OmniAuth: Standardized Multi-Provider Authentication
OmniAuth is a library 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.
One strategy, called
Developer, is included with OmniAuth and provides
a completely insecure, non-production-usable strategy that directly
prompts a user for authentication information and then passes it
straight through. You can use it as a placeholder when you start
development and easily swap in other strategies later.
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::Cookie 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:
get '/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.
Integrating OmniAuth Into Your Rails API
The following middleware are (by default) included for session management in Rails applications. When using OmniAuth with a Rails API, you'll need to add one of these required middleware back in:
The trick to adding these back in is that, by default, they are passed
session_options when added (including the session key), so you can't just add
session_store.rb initializer, add
and have sessions functioning as normal.
To be clear: sessions may work, but your session options will be ignored
(i.e the session key will default to
_session_id). Instead of the
initializer, you'll have to set the relevant options somewhere
before your middleware is built (like
application.rb) and pass them to your
preferred middleware, like this:
config.session_store :cookie_store, key: '_interslice_session' config.middleware.use ActionDispatch::Cookies # Required for all session management config.middleware.use ActionDispatch::Session::CookieStore, config.session_options
OmniAuth supports a configurable logger. By default, OmniAuth will log
STDOUT but you can configure this using
# Rails application example OmniAuth.config.logger = Rails.logger
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.
Supported Ruby Versions
OmniAuth is tested under 2.1.10, 2.2.6, 2.3.3, 2.4.0, and JRuby.
This library aims to adhere to Semantic Versioning 2.0.0. Violations of this scheme should be reported as bugs. Specifically, if a minor or patch version is released that breaks backward compatibility, that version should be immediately yanked and/or a new version should be immediately released that restores compatibility. Breaking changes to the public API will only be introduced with new major versions. As a result of this policy, you can (and should) specify a dependency on this gem using the Pessimistic Version Constraint with two digits of precision. For example:
spec.add_dependency 'omniauth', '~> 1.0'
Copyright (c) 2010-2017 Michael Bleigh and Intridea, Inc. See LICENSE for details.