This is my scenario:

1. User tries to reach ServiceA or B
2. ServiceA throws an exception(user does not have sso session yet) and redirects User to Cas web form for user input credentials
3. User have a choose, to enter username/password in the CAS form or click the link to reach external identity provider portal.
4. If user chooses External Identity Provider (EIDP), the user will be redirected to new web page of EIDP for user credentials input. I put redirectURL after success EIDP identificaiton.
5. If success identification in EIDP: user will be redirected to redirectURL (for example to serviceA, to serviceB or to my Custom Authentication Service).
   The EIDP provides ticket in redirect URL to retrieve User Details later.
   I need here to create new user in DB or if user exists- immediately authenticate via CAS (to create sso session and redirect to Service(A,B)). For that purpose i have created my Custom Authentication Service.

My questions is:

1. How to create Cas SSO session via Custom Authentication Service? I’m using here CAS REST API. Maybe it is wrong idea
2. How to separate CAS login form username/password and REST API authentication to use different CAS Authentication handlers.