Active directory and LDAP libraries

I am trying to authenticate users to active directory with the Novell.Directory.Ldap libraries found in Mono. I know there is better ways than below, but given that I'm confined to Mono, these are the only supported routines as best I can see.

Using the .NET libraries, I can authenticate a user with their samAccountName.

using (DirectoryEntry de = new DirectoryEntry())
                {
 开发者_运维百科                   de.Username = username;
                    de.Password = password;
                    de.Path = string.Format("LDAP://{0}/{1}", ADHostname, DefaultNamingContext);
                    de.AuthenticationType = AuthenticationTypes.Secure;

                    using (DirectorySearcher deSearch = new DirectorySearcher())
                    {
                        deSearch.SearchRoot = de;
                        deSearch.PropertiesToLoad.Add("cn");
                        deSearch.Filter = "(&(objectCatagory=person))";

                        deSearch.FindOne();
                    }
                }

but this fails with invalid credentials if it's running inside mono. The only way to make it work is by specifying the UPN for username:

de.Username = "foo@my.domain.com";

The problem is, UPN is not a required attribute for AD. So how can I authenticate a user with just their username?

I see a post about one way to do it: Authenticating user using LDAP from PHP

But, it's a chicken and egg problem. How do I bind to search for the users DN so I can bind, if I can't bind as an authenticated user to begin with.

Thank you for any help you can give.

Usually you get an account for your application to allow the search for other user DN's. Traditionally this was done using an anonymous bind, but nowadays that is usually blocked for security reasons.

Therefore get a service account with a known DN and password. Bind as that service account, do your search, then bind as the users DN that you found via the search.