Simple SSO

ApplicationController.rb

class ApplicationController < ActionController::Base

  before_action :auth_via_sso_cookie

  private

  def auth_via_sso_cookie
    if !current_user_id && cookies[:sso_from] && cookies[:sso_token] && cookies[:sso_env] == Rails.env
      verifier = ActiveSupport::MessageVerifier.new( SSO_SECRET_TOKEN.fetch(cookies[:sso_from]) )
      user_id = verifier.verify( cookies[:sso_token] )
      session[:current_user_id] = user_id
    end    
  end
  
  def add_sso_cookie(user_id)
    verifier = ActiveSupport::MessageVerifier.new( WebSite::Application.config.secret_token )
    value = verifier.generate(user_id)

    cookies[:sso_from]  = { value: "website", domain: SSO_DOMAIN } 
    cookies[:sso_env]   = { value: Rails.env, domain: SSO_DOMAIN }
    cookies[:sso_token] = { value: value, domain: SSO_DOMAIN }
  end

  
  def remove_sso_cookie
    cookies.delete(:sso_from, domain: SSO_DOMAIN)
    cookies.delete(:sso_env, domain: SSO_DOMAIN)
    cookies.delete(:sso_token, domain: SSO_DOMAIN)
  end
  
end

production.rb

SSO_DOMAIN = "website.com"

secret_token.rb

SSO_SECRET_TOKEN = { 
  "website" => 'blahblahblah' 
}

sessions_controller.rb

class SessionsController < ApplicationController

  def create
    #..after sign in
    add_sso_cookie( user["id"] )
  end
  
  def destroy
    #..after sign out
    remove_sso_cookie
  end
  
end