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[GWCTF 2019]babyvm re

BABYVM

基于虚拟机操作的一个题 明面上的check函数和加密逻辑都是假的

image-20220115141537269

操作码

重点分析这个vm

0xF5, 0xF1, 0xE1, 0x00, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 
  0x20, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x01, 0x00, 0x00, 0x00, 
  0xF2, 0xF1, 0xE4, 0x21, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x02, 
  0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x22, 0x00, 0x00, 0x00, 
  0xF1, 0xE1, 0x03, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x23, 
  0x00, 0x00, 0x00, 0xF1, 0xE1, 0x04, 0x00, 0x00, 0x00, 0xF2, 
  0xF1, 0xE4, 0x24, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x05, 0x00, 
  0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x25, 0x00, 0x00, 0x00, 0xF1, 
  0xE1, 0x06, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x26, 0x00, 
  0x00, 0x00, 0xF1, 0xE1, 0x07, 0x00, 0x00, 0x00, 0xF2, 0xF1, 
  0xE4, 0x27, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x08, 0x00, 0x00, 
  0x00, 0xF2, 0xF1, 0xE4, 0x28, 0x00, 0x00, 0x00, 0xF1, 0xE1, 
  0x09, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x29, 0x00, 0x00, 
  0x00, 0xF1, 0xE1, 0x0A, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 
  0x2A, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x0B, 0x00, 0x00, 0x00, 
  0xF2, 0xF1, 0xE4, 0x2B, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x0C, 
  0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x2C, 0x00, 0x00, 0x00, 
  0xF1, 0xE1, 0x0D, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x2D, 
  0x00, 0x00, 0x00, 0xF1, 0xE1, 0x0E, 0x00, 0x00, 0x00, 0xF2, 
  0xF1, 0xE4, 0x2E, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x0F, 0x00, 
  0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x2F, 0x00, 0x00, 0x00, 0xF1, 
  0xE1, 0x10, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x30, 0x00, 
  0x00, 0x00, 0xF1, 0xE1, 0x11, 0x00, 0x00, 0x00, 0xF2, 0xF1, 
  0xE4, 0x31, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x12, 0x00, 0x00, 
  0x00, 0xF2, 0xF1, 0xE4, 0x32, 0x00, 0x00, 0x00, 0xF1, 0xE1, 
  0x13, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x33, 0x00, 0x00, 
  0x00, 0xF4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xF5, 0xF1, 
  0xE1, 0x00, 0x00, 0x00, 0x00, 0xF1, 0xE2, 0x01, 0x00, 0x00, 
  0x00, 0xF2, 0xF1, 0xE4, 0x00, 0x00, 0x00, 0x00, 0xF1, 0xE1, 
  0x01, 0x00, 0x00, 0x00, 0xF1, 0xE2, 0x02, 0x00, 0x00, 0x00, 
  0xF2, 0xF1, 0xE4, 0x01, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x02, 
  0x00, 0x00, 0x00, 0xF1, 0xE2, 0x03, 0x00, 0x00, 0x00, 0xF2, 
  0xF1, 0xE4, 0x02, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x03, 0x00, 
  0x00, 0x00, 0xF1, 0xE2, 0x04, 0x00, 0x00, 0x00, 0xF2, 0xF1, 
  0xE4, 0x03, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x04, 0x00, 0x00, 
  0x00, 0xF1, 0xE2, 0x05, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 
  0x04, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x05, 0x00, 0x00, 0x00, 
  0xF1, 0xE2, 0x06, 0x00, 0x00, 0x00, 0xF2, 0xF1, 0xE4, 0x05, 
  0x00, 0x00, 0x00, 0xF1, 0xE1, 0x06, 0x00, 0x00, 0x00, 0xF1, 
  0xE2, 0x07, 0x00, 0x00, 0x00, 0xF1, 0xE3, 0x08, 0x00, 0x00, 
  0x00, 0xF1, 0xE5, 0x0C, 0x00, 0x00, 0x00, 0xF6, 0xF7, 0xF1, 
  0xE4, 0x06, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x07, 0x00, 0x00, 
  0x00, 0xF1, 0xE2, 0x08, 0x00, 0x00, 0x00, 0xF1, 0xE3, 0x09, 
  0x00, 0x00, 0x00, 0xF1, 0xE5, 0x0C, 0x00, 0x00, 0x00, 0xF6, 
  0xF7, 0xF1, 0xE4, 0x07, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x08, 
  0x00, 0x00, 0x00, 0xF1, 0xE2, 0x09, 0x00, 0x00, 0x00, 0xF1, 
  0xE3, 0x0A, 0x00, 0x00, 0x00, 0xF1, 0xE5, 0x0C, 0x00, 0x00, 
  0x00, 0xF6, 0xF7, 0xF1, 0xE4, 0x08, 0x00, 0x00, 0x00, 0xF1, 
  0xE1, 0x0D, 0x00, 0x00, 0x00, 0xF1, 0xE2, 0x13, 0x00, 0x00, 
  0x00, 0xF8, 0xF1, 0xE4, 0x0D, 0x00, 0x00, 0x00, 0xF1, 0xE7, 
  0x13, 0x00, 0x00, 0x00, 0xF1, 0xE1, 0x0E, 0x00, 0x00, 0x00, 
  0xF1, 0xE2, 0x12, 0x00, 0x00, 0x00, 0xF8, 0xF1, 0xE4, 0x0E, 
  0x00, 0x00, 0x00, 0xF1, 0xE7, 0x12, 0x00, 0x00, 0x00, 0xF1, 
  0xE1, 0x0F, 0x00, 0x00, 0x00, 0xF1, 0xE2, 0x11, 0x00, 0x00, 
  0x00, 0xF8, 0xF1, 0xE4, 0x0F, 0x00, 0x00, 0x00, 0xF1, 0xE7, 
  0x11, 0x00, 0x00, 0x00, 0xF4

操作码 接下来分析对应含义

函数含义

0xF1

unsigned __int64 __fastcall sub_555555400B5F(__int64 a1)
{
  int *v2; // [rsp+28h] [rbp-18h]
  unsigned __int64 v3; // [rsp+38h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  v2 = (*(a1 + 16) + 2LL);
  switch ( *(*(a1 + 16) + 1LL) )
  {
    case 0xE1:
      *a1 = *(sbb + *v2);
      break;
    case 0xE2:
      *(a1 + 4) = *(sbb + *v2);
      break;
    case 0xE3:
      *(a1 + 8) = *(sbb + *v2);
      break;
    case 0xE4:
      *(sbb + *v2) = *a1;
      break;
    case 0xE5:
      *(a1 + 12) = *(sbb + *v2);
      break;
    case 0xE7:
      *(sbb + *v2) = *(a1 + 4);
      break;
    default:
      break;
  }
  *(a1 + 16) += 6LL;
  return __readfsqword(0x28u) ^ v3;
}

类似于move 取决于后面的

0XF2

//0XF2
unsigned __int64 __fastcall sub_555555400A64(__int64 a1)
{
  unsigned __int64 v2; // [rsp+18h] [rbp-8h]

  v2 = __readfsqword(0x28u);
  *a1 ^= *(a1 + 4);
  ++*(a1 + 16);
  return __readfsqword(0x28u) ^ v2;
}

异或xor

0XF5

//0xF5
unsigned __int64 __fastcall sub_555555400AC5(__int64 a1)
{
  const char *buf; // [rsp+10h] [rbp-10h]
  unsigned __int64 v3; // [rsp+18h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  buf = sbb;
  read(0, sbb, 0x20uLL);
  dword_5555556022A4 = strlen(buf);
  if ( dword_5555556022A4 != 21 )
  {
    puts("WRONG!");
    exit(0);
  }
  ++*(a1 + 16);
  return __readfsqword(0x28u) ^ v3;
}

好像是个长度判断

0XF4

//0XF4
unsigned __int64 __fastcall sub_555555400956(__int64 a1)
{
  unsigned __int64 v2; // [rsp+18h] [rbp-8h]

  v2 = __readfsqword(0x28u);
  ++*(a1 + 16);
  return __readfsqword(0x28u) ^ v2;
}

没啥用 nop

0XF7

//0XF7
unsigned __int64 __fastcall sub_555555400A08(__int64 a1)
{
  unsigned __int64 v2; // [rsp+18h] [rbp-8h]

  v2 = __readfsqword(0x28u);
  *a1 *= *(a1 + 12);
  ++*(a1 + 16);
  return __readfsqword(0x28u) ^ v2;
}

mul乘积

0XF8

0xF8
unsigned __int64 __fastcall sub_5555554008F0(int *a1)
{
  int v2; // [rsp+14h] [rbp-Ch]
  unsigned __int64 v3; // [rsp+18h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  v2 = *a1;
  *a1 = a1[1];
  a1[1] = v2;
  ++*(a1 + 2);
  return __readfsqword(0x28u) ^ v3;
}

swap 交换

0XF6

//0XF6
unsigned __int64 __fastcall sub_55555540099C(__int64 a1)
{
  unsigned __int64 v2; // [rsp+18h] [rbp-8h]

  v2 = __readfsqword(0x28u);
  *a1 = *(a1 + 8) + 2 * *(a1 + 4) + 3 * *a1;
  ++*(a1 + 16);
  return __readfsqword(0x28u) ^ v2;
}

一个函数

解析脚本

格式化一下

opca = [[0xF5],
        [0xF1, 0xE1, 0x00, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x20, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x01, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x21, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x02, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x22, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x03, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x23, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x04, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x24, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x05, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x25, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x06, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x26, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x07, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x27, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x08, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x28, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x09, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x29, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0A, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x2A, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0B, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x2B, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0C, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x2C, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0D, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x2D, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0E, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x2E, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0F, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x2F, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x10, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x30, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x11, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x31, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x12, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x32, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x13, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x33, 0x00, 0x00, 0x00],

        [0xF4],
        [0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, ]
        [0xF5],
        [0xF1, 0xE1, 0x00, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x01, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x00, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x01, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x02, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x01, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x02, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x03, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x02, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x03, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x04, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x03, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x04, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x05, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x04, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x05, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x06, 0x00, 0x00, 0x00],
        [0xF2],
        [0xF1, 0xE4, 0x05, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x06, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x07, 0x00, 0x00, 0x00],
        [0xF1, 0xE3, 0x08, 0x00, 0x00, 0x00],
        [0xF1, 0xE5, 0x0C, 0x00, 0x00, 0x00],
        [0xF6],
        [0xF7],
        [0xF1, 0xE4, 0x06, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x07, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x08, 0x00, 0x00, 0x00],
        [0xF1, 0xE3, 0x09, 0x00, 0x00, 0x00],
        [0xF1, 0xE5, 0x0C, 0x00, 0x00, 0x00],
        [0xF6],
        [0xF7],
        [0xF1, 0xE4, 0x07, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x08, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x09, 0x00, 0x00, 0x00],
        [0xF1, 0xE3, 0x0A, 0x00, 0x00, 0x00],
        [0xF1, 0xE5, 0x0C, 0x00, 0x00, 0x00],
        [0xF6],
        [0xF7],
        [0xF1, 0xE4, 0x08, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0D, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x13, 0x00, 0x00, 0x00],
        [0xF8],
        [0xF1, 0xE4, 0x0D, 0x00, 0x00, 0x00],
        [0xF1, 0xE7, 0x13, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0E, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x12, 0x00, 0x00, 0x00],
        [0xF8],
        [0xF1, 0xE4, 0x0E, 0x00, 0x00, 0x00],
        [0xF1, 0xE7, 0x12, 0x00, 0x00, 0x00],
        [0xF1, 0xE1, 0x0F, 0x00, 0x00, 0x00],
        [0xF1, 0xE2, 0x11, 0x00, 0x00, 0x00],
        [0xF8],
        [0xF1, 0xE4, 0x0F, 0x00, 0x00, 0x00],
        [0xF1, 0xE7, 0x11, 0x00, 0x00, 0x00],
        [0xF4]]

for x in opca:
    if x[0] == 0xF1:
        if x[1] == 0xE1:
            print(f"move e1 flag[{x[2]}]")
        if x[1] == 0xE2:
            print(f"move e2 flag[{x[2]}]")
        if x[1] == 0xE3:
            print(f"move e3 flag[{x[2]}]")
        if x[1] == 0xE4:
            print(f"move flag[{x[2]}] e1")
        if x[1] == 0xE5:
            print(f"move e4 flag[{x[2]}]")
        if x[1] == 0xE7:
            print(f"move flag[{x[2]}] e2")
    elif x[0] == 0xf2:
        print("xor e1 e2")
    # elif x[0] == 0XF4:
    #     print("nop")
    elif x[0] == 0xF5:
        print("len")
    elif x[0] == 0xF6:
        print("mov e1 3*e1+2*e2+e3")
    elif x[0] == 0xf7:
        print("mul e1 e2")
    elif x[0] == 0xf8:
        print("swap e1 e2")

结果为

#一看第一段就是假的
read_len
move e1 flag[0]
xor e1 e2
move flag[32] e1
move e1 flag[1]
xor e1 e2
move flag[33] e1
move e1 flag[2]
xor e1 e2
move flag[34] e1
move e1 flag[3]
xor e1 e2
move flag[35] e1
move e1 flag[4]
xor e1 e2
move flag[36] e1
move e1 flag[5]
xor e1 e2
move flag[37] e1
move e1 flag[6]
xor e1 e2
move flag[38] e1
move e1 flag[7]
xor e1 e2
move flag[39] e1
move e1 flag[8]
xor e1 e2
move flag[40] e1
move e1 flag[9]
xor e1 e2
move flag[41] e1
move e1 flag[10]
xor e1 e2
move flag[42] e1
move e1 flag[11]
xor e1 e2
move flag[43] e1
move e1 flag[12]
xor e1 e2
move flag[44] e1
move e1 flag[13]
xor e1 e2
move flag[45] e1
move e1 flag[14]
xor e1 e2
move flag[46] e1
move e1 flag[15]
xor e1 e2
move flag[47] e1
move e1 flag[16]
xor e1 e2
move flag[48] e1
move e1 flag[17]
xor e1 e2
move flag[49] e1
move e1 flag[18]
xor e1 e2
move flag[50] e1
move e1 flag[19]
xor e1 e2
move flag[51] e1

#从这段开始是真的 直接逆
read_len
#下面三段都是异或
move e1 flag[0]
move e2 flag[1]
xor e1 e2
move flag[0] e1

move e1 flag[1]
move e2 flag[2]
xor e1 e2
move flag[1] e1

move e1 flag[2]
move e2 flag[3]
xor e1 e2
move flag[2] e1

move e1 flag[3]
move e2 flag[4]
xor e1 e2
move flag[3] e1

move e1 flag[4]
move e2 flag[5]
xor e1 e2
move flag[4] e1

move e1 flag[5]
move e2 flag[6]
xor e1 e2
move flag[5] e1
#下面三段都是相乘
move e1 flag[6]
move e2 flag[7]
move e3 flag[8]
move e4 flag[12]
mov e1 3*e1+2*e2+e3
mul e1 e4
move flag[6] e1

move e1 flag[7]
move e2 flag[8]
move e3 flag[9]
move e4 flag[12]
mov e1 3*e1+2*e2+e3
mul e1 e4
move flag[7] e1

move e1 flag[8]
move e2 flag[9]
move e3 flag[10]
move e4 flag[12]
mov e1 3*e1+2*e2+e3
mul e1 e4
move flag[8] e1
#下面三段都是交换
move e1 flag[13]
move e2 flag[19]
swap e1 e2
move flag[13] e1
move flag[19] e2

move e1 flag[14]
move e2 flag[18]
swap e1 e2
move flag[14] e1
move flag[18] e2

move e1 flag[15]
move e2 flag[17]
swap e1 e2
move flag[15] e1
move flag[17] e2

flag z3求解！

from z3 import *

flag = [0x69, 0x45, 0x2A, 0x37, 0x09, 0x17, 0xC5, 0x0B, 0x5C, 0x72,
        0x33, 0x76, 0x33, 0x21, 0x74, 0x31, 0x5F, 0x33, 0x73, 0x72,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00]
flag[15], flag[17] = flag[17], flag[15]
flag[14], flag[18] = flag[18], flag[14]
flag[13], flag[19] = flag[19], flag[13]
#
# so = Solver()
# e1 = BitVec("e1", 8)
# e2 = BitVec("e2",8)
# e3 = BitVec("e3", 8)
# e4 = BitVec("e4", 8)
#
# so.add(e2 == 0x72)
# so.add(e3 == 0x33)
# so.add(e4 == 0x33)
# so.add((3 * e1 + 2 * e2 + e3) * e4 == 0x5C)
# print(so.check())
# print(so.model())
flag[8] = 95
#
# so = Solver()
# e1 = BitVec("e1", 8)
# e2 = BitVec("e2",8)
# e3 = BitVec("e3", 8)
# e4 = BitVec("e4", 8)
#
# so.add(e2 == flag[8])
# so.add(e3 == flag[9])
# so.add(e4 == flag[12])
# so.add((3 * e1 + 2 * e2 + e3) * e4== flag[7])
# print(so.check())
# print(so.model())

flag[7] = 51

so = Solver()
e1 = BitVec("e1", 8)
e2 = BitVec("e2", 8)
e3 = BitVec("e3", 8)
e4 = BitVec("e4", 8)

so.add(e2 == flag[7])
so.add(e3 == flag[8])
so.add(e4 == flag[12])
so.add((3 * e1 + 2 * e2 + e3) * e4 == flag[6])
print(so.check())
print(so.model())

flag[6] = 118
flag[5]^=flag[6]
flag[4]^=flag[5]
flag[3]^=flag[4]
flag[2]^=flag[3]
flag[1]^=flag[2]
flag[0]^=flag[1]
print(flag)
for x in flag:
        print(chr(x),end="")

Y0u_hav3_r3v3rs3_1t!

posted @ 2022-01-15 21:36  FW_ltlly  阅读(160)  评论(0)  编辑  收藏  举报