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##Using Omni Auth

Step-by-step creation instructions to enable oAuth based authentication using the omni auth gem.

####create app

rails new omniauth_test -T -d postgresql
cd omniauth_test

####Generate model

rails g model user auth_hash:string email:string name:string

• auth_hash - the hash we get from the oauth provider (eg facebook, twitter, etc)
• Which oauth provider we're using (eg facebook, twitter, etc)

####Create database and tables

(remember to run postgres.app first)

rake db:create
rake db:migrate

####Quickly test your model

rails c
User.all

####Add omni auth gems

in Gemfile:

gem 'omniauth'
gem 'omniauth-facebook'
gem 'omniauth-twitter'
gem 'omniauth-google-oauth2'

add omniauth and then the strategy gem for each oauth provider you want to support. In the example above I'm doing facebook, twitter, and google. Full list of supported strategies.

After updating the gem file remember to run bundle install.

####Init omni auth

create a new file: config/initializers/omniauth.rb

Add an initlizer for each strategy / provider you want to support.

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :facebook, ENV['FACEBOOK_KEY'], ENV['FACEBOOK_SECRET']
  provider :twitter, ENV['TWITTER_KEY'], ENV['TWITTER_SECRET']
  provider :google_oauth2, ENV["GOOGLE_CLIENT_ID"], ENV["GOOGLE_CLIENT_SECRET"]
end

####Create apps with providers

Now you need to go to facebook, twitter, google, etc and create an app. This will allow you to get the key/secret for each service which you can set in your environment variable in one of two ways:

• globally in your ~/.zshrc
• locally in a .env file. Run your app using foreman run rails s

NOTE: remember to add .env to your .gitignore file to avoid exposing your keys on github.

Quicklinks for API key creation

• Facebook
• Twitter
• Google

####Create auth routes

Like many things in rails OmniAuth uses convention over configuration so it has pre-defined routes that you are expected to use.

• /auth/:provider -- login route, created for us, redirects user to the appropriate provider.
• /auth/failure -- user is sent here on authentication failure
• /auth/:provider/callback -- callback url. This is where the user is redirected after they come back from the provider.

add to config/routes.rb

get 'auth/logout' => 'auth#logout'
get 'auth/failure' => 'auth#failure'
get 'auth/:provider/callback' => 'auth#callback'

create auth controller auth_controller.rb

class AuthController < ApplicationController

    def callback
        provider_user = request.env['omniauth.auth']

        @user = User.find_or_create_by(auth_hash: provider_user['uid'], provider:params[:provider])

        if provider_user['info'] && provider_user['info']['name']
            @user.name=provider_user['info']['name']
            @user.save
        end
        session[:user_id] = @user.id
        redirect_to root_path
    end

    def logout
        session[:user_id]=nil
        redirect_to root_path
    end

    def failure
        #TODO: render a page with a failure message
        render plain: "this is a failure"
    end
   
end

##Views

Create links for login / logout. See views/pages/index.html.erb