Hello, I was wondering if someone can help me understand something. Below is
some code that I got from the MS website that is suppose to authenticate for
the username and password on the local machine. I tested this code in VB.net
2003 in a WINDOW FORM class and it seems to work fine. However, when I test
it in VB.net 2005 Express Edition it works for the login portion but it
doesn't display the error message if the user name and password is incorrect,
it doesn't do anything:
Imports System.Security.Principal
Imports System.Security.Permissions
Imports System.Runtime.InteropServices
Imports System.Environment
'The LogonUser function tries to log on to the local computer
'by using the specified user name. The function authenticates
'the Windows user with the password provided.
Private Declare Auto Function LogonUser 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 Boolean
'The FormatMessage function formats a message string that is passed as
input.
<DllImport("kernel32.dll")> _
Public Shared Function FormatMessage(ByVal dwFlags As Integer, ByRef
lpSource As IntPtr, _
ByVal dwMessageId As Integer, ByVal dwLanguageId As Integer, ByRef
lpBuffer As [String], _
ByVal nSize As Integer, ByRef Arguments As IntPtr) As Integer
End Function
'The CloseHandle function closes the handle to an open object such as an
Access token.
Public Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal
handle As IntPtr) As Boolean
'The GetErrorMessage function formats and then returns an error message
'that corresponds to the input error code.
Public Shared Function GetErrorMessage(ByVal errorCode As Integer) As
String
Dim FORMAT_MESSAGE_ALLOCATE_BUFFER As Integer = &H100
Dim FORMAT_MESSAGE_IGNORE_INSERTS As Integer = &H200
Dim FORMAT_MESSAGE_FROM_SYSTEM As Integer = &H1000
Dim msgSize As Integer = 255
Dim lpMsgBuf As String
Dim dwFlags As Integer = FORMAT_MESSAGE_ALLOCATE_BUFFER Or
FORMAT_MESSAGE_FROM_SYSTEM Or FORMAT_MESSAGE_IGNORE_INSERTS
Dim lpSource As IntPtr = IntPtr.Zero
Dim lpArguments As IntPtr = IntPtr.Zero
'Call the FormatMessage function to format the message.
Dim returnVal As Integer = FormatMessage(dwFlags, lpSource,
errorCode, 0, lpMsgBuf, _
msgSize, lpArguments)
If returnVal = 0 Then
Throw New Exception("Failed to format message for error code " +
errorCode.ToString() + ". ")
End If
Return lpMsgBuf
End Function
Private Sub Button1_Click(ByVal sender As Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim tokenHandle As New IntPtr(0)
Try
Dim UserName, MachineName, Pwd As String
'The MachineName property gets the name of your computer.
MachineName = System.Environment.MachineName
UserName = TextBox1.Text
Pwd = TextBox2.Text
Dim frm2 As New Form2
Const LOGON32_PROVIDER_DEFAULT As Integer = 0
Const LOGON32_LOGON_INTERACTIVE As Integer = 2
tokenHandle = IntPtr.Zero
'Call the LogonUser function to obtain a handle to an access
token.
Dim returnValue As Boolean = LogonUser(UserName, MachineName,
Pwd, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, tokenHandle)
If returnValue = False Then
'This function returns the error code that the last
unmanaged function returned.
Dim ret As Integer = Marshal.GetLastWin32Error()
Dim errmsg As String = GetErrorMessage(ret)
frm2.Show()
frm2.Label1.Text = errmsg
frm2.Button1.Visible = False
Else
'Create the WindowsIdentity object for the Windows user
account that is
'represented by the tokenHandle token.
Dim newId As New WindowsIdentity(tokenHandle)
Dim userperm As New WindowsPrincipal(newId)
'Verify whether the Windows user has administrative
credentials.
If userperm.IsInRole(WindowsBuiltInRole.Administrator ) Then
frm2.Button1.Text = "Add Numbers"
frm2.Label1.Text = "Click this button to add two numbers"
frm2.Show()
Else
frm2.Label1.Text = " You do not have administrative
credentials."
frm2.Button1.Visible = False
frm2.Show()
End If
End If
'Free the access token.
If Not System.IntPtr.op_Equality(tokenHandle, IntPtr.Zero) Then
CloseHandle(tokenHandle)
End If
Catch ex As Exception
MessageBox.Show("Exception occurred. " + ex.Message)
End Try
End Sub
--
TC
