Created
December 30, 2023 18:08
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Easy Risky solution - ASIS CTF 2023
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#include <stdint.h> | |
#include <stdio.h> | |
void encryptData(uint8_t *flag_enc) { | |
uint8_t bVar1; | |
int64_t lVar2; | |
uint64_t *puVar3; | |
uint64_t uVar4; | |
uint8_t *pbVar5; | |
uint64_t uVar6; | |
uint64_t uVar7; | |
if (flag_enc[0x2a] != 0) { | |
return; | |
} | |
uVar6 = -(long)flag_enc; | |
uVar7 = uVar6 & 7; | |
if (uVar7 == 0) { | |
uVar4 = (uint64_t)flag_enc[0x2b]; | |
lVar2 = 0x2a; | |
pbVar5 = flag_enc; | |
} | |
else { | |
bVar1 = flag_enc[0x2b]; | |
uVar4 = (uint64_t)bVar1; | |
*flag_enc = *flag_enc ^ bVar1; | |
if ((uVar6 & 6) == 0) { | |
lVar2 = 0x29; | |
pbVar5 = flag_enc + 1; | |
} | |
else { | |
lVar2 = 0x28; | |
flag_enc[1] = flag_enc[1] ^ bVar1; | |
pbVar5 = flag_enc + 2; | |
if (2 < uVar7) { | |
lVar2 = 0x27; | |
flag_enc[2] = flag_enc[2] ^ bVar1; | |
pbVar5 = flag_enc + 3; | |
if ((uVar6 & 4) != 0) { | |
flag_enc[3] = flag_enc[3] ^ bVar1; | |
if (uVar7 < 5) { | |
lVar2 = 0x26; | |
pbVar5 = flag_enc + 4; | |
} | |
else { | |
flag_enc[4] = flag_enc[4] ^ bVar1; | |
if (uVar7 == 5) { | |
lVar2 = 0x25; | |
pbVar5 = flag_enc + 5; | |
} | |
else { | |
flag_enc[5] = flag_enc[5] ^ bVar1; | |
lVar2 = 0x24; | |
pbVar5 = flag_enc + 6; | |
if (((uint64_t)(flag_enc + -1) & 7) == 0) { | |
lVar2 = 0x23; | |
flag_enc[6] = flag_enc[6] ^ bVar1; | |
pbVar5 = flag_enc + 7; | |
} | |
} | |
} | |
} | |
} | |
} | |
} | |
puVar3 = (uint64_t *)(flag_enc + uVar7); | |
uVar6 = uVar4 << 8 | uVar4 | uVar4 << 0x10 | uVar4 << 0x18 | uVar4 << 0x20 | uVar4 << 0x28 | | |
uVar4 << 0x30 | uVar4 << 0x38; | |
puVar3[3] = uVar6 ^ puVar3[3]; | |
*puVar3 = uVar6 ^ *puVar3; | |
puVar3[1] = uVar6 ^ puVar3[1]; | |
puVar3[2] = uVar6 ^ puVar3[2]; | |
if (0x2a - uVar7 >> 3 == 5) { | |
pbVar5 = pbVar5 + 0x28; | |
puVar3[4] = uVar6 ^ puVar3[4]; | |
lVar2 = lVar2 + -0x28; | |
if (0x2a - uVar7 == 0x28) goto LAB_00100c04; | |
} | |
else { | |
pbVar5 = pbVar5 + 0x20; | |
lVar2 = lVar2 + -0x20; | |
} | |
*pbVar5 = *pbVar5 ^ flag_enc[0x2b]; | |
if ((((lVar2 != 1) && (pbVar5[1] = pbVar5[1] ^ flag_enc[0x2b], lVar2 != 2)) && | |
(pbVar5[2] = pbVar5[2] ^ flag_enc[0x2b], lVar2 != 3)) && | |
(((pbVar5[3] = pbVar5[3] ^ flag_enc[0x2b], lVar2 != 4 && | |
(pbVar5[4] = pbVar5[4] ^ flag_enc[0x2b], lVar2 != 5)) && | |
(pbVar5[5] = pbVar5[5] ^ flag_enc[0x2b], lVar2 != 6)))) { | |
pbVar5[6] = pbVar5[6] ^ flag_enc[0x2b]; | |
} | |
LAB_00100c04: | |
flag_enc[0x2a] = 1; | |
return; | |
} | |
void main() { | |
char enc_flag[] = { 0x6b,0x79,0x63,0x79,0x51,0x1d,0x58,0x73,0x75,0x5e,0x65,0x75,0x58,0x7f,0x44,0x75,0x67,0x19,0x75,0x45,0x64,0x75,0x78,0x63,0x79,0x69,0x07,0x7c,0x1c,0x1e,0x75,0x47,0x1e,0x49,0x62,0x0b,0x44,0x6f,0x0b,0x0b,0x57,0x2a,0x00,0x2a}; | |
encryptData(enc_flag); | |
puts(enc_flag); | |
} |
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