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Windows Impersonation using C#

, 29 Apr 2003
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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

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)

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About the Author

Marc Merritt
Architect
United States United States
I live in southeastern Pennsylvania, USA with my lovely wife and two beautiful daughters. Life is good. My hobbies are motorcycles, motorcycles, and motorcycles.
 
I run a riders group called Twisties Motorcycle Club. If you're are a rider in the tri-state area, look us up! http://twistiesmc.com/
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Comments and Discussions

 
GeneralRe: This process not working with a WPF application!!! PinmemberJason Jakob20-Jun-13 5:09 
QuestionIt may be.... PinmemberWillian.BR15-May-08 8:55 
GeneralWindows CE .net Pinmemberquestions_c1-Oct-07 2:28 
GeneralRe: Windows CE .net PinmemberMarc Merritt1-Oct-07 15:18 
GeneralRe: Windows CE .net PinmemberPram_Singh4120-Jul-09 4:22 
GeneralError Code 1326 [modified] Pinmembercollapo21-Aug-07 0:56 
GeneralRe: Error Code 1326 Pinmembermirh10-Oct-07 1:59 
GeneralRe: Error Code 1326 Pinmembermustiy9-Feb-10 23:17 
GeneralError 1314 Pinmemberm.aldegheri3-Aug-06 6:28 
GeneralRe: Error 1314 Pinmemberm.aldegheri3-Aug-06 22:23 
GeneralRe: Error 1314 PinmemberMunkieFish11-Apr-07 7:49 
AnswerRe: Error 1314 Pinmemberuppals12-Apr-07 13:06 
GeneralHelp needed Windows 2000 SP4 still getting 1314! -- Re: Error 1314 Pinmemberdevvvy21-Feb-08 20:41 
GeneralRe: Help needed Windows 2000 SP4 still getting 1314! -- Re: Error 1314 PinmemberMarc Merritt26-Feb-08 3:02 
Questionhow to use this in case of a local account? Pinmemberyossof elnaggar27-Jun-06 20:29 
AnswerRe: how to use this in case of a local account? Pinmemberhk1112-Jul-07 19:04 
GeneralRe: how to use this in case of a local account? Pinmemberappalanaidu Aug20118-Feb-12 20:54 
GeneralFirst call takes too long Pinmemberschweeneh4-Apr-06 6:04 
GeneralRe: First call takes too long PinmemberMarc Merritt12-Jun-06 2:24 
GeneralA similar article [modified] PinsitebuilderUwe Keim23-Apr-05 23:59 
GeneralRe: A similar article Pinmembercraigg753-Nov-06 5:57 
GeneralRe: A similar article PinsitebuilderUwe Keim3-Nov-06 6:14 
GeneralImpersonation Pinmemberchriskoiak16-Mar-04 5:13 
QuestionRe: Impersonation Pinmembertee_jay10-Apr-06 22:08 
AnswerRe: Impersonation Pinmemberhk1112-Jul-07 19:01 
GeneralRe: Impersonation PinmemberPhutphornxai19-Jul-07 1:43 
GeneralCoding Style Issues PinmemberAndy Neilson7-May-03 2:56 
GeneralRe: Coding Style Issues PinmemberMaximilian Hänel27-May-03 12:54 
GeneralRe: Coding Style Issues PinmemberAndy Neilson28-May-03 2:53 
GeneralRe: Coding Style Issues PinmemberMaximilian Hänel28-May-03 4:56 
GeneralJust to complete this PinmemberJahava25-Oct-03 4:53 
GeneralRe: Just to complete this PinmemberMarc Merritt25-Oct-03 8:42 
GeneralWhat an attitude... PinmemberJahava27-Oct-03 5:08 
GeneralRe: What an attitude... PinmemberMarc Merritt27-Oct-03 5:46 
GeneralIt's cool PinmemberJahava27-Oct-03 13:45 
GeneralRe: Coding Style Issues PinmemberJonathan C Dickinson5-May-08 1:53 
GeneralError messages PinmemberMaximilian Hänel6-May-03 1:24 
GeneralRe: Error messages PinmemberHaidong Chen27-May-03 12:15 
GeneralRe: Error messages PinmemberHaidong Chen27-May-03 12:17 
GeneralRe: Error messages PinmemberMaximilian Hänel27-May-03 12:47 
GeneralSeImpersonatePrivilege Pinmembergeo_m3-May-03 22:56 
GeneralThis method won't work on Windows 2000 or Windows NT PinmemberSoftomatix3-May-03 13:54 
GeneralRe: This method won't work on Windows 2000 or Windows NT PinmemberMarc Merritt3-May-03 15:53 
GeneralRe: This method won't work on Windows 2000 or Windows NT PinmemberSoftomatix4-May-03 3:57 
GeneralRe: This method won't work on Windows 2000 or Windows NT PinsussDanko Greiner14-Dec-04 0:44 

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