Ruby On Rails: Login

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Ruby On Rails: Login

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By Josh Cunningham

This tutorial demonstrates how to add user login to a Ruby on Rails application. We recommend you to Log in to follow this quickstart with examples configured for your account.

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2 minutes

Get a sample configured with your account settings or check it out on Github.

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System requirements: Ruby 2.3.1+ | Rails 5.0.0+ or Rails 4.2.0+

New to Auth? Learn How Auth0 works, how it integrates with Regular Web Applications and which protocol it uses.

Configure Auth0

Get Your Application Keys

When you signed up for Auth0, a new application was created for you, or you could have created a new one.

You will need some details about that application to communicate with Auth0. You can get these details from the Application Settings section in the Auth0 dashboard.

You need the following information:

  • Domain
  • Client ID
  • Client Secret

If you download the sample from the top of this page these details are filled out for you.

If you have more than one application in your account, the sample comes with the values for your Default App.

App Dashboard

Configure Callback URLs

A callback URL is a URL in your application where Auth0 redirects the user after they have authenticated.

The callback URL for your app must be whitelisted in the Allowed Callback URLs field in your Application Settings. If this field is not set, users will be unable to log in to the application and will get an error.

If you are following along with the sample project you downloaded from the top of this page, the callback URL you need to whitelist in the Allowed Callback URLs field is http://localhost:3000/auth/auth0/callback.

Configure Logout URLs

A logout URL is a URL in your application that Auth0 can return to after the user has been logged out of the authorization server. This is specified in the returnTo query parameter.

The logout URL for your app must be whitelisted in the Allowed Logout URLs field in your Application Settings. If this field is not set, users will be unable to log out from the application and will get an error.

If you are following along with the sample project you downloaded from the top of this page, the logout URL you need to whitelist in the Allowed Logout URLs field is http://localhost:3000.

Configure Rails to Use Auth0

Install the Dependencies

To follow along with this guide, add the following dependencies to your Gemfile:

gem 'omniauth-auth0', '~> 2.2'

To prevent forged authentication requests, we need to also include CSRF protection. If you're using OmniAuth with Rails, include:

gem 'omniauth-rails_csrf_protection', '~> 0.1'

Once your gems are added, install with the following command:

bundle install

If you are using Windows, uncomment the tzinfo-data gem in the Gemfile.

Initialize OmniAuth Auth0

Create a file named auth0.rb under config/initializers and configure the OmniAuth middleware in it.

Rails.application.config.middleware.use OmniAuth::Builder do
    callback_path: '/auth/auth0/callback',
    authorize_params: {
      scope: 'openid email profile'

This tutorial uses omniauth-auth0, a custom OmniAuth strategy.

Add the Auth0 Callback Handler

Use the following command to create the controller that will handle the Auth0 callback:

rails generate controller auth0 --skip-template-engine --skip-assets --no-helper

In the newly created controller, add success and failure callback handlers.

# app/controllers/auth0_controller.rb

class Auth0Controller < ApplicationController
  def callback
    # This stores all the user information that came from Auth0
    # and the IdP
    session[:userinfo] = request.env['omniauth.auth']

    # Redirect to the URL you want after successful auth
    redirect_to '/dashboard'

  def failure
    # show a failure page or redirect to an error page
    @error_msg = request.params['message']

Replace the generated routes with the following:

# config/routes.rb

Rails.application.routes.draw do
  get 'auth/auth0/callback' => 'auth0#callback'
  get 'auth/failure' => 'auth0#failure'

Trigger Authentication

We need a way for users to trigger authentication. Add a link to /auth/auth0 anywhere in an existing template or use the steps below to generate a homepage in a new app.

To prevent forged authentication requests, make sure that you add a link with a method of :post (as described below using the link_to function in Rails) or create a form with a CSRF token included.

Run the following command to generate the homepage controller and views:

rails generate controller home show --skip-assets

Add the following to the generated show.html.erb file:

<!-- app/views/home/show.html.erb -->

<img src="">
<h1>RoR Auth0 Sample</h1>
<p>Step 1 - Login.</p>
<%= button_to 'Login', 'auth/auth0', method: :post %>

Finally, point the root path to generated controller:

# config/routes.rb

Rails.application.routes.draw do
  root 'home#show'
  # ...

Run bin/rails server and go to localhost:3000 in your browser. You should see the Auth0 logo and a link to log in.

Check the User's Authentication Status

You can use a controller concern to control access to routes that require the user to be authenticated:

# app/controllers/concerns/secured.rb

module Secured
  extend ActiveSupport::Concern

  included do
    before_action :logged_in_using_omniauth?

  def logged_in_using_omniauth?
    redirect_to '/' unless session[:userinfo].present?

Now generate a controller for the dashboard view that users will see once they are authenticated:

rails generate controller dashboard show --skip-assets

Include the concern in this new controller to prevent unauthenticated users from accessing its routes:

# app/controllers/dashboard_controller.rb

class DashboardController < ApplicationController
  include Secured

  def show

Add the session data for userinfo to the dashboard view to see what is returned:

<!-- app/views/dashboard/show.html.erb -->

<%= session[:userinfo].inspect %>

Finally, adjust your routes to point /dashboard to this new, secured controller:

# config/routes.rb

Rails.application.routes.draw do
  # ...
  get 'dashboard' => 'dashboard#show'
  # ...

With the Rails server still running, go to localhost:3000/dashboard in your browser and you should be redirected to the homepage.

Click the Login link and log in or sign up. Accept the consent modal that appears (for localhost only) and you should end up on at /dashboard with your user info showing.

Display Error Descriptions

Configure the application to display errors by adding the following to the production environment config:

# config/environments/production.rb

OmniAuth.config.on_failure = { |env|
  message_key = env['omniauth.error.type']
  error_description = Rack::Utils.escape(env['omniauth.error'].error_reason)
  new_path = "#{env['SCRIPT_NAME']}#{OmniAuth.config.path_prefix}/failure?message=#{message_key}&error_description=#{error_description}"['302 Moved'], 302, 'Location' => new_path).finish


Use the following command to create the controller that will handle user logout:

rails generate controller logout

To clear out all the objects stored within the session, call the reset_session method within the logout_controller/logout method. Learn more about reset_session here.

# app/controllers/logout_controller.rb

class LogoutController < ApplicationController
  include LogoutHelper
  def logout
    redirect_to logout_url.to_s

In logout_helper.rb file add the methods to generate the logout URL.

# app/helpers/logout_helper.rb

module LogoutHelper
  def logout_url
    domain = Rails.application.secrets.auth0_domain
    client_id = Rails.application.secrets.auth0_client_id
    request_params = {
      returnTo: root_url,
      client_id: client_id
    } domain, path: '/v2/logout', query: to_query(request_params))


  def to_query(hash) { |k, v| "#{k}=#{CGI.escape(v)}" unless v.nil? }.reject(&:nil?).join('&')

The final destination URL (the returnTo value) needs to be in the list of Allowed Logout URLs. See the logout documentation for more.


Using a reverse proxy

The redirect_uri parameter that OmniAuth generates when redirecting to login is based on the Host header that is passed to Rails. This can cause incorrect callback URLs to be passed when using this strategy (and OmniAuth in general) with a reverse proxy. You can adjust the host used by OmniAuth with the following snippet:

OmniAuth.config.full_host = lambda do |env|
    scheme         = env['rack.url_scheme']
    local_host     = env['HTTP_HOST']
    forwarded_host = env['HTTP_X_FORWARDED_HOST']
    forwarded_host.blank? ? "#{scheme}://#{local_host}" : "#{scheme}://#{forwarded_host}"

See this StackOverflow thread for more information.


This is likely caused by a missing CSRF token needed to POST the login request. If you inspect the login button in your browser, you should see something like this:

<a data-method="post" href="auth/auth0">Login</a>

... and in the <head> element for the page, you should have CSRF meta tags like these:

<meta name="csrf-param" content="authenticity_token">
<meta name="csrf-token" content="UY2XpKwxzwBWalxFVJ8yKsao/33it7If09BnZewpHifVPSpFJd2LrA7xgQn6VQrhZNGjgZoLI3kV+bkQHtr+Rw==">

With those elements in place, Rails will convert the login link to POST the CSRF token to the backend to verify it before redirecting to login.

This error means that a cookie session is being used and because the whole profile is being stored, it overflows the max-size of 4 kb. If you are unable to access the user profile and you get an error similar to NoMethodError, undefined method '[]' for nil:NilClass, try using In-Memory store for development.

Go to /config/initializers/session_store.rb and add the following:

Rails.application.config.session_store :cache_store

Go to /config/environments/development.rb and add the following:

config.cachestore = :memorystore

It is recommended that a memory store such as MemCached being used for production applications.

SSL Issues

Under some configurations, Ruby may not be able to find certification authority certificates (CA certs).

Download the CA certs bundle to the project directory:

curl -L -o lib/ca-bundle.crt

Add this initializer to config/initializers/fix_ssl.rb:

# config/initializers/fix_ssl.rb

require 'open-uri'
require 'net/https'

module Net
  class HTTP
    alias_method :original_use_ssl=, :use_ssl=

    def use_ssl=(flag)
      path = ( Rails.env == "development") ? "lib/ca-bundle.crt" : "/usr/lib/ssl/certs/ca-certificates.crt"
      self.ca_file = Rails.root.join(path).to_s
      self.verify_mode = OpenSSL::SSL::VERIFY_PEER
      self.original_use_ssl = flag

"failure message=invalid_credentials"

This issue doesn't occur when working locally but may happen in a staging or production environment. The error message may be displayed as:

omniauth: (auth0) Authentication failure! invalid_credentials: OAuth2::Error, server_error: The redirect URI is wrong. You send [wrong url], and we expected [callback url set in your app settings]

To solve this, add the following to config/environments/staging.rb or production.rb:

OmniAuth.config.full_host = ""

Substitute with the actual URL you'll be using in your application.

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