Hi,
use this code to authenticate a user on a windows domain.I have
tested this code in my company network it is not working.But the
Same code is working in other places.
If any one know the reason please mail me

Regards
Anwar


visual basic code:


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