bl4ack's Confusion

Author:
bl4ack

Language:
C/C++

Upload:
2021-12-17 01:56

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Platform:
Windows

Difficulty:
3.0

Quality:
3.5

Arch:
x86-64

Downloads:
11

Size:
25.00 KB

Writeups:
2

Comments:
4

Description

Hi there, the rules is on crackme. is not difficult bypass the anti-debugger but find the key, you'll have to use your neurons...

Comments (4)
Writeups (2)

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mucomplex on 2022-01-09 17:54: Password input is bugged. It is not replace inside memory

mstik13 on 2022-05-19 08:05: NiceOne!, that was fun!

db123 on 2022-06-22 07:37: char v15m[16] = { 0x4E, 0, 0x69, 0, 0x63, 0 , 0x65, 0, 0x4F, 0, 0x6E, 0, 0x65, 0, 0x21, 0 }; memcpy(&v15, v15m, sizeof(v15)); char v16m[16] = { 0x2D, 0, 0x5F, 0, 0, 0 , 0, 0, 0x80, 0x50, 0x5D, 0x61, 0xF8, 0x7F, 0, 0 }; memcpy(&v16, v16m, sizeof(v16)); memset(&si128, 0, sizeof(si128)); si128.m128i_i8[0] = (uint8)strlen(username); si128.m128i_u8[8] = 0x0F; userpassword[0] = (si128.m128i_i32[0] ^ *(unsigned __int16*)&v15); userpassword[1] = (si128.m128i_i32[0] ^ WORD1(v15)); userpassword[2] = (si128.m128i_i32[0] ^ WORD2(v15)); userpassword[3] = (si128.m128i_i32[0] ^ WORD3(v15)); userpassword[4] = (si128.m128i_i32[0] ^ WORD4(v15)); userpassword[5] = (si128.m128i_i32[0] ^ WORD5(v15)); userpassword[6] = (si128.m128i_i32[0] ^ WORD6(v15)); userpassword[7] = (si128.m128i_i32[0] ^ HIWORD(v15)); userpassword[8] = (si128.m128i_i32[0] ^ v16.m128i_u16[0]); userpassword[9] = (si128.m128i_i32[0] ^ v16.m128i_u16[1]); userpassword[10] = (si128.m128i_i32[0] ^ v16.m128i_u16[2]); userpassword[11] = 0;

Tomutt on 2025-08-17 12:27: I can't find the part where the username length is assigned to the key calculation logic. Like, "local_38 != (uStack_84 & 0xffff ^ local_50)" the local_50 here, which is supposed to hold username length value. There's no other initialization for that. Thus it's always 0. Can somebody explain this to me?

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Solution by dev0 on 2022-01-26 13:36:
Thank you bl4ack!

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Solution by mstik13 on 2022-05-19 08:48:
Thanks for this it was a NiceOne! Tools Used: Ghidra, x64dbg

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crackmes.one

bl4ack's Confusion