“The specified domain either does not exist or could not be contacted”

Question

I'm trying to use Integrated Windows Authentication combined with a DirectorySearcher to identify and authenticate the intranet user.

I'd managed to get some fairly simple code that seemed to do the trick, but when I tried on the live server I get the following error:

"The specified domain either does not exist or could not be contacted"

I can't debug the app on the live server so I copied it across to an old development server to test there. When I ran the app normally, it came up with the same error, so the I tried debugging in VS.... except it worked perfectly.

I suspect it's something to do with impersonation or to do with the LDAP call - obviously when it works for the debugger it's hard to be sure what the real problem is.

But I figured one of you guys will be able to point me in the right direction.

Snippets from my authentication class:

Private Function GetUserID() As String
    Dim sID As String = HttpContext.Current.User.Identity.Name
    Return Mid(sID, InStr(sID, "\") + 1)
End Function

Private Function GetDisplayName() As String
    Dim oSearcher As New DirectorySearcher
    Dim oResult As SearchResult
    Dim sName As String = String.Empty

    With oSearcher
        .Filter = String.Format("(SAMAccountName={0})", _UserID)
        .PropertiesToLoad.Add("displayName")
        oResult = .FindOne()
        If Not oResult Is Nothing Then
            sName = oResult.Properties("displayName")(0).ToString()
        End If
    End With

    Return sName
End Function
Private Function GetEmail() As String
    Dim oSearcher As New DirectorySearcher
    Dim oResult As SearchResult
    Dim sEmail As String = String.Empty

    With oSearcher
        .Filter = String.Format("(SAMAccountName={0})", _UserID)
        .PropertiesToLoad.Add("mail")
        oResult = .FindOne()
        If Not oResult Is Nothing Then
            sEmail = oResult.Properties("mail")(0).ToString()
        End If
    End With

    Return sEmail

End Function

Private Function GetGroups() As StringCollection
    Dim oSearcher As New DirectorySearcher
    Dim oResult As SearchResult
    Dim colGroups As New StringCollection
    Dim i As Int16

    With oSearcher
        .Filter = String.Format("(cn=" & _UserName & ")", _UserID)
        .PropertiesToLoad.Add("memberOf")
        oResult = .FindOne()

        If Not oResult Is Nothing Then
            Dim iGroupCount As Int16 = oResult.Properties("memberOf").Count

            For i = 0 To iGroupCount - 1
                colGroups.Add(oResult.Properties("memberOf")(i).ToString())
            Next

        End If
    End With

    Return colGroups
End Function

Answer 1

I've found it much easier to use the System.DirectoryServices.AccountManagement namespace for this kind of thing, in your case the UserPrincipal class is your friend.

Private Function GetEmail() As String
        Dim pc As PrincipalContext = new PrincipalContext(ContextType.Domain)
        Dim wi As WindowsIdentity = HttpContext.Current.User.Identity
        Dim up As UserPrincipal = UserPrincipal.FindByIdentity(pc, wi.Name)

        Return up.EmailAddress
End Function

Answer 2

I once had the same problem and I figured out that the cause of error was the way the url was written.

When using AD and ADSI ensure you are using "UPPER CASE" paths. As I can see from your code you are writing "cn" as lower case. [GetGroups function]

Another way I would try is to ensure that you are making a proper use of the "connectionstring" you are using.

LDAP://CN=" + username + ",OU=" + OU + ",OU=myOU,DC=myDC1,DC=myDC2";

becomes

LDAP://orgname.ad.root/CN=" + username + ",OU=" + OU + ",OU=myOU,DC=myDC1,DC=myDC2";

where "orgname" it's the server name where AD is running on.

Hope this helps.

Answer 3

Here is another way of achieving the same functionality:

string fullPath = "LDAP://abc.xyz.com/DC=xyz, DC=com";
AuthenticationTypes authType = AuthenticationTypes.None;
DirectoryEntry verifiedUser = new DirectoryEntry(fullPath, txtUserName.Text.Trim(), txtPassword.Text.Trim(), authType);
verifiedUser.RefreshCache();
isAuthorisedUser = true;

This worked for me.