Windows Authentication.

[Asgorath]

Hi,
use this code to authenticate a user on a windows domain.

Option Strict On
Option Explicit On 
 
Imports System
Imports System.Security.Principal
 
    Declare Function LogonUserA Lib "advapi32.dll" (ByVal lpszUsername As String, ByVal lpszDomain As String, ByVal lpszPassword As String, ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, ByRef phToken As IntPtr) As Integer
    Declare Auto Function DuplicateToken Lib "advapi32.dll" (ByVal ExistingTokenHandle As IntPtr, ByVal ImpersonationLevel As Integer, ByRef DuplicateTokenHandle As IntPtr) As Integer
    Declare Auto Function RevertToSelf Lib "advapi32.dll" () As Long
    Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Long
    Private LOGON32_LOGON_INTERACTIVE As Integer = 2
    Private LOGON32_PROVIDER_DEFAULT As Integer = 0
    Private impersonationContext As WindowsImpersonationContext
 
    Private Function impersonateValidUser(ByVal userName As String, ByVal domain As String, ByVal password As String) As Boolean
 
        Dim tempWindowsIdentity As WindowsIdentity
        Dim token As IntPtr = IntPtr.Zero
        Dim tokenDuplicate As IntPtr = IntPtr.Zero
        impersonateValidUser = False
 
        If RevertToSelf() <> 0 Then
            If LogonUserA(userName, domain, password, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, token) <> 0 Then
                If DuplicateToken(token, 2, tokenDuplicate) <> 0 Then
                    tempWindowsIdentity = New WindowsIdentity(tokenDuplicate)
                    impersonationContext = tempWindowsIdentity.Impersonate()
                    If Not impersonationContext Is Nothing Then
                        impersonateValidUser = True
                    End If
                End If
            End If
        End If
        If Not tokenDuplicate.Equals(IntPtr.Zero) Then
            CloseHandle(tokenDuplicate)
        End If
        If Not token.Equals(IntPtr.Zero) Then
            CloseHandle(token)
        End If
    End Function
    Private Sub undoImpersonation()
        impersonationContext.Undo()
    End Sub
 
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
 
        If impersonateValidUser(Me.TextBox1.Text, SystemInformation.UserDomainName(), Me.TextBox2.Text) Then
            Console.WriteLine("Autenticated")
            'Insert your code that runs under the security context of a specific user here.
            undoImpersonation()
        Else
            MessageBox.Show("Invalid Password")
            Exit Sub
        End If
 
    End Sub

Regards
Jorge