Question

I am using the code to impersonate a user account to get access to a file share.

public class Impersonator :
    IDisposable
{
    #region Public methods.
    // ------------------------------------------------------------------

    /// <summary>
    /// Constructor. Starts the impersonation with the given credentials.
    /// Please note that the account that instantiates the Impersonator class
    /// needs to have the 'Act as part of operating system' privilege set.
    /// </summary>
    /// <param name="userName">The name of the user to act as.</param>
    /// <param name="domainName">The domain name of the user to act as.</param>
    /// <param name="password">The password of the user to act as.</param>
    public Impersonator(
        string userName,
        string domainName,
        string password )
    {
        ImpersonateValidUser( userName, domainName, password );
    }

    // ------------------------------------------------------------------
    #endregion

    #region IDisposable member.
    // ------------------------------------------------------------------

    public void Dispose()
    {
        UndoImpersonation();
    }

    // ------------------------------------------------------------------
    #endregion

    #region P/Invoke.
    // ------------------------------------------------------------------

    [DllImport("advapi32.dll", SetLastError=true)]
    private static extern int LogonUser(
        string lpszUserName,
        string lpszDomain,
        string lpszPassword,
        int dwLogonType,
        int dwLogonProvider,
        ref IntPtr phToken);

    [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
    private static extern int DuplicateToken(
        IntPtr hToken,
        int impersonationLevel,
        ref IntPtr hNewToken);

    [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
    private static extern bool RevertToSelf();

    [DllImport("kernel32.dll", CharSet=CharSet.Auto)]
    private static extern  bool CloseHandle(
        IntPtr handle);

    private const int LOGON32_LOGON_INTERACTIVE = 2;
    private const int LOGON32_PROVIDER_DEFAULT = 0;

    // ------------------------------------------------------------------
    #endregion

    #region Private member.
    // ------------------------------------------------------------------

    /// <summary>
    /// Does the actual impersonation.
    /// </summary>
    /// <param name="userName">The name of the user to act as.</param>
    /// <param name="domainName">The domain name of the user to act as.</param>
    /// <param name="password">The password of the user to act as.</param>
    private void ImpersonateValidUser(
        string userName, 
        string domain, 
        string password )
    {
        WindowsIdentity tempWindowsIdentity = null;
        IntPtr token = IntPtr.Zero;
        IntPtr tokenDuplicate = IntPtr.Zero;

        try
        {
            if ( RevertToSelf() )
            {
                if ( LogonUser(
                    userName, 
                    domain, 
                    password, 
                    LOGON32_LOGON_INTERACTIVE,
                    LOGON32_PROVIDER_DEFAULT, 
                    ref token ) != 0 )
                {
                    if ( DuplicateToken( token, 2, ref tokenDuplicate ) != 0 )
                    {
                        tempWindowsIdentity = new WindowsIdentity( tokenDuplicate );
                        impersonationContext = tempWindowsIdentity.Impersonate();
                    }
                    else
                    {
                        throw new Win32Exception( Marshal.GetLastWin32Error() );
                    }
                }
                else
                {
                    throw new Win32Exception( Marshal.GetLastWin32Error() );
                }
            }
            else
            {
                throw new Win32Exception( Marshal.GetLastWin32Error() );
            }
        }
        finally
        {
            if ( token!= IntPtr.Zero )
            {
                CloseHandle( token );
            }
            if ( tokenDuplicate!=IntPtr.Zero )
            {
                CloseHandle( tokenDuplicate );
            }
        }
    }

    /// <summary>
    /// Reverts the impersonation.
    /// </summary>
    private void UndoImpersonation()
    {
        if ( impersonationContext!=null )
        {
            impersonationContext.Undo();
        }   
    }

    private WindowsImpersonationContext impersonationContext = null;

    // ------------------------------------------------------------------
    #endregion
}

Then using:

using (new Impersonator("username", "domain", "password"))
        {
            Process.Start("explorer.exe", @"/root,\\server01-Prod\abc");
        }

I get an “Access Denied” error.

This user supposely has access to this share. I can map a drive, use “net use” but this code will not work. Now I am thinking it is the code. Does anyone see anything? Is there a better way of doing this?

Answer 1

try this :

[DllImport("advapi32.dll", SetLastError = true)]
    public static extern bool LogonUser(
            string lpszUsername,
            string lpszDomain,
            string lpszPassword,
            int dwLogonType,
            int dwLogonProvider,
            out IntPtr phToken);

Usage :

IntPtr userToken = IntPtr.Zero;

bool success = External.LogonUser(
  "john.doe", 
  "domain.com", 
  "MyPassword", 
  (int) AdvApi32Utility.LogonType.LOGON32_LOGON_INTERACTIVE, //2
  (int) AdvApi32Utility.LogonProvider.LOGON32_PROVIDER_DEFAULT, //0
  out userToken);

if (!success)
{
  throw new SecurityException("Logon user failed");
}

using (WindowsIdentity.Impersonate(userToken))
{
 Process.Start("explorer.exe", @"/root,\\server01-Prod\abc");
}