Integrated Authentication on Webserver - Security?

Question

We have our own web server hosting our website that is open to the public outside of our network.

I have a request to make our "Internal Postings" link on our Careers page to authenticate the user against our network's Active Directory list.

I currently have it setup so the link hits a page inside the directory structure of the website, and this page's folder is set to "Integrated Windows Authentication". Anonymous access is turned off for this page. If the user is authenticated (ie: logged into our network or supplies proper credentials) it passes them on to an external careers website which hosts our job postings. If they fail to authenticate, it displays a custom 401 error page.

This works fine, but there is a problem with it. Using IE, people cannot just enter their username. They (of course) are required to enter the domain name as well. Unfortunately the default 'domain' is set to the URL of our website (www.xyz.com/username). I would like it to automatically choose the name of our internal domain (aaa/username) but am unsure of how to do this.

Another option would be to use LDAP and a little ASP scripting to authenticate the user. I have this code already, but am unsure of the security consequences of doing so. Basically, the page will be setup for anonymous authentication, and if the user isn't logged into our network, they will be prompted for a username/password using standard textboxes. This is then passed to an ASP script that does an LDAP lookup against our Active Directory. Is there any security issues with this method?

Which method would you choose to do?

Thanks.

EDIT: It seems I cannot authenticate to ActiveD via LDAP using a username/password combo. So forget about that option.

My question now is, how can I change the default 'domain' that IWA uses? Is that at all possible? IE seems to default to 'www.xyz.com\username' (my website) rather than 'aaa\username' (my domain name). Of course, www.xyz.com\username fails because that is not where our ActiveD resides... Is this possible? I want to make it as simple as possible for our employees.

Answer 1

You cannot authenticate an user with a script that looks up the user in LDAP. You need to know that the user is who it claims it is, and the only way to do that is to let NTLM/Kerberos authenticate the user (ie. establish proof that the user knows a secret stored in the AD, the password).

Answer 2

The URL of the web site to the set of sites considered be in the local intranet zone for IE browsers running on the internal network. By default sites consider to local intranet will be sent the current logged on users credentials when challanged with NTLM/Kerberos. Hence your internal users shouldn't even see a network logon box.