Hello, I wrote a VB application to validate an NT login screen.  Nothing
fancy, just trying new things.  This program (source code below) was working
perfect until I rebuilt my machine.  For some reason now when it calls the
LOGONUSER function it always returns false!  I'm lost.  I'm on an NT
workstation with VB6.0 loaded with MDAC 2.1, NT OPtions pack 4.0 with SP4.
(if you need to know what else was loaded that might help please let me
know).  I theory is that at some point prior, I must have loaded something
which might have given me the latest advapi32.dll  (not sure what).  Where
can I get the latest dll (from what product)?

Any advice or leads into the right direction would be greatly appreciated!!

Thanks,
Mark Lavoie

============================================================================
===
Option Explicit

Private Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA"
(ByVal lpbuffer As String, nSize As Long) As Long
Private Declare Function LogonUser Lib "advapi32.dll" 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 ImpersonateLoggedOnUser Lib "advapi32.dll" (ByVal
hToken As Long) As Long
Private Declare Function RevertToSelf Lib "advapi32.dll" () As Long

Private UserName As String
Private Password As String
Private Domain As String

Public Function ValLogon(ByVal strAdminUser As String, ByVal
strAdminPassword As String, ByVal strAdminDomain As String)
Dim Ok As Boolean
Dim lngTokenHandle As Long
Dim lngLogonType As Long
Dim lngLogonProvider As Long

On Error GoTo ErrorHandler

   lngLogonType = 2        'LOGON32_LOGON_INTERACTIVE
   lngLogonProvider = 0   'LOGON32_PROVIDER_DEFAULT

   Ok = RevertToSelf()
   Ok = LogonUser(strAdminUser, strAdminDomain, strAdminPassword,
lngLogonType, lngLogonProvider, lngTokenHandle)
   Ok = ImpersonateLoggedOnUser(lngTokenHandle)

   ValLogon = Ok
Exit Function

ErrorHandler:
    MsgBox Err.Description
End Function

Private Sub cmdOK_Click()
   UserName = txtUserName.Text
   Domain = "tbdomn01"
   Password = txtPassword.Text

   If ValLogon(UserName, Password, Domain) Then
      MsgBox "You're In!!", , "Login"
   Else
      MsgBox "Invalid Password, try again!", , "Login"
   End If
End Sub

Public Sub Form_Load()
Dim sBuffer As String
Dim lSize As Long

   sBuffer = Space$(255)
   lSize = Len(sBuffer)
   Call GetUserName(sBuffer, lSize)
   If lSize > 0 Then
      txtUserName.Text = Left$(sBuffer, lSize)
   Else
      UserName = vbNullString
   End If

End Sub

"The LogonUser API has been available and documented since
Windows NT 3.51, and is commonly used to verify user
credentials. Unfortunately, there are some restrictions on
using LogonUser that are not always convenient to satisfy.
The first and biggest of these restrictions is that the
process calling LogonUser must have the SE_TCB_NAME
privilege (in User Manager, this is the "Act as part of the
Operating System" right). The SE_TCB_NAME privilege is very
powerful and should not be granted to any arbitrary user
just so that they can run an application that needs to
validate credentials. The recommended method is to call
LogonUser from a service running in the local system account
since the local system account already has the SE_TCB_NAME
privilege."

Insert Disclaimer:
Most of the time i think for myself, at least that is what
they tell me.