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Windows Impersonation using C#

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29 Apr 2003CPOL 720.4K   15.6K   149   74
An article demonstrating how to use Windows impersonation in your C# code

Impersonation

Introduction

I've been a member of the CodeProject for over 3 years now, and still haven't contributed any articles - until now.

While designing a Windows Forms-based application, to administrate containers in our Active Directory, I needed a way to allow binding to the AD using alternate credentials. Windows impersonation was the answer. This sample app demonstrates how to use unmanaged code by calling LogonUser() contained within the advapi32.dll, and pass a token handle back to your .NET application using WindowsImpersonationContext.

One of the downfalls to the LogonUser()function is that the password get passed in clear-text.

Partial Source Code

C#
using System.Runtime.InteropServices; // DllImport
using System.Security.Principal; // WindowsImpersonationContext
using System.Security.Permissions; // PermissionSetAttribute
...

public WindowsImpersonationContext 
    ImpersonateUser(string sUsername, string sDomain, string sPassword)
{
    // initialize tokens
    IntPtr pExistingTokenHandle = new IntPtr(0);
    IntPtr pDuplicateTokenHandle = new IntPtr(0);
    pExistingTokenHandle = IntPtr.Zero;
    pDuplicateTokenHandle = IntPtr.Zero;
    
    // if domain name was blank, assume local machine
    if (sDomain == "")
        sDomain = System.Environment.MachineName;

    try
    {
        string sResult = null;

        const int LOGON32_PROVIDER_DEFAULT = 0;

        // create token
        const int LOGON32_LOGON_INTERACTIVE = 2;
        //const int SecurityImpersonation = 2;

        // get handle to token
        bool bImpersonated = LogonUser(sUsername, sDomain, sPassword, 
            LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, 
                ref pExistingTokenHandle);

        // did impersonation fail?
        if (false == bImpersonated)
        {
            int nErrorCode = Marshal.GetLastWin32Error();
            sResult = "LogonUser() failed with error code: " + 
                nErrorCode + "\r\n";

            // show the reason why LogonUser failed
            MessageBox.Show(this, sResult, "Error", 
                MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

        // Get identity before impersonation
        sResult += "Before impersonation: " + 
            WindowsIdentity.GetCurrent().Name + "\r\n";

        bool bRetVal = DuplicateToken(pExistingTokenHandle, 
            (int)SECURITY_IMPERSONATION_LEVEL.SecurityImpersonation, 
                ref pDuplicateTokenHandle);

        // did DuplicateToken fail?
        if (false == bRetVal)
        {
            int nErrorCode = Marshal.GetLastWin32Error();
            // close existing handle
            CloseHandle(pExistingTokenHandle); 
            sResult += "DuplicateToken() failed with error code: " 
                + nErrorCode + "\r\n";

            // show the reason why DuplicateToken failed
            MessageBox.Show(this, sResult, "Error", 
                MessageBoxButtons.OK, MessageBoxIcon.Error);
            return null;
        }
        else
        {
            // create new identity using new primary token
            WindowsIdentity newId = new WindowsIdentity
                                        (pDuplicateTokenHandle);
            WindowsImpersonationContext impersonatedUser = 
                                        newId.Impersonate();

            // check the identity after impersonation
            sResult += "After impersonation: " + 
                WindowsIdentity.GetCurrent().Name + "\r\n";
            
            MessageBox.Show(this, sResult, "Success", 
                MessageBoxButtons.OK, MessageBoxIcon.Information);
            return impersonatedUser;
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        // close handle(s)
        if (pExistingTokenHandle != IntPtr.Zero)
            CloseHandle(pExistingTokenHandle);
        if (pDuplicateTokenHandle != IntPtr.Zero) 
            CloseHandle(pDuplicateTokenHandle);
    }
}

Points of Interest

This code won't work on Windows 98 or ME because they do not utilize user tokens. Code was built and run using Visual Studio.NET 2002 on Windows XP Service Pack 1.

One of the other uses for this code I've found is, for instantiating COM components that must run in an alternate security context to that of the logged-on user.

If anyone has a more secure method of achieving the same thing, please let me know.

History

  • Version 1.0 - 04.25.03 - First release version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Zambia Zambia
Living abroad and loving life.

Comments and Discussions

 
GeneralRe: Windows 2008 server Pin
omar_chavez1-Dec-15 15:08
omar_chavez1-Dec-15 15:08 
GeneralThis process not working with a WPF application!!! Pin
Arshad Kunnath31-Jul-08 1:36
Arshad Kunnath31-Jul-08 1:36 
GeneralRe: This process not working with a WPF application!!! Pin
Christian Merritt31-Jul-08 2:59
Christian Merritt31-Jul-08 2:59 
GeneralRe: This process not working with a WPF application!!! Pin
Matei Focseneanu12-May-10 5:15
Matei Focseneanu12-May-10 5:15 
GeneralRe: This process not working with a WPF application!!! Pin
Jason Jakob20-Jun-13 5:09
Jason Jakob20-Jun-13 5:09 
QuestionIt may be.... Pin
WillianBR15-May-08 8:55
WillianBR15-May-08 8:55 
GeneralWindows CE .net Pin
questions_c1-Oct-07 2:28
questions_c1-Oct-07 2:28 
GeneralRe: Windows CE .net Pin
Christian Merritt1-Oct-07 15:18
Christian Merritt1-Oct-07 15:18 
GeneralRe: Windows CE .net Pin
Pram_Singh4120-Jul-09 4:22
Pram_Singh4120-Jul-09 4:22 
GeneralError Code 1326 [modified] Pin
collapo21-Aug-07 0:56
collapo21-Aug-07 0:56 
GeneralRe: Error Code 1326 Pin
mirh10-Oct-07 1:59
mirh10-Oct-07 1:59 
GeneralRe: Error Code 1326 Pin
mustiy9-Feb-10 23:17
mustiy9-Feb-10 23:17 
GeneralError 1314 Pin
m.aldegheri3-Aug-06 6:28
m.aldegheri3-Aug-06 6:28 
GeneralRe: Error 1314 Pin
m.aldegheri3-Aug-06 22:23
m.aldegheri3-Aug-06 22:23 
GeneralRe: Error 1314 Pin
MunkieFish11-Apr-07 7:49
MunkieFish11-Apr-07 7:49 
AnswerRe: Error 1314 Pin
uppals12-Apr-07 13:06
uppals12-Apr-07 13:06 
GeneralHelp needed Windows 2000 SP4 still getting 1314! -- Re: Error 1314 Pin
devvvy21-Feb-08 20:41
devvvy21-Feb-08 20:41 
GeneralRe: Help needed Windows 2000 SP4 still getting 1314! -- Re: Error 1314 Pin
Christian Merritt26-Feb-08 3:02
Christian Merritt26-Feb-08 3:02 
Questionhow to use this in case of a local account? Pin
yossof elnaggar27-Jun-06 20:29
yossof elnaggar27-Jun-06 20:29 
AnswerRe: how to use this in case of a local account? Pin
Harkamal Singh12-Jul-07 19:04
Harkamal Singh12-Jul-07 19:04 
GeneralRe: how to use this in case of a local account? Pin
appalanaidu Aug20118-Feb-12 20:54
appalanaidu Aug20118-Feb-12 20:54 
GeneralFirst call takes too long Pin
schweeneh4-Apr-06 6:04
schweeneh4-Apr-06 6:04 
GeneralRe: First call takes too long Pin
Christian Merritt12-Jun-06 2:24
Christian Merritt12-Jun-06 2:24 
GeneralA similar article Pin
Uwe Keim23-Apr-05 23:59
sitebuilderUwe Keim23-Apr-05 23:59 
GeneralRe: A similar article Pin
craigg753-Nov-06 5:57
craigg753-Nov-06 5:57 

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