Rails. Omniauth with devise (github example)

What We Aim To Do?

Create simple app with Auth handling by third part provider, in our case it will be github .

What is Omniauth?

OmniAuth is a library that standardizes multi-provider authentication for web applications. It also contains specifications for passing data to/from provider.

Let's start!

First of all we create rails app

rails new git_omni

add gem 'devise' to your Gemfile and install it

bundle install
rails g devise:install

after that we have to create user model

rails g devise user
bundle exec rake db:migrate

Ok, we are all set with devise, let's jump to omniauth.

How it works?

There are basic steps for user handling by Auth with Omniauth:

1. User click on 'auth with github'
2. Rails app redirect him to github page
3. User sign in on github and grant access to your app
4. Github redirect user back to your rails app
5. Rails app got at least two things: provider and uid
6. Now we can use this info to sign in user in app

In conclusion, we use provider and uid returned from github to sign in/register user in our app.

Go Over Omniauth

All instructions below related to github provider, but you can use anyone. All available strategies with gems located there.

we will use gem 'omniauth-github' and run bundle install

Add Routes and Controller

As you remember, after success signing in provider will redirect user to some url in our page. We should create route for that and handle them in controller

Add omniauth callbacks to config/routes.rb

devise_for :users, :controllers => { :omniauth_callbacks => "callbacks" }

and create new controller for handle callback app/controllers/callbacks_controller.rb

class CallbacksController < Devise::OmniauthCallbacksController
  def github
    @user = User.from_omniauth(request.env["omniauth.auth"])
    sign_in_and_redirect @user
  end
end

Ok, now we've got provider and uid from github, but what about from_omniauth method? Let's implement them!

Add Support Omniauth to Your Model

Add uid and provider fields to users table

rails g migration AddColumnsToUsers provider uid
bundle exec rake db:migrate

Add omniauthable module and from_omniauth class method to the model

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable,
         :omniauthable

  def self.from_omniauth(auth)  
    where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
      user.provider = auth.provider
      user.uid = auth.uid
      user.email = auth.info.email
      user.password = Devise.friendly_token[0,20]
    end
  end
end

Ok, we're done with coding. Now we need to create app on provider side and set devise config.

Create Github App

https://github.com/settings/applications/new

Set site url to http://localhost:3000/ and callback url to http://localhost:3000/users/auth/github/callback

When we done, go to the config/initializers/devise.rb and add omiauth config (paste your client ID and secret instead of placeholders)

 config.omniauth :github, 'CLIENT_ID', 'APP_SECRET', :scope => 'user:email'

Well done! Restart server and go to "/users/sign_in", you will see link for github sign in.

You can see working solution on github.

Will appreciate any comments, questions and suggestions!