说实话这个题真的离谱（最开始一点线索没有，真的难顶）
首先DIEasy看看文件信息：
拖进IDA，发现主要函数WinMain：
int __stdcall WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
DialogBoxParamA(hInstance, (LPCSTR)0x67, 0, DialogFunc, 0);
return 0;
}
只有DialogFunc一个函数相关。打开此函数，谢天谢地，有flag的线索了；
BOOL __stdcall DialogFunc(HWND hDlg, UINT a2, WPARAM a3, LPARAM a4)
{
const char *v4; // esi
const char *v5; // edi
int v7; // [esp+8h] [ebp-20030h]
int v8; // [esp+Ch] [ebp-2002Ch]
int v9; // [esp+10h] [ebp-20028h]
int v10; // [esp+14h] [ebp-20024h]
int v11; // [esp+18h] [ebp-20020h]
int v12; // [esp+1Ch] [ebp-2001Ch]
int v13; // [esp+20h] [ebp-20018h]
int v14; // [esp+24h] [ebp-20014h]
int v15; // [esp+28h] [ebp-20010h]
int v16; // [esp+2Ch] [ebp-2000Ch]
int v17; // [esp+30h] [ebp-20008h]
CHAR String; // [esp+34h] [ebp-20004h]
char v19; // [esp+35h] [ebp-20003h]
char v20; // [esp+36h] [ebp-20002h]
char v21; // [esp+37h] [ebp-20001h]
char v22; // [esp+38h] [ebp-20000h]
char v23; // [esp+39h] [ebp-1FFFFh]
char v24; // [esp+3Ah] [ebp-1FFFEh]
char v25; // [esp+3Bh] [ebp-1FFFDh]
char v26; // [esp+10034h] [ebp-10004h]
char v27; // [esp+10035h] [ebp-10003h]
char v28; // [esp+10036h] [ebp-10002h]
if ( a2 == 272 )
return 1;
if ( a2 != 273 )
return 0;
if ( (_WORD)a3 == 1001 )
{
memset(&String, 0, 0xFFFFu);
GetDlgItemTextA(hDlg, 1000, &String, 0xFFFF);// String就是我们输入的flag，长度为8；
if ( strlen(&String) == 8 )
{
v7 = 90;
v8 = 74;
v9 = 83;
v10 = 69;
v11 = 67;
v12 = 97;
v13 = 78;
v14 = 72;
v15 = 51;
v16 = 110;
v17 = 103;
sub_4010F0((int)&v7, 0, 10); // 搞事情？？？
// test
memset(&v26, 0, 0xFFFFu);
v26 = v23;
v28 = v25;
v27 = v24;
v4 = (const char *)sub_401000(&v26, strlen(&v26));
memset(&v26, 0, 0xFFFFu);
v27 = v21;
v26 = v20;
v28 = v22;
v5 = (const char *)sub_401000(&v26, strlen(&v26));
if ( String == v7 + 34
&& v19 == v11
&& 4 * v20 - 141 == 3 * v9
&& v21 / 4 == 2 * (v14 / 9)
&& !strcmp(v4, "ak1w")
&& !strcmp(v5, "V1Ax") )
{
MessageBoxA(hDlg, "U g3t 1T!", "@_@", 0);
}
}
return 0;
}
if ( (_WORD)a3 != 1 && (_WORD)a3 != 2 )
return 0;
EndDialog(hDlg, (unsigned __int16)a3);
return 1;
转到搞事情函数：
// this func includes i,v5,v6&a1=90,a2=0,a3=10;
int __cdecl sub_4010F0(int a1, int a2, int a3)
{
int result; // eax
int i; // esi
int v5; // ecx
int v6; // edx
result = a3;
for ( i = a2; i <= a3; a2 = i )
{
v5 = 4 * i;
v6 = *(_DWORD *)(4 * i + a1);
if ( a2 < result && i < result )
{
do
{
if ( v6 > *(_DWORD *)(a1 + 4 * result) )
{
if ( i >= result )
break;
++i;
*(_DWORD *)(v5 + a1) = *(_DWORD *)(a1 + 4 * result);
if ( i >= result )
break;
while ( *(_DWORD *)(a1 + 4 * i) <= v6 )
{
if ( ++i >= result )
goto LABEL_13;
}
if ( i >= result )
break;
v5 = 4 * i;
*(_DWORD *)(a1 + 4 * result) = *(_DWORD *)(4 * i + a1);
}
--result;
}
while ( i < result );
}
LABEL_13:
*(_DWORD *)(a1 + 4 * result) = v6;
sub_4010F0(a1, a2, i - 1);
result = a3;
++i;
}
return result;
}
脑壳疼，转C++代码跑一下：
#include <bits/stdc++.h>
using namespace std;
int __cdecl sub_4010F0(char *a1, int a2, int a3)
{
int result;
int i;
int v5;
int v6;
result = a3;
for (i = a2; i <= a3; a2 = i)
{
v5 = i;
v6 = a1[i];
if (a2 < result && i < result)
{
do
{
if (v6 >a1[result])
{
if (i >= result)
break;
++i;
a1[v5] = a1[result];
if (i >= result)
break;
while (a1[i] <= v6)
{
if (++i >= result)
goto LABEL_13;
}
if (i >= result)
break;
v5 = i;
a1[result] = a1[i];
}
--result;
} while (i < result);
}
LABEL_13:
a1[result] = v6;
sub_4010F0(a1, a2, i - 1);
result = a3;
++i;
}
return result;
}
char str[20] = { 90,74,83,69,67,97,78,72,51,110,103 };
int main()
{
cout << str << endl;
sub_4010F0(str, 0, 10);
for (int i = 0; i < 11; ++i) {
cout << str[i];
}
return 0;
}
得到如下结果
.png)
在这之后还有一个base64加密。结合报正确的判定：
if ( String == v7 + 34
&& v19 == v11
&& 4 * v20 - 141 == 3 * v9
&& v21 / 4 == 2 * (v14 / 9)
&& !strcmp(v4, "ak1w")
&& !strcmp(v5, "V1Ax") )
得出字符串 UJWP1jMp ，包上flag{}提交。
（某note秒粘贴真好用）