RunProcessAsUser causing problems - windows

Question

I have an application that is being started by a Service automatically when the user logs on to his account. The application in question is a Winforms application and the problem is that sometimes when the application is started from the service it inexplicably hangs. Killing it and running it once more without a service works fine.
I am not sure why this is happening and why it only happens occasionally (not all the time). I always check the new process information and it is always running under the correct session of the logged in user.
I am not sure if I am doing something wrong when impersonating the user but in any case I am listing the code just so that maybe someone can find a flaw in it:
public int RunWithTokenInSession(IntPtr token, int nSessionID)
{
IntPtr primaryToken = GetUserTokenOfSessoin((uint)nSessionID);
if (primaryToken == IntPtr.Zero)
{
return -1;
}
STARTUPINFO StartupInfo = new STARTUPINFO();
processInfo_ = new PROCESS_INFORMATION();
StartupInfo.cb = Marshal.SizeOf(StartupInfo);
//StartupInfo.wShowWindow = (short)ShowCommands.SW_HIDE;
StartupInfo.lpDesktop = "Winsta0\\Default";
SECURITY_ATTRIBUTES Security1 = new SECURITY_ATTRIBUTES();
SECURITY_ATTRIBUTES Security2 = new SECURITY_ATTRIBUTES();
string command = "\"" + processPath_ + "\"";
if ((arguments_ != null) && (arguments_.Length != 0))
{
command += " " + arguments_;
}
IntPtr lpEnvironment = IntPtr.Zero;
bool resultEnv = CreateEnvironmentBlock(out lpEnvironment, primaryToken, false);
if (resultEnv != true)
{
int nError = GetLastError();
}
bool b = CreateProcessAsUser(primaryToken, null, command, ref Security1, ref Security2, false, /*CREATE_NO_WINDOW | NORMAL_PRIORITY_CLASS |*/ CREATE_UNICODE_ENVIRONMENT | DETACHED_PROCESS, lpEnvironment, null, ref StartupInfo, out processInfo_);
int error = 0;
if (!b)
{
error = Marshal.GetLastWin32Error();
string message = String.Format("CreateProcessAsUser Error: {0}", error);
Debug.WriteLine(message);
}
DestroyEnvironmentBlock(lpEnvironment);
CloseHandle(primaryToken);
return error;
}
And this is the code for GetUserTokenOfSessoin:
public static IntPtr GetUserTokenOfSessoin(uint dwSessionId)
{
IntPtr currentToken = IntPtr.Zero;
IntPtr primaryToken = IntPtr.Zero;
IntPtr WTS_CURRENT_SERVER_HANDLE = IntPtr.Zero;
IntPtr hUserToken = IntPtr.Zero;
IntPtr hTokenDup = IntPtr.Zero;
bool bRet = WTSQueryUserToken(dwSessionId, out currentToken);
if (bRet == false)
{
int n = GetLastError();
return IntPtr.Zero;
}
bool fInAdminGroup = false;
//IntPtr hToken = IntPtr.Zero;
IntPtr hTokenToCheck = IntPtr.Zero;
IntPtr pElevationType = IntPtr.Zero;
IntPtr pLinkedToken = IntPtr.Zero;
int cbSize = 0;
if (Environment.OSVersion.Version.Major >= 6)
{
// Running Windows Vista or later (major version >= 6).
// Determine token type: limited, elevated, or default.
// Allocate a buffer for the elevation type information.
cbSize = sizeof(TOKEN_ELEVATION_TYPE);
pElevationType = Marshal.AllocHGlobal(cbSize);
if (pElevationType == IntPtr.Zero)
{
throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
}
// Retrieve token elevation type information.
if (!GetTokenInformation(currentToken,
TOKEN_INFORMATION_CLASS.TokenElevationType, pElevationType, cbSize, out cbSize))
{
throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
}
// Marshal the TOKEN_ELEVATION_TYPE enum from native to .NET.
TOKEN_ELEVATION_TYPE elevType = (TOKEN_ELEVATION_TYPE)Marshal.ReadInt32(pElevationType);
// If limited, get the linked elevated token for further check.
if (elevType == TOKEN_ELEVATION_TYPE.TokenElevationTypeLimited)
{
// Allocate a buffer for the linked token.
cbSize = IntPtr.Size;
pLinkedToken = Marshal.AllocHGlobal(cbSize);
if (pLinkedToken == IntPtr.Zero)
{
throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
}
// Get the linked token.
if (!GetTokenInformation(currentToken, TOKEN_INFORMATION_CLASS.TokenLinkedToken, pLinkedToken, cbSize, out cbSize))
{
throw new System.ComponentModel.Win32Exception(Marshal.GetLastWin32Error());
}
// Marshal the linked token value from native to .NET.
hTokenToCheck = Marshal.ReadIntPtr(pLinkedToken);
bRet = DuplicateTokenEx(hTokenToCheck, TOKEN_ASSIGN_PRIMARY | TOKEN_ALL_ACCESS, IntPtr.Zero, SECURITY_IMPERSONATION_LEVEL.SecurityImpersonation, TOKEN_TYPE.TokenPrimary, out primaryToken);
}
else
{
bRet = DuplicateTokenEx(currentToken, TOKEN_ASSIGN_PRIMARY | TOKEN_ALL_ACCESS, IntPtr.Zero, SECURITY_IMPERSONATION_LEVEL.SecurityImpersonation, TOKEN_TYPE.TokenPrimary, out primaryToken);
}
}
else
{
// XP
bRet = DuplicateTokenEx(currentToken, TOKEN_ASSIGN_PRIMARY | TOKEN_ALL_ACCESS, IntPtr.Zero, SECURITY_IMPERSONATION_LEVEL.SecurityImpersonation, TOKEN_TYPE.TokenPrimary, out primaryToken);
}
if (bRet == false)
{
int lastError = Marshal.GetLastWin32Error();
return IntPtr.Zero;
}
return primaryToken;
}
Now the issue seems to exclusively happen on Windows Server 2008 R2 as I haven't been able to reproduce it on any other version of Windows so I was wondering if there is anything special about Server 2008 and do I need to take extra security measures or obtain an extra privilege to run the process as the user.