Aserto Rails

Aserto authorization library for Ruby and Ruby on Rails.

Built on top of aserto and aserto-grpc-authz.

Prerequisites

• Ruby 3.0 or newer.
• Rails 6 or newer.
• An Aserto account.

Installation

Add to your application Gemfile:

gem "aserto-rails"

And then execute:

bundle install

Or install it yourself as:

gem install aserto-rails

Configuration

The following configuration settings are required for authorization:

• policy_id
• tenant_id
• authorizer_api_key
• policy_root

These settings can be retrieved from the Policy Settings page of your Aserto account.

Optional parameters:

Parameter name	Default value	Description
service_url	"authorizer.prod.aserto.com:8443"	Sets the URL for the authorizer endpoint.
decision	"allowed"	The decision that will be used when executing an authorizer request.
logger	STDOUT	The logger to be used.
identity_mapping	{ type: :none }	The strategy for retrieveing the identity, possible values: :jwt, :sub, :none

Identity

To determine the identity of the user, the gem can be configured to use a JWT token or a claim using the identity_mapping config.

# configure the gem to use a JWT token form the `my-auth-header` header.
config.identity_mapping = {
  type: :jwt,
  from: "my-auth-header",
}

# configure the gem to use a claim from the JWT token.
# This will decode the JWT token and extract the `sub` field from payload.
config.identity_mapping = {
  type: :sub,
  from: :sub,
}

The whole identity resolution can be overwritten by providing a custom function.

# config/initializers/aserto.rb

# needs to return a hash with the identity having `type` and `identity` keys.
# supported types: `:jwt, :sub, :none`
Aserto.with_identity_mapper do |request|
  {
    type: :sub,
    identity: "my custom identity",
  }
end

URL path to policy mapping

By default, when computing the policy path:

• converts all slashes to dots
• converts any character that is not alpha, digit, dot or underscore to underscore
• converts uppercase characters in the URL path to lowercases

This behavior can be overwritten by providing a custom function:

# config/initializers/aserto.rb

# must return a String
Aserto.with_policy_path_mapper do |policy_root, request|
  method = request.request_method
  path = request.path_info

  "custom: #{policy_root}.#{method}.#{path}"
end

Resource

A resource can be any structured data that the authorization policy uses to evaluate decisions. By default, gem do not include a resource in authorization calls.

This behavior can be overwritten by providing a custom function:

# config/initializers/aserto.rb

# must return a Hash
Aserto.with_resource_mapper do |request|
  { resource:  request.path_info }
end

Examples

# config/initializers/aserto.rb
require "aserto/rails"

Aserto.configure do |config|
  config.enabled = true
  config.policy_name = "my-policy-name"
  config.instance_label = "my-instance"
  config.authorizer_api_key = Rails.application.credentials.aserto[:authorizer_api_key]
  config.policy_root = "peoplefinder"
  config.service_url = "localhost:8282"
  config.cert_path = "/path/to/topaz/cert.crt"
  config.decision = "allowed"
  config.logger = Rails.logger
  config.identity_mapping = {
    type: :sub,
    from: :sub
  }
end

Controller helpers

aserto_authorize!

The aserto_authorize! method in the controller will raise an exception if the user is not able to perform the given action.

def show
  aserto_authorize!
  @post = Post.find(params[:id])
end

Setting this for every action can be tedious, therefore the aserto_authorize_resource method is provided to automatically authorize all actions in a RESTful style resource controller. It will use a before action to load the resource into an instance variable and authorize it for every action.

class PostsController < ApplicationController
  aserto_authorize_resource
  # aserto_authorize_resource only: %i[show]
  # aserto_authorize_resource except: %i[index]

  def show
    # getting a single post authorized
  end

  def index
    # getting all posts is authorized
  end
end

check!

The check! method in the controller will raise an exception if the user is not able to perform the given action.

def show
  # only users in the "evil_genius" group are allowed to get this resource
  check!(object_id: "evil_genius", object_type: "group", relation: "member")
  @post = Post.find(params[:id])
end

Setting this for every action can be tedious, therefore the aserto_check_resource method is provided to automatically authorize all actions in a RESTful style resource controller. It will use a before action to load the resource into an instance variable and authorize it for every action.

class PostsController < ApplicationController
  aserto_authorize_resource
  # aserto_check_resource only: %i[show], params: { object_id: "evil_genius", object_type: "group", relation: "member" }
  # aserto_check_resource except: %i[index], params: { object_id: "evil_genius", object_type: "group", relation: "member" }

  def show
    # getting a single post authorized
  end

  def index
    # getting all posts is authorized
  end
end

Check Permissions

The current user's permissions can then be checked using the allowed?, visible? and enabled? methods in views and controllers.

<% if allowed? :get, "/posts/:id", @post %>
  <%= link_to "View", @post %>
<% end %>

Development

Prerequisites: - Ruby >= 3.0 to run the code

Run bundle install to install dependencies. Then, run bundle exec rspec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

aserto-rails uses appraisals to test the code base against multiple versions of Rails, as well as the different model adapters.

When first developing, you need to run bundle exec appraisal install, to install the different sets.

You can then run all appraisal files (like CI does), with bundle exec appraisal rake spec or just run a specific set bundle exec appraisal rails_7.0.0 rake spec.

If you'd like to run a specific set of tests within a specific file or folder you can use SPEC=path/to/file/or/folder bundle exec appraisal rails_7.0.0 rake spec rake.

Eg: SPEC=spec/aserto/rails/controller_additions_spec.rb:31 bundle exec appraisal rails_7.0.0 rake spec rake

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/aserto-dev/aserto-rails. This project is intended to be a safe, welcoming space for collaboration.

License

The gem is available as open source under the terms of the Apache-2.0 License.