Scenario: I want to use Craft to build a community website for an organisation which uses LDAP and Google Apps. I'd like to users to be able to login to Craft Admin via their existing LDAP account (or via Google Apps OAuth, which is easier).
The ideal workflow would be something like this: 1. John Doe is a member of the community and requests access to the Craft site. 2. Admin user logs into Craft and adds John Doe as a new user with his SSO email address 3. John Doe can then login to Craft using his SSO login details (either via a custom front-end form, or directly via Craft admin).
Looking at the available Craft events & hooks, this doesn't seem possible currently without hacking up the Craft internals.
My question: Is there any way to implement this sort of SSO in a modular fashion in Craft? Or, will it require extensive hacking of Craft internals in a 'brittle' fashion?