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Last updated: 18 Oct 2023

signon: Usage Documentation

Setup Rake Tasks

To create a new client application to which Signon will provide sign-on services:

rake applications:create name=ClientName description="What does this app do" \
home_uri="https://myapp.com" redirect_uri="https://myapp.com/auth/gds/callback"

This will create and return a client ID and secret that can be used in the app (normally via GDS-SSO).

You can then add the ID and secret to the app's ENV using your preferred method.

Access Tokens

You may also need to create an access token, so one application can identify itself to another. Say, for instance, you have an API that requires authentication and you need to configure a frontend to make requests of it. Assuming you have your application set up in Signon under the name "Stuff API", follow these steps to create an access token for API clients to access your it:

  • Login to Signon with 'superadmin' role
  • Click 'API Users', followed by 'Create API User'
  • Fill-in a name and email for the API client
  • Once saved, click "Add application token", select "Stuff API" and press "Create access token"
  • You should see an access token on the screen, which you must copy as it is the only time it'll be displayed on screen.

Development.

More detail is contained in the GDS-SSO Repo, but if you just want to get this working, follow the steps below:

  • If you haven't already set real tokens in your app's ENV, you'll first need to run the following command to make sure your database has got OAuth config that matches what the apps use in development mode:

    bundle exec ./script/make_oauth_work_in_dev
    
  • You must then make sure you set an environment variable when you run your app. eg:

    GDS_SSO_STRATEGY=real bundle exec rails s
    

Creating new permissions

To create a new permission for an existing app, you first need to have the "superadmin" role on your account (or have access to someone who does): you'll then be able to access the "Administer applications" menu item. Under the application you want to change, follow the "Supported Permissions" link and add a new permission from there.

Note that this UI won't let you edit or delete existing permissions.

Creating new organisations

Instead of creating organisations directly in signon we pull them in from whitehall which is the canonical source. If you run:

rake organisations:fetch

This will communicate with whitehall to get the complete list of orgs and the relationships between them. It then uses this information to make sure signon is up to date.

One downside to this is that whitehall allows an org to have multiple parents whereas signon only allows for a single parent. Signon's behaviour is currently to set the parent of an org with multiple parents to the one that appears last in the api response.

On deployed environments this rake task is run nightly at 11pm via jenkins. This is configured in govuk-puppet. If you want orgs and their relationships to be modelled correctly in signon, you should do it whitehall and then let this nightly import do its thing.

Implementation Notes

The application is divided into two parts: user management (User sign-on and passwords) and OAuth delegation (SSO service, contacts API).

User management is handled by Devise. Configuration is in config/initializers/devise and views are either concrete (under app/views/devise) or pulled in from the Devise gem. Likewise with Controllers, though Devise controllers should inherit from Devise::SomeController (e.g., as with the PasswordsController).

API authentication is handled by Doorkeeper. It's a bit of a tricky beast, but not too bad overall, and it nicely separates concerns. Instead of exposing the current user with current_user, Doorkeeper exposes the current valid OAuth token as doorkeeper_token. Doorkeeper tokens are associated with a resource owner through an authenticator block, defined in config/initializers/doorkeeper.

To require Devise authentication in a controller (ie, you want a user sitting at a computer looking at the page), add before_action:authenticate_user! to the controller.

For example:

class SettingsController
  before_action :authenticate_user!

  def show
    settings = current_user.settings
  end
end

To require Doorkeeper authentication in a controller (i.e., you want an application that has been granted a token on behalf of a user to interact with the controller), add before_action :doorkeeper_authorize! to the controller.

For example:

class AutomaticApiController
  before_action :doorkeeper_authorize!

  def swizzle
    @token_owning_user = User.find_by_id(doorkeeper_token.resource_owner_id)
  end
end