VBootkit Bypasses Vista’s Digital Code Signing

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At Black Hat Europe (in Amsterdam) security experts from India (Nitin and Vipin Kumar of NV labs) demonstrated a special boot loader that gets around Vista’s code-signing mechanisms. Known as VBoot and launching from a CD and booting Vista it can make on-the-fly changes in memory and in files being read.

In a demonstration, the “boot kit” managed to run with kernel privileges and issue system rights to a CMD shell when running on Vista RC2 (build 5744), even without a Microsoft signature

Experts say that the fundamental problem that this highlights is that every stage in Vista’s booting process works on blind faith that everything prior to it ran cleanly. The boot kit is therefore able to copy itself into the memory image even before Vista has booted and capture interrupt 13, which operating systems use for read access to sectors of hard drives, among other things.

As soon as the NT Boot sector loads Bootmgr.exe, VBootkit patches the security queries that ensure integrity and copies itself into an unused area of memory. Something similar is done with the subsequent boot stages of Winload.exe and NTOSKrnl.exe so that the boot kit is running in the background when the system is finally booted; at no time are Vista’s new security mechanisms, which were intended to prevent unsigned code from being executed with kernel privileges, set off.

Interesting eh, seen as though Microsoft touts Vista as so secure…and it’s already been taken apart.

It might lead to some interesting workarounds for DRM and video content protection.

From the Black Hat release:

Vboot kit is first of its kind technology to demonstrate Windows vista kernel subversion using custom boot sector. Vboot Kit shows how custom boot sector code can be used to circumvent the whole protection and security mechanisms of Windows Vista. The booting process of windows Vista is substantially different from the earlier versions of Windows. The talk will give you:

• details and know abouts for the Vista booting process.
• explain the vboot kit functionality and how it works.
• insight into the Windows Vista Kernel.

We will also review sample Ring 0 Shell code (for Vista). The sample shellcode effectively raises the privileges of certain programs to SYSTEM. A live demonstration of vboot kit POC will be done.

Source: Heise Security