CSAW CTF - Forensics Write-up

The forensics challenge given at CSAW CTF weren't exactly what I was expecting, but still we achieved to solve most of it. Here are my write-ups for the 4 challenges.

Challenges were made by Efstratios Gavas (@xtrat), Director of cyber security labs at NYU Poly! Awesome :)

CSAW Exploit 3 Write-up - FreeBSD local root

For exploit3, we were given the following instructions:

Get Root. Get the key. If only I can jump over the mountain without being normal
ssh://128.238.66.100:40010
chal3:$+1zX*(
2048 51:41:94:32:cf:b1:3f:d9:74:c1:d2:08:aa:e3:49:2b /etc/ssh/ssh_host_rsa_key.pub (RSA)
1024 22:7f:72:93:93:7e:9a:3d:01:b9:58:ea:74:1a:c5:af /etc/ssh/ssh_host_dsa_key.pub (DSA)

Vulnerable FreeBSD kernel

We ssh and notice an old FreeBSD kernel. We can try to use @kingcope's freebsd sendfile cache local root. Sadly it does not work out of the box because we do not have /tmp writable: we have to customize a bit the shellcode to use a different one. Also, we can remove the 64-bit part since we are on 32-bit.

CSAW Exploit 1 Write-up - FreeBSD remote stack based buffer overflow

A few weeks ago was held Leet More CTF where Nibbles ended 1st! Didn't have the time to put some write-ups, but you can find some on nibbles blog or by sh4ka, auntitled and hellman.

Last week-end was held the well-known CSAW CTF (quals) by NYU-Poly. Last year and this year winners are none but our awesome friends PPP! We took 2nd place just behind them, see top15 graph.

They gave us interesting exploit challenges and I had the opportunity to look at exploit1: a remote stack based buffer overflow under FreeBSD 8.0.