I'm having trouble discovering exactly what I need to implement in order to use a custom authentication method with my web application using Spring Security. I have a Grails application with the Spring Security plugin that currently uses the standard user/password authentication with a browser form. This is working correctly.
I need to implement a mechanism alongside of this that implements a type of MAC authentication. If the HTTP request contains several parameters (e.g. a user identifier, timestamp, signature, etc.) I need to take those parameters, perform some hashing and signature/timestamp comparisons, and then authenticate the user.
I'm not 100% sure where to start with this. What Spring Security classes do I need to extend/implement? I have read the Reference Documentation and have an okay understanding of the concepts, but am not really sure if I need a Filter or Provider or Manager, or where/how exactly to create Authentication objects. I've messed around trying to extend AbstractProcessingFilter and/or implement AuthenticationProvider, but I just get caught up understanding how I make them all play nicely.