Friday, August 22, 2008

Defcon, testing and exploiting

This year at Defcon Immunity trotted out the first iteration of their NOP cert test, and I had the pleasure of giving it a test run. I still think it's a great indicator of ability, despite the Immunity tools focus; I'm not a user of any of their tools generally, but I managed to pull off the hardest level test in a modest time. It got us thinking on the way home, where does one go from the bar set by the NOP to get to the next level in terms of exploit development skill? In this vein I've thrown together a few windows executables, and in a nod to Gera of Core, they're called Advanced Windows Buffer Overflows (AWBOs).

We've set up a few ground rules and a basic set up to keep things moving along:

1) All exploits are performed in Windows 2000 SP4 unless otherwise specified. Sometimes, otherwise will be specified.
2) Exploits will use the provided shellcode, or ret2lib.
3) You may not return to hard coded stack addresses.
4) No source code will be provided - just like the NOP cert.

Standard tools used are cygwin with perl, and windbg, installation in vmware a plus. The shellcode provided is the amazing windows exec shellcode from metasploit set up to run calc.exe.

I can say that all of these are exploitable, and they run through a progression, so try to do each of them in the most straight forward way possible. We'll be skipping awbo1.exe as it's very similar to one of immunity's tests (as far as my memory serves). They'll be released slowly over the next few months. Feel free to send in your solutions, or ask for tips. All of the examples have been play tested by the VRT analysts team, and are assured to be exploitable.

"This next test could take a very, very long time. If you become lightheaded from thirst, feel free to pass out. An intubation associate will be dispatched to revive you with peptic salve and adrenaline."

Awbo2.exe download and shellcode download

AUTHOR: Lurene Grenier, Analyst Team Lead, Sourcefire Vulnerability Resarch Team

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