这个题可以说是比较坑了（还不是我很弱...）
Linux跑一下：
要输密码
ida打开看看：
int __cdecl main(int argc, const char **argv, const char **envp) { __int64 v3; // rax __int64 v4; // rax __int64 v5; // rax __int64 v6; // rax __int64 v7; // rax __int64 v8; // rax __int64 v9; // rax __int64 v10; // rax __int64 v11; // rax __int64 v12; // rax __int64 v13; // rax __int64 v14; // rax __int64 v15; // rax __int64 v16; // rax __int64 v17; // rax __int64 v18; // rax __int64 v19; // rax __int64 v20; // rax __int64 v21; // rax int result; // eax __int64 v23; // rax __int64 v24; // rax __int64 v25; // rax __int64 v26; // rax __int64 v27; // rax __int64 v28; // rax __int64 v29; // rax __int64 v30; // rax __int64 v31; // rax __int64 v32; // rax __int64 v33; // rax __int64 v34; // rax __int64 v35; // rax __int64 v36; // rax __int64 v37; // rax char v38; // [rsp+Fh] [rbp-71h] char v39; // [rsp+10h] [rbp-70h] char v40; // [rsp+20h] [rbp-60h] _BYTE *v41; // [rsp+28h] [rbp-58h] char v42; // [rsp+30h] [rbp-50h] unsigned __int64 v43; // [rsp+68h] [rbp-18h] v43 = __readfsqword(0x28u); std::operator<<<std::char_traits<char>>(&std::cout, "Enter the valid key!\n", envp); std::operator>><char,std::char_traits<char>>(&edata, &v42); std::allocator<char>::allocator((__int64)&v38); std::string::string(&v39, &v42, &v38); md5((MD5 *)&v40, (const std::string *)&v39); v41 = (_BYTE *)std::string::c_str((std::string *)&v40); std::string::~string((std::string *)&v40); std::string::~string((std::string *)&v39); std::allocator<char>::~allocator(&v38); if ( *v41 != 55 || v41[1] != 56 || v41[2] != 48 || v41[3] != 52 || v41[4] != 51 || v41[5] != 56 || v41[6] != 100 || v41[7] != 53 || v41[8] != 98 || v41[9] != 54 || v41[10] != 101 || v41[11] != 50 || v41[12] != 57 || v41[13] != 100 || v41[14] != 98 || v41[15] != 48 || v41[16] != 56 || v41[17] != 57 || v41[18] != 56 || v41[19] != 98 || v41[20] != 99 || v41[21] != 52 || v41[22] != 102 || v41[23] != 48 || v41[24] != 50 || v41[25] != 50 || v41[26] != 53 || v41[27] != 57 || v41[28] != 51 || v41[29] != 53 || v41[30] != 99 || v41[31] != 48 ) { v23 = std::operator<<<std::char_traits<char>>(&std::cout, 73LL); v24 = std::operator<<<std::char_traits<char>>(v23, 110LL); v25 = std::operator<<<std::char_traits<char>>(v24, 118LL); v26 = std::operator<<<std::char_traits<char>>(v25, 97LL); v27 = std::operator<<<std::char_traits<char>>(v26, 108LL); v28 = std::operator<<<std::char_traits<char>>(v27, 105LL); v29 = std::operator<<<std::char_traits<char>>(v28, 100LL); v30 = std::operator<<<std::char_traits<char>>(v29, 32LL); v31 = std::operator<<<std::char_traits<char>>(v30, 75LL); v32 = std::operator<<<std::char_traits<char>>(v31, 101LL); v33 = std::operator<<<std::char_traits<char>>(v32, 121LL); v34 = std::operator<<<std::char_traits<char>>(v33, 33LL); v35 = std::operator<<<std::char_traits<char>>(v34, 32LL); v36 = std::operator<<<std::char_traits<char>>(v35, 58LL); v37 = std::operator<<<std::char_traits<char>>(v36, 40LL); std::ostream::operator<<(v37, &std::endl<char,std::char_traits<char>>); result = 0; } else { v3 = std::operator<<<std::char_traits<char>>(&std::cout, 84LL); v4 = std::operator<<<std::char_traits<char>>(v3, 104LL); v5 = std::operator<<<std::char_traits<char>>(v4, 101LL); v6 = std::operator<<<std::char_traits<char>>(v5, 32LL); v7 = std::operator<<<std::char_traits<char>>(v6, 107LL); v8 = std::operator<<<std::char_traits<char>>(v7, 101LL); v9 = std::operator<<<std::char_traits<char>>(v8, 121LL); v10 = std::operator<<<std::char_traits<char>>(v9, 32LL); v11 = std::operator<<<std::char_traits<char>>(v10, 105LL); v12 = std::operator<<<std::char_traits<char>>(v11, 115LL); v13 = std::operator<<<std::char_traits<char>>(v12, 32LL); v14 = std::operator<<<std::char_traits<char>>(v13, 118LL); v15 = std::operator<<<std::char_traits<char>>(v14, 97LL); v16 = std::operator<<<std::char_traits<char>>(v15, 108LL); v17 = std::operator<<<std::char_traits<char>>(v16, 105LL); v18 = std::operator<<<std::char_traits<char>>(v17, 100LL); v19 = std::operator<<<std::char_traits<char>>(v18, 32LL); v20 = std::operator<<<std::char_traits<char>>(v19, 58LL); v21 = std::operator<<<std::char_traits<char>>(v20, 41LL); std::ostream::operator<<(v21, &std::endl<char,std::char_traits<char>>); result = 0; } return result; }
可以看出来是先将输入的字符串进行md5加密 然后进行比对 正确就会输出一串字符
一开始我以为flag应该是输出的字符 于是：
a=[84,104,101,32,107,101,121,32,105,115,32,118,97,108,105,100,32,58,41] s='' for i in a: s+=chr(i) print(s)
结果输出是：
The key is valid :)
okey....应该是考虑错了
那么就是md5这里：
b=[55,56,48,52,51,56,100,53,98,54,101,50,57,100,98,48,56,57,56,98,99,52,102,48,50,50,53,57,51,53,99,48] s='' for i in b: s+=chr(i) print(s)
输出：
780438d5b6e29db0898bc4f0225935c0
这是md5加密后的值，把它解密：
输出是 grape
满心欢喜提交 错误......
仔细看一下这个md5的类型：
md5(md5($pass))
也就是加密了之后又进行了一遍md5加密的 所以grape是最初的字符串 780438d5b6e29db0898bc4f0225935c0是最终的密文
那么我们的key应该就是中间加密一次得到的字符串！
将 grape 加密一遍得到：
b781cbb29054db12f88f08c6e161c199
提交正确！