CSC/ECE 517 Spring 2015/ch1b 21 QW

Omniauth

Omniauth is a Ruby authentication framework aimed to integrated with various types of authentication providers. It can be hooked up to any system, from social network to enterprise systems to simple username and password authentication. <ref>https://github.com/intridea/omniauth/wiki</ref>

The topic writeup for this page can be found here.

Background

With web application booming, most users login hundreds of services every day and won't expect to create unique login and password for each service. So intridea recently releases a standard library to provide multi-provider authentication for web applications.

Getting Start

Each OmniAuth strategy is a Rack Middleware, which means it can be used the same way as other Rack middleware. Here we introduce some simple steps to illustrate how to use Twitter strategy for OmniAuth.<ref>https://github.com/intridea/omniauth</ref>

Installing

First start by adding this gem to your Gemfile:

gem 'omniauth-twitter'

If you need to use the latest HEAD version, you can do so with:

gem 'omniauth-twitter', :github => 'arunagw/omniauth-twitter'

Usage

Because OmniAuth is built for multi-provider authentication, you need to build multiple strategies. For this, the Rack middleware OmniAuth::Builder class gives an easy way to build up your list of OmniAuth strategies for use in your application.

Below is an example that you can put into a Rails initializer at config/initializers/omniauth.rb or add it to your middleware:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :developer unless Rails.env.production?
  provider :twitter, ENV['TWITTER_KEY'], ENV['TWITTER_SECRET']
end

Where "TWITTER_KEY" and "TWITTER_SECRET" is the appropriate values you obtained here.

Integrating OmniAuth into Rails Application

OmniAuth is a library extremely easy to use. It is designed to be a black box that you can send your application's users into when you need authentication and then get information back. OmniAuth was intentionally built not to automatically associate with a User model or make assumptions about how many authentication methods you might want to use or what you might want to do with the data once a user has authenticated. To use OmniAuth, you need only to redirect users to /auth/:provider , where :provider is the name of the strategy (for example, developer or twitter ). From there, OmniAuth will take over and take the user through the necessary steps to authenticate them with the chosen strategy.

Once the user has authenticated, OmniAuth simply sets a special hash called the Authentication Hash on the Rack environment of a request to /auth/:provider/callback. This hash contains as much information about the user as OmniAuth was able to glean from the utilized strategy. You should set up an endpoint in your application that matches to the callback URL and then performs whatever steps are necessary for your application.

For example, in a Rails app you can add a line in routes.rb file like this:

get '/auth/:provider/callback', to: 'sessions#create'

And in Sinatra, a callback might look something like this:

# Support both GET and POST for callbacks
%w(get post).each do |method|
  send(method, "/auth/:provider/callback") do
    env['omniauth.auth'] # => OmniAuth::AuthHash
  end
end

Also of note, by default, if user authentication fails on the provider side, OmniAuth will catch the response and then redirect the request to the path /auth/failure, passing a corresponding error message in a parameter named message. You may want to add an action to catch these cases. Continuing with the previous Sinatra example, you could add an action like this:

get '/auth/failure' do
  flash[:notice] = params[:message] # if using sinatra-flash or rack-flash
  redirect '/'
end

And finally you can have SessionsController with code that looks something like this:

class SessionsController < ApplicationController
  def create
    @user = User.find_or_create_from_auth_hash(auth_hash)
    self.current_user = @user
    redirect_to '/'
  end

  protected

  def auth_hash
    request.env['omniauth.auth']
  end
end

The omniauth.auth key in the environment hash gives the Authentication Hash which will contain information about the just authenticated user including a unique id, the strategy they just used for authentication, and personal details such as name and email address as available.

Note that OmniAuth does not perform any actions beyond setting some environment information on the callback request. It is entirely up to you how you want to implement the particulars of your application's authentication flow.

Logging

OmniAuth supports a configurable logger. By default, OmniAuth will log to STDOUT but you can configure this using OmniAuth.config.logger:

# Rails application example
OmniAuth.config.logger = Rails.logger

Other Examples

OmniAuth Facebook

Installing

To use Facebook OmniAuth Strateges<ref>https://github.com/mkdynamic/omniauth-facebook</ref>, first, add this gem into your Gemfile, and then run bundle install:

gem 'omniauth-facebook'

Usage

Adding the middleware to a Rails app in config/initializers/omniauth.rb:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :facebook, ENV['FACEBOOK_KEY'], ENV['FACEBOOK_SECRET']
end

Configuring

Option name	Default	Explanation
scope	email	A comma-separated list of permissions you want to request from the user. See the Facebook docs for a full list of available permissions
display	page	The display context to show the authentication page. Options are: page, popup and touch. Read the Facebook docs for more details
image_size	square	Set the size for the returned image url in the auth hash. Valid options include square (50x50), small (50 pixels wide, variable height), normal (100 pixels wide, variable height), or large (about 200 pixels wide, variable height). Additionally, you can request a picture of a specific size by setting this option to a hash with :width and :height as keys. This will return an available profile picture closest to the requested size and requested aspect ratio. If only :width or :height is specified, we will return a picture whose width or height is closest to the requested size, respectively.
info_fields		Specify exactly which fields should be returned when getting the user's info. Value should be a comma-separated string as per <ref>https://developers.facebook.com/docs/graph-api/reference/user/</ref>
locale		Specify locale which should be used when getting the user's info. Value should be locale string as per <ref>https://developers.facebook.com/docs/reference/api/locale/</ref>
auth_type		Optionally specifies the requested authentication features as a comma-separated list <ref>https://developers.facebook.com/docs/facebook-login/reauthentication/</ref>. Valid values are https (checks for the presence of the secure cookie and asks for re-authentication if it is not present), and reauthenticate (asks the user to re-authenticate unconditionally). Default is nil.
secure_image_url	false	Set to true to use https for the avatar image url returned in the auth hash
callback_url / callback_path		Specify a custom callback URL used during the server-side flow. Note this must be allowed by your app configuration on Facebook

OmniAuth GitHub

To use GitHub OmniAuth Strateges<ref>https://github.com/intridea/omniauth-github</ref>, first, add this gem into your Gemfile, and then run bundle install:

gem 'omniauth-github'

Then adding the middleware to a Rails app in config/initializers/omniauth.rb:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :github, ENV['GITHUB_KEY'], ENV['GITHUB_SECRET']
end

References

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