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Understanding Built-In User and Group Accounts in IIS

@2020-03-02 10:29:26

If you want to impersonate a user on a thread in ASP.NET, you can use one of the following methods, based on your requirments:

  • Impersonate the IIS authenticated account or user
  • Impersonate a specific user for all the requests of an ASP.NET application
  • Impersonate the authenticating user in code
  • Impersonate a specific user in code

Note You can use the following code to determine what user the thread is executing as:

Impersonate the IIS Authenticated Account or User

To impersonate the Microsoft Internet Information Services (IIS) authenticating user on every request for every page in an ASP.NET application, you must include an <identity> tag in the Web.config file of this application and set the impersonate attribute to true. For example:

<identity impersonate="true" />

Impersonate a Specific User for All the Requests of an ASP.NET Application

To impersonate a specific user for all the requests on all pages of an ASP.NET application, you can specify the userName and password attributes in the <identity> tag of the Web.config file for that application. For example:

<identity impersonate="true" userName="accountname" password="password" />

Impersonate the Authenticating User in Code

To impersonate the authenticating user (User.Identity) only when you run a particular section of code, you can use the code to follow. This method requires that the authenticating user identity is of type WindowsIdentity.

System.Security.Principal.WindowsImpersonationContext impersonationContext;
impersonationContext = 

//Insert your code that runs under the security context of the authenticating user here.


Impersonate a Specific User in Code

To impersonate a specific user only when you run a particular section of code, use the following code:

<%@ Page Language="C#"%>
<%@ Import Namespace = "System.Web" %>
<%@ Import Namespace = "System.Web.Security" %>
<%@ Import Namespace = "System.Security.Principal" %>
<%@ Import Namespace = "System.Runtime.InteropServices" %>

<script runat=server>
public const int LOGON32_LOGON_INTERACTIVE = 2;
public const int LOGON32_PROVIDER_DEFAULT = 0;

WindowsImpersonationContext impersonationContext; 

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);

public void Page_Load(Object s, EventArgs e)
if(impersonateValidUser("username", "domain", "password"))
//Insert your code that runs under the security context of a specific user here.
//Your impersonation failed. Therefore, include a fail-safe mechanism here.

private bool impersonateValidUser(String userName, String domain, String password)
WindowsIdentity tempWindowsIdentity;
IntPtr token = IntPtr.Zero;
IntPtr tokenDuplicate = IntPtr.Zero;

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)
return true;

if(token!= IntPtr.Zero)
return false;

private void undoImpersonation()


Note The identity of the process that impersonates a specific user on a thread must have the "Act as part of the operating system" privilege.


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