OmniAuth Identity

The OmniAuth Identity gem provides a way for applications to utilize a traditional login/password based authentication system without the need to give up the simple authentication flow provided by OmniAuth. Identity is designed on purpose to be as featureless as possible: it provides the basic construct for user management and then gets out of the way.

Usage

This can be a bit hard to understand the first time. Luckily, Ryan Bates made a Railscast about it!

You use omniauth-identity just like you would any other OmniAuth provider: as a Rack middleware. The basic setup for a email/password authentication would look something like this:

use OmniAuth::Builder do
  provider :identity, :fields => [:email]
end

Next, you need to create a model (called Identity by default) that will be able to persist the information provided by the user. Luckily for you, there are pre-built models for popular ORMs that make this dead simple.

ActiveRecord

Just subclass OmniAuth::Identity::Models::ActiveRecord and provide fields in the database for all of the fields you are using.

class Identity < OmniAuth::Identity::Models::ActiveRecord
  # Add whatever you like!
end

Mongoid

Include the OmniAuth::Identity::Models::Mongoid mixin and specify fields that you will need.

class Identity
  include Mongoid::Document
  include OmniAuth::Identity::Models::Mongoid

  field :email, type: String
  field :name, type: String
  field :password_digest, type: String
end

MongoMapper

Include the OmniAuth::Identity::Models::MongoMapper mixin and specify fields that you will need.

class Identity
  include MongoMapper::Document
  include OmniAuth::Identity::Models::MongoMapper

  key :email, String
  key :name, String
  key :password_digest, String
end

Once you've got an Identity persistence model and the strategy up and running, you can point users to /auth/identity and it will request that they log in or give them the opportunity to sign up for an account. Once they have authenticated with their identity, OmniAuth will call through to /auth/identity/callback with the same kinds of information it would had the user authenticated through an external provider. Simple!

Custom Auth Model

To use a class other than the default, specify the :model option to a different class.

use OmniAuth::Builder do
  provider :identity, :fields => [:email], :model => MyCustomClass
end

Customizing Registration Failure

To use your own custom registration form, create a form that POSTs to '/auth/identity/register' with 'password', 'password_confirmation', and your other fields.

<%= form_tag '/auth/identity/register' do |f| %>
  <h1>Create an Account</h1>
  <%= text_field_tag :email %>
  <%= password_field_tag, :password %>
  <%= password_field_tag, :password_confirmation %>
  <%= submit_tag %>
<% end %>

Beware not to nest your form parameters within a namespace. This strategy looks for the form parameters at the top level of the post params. If you are using simple_form, then you can avoid the params nesting by specifying :input_html.

<%= simple_form_for @identity, :url => '/auth/identity/register' do |f| %>
  <h1>Create an Account</h1>
  <%# specify :input_html to avoid params nesting %>
  <%= f.input :email, :input_html => {:name => 'email'} %>
  <%= f.input :password, :as => 'password', :input_html => {:name => 'password'} %>
  <%= f.input :password_confirmation, :label => "Confirm Password", :as => 'password', :input_html => {:name => 'password_confirmation'} %>
  <button type='submit'>Sign Up</button>
<% end %>

Next you'll need to let OmniAuth know what action to call when a registration fails. In your OmniAuth configuration, specify any valid rack endpoint in the :on_failed_registration option.

use OmniAuth::Builder do
  provider :identity,
    :fields => [:email],
    :on_failed_registration => UsersController.action(:new)
end

For more information on rack endpoints, check out this introduction and ActionController::Metal