Impersonation code in C#
While investigating a customer issue, I needed code to impersonate a different user on the current thread. A quick search of the msdn blogs turned up this post, which got me most of the way there. I decided to wrap the code into a class that inherits from IDisposable just to make it easily usable in a using statement. Here is what I came up with (note that it is not thread safe):
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Security.Principal;
public class ImpersonatedUser : IDisposable
{
IntPtr userHandle;
WindowsImpersonationContext impersonationContext;
public ImpersonatedUser(string user, string domain, string password)
{
userHandle = IntPtr.Zero;
bool loggedOn = LogonUser(
user,
domain,
password,
LogonType.Interactive,
LogonProvider.Default,
out userHandle);
if (!loggedOn)
throw new Win32Exception(Marshal.GetLastWin32Error());
// Begin impersonating the user
impersonationContext = WindowsIdentity.Impersonate(userHandle);
}
public void Dispose()
{
if (userHandle != IntPtr.Zero)
{
CloseHandle(userHandle);
userHandle = IntPtr.Zero;
impersonationContext.Undo();
}
}
[DllImport("advapi32.dll", SetLastError = true)]
static extern bool LogonUser(
string lpszUsername,
string lpszDomain,
string lpszPassword,
LogonType dwLogonType,
LogonProvider dwLogonProvider,
out IntPtr phToken
);
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool CloseHandle(IntPtr hHandle);
enum LogonType : int
{
Interactive = 2,
Network = 3,
Batch = 4,
Service = 5,
NetworkCleartext = 8,
NewCredentials = 9,
}
enum LogonProvider : int
{
Default = 0,
}
}
