Challenge name : Flappy ship
Description :
Have fun
and share your fun! :-)
Controls: up, down, right, left
Download link (20MB)
Actualy i didn’t solve this cahallenge at the ctf runing time but after 3 monthes i do it adn solve, It turned out to be easy to solve, but I was making it more complicated than it is
Solution :
After downloading the challenge files, you can tell that you have to hack the game score to get the flag and when you say game hacking Cheat Engine comes to your mind.
P.S : during ctf time i wasted more than hour just playing the game.
First step is to know what score we have to reach to get the flag so after doing simple strings extraction we can notice interesting string (“Score 0xab56”)
we need to make your score = 0xab56 (43862 in dec) but when you make it equal to this number nothing happens
actually this made me give up on trying solve the challenge during ctf running time but now i can see what was wrong
simply when you cahnge the value using cheat engine it will not change until you hit an asteroid by your rocket so after we hit the asteroid it will be 43862 + 1 = 43863 and this will not show you the flag
we should make it 43861 and hit astroid to get a score = 43861 + 1 = 43862 and this will give us the flag
sadly this will give us half of the flag (when you hacke the score you will get a printed message “flag{you_got_ban”)
to get the second half we have to hack the lives counter now (a hint from the author of the challenge )
but we have no clue what the value should be to give us the rest of the flag
we can do a little trick with cheat engine
we can search for the lives address then find what access to it
the instruction at 0040442A seems interesting, when we inspect it by clicking more information button
cmp [rcx+10],000056AB
it compares the lives number with the value (0x56ab in dec 22187)
and again when we change it we have to change the value to 22188 so when the asteroid hits our ship 22188 -1 = 22187 and this will print the second half of flag
Useful resources :
Cheat engine tutorial guide
Introduction to Game Hacking!