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[原创]MS08-021漏洞分析
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发表于: 2008-12-10 13:22
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Author:dge
我从分析这个漏洞的过程中重新认识到一些东西，写下来分享给像我一样的人们。
在分析文件格式漏洞时只用调试工具跟踪有时候很费劲。如果POC可以顺利执行shellcode，跟踪比较简单，但如果POC执行不到shellcode，就很难去解决，当然我们可以通过补丁比较确定出几个可疑函数进行重点跟踪，当然前提是你得能确定出来，如果补丁对代码的改动很大，要确定出可疑函数实非易事，即使能确定出几个来，对他们跟踪也是非常麻烦的事情，让复杂的问题变的简单，那肯定是最理想的。
认识PaiMei这个工具是在failwest的书里，虽然读完那本书已经很久了，但一直没用过这个工具，直到前几天分析这个漏洞，在分析未果的情况下，我想起了PaiMei,这才体会到了它的强大，这也是我想写这篇文章的原因。
MS08-021有两个漏洞，这是其中的一个，这个漏洞的POC在很久之前就有人公布了，这是POC的地址：86dK9s2c8@1M7q4)9K6b7g2)9J5c8W2)9J5c8Y4N6%4N6#2)9J5k6h3#2A6L8s2M7H3M7X3#2Q4x3X3g2U0L8$3#2Q4x3V1k6W2P5s2m8D9L8$3W2@1M7#2)9J5c8U0f1@1y4o6u0Q4c8f1k6Q4b7V1y4Q4z5p5y4Q4c8e0k6Q4z5f1y4Q4z5o6W2Q4c8e0c8Q4b7V1q4Q4z5o6k6b7e0@1y4Q4c8e0g2Q4z5e0u0Q4z5p5y4b7j5h3W2y4k6h3W2Q4c8f1k6Q4b7V1y4Q4z5p5y4Q4c8e0g2Q4z5o6S2Q4z5o6k6Q4c8e0k6Q4z5f1g2Q4z5e0m8Q4c8e0S2Q4b7V1k6Q4z5e0W2Q4c8e0c8Q4b7U0S2Q4b7f1q4Q4c8e0k6Q4b7V1y4Q4z5p5k6Q4c8e0k6Q4b7U0c8Q4z5f1g2Q4c8e0g2Q4b7U0m8Q4b7U0q4Q4c8e0g2Q4z5p5k6Q4z5e0S2Q4c8e0g2Q4b7V1g2Q4z5e0N6Q4c8e0N6Q4b7f1g2Q4z5o6m8Q4c8e0g2Q4z5p5c8Q4z5e0g2Q4c8e0c8Q4b7V1q4Q4z5o6k6Q4c8f1k6Q4b7V1y4Q4z5p5y4Q4c8e0S2Q4b7V1k6Q4z5e0W2Q4c8e0c8Q4b7U0S2Q4b7f1q4Q4c8e0k6Q4b7V1y4Q4z5p5k6Q4c8e0k6Q4b7U0c8Q4z5f1g2Q4c8e0g2Q4z5p5k6Q4z5e0q4Q4c8e0N6Q4z5e0c8Q4z5f1k6Q4c8e0g2Q4z5f1y4Q4b7e0S2Y4k6r3V1K6x3W2)9J5k6h3c8D9L8q4!0q4y4q4!0n7z5q4!0m8c8q4!0q4c8W2!0n7b7#2)9^5b7#2!0q4y4W2)9&6z5q4!0m8c8W2!0q4y4g2)9^5y4g2!0n7z5q4!0q4y4g2)9&6c8g2)9^5b7W2!0q4y4#2)9&6b7g2)9^5y4q4!0q4y4W2!0m8x3q4)9^5z5q4!0q4y4W2!0n7b7g2!0m8x3W2!0q4y4g2)9^5y4#2!0n7b7g2!0q4x3#2)9^5x3q4)9^5x3R3`.`.
用PaiMei和od我们可以轻松地确定出漏洞触发路径。
PlayEnhMetaFileRecord
|__MRCOLORMATCHTOTARGET::bPlay
|__IcmCreateColorSpaceByName
|__lstrcpyW
先简单了解下EMF文件格式
Header结构：
typedef struct tagENHMETAHEADER {
DWORD iType;
DWORD nSize;
RECTL rclBounds;
RECTL rclFrame;
DWORD dSignature;
DWORD nVersion;
DWORD nBytes;
DWORD nRecords;
WORD nHandles;
WORD sReserved;
DWORD nDescription;
DWORD offDescription;
DWORD nPalEntries;
SIZEL szlDevice;
SIZEL szlMillimeters;
#if (WINVER >= 0x0400)
DWORD cbPixelFormat;
DWORD offPixelFormat;
DWORD bOpenGL;
#endif /* WINVER >= 0x0400 */
#if (WINVER >= 0x0500)
SIZEL szlMicrometers;
#endif /* WINVER >= 0x0500 */
} ENHMETAHEADER, *PENHMETAHEADER;
RECORD结构
typedef struct tagENHMETARECORD
{
DWORD iType; // Record type EMR_XXX
DWORD nSize; // Record size in bytes
DWORD dParm[1]; // DWORD Array of parameters
} ENHMETARECORD;
函数原型：
BOOL PlayEnhMetaFileRecord(
HDC hdc, // handle to DC
LPHANDLETABLE lpHandletable, // metafile handle table
CONST ENHMETARECORD *lpEnhMetaRecord, // metafile record
UINT nHandles // count of handles
);
POC截图：
下边分析下这个漏洞：
.text:77EFEF66 __stdcall PlayEnhMetaFileRecord(x, x, x, x) proc near
.text:77EFEF66 ; CODE XREF: bInternalPlayEMF(x,x,x,x,x)+6A2 p
.text:77EFEF66 ; bInternalPlayEMF(x,x,x,x,x)+13B2 p ...
.text:77EFEF66
.text:77EFEF66 var_58 = dword ptr -58h
.text:77EFEF66 var_54 = dword ptr -54h
.text:77EFEF66 var_50 = dword ptr -50h
.text:77EFEF66 var_4C = dword ptr -4Ch
.text:77EFEF66 var_48 = dword ptr -48h
.text:77EFEF66 var_44 = dword ptr -44h
.text:77EFEF66 var_40 = dword ptr -40h
.text:77EFEF66 var_3C = dword ptr -3Ch
.text:77EFEF66 var_38 = dword ptr -38h
.text:77EFEF66 var_34 = dword ptr -34h
.text:77EFEF66 var_30 = dword ptr -30h
.text:77EFEF66 var_2C = dword ptr -2Ch
.text:77EFEF66 var_28 = dword ptr -28h
.text:77EFEF66 var_24 = dword ptr -24h
.text:77EFEF66 var_20 = dword ptr -20h
.text:77EFEF66 var_1C = dword ptr -1Ch
.text:77EFEF66 var_18 = dword ptr -18h
.text:77EFEF66 var_14 = dword ptr -14h
.text:77EFEF66 var_10 = dword ptr -10h
.text:77EFEF66 var_C = dword ptr -0Ch
.text:77EFEF66 var_8 = dword ptr -8
.text:77EFEF66 var_4 = dword ptr -4
.text:77EFEF66 hdc = dword ptr 8
.text:77EFEF66 lphandletable = dword ptr 0Ch
.text:77EFEF66 lpenhmetarecord = dword ptr 10h
.text:77EFEF66 nhandles = dword ptr 14h
.text:77EFEF66
.text:77EFEF66 ; FUNCTION CHUNK AT .text:77F18A61 SIZE 0000028A BYTES
.text:77EFEF66
.text:77EFEF66 mov edi, edi
.text:77EFEF68 push ebp
.text:77EFEF69 mov ebp, esp
.text:77EFEF6B sub esp, 58h
.text:77EFEF6E push ebx
.text:77EFEF6F mov ebx, [ebp+lpenhmetarecord]
.text:77EFEF72 mov eax, [ebx]
.text:77EFEF74 cmp eax, 1
.text:77EFEF77 push esi
.text:77EFEF78 push edi
.text:77EFEF79 jb short loc_77EFEF99
.text:77EFEF7B cmp eax, 122
.text:77EFEF7E ja short loc_77EFEF99
.text:77EFEF80 push [ebp+nhandles]
.text:77EFEF83 mov ecx, ebx
.text:77EFEF85 push [ebp+lphandletable]
.text:77EFEF88 push [ebp+hdc]
.text:77EFEF8B call _fpStartDocDlgW[eax*4] ; eax必须是79,这样才可以调用虚函数MRCOLORMATCHTOTARGET::bPlay
.text:77EFEF92
.text:77EFEF92 loc_77EFEF92: ; CODE XREF: PlayEnhMetaFileRecord(x,x,x,x)+19D72 j
.text:77EFEF92 ; PlayEnhMetaFileRecord(x,x,x,x)+19D80 j
.text:77EFEF92 pop edi
.text:77EFEF93 pop esi
.text:77EFEF94 pop ebx
.text:77EFEF95 leave
.text:77EFEF96 retn 10h
.text:77EFEF99 ; ---------------------------------------------------------------------------
.text:77EFEF99
.text:77EFEF99 loc_77EFEF99: ; CODE XREF: PlayEnhMetaFileRecord(x,x,x,x)+13 j
.text:77EFEF99 ; PlayEnhMetaFileRecord(x,x,x,x)+18 j
.text:77EFEF99 test eax, eax
.text:77EFEF9B js loc_77F18CD5
.text:77EFEFA1 jmp loc_77F18A61
.text:77EFEFA1 __stdcall PlayEnhMetaFileRecord(x, x, x, x) endp
上图中的6Ch偏移处的四字节必须是79000000，这样才可以让数据流到达MRCOLORMATCHTOTARGET::bPlay。
text:77F2EBB5 public: int __thiscall MRCOLORMATCHTOTARGET::bPlay(void *, struct tagHANDLETABLE *, unsigned int) proc near
.text:77F2EBB5 ; CODE XREF: PlayEnhMetaFileRecord(x,x,x,x)+25 P
.text:77F2EBB5 ; DATA XREF: .data:77F327C0 o
.text:77F2EBB5
.text:77F2EBB5 var_264 = dword ptr -264h
.text:77F2EBB5 var_260 = dword ptr -260h
.text:77F2EBB5 var_25C = dword ptr -25Ch
.text:77F2EBB5 var_258 = dword ptr -258h
.text:77F2EBB5 var_254 = dword ptr -254h
.text:77F2EBB5 var_250 = dword ptr -250h
.text:77F2EBB5 var_24C = dword ptr -24Ch
.text:77F2EBB5 var_248 = dword ptr -248h
.text:77F2EBB5 var_244 = dword ptr -244h
.text:77F2EBB5 var_240 = dword ptr -240h
.text:77F2EBB5 lp_buff = dword ptr -20Ch
.text:77F2EBB5 var_4 = dword ptr -4
.text:77F2EBB5 hdc = dword ptr 8
.text:77F2EBB5 lphandletable = dword ptr 0Ch
.text:77F2EBB5
.text:77F2EBB5 mov edi, edi
.text:77F2EBB7 push ebp
.text:77F2EBB8 mov ebp, esp
.text:77F2EBBA sub esp, 264h
.text:77F2EBC0 mov eax, ___security_cookie
.text:77F2EBC5 push ebx
.text:77F2EBC6 mov ebx, [ebp+hdc]
.text:77F2EBC9 mov [ebp+var_4], eax
.text:77F2EBCC mov eax, [ebp+lphandletable]
.text:77F2EBCF push esi
.text:77F2EBD0 push eax
.text:77F2EBD1 mov esi, ecx
.text:77F2EBD3 mov [ebp+var_258], ebx
.text:77F2EBD9 call MRCOLORMATCHTOTARGET::bCheckRecord(tagHANDLETABLE *) ;这个函数里规定[esi+0x14]+[esi+0x10]+0x1B==[esi+0x4]
.text:77F2EBDE test eax, eax
.text:77F2EBE0 jz loc_77F2ED19
.text:77F2EBE6 mov eax, [esi+8]
.text:77F2EBE9 xor ecx, ecx
.text:77F2EBEB inc ecx
.text:77F2EBEC cmp eax, ecx
.text:77F2EBEE push edi
.text:77F2EBEF mov [ebp+var_254], ecx
.text:77F2EBF5 jnz loc_77F2ED03 ; ENHMETARECORD.iType==EMR_HEADER ?
.text:77F2EBFB test [esi+0Ch], cl
.text:77F2EBFE jz loc_77F2ECB2 ; Record size是否是偶数
从上边的代码知道要触发漏洞必须符合的几个条件：
1） ENHMETARECORD.iType==EMR_HEADER，也就是第一个RECORD。
2） 当esi指向上图蓝色的位置时，([esi+0x14]+[esi+0x10]+0x1B)& 0FFFFFFFCh==[esi+0x4]。
3） Record size必须是偶数。
.text:77F2ECB2 loc_77F2ECB2: ; CODE XREF: MRCOLORMATCHTOTARGET::bPlay(void *,tagHANDLETABLE *,uint)+49 j
.text:77F2ECB2 mov edi, 10002h
.text:77F2ECB7 push edi ; const_10002
.text:77F2ECB8 push 4 ; const_4
.text:77F2ECBA lea eax, [esi+18h]
.text:77F2ECBD push eax ; lp_sz
.text:77F2ECBE push ebx ; hdc
.text:77F2ECBF call IcmGetColorSpaceByName(x,x,x,x)
.text:77F2ECC4 mov ebx, eax ;必须返回0
.text:77F2ECC6 test ebx, ebx
.text:77F2ECC8 jnz short loc_77F2ECE2
.text:77F2ECCA push edi ; int
.text:77F2ECCB push 4 ; int
.text:77F2ECCD lea eax, [esi+18h]
.text:77F2ECD0 push eax ; 指向RECORD的内容
.text:77F2ECD1 push [ebp+var_258] ; int
.text:77F2ECD7 call IcmCreateColorSpaceByName(x,x,x,x) ;有漏洞的函数
IcmGetColorSpaceByName必须返回0。
.text:77F0335B __stdcall IcmCreateColorSpaceByName(x, x, x, x) proc near
.text:77F0335B ; CODE XREF: IcmUpdateLocalDCColorSpace(x,x)+1043 p
.text:77F0335B ; IcmUpdateLocalDCColorSpace(x,x)+150B7 p ...
.text:77F0335B
.text:77F0335B var_250 = dword ptr -250h
.text:77F0335B var_24C = dword ptr -24Ch
.text:77F0335B var_248 = dword ptr -248h
.text:77F0335B var_244 = dword ptr -244h
.text:77F0335B var_240 = dword ptr -240h
.text:77F0335B String1 = word ptr -20Ch
.text:77F0335B var_4 = dword ptr -4
.text:77F0335B arg_0 = dword ptr 8
.text:77F0335B lpString2 = dword ptr 0Ch
.text:77F0335B arg_8 = dword ptr 10h
.text:77F0335B arg_C = dword ptr 14h
.text:77F0335B
.text:77F0335B mov edi, edi
.text:77F0335D push ebp
.text:77F0335E mov ebp, esp
.text:77F03360 sub esp, 250h
.text:77F03366 mov eax, ___security_cookie;使用了GS
.text:77F0336B mov edx, [ebp+lpString2]
.text:77F0336E push esi
.text:77F0336F mov esi, [ebp+arg_0]
.text:77F03372 mov [ebp+var_4], eax
.text:77F03375 push edi
.text:77F03376 xor eax, eax
.text:77F03378 mov ecx, 93h
.text:77F0337D lea edi, [ebp+var_250]
.text:77F03383 rep stosd
.text:77F03385 and [ebp+var_244], eax
.text:77F0338B mov eax, [ebp+arg_8]
.text:77F0338E mov [ebp+var_240], eax
.text:77F03394 push edx ; lpString2
.text:77F03395 lea eax, [ebp+String1]
.text:77F0339B push eax ; lpString1
.text:77F0339C mov [ebp+var_250], 50534F43h
.text:77F033A6 mov [ebp+var_24C], 400h
.text:77F033B0 mov [ebp+var_248], 24Ch
.text:77F033BA call ds:lstrcpyW(x,x) ; 如果第一个RECORD的内容足够大就可以溢出。
.text:77F033C0 push [ebp+arg_C]
.text:77F033C3 lea eax, [ebp+var_250]
.text:77F033C9 push 0
.text:77F033CB push eax
.text:77F033CC push esi
.text:77F033CD call IcmCreateColorSpaceByColorSpace(x,x,x,x)
.text:77F033D2 mov ecx, [ebp+var_4]
.text:77F033D5 pop edi
.text:77F033D6 pop esi
.text:77F033D7 call __security_check_cookie(x)
.text:77F033DC leave
.text:77F033DD retn 10h
.text:77F033DD __stdcall IcmCreateColorSpaceByName(x, x, x, x) endp
本人菜鸟一只，请指教，谢谢。
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楼主能不能好心给传个paimei啊，下了一个多月了都是超时
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