C# Signature:
[DllImport("advapi32.dll", SetLastError=true)]
static extern bool OpenThreadToken(
IntPtr ThreadHandle,
uint DesiredAccess,
bool OpenAsSelf,
out IntPtr TokenHandle);
VB Signature:
Declare Function OpenThreadToken Lib "advapi32.dll" (
ThreadHandle As IntPtr,
DesiredAccess As Integer,
OpenAsSelf As Boolean,
ByRef TokenHandle As IntPtr) As Boolean
User-Defined Types:
None.
Notes:
None.
Tips & Tricks:
Please add some!
Sample Code:
/// <summary>
/// HoldImpersonationCloak enables temporarily dropping the 'cloak' of
/// impersonation to access items as the process identity, so hiding another
/// account/password pair is not required. Useful in double-hop
/// situations where the process ID can be safely used for remote access.
/// </summary>
/// <example>
/// using (HoldImpersonationCloak hic = new HoldImpersonationCloak())
/// {
/// //operate here as process identity
/// GC.KeepAlive(hic); //prevent over-eager garbage collection optimization from taking it too soon
/// }
/// </example>
public class HoldImpersonationCloak : IDisposable
{
#region Constants
//Some declarations and code taken from http://support.microsoft.com/kb/306158/,
// http://pluralsight.com/wiki/default.aspx/Keith.GuideBook/HowToImpersonateAUserGivenHerToken.html,
// http://pluralsight.com/wiki/default.aspx/Keith.GuideBook/HowToCreateAWindowsPrincipalGivenAToken.html,
// http://www.pinvoke.net
private const int TOKEN_READ = 0x00020008; //From VC\PlatformSDK\Include\Winnt.h
private const int TOKEN_IMPERSONATE = 0x0004;
private const int ERROR_NO_TOKEN = 1008; //From VC\PlatformSDK\Include\WinError.h
#endregion
#region External Declarations
[System.Runtime.InteropServices.DllImport("kernel32.dll", SetLastError = true)]
private static extern IntPtr GetCurrentThread();
[System.Runtime.InteropServices.DllImport("advapi32.dll", SetLastError = true)]
private static extern bool OpenThreadToken(IntPtr ThreadHandle,
uint DesiredAccess,
bool OpenAsSelf,
out IntPtr TokenHandle);
[System.Runtime.InteropServices.DllImport("advapi32.dll", SetLastError = true)]
private static extern bool SetThreadToken(IntPtr pHandle,
IntPtr hToken);
[System.Runtime.InteropServices.DllImport("advapi32.dll", SetLastError = true)]
private static extern bool RevertToSelf();
[System.Runtime.InteropServices.DllImport("kernel32.dll", SetLastError = true)]
private static extern bool CloseHandle(IntPtr handle);
#endregion
#region Variables
private IntPtr hToken = IntPtr.Zero;
private int dw;
#endregion
public HoldImpersonationCloak()
{
if (!OpenThreadToken(GetCurrentThread(), TOKEN_READ | TOKEN_IMPERSONATE, true, out hToken))
{
dw = System.Runtime.InteropServices.Marshal.GetLastWin32Error();
if (ERROR_NO_TOKEN == dw) //
{
System.Diagnostics.Trace.WriteLine("Not impersonating, cloak is a no-op!", "Impersonation");
}
else
{
System.Diagnostics.Trace.WriteLine("Unexpected error 0x" + dw.ToString("x4") + " on OpenThreadToken", "Impersonation");
}
hToken = IntPtr.Zero;
}
else
{
if (!RevertToSelf())
{
dw = System.Runtime.InteropServices.Marshal.GetLastWin32Error();
System.Diagnostics.Trace.WriteLine("Failed to revert!, error 0x" + dw.ToString("x4"), "Impersonation");
}
}
}
//Implement IDisposable. (from Implementing Finalize and Dispose to Clean Up Unmanaged Resources )
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (disposing)
{
// Free other state (managed objects).
if (IntPtr.Zero != hToken)
{
if (!SetThreadToken(IntPtr.Zero, hToken))
{
dw = System.Runtime.InteropServices.Marshal.GetLastWin32Error();
System.Diagnostics.Trace.WriteLine("Could not reset cloak!, error 0x" + dw.ToString("x4"), "Impersonation");
}
}
}
// Free your own state (unmanaged objects).
if (IntPtr.Zero != hToken)
{
if (!CloseHandle(hToken))
{
dw = System.Runtime.InteropServices.Marshal.GetLastWin32Error();
System.Diagnostics.Trace.WriteLine("Could not close cloak token!, error 0x" + dw.ToString("x4"), "Impersonation"); ;
}
hToken = IntPtr.Zero;
}
// Set large fields to null.
}
// Use C# destructor syntax for finalization code.
~HoldImpersonationCloak()
{
// Simply call Dispose(false).
Dispose (false);
}
}
Alternative Managed API:
Do you know one? Please contribute it!
