Binaryworld - CheckWindowsUser - Validate a username/password pair ... [ VB -> Windows ]

Private Declare Function LogonUser Lib "Advapi32" Alias "LogonUserA" (ByVal _
  lpszUserName As String, ByVal lpszDomain As String, _
  ByVal lpszPassword As String, ByVal dwLogonType As Long, _
  ByVal dwLogonProvider As Long, phToken As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As _
  Long
Const LOGON32_PROVIDER_DEFAULT = 0&
Const LOGON32_LOGON_NETWORK = 3&

' Check whether a username/password pair is correct
'
' if DOMAIN is omitted, it uses the local account database
' and then asks trusted domains to search their account databases
' until it finds the account or the search is exhausted
' use DOMAIN="." to search only the local account database
'
' IMPORTANT: works only under Windows NT and 2000

Private Function CheckWindowsUser(ByVal UserName As String, _
  ByVal Password As String, Optional ByVal Domain As String) As Boolean
  Dim hToken As Long, ret As Long

  ' provide a default for the Domain name
  If Len(Domain) = 0 Then Domain = vbNullString
  ' check the username/password pair
  ' using LOGON32_LOGON_NETWORK delivers the best performance
  ret = LogonUser(UserName, Domain, Password, LOGON32_LOGON_NETWORK, _
    LOGON32_PROVIDER_DEFAULT, hToken)

  ' a non-zero value means success
  If ret Then
    CheckWindowsUser = True
    CloseHandle hToken
  End If

End Function