Develop Reference

Access the HKCU registry hive for an impersonated user in C#

I need to implement functionality that impersonates a domain user. The impersonated thread needs to be able to read from/write to HKCU registry hive for the impersonated user. I am able to impersonate the user, but when I attempt to load any registry keys, I receive a Win32 "Access is denied" exception.
NOTE: The intention here is to provide a pseudo impersonated command-line to perform a specific set of actions as a service account. The service account may not have interactive logon rights, so I am required to use the BATCH logon type. As a test, I did also try the INTERACTIVE logon type, but the result was the same.
I followed this CodeProject article as a general guide. Here is what I have:
partial class Program
{
[DllImport("advapi32.dll")]
public 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)]
public static extern int DuplicateToken(IntPtr hToken, int impersonationLevel, ref IntPtr hNewToken);
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern bool RevertToSelf();
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern bool CloseHandle(IntPtr handle);
[DllImport("advapi32.dll", CharSet = CharSet.Auto)]
public static extern int RegOpenCurrentUser(int samDesired, out IntPtr phkResult);
[DllImport("userenv.dll", SetLastError = true, CharSet = CharSet.Auto)]
public static extern bool LoadUserProfile(IntPtr hToken, ref ProfileInfo lpProfileInfo);
[DllImport("Userenv.dll", CallingConvention = CallingConvention.Winapi, SetLastError = true, CharSet = CharSet.Auto)]
public static extern bool UnloadUserProfile(IntPtr hToken, IntPtr lpProfileInfo);
[StructLayout(LayoutKind.Sequential)]
public struct ProfileInfo
{
public int dwSize;
public int dwFlags;
public string lpUserName;
public string lpProfilePath;
public string lpDefaultPath;
public string lpServerName;
public string lpPolicyPath;
public IntPtr hProfile;
}
private static string ImpUser = string.Empty;
private static string ImpDomain = string.Empty;
private static string FullyQualifiedImpUser
{
get
{
return $"{ImpDomain}\\{ImpUser}";
}
}
private static SecureString ImpSecret = new SecureString();
private static bool CurrentlyImpersonating = false;
private static WindowsIdentity ImpersonatedIdentity = null;
private static IntPtr Token = IntPtr.Zero;
private static IntPtr TokenDuplicate = IntPtr.Zero;
//*** THIS IS THE CORE METHOD ***
private static void EnterModeImpersonated()
{
bool loadSuccess;
int errCode;
try
{
if (RevertToSelf())
{
if (LogonUser(ImpUser, ImpDomain,
ImpSecret.Plaintext(), Constants.LOGON32_LOGON_TYPE_BATCH,
Constants.LOGON32_PROVIDER_DEFAULT, ref Token) != 0)
{
if (DuplicateToken(Token, Constants.SecurityImpersonation, ref TokenDuplicate) != 0)
{
ImpersonatedIdentity = new WindowsIdentity(TokenDuplicate);
using (WindowsImpersonationContext m_ImpersonationContext = ImpersonatedIdentity.Impersonate())
{
if (m_ImpersonationContext != null)
{
#region LoadUserProfile
// Load user profile
ProfileInfo profileInfo = new ProfileInfo();
profileInfo.dwSize = Marshal.SizeOf(profileInfo);
profileInfo.lpUserName = ImpUser;
profileInfo.dwFlags = 1;
//Here is where I die:
loadSuccess = LoadUserProfile(TokenDuplicate, ref profileInfo);
if (!loadSuccess)
{
errCode = Marshal.GetLastWin32Error();
Win32Exception ex = new Win32Exception(errCode);
throw new Exception($"Failed to load profile for {FullyQualifiedImpUser}. Error code: {errCode}", ex);
}
if (profileInfo.hProfile == IntPtr.Zero)
{
errCode = Marshal.GetLastWin32Error();
Win32Exception ex = new Win32Exception(errCode);
throw new Exception($"Failed accessing HKCU registry for {FullyQualifiedImpUser}. Error code: {errCode}", ex);
}
#endregion
CloseHandle(Token);
CloseHandle(TokenDuplicate);
RegistryAgent.GetRootKeys(profileInfo.hProfile);
EnterMode();
UnloadUserProfile(TokenDuplicate, profileInfo.hProfile);
m_ImpersonationContext.Undo();
RegistryAgent.GetRootKeys(Constants.RevertToInvoker);
}
}
}
else
{
Console.WriteLine("DuplicateToken() failed with error code: " +
Marshal.GetLastWin32Error());
throw new Win32Exception(Marshal.GetLastWin32Error());
}
}
}
}
catch (Win32Exception we)
{
throw we;
}
catch
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
finally
{
if (Token != IntPtr.Zero) CloseHandle(Token);
if (TokenDuplicate != IntPtr.Zero) CloseHandle(TokenDuplicate);
Console.WriteLine("After finished impersonation: " +
WindowsIdentity.GetCurrent().Name);
}
}
//Toggles on impersonation mode
//Here, we grab the username, domain and password.
private static bool EnableImpersonation(string userInfo)
{
if (userInfo.Contains('\\'))
{
string[] parts = Parameter.ImpUser.TextValue.Split('\\');
ImpUser = parts[1];
ImpDomain = parts[0];
}
else
{
ImpUser = userInfo;
ImpDomain = Environment.UserDomainName;
}
//Prompt for the invoker to enter the impersonated account password
GetSecret();
if (TryImpersonate())
{
CurrentlyImpersonating = true;
}
else
{
DisableImpersonation();
}
return CurrentlyImpersonating;
}
//Toggles off impersontation & cleans up
private static void DisableImpersonation()
{
ImpSecret = null;
ImpersonatedIdentity = null;
Token = IntPtr.Zero;
TokenDuplicate = IntPtr.Zero;
ImpUser = string.Empty;
ImpDomain = string.Empty;
CurrentlyImpersonating = false;
}
//Implements a console prompt to grab the impersonated account password
//as a SecureString object
private static void GetSecret()
{
ImpSecret = new SecureString();
ConsoleKeyInfo key;
Console.Write($"\r\nEnter the password for {FullyQualifiedImpUser}: ");
do
{
key = Console.ReadKey(true);
if (key.Key != ConsoleKey.Backspace && key.Key != ConsoleKey.Enter)
{
ImpSecret.AppendChar(key.KeyChar);
Console.Write("*");
}
else
{
if (key.Key == ConsoleKey.Backspace && ImpSecret.Length != 0)
{
ImpSecret.RemoveAt(ImpSecret.Length - 1);
Console.Write("\b \b");
}
}
}
while (key.Key != ConsoleKey.Enter);
Console.WriteLine();
}
//This method is intended to ensure that the credentials entered
//for the impersonated user are correct.
private static bool TryImpersonate()
{
IntPtr testToken = IntPtr.Zero;
int result;
try
{
result = LogonUser(ImpUser, ImpDomain, ImpSecret.Plaintext(), Constants.LOGON32_LOGON_TYPE_BATCH, Constants.LOGON32_PROVIDER_DEFAULT, ref testToken);
if (result == 0)
{
int errCode = Marshal.GetLastWin32Error();
Win32Exception ex = new Win32Exception(errCode);
throw new Exception($"Failed to impersonate {FullyQualifiedImpUser}. Error code: {errCode}", ex);
}
return true;
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
return false;
}
}
}
I also read The MSDN documentation for LoadUserProfileA (I didn't find an article for LoadUserProfile() so I have to assume this is the ultimate COM function being called). It indicates:
The token must have TOKEN_QUERY, TOKEN_IMPERSONATE, and TOKEN_DUPLICATE access.. I'm wondering if the logon token or duplicated token needs to be created differently in order to include these rights? I wasn't able to find any documentation on how to manipulate the token rights, though...

I was able to resolve this problem. Here's what I did:
First, there are several Win32 methods which need to be exposed:
[DllImport("advapi32.dll")]
public static extern int LogonUser(String lpszUserName, String lpszDomain, String lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken);
[DllImport("userenv.dll")]
public static extern bool LoadUserProfile(IntPtr hToken, ref ProfileInfo lpProfileInfo);
[DllImport("advapi32.dll", CharSet = CharSet.Auto)]
public static extern int RegDisablePredefinedCache();
You'll also need to define a struct in support of calling LoadUserProfile()
[StructLayout(LayoutKind.Sequential)]
public struct ProfileInfo
{
public int dwSize;
public int dwFlags;
public string lpUserName;
public string lpProfilePath;
public string lpDefaultPath;
public string lpServerName;
public string lpPolicyPath;
public IntPtr hProfile;
}
We're going to store the impersonation account password in a SecureString object, but we also want to be able to easily access it as plaintext.
I used the following method to populate the SecureString password, masked, at a console prompt:
public static SecureString GetPasswordAsSecureString(string prompt)
{
SecureString pwd = new SecureString();
ConsoleKeyInfo key;
Console.Write(prompt + #": ");
do
{
key = Console.ReadKey(true);
if (key.Key != ConsoleKey.Backspace && key.Key != ConsoleKey.Enter)
{
pwd.AppendChar(key.KeyChar);
Console.Write("*");
}
else
{
if (key.Key == ConsoleKey.Backspace && pwd.Length != 0)
{
pwd.RemoveAt(pwd.Length - 1);
Console.Write("\b \b");
}
}
}
while (key.Key != ConsoleKey.Enter);
Console.WriteLine();
return pwd;
}
var impPassword = GetPasswordAsSecureString($"Enter the password for {impUser}");
I also recommend defining the following extension method in order to conveniently convert a SecureString to a normal string since one of the Win32 methods we need to use will only accept a normal string:
public static string ToUnSecureString(this SecureString securePassword)
{
if (securePassword == null)
{
return string.Empty;
}
IntPtr unmanagedString = IntPtr.Zero;
try
{
unmanagedString = Marshal.SecureStringToGlobalAllocUnicode(securePassword);
return Marshal.PtrToStringUni(unmanagedString);
}
finally
{
Marshal.ZeroFreeGlobalAllocUnicode(unmanagedString);
}
}
Before doing anything else having to do with impersonation, we need to call the Win32 method RegDisablePredefinedCache(). In terms of our purpose, this method tells Windows to dynamically determine where to look for the HKEY_CURRENT_USER registry hive, rather than using the cached location from when the process was initially invoked (Failing to call this method explains the "Access is denied" exception I was receiving previously. The impersonated user was attempting to load the HKCU hive for the invoker's account, which is obviously not allowed)
RegDisablePredefinedCache();
Next, we need to load that account's profile before entering the impersonated thread. This ensures that the impersonated account's registry hive is available in memory. We call the LogonUser() and LoadUserProfile() COM methods in order to accomplish that:
// Get a token for the user
const int LOGON32_LOGON_BATCH = 4;
const int LOGON32_PROVIDER_DEFAULT = 0;
//We'll use our extension method to pass the password as a normal string
LogonUser(ImpUser, ImpDomain, ImpPassword.ToUnSecureString(), LOGON32_LOGON_BATCH, LOGON32_PROVIDER_DEFAULT, ref Token);
// Load user profile
ProfileInfo profileInfo = new ProfileInfo();
profileInfo.dwSize = Marshal.SizeOf(profileInfo);
profileInfo.lpUserName = ImpUser;
profileInfo.dwFlags = 1;
bool loadSuccess = LoadUserProfile(Token, ref profileInfo);
//Detect and handle failure gracefully
if (!loadSuccess)
{
errCode = Marshal.GetLastWin32Error();
Win32Exception ex = new Win32Exception(errCode);
throw new Exception($"Failed to load profile for {ImpUser}. Error code: {errCode}", ex);
}
if (profileInfo.hProfile == IntPtr.Zero)
{
errCode = Marshal.GetLastWin32Error();
Win32Exception ex = new Win32Exception(errCode);
throw new Exception($"Failed accessing HKCU registry for {ImpUser}. Error code: {errCode}", ex);
}
Finally, thanks to one of the comments left on this question, I discovered a nifty nuget package called SimpleImpersonation. This obfuscates away most of the complexity involved with account impersonation:
//Note that UserCredentials() constructor I chose requires the
//password to be passed as a SecureString object.
var Credentials = new UserCredentials(impDomain, impUser, impPassword);
Impersonation.RunAsUser(Credentials, LogonType.Batch, () =>
{
//Within this bock, you can call methods such as
//Registry.CurrentUser.OpenSubKey()
//and they use the impersonated account's registry hive
}

C# How to change user context in app running on system

I have an application that runs with the system user. I need that some code in the app runs on user context (with the user itself). For example i need to use the webclient in user context because that way my firewall recognize the username, but later i need to run some other code ex. Running a exe in system context (with system user) because i need the privileges.
Is there a way to do this?.
Thanks!!!

I have used this code to impersonate certain operations
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Security.Principal;
using NLog;
namespace Core.Impersonation
{
public class ImpersonatedUser : IDisposable
{
private static Logger logger = LogManager.GetCurrentClassLogger();
IntPtr userHandle;
WindowsImpersonationContext impersonationContext;
public ImpersonatedUser(string user, string domain, string password)
{
logger.Debug("Impersonating user: " + domain + #"\" + user);
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();
logger.Debug("Finished Impersonating user");
}
}
[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,
}
}
}
and then usage:
using (var i = new ImpersonatedUser("someLogin", "someDomain", "thePassword"))
{
var u = System.Environment.UserName;
}

How deleted, replaced file at share folder

Hello I have a problem with deleting and replacing files at share folder
I have full access.
"access to the path was denied"
The copy function works well in both directions.
(but I have to delete files manually).
SERVER - >>> PC
SERVER <<< - PC
The program connects to the file server under another user and manipulate with files (copy files worked fine, delete files doesn't work replace doesn't work).
private void replaceFile(string source, string sourceName ,string destination)
{
try
{
using (new Impersonator(username(), domain(), password()))
{
//File.delete(destination);
//File.Copy(source, destination, true);
File.Replace(source, destination, null);
}
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
}
private void copyFile(string source, string destination)
{
try
{
using (new Impersonator(username(), domain(), password()))
{
File.Copy(source, destination, true);
}
}
catch (Exception e)
{
MessageBox.Show(e.Message);
}
}
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Windows.Forms;
namespace IFS_FileManager
{
public enum LogonType
{
LOGON32_LOGON_INTERACTIVE = 2,
LOGON32_LOGON_NETWORK = 3,
LOGON32_LOGON_BATCH = 4,
LOGON32_LOGON_SERVICE = 5,
LOGON32_LOGON_UNLOCK = 7,
LOGON32_LOGON_NETWORK_CLEARTEXT = 8, // Win2K or higher
LOGON32_LOGON_NEW_CREDENTIALS = 9 // Win2K or higher
};
public enum LogonProvider
{
LOGON32_PROVIDER_DEFAULT = 0,
LOGON32_PROVIDER_WINNT35 = 1,
LOGON32_PROVIDER_WINNT40 = 2,
LOGON32_PROVIDER_WINNT50 = 3
};
public enum ImpersonationLevel
{
SecurityAnonymous = 0,
SecurityIdentification = 1,
SecurityImpersonation = 2,
SecurityDelegation = 3
}
class Win32NativeMethods
{
[DllImport("advapi32.dll", SetLastError = true)]
public 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)]
public static extern int DuplicateToken(IntPtr hToken,
int impersonationLevel,
ref IntPtr hNewToken);
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern bool RevertToSelf();
[DllImport("kernel32.dll", CharSet = CharSet.Auto)]
public static extern bool CloseHandle(IntPtr handle);
}
public class Impersonator : IDisposable
{
private WindowsImpersonationContext _wic;
public Impersonator(string userName, string domainName, string password, LogonType logonType, LogonProvider logonProvider)
{
Impersonate(userName, domainName, password, logonType, logonProvider);
}
public Impersonator(string userName, string domainName, string password)
{
Impersonate(userName, domainName, password, LogonType.LOGON32_LOGON_INTERACTIVE, LogonProvider.LOGON32_PROVIDER_DEFAULT);
}
public Impersonator() { }
public void Dispose()
{
UndoImpersonation();
}
public void Impersonate(string userName, string domainName, string password)
{
Impersonate(userName, domainName, password, LogonType.LOGON32_LOGON_INTERACTIVE, LogonProvider.LOGON32_PROVIDER_DEFAULT);
}
public void Impersonate(string userName, string domainName, string password, LogonType logonType, LogonProvider logonProvider)
{
UndoImpersonation();
IntPtr logonToken = IntPtr.Zero;
IntPtr logonTokenDuplicate = IntPtr.Zero;
try
{
// revert to the application pool identity, saving the identity of the current requestor
_wic = WindowsIdentity.Impersonate(IntPtr.Zero);
// do logon & impersonate
if (Win32NativeMethods.LogonUser(userName,domainName,password,(int)logonType,(int)logonProvider,ref logonToken) != 0)
{
if (Win32NativeMethods.DuplicateToken(logonToken, (int)ImpersonationLevel.SecurityImpersonation, ref logonTokenDuplicate) != 0)
{
var wi = new WindowsIdentity(logonTokenDuplicate);
wi.Impersonate();
// discard the returned identity context (which is the context of the application pool)
}
else
MessageBox.Show("\n " + Marshal.GetLastWin32Error(), "Error Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
else
MessageBox.Show("\n " + Marshal.GetLastWin32Error(), "Error Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
finally
{
if (logonToken != IntPtr.Zero)
Win32NativeMethods.CloseHandle(logonToken);
if (logonTokenDuplicate != IntPtr.Zero)
Win32NativeMethods.CloseHandle(logonTokenDuplicate);
}
}
/// <summary>
/// Stops impersonation.
/// </summary>
private void UndoImpersonation()
{
// restore saved requestor identity
if (_wic != null)
_wic.Undo();
_wic = null;
}
}
}

Unable to find an entry point named 'LogonUser' in DLL 'advapi32.dll' Impersonation exception

I'm getting the following exception when going through some legacy impersonation logic:
Unable to find an entry point named 'LogonUser' in DLL 'advapi32.dll'
I understand that the error means that my app can't find the LogonUser method in the advapi32.dll.
The code looks something like this:
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
private static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken);
if(LogonUser(_username, _domainname, _password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref _tokenHandle))
{
//do stuff...
}
Has anyone had a similar error - any suggestions on how to fix it or why it is happening? Is there a better way to do this besides using the advapi32.dll (its a .net 3.5 solution but there are lots of legacy classes)?

Maybe it has something to do with the "ExactSpelling = true"
This seems to work:
public enum LogonType : int
{
Interactive = 2,
Network = 3,
Batch = 4,
Service = 5,
Unlock = 7,
NetworkCleartText = 8,
NewCredentials = 9,
}
public enum LogonProvider : int
{
Default = 0,
}
public class Impersonation : IDisposable
{
#region Dll Imports
[DllImport("kernel32.dll")]
private static extern Boolean CloseHandle(IntPtr hObject);
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool LogonUser(string username, string domain,
string password, LogonType logonType,
LogonProvider logonProvider,
out IntPtr userToken);
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool DuplicateToken(IntPtr token, int impersonationLevel,
ref IntPtr duplication);
[DllImport("advapi32.dll", SetLastError = true)]
static extern bool ImpersonateLoggedOnUser(IntPtr userToken);
#endregion
#region Private members
private bool _disposed;
private WindowsImpersonationContext _impersonationContext;
#endregion
#region Constructors
public Impersonation(String username, String domain, String password)
{
IntPtr userToken = IntPtr.Zero;
IntPtr userTokenDuplication = IntPtr.Zero;
// Logon with user and get token.
bool loggedOn = LogonUser(username, domain, password,
LogonType.Interactive, LogonProvider.Default,
out userToken);
if (loggedOn)
{
try
{
// Create a duplication of the usertoken, this is a solution
// for the known bug that is published under KB article Q319615.
if (DuplicateToken(userToken, 2, ref userTokenDuplication))
{
// Create windows identity from the token and impersonate the user.
WindowsIdentity identity = new WindowsIdentity(userTokenDuplication);
_impersonationContext = identity.Impersonate();
}
else
{
// Token duplication failed!
// Use the default ctor overload
// that will use Mashal.GetLastWin32Error();
// to create the exceptions details.
throw new Exception("Could not copy token");
}
}
finally
{
// Close usertoken handle duplication when created.
if (!userTokenDuplication.Equals(IntPtr.Zero))
{
// Closes the handle of the user.
CloseHandle(userTokenDuplication);
userTokenDuplication = IntPtr.Zero;
}
// Close usertoken handle when created.
if (!userToken.Equals(IntPtr.Zero))
{
// Closes the handle of the user.
CloseHandle(userToken);
userToken = IntPtr.Zero;
}
}
}
else
{
throw new Exception("Login failed");
}
}
~Impersonation()
{
Dispose(false);
}
#endregion
#region Public methods
public void Revert()
{
if (_impersonationContext != null)
{
// Revert to previous user.
_impersonationContext.Undo();
_impersonationContext = null;
}
}
#endregion
#region IDisposable implementation.
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (!_disposed)
{
Revert();
_disposed = true;
}
}
#endregion
}

Have you tried using the version of LogonUser's signature provided on pinvoke.net?

ASP.NET Development Server permissions and Network Resources

My ASP.NET 4.0 Web App is unable to access Network Printers, while debugging on VS 2010. It can access local printers. Seems like it may be a permissions issue. Since VS2010 Debugging runs on ASP.NET Development Server, it must be running under the account I used to log into Windows, right? Does that user need to be added as an Admin in that printers users? Is there any account that I can impersonate to get this working?

You are correct, debugging through Visual Studio means all of your code runs with the same rights as the user logged in to windows. On the server, you will need to setup impersonation and/or setup your Application Pool to run as a user who has access to print on these printers.
I recommend you setup a dedicated domain account (like domain\yourapp-impers-user) and either set the Application Pool to use that, or setup impersonation in your web.config. Then on the print server, you simply grant that user account the necessary permissions.

Here is an example of impersonation
using System;
using System.Collections.Generic;
using System.Web.Security;
using System.Security.Principal;
using System.Runtime.InteropServices;
using System.Linq;
using System.Web;
using System.IO;
public partial class Main : PageBase
{
public const int LOGON32_LOGON_INTERACTIVE = 2;
public const int LOGON32_PROVIDER_DEFAULT = 0;
WindowsImpersonationContext impersonationContext;
[DllImport("advapi32.dll")]
public static extern int LogonUserA(String lpszUserName,
String lpszDomain,
String lpszPassword,
int dwLogonType,
int dwLogonProvider,
ref IntPtr phToken);
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern int DuplicateToken(IntPtr hToken,
int impersonationLevel,
ref IntPtr hNewToken);
[DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern bool RevertToSelf();
[DllImport("kernel32.dll", CharSet = CharSet.Auto)]
public static extern bool CloseHandle(IntPtr handle);
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == false)
{
if (impersonateValidUser("Username", "Domain", "Password"))
{
//Your code under a specific user here.
}
}
}
private bool impersonateValidUser(String userName, String domain, String password)
{
WindowsIdentity tempWindowsIdentity;
IntPtr token = IntPtr.Zero;
IntPtr tokenDuplicate = IntPtr.Zero;
if (RevertToSelf())
{
if (LogonUserA(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();
if (impersonationContext != null)
{
CloseHandle(token);
CloseHandle(tokenDuplicate);
return true;
}
}
}
}
if (token != IntPtr.Zero)
CloseHandle(token);
if (tokenDuplicate != IntPtr.Zero)
CloseHandle(tokenDuplicate);
return false;
}
private void undoImpersonation()
{
impersonationContext.Undo();
}
Good luck !

without knowing for sure, you can try to impersonate the Network Service, or of course your own domain account which should always work.