[C++知识库]攻防世界 Reverse logmein

1.file查看文件格式

64位程序

2.IDA64打开

  strcpy(v8, ":\"AL_RT^L*.?+6/46");
  v7 = 0x65626D61726168LL;
  v6 = 7;
  printf("Welcome to the RC3 secure password guesser.\n");
  printf("To continue, you must enter the correct password.\n");
  printf("Enter your guess: ");
  __isoc99_scanf("%32s", s);
  v3 = strlen(s);                               // s的长度
  if ( v3 < strlen(v8) )
    incorrcet_password();
  for ( i = 0; i < strlen(s); ++i )
  {
    if ( i >= strlen(v8) )
      incorrcet_password();
    if ( s[i] != (char)(*((_BYTE *)&v7 + i % v6) ^ v8[i]) )
      incorrcet_password();
  }
  correct_password();

我们的目标是拿到密码
异或加密v7
v7 = 0x65626D61726168LL;

3.exp

k=str(bytes.fromhex(hex(28537194573619560)[2:]))[-2:1:-1]
#LL长整型数，需要转成十六进制再转换成字符，又因为是小端储存，所以要将字符串倒置
v= ":\"AL_RT^L*.?+6/46"
flag=''
for i in range(len(v)):
      flag+=chr(ord(v[i])^(ord(k[(i%7)])))
print(flag)

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