A Rack Middleware component to authenticate against a CAS server. I (shamefully) forgot to attribute this to https://github.com/garnieretienne/rubycas-client-sinatra. I had reached out to garnieretienne and he was no longer interested in his project. There is also rack-cas-client gem but that was too rails focused for me.
Gemfile gem 'rack-cas_client', '~> 0.3.0'
install gem install rack-cas_client