Authorization Adapter

Active Admin offers the ability to define and use your own authorization adapter. If implemented, the ‘#authorized?’ will be called when an action is taken. By default, ‘#authorized?’ returns true.

Setting up your own AuthorizationAdapter

Setting up your own AuthorizationAdapter is easy! The following example shows how to set up and tie your authorization adapter class to Active Admin:

# app/models/only_authors_authorization.rb
class OnlyAuthorsAuthorization < ActiveAdmin::AuthorizationAdapter

  def authorized?(action, subject = nil)
    case subject
    when normalized(Post)
      # Only let the author update and delete posts
      if action == :update || action == :destroy
        subject.author == user
      else
        true
      end
    else
      true
    end
  end

end

In order to hook up OnlyAuthorsAuthorization to Active Admin, go to your application’s config/initializers/active_admin.rb and add/modify the line:

config.authorization_adapter = "OnlyAuthorsAuthorization"

Authorization adapters can be configured per ActiveAdmin namespace as well, for example:

ActiveAdmin.setup do |config|
  config.namespace :admin do |ns|
    ns.authorization_adapter = "AdminAuthorization"
  end
  config.namespace :my do |ns|
    ns.authorization_adapter = "DashboardAuthorization"
  end
end

Now, whenever a controller action is performed, the OnlyAuthorsAuthorization’s #authorized? method will be called.

Getting Access to the Current User

From within your authorization adapter, you can call the #user method to retrieve the current user.

class OnlyAdmins < ActiveAdmin::AuthorizationAdapter

  def authorized?(action, subject = nil)
    user.admin?
  end

end

Scoping Collections in Authorization Adapters

ActiveAdmin::AuthorizationAdapter also provides a hook method (#scope_collection) for the adapter to scope the resource’s collection. For example, you may want to centralize the scoping:

class OnlyMyAccount < ActiveAdmin::AuthorizationAdapter

  def authorized?(action, subject = nil)
    subject.account == user.account
  end

  def scope_collection(collection, action = Auth::READ)
    collection.where(account_id: user.account_id)
  end

end

All collections presented on Index Screens will be passed through this method and will be scoped accordingly.

Managing Access to Pages

Pages, just like resources, get authorized too. When authorizing a page, the subject will be an instance of ActiveAdmin::Page.

class OnlyDashboard < ActiveAdmin::AuthorizationAdapter
  def authorized?(action, subject = nil)
    case subject
    when ActiveAdmin::Page
      action == :read &&
        subject.name == "Dashboard" &&
        subject.namespace.name == :admin
    else
      false
    end
  end
end

Action Types

By default Active Admin simplifies the controller actions into 4 actions:

  • :read - This controls if the user can view the menu item as well as the index and show screens.
  • :create - This controls if the user can view the new screen and submit the form to the create action.
  • :update - This controls if the user can view the edit screen and submit the form to the update action.
  • :destroy - This controls if the user can delete a resource.

Each of these actions is available as a constant. Eg: :read is available as ActiveAdmin::Authorization::READ.

Checking for Authorization in Controllers and Views

Active Admin provides a helper method to check if the current user is authorized to perform an action on a subject.

Simply use the #authorized?(action, subject) method to check.

ActiveAdmin.register Post do

  index do
    column :title
    column '' do |post|
      link_to 'Edit', admin_post_path(post) if authorized? :update, post
    end
  end

end

If you are implementing a custom controller action, you can use the #authorize! method to raise an ActiveAdmin::AccessDenied exception.

ActiveAdmin.register Post do

  member_action :publish, method: :post do
    post = Post.find(params[:id])

    authorize! :publish, post
    post.publish!

    flash[:notice] = "Post has been published"
    redirect_to [:admin, post]
  end

  action_item :publish, only: :show do
    if !post.published? && authorized?(:publish, post)
      link_to "Publish", publish_admin_post_path(post), method: :post
    end
  end

end

Using the CanCan Adapter

Sub-classing ActiveAdmin::AuthorizationAdapter is fairly low level. Many times it’s nicer to have a simpler DSL for managing authorization. Active Admin provides an adapter out of the box for CanCan and CanCanCan.

To use the CanCan adapter, simply update the configuration in the Active Admin initializer:

config.authorization_adapter = ActiveAdmin::CanCanAdapter

You can also specify a method to be called on unauthorized access. This is necessary in order to prevent a redirect loop that can happen if a user tries to access a page they don’t have permissions for (see #2081).

config.on_unauthorized_access = :access_denied

The method access_denied would be defined in application_controller.rb. Here is one example that redirects the user from the page they don’t have permission to access to a resource they have permission to access (organizations in this case), and also displays the error message in the browser:

class ApplicationController < ActionController::Base
  protect_from_forgery

  def access_denied(exception)
    redirect_to admin_organizations_path, alert: exception.message
  end
end

By default this will use the ability class named “Ability”. This can also be changed from the initializer:

config.cancan_ability_class = "MyCustomAbility"

Now you can simply use CanCan or CanCanCan the way that you would expect and Active Admin will use it for authorization:

# app/models/ability.rb
class Ability
  include CanCan::Ability

  def initialize(user)
    can :manage, Post
    can :read, User
    can :manage, User, id: user.id
    can :read, ActiveAdmin::Page, name: "Dashboard", namespace_name: :admin
  end

end

To view more details about the API’s, visit project pages of CanCan and CanCanCan.

Using the Pundit Adapter

Active Admin provides an adapter out of the box also for Pundit.

To use the Pundit adapter, simply update the configuration in the Active Admin initializer:

config.authorization_adapter = ActiveAdmin::PunditAdapter

You can simply use Pundit the way that you would expect and Active Admin will use it for authorization. Check Pundit’s documentation to set up Pundit in your application. If you want to use batch actions just ensure that destroy_all? method is defined in your policy class. You can use this template policy in your application instead of default one generated by Pundit’s rails g pundit:install command.

Copyright 2011 Greg Bell and VersaPay