Imports System
Imports System.Diagnostics
Imports System.Runtime.InteropServices
Imports System.Security
Imports System.Security.Principal
Imports System.Text




Module ImpersonationExample


    ' PInvoke into the Win32 API to provide access to the 
    ' LogonUser and CloseHandle functions.
    <DllImport("advapi32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)> Function LogonUser(ByVal username As String, ByVal domain As String, ByVal password As IntPtr, ByVal logonType As Integer, ByVal logonProvider As Integer, ByRef token As IntPtr) As Boolean

    End Function


    <DllImport("kernel32.dll", CharSet:=CharSet.Auto)> Function CloseHandle(ByVal handle As IntPtr) As Boolean

    End Function

    ' Define the required LogonUser enumerations.
    Const LOGON32_PROVIDER_DEFAULT As Integer = 0
    Const LOGON32_LOGON_INTERACTIVE As Integer = 2



    Sub Main(ByVal args() As String)
        Try
            ' Display the current user before impersonation.
            Console.WriteLine("Before impersonation: " + WindowsIdentity.GetCurrent().Name)

            ' Ask the user for a network domain.
            Console.Write("Please enter your domain:")

            Dim domain As String = Console.ReadLine()

            ' Ask the user for a user name.
            Console.Write("Please enter your user name:")

            Dim username As String = Console.ReadLine()

            ' Ask the user for a password.
            Console.Write("Please enter your password:")

            Dim passWord As SecureString = GetPassword()

            ' Impersonate the account provided by the user.
            Dim userContext As WindowsImpersonationContext = ImpersonateUser(passWord, username, domain)

            ' Display the current user after impersonation.
            Console.WriteLine("After impersonation: " + WindowsIdentity.GetCurrent().Name)
        Catch e As Exception
            Console.WriteLine(e.Message)
        End Try

        Console.ReadLine()

    End Sub



    Function GetPassword() As SecureString
        Dim password As New SecureString()

        ' get the first character of the password
        Dim nextKey As ConsoleKeyInfo = Console.ReadKey(True)

        While nextKey.Key <> ConsoleKey.Enter
            If nextKey.Key = ConsoleKey.BackSpace Then
                If password.Length > 0 Then
                    password.RemoveAt(password.Length - 1)

                    ' erase the last * as well
                    Console.Write(nextKey.KeyChar)
                    Console.Write(" ")
                    Console.Write(nextKey.KeyChar)
                End If
            Else
                password.AppendChar(nextKey.KeyChar)
                Console.Write("*")
            End If

            nextKey = Console.ReadKey(True)
        End While

        Console.WriteLine()

        ' lock the password down
        password.MakeReadOnly()
        Return password

    End Function



    Function ImpersonateUser(ByVal password As SecureString, ByVal userName As String, ByVal domainName As String) As WindowsImpersonationContext
        Dim tokenHandle As IntPtr = IntPtr.Zero

        Dim passwordPtr As IntPtr = IntPtr.Zero

        Dim returnValue As Boolean = False

        Try
            ' Marshal the SecureString to unmanaged memory.
            passwordPtr = Marshal.SecureStringToGlobalAllocUnicode(password)

            ' Call LogonUser, passing the unmanaged (and decrypted) copy of
            ' the SecureString password.
            returnValue = LogonUser(userName, domainName, passwordPtr, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, tokenHandle)


        Finally
            ' Zero-out and free the unmanaged string reference.
            Marshal.ZeroFreeGlobalAllocUnicode(passwordPtr)

            ' Close the token handle.
            CloseHandle(tokenHandle)
        End Try

        ' Get the Last win32 Error and throw an exception.
        If Not returnValue AndAlso tokenHandle = IntPtr.Zero Then
            Dim [error] As Integer = Marshal.GetLastWin32Error()

            Throw New System.ComponentModel.Win32Exception([error])
        End If
        ' The token that is passed to the following constructor must 
        ' be a primary token in order to use it for impersonation.
        Dim newId As New WindowsIdentity(tokenHandle)

        Return newId.Impersonate()

    End Function
End Module

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Principal;
using System.Text;

namespace SecureStringImpersonationExample
{

    class ImpersonationExample
    {

        // PInvoke into the Win32 API to provide access to the 
        // LogonUser and CloseHandle functions.
        [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
        internal static extern bool LogonUser(String username, String domain, IntPtr password,
                int logonType, int logonProvider, ref IntPtr token);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
        public extern static bool CloseHandle(IntPtr handle);

        // Define the required LogonUser enumerations.
        const int LOGON32_PROVIDER_DEFAULT = 0;
        const int LOGON32_LOGON_INTERACTIVE = 2;


        static void Main(string[] args)
        {
            try
            {
                // Display the current user before impersonation.
                Console.WriteLine("Before impersonation: "
                    + WindowsIdentity.GetCurrent().Name);

                // Ask the user for a network domain.
                Console.Write("Please enter your domain:");

                string domain = Console.ReadLine();

                // Ask the user for a user name.
                Console.Write("Please enter your user name:");

                string username = Console.ReadLine();

                // Ask the user for a password.
                Console.Write("Please enter your password:");

                SecureString passWord = GetPassword();

                // Impersonate the account provided by the user.
                WindowsImpersonationContext userContext = ImpersonateUser(passWord, username, domain);

                // Display the current user after impersonation.
                Console.WriteLine("After impersonation: "
                    + WindowsIdentity.GetCurrent().Name);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }

            Console.ReadLine();


        }

        public static SecureString GetPassword()
        {
            SecureString password = new SecureString();

            // get the first character of the password
            ConsoleKeyInfo nextKey = Console.ReadKey(true);

            while (nextKey.Key != ConsoleKey.Enter)
            {
                if (nextKey.Key == ConsoleKey.Backspace)
                {
                    if (password.Length > 0)
                    {
                        password.RemoveAt(password.Length - 1);

                        // erase the last * as well
                        Console.Write(nextKey.KeyChar);
                        Console.Write(" ");
                        Console.Write(nextKey.KeyChar);
                    }
                }
                else
                {
                    password.AppendChar(nextKey.KeyChar);
                    Console.Write("*");
                }

                nextKey = Console.ReadKey(true);
            }

            Console.WriteLine();

            // lock the password down
            password.MakeReadOnly();
            return password;
        }


        public static WindowsImpersonationContext ImpersonateUser(SecureString password, string userName, string domainName)
        {
            IntPtr tokenHandle = IntPtr.Zero;

            IntPtr passwordPtr = IntPtr.Zero;

            bool returnValue = false;

            try
            {
                // Marshal the SecureString to unmanaged memory.
                passwordPtr = Marshal.SecureStringToGlobalAllocUnicode(password);

                // Call LogonUser, passing the unmanaged (and decrypted) copy of
                // the SecureString password.
                returnValue = LogonUser(userName, domainName, passwordPtr, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, ref tokenHandle);

            }
            finally
            {
                // Zero-out and free the unmanaged string reference.
                Marshal.ZeroFreeGlobalAllocUnicode(passwordPtr);

                // Close the token handle.
                CloseHandle(tokenHandle);
            }

            // Get the Last win32 Error and throw an exception.
            if (!returnValue && tokenHandle == IntPtr.Zero)
            {
                int error = Marshal.GetLastWin32Error();

                throw new System.ComponentModel.Win32Exception(error);

            }
            // The token that is passed to the following constructor must 
            // be a primary token in order to use it for impersonation.
            WindowsIdentity newId = new WindowsIdentity(tokenHandle);

            return newId.Impersonate();
        }
    }
}