How to "un-impersonate" (un-delegate?) in Kerberos

Question

I have a web application using Kerberos to access an external resource useing ASP.NET 3.5 and IIS.

When a user connects with the application, Kerberos authentication auto-magically allows me to connect to external resources acting as the user using delegation. This was not easy to do. It is nice, but I've a problem. Sometimes I need to connect to an external resource using an account with more rights than the user. The service account which the app-pool is running under has the addition rights I need. How can I remove the user's Kerberos identification and connect with Kerberos using the service account running the application pool?

UPDATE

I'm not sure why I am getting no responses at all. I've never seen that before. Please post questions, they may clarify the problem (to me too).

Answer 1

I have a class:

public class ProcessIdentityScope : IDisposable
{
    private System.Security.Principal.WindowsImpersonationContext _impersonationContext;
    private bool _disposed;

    public ProcessIdentityScope()
    {
        _impersonationContext = System.Security.Principal.WindowsIdentity.Impersonate(IntPtr.Zero);
    }

    #region IDisposable Members

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!_disposed)
        {
            _impersonationContext.Undo();
            _impersonationContext.Dispose();
            _disposed = true;
        }
        else
            throw new ObjectDisposedException("ProcessIdentityScope");
    }

    #endregion
}

And I use it like so:

using(ProcessIdentityScope identityScope = new ProcessIdentityScope())
{
    // Any code in here runs under the Process Identity.
}

This code is based on this MSDN article: http://msdn.microsoft.com/en-us/library/ms998351.aspx