CVE-2012-0158 MSCOMCTL控件漏洞分析

来源：互联网发布：淘宝客退款佣金还收吗编辑：程序博客网时间：2024/05/16 10:59

参考：http://bbs.pediy.com/showthread.php?t=149957（样本是此链接提供的样本）

环境：

xp sp3 / word2007

运行样本后，会弹出计算器

因为此类型的exp的shellcode 在运行的时候都会释放文件，释放文件时需要调用kernel32.dll 中的GetFileSize函数来判断需要释放的文件，

所以在windbg开始调试poc时，在GetFileSize函数下断点，bu kernel32!GetFileSize,但是word运行时会调用很多次GetFileSize，直接下断点的话，会执行很多次。

我们知道漏洞出现在MSCOMCTL.OCX中，因此我们可以等待加载MSCOMCTL.OCX后在对GetFileSize下断点

sxe ld:MSCOMCTL.OCX

加载MSCOMCTL.OCX模块时会断下来

0:000> g(278.288): Unknown exception - code e0000002 (first chance)ModLoad: 27580000 27685000   C:\WINDOWS\system32\MSCOMCTL.OCXeax=00000000 ebx=00000000 ecx=03c30000 edx=7c92e4f4 esi=00000000 edi=00000000eip=7c92e4f4 esp=0012392c ebp=00123a20 iopl=0         nv up ei ng nz ac pe nccs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00000296ntdll!KiFastSystemCallRet:7c92e4f4 c3              ret0:000> bp kernel32!GetFileSize0:000> bl 0 e 7c810b07     0001 (0001)  0:**** kernel32!GetFileSize

然后g运行程序，程序停在GetFileSize处，

然后gu跳出GetFileSize函数，程序已经进入shellcode区域

观察右下角堆栈调用，可知上层调用位于

MSCOMCTL!DllGetClassObject+0x41cc6 处

u MSCOMCTL!DllGetClassObject+0x41cc6MSCOMCTL!DllGetClassObject+0x41cc6:275c8a0a 8bf0            mov     esi,eax275c8a0c 83c40c          add     esp,0Ch275c8a0f 85f6            test    esi,esi275c8a11 7c3d            jl      MSCOMCTL!DllGetClassObject+0x41d0c (275c8a50)275c8a13 837df800        cmp     dword ptr [ebp-8],0275c8a17 8b7d08          mov     edi,dword ptr [ebp+8]275c8a1a 742a            je      MSCOMCTL!DllGetClassObject+0x41d02 (275c8a46)275c8a1c 83650c00        and     dword ptr [ebp+0Ch],0

地址位于275c8a0a 处。猜测出现问题的地方就在此附近。

IDA打开MSCOMCTL.OCX模块，定位到275c8a0a处附近

.text:275C89C7 ; int __stdcall sub_275C89C7(int, BSTR bstrString).text:275C89C7 sub_275C89C7    proc near               ; CODE XREF: sub_275C8807+10p.text:275C89C7                                         ; sub_275E7004+11p ....text:275C89C7.text:275C89C7 var_14          = dword ptr -14h.text:275C89C7 dwBytes         = dword ptr -0Ch.text:275C89C7 var_8           = dword ptr -8.text:275C89C7 var_4           = dword ptr -4.text:275C89C7 arg_0           = dword ptr  8.text:275C89C7 bstrString      = dword ptr  0Ch.text:275C89C7.text:275C89C7 ; FUNCTION CHUNK AT .text:275D3085 SIZE 0000001D BYTES.text:275C89C7.text:275C89C7                 push    ebp.text:275C89C8                 mov     ebp, esp.text:275C89CA                 sub     esp, 14h.text:275C89CD                 push    ebx.text:275C89CE                 mov     ebx, [ebp+bstrString].text:275C89D1                 push    esi.text:275C89D2                 push    edi.text:275C89D3                 push    0Ch             ; dwBytes.text:275C89D5                 lea     eax, [ebp+var_14].text:275C89D8                 push    ebx             ; lpMem.text:275C89D9                 push    eax             ; int.text:275C89DA                 call    __keyfun.text:275C89DF                 add     esp, 0Ch.text:275C89E2                 test    eax, eax.text:275C89E4                 jl      short loc_275C8A52.text:275C89E6                 cmp     [ebp+var_14], 6A626F43h.text:275C89ED                 jnz     loc_275D3085.text:275C89F3                 cmp     [ebp+dwBytes], 8.text:275C89F7                 jb      loc_275D3085.text:275C89FD                 push    [ebp+dwBytes]   ; dwBytes.text:275C8A00                 lea     eax, [ebp+var_8].text:275C8A03                 push    ebx             ; lpMem.text:275C8A04                 push    eax             ; int.text:275C8A05                 call    __keyfun.text:275C8A0A                 mov     esi, eax.text:275C8A0C                 add     esp, 0Ch.text:275C8A0F                 test    esi, esi.text:275C8A11                 jl      short loc_275C8A50.text:275C8A13                 cmp     [ebp+var_8], 0.text:275C8A17                 mov     edi, [ebp+arg_0].text:275C8A1A                 jz      short loc_275C8A46.text:275C8A1C                 and     [ebp+bstrString], 0.text:275C8A20                 lea     eax, [ebp+bstrString].text:275C8A23                 push    ebx             ; int.text:275C8A24                 push    eax             ; len.text:275C8A25                 call    sub_275C8A59.text:275C8A2A                 mov     esi, eax.text:275C8A2C                 pop     ecx.text:275C8A2D                 test    esi, esi.text:275C8A2F                 pop     ecx.text:275C8A30                 jl      short loc_275C8A50.text:275C8A32                 push    [ebp+bstrString] ; strIn.text:275C8A35                 lea     ecx, [edi-24h].text:275C8A38                 call    sub_27585BE7.text:275C8A3D                 push    [ebp+bstrString] ; bstrString.text:275C8A40                 call    ds:SysFreeString.text:275C8A46.text:275C8A46 loc_275C8A46:                           ; CODE XREF: sub_275C89C7+53j.text:275C8A46                 cmp     [ebp+var_4], 0.text:275C8A4A                 jnz     loc_275D308F.text:275C8A50.text:275C8A50 loc_275C8A50:                           ; CODE XREF: sub_275C89C7+4Aj.text:275C8A50                                         ; sub_275C89C7+69j ....text:275C8A50                 mov     eax, esi.text:275C8A52.text:275C8A52 loc_275C8A52:                           ; CODE XREF: sub_275C89C7+1Dj.text:275C8A52                                         ; sub_275C89C7+A6C3j.text:275C8A52                 pop     edi.text:275C8A53                 pop     esi.text:275C8A54                 pop     ebx.text:275C8A55                 leave.text:275C8A56                 retn    8.text:275C8A56 sub_275C89C7    endp

发编译如下：

int __stdcall sub_275C89C7(int a1, BSTR bstrString){  BSTR v2; // ebx@1  int result; // eax@1  int v4; // esi@4  int v5; // [sp+Ch] [bp-14h]@1  SIZE_T dwBytes; // [sp+14h] [bp-Ch]@3  int v7; // [sp+18h] [bp-8h]@4  int v8; // [sp+1Ch] [bp-4h]@8  v2 = bstrString;  result = _keyfun((int)&v5, bstrString, 0xCu);  if ( result >= 0 )  {    if ( v5 == 1784835907 && dwBytes >= 8 )    {      v4 = _keyfun((int)&v7, v2, dwBytes);      if ( v4 >= 0 )      {        if ( !v7 )          goto LABEL_8;        bstrString = 0;        v4 = sub_275C8A59((UINT)&bstrString, (int)v2);        if ( v4 >= 0 )        {          sub_27585BE7(bstrString);          SysFreeString(bstrString);LABEL_8:          if ( v8 )            v4 = sub_275C8B2B(a1 + 20, v2);          return v4;        }      }      return v4;    }    result = -2147418113;  }  return result;}

int __cdecl _keyfun(int a1, LPVOID lpMem, SIZE_T dwBytes){  LPVOID v3; // ebx@1  int result; // eax@1  LPVOID v5; // eax@3  int v6; // esi@4  int v7; // [sp+Ch] [bp-4h]@1  LPVOID lpMema; // [sp+1Ch] [bp+Ch]@3  v3 = lpMem;  result = (*(int (__stdcall **)(LPVOID, int *, signed int, _DWORD))(*(_DWORD *)lpMem + 12))(lpMem, &v7, 4, 0);  if ( result >= 0 )  {    if ( v7 == dwBytes )    {      v5 = HeapAlloc(hHeap, 0, dwBytes);      lpMema = v5;      if ( v5 )      {        v6 = (*(int (__stdcall **)(LPVOID, LPVOID, SIZE_T, _DWORD))(*(_DWORD *)v3 + 12))(v3, v5, dwBytes, 0);        if ( v6 >= 0 )        {          qmemcpy((void *)a1, lpMema, dwBytes);          v6 = (*(int (__stdcall **)(LPVOID, _UNKNOWN *, SIZE_T, _DWORD))(*(_DWORD *)v3 + 12))(                 v3,                 &unk_27632368,                 ((dwBytes + 3) & 0xFFFFFFFC) - dwBytes,                 0);        }        HeapFree(hHeap, 0, lpMema);        result = v6;      }      else      {        result = -2147024882;      }    }    else    {      result = -2147418113;    }  }  return result;}

根据上结果可以大致判断，异常出现原因是因为对字符串长度判断出问题，导致溢出。

下面使用OD具体跟踪下情况：

因为MSCOMCTL.OCX 并不在word运行起来就加载，所以一开始是不能对MSCOMCTL.OCX中的地址进行断点设置的，但是一般模块的加载都是是哟用函数LoadLibraryA函数的，

因此可以在LoadLibraryA下断点（不要一开始就下断点，因为word运行时会加载很多断点）

OD加载may.doc, F9运行，出现提示（之前运行过样本）