BUU_RE_刮开有奖

32,无壳

 

 

 shift+f12查字符串,跟进

到主函数:

INT_PTR __stdcall DialogFunc(HWND hDlg, UINT a2, WPARAM a3, LPARAM a4)
{
  const char *v4; // esi
  const char *v5; // edi
  int v7[2]; // [esp+8h] [ebp-20030h] BYREF
  int v8; // [esp+10h] [ebp-20028h]
  int v9; // [esp+14h] [ebp-20024h]
  int v10; // [esp+18h] [ebp-20020h]
  int v11; // [esp+1Ch] [ebp-2001Ch]
  int v12; // [esp+20h] [ebp-20018h]
  int v13; // [esp+24h] [ebp-20014h]
  int v14; // [esp+28h] [ebp-20010h]
  int v15; // [esp+2Ch] [ebp-2000Ch]
  int v16; // [esp+30h] [ebp-20008h]
  CHAR String[65536]; // [esp+34h] [ebp-20004h] BYREF
  char v18[65536]; // [esp+10034h] [ebp-10004h] BYREF

  if ( a2 == 272 )
    return 1;
  if ( a2 != 273 )
    return 0;
  if ( (_WORD)a3 == 1001 )
  {
    memset(String, 0, 65535u);
    GetDlgItemTextA(hDlg, 1000, String, 65535);
    if ( strlen(String) == 8 )
    {
      v7[0] = 90;
      v7[1] = 74;
      v8 = 83;
      v9 = 69;
      v10 = 67;
      v11 = 97;
      v12 = 78;
      v13 = 72;
      v14 = 51;
      v15 = 110;
      v16 = 103;
      sub_4010F0((int)v7, 0, 10);
      memset(v18, 0, 65535u);
      v18[0] = String[5];
      v18[2] = String[7];
      v18[1] = String[6];
      v4 = sub_401000((int)v18, strlen(v18));
      memset(v18, 0, 0xFFFFu);
      v18[1] = String[3];
      v18[0] = String[2];
      v18[2] = String[4];
      v5 = sub_401000((int)v18, strlen(v18));
      if ( String[0] == v7[0] + 34
        && String[1] == v10
        && 4 * String[2] - 141 == 3 * v8
        && String[3] / 4 == 2 * (v13 / 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;
}

注意到输出上面有特殊字符串,跟进后发现:

 

 

 有一串像base64的字符串,刚开始以为是自定义的base64,拿去在线解,结果:

 

 

 然后试了直接解码,就出了:

分别对应v4:jMV,v5:WP1

前面分析应该可以得知flag是八位,现在还差两位,

注意:

 

 

 

 

 

 这两段将字符串赋值到String,所以现在得到的flag就有:

flag{__WP1jMV}

 

 

 根据这个能知道前两位是"|C"但是提交之后会发现是错的

看了大佬的wp,发现这些值和他的不一样,换了个ida就可以了:

 

 

 但是当我直接把v9默认成90了,结果还是不对,仔细观察一番发现有个函数对v9进行处理:

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;
}

这里把伪代码转换成c语言:

#include <stdio.h>
#include <string.h>

int  sub_4010F0(char* 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 = 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;
}
int main(void)
{
    char str[] = "ZJSECaNH3ng";
    sub_4010F0(str,0,10);
    printf("%s", str);
    return 0;
}

其中的字符串"ZJ......"是v9到v19的ascii码,最开始我一直没找到

接下来运行出来:

 

 然后想了想

发现这个运行得到的字符串替代了v9到v19,所以:

 

 那么v9代表的就是3,v13代表的就是J

最后拼起来就是:

flag{UJWP1jMp}