OmniAuth adapter to allow apps to sign in via GOV.UK signon
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README.md

GDS-SSO

This gem provides everything needed to integrate an application with Signon. It's a wrapper around OmniAuth that adds a 'strategy' for oAuth2 integration against Signon, and the necessary controller to support that request flow.

Some of the applications that use this gem:

Usage

Integration with a Rails 4+ app

To use gds-sso you will need an oAuth client ID and secret for Signon or a compatible system. These can be provided by one of the team with admin access to Signon.

Then include the gem in your Gemfile:

gem 'gds-sso', '<version>'

Create a config/initializers/gds-sso.rb that looks like:

GDS::SSO.config do |config|
  config.user_model   = 'User'

  # set up ID and Secret in a way which doesn't require it to be checked in to source control...
  config.oauth_id     = ENV['OAUTH_ID']
  config.oauth_secret = ENV['OAUTH_SECRET']

  # optional config for location of Signon
  config.oauth_root_url = "http://localhost:3001"

  # Pass in a caching adapter cache bearer token requests.
  config.cache = Rails.cache
end

The user model must include the GDS::SSO::User module.

It should have the following fields:

string   "name"
string   "email"
string   "uid"
string   "organisation_slug"
string   "organisation_content_id"
array    "permissions"
boolean  "remotely_signed_out", :default => false
boolean  "disabled", :default => false

You also need to include GDS::SSO::ControllerMethods in your ApplicationController.

For ActiveRecord, you probably want to declare permissions as "serialized" like this:

serialize :permissions, Array

Securing your application

GDS::SSO::ControllerMethods provides some useful methods for your application controllers.

To make sure that only people with a signon account and permission to use your app are allowed in use authenticate_user!.

class ApplicationController < ActionController::Base
  include GDS::SSO::ControllerMethods
  before_action :authenticate_user!
  # ...
end

You can refine authorisation to specific controller actions based on permissions using authorise_user!. All permissions are assigned via Signon.

class PublicationsController < ActionController::Base
  include GDS::SSO::ControllerMethods
  before_action :authorise_for_editing!, except: [:show, :index]
  # ...
private
  def authorise_for_editing!
    authorise_user!('edit_publications')
  end
end

authorise_user! can be configured to check for multiple permissions:

# fails unless the user has at least one of these permissions
authorise_user!(any_of: %w(edit create))

# fails unless the user has both of these permissions
authorise_user!(all_of: %w(edit create))

The signon application makes sure that only users who have been granted access to the application can access it (e.g. they have the signin permission for your app). This used to be left up to the applications themselves to check with the require_signin_permission! method. This is now deprecated and can be removed from your controllers. You should replace it with a call to authenticate_user! if you aren't already using that method, otherwise no signon authentication will be performed.

Authorisation for API Users

In addition to the single-sign-on strategy, this gem also allows authorisation via a "bearer token". This is used by publishing applications to be authorised as an API user.

To authorise with a bearer token, a request has to be made with the header:

Authorization: Bearer your-token-here

This gem will then authenticate the token with the Signon application. If valid, the API client will be authorised in the same way as a single-sign-on user. The gds-api-adapters gem has functionality for sending the bearer token for each request. To avoid making these requests for each incoming request, specify a caching adapter like Rails.cache:

GDS::SSO.config do |config|
  # ...
  # Pass in a caching adapter cache bearer token requests.
  config.cache = Rails.cache
end

If you are using a Rails 5 app in api_only mode this gem will automatically disable the oauth layers which use session persistence. You can configure this gem to be in api_only mode (or not) with:

GDS::SSO.config do |config|
  # ...
  # Only support bearer token authentication and send responses in JSON
  config.api_only = true
end

Use in development mode

In development, you generally want to be able to run an application without needing to run your own SSO server to be running as well. GDS-SSO facilitates this by using a 'mock' mode in development. Mock mode loads an arbitrary user from the local application's user tables:

GDS::SSO.test_user || GDS::SSO::Config.user_klass.first

To make it use a real strategy (e.g. if you're testing an app against the signon server), you will need to ensure that your Signon database has got OAuth config that matches what the apps use in development mode. To do this, run this in Signon:

bundle exec ./script/make_oauth_work_in_dev

Once that's done, set an environment variable when you run your app. e.g.:

GDS_SSO_STRATEGY=real bundle exec rails s

Testing in your application

If your app is using test-unit or minitest, there is a linting test that can verify your User model is compatible with GDS:SSO::User:

require 'gds-sso/lint/user_test'

class GDS::SSO::Lint::UserTest
  def user_class
    ::User
  end
end

Or if your app is using rspec, there is a shared examples spec:

require 'gds-sso/lint/user_spec'

describe User do
  it_behaves_like "a gds-sso user class"
end

Running the test suite

Run the tests with:

bundle exec rake

By default, the tests use the master of Signon for running integration tests. If you want to use a branch (or commit, or tag), you can run it like this:

SIGNON_COMMITISH=my_branch_name bundle exec rake

Licence

MIT License