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o_O - [v0.1] Crackme

 
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zeroc0de
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PostPosted: Fri Oct 10, 2008 11:53 am    Post subject: o_O - [v0.1] Crackme Reply with quote

Goal is to figure a way to patch the password check, then figure the real password.

Coded in Delphi, this should be a good, fun and worth challenge.

Have a go, sir Smile

-- Patching the password check is easy.
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Noz3001
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PostPosted: Fri Oct 10, 2008 2:29 pm    Post subject: Reply with quote

Password: cookie

For any password:
004598BF EB 34 JMP SHORT o_O.004598F5
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zeroc0de
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PostPosted: Fri Oct 10, 2008 3:04 pm    Post subject: Reply with quote

Fucking nice! Can you explain a little how you did find the password?
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Zerith
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Joined: 07 Oct 2007
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PostPosted: Sat Oct 11, 2008 12:13 am    Post subject: Reply with quote

You apparently had a switch() for every char entered:

Code:

004599A8  |. 83C0 9D        |ADD EAX,-63                             ;  Switch (cases 63..6F)
004599AB  |. 83F8 0C        |CMP EAX,0C
004599AE  |. 77 6F          |JA SHORT o_O.00459A1F
004599B0  |. 0FB680 BE99450>|MOVZX EAX,BYTE PTR DS:[EAX+4599BE]
004599B7  |. FF2485 CB99450>|JMP DWORD PTR DS:[EAX*4+4599CB]
004599BE  |. 01             |DB 01                                   ;  Index table to switch 004599CB







Code:

004599E3  |> 8BC6           |MOV EAX,ESI                             ;  ; Case 63 ('c') of switch 004599A8
004599E5  |. F7EF           |IMUL EDI
004599E7  |. 0105 D0054600  |ADD DWORD PTR DS:[4605D0],EAX
004599ED  |. EB 37          |JMP SHORT o_O.00459A26
004599EF  |> 8BC6           |MOV EAX,ESI                             ;  Case 6F ('o') of switch 004599A8
004599F1  |. F7EF           |IMUL EDI
004599F3  |. 0105 D0054600  |ADD DWORD PTR DS:[4605D0],EAX
004599F9  |. EB 2B          |JMP SHORT o_O.00459A26
004599FB  |> 8BC6           |MOV EAX,ESI                             ;  Case 6B ('k') of switch 004599A8
004599FD  |. F7EF           |IMUL EDI
004599FF  |. 0105 D0054600  |ADD DWORD PTR DS:[4605D0],EAX
00459A05  |. EB 1F          |JMP SHORT o_O.00459A26
00459A07  |> 8BC6           |MOV EAX,ESI                             ;  Case 69 ('i') of switch 004599A8
00459A09  |. F7EF           |IMUL EDI
00459A0B  |. 0105 D0054600  |ADD DWORD PTR DS:[4605D0],EAX
00459A11  |. EB 13          |JMP SHORT o_O.00459A26
00459A13  |> 8BC6           |MOV EAX,ESI                             ;  Case 65 ('e') of switch 004599A8
00459A15  |. F7EF           |IMUL EDI
00459A17  |. 0105 D0054600  |ADD DWORD PTR DS:[4605D0],EAX
00459A1D  |. EB 07          |JMP SHORT o_O.00459A26
00459A1F  |> 33C0           |XOR EAX,EAX                             ;  Default case of switch 004599A8
00459A21  |. A3 D0054600    |MOV DWORD PTR DS:[4605D0],EAX
00459A26  |> 47             |INC EDI
00459A27  |. FF4D F4        |DEC DWORD PTR SS:[EBP-C]
00459A2A  |.^0F85 2EFFFFFF  \JNZ o_O.0045995E



Then it was pretty easy tracing and finding the right password Wink
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zeroc0de
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PostPosted: Sun Oct 12, 2008 3:03 pm    Post subject: Reply with quote

Thanks, I'll look deeper into it.
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