devise_cas_authenticatable

Written by Nat Budin
Taking a lot of inspiration from devise_ldap_authenticatable

devise_cas_authenticatable is CAS single sign-on support for Devise applications. It acts as a replacement for database_authenticatable. It builds on rubycas-client and should support just about any conformant CAS server (although I have personally tested it using rubycas-server).

Requirements

• Rails 2.3 or greater (works with 3.x versions as well)
• Devise 1.0 or greater
• rubycas-client

Installation

gem install --pre devise_cas_authenticatable

and in your config/environment.rb (on Rails 2.3):

config.gem 'devise', :version => '~> 1.0.6'
config.gem 'devise_cas_authenticatable'

or Gemfile (Rails 3.x):

gem 'devise'
gem 'devise_cas_authenticatable'

Setup

Once devise_cas_authenticatable is installed, add the following to your user model:

devise :cas_authenticatable

You can also add other modules such as token_authenticatable, trackable, etc. Please do not add database_authenticatable as this module is intended to replace it.

You'll also need to set up the database schema for this:

create_table :users do |t|
  t.string :username, :null => false
end

We also recommend putting a unique index on the username column:

add_index :users, :username, :unique => true

(Note: previously, devise_cas_authenticatable recommended using a t.cas_authenticatable method call to update the schema. Devise 2.0 has deprecated this type of schema building method, so we now recommend just adding the username string column as above. As of this writing, t.cas_authenticatable still works, but throws a deprecation warning in Devise 2.0.)

Finally, you'll need to add some configuration to your config/initializers/devise.rb in order to tell your app how to talk to your CAS server:

Devise.setup do |config|
  ...
  config.cas_base_url = "https://cas.myorganization.com"
  
  # you can override these if you need to, but cas_base_url is usually enough
  # config.cas_login_url = "https://cas.myorganization.com/login"
  # config.cas_logout_url = "https://cas.myorganization.com/logout"
  # config.cas_validate_url = "https://cas.myorganization.com/serviceValidate"
  
  # The CAS specification allows for the passing of a follow URL to be displayed when
  # a user logs out on the CAS server. RubyCAS-Server also supports redirecting to a
  # URL via the destination param. Set either of these urls and specify either nil,
  # 'destination' or 'follow' as the logout_url_param. If the urls are blank but
  # logout_url_param is set, a default will be detected for the service.
  # config.cas_destination_url = 'https://cas.myorganization.com'
  # config.cas_follow_url = 'https://cas.myorganization.com'
  # config.cas_logout_url_param = nil

  # By default, devise_cas_authenticatable will create users.  If you would rather
  # require user records to already exist locally before they can authenticate via
  # CAS, uncomment the following line.
  # config.cas_create_user = false  
end

Extra attributes

If your CAS server passes along extra attributes you'd like to save in your user records, using the CAS extra_attributes parameter, you can define a method in your user model called cas_extra_attributes= to accept these. For example:

class User < ActiveRecord::Base
  devise :cas_authenticatable
  
  def cas_extra_attributes=(extra_attributes)
    extra_attributes.each do |name, value|
      case name.to_sym
      when :fullname
        self.fullname = value
      when :email
        self.email = value
      end
    end
  end
end

See also

• CAS
• rubycas-server
• rubycas-client
• Devise
• Warden

TODO

• Test on non-ActiveRecord ORMs