« Posts under assembly

PCAUSA Rawether for Windows local privilege escalation

Rawether for Windows is a framework that facilitates communication between an application and the NDIS miniport driver. It’s produced by a company named Printing Communications Assoc., Inc. (PCAUSA), which seems to be no longer operating. Company websites can be still reached through web.archive.org:


Rawether framework provides NDIS Protocol Driver similar to the NPF.SYS (part of the WinPcap). This framework is used by many different hardware vendors in their WiFi and router control applications. Exploit attached to this advisory targets 64bit version of PcaSp60.sys driver which is part of ASUS PCE-AC56 WLAN Card Utilities.

Identifying other affected vendors is quite problematic, since Rawether is just a framework it is possible that the driver name, device name or driver version info were changed. Additionally, verifying if the particular software is really vulnerable is sometimes not feasible, because installation package won’t install without specific hardware.

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IceCTF 2016 Slickserver/Slickerserver pwn writeup

It’s almost 6 months since the last post, so to keep some good yearly average it’s finally time to write something here. For the last couple of months, most of my spare time went into various CTF challenges. Since I’m very new to CTFs, usually I’m not able to solve top scoring tasks and people familiar with CTFs probably know that challenges with lower score are not really interesting enough to write anything more than a few lines writeup (and there is usually dozens of writeups already published, before I even think about writing something). So this time it might be a bit different since the IceCTF was 2 weeks long, and I could prepare some good writeup before competition ends. I did two pwn tasks, which are actually very similar to each other. First one was initially for 300 points, but the organizers figured out, that it’s easier than they thought, so they lowered score to 140pts and published improved version of the task for 300pts. Description for both tasks was pretty straight forward »Read More

wow64ext finally compatible with Windows 8

I’ve some good news for everyone who was complaining that wow64ext library doesn’t work on Windows 8. I’ve researched this topic a bit, and I’ve released fixed version of the library. Problem was very simple, but it couldn’t be fixed with just one line of code. On Windows 8/8.1 x64 version of NTDLL is loaded at address above 4GB, it wasn’t the case on previous versions of Windows, as x64 NTDLL was always loaded below 4GB. Also some of the system structures are mapped above 4GB (PEB_LDR_DATA64). To fix all the issues I had to introduce new memcpy-like function that can copy data from addresses above 4GB to addresses that are accessible by the standard x86 code. I’ve also fixed problem with case-sensitive GetModuleHandle64 that popped up recently. Below you can find direct link to the updated library:

Link to library hosted on google code: http://code.google.com/p/rewolf-wow64ext/
Direct link to zip package: http://rewolf-wow64ext.googlecode.com/files/rewolf.wow64ext.v1.0.0.3.zip

Debugging ring 3 part of PE/PE+ loader

Someone may ask what is the purpose of debugging PE loader, here are a few reasons:

  • checking why executable is not loaded properly (imports, TLS, other initialization related issues)
  • looking for some hidden features (e.g. LdrpCheckNXCompatibility)
  • plain curiosity

Of course debugging ring 3 part of PE/PE+ loader can reveal only part of the truth, for the second part (or rather first part if I want to be strict) there is MiCreateImageFileMap function inside ntoskrnl (source code of this function can be found in Windows Research Kernel: \base\ntos\mm\creasect.c, it is a bit old, but most of the stuff hasn’t changed much). In this short article I’ll cover only x86 and x64 of ring 3 part.

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Solving gim913’s KeygenMe#01

Due to permanent lack of time and really long personal TODO list I’m not frequent crackme-solver, but sometimes it is good to check if my skills didn’t get rusty. I’ve browsed through unsolved crackmes on crackmes.de and found quite new gim913’s crackme that was unsolved for almost 2 months (yup, I know that it’s not much :) ). Knowing reputation of the author I’ve decided to give it a try, as probably there will be something interesting inside. So, let’s start.

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rep movsb isn’t memcpy()

Some of you probably noticed that HexRays translates rep movsb opcode to memcpy() function from standard C library. In most cases this is perfectly correct behaviour, but there is at least one example when it will not work as it should.
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MD5 implementation for GNU Assembler

Probably some of you may remember that over 6 years ago I’ve created MD5 implementation for MASM (there was also separate file for FASM adapted by Reverend). Few days ago I’ve received e-mail from Hannes Beinert, he found my old code and he adapted it for GNU Assembler. Moreover he also wrote comments for almost every line of algorithm, so it can be now used for some educational purposes. I’ve decided to put it all together online on code.google.com, so everyone can benefit from it:


You can also download it as a separate zip archive: