ASP.NET - Detect if user is authenticated with Active Directory?

Question

We have a SSO solution with ADFS for logging into our web app, we also have standard setup that uses authentication with our database. I want to setup a solution that allows for both. So now I am trying to figure out, is there any way for ASP.NET to detect if a user is authenticated with Active Directory so I could do this on the fly? If user is logged in through AD, send through ADFS, else, show login screen. Any idea?

I also realize that this may not work if they are setup to use forms based authentication only after the ADFS process is started.

Answer 1

Yes... In IIS, enable both integrated authentication, basic, and anonymous. All the real work is done in HTTPModule that are registered in the root Web.config (eg in the runtime CONFIG folder). The built-in Authentication HTTPModule will set the user Principle once authenticated if authenticated via integrated credentials. You can add your own to be fired after it. If the IIdentity (eg User.Identity) has the IsAuthenticated set to false then you know they were not authenticated and can then redirect them. If it is set to true, you can then replace the IPrinciple with one that contains roles that are germane to your application.