This particular gist it to make sure your CAS backed application is intercepting the Sign Out request for all your Rails applications which been using devise+CAS Authenticable Module for sign in and sign out. To use this We first need to place the single_sign_out.rb file in our lib folder. And then just include this SingleSignOut in your applica…

application_controller.rb

class ApplicationController < ActionController::Base
  require "single_sign_out"
  before_filter :authenticate_user! 
  
  include SingleSignOut

  #NOTE: Define this will inspect logger info of paramenter,controller name and action
  def print_logger_info parameter
    logger.info "######{" Controller : "+params[:controller]+" "}#################{" Action : "+params[:action]+" "}###########{" Parameters : "+parameter.inspect+" "}#############}" if Rails.env.development?
    logger.info "###=>>>>>>>>>>>>>>>>>>session['cas_last_valid_ticket']###{session['cas_last_valid_ticket'].inspect}"
    logger.info "######=>>>>>>>>>>>>>>>>>>session inspect###{session.inspect}"
    logger.info "######=>>>>>>>>>>>>>>>>>>current_user.inspect ###{current_user.inspect}"
  end
end

single_sign_out.rb

module SingleSignOut

  def self.included(base)
    base.send(:before_filter, :check_url)
    #base.send(:after_filter, :another_method)
  end

  def check_url
    logger.debug "!!!!!!!!!=>>>>>>>> request.session_options[:id] <<<<<<< #{request.session_options[:id]} "
    logger.debug "Intercepted check_url request for CAS session #{params.inspect}. #{session.inspect}"
    logger.debug "Intercepted Devise CasSessions get/post  request for CAS session #{params.inspect}."
    ticket = read_ticket(session)
    session_id = read_session_id
    logger.debug "Intercepted Devise CasSessions get/post  request for CAS session session_id =>>>>#{session_id} ticket =>>>>> #{ticket}."
    if ticket
      store_session_id_for_index(ticket, session_id)
    end
  end

  def store_session_id_for_index(session_index, session_id)
    logger.debug("Storing #{session_id} for index #{session_index}")
    cache = Rails.cache.write(cache_key(session_index), session_id) #unless session_index_exist(session_index)
    logger.debug("Stored #{cache.inspect} for index #{session_index}")
  end

  #NOTE:define This method returns the session_id of the application for the user stored in Rails cache by devise.
  def find_session_id_by_index(session_index)
    sid = Rails.cache.read(cache_key(session_index))
    logger.debug("Found session id #{sid} for index #{session_index}")
    sid
  end


  #NOTE:define This method destroys the cas and devise session for the current user.
  def destroy_cas_session(session_id, session_index)
    if session = Rails.application.config.session_store.session_class.where(:_id => session_id)
      logger.debug("Deleting session #{session.inspect}")
      session.destroy
    end
    logger.debug("Deleting index #{session_index}")
    delete_session_index(session_index)
  end

  #NOTE:define This methods accepts the params from the request and return the SessionIndex value(name of cas ticket).
  def read_session_index
    if request.headers['CONTENT_TYPE'] =~ %r{^multipart/}
      false
    elsif request.post? && params['logoutRequest'] =~
        %r{^<samlp:LogoutRequest.*?<samlp:SessionIndex>(.*)</samlp:SessionIndex>}m
      $~[1]
    else
      false
    end
  end

  private

  #NOTE:define This method destroys Rails cache current user.
  def delete_session_index(session_index)
    logger.debug("Deleting index 2 #{session_index}")
    Rails.cache.delete(cache_key(session_index))
  end

  #NOTE:define This method returns the present mongoid session for the app from mongoid-store.
  def read_session_id
    session_id = request.session_options[:id]
  end

  #NOTE:define This method checks the cas and devise session is already present/created.
  def session_index_exist(session_index)
    logger.debug("Searching index #{session_index}")
    Rails.cache.exist?(cache_key(session_index))
  end

  #NOTE:define this method prepare and return the cas session filename,
  #     in which session_id is stored for that cas ticket.
  def cache_key(session_index)
    "devise_cas_authenticatable:#{session_index}"
  end

  #NOTE:define This methods accepts the params from the request and return the SessionIndex value(name of cas ticket).
  def read_ticket(params)
    logger.debug("read_ticket #{params.inspect}")
    ticket = params[:cas_last_valid_ticket]
  end
end