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Noz3001
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PostPosted: Wed Sep 17, 2008 3:37 pm    Post subject: "The Game" Reply with quote

The aim of this "crackme" is simple, there's a value which is randomized everytime you press enter. Your goal is to set this value to 5000 to win. This means that patching jumps to make it say you've won don't count but you can do that if you really cant figure out how to set the value.

I was inspired by this thread: http://forum.cheatengine.org/viewtopic.php?t=289549 so you might want to check it out.

What i'm really looking for is information and tips which will help me make the program even more secure.

Try it out =D.


Last edited by Noz3001 on Thu Sep 18, 2008 2:07 pm; edited 2 times in total
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AndrewMan
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PostPosted: Wed Sep 17, 2008 6:22 pm    Post subject: Reply with quote

I dont get it.

I pressed enter, it randomizes a number, than what do I do?

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Noz3001
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PostPosted: Thu Sep 18, 2008 2:02 am    Post subject: Reply with quote

AndrewMan wrote:
I dont get it.

I pressed enter, it randomizes a number, than what do I do?


You're supposed to set it to 5000.
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DoomsDay
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PostPosted: Thu Sep 18, 2008 3:47 am    Post subject: Reply with quote

This crackme is well written...
It took me an hour or so to reach the decryption proc manually(I began by setting a breakpoint on WriteFile), but then I just had to monitor it.
The first call to it will check if the value is already 5000, else a random number will be generated, and then checked to zero out. If it won't - it will be encrypted by the function that follows the decryption routine (location-wise).

I won't reveal my solution this time, enjoy yourselves Wink

EDIT: Security tips:
  • Don't use the same stack location twice - it's a high-risk security flaw
  • Use exception handlers to trigger some events - cause an exception in purpose to jump out of a code block (it could be a bitch to analyze)


Last edited by DoomsDay on Thu Sep 18, 2008 5:15 am; edited 2 times in total
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Noz3001
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PostPosted: Thu Sep 18, 2008 3:52 am    Post subject: Reply with quote

Very Happy Nice one DoomsDay, you're the first person to beat it. Oohh, can't wait until i've finished the next version =].
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SunBeam
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PostPosted: Thu Sep 18, 2008 5:00 am    Post subject: Reply with quote

Should I even bother? Smile
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DoomsDay
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PostPosted: Thu Sep 18, 2008 5:08 am    Post subject: Reply with quote

If noz is going to release an enhanced version, I'd say yes Very Happy
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Zand
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PostPosted: Thu Sep 18, 2008 5:19 am    Post subject: Reply with quote

40245A = mov eax, 0x1388
401ff8 = NOP
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SunBeam
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PostPosted: Thu Sep 18, 2008 5:31 am    Post subject: Reply with quote

^ No patching, bithc Very Happy
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Zand
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PostPosted: Thu Sep 18, 2008 5:46 am    Post subject: Reply with quote

I didn't patch no jumps....
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DoomsDay
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PostPosted: Thu Sep 18, 2008 5:54 am    Post subject: Reply with quote

You didn't patch the correct addresses either... Smile
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Zand
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PostPosted: Thu Sep 18, 2008 5:58 am    Post subject: Reply with quote

I did.
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Noz3001
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PostPosted: Thu Sep 18, 2008 2:07 pm    Post subject: Reply with quote

Slightly updated version uploaded. Have a go =].
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Cryoma
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PostPosted: Thu Sep 18, 2008 2:18 pm    Post subject: Reply with quote

Done.
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Noz3001
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PostPosted: Thu Sep 18, 2008 3:02 pm    Post subject: Reply with quote

Cryoma wrote:
Done.


Any more info?
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