How do we use CAS login screen to authenticate Nginx.

We have deployed front end using EXT JS in Nginx server and Nginx server is using reverse proxy to get the data from JBOSS server (spring MVC rest services).

We have deployed Jasig CAS application in tomcat server and configured our JBOSS server for the CAS Authentication. So far so Good.

Since user is entering the data in EXT JS forms so we are supposed to enable SSL at nginx server level. Also, when user is not logged in, we have to redirect users to the CAS login screen.How do we do that ?

One way is to check for the cookie in nginx for authentication and redirect to cas login screen if cookie is not available. Is it the right way of doing this ?

Do have any user guide for nginx and CAS integration ?