In this post I will explain how to configure Rails to perform single sign-on authentication using Oauth2 and your hosted Wordpress site as an authentication provider.
I’ve worked on a few projects lately where there was a need to integrate a Rails site with an existing Wordpress site in a Single Sign On fashion but without authenticating against a central auth store or use of an SSO appliance. It is very easy to turn an existing Wordpress installation into an OAuth provider and skip the hassle of maintaining a central authentication store or a conversion effort for users already using your Wordpress blog.
In order to turn our existing wordpress installation into an Oauth2 provider we first have to install the Wordpress Oauth2 Complete plugin. The official plugin in the Wordpress plugins repository is missing some recent enhancements so I recommend installing from the 1.0.4 release on github: https://github.com/justingreerbbi/wordpress-oauth/archive/1.0.4.zip
ouath2-complete to the /wp-content/plugins/ directory or use the built in plugin install by WordPressrails new omniauth-wordpress-oauth2-plugin-example . --database=sqlite3 -T
#authentication framework
gem 'devise'
#oauth2 integration
gem 'omniauth'
#wordpress oauth strategy
gem 'omniauth-wordpress-oauth2-plugin', github: 'jwickard/omniauth-wordpress-oauth2-plugin' bundle install
rails g devise:install
rails g devise user
rails db:migrateInstall Oauth2 provider plugin for your wordpress site:
https://github.com/jwickard/wordpress-oauth
Create client entry for your rails app with the callback key set to: http://your-rails-site.com/users/auth/wordpress_oauth2/callback 
Save the generated key & secret for next step
Add provider to devise initializer config/initializers/devise.rb
config.omniauth :wordpress_oauth2, ENV['APP_ID'], ENV['APP_SECRET'],
strategy_class: OmniAuth::Strategies::WordpressOauth2Plugin,
client_options: { site: 'http://yourcustomwordpress.com' }Update routes config/routes.rb to add omniauth_callbacks controller
devise_for :users, controllers: { omniauth_callbacks: 'omniauth_callbacks' }Easiest to just create the class app/controllers/omniauth_callbacks_controller.rb instead of running generator.
class OmniauthCallbacksController < ApplicationController
def wordpress_oauth2
#You need to implement the method below in your model (e.g. app/models/user.rb)
@user = User.find_for_wordpress_oauth2(request.env["omniauth.auth"], current_user)
if @user.persisted?
flash[:notice] = I18n.t "devise.omniauth_callbacks.success", :kind => "Wordpress Oauth2"
sign_in_and_redirect @user, :event => :authentication #this will throw if @user is not activated
else
session["devise.wordpress_oauth2_data"] = request.env["omniauth.auth"]
redirect_to new_user_registration_url
end
end
endUpdate user to be omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable, :omniauthableUpdate User model to find users by oauth provider data:
def self.find_for_wordpress_oauth2(oauth, signed_in_user=nil)
#if the user was already signed in / but they navigated through the authorization with wordpress
if signed_in_user
#update / synch any information you want from the authentication service.
if signed_in_user.email.nil? or signed_in_user.email.empty?
signed_in_user.update_attributes(email: oauth['info']['email'])
end
return signed_in_user
else
#find user by id and provider.
user = User.find_by_provider_and_uid(oauth['provider'], oauth['uid'])
#if user isn't in our database yet, create it!
if user.nil?
user = User.create!(email: oauth['info']['email'], uid: oauth['uid'], provider: oauth['provider'],
nickname: oauth['extra']['user_login'], website: oauth['info']['urls']['Website'],
display_name: oauth['extra']['display_name'])
end
user
end
endNow when an authenticated resource is requested on your rails site, the user will be redirected to the wordpress auth provider to login. When the user has authenticated, they will be redirected back to your rails application and your app will receive a hash of user data passed from the authentication source:
--- !ruby/hash:OmniAuth::AuthHash
provider: wordpress_oauth2
uid: '2'
info: !ruby/hash:OmniAuth::AuthHash::InfoHash
name: Joe Sandstone
email: jsandstone@example.com
nickname: jsand
urls: !ruby/hash:OmniAuth::AuthHash
Website: http://example.com
credentials: !ruby/hash:OmniAuth::AuthHash
token: 4070b5be481b1a4110797763ac27359c1d1da3bb
refresh_token: 212597ee673d630cfb95a77a69900c7ead1d3e19
expires_at: 1387912450
expires: true
extra: !ruby/hash:OmniAuth::AuthHash
ID: '2'
user_login: jsand
user_nicename: jsand
user_email: jsandstone@example.com
user_url: http://example.com
user_registered: '2013-12-12 15:29:34'
user_status: '0'
display_name: Joe SandstoneDemo Application: https://github.com/jwickard/omniauth-wordpress-oauth2-plugin-example
That’s it! Thanks!
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