AD Password About to Expire check - asp.net

Question

I am trying to write some code to check the AD password age during a user login and notify them of the 15 remaining days. I am using the ASP.Net code that I found on the Microsoft MSDN site and I managed to add a function that checks the if the account is set to change password at next login. The login and the change password at next login works great but I am having some problems with the check for the password age.
This is the VB.Net code for the DLL file:
Imports System
Imports System.Text
Imports System.Collections
Imports System.DirectoryServices
Imports System.DirectoryServices.AccountManagement
Imports System.Reflection 'Needed by the Password Expiration Class Only -Vince
Namespace FormsAuth
Public Class LdapAuthentication
Dim _path As String
Dim _filterAttribute As String
'Code added for the password expiration added by Vince
Private _domain As DirectoryEntry
Private _passwordAge As TimeSpan = TimeSpan.MinValue
Const UF_DONT_EXPIRE_PASSWD As Integer = &H10000
'Function added by Vince
Public Sub New()
Dim root As New DirectoryEntry("LDAP://rootDSE")
root.AuthenticationType = AuthenticationTypes.Secure
_domain = New DirectoryEntry("LDAP://" & root.Properties("defaultNamingContext")(0).ToString())
_domain.AuthenticationType = AuthenticationTypes.Secure
End Sub
'Function added by Vince
Public ReadOnly Property PasswordAge() As TimeSpan
Get
If _passwordAge = TimeSpan.MinValue Then
Dim ldate As Long = LongFromLargeInteger(_domain.Properties("maxPwdAge")(0))
_passwordAge = TimeSpan.FromTicks(ldate)
End If
Return _passwordAge
End Get
End Property
Public Sub New(ByVal path As String)
_path = path
End Sub
'Function added by Vince
Public Function DoesUserHaveToChangePassword(ByVal userName As String) As Boolean
Dim ctx As PrincipalContext = New PrincipalContext(System.DirectoryServices.AccountManagement.ContextType.Domain)
Dim up = UserPrincipal.FindByIdentity(ctx, userName)
Return (Not up.LastPasswordSet.HasValue)
'returns true if last password set has no value.
End Function
Public Function IsAuthenticated(ByVal domain As String, ByVal username As String, ByVal pwd As String) As Boolean
Dim domainAndUsername As String = domain & "\" & username
Dim entry As DirectoryEntry = New DirectoryEntry(_path, domainAndUsername, pwd)
Try
'Bind to the native AdsObject to force authentication.
Dim obj As Object = entry.NativeObject
Dim search As DirectorySearcher = New DirectorySearcher(entry)
search.Filter = "(SAMAccountName=" & username & ")"
search.PropertiesToLoad.Add("cn")
Dim result As SearchResult = search.FindOne()
If (result Is Nothing) Then
Return False
End If
'Update the new path to the user in the directory.
_path = result.Path
_filterAttribute = CType(result.Properties("cn")(0), String)
Catch ex As Exception
Throw New Exception("Error authenticating user. " & ex.Message)
End Try
Return True
End Function
Public Function GetGroups() As String
Dim search As DirectorySearcher = New DirectorySearcher(_path)
search.Filter = "(cn=" & _filterAttribute & ")"
search.PropertiesToLoad.Add("memberOf")
Dim groupNames As StringBuilder = New StringBuilder()
Try
Dim result As SearchResult = search.FindOne()
Dim propertyCount As Integer = result.Properties("memberOf").Count
Dim dn As String
Dim equalsIndex, commaIndex
Dim propertyCounter As Integer
For propertyCounter = 0 To propertyCount - 1
dn = CType(result.Properties("memberOf")(propertyCounter), String)
equalsIndex = dn.IndexOf("=", 1)
commaIndex = dn.IndexOf(",", 1)
If (equalsIndex = -1) Then
Return Nothing
End If
groupNames.Append(dn.Substring((equalsIndex + 1), (commaIndex - equalsIndex) - 1))
groupNames.Append("|")
Next
Catch ex As Exception
Throw New Exception("Error obtaining group names. " & ex.Message)
End Try
Return groupNames.ToString()
End Function
'Function added by Vince
Public Function WhenExpires(ByVal username As String) As TimeSpan
Dim ds As New DirectorySearcher(_domain)
ds.Filter = [String].Format("(&(objectClass=user)(objectCategory=person)(sAMAccountName={0}))", username)
Dim sr As SearchResult = FindOne(ds)
Dim user As DirectoryEntry = sr.GetDirectoryEntry()
Dim flags As Integer = CInt(user.Properties("userAccountControl").Value)
If Convert.ToBoolean(flags And UF_DONT_EXPIRE_PASSWD) Then
'password never expires
Return TimeSpan.MaxValue
End If
'get when they last set their password
Dim pwdLastSet As DateTime = DateTime.FromFileTime(LongFromLargeInteger(user.Properties("pwdLastSet").Value))
' return pwdLastSet.Add(PasswordAge).Subtract(DateTime.Now);
If pwdLastSet.Subtract(PasswordAge).CompareTo(DateTime.Now) > 0 Then
Return pwdLastSet.Subtract(PasswordAge).Subtract(DateTime.Now)
Else
Return TimeSpan.MinValue
'already expired
End If
End Function
'Function added by Vince
Private Function LongFromLargeInteger(ByVal largeInteger As Object) As Long
Dim type As System.Type = largeInteger.[GetType]()
Dim highPart As Integer = CInt(type.InvokeMember("HighPart", BindingFlags.GetProperty, Nothing, largeInteger, Nothing))
Dim lowPart As Integer = CInt(type.InvokeMember("LowPart", BindingFlags.GetProperty, Nothing, largeInteger, Nothing))
Return CLng(highPart) << 32 Or CUInt(lowPart)
End Function
'Function added by Vince
Private Function FindOne(ByVal searcher As DirectorySearcher) As SearchResult
Dim sr As SearchResult = Nothing
Dim src As SearchResultCollection = searcher.FindAll()
If src.Count > 0 Then
sr = src(0)
End If
src.Dispose()
Return sr
End Function
End Class
End Namespace
And this is the Login.aspx page:
sub Login_Click(sender as object,e as EventArgs)
Dim adPath As String = "LDAP://DC=xxx,DC=com" 'Path to your LDAP directory server
Dim adAuth As LdapAuthentication = New LdapAuthentication(adPath)
Try
If (True = adAuth.DoesUserHaveToChangePassword(txtUsername.Text)) Then
Response.Redirect("passchange.htm")
ElseIf (True = adAuth.IsAuthenticated(txtDomain.Text, txtUsername.Text, txtPassword.Text)) Then
Dim groups As String = adAuth.GetGroups()
'Create the ticket, and add the groups.
Dim isCookiePersistent As Boolean = chkPersist.Checked
Dim authTicket As FormsAuthenticationTicket = New FormsAuthenticationTicket(1, _
txtUsername.Text, DateTime.Now, DateTime.Now.AddMinutes(60), isCookiePersistent, groups)
'Encrypt the ticket.
Dim encryptedTicket As String = FormsAuthentication.Encrypt(authTicket)
'Create a cookie, and then add the encrypted ticket to the cookie as data.
Dim authCookie As HttpCookie = New HttpCookie(FormsAuthentication.FormsCookieName, encryptedTicket)
If (isCookiePersistent = True) Then
authCookie.Expires = authTicket.Expiration
End If
'Add the cookie to the outgoing cookies collection.
Response.Cookies.Add(authCookie)
'Retrieve the password life
Dim t As TimeSpan = adAuth.WhenExpires(txtUsername.Text)
'You can redirect now.
If (passAge.Days = 90) Then
errorLabel.Text = "Your password will expire in " & DateTime.Now.Subtract(t)
'errorLabel.Text = "This is"
'System.Threading.Thread.Sleep(5000)
Response.Redirect("http://somepage.aspx")
Else
Response.Redirect(FormsAuthentication.GetRedirectUrl(txtUsername.Text, False))
End If
Else
errorLabel.Text = "Authentication did not succeed. Check user name and password."
End If
Catch ex As Exception
errorLabel.Text = "Error authenticating. " & ex.Message
End Try
End Sub
`
Every time I have this Dim t As TimeSpan = adAuth.WhenExpires(txtUsername.Text) enabled, I receive "Arithmetic operation resulted in an overflow." during the login and won't continue.
What am I doing wrong? How can I correct this? Please help!!
Thank you very much for any help in advance.
Vince
Ok I tried to use a different approach.
Here are the functions converted from C#:
Public Function PassAboutToExpire(ByVal userName As String) As Integer
Dim passwordAge As TimeSpan
Dim currentDate As DateTime
Dim ctx As PrincipalContext = New PrincipalContext(System.DirectoryServices.AccountManagement.ContextType.Domain)
Dim up = UserPrincipal.FindByIdentity(ctx, userName)
'Return (Not up.LastPasswordSet.HasValue)
'returns true if last password set has no value.
Dim pwdLastSet As DateTime = DateTime.FromFileTime(LongFromLargeInteger(up.LastPasswordSet))
currentDate = Now
passwordAge = currentDate.Subtract(pwdLastSet)
If passwordAge.Days > 75 Then
'If pwdLastSet.Subtract(passwordAge).CompareTo(DateTime.Now) > 0 Then
'Dim value As TimeSpan = pwdLastSet.Subtract(passwordAge).Subtract(DateTime.Now)
'If (value.Days > 75) Then
Return passwordAge.Days
'End If
Else
Return False
'already expired
End If
End Function
Private Function LongFromLargeInteger(ByVal largeInteger As Object) As Long
Dim type As System.Type = largeInteger.[GetType]()
Dim highPart As Integer = CInt(type.InvokeMember("HighPart", BindingFlags.GetProperty, Nothing, largeInteger, Nothing))
Dim lowPart As Integer = CInt(type.InvokeMember("LowPart", BindingFlags.GetProperty, Nothing, largeInteger, Nothing))
Return CLng(highPart) << 32 Or CUInt(lowPart)
End Function
And here is the code snippet from the logon.aspx page:
sub Login_Click(sender as object,e as EventArgs)
Dim adPath As String = "LDAP://DC=xzone,DC=com" 'Path to your LDAP directory server
Dim adAuth As LdapAuthentication = New LdapAuthentication(adPath)
Try
If (True = adAuth.DoesUserHaveToChangePassword(txtUsername.Text)) Then
Response.Redirect("http://mypass.nsu.edu")
ElseIf (adAuth.PassAboutToExpire(txtUsername.Text) > 0) Then
Response.Redirect("http://www.yahoo.com")
Now when I try to login I receive the exception error: Error authenticating. Method 'System.DateTime.HighPart' not found.
and I don't know why. Anyone has any idea?

Answer 1

I would use the DateDiff function to determine the remaining number of days rather than using currentDate.Subtract
Dim passwordAge As Integer = (CInt)DateDiff(DateInterval.Day, Now, up.LastPasswordSet))
That will return an integer representing the number of days between now and when the password will need to be set.