Impersonating CurrentUser from SYSTEM

Hey all,

I've been searching for a very long time an easy way to impersonate current user while running in a "SYSTEM" user credentials.
I haven't found any code that does it and actually works.
So I managed to combine pieces of code from several places, and added some of my own.
This helper class exposes 2 functions:
1. Get current user impersonated scope - in this scope you can do pretty much whatever you want in the current user credentials.
2. Start a process as current user.

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public static class ImpersonationUtils {     private const int SW_SHOW = 5;     private const int TOKEN_QUERY = 0x0008;     private const int TOKEN_DUPLICATE = 0x0002;     private const int TOKEN_ASSIGN_PRIMARY = 0x0001;     private const int STARTF_USESHOWWINDOW = 0x00000001;     private const int STARTF_FORCEONFEEDBACK = 0x00000040;     private const int CREATE_UNICODE_ENVIRONMENT = 0x00000400;     private const int TOKEN_IMPERSONATE = 0x0004;     private const int TOKEN_QUERY_SOURCE = 0x0010;     private const int TOKEN_ADJUST_PRIVILEGES = 0x0020;     private const int TOKEN_ADJUST_GROUPS = 0x0040;     private const int TOKEN_ADJUST_DEFAULT = 0x0080;     private const int TOKEN_ADJUST_SESSIONID = 0x0100;     private const int STANDARD_RIGHTS_REQUIRED = 0x000F0000;     private const int TOKEN_ALL_ACCESS =         STANDARD_RIGHTS_REQUIRED |         TOKEN_ASSIGN_PRIMARY |         TOKEN_DUPLICATE |         TOKEN_IMPERSONATE |         TOKEN_QUERY |         TOKEN_QUERY_SOURCE |         TOKEN_ADJUST_PRIVILEGES |         TOKEN_ADJUST_GROUPS |         TOKEN_ADJUST_DEFAULT |         TOKEN_ADJUST_SESSIONID;       [StructLayout(LayoutKind.Sequential)]     private struct PROCESS_INFORMATION     {         public IntPtr hProcess;         public IntPtr hThread;         public int dwProcessId;         public int dwThreadId;     }       [StructLayout(LayoutKind.Sequential)]     private struct SECURITY_ATTRIBUTES     {         public int nLength;         public IntPtr lpSecurityDescriptor;         public bool bInheritHandle;     }       [StructLayout(LayoutKind.Sequential)]     private struct STARTUPINFO     {         public int cb;         public string lpReserved;         public string lpDesktop;         public string lpTitle;         public int dwX;         public int dwY;         public int dwXSize;         public int dwYSize;         public int dwXCountChars;         public int dwYCountChars;         public int dwFillAttribute;         public int dwFlags;         public short wShowWindow;         public short cbReserved2;         public IntPtr lpReserved2;         public IntPtr hStdInput;         public IntPtr hStdOutput;         public IntPtr hStdError;     }       private enum SECURITY_IMPERSONATION_LEVEL     {         SecurityAnonymous,         SecurityIdentification,         SecurityImpersonation,         SecurityDelegation     }       private enum TOKEN_TYPE     {         TokenPrimary = 1,         TokenImpersonation     }       [DllImport("advapi32.dll", SetLastError = true)]     private static extern bool CreateProcessAsUser(         IntPtr hToken,         string lpApplicationName,         string lpCommandLine,         ref SECURITY_ATTRIBUTES lpProcessAttributes,         ref SECURITY_ATTRIBUTES lpThreadAttributes,         bool bInheritHandles,         int dwCreationFlags,         IntPtr lpEnvironment,         string lpCurrentDirectory,         ref STARTUPINFO lpStartupInfo,         out PROCESS_INFORMATION lpProcessInformation);       [DllImport("advapi32.dll", SetLastError = true)]     private static extern bool DuplicateTokenEx(         IntPtr hExistingToken,         int dwDesiredAccess,         ref SECURITY_ATTRIBUTES lpThreadAttributes,         int ImpersonationLevel,         int dwTokenType,         ref IntPtr phNewToken);       [DllImport("advapi32.dll", SetLastError = true)]     private static extern bool OpenProcessToken(         IntPtr ProcessHandle,         int DesiredAccess,         ref IntPtr TokenHandle);       [DllImport("userenv.dll", SetLastError = true)]     private static extern bool CreateEnvironmentBlock(             ref IntPtr lpEnvironment,             IntPtr hToken,             bool bInherit);       [DllImport("userenv.dll", SetLastError = true)]     private static extern bool DestroyEnvironmentBlock(             IntPtr lpEnvironment);       [DllImport("kernel32.dll", SetLastError = true)]     private static extern bool CloseHandle(         IntPtr hObject);       private static void LaunchProcessAsUser(string cmdLine, IntPtr token, IntPtr envBlock, int sessionId)     {         var pi = new PROCESS_INFORMATION();         var saProcess = new SECURITY_ATTRIBUTES();         var saThread = new SECURITY_ATTRIBUTES();         saProcess.nLength = Marshal.SizeOf(saProcess);         saThread.nLength = Marshal.SizeOf(saThread);           var si = new STARTUPINFO();         si.cb = Marshal.SizeOf(si);         si.lpDesktop = @"WinSta0\Default";         si.dwFlags = STARTF_USESHOWWINDOW | STARTF_FORCEONFEEDBACK;         si.wShowWindow = SW_SHOW;           if (!CreateProcessAsUser(             token,             null,             cmdLine,             ref saProcess,             ref saThread,             false,             CREATE_UNICODE_ENVIRONMENT,             envBlock,             null,             ref si,             out pi))         {             throw new Win32Exception(Marshal.GetLastWin32Error(), "CreateProcessAsUser failed");         }     }       private static IDisposable Impersonate(IntPtr token)     {         var identity = new WindowsIdentity(token);         return identity.Impersonate();     }       private static IntPtr GetPrimaryToken(Process process)     {         var token = IntPtr.Zero;         var primaryToken = IntPtr.Zero;           if (OpenProcessToken(process.Handle, TOKEN_DUPLICATE, ref token))         {             var sa = new SECURITY_ATTRIBUTES();             sa.nLength = Marshal.SizeOf(sa);               if (!DuplicateTokenEx(                 token,                 TOKEN_ALL_ACCESS,                 ref sa,                 (int)SECURITY_IMPERSONATION_LEVEL.SecurityImpersonation,                 (int)TOKEN_TYPE.TokenPrimary,                 ref primaryToken))             {                 throw new Win32Exception(Marshal.GetLastWin32Error(), "DuplicateTokenEx failed");             }               CloseHandle(token);         }         else         {             throw new Win32Exception(Marshal.GetLastWin32Error(), "OpenProcessToken failed");         }           return primaryToken;     }       private static IntPtr GetEnvironmentBlock(IntPtr token)     {         var envBlock = IntPtr.Zero;         if (!CreateEnvironmentBlock(ref envBlock, token, false))         {             throw new Win32Exception(Marshal.GetLastWin32Error(), "CreateEnvironmentBlock failed");         }         return envBlock;     }       public static void LaunchAsCurrentUser(string cmdLine)     {         var process = Process.GetProcessesByName("explorer").FirstOrDefault();         if (process != null)         {             var token = GetPrimaryToken(process);             if (token != IntPtr.Zero)             {                 var envBlock = GetEnvironmentBlock(token);                 if (envBlock != IntPtr.Zero)                 {                     LaunchProcessAsUser(cmdLine, token, envBlock, process.SessionId);                     if (!DestroyEnvironmentBlock(envBlock))                     {                         throw new Win32Exception(Marshal.GetLastWin32Error(), "DestroyEnvironmentBlock failed");                     }                 }                   CloseHandle(token);             }         }     }       public static IDisposable ImpersonateCurrentUser()     {         var process = Process.GetProcessesByName("explorer").FirstOrDefault();         if (process != null)         {             var token = GetPrimaryToken(process);             if (token != IntPtr.Zero)             {                 return Impersonate(token);             }         }           throw new Exception("Could not find explorer.exe");     } }

And the usage is very easy:

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ImpersonationUtils.LaunchAsCurrentUser("notepad");   using (ImpersonationUtils.ImpersonateCurrentUser()) {       }

It's easy and it's fun!
I really hope this code will save you the hours I spend on writing it.