elf文件，IDA中打开，定位main函数查看伪代码：

int __cdecl main(int argc, const char **argv, const char **envp)
{
  char *v3; // rsi
  int result; // eax
  signed int i; // [rsp+2Ch] [rbp-124h]
  char v6[264]; // [rsp+40h] [rbp-110h]
  __int64 v7; // [rsp+148h] [rbp-8h]

  memset(v6, 0, 0x100uLL);
  v3 = (char *)256;
  printf("Input your flag:\n", 0LL);
  get_line(v6, 256LL);
  if ( strlen(v6) != 33 )
    goto LABEL_12;
  for ( i = 1; i < 33; ++i )
    v6[i] ^= v6[i - 1];
  v3 = global;
  if ( !strncmp(v6, global, 0x21uLL) )
    printf("Success", v3);
  else
LABEL_12:
    printf("Failed", v3);
  result = __stack_chk_guard;
  if ( __stack_chk_guard == v7 )
    result = 0;
  return result;
}

用户输入一个长度为33的字符串，字符串中的字符分别和前一个字符异或（对应得ASCII码）后和变量global的前0x21个字符比对。逻辑并不复杂，提取global的值：

导出数据

unsigned char ida_chars[] =
{
    0x66, 0x0A, 0x6B, 0x0C, 0x77, 0x26, 0x4F, 0x2E, 0x40, 0x11,
    0x78, 0x0D, 0x5A, 0x3B, 0x55, 0x11, 0x70, 0x19, 0x46, 0x1F,
    0x76, 0x22, 0x4D, 0x23, 0x44, 0x0E, 0x67, 0x06, 0x68, 0x0F,
    0x47, 0x32, 0x4F, 0x00
};

编写解密脚本：

FLAG：

flag{QianQiuWanDai_YiTongJiangHu}

点击数：606