Flare-On Challenge 7 - 03 - Wednesday

tags: ctf challenge write-up binary reverse engineer Malware Analysis
by Firpo7

Be the wednesday. Unlike challenge 1, you probably won’t be able to beat this game the old fashioned way. Read the README.txt file, it is very important.

This challenge consists of a simple game. This game is similar to “Dino Runner”, where the character will run forward and you have to avoid obstacles by jumping them or slipping below.

Game Screenshot

After a few runs, it’s noticeable that the jumps and the slipping are always the same. So they could either generated in a deterministic way or they are hardcoded.

After searching around in the code how the obstacles were generated I found in the executable what they seem to be the bytes that determine how the obstacles should be avoided.

They are an array of zeroes and ones, where zeroes mean that the obstacle should be avoided by passing below while the ones mean that the obstacle should be jumped.

Hex View of Obstacles

The flag could be found by treating those bytes as bits and converting them into characters.