[CSAW 2016] Gametime Writeup

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Guess what time it is! That’s right! Gametime! Wowwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww!!!!!!!!!!!!

Author: Brad Antoniewicz

note: flag is not in flag{} format

gametime.exe

To be honest, I downloaded the file, played the game once and got the key. It is possible for humans to win the game, or maybe it’s just my Super-Vegan powers LOL.
But I wanted, of course, to get the key using RE. I opened IDA and searched for interesting strings.

I highlighted the important lines: The success message (I know, I got it when I played) and the failure messages. Using X-Refs I found where the failure messages are printed out and patched the program to jump to the success instead. Notice that you’ll need to change two functions.

1st jump to change:

gametime_1

2nd jump to change:

gametime_2

Now apply the patches to the program and run it. Let the game play alone and the key will be printed.

The key is: (no5c30416d6cf52638460377995c6a8cf5)

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