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| // This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
// IMPORTANT NOTES:
// This sample can be run only on Windows XP. The default Windows 2000 security policy
// prevents this sample from executing properly, and changing the policy to allow
// proper execution presents a security risk.
// This sample requests the user to enter a password on the console screen.
// Because the console window does not support methods allowing the password to be masked,
// it will be visible to anyone viewing the screen.
// The sample is intended to be executed in a .NET Framework 1.1 environment. To execute
// this code in a 1.0 environment you will need to use a duplicate token in the call to the
// WindowsIdentity constructor. See KB article Q319615 for more information.
using System;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Security.Permissions;
using System.Windows.Forms;
[assembly:SecurityPermissionAttribute(SecurityAction.RequestMinimum, UnmanagedCode=true)]
[assembly:PermissionSetAttribute(SecurityAction.RequestMinimum, Name ="FullTrust")]
public class ImpersonationDemo
{
[DllImport("advapi32.dll", SetLastError=true, CharSet = CharSet.Unicode)]
public static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword,
int dwLogonType, int dwLogonProvider, ref IntPtr phToken);
[DllImport("kernel32.dll", CharSet=System.Runtime.InteropServices.CharSet.Auto)]
private unsafe static extern int FormatMessage(int dwFlags, ref IntPtr lpSource,
int dwMessageId, int dwLanguageId, ref String lpBuffer, int nSize, IntPtr *Arguments);
[DllImport("kernel32.dll", CharSet=CharSet.Auto)]
public extern static bool CloseHandle(IntPtr handle);
[DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
public extern static bool DuplicateToken(IntPtr ExistingTokenHandle,
int SECURITY_IMPERSONATION_LEVEL, ref IntPtr DuplicateTokenHandle);
// Test harness.
// If you incorporate this code into a DLL, be sure to demand FullTrust.
[PermissionSetAttribute(SecurityAction.Demand, Name ="FullTrust")]
public static void Main(string[] args)
{
IntPtr tokenHandle = new IntPtr(0);
IntPtr dupeTokenHandle = new IntPtr(0);
try
{
string userName, domainName;
// Get the user token for the specified user, domain, and password using the
// unmanaged LogonUser method.
// The local machine name can be used for the domain name to impersonate a user on this machine.
Console.Write("Enter the name of the domain on which to log on:");
domainName = Console.ReadLine();
Console.Write("Enter the login of a user on {0} that you wish to impersonate:", domainName);
userName = Console.ReadLine();
Console.Write("Enter the password for {0}:", userName);
const int LOGON32_PROVIDER_DEFAULT = 0;
//This parameter causes LogonUser to create a primary token.
const int LOGON32_LOGON_INTERACTIVE = 2;
tokenHandle = IntPtr.Zero;
// Call LogonUser to obtain a handle to an access token.
bool returnValue = LogonUser(userName, domainName, Console.ReadLine(),
LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
ref tokenHandle);
Console.WriteLine("LogonUser called.");
if (false == returnValue)
{
int ret = Marshal.GetLastWin32Error();
Console.WriteLine("LogonUser failed with error code : {0}", ret);
throw new System.ComponentModel.Win32Exception(ret);
}
Console.WriteLine("Did LogonUser Succeed?" + (returnValue?"Yes" :"No"));
Console.WriteLine("Value of Windows NT token:" + tokenHandle);
// Check the identity.
Console.WriteLine("Before impersonation:"
+ WindowsIdentity.GetCurrent().Name);
// Use the token handle returned by LogonUser.
WindowsIdentity newId = new WindowsIdentity(tokenHandle);
WindowsImpersonationContext impersonatedUser = newId.Impersonate();
// Check the identity.
Console.WriteLine("After impersonation:"
+ WindowsIdentity.GetCurrent().Name);
// Stop impersonating the user.
impersonatedUser.Undo();
// Check the identity.
Console.WriteLine("After Undo:" + WindowsIdentity.GetCurrent().Name);
// Free the tokens.
if (tokenHandle != IntPtr.Zero)
CloseHandle(tokenHandle);
}
catch(Exception ex)
{
Console.WriteLine("Exception occurred." + ex.Message);
}
}
} |
