ASP.NET MVC 2 and authentication using WIF (Windows Identity Foundation)

Question

Are there any decent examples of the following available:

Looking through the WIF SDK, there are examples of using WIF in conjunction with ASP.NET using the WSFederationAuthenticationModule (FAM) to redirect to an ASP.NET site thin skin on top of a Security Token Service (STS) that user uses to authenticate (via supplying a username and password).

If I understand WIF and claims-based access correctly, I would like my application to provide its own login screen where users provide their username and password and let this delegate to an STS for authentication, sending the login details to an endpoint via a security standard (WS-*), and expecting a SAML token to be returned. Ideally, the SessionAuthenticationModule would work as per the examples using FAM in conjunction with SessionAuthenticationModule i.e. be responsible for reconstructing the IClaimsPrincipal from the session security chunked cookie and redirecting to my application login page when the security session expires.

Is what I describe possible using FAM and SessionAuthenticationModule with appropriate web.config settings, or do I need to think about writing a HttpModule myself to handle this? Alternatively, is redirecting to a thin web site STS where users log in the de facto approach in a passive requestor scenario?

Answer 1

That's an interesting question you've asked. I know that for whatever reason, Microsoft put out this "Windows Identity Foundation" framework without much documentation. I know this because I've been tasked with figuring out how to use it with a new project and integrating it with existing infrastructure. I've been searching the web for months looking for good information.

I've taken a somewhat different angle to solving the problem you describe.

I took an existing log-on application and integrated Microsoft's WIF plumbing into it. By that, I mean that I have an application where a user logs in. The log-on application submits the credentials supplied by the user to another server which returns the users identity (or indicates log-on failure).

Looking at some of Microsoft's examples, I see that they do the following: Construct a SignInRequestMessage from a querystring (generated by a relying party application), construct a security token service from a custom class, and finally call FederatedSecurityTokenServiceOperations.ProcessSignInresponse with the current httpcontext.response. Unfortunately, I can't really explain it well here; you really need to look at the code samples.

Some of my code is very similar to the code sample. Where you're going to be interested in implementing a lot of your own logic is in the GetOutputClaimsIdentity. This is the function that constructs the claims-identity that describes the logged-in user.

Now, here's what I think you're really interested in knowing. This is what Microsoft doesn't tell you in their documentation, AFAIK.

Once the user logs in, they are redirected back to the relying party application. Regardless of how the log-on application works, the WIF classes will send a response to the user's browser that contains a "hidden" HTML input that contains the token signing certificate and the user's claims. (The claims will be in clear text). At the end of this response is a redirect to your relying-party website. I only know about this action because I captured it with "Fiddler"

Once back at the relying party web site, the WIF classes will handle the response (before any of your code is run). The certificate will be validated. By default, if you've set up your relying party web site with FedUtil.exe (by clicking "Add STS Reference in your relying party application from Visual Studio), Microsoft's class will verify the certificate thumbprint.

Finally, the WIF framework sets cookies in the user's browser (In my experience, the cookie names start out with "FedAuth") that contain the users claims. The cookies are not human readable.

Once that happens, you may optionally perform operations on the user's claims within the relying party website using the ClaimsAuthenticationClass. This is where your code is running again.

I know this is different from what you describe, but I have this setup working. I hope this helps!

ps. Please check out the other questions I've asked about Windows Identity Foundation.

UPDATE: To answer question in comment below:

One thing that I left out is that redirection to the STS log-on application happens by way of a redirect with a query-string containing the URL of the application the user is logging in to. This redirect happens automatically the first time a user tries to access a page that requires authentication. Alternatively, I believe that you could do the redirect manually with the WSFederationAuthentication module.

I've never tried to do this, but if you want to use a log-on page within the application itself, I believe the framework should allow you to use the following:

1) Encapsulate your STS code within a library. 2) Reference the library from your application. 3) Create a log-on page within your application. Make sure that such page does not require authentication. 4) Set the issuer property of the wsFederation element within the Microsoft.IdentityModel section of your web.config to the login page.

Answer 2

An example of WIF + MVC is available in this chapter of the "Claims Identity Guide":

http: //msdn.microsoft.com/en-us/library/ff359105.aspx

I do suggest reading the first couple chapters to undertsand all underlying principles. This blog post covers the specifics of MVC + WIF:

http://blogs.msdn.com/b/eugeniop/archive/2010/04/03/wif-and-mvc-how-it-works.aspx

Controlling the login experience is perfectly fine. You should just deploy your own STS (in your domain, with your look & feel, etc). Your apps would simply rely on it for AuthN (that's why a app is usually called a "relying party").

The advantage of the architecture is that authN is delegated to 1 component (the STS) and not spread out throughout many apps. But the other (huge) advantage is that you can enable more spohisticated scenarios very easily. For example you can now federate with other organization's identity providers.

Hope it helps Eugenio

@RisingStar:

The token (containing the claims) can be optionally encrypted (otherwise they will be in clear text). That's why SSL is always recommended for interactions between the browser and the STS.

Notice that even though they are in clear text, tampering is not possible because the token is digitally signed.

Answer 3

What you want to do is an active signin. WIF includes WSTrustChannel(Factory) which allows you to communicate directly with the STS and obtain a security token. If you want your login form to work this way, you can follow the "WSTrustChannel" sample from the WIF 4.0 SDK. Once you have obtained the token, the following code will take that token and call the WIF handler to create a session token and set the appropriate cookie:

public void EstablishAuthSession(GenericXmlSecurityToken genericToken)
{
    var handlers = FederatedAuthentication.ServiceConfiguration.SecurityTokenHandlers;            
    var token = handlers.ReadToken(new XmlTextReader(
                                        new StringReader(genericToken.TokenXml.OuterXml)));

    var identity = handlers.ValidateToken(token).First();
    // create session token
    var sessionToken = new SessionSecurityToken(
        ClaimsPrincipal.CreateFromIdentity(identity));
    FederatedAuthentication.SessionAuthenticationModule.WriteSessionTokenToCookie(sessionToken);
}

Once you have done this, your site ought to behave the same as if passive signing had occurred.

Answer 4

You could use the FederatedPassiveSignIn Control.