David Castro posted some documentation to the CAS discussion list about his excellent Apache::AuthCAS mod_perl module. Slightly edited for this venue, it is reproduced below. See also the CPAN documentation.
Apache::AuthCAS is a mod_perl module for Apache that can be declaratively configured and does support proxy tickets. This module is written in perl and does not require any compilation against Apache source (which can be a pain). It only requires that mod_perl be installed on the Apache server. As for its usefulness, I will give a couple examples below.
One has an application that cannot be modified itself (due to inability, preference, or the desire for sanity), but wants to make this application available only to centrally authenticated users. We did this for an online faculty/staff directory running on FileMaker Pro (sigh).
This module was created as a solution to needs we had during our CAS implementation at APU. We have many applications that are not written in Java and didn't want to integrate any of the custom CAS client bindings into them. This mechanism is much simpler for maintenance and also gives us some unique options.
For instance, we want to allow departments the ability to restrict some of their web content to others in the university. We simply configure
Currently, a database to store session data and pgt/pgtiou mappings is required, as getting data shared between Apache processes is a little tricky and you never know which process/thread is going to serve your request. This configuration was also desirable, because we can restart Apache without destroying existing sessions.
I hope this helps to explain Apache::AuthCAS a bit more. Please send me any questions and I will clarify or explain anything I didn't cover.
I am sure this diagram is similar to others that exist, however, this helped me wrap my head around CAS and proxy tickets for this implementation. Feedback is greatly appreciated, and I am willing to make adjustments to the module for anyone needing them (so long as they are generally useful to the community).