Hi, we are trying to implement DUO with Shibboleth and CAS and are having issues with the integration to work. Shibboleth initiates the DUO workflow but the integration does not work. Has anyone successfully implemented DUO with Shibboleth and CAS, where CAS is the authentication source (Shibboleth forwards authentication requests to CAS).
As a general rule of thumb, Duo should be invoked at the point of authentication, so in your case, CAS.
Hope this helps!