AzureJwtAuth

Easy way for Ruby applications to authenticate to Azure B2C/AD in order to access protected web resources.

Installation

Add this line to your application's Gemfile:

gem 'azure_jwt_auth'

And then execute:

$ bundle

Or install it yourself as:

$ gem install azure_jwt_auth

Usage with Rails

First of all, we add our providers into an initializer:

# config/initializers/azure.rb

require 'azure_jwt_auth/jwt_manager'

AzureJwtAuth::JwtManager.load_provider(
  :b2c,
  'https://login.microsoftonline.com/.../v2.0/.well-known/openid-configuration')
)

AzureJwtAuth::JwtManager.load_provider(
  :ad,
  'https://sts.windows.net/.../v2.0/.well-known/openid-configuration'
)
...

Then, we add Authenticable module into ApplicationController and define entity_from_token_payload method.
This method is used by Authenticable module to load current_user.

require 'azure_jwt_auth/authenticable'

class ApplicationController < ActionController::API
  include AzureJwtAuth::Authenticable

  rescue_from AzureJwtAuth::NotAuthorized, with: :render_401

  private

  def render_401
    render json: {}, status: 401
  end

  def entity_from_token_payload(payload)
    # Returns a valid entity, `nil` or raise
    # e.g.
    #   User.find payload['sub']
  end
end

Finally, we can use authenticate! method into ours controllers:

class ExampleController < ApplicationController
  before_action :authenticate!

  ...
end

Providers

Provider class initializer receives the following parameters:

parameter	description
uid	unique provider identifier
config_url	azure url to get config
validations	payload fields validations which will be checked for each token: {payload_field: value_expected, ...} (optional)

We create providers using the AzureJwtAuth::JwtManager.load_provider method:

AzureJwtAuth::JwtManager.load_provider(
  :b2c, # uid
  'https://login.microsoftonline.com/.../v2.0/.well-known/openid-configuration'), # config_url
  {'aud' => 'my_app_id'} # validations
)

Authenticable

This module provides us with the following methods:

• authenticate!

  Check if a token is valid for any provider and loads current_user. Otherwise it throws an exception.

  If you need other behavior you can define your custom authenticate! method like this:

  def my_authenticate!
    begin
      token = JwtManager.new(request, :privider_id)
      unauthorize! unless token.valid?
    rescue
      unauthorize!
    end
  
    @current_user = User.find(token.payload['sub'])
  end

• current_user

  Returns current_user loaded by authenticate! method.

• signed_in?

  Check if exists current_user.

• unauthorize!

  Throws a AzureJwtAuth::NotAuthorized exception.

Testing (rspec)

Require the AzureJwtAuth::Spec::Helpers helper module in rails_helper.rb.

  require 'azure_jwt_auth/spec/helpers'
  ...
  RSpec.configure do |config|
    ...
    config.include AzureJwtAuth::Spec::Helpers, :type => :controller
  end

And then we can just call sign_in(user):

  describe ExampleController
    let(:user) { MyEntity.create(...) }

    it "blocks unauthenticated access" do
      get :index
      expect(response).to have_http_status(401)
    end

    it "allows authenticated access" do
      sign_in user # user will be returned by current_user method
      get :index
      expect(response).to have_http_status(200)
    end
  end

License

The gem is available as open source under the terms of the MIT License.