0ctf 2016 writeup for VM challenge(reverse 7 pts)

Categories CTF

This is a write-up for the 0ctf 2016 quals “VM” reverse challenge worth 7 points.

The main process of solving this challenge contains 3 phase:

  1. Find the location of input check algorithm
  2. Reverse input transform algorithm
  3. profit

I wasted much life in the second phase. This function is flattend by a big switch structure and contains a lot of goto instruction. It’s hard to reverse such a function statically, So we use dynamic analysis and black box analysis. we make a few assumptions on the transform pattern. We can reverse the algorithm without understanding  assembly or decompiled code.

Continue reading “0ctf 2016 writeup for VM challenge(reverse 7 pts)”

Teaser CTF 2015 writeup(So easy, power level)

Categories Uncategorized

Teaser CTF is launched by Dragon Sector, is a Polish security Capture The Flag team. It was created in February 2013 and currently has 13 active members.

I solved two challenge in the first evening(so easy, power level) and tried to solves the pwnable challenge quine on Sunday Morning but failed, I found a write-any-where vulnerability but I didn’t see how to exploit. Continue reading “Teaser CTF 2015 writeup(So easy, power level)”