IIS文件名解析漏洞扼要分析

时间 2020-07-27

标签 iis 文件名解析漏洞扼要分析繁體版

原文原文链接

归纳: 从技术角度分析IIS6文件名解析漏洞的原理与IIS7的相关状况。

a.IIS6错误解析文件类型现象

一、当WEB目录下，文件名以 xxx.asp;xxx.xxx 来进行命名的时候，此文件将送交asp.dll解析(也就是执行脚本)

二、当WEB目录下，在访问以 xxx.asp 命名的目录下的任意文件时，此文件将送交asp.dll解析(也就是执行脚本)

经过对IIS6的核心文件类型解析相关文件的逆向后，整理出下面的核心处理代码。app

 1 //reverse code by golds7n with ida
 2 int __thiscall Url(void *this, char *UrlStruct)  3 {  4   void *pW3_URL_INFO; // esi@1
 5   int bSuccess; // eax@1
 6   const wchar_t *i; // eax@2
 7   wchar_t *wcsSlashTemp; // ebx@6
 8   int wcsTemp; // eax@6
 9   int wcs_Exten; // eax@6
10   int v8; // esi@9
11   int v10; // eax@11
12   int v11; // ST04_4@13
13   int v12; // eax@13
14   int ExtenDll; // eax@19
15   int Extenisa; // eax@20
16   int ExtenExe; // eax@21
17   int ExtenCgi; // eax@22
18   int ExtenCom; // eax@23
19   int ExtenMap; // eax@24
20   int Entry; // [sp+Ch] [bp-148h]@6
21   wchar_t *wcsMaohaoTemp; // [sp+10h] [bp-144h]@6
22   unsigned int dotCount; // [sp+14h] [bp-140h]@1
23   wchar_t *Str; // [sp+18h] [bp-13Ch]@3
24   char *url_FileName; // [sp+1Ch] [bp-138h]@1
25   char Url_FileExtenName; // [sp+20h] [bp-134h]@1
26   char v25; // [sp+50h] [bp-104h]@1
27 
28  dotCount = 0; 29   pW3_URL_INFO = this; 30   STRU::STRU(&Url_FileExtenName, &v25, 0x100u); 31   url_FileName = (char *)pW3_URL_INFO + 228; 32   bSuccess = STRU::Copy((char *)pW3_URL_INFO + 228, UrlStruct); 33   if ( bSuccess < 0 ) 34     goto SubEnd; 35   for ( i = (const wchar_t *)STRU::QueryStr((char *)pW3_URL_INFO + 228); ; i = Str + 1 ) 36  { 37     Str = _wcschr(i, '.');   ***********N1************
38     if ( !Str ) 39       break; 40     ++dotCount; 41     if ( dotCount > W3_URL_INFO::sm_cMaxDots ) 42       break; 43     bSuccess = STRU::Copy(&Url_FileExtenName, Str); 44     if ( bSuccess < 0 ) 45       goto SubEnd; 46     wcsSlashTemp = _wcschr(Str, '/'); ***********N2************
47     JUMPOUT(wcsSlashTemp, 0, loc_5A63FD37); 48     wcsTemp = STRU::QueryStr(&Url_FileExtenName); 49     wcsMaohaoTemp = _wcschr((const wchar_t *)wcsTemp, ':');  ***********N3************
50     JUMPOUT(wcsMaohaoTemp, 0, loc_5A63FD51); 51     wcs_Exten = STRU::QueryStr(&Url_FileExtenName); 52     __wcslwr((wchar_t *)wcs_Exten); 53     if ( META_SCRIPT_MAP::FindEntry(&Url_FileExtenName, &Entry) ) 54  { 55       *((_DWORD *)pW3_URL_INFO + 201) = Entry; 56       JUMPOUT(wcsSlashTemp, 0, loc_5A63FDAD); 57       STRU::Reset((char *)pW3_URL_INFO + 404); 58       break; 59  } 60     if ( STRU::QueryCCH(&Url_FileExtenName) == 4 ) 61  { 62       ExtenDll = STRU::QueryStr(&Url_FileExtenName); 63       if ( !_wcscmp(L".dll", (const wchar_t *)ExtenDll) 64         || (Extenisa = STRU::QueryStr(&Url_FileExtenName), !_wcscmp(L".isa", (const wchar_t *)Extenisa)) ) 65  JUMPOUT(loc_5A63FD89); 66       ExtenExe = STRU::QueryStr(&Url_FileExtenName); 67       if ( !_wcscmp(L".exe", (const wchar_t *)ExtenExe) 68         || (ExtenCgi = STRU::QueryStr(&Url_FileExtenName), !_wcscmp(L".cgi", (const wchar_t *)ExtenCgi)) 69         || (ExtenCom = STRU::QueryStr(&Url_FileExtenName), !_wcscmp(L".com", (const wchar_t *)ExtenCom)) ) 70  JUMPOUT(loc_5A63FD89); 71       ExtenMap = STRU::QueryStr(&Url_FileExtenName); 72       JUMPOUT(_wcscmp(L".map", (const wchar_t *)ExtenMap), 0, loc_5A63FD7B); 73  } 74  } 75   if ( *((_DWORD *)pW3_URL_INFO + 201) 76     || (v10 = *((_DWORD *)pW3_URL_INFO + 202), v10 == 3) 77     || v10 == 2
78     || (v11 = *(_DWORD *)(*((_DWORD *)pW3_URL_INFO + 204) + 0xC4C), 79         v12 = STRU::QueryStr(url_FileName), 80         bSuccess = SelectMimeMappingForFileExt(v12, v11, (char *)pW3_URL_INFO + 756, (char *)pW3_URL_INFO + 1012), 81         bSuccess >= 0) ) 82     v8 = 0; 83   else
84 SubEnd: 85     v8 = bSuccess; 86   STRU::_STRU(&Url_FileExtenName); 87   return v8; 88 }

上述代码中，做星号标记的是N1,N2,N3，分别检测点号,反斜杠和分号。

大概流程为:

请求 /aaa.asp;xxxx.jpg

N1:从头部查找查找 "."号,得到 .asp;xxxx.jpg

N2:查找";"号,若是有则内存截断

N3:查找"/",若是有则内存截断

最终,将保留下来 .asp 字符串,从META_SCRIPT_MAP脚本映射表里与扩展名匹配对比,并反馈给了asp.dll处理this

b.IIS7是否延续了漏洞

IIS7的核心处理代码：url

 1 //reverse code by golds7n with ida
 2 const unsigned __int16 *__stdcall MatchPathInUrl(const unsigned __int16 *url_User, unsigned __int32 url_Length, const unsigned __int16 *IIS_MAP_Wizard)  3 {  4   const unsigned __int16 *p; // ebx@1
 5   const unsigned __int16 *pUrl; // ecx@4
 6   const wchar_t *i; // edi@6
 7   signed int isXingHao; // edx@8
 8   const unsigned __int16 cWizard; // ax@10
 9   const unsigned __int16 *pWizard; // esi@11
 10   int cTemp; // eax@17
 11   int pCharTemp; // esi@23
 12   const unsigned __int16 *pCharUser; // eax@43
 13   const unsigned __int16 byteChar; // cx@44
 14   const wchar_t cSlash; // ax@50
 15   const unsigned __int16 *Str2; // [sp+8h] [bp-8h]@11
 16   signed int bFound; // [sp+Ch] [bp-4h]@3
 17 
 18  p = IIS_MAP_Wizard;  19   if ( *IIS_MAP_Wizard != '*' || IIS_MAP_Wizard[1] )  20  {  21     bFound = 1;  22     if ( *IIS_MAP_Wizard == '/' )  23  {  24       p = IIS_MAP_Wizard + 1;  25       bFound = 0;  26       ++IIS_MAP_Wizard;  27  }  28     pUrl = url_User;  29     if ( *url_User == '/' )  30  {  31       pUrl = url_User + 1;  32       ++url_User;  33  }  34 LABEL_6:  35     for ( i = pUrl; ; i += pCharTemp )  36  {  37       while ( *p == '?' )  38  {  39         if ( !*i )  40           return 0;  41         if ( *i == '/' )  42           goto LABEL_30;  43         ++p;  44         ++i;  45  }  46       isXingHao = 0;  47       if ( *p == '*' )  48  {  49         ++p;  50         isXingHao = 1;  51  }  52       cWizard = *p;  53       if ( !*p )  54         break;  55       pWizard = p;  56       Str2 = p;  57       if ( cWizard != '*' )  58  {  59         do
 60  {  61           if ( cWizard == '?' )  62             break;  63           if ( !cWizard )  64             break;  65           ++pWizard;  66           cWizard = *pWizard;  67           Str2 = pWizard;  68  }  69         while ( *pWizard != '*' );  70  }  71       if ( isXingHao )  72  {  73         if ( !*pWizard )  74  {  75           cTemp = (int)&i[pWizard - p];  76           if ( cTemp > (unsigned int)&pUrl[url_Length] )  77             return 0;  78           while ( *(_WORD *)cTemp != '/' && *(_WORD *)cTemp && *i != '/' && *i )  79  {  80             ++i;  81             cTemp += 2;  82  }  83  }  84         pCharTemp = pWizard - p;  85         while ( _wcsncmp(i, p, pCharTemp) )  86  {  87           if ( !*i )  88             return 0;  89           if ( *i == '/' )  90             goto LABEL_29;  91           ++i;  92  }  93  }  94       else
 95  {  96         pCharTemp = pWizard - p;  97         if ( _wcsncmp(i, p, pCharTemp) )  98  {  99 LABEL_29: 100           pUrl = url_User; 101 LABEL_30: 102           if ( !bFound ) 103             return 0; 104           while ( *pUrl != '/' ) 105  { 106             if ( !*pUrl ) 107               return 0; 108             ++pUrl; 109  } 110           if ( !*pUrl ) 111             return 0; 112           p = IIS_MAP_Wizard; 113           ++pUrl; 114           url_User = pUrl; 115           goto LABEL_6; 116  } 117  } 118       p = Str2; 119       pUrl = url_User; 120  } 121     if ( isXingHao ) 122  { 123       cSlash = *i; 124       if ( *i == '/' ) 125         return i; 126       do
127  { 128         if ( !cSlash ) 129           break; 130         ++i; 131         cSlash = *i; 132  } 133       while ( *i != '/' ); 134  } 135     if ( *i != '/' && *i ) 136       goto LABEL_30; 137     return i; 138  } 139   pCharUser = url_User; 140   do
141  { 142     byteChar = *pCharUser; 143     ++pCharUser; 144  } 145   while ( byteChar ); 146   return &url_User[pCharUser - (url_User + 1)]; 147 } 148 MatchPathInUrl(const unsigned __int16 *url_User, unsigned __int32 url_Length, const unsigned __int16 *IIS_MAP_Wizard)

参数url_User是用户提交的路径参数,相似PHOST/DEFAULT WEB SITE/aa.asp;xxx.jpg,由服务/站点名称/请求路径构成,IIS_MAP_Wizard是在管理器文件映射里的每一个表项,譬如*.ASP

比较的结果就是,拿aa.asp;xxx.jpg与*.ASP进行匹配,显然结果是不匹配的(/xxx.asp/xxx.jpg,是拿xxx.jpg和*.ASP进行匹配)spa

c.总结

IIS6文件映射配置图设计

IIS7文件映射配置图code

从上面的关键分析和图中，能够看出，IIS6存在解析漏洞是因为其设计上的问题致使,IIS6只简单地根据扩展名来识别,而IIS7是进行通配符匹配来定夺请求文件是不是某脚本类型,可见IIS7纠正了错误机制,更加科学、健壮。blog