Uninformed: Informative Information for the Uninformed

Vol 6» 2007.Jan

Engineering in Reverse
Subverting PatchGuard Version 2
Windows Vista x64 and recently hotfixed versions of the Windows Server 2003 x64 kernel contain an updated version of Microsoft's kernel-mode patch prevention technology known as PatchGuard. This new version of PatchGuard improves on the previous version in several ways, primarily dealing with attempts to increase the difficulty of bypassing PatchGuard from the perspective of an independent software vendor (ISV) deploying a driver that patches the kernel. The feature-set of PatchGuard version 2 is otherwise quite similar to PatchGuard version 1; the SSDT, IDT/GDT, various MSRs, and several kernel global function pointer variables (as well as kernel code) are guarded against unauthorized modification. This paper proposes several methods that can be used to bypass PatchGuard version 2 completely. Potential solutions to these bypass techniques are also suggested. Additionally, this paper describes a mechanism by which PatchGuard version 2 can be subverted to run custom code in place of PatchGuard's system integrity checking code, all while leaving no traces of any kernel patching or custom kernel drivers loaded in the system after PatchGuard has been subverted. This is particularly interesting from the perspective of using PatchGuard's defenses to hide kernel mode code, a goal that is (in many respects) completely contrary to what PatchGuard is designed to do.

Locreate: An Anagram for Relocate
This paper presents a proof of concept executable packer that does not use any custom code to unpack binaries at execution time. This is different from typical packers which generally rely on packed executables containing code that is used to perform the inverse of the packing operation at runtime. Instead of depending on custom code, the technique described in this paper uses documented behavior of the dynamic loader as a mechanism for performing the unpacking operation. This difference can make binaries packed using this technique more difficult to signature and analyze, but only when presented to an untrained eye. The description of this technique is meant to be an example of a fun thought exercise and not as some sort of revolutionary packer. In fact, it's been used in the virus world many years prior to this paper.

Exploitation Technology
Exploiting 802.11 Wireless Driver Vulnerabilities on Windows
Johnny Cache, H D Moore, skape
This paper describes the process of identifying and exploiting 802.11 wireless device driver vulnerabilities on Windows. This process is described in terms of two steps: pre-exploitation and exploitation. The pre-exploitation step provides a basic introduction to the 802.11 protocol along with a description of the tools and libraries the authors used to create a basic 802.11 protocol fuzzer. The exploitation step describes the common elements of an 802.11 wireless device driver exploit. These elements include things like the underlying payload architecture that is used when executing arbitrary code in kernel-mode on Windows, how this payload architecture has been integrated into the 3.0 version of the Metasploit Framework, and the interface that the Metasploit Framework exposes to make developing 802.11 wireless device driver exploits easy. Finally, three separate real world wireless device driver vulnerabilities are used as case studies to illustrate the application of this process. It is hoped that the description and illustration of this process can be used to show that kernel-mode vulnerabilities can be just as dangerous and just as easy to exploit as user-mode vulnerabilities. In so doing, awareness of the need for more robust kernel-mode exploit prevention technology can be raised.