Minimal Single Sign On using Sinatra

gistfile1.rb

class SessionManager < Sinatra::Base
  use Rack::Session::Memcache,
    :key => 'customsessionkey',
    :memcache_server => 'a.b.c.d:11211',
    :cookie_only => false,
    :secure => true,
    :secret => 'secretpassphrase'

  get '/cookies/set' do
    # Newly set cookie points to the same session
    session[:user].inspect 
  end
end

class SSOLoginApp < Sinatra::Base

  use SessionManager

  post '/login' do
    session[:user] = User.authenticate(params.id)

    MY_SSO_DOMAIN_LIST.map do |domain|
      "<img src='https://#{domain}/cookies/set?customsessionkey=#{env['rack.session.options'][:id]}'  style='display:none'></img>"
    end.join
  end

end