There's an old ticket discussing CAS authentication:
https://jira.lyrasis.org/browse/DS-1028 Unfortunately though, it has not yet been implemented (to my knowledge) and remains open. That said, if anyone
has build a custom CAS authentication plugin, the DSpace developers are always interested in new contributions.
Currently, there are no plans to add new authentication plugins in v7.x, as that upcoming release concentrates more on a new UI / REST API. So, as of right now, the pre-7.0 codebase uses & support the same authentication plugins as 6.x. (It's always possible
plans could change if a volunteer offers to donate or implement CAS authentication, but it's not currently on the 7.x roadmap.)
Tim