OmniAuth: Standardized Multi-Provider Authentication
NOTICE: This documentation and code is for OmniAuth 1.0 in which each provider will become its own separate gem. If you're looking for the current released version, please visit OmniAuth 0.3 Stable Branch.
OmniAuth is a libary that standardizes multi-provider authentication for web applications. It was created to be powerful, flexible, and do as little as possible. Any developer can create strategies for OmniAuth that can authenticate users via disparate systems. OmniAuth strategies have been created for everything from Facebook to LDAP.
In order to use OmniAuth in your applications, you will need to leverage one or more strategies. These strategies are generally released individually as RubyGems, and you can see a community maintained list on the wiki for this project.
Adding OmniAuth to Your Application
Each OmniAuth strategy is a Rack Middleware. That means that you can use it the same way that you use any other Rack middleware. For example, to use the built-in Developer strategy in a Sinatra application I might do this:
require 'sinatra' require 'omniauth' class MyApplication < Sinatra::Base use Rack::Session use OmniAuth::Strategies::Developer end
Because OmniAuth is built for multi-provider authentication, I may
want to leave room to run multiple strategies. For this, the built-in
OmniAuth::Builder class gives you an easy way to specify multiple
strategies. Note that there is no difference between the following
code and using each strategy individually as middleware. This is an
example that you might put into a Rails initializer at
Rails.application.config.middleware.use OmniAuth::Builder do provider :developer unless Rails.env.production? provider :twitter, ENV['TWITTER_KEY'], ENV['TWITTER_SECRET'] end
You should look to the documentation for each provider you use for specific initialization requirements.
Integrating OmniAuth Into Your Application
OmniAuth is an extremely low-touch library. 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. This makes OmniAuth incredibly flexible. To use OmniAuth,
you need only to redirect users to
is the name of the strategy (for example,
Once the user has authenticated, what do you do next? 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 I
would add a line in my
routes.rb file like this:
match '/auth/:provider/callback', to: 'sessions#create'
And I might then have a
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
omniauth.auth key in the environment hash gives me my
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. For an in-depth description of what the authentication
hash might contain, see the Auth Hash Schema wiki page.
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.
The OmniAuth Wiki has actively maintained in-depth documentation for OmniAuth. It should be your first stop if you are wondering about a more in-depth look at OmniAuth, how it works, and how to use it.
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