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zquestz / omniauth-google-oauth2

Oauth2 strategy for Google
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google-oauth2 oauth2 omniauth ruby

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Gem Version

OmniAuth Google OAuth2 Strategy

Strategy to authenticate with Google via OAuth2 in OmniAuth.

Get your API key at: https://code.google.com/apis/console/ Note the Client ID and the Client Secret.

For more details, read the Google docs: https://developers.google.com/accounts/docs/OAuth2

Installation

Add to your Gemfile:

gem 'omniauth-google-oauth2'

Then bundle install.

Google API Setup

Usage

Here's an example for adding the middleware to a Rails app in config/initializers/omniauth.rb:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :google_oauth2, ENV['GOOGLE_CLIENT_ID'], ENV['GOOGLE_CLIENT_SECRET']
end
OmniAuth.config.allowed_request_methods = %i[get]

You can now access the OmniAuth Google OAuth2 URL: /auth/google_oauth2

For more examples please check out examples/omni_auth.rb

Using Devise? Skip the above and jump down to the Devise section! After setting up the provider via Devise, you can reference the configurations below.

NOTE: While developing your application, if you change the scope in the initializer you will need to restart your app server. Remember that either the 'email' or 'profile' scope is required!

Configuration

You can configure several options, which you pass in to the provider method via a hash:

Here's an example of a possible configuration where the strategy name is changed, the user is asked for extra permissions, the user is always prompted to select their account when logging in and the user's profile picture is returned as a thumbnail:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :google_oauth2, ENV['GOOGLE_CLIENT_ID'], ENV['GOOGLE_CLIENT_SECRET'],
    {
      scope: 'email, profile, http://gdata.youtube.com',
      prompt: 'select_account',
      image_aspect_ratio: 'square',
      image_size: 50
    }
end

Auth Hash

Here's an example of an authentication hash available in the callback by accessing request.env['omniauth.auth']:

{
  "provider" => "google_oauth2",
  "uid" => "100000000000000000000",
  "info" => {
    "name" => "John Smith",
    "email" => "john@example.com",
    "first_name" => "John",
    "last_name" => "Smith",
    "image" => "https://lh4.googleusercontent.com/photo.jpg",
    "urls" => {
      "google" => "https://plus.google.com/+JohnSmith"
    }
  },
  "credentials" => {
    "token" => "TOKEN",
    "refresh_token" => "REFRESH_TOKEN",
    "expires_at" => 1496120719,
    "expires" => true
  },
  "extra" => {
    "id_token" => "ID_TOKEN",
    "id_info" => {
      "azp" => "APP_ID",
      "aud" => "APP_ID",
      "sub" => "100000000000000000000",
      "email" => "john@example.com",
      "email_verified" => true,
      "at_hash" => "HK6E_P6Dh8Y93mRNtsDB1Q",
      "iss" => "accounts.google.com",
      "iat" => 1496117119,
      "exp" => 1496120719
    },
    "raw_info" => {
      "sub" => "100000000000000000000",
      "name" => "John Smith",
      "given_name" => "John",
      "family_name" => "Smith",
      "profile" => "https://plus.google.com/+JohnSmith",
      "picture" => "https://lh4.googleusercontent.com/photo.jpg?sz=50",
      "email" => "john@example.com",
      "email_verified" => "true",
      "locale" => "en",
      "hd" => "company.com"
    }
  }
}

Devise

First define your application id and secret in config/initializers/devise.rb. Do not use the snippet mentioned in the Usage section.

Configuration options can be passed as the last parameter here as key/value pairs.

config.omniauth :google_oauth2, 'GOOGLE_CLIENT_ID', 'GOOGLE_CLIENT_SECRET', {}

NOTE: If you are using this gem with devise with above snippet in config/initializers/devise.rb then do not create config/initializers/omniauth.rb which will conflict with devise configurations.

Then add the following to 'config/routes.rb' so the callback routes are defined.

devise_for :users, controllers: { omniauth_callbacks: 'users/omniauth_callbacks' }

Make sure your model is omniauthable. Generally this is "/app/models/user.rb"

devise :omniauthable, omniauth_providers: [:google_oauth2]

Then make sure your callbacks controller is setup.

# app/controllers/users/omniauth_callbacks_controller.rb:

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def google_oauth2
      # You need to implement the method below in your model (e.g. app/models/user.rb)
      @user = User.from_omniauth(request.env['omniauth.auth'])

      if @user.persisted?
        flash[:notice] = I18n.t 'devise.omniauth_callbacks.success', kind: 'Google'
        sign_in_and_redirect @user, event: :authentication
      else
        session['devise.google_data'] = request.env['omniauth.auth'].except('extra') # Removing extra as it can overflow some session stores
        redirect_to new_user_registration_url, alert: @user.errors.full_messages.join("\n")
      end
  end
end

and bind to or create the user

# app/models/user.rb

def self.from_omniauth(access_token)
    data = access_token.info
    user = User.where(email: data['email']).first

    # Uncomment the section below if you want users to be created if they don't exist
    # unless user
    #     user = User.create(name: data['name'],
    #        email: data['email'],
    #        password: Devise.friendly_token[0,20]
    #     )
    # end
    user
end

For your views you can login using:

<%# omniauth-google-oauth2 1.0.x uses OmniAuth 2 and requires using HTTP Post to initiate authentication: %>
<%= link_to "Sign in with Google", user_google_oauth2_omniauth_authorize_path, method: :post %>

<%# omniauth-google-oauth2 prior 1.0.0: %>
<%= link_to "Sign in with Google", user_google_oauth2_omniauth_authorize_path %>

<%# Devise prior 4.1.0: %>
<%= link_to "Sign in with Google", user_omniauth_authorize_path(:google_oauth2) %>

An overview is available at https://github.com/heartcombo/devise/wiki/OmniAuth:-Overview

One-time Code Flow (Hybrid Authentication)

Google describes the One-time Code Flow here. This hybrid authentication flow has significant functional and security advantages over a pure server-side or pure client-side flow. The following steps occur in this flow:

  1. The client (web browser) authenticates the user directly via Google's JS API. During this process assorted modals may be rendered by Google.
  2. On successful authentication, Google returns a one-time use code, which requires the Google client secret (which is only available server-side).
  3. Using a AJAX request, the code is POSTed to the Omniauth Google OAuth2 callback.
  4. The Omniauth Google OAuth2 gem will validate the code via a server-side request to Google. If the code is valid, then Google will return an access token and, if this is the first time this user is authenticating against this application, a refresh token. Both of these should be stored on the server. The response to the AJAX request indicates the success or failure of this process.

This flow is immune to replay attacks, and conveys no useful information to a man in the middle.

The omniauth-google-oauth2 gem supports this mode of operation when provider_ignores_state is set to true. Implementors simply need to add the appropriate JavaScript to their web page, and they can take advantage of this flow. An example JavaScript snippet follows.

// Basic hybrid auth example following the pattern at:
// https://developers.google.com/identity/sign-in/web/reference

<script src="https://apis.google.com/js/platform.js?onload=init" async defer></script>

...

function init() {
  gapi.load('auth2', function() {
    // Ready.
    $('.google-login-button').click(function(e) {
      e.preventDefault();

      gapi.auth2.authorize({
        client_id: 'YOUR_CLIENT_ID',
        cookie_policy: 'single_host_origin',
        scope: 'email profile',
        response_type: 'code'
      }, function(response) {
        if (response && !response.error) {
          // google authentication succeed, now post data to server.
          jQuery.ajax({type: 'POST', url: '/auth/google_oauth2/callback', data: response,
            success: function(data) {
              // response from server
            }
          });
        } else {
          // google authentication failed
        }
      });
    });
  });
};

Note about mobile clients (iOS, Android)

The documentation at https://developers.google.com/identity/sign-in/ios/offline-access specifies the _REDIRECTURI to be either a set value or an EMPTY string for mobile logins to work. Else, you will run into _redirect_urimismatch errors.

In that case, ensure to send an additional parameter redirect_uri= (empty string) to the /auth/google_oauth2/callback URL from your mobile device.

Note about CORS

If you're making POST requests to /auth/google_oauth2/callback from another domain, then you need to make sure 'X-Requested-With': 'XMLHttpRequest' header is included with your request, otherwise your server might respond with OAuth2::Error, : Invalid Value error.

Getting around the redirect_uri_mismatch error (See Issue #365)

If you are struggling with a persistent redirect_uri_mismatch, you can instead pass the access_token from getAuthResponse directly to the auth/google_oauth2/callback endpoint, like so:

// Initialize the GoogleAuth object
let googleAuth;
gapi.load('client:auth2', async () => {
  await gapi.client.init({ scope: '...', client_id: '...' });
  googleAuth = gapi.auth2.getAuthInstance();
});

// Call this when the Google Sign In button is clicked
async function signInGoogle() {
  const googleUser = await googleAuth.signIn(); // wait for the user to authorize through the modal
  const { access_token } = googleUser.getAuthResponse();

  const data = new FormData();
  data.append('access_token', access_token);

  const response = await api.post('/auth/google_oauth2/callback', data)
  console.log(response);
}

Using Axios

If you're making a GET resquests from another domain using access_token.

axios
  .get(
    'url(path to your callback}',
    { params: { access_token: 'token' } },
    headers....
    )

If you're making a POST resquests from another domain using access_token.

axios
  .post(
    'url(path to your callback}',
    { access_token: 'token' },
    headers....
    )

--OR--

axios
  .post(
    'url(path to your callback}',
    null,
      {
        params: {
          access_token: 'token'
        },
        headers....
      }
    )

Fixing Protocol Mismatch for redirect_uri in Rails

Just set the full_host in OmniAuth based on the Rails.env.

# config/initializers/omniauth.rb
OmniAuth.config.full_host = Rails.env.production? ? 'https://domain.com' : 'http://localhost:3000'

License

Copyright (c) 2018 by Josh Ellithorpe

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.