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I am sitting here, working with my PC: My keyboard and my mouse are connected wirelessly via Bluetooth and my monitor is hooked up through DVI. The graphics card is sitting in a PCI slot, main memory is DDR-SDRAM, and my optical drive can do CDs and DVDs. While my internal hard disk speaks the SATA protocol, my home directory is actually sitting on an SD card that is connected through a USB reader. My internet connection is done through DSL. On the software side, I am using GNU/Linux and browsing the internet with Firefox. No way I would ever watch a video in H.264 format.

I just did a Lightning Talk at the 26th Chaos Communication Congress 26C3 about our new project “libcpu”, and it has already been picked up by Golem.de and reddit.com, so I might as well announce it here:

“libcpu” is an open source library that emulates several CPU architectures, allowing itself to be used as the CPU core for different kinds of emulator projects. It uses its own frontends for the different CPU types, and uses LLVM for the backend. libcpu is supposed to be able to do user mode and system emulation, and dynamic as well as static recompilation.

Here are my slides: 26C3-libcpu.pdf

Here is the video recording: 26C3-libcpu.mp4

Read more at http://www.libcpu.org/

Users of Skype that run 64-bit versions of Windows like me probably have noticed that when starting Skype, the following dialog box appears:

The program or feature “\??\C:\Documents and Settings\Myria\Local Settings\Temp\12\1.com” cannot start or run due to incompatibility with 64-bit versions of Windows. Please contact the software vendor to ask if a 64-bit Windows compatible version is available.

Well, that’s weird. Skype’s trying to run a .com file, which won’t work on Win64 because there’s no NTVDM. Let’s try opening it in Hex Workshop. Access denied? OK, I’ll terminate Skype to read it. Still can’t?! This thing is really starting to annoy me. I’ll use WinDbg to terminate winlogon.exe to force a kernel panic. I reboot and NOW I can read the damn file.

An unreadable executable file coming from Skype sounds interesting, so I look at it. It’s 46 bytes long. For copyright reasons I can’t post the file or a complete disassembly. However, I can describe the program in terms of 16-bit DOS C:

int main(void)
{
fwrite((const void far*) 0xF0000000, 1, 0xFFFF, stdout);
fwrite((const void far*) 0xF000FFFF, 1, 1, stdout);
return 0;
}

It’s dumping your system BIOS, which usually includes your motherboard’s serial number, and pipes it to the Skype application. I have no idea what they’re using it for, or whether they send anything to their servers, but I bet whatever they’re doing is no good given their track record.

In 32-bit Windows NT, including Vista, the kernel permits NTVDM to make a read-only mapping of the BIOS at address 000F0000. This allows DOS programs running under NTVDM to make use of the BIOS. That’s how this 46-byte program is capable of sending the BIOS to the Skype application, and also explains why they use this mechanism to begin with.

If they hadn’t been ignorant of Win64’s lack of NTVDM, nobody would’ve noticed this happening.