Grails Spring Security (Acegi) plugin intercept login to inject custom Facebook Connect logic

Ok, second try here.. hoping I phrase my question better to get a few responses.

I am currently working on a small project developed in Grails with the Spring Security plugin to handle account management and security. I want to intercept the login function and add some custom code. The goal is to have 2 options available to the end user for registration, the default spring security/application option and the other using facebook connect.

I did notice and read up on the facebook connect features in Spring Security but to me, it doesnt seem to fit my requirements exactly. I cannot assign permissions/roles to these facebook connect users if I were to use the default facebook connect features in Spring Security开发者_JAVA百科. Anyone else run into this?

How can I intercept the login function? There is an auth method in Login but thats not exactly where I think I need to inject my own custom business logic. Any help with this would be most appreciated.