Extend authentication logic in a Spring Security + Waffle application

Question

I'm using Waffle to implement ActiveDirectory single sign-on in a Spring Web application.

I'm also using Spring Security and I followed this tutorial to integrate these libraries.

Now I need to customize authentication behaviour like I've done and described in an old question: Spring Security: how to map Active Directory users to application users?

I basically need to allow authentication for registered users only and to map AD users to application users.

To achieve this I need to extend some AuthenticationProvider and UserDetailsContextMapper, but I cannot find anything similar in Waffle implementation.

So, how can I solve my issue? Is there some other approach to add logic in the authentication and authorization chain when using Waffle?