Out of the box, Sitecore only offers their own forms-based authentication provider, which requires to add every user to the Sitecore membership database. At Achmea, we had the requirement to facilitate login via ADFS, as we are using our user accounts amongst different systems, web applications and apps. In addition to the absence of this functionality, it’s not possible to work with claims as well.
This blogpost describes how to add and use the Federated Authentication middleware using OWIN in combination with Sitecore and how to access the claims that are provided using the federated login. The solution supports a multi-site scenario, which can handle different identity providers and multiple realms. This opens up possibilities to use external identity providers, for example via ADFS or Windows Azure Active Directory.
The source code for federated login component can be found on github. Please feel free to contact me via twitter/mail/github if there are any questions! A special thanksto Kern Herskind Nightingale of Sitecore: We discussed a lot on the integration patterns for Federation and Sitecore.