We have very similar needs (minus Open ID) here at Virginia Tech, and we use CAS as the authentication provider for Shib, http://www.ja-sig.org/wiki/display/CASUM/Shibboleth-CAS+Integration. This way you can use CAS for internal SSO needs and Shib for external SSO. Although the two SSO domains are not unified in this integration strategy, for us that's a benefit rather than a liability.
I don't see any need for CASShib in anything you wrote. If you want to go that route, you're in much less supported territory as far as I can tell. M -- You are currently subscribed to [email protected] as: [email protected] To unsubscribe, change settings or access archives, see http://www.ja-sig.org/wiki/display/JSG/cas-user
