Implement Office 365 styled Basic Authentication (Active Profile)

I'm working on a SaaS application built around ASP.net MVC & WebAPI and want to make it easy for enterprises to use my service. Example would be Office 365 Basic Authentication (Active Profile) where the user enters his username/password on microsoft's site (or desktop app) and he is authenticated against his employer's Active Directory. My understanding so far is that I would need to create a RP-STS which will accept credentials and then forward those to AD FS Proxy running on the client company's AD server. Is this correct?

If yes, then how do I implement this? Setting up AD server adding a Relying Party and AD FS Proxy Role is easy, so that's really not an issue. I just need to figure out how to create/setup RP-STS service and any other steps involved in this process. There just isn't an example/tutorial of this in .net

Solution

I believe this msdn blog post describes exactly what you're asking for. It has a complete walkthrough of the entire process, including creating an RP by creating a normal WCF service, and then use the provided utility to configure the service to trust your ADFS.

http://blogs.msdn.com/b/mcsuksoldev/archive/2011/08/17/federated-security-how-to-setup-and-call-a-wcf-service-secured-by-adfs-2-0.aspx

Edit:

This code, taken from the linked article (comments are mine), is a demonstration of active federation. The client application is manually retrieving a security token from the ADFS. Passive Federation would involve forwarding the user to a secure web page in which they could send their credentials directly to the ADFS. The major benefit of Passive Federation is that the end user's secret credentials are provided directly to the ADFS, and the RP's client side code never has access to it.

var requestTokenResponse = new RequestSecurityTokenResponse();

//The line below is the 'Active' federation
var token = Token.GetToken(@"mydomain\testuser", "p@ssw0rd", "http://services.testdomain.dev/wcfservice/Service.svc", out requestTokenResponse);

var wcfClient = new FederatedWCFClient<MyTestService.IService>(token, "WS2007FederationHttpBinding_IService");   // This must match the app.config
var client = wcfClient.Client as MyTestService.IService;
var result = client.GetData();
Console.WriteLine(result);
wcfClient.Close();