# Declarative Authorization The declarative authorization plugin offers an authorization mechanism inspired by _RBAC_. The most notable distinction to other authorization plugins is the declarative approach. That is, authorization rules are not defined programmatically in between business logic but in an authorization configuration. With programmatic authorization rules, the developer needs to specify which roles are allowed to access a specific controller action or a part of a view, which is not DRY. With a growing application code base roles' permissions often change and new roles are introduced. Then, at several places of the source code the changes have to be implemented, possibly leading to omissions and thus hard to find errors. In these cases, a declarative approach as offered by decl_auth increases the development and maintenance efficiency. Plugin features * Authorization at controller action level * Authorization helpers for Views * Authorization at model level * Authorize CRUD (Create, Read, Update, Delete) activities * Query rewriting to automatically only fetch authorized records * DSL for specifying Authorization rules in an authorization configuration * Support for Rails 4 and 5 Requirements * An authentication mechanism * User object in Controller#current_user * (For model security) Setting Authorization.current_user * User objects need to respond to a method `:role_symbols` that returns an array of role symbols See below for installation instructions. There is a decl_auth screencast by Ryan Bates, nicely introducing the main concepts: http://railscasts.com/episodes/188-declarative-authorization ## Quick Start ### Install Declarative Authorization comes with an installer to make setup easy. First, include ae_declarative_authorization in your gemfile. ```ruby gem 'ae_declarative_authorization' ``` Next, bundle and install. $ bundle $ rails g authorization:install [UserModel=User] [field:type field:type ...] [--create-user --commit --user-belongs-to-role] This installer will create a Role model, an admin and a user role, and set a has_and_belongs_to_many relationship between the User model and the Role model. It will also add a `role_symbols` method to the user model to meet declarative_authorization's requirements. The default User model is User. You can override this by simply typing the name of a model as above. You can create the model with the fields provided by using the `--create-user` option. The `--commit` option will run `rake db:migrate` and `rake db:seed`. The `--user-belongs-to-role` option will set up a one-to-many relationship between Users and Roles. That is, each user has a role_id column and can only have one role. Role inheritance can be used in authorization rules. Finally, the installer also copies default authorization rules, as below. ### Generate Authorization Rules To copy a default set of authorization rules which includes CRUD priveleges, run: $ rails g authorization:rules This command will copy the following to `config/authorization_rules.rb`. Remember to implement the requirements of this gem as described in the Installation section at the end of this README if you do not use the above installer. ```ruby authorization do role :guest do # add permissions for guests here, e.g. # has_permission_on :conferences, :to => :read end # permissions on other roles, such as # role :admin do # has_permission_on :conferences, :to => :manage # end # role :user do # has_permission_on :conferences, :to => [:read, :create] # has_permission_on :conferences, :to => [:update, :delete] do # if_attribute :user_id => is {user.id} # end # end # See the readme or GitHub for more examples end privileges do # default privilege hierarchies to facilitate RESTful Rails apps privilege :manage, :includes => [:create, :read, :update, :delete] privilege :create, :includes => :new privilege :read, :includes => [:index, :show] privilege :update, :includes => :edit privilege :delete, :includes => :destroy end ``` ### Controller Authorization For RESTful controllers, add `filter_resource_access`: ```ruby class MyRestfulController < ApplicationController filter_resource_access end ``` For a non-RESTful controller, you can use `filter_access_to`: ```ruby class MyOtherController < ApplicationController filter_access_to :all # or a group: filter_access_to [:action1, :action2] end ``` ### View Authorization Declarative Authorization will use `current_user` to check authorization. ```erb <%= link_to 'Edit Post', edit_post_path(@post) if permitted_to? :update, @post %> ``` ## Authorization Data Model ``` ----- App domain ----|-------- Authorization conf ---------|------- App domain ------ includes includes .--. .---. | v | v .------. can_play .------. has_permission .------------. requires .----------. | User |----------->| Role |----------------->| Permission |<-----------| Activity | '------' * * '------' * * '------------' 1 * '----------' | .-------+------. 1 / | 1 \ * .-----------. .---------. .-----------. | Privilege | | Context | | Attribute | '-----------' '---------' '-----------' ``` In the application domain, each *User* may be assigned to *Roles* that should define the users' job in the application, such as _Administrator_. On the right-hand side of this diagram, application developers specify which *Permissions* are necessary for users to perform activities, such as calling a controller action, viewing parts of a View or acting on records in the database. Note that Permissions consist of an *Privilege* that is to be performed, such as _read_, and a *Context* in that the Operation takes place, such as _companies_. In the authorization configuration, Permissions are assigned to Roles and Role and Permission hierarchies are defined. *Attributes* may be employed to allow authorization according to dynamic information about the context and the current user, e.g. "only allow access on employees that belong to the current user's branch." ## Examples A fully functional example application can be found at http://github.com/stffn/decl_auth_demo_app ## Controller If authentication is in place, there are two ways to enable user-specific access control on controller actions. For resource controllers, which more or less follow the CRUD pattern, `filter_resource_access` is the simplest approach. It sets up instance variables in before filters and calls `filter_access_to` with the appropriate parameters to protect the CRUD methods. ```ruby class EmployeesController < ApplicationController filter_resource_access end ``` See `Authorization::AuthorizationInController::ClassMethods` for options on nested resources and custom member and collection actions. By default, Declarative Authorization will enable `filter_resource_access` compatibility with `strong_parameters`. If you want to disable this behavior, you can use the `:strong_parameters` option. ```ruby class EmployeesController < ApplicationController filter_resource_access :strong_parameters => false end ``` If you prefer less magic or your controller has no resemblance with the resource controllers, directly calling `filter_access_to` may be the better option. Examples are given in the following. E.g. the privilege index users is required for action index. This works as a first default configuration for RESTful controllers, with these privileges easily handled in the authorization configuration, which will be described below. ```ruby class EmployeesController < ApplicationController filter_access_to :all def index end end ``` When custom actions are added to such a controller, it helps to define more clearly which privileges are the respective requirements. That is when the `filter_access_to` call may become more verbose: ```ruby class EmployeesController < ApplicationController filter_access_to :all # this one would be included in :all, but :read seems to be # a more suitable privilege than :auto_complete_for_user_name filter_access_to :auto_complete_for_employee_name, :require => :read def auto_complete_for_employee_name end end ``` For some actions it might be necessary to check certain attributes of the object the action is to be acting on. Then, the object needs to be loaded before the action's access control is evaluated. On the other hand, some actions might prefer the authorization to ignore specific attribute checks as the object is unknown at checking time, so attribute checks and thus automatic loading of objects needs to be enabled explicitly. ```ruby class EmployeesController < ApplicationController filter_access_to :update, :attribute_check => true def update # @employee is already loaded from param[:id] because of :attribute_check end end ``` You can provide the needed object through before_actions. This way, you have full control over the object that the conditions are checked against. Just make sure, your before_actions occur before any of the `filter_access_to` calls. ```ruby class EmployeesController < ApplicationController before_action :new_employee_from_params, :only => :create before_action :new_employee, :only => [:index, :new] filter_access_to :all, :attribute_check => true def create @employee.save! end protected def new_employee_from_params @employee = Employee.new(params[:employee]) end end ``` If the access is denied, a `permission_denied` method is called on the current_controller, if defined, and the issue is logged. For further customization of the filters and object loading, have a look at the complete API documentation of `filter_access_to` in `Authorization::AuthorizationInController::ClassMethods`. ## Views In views, a simple permitted_to? helper makes showing blocks according to the current user's privileges easy: ```erb <% permitted_to? :create, :employees do %> <%= link_to 'New', new_employee_path %> <% end %> ``` Only giving a symbol :employees as context prevents any checks of attributes as there is no object to check against. For example, in case of nested resources a new object may come in handy: ```erb <% permitted_to? :create, Branch.new(:company => @company) do # or @company.branches.new # or even @company.branches %> <%= link_to 'New', new_company_branch_path(@company) %> <% end %> ``` Lists are straight-forward: ```erb <% for employee in @employees do %> <%= link_to 'Edit', edit_employee_path(employee) if permitted_to? :update, employee %> <% end %> ``` See also `Authorization::AuthorizationHelper`. ## Models There are two distinct features for model security built into this plugin: authorizing CRUD operations on objects as well as query rewriting to limit results according to certain privileges. See also Authorization::AuthorizationInModel. ### Model security for CRUD operations To activate model security, all it takes is an explicit enabling for each model that model security should be enforced on, i.e. ```ruby class Employee < ActiveRecord::Base using_access_control end ``` Thus, `Employee.create(...)` fails, if the current user is not allowed to `:create` `:employees` according to the authorization rules. For the application to find out about what happened if an operation is denied, the filters throw `Authorization::NotAuthorized` exceptions. As access control on read are costly, with possibly lots of objects being loaded at a time in one query, checks on read need to be activated explicitly by adding the `:include_read` option. ### Query rewriting through named scopes When retrieving large sets of records from databases, any authorization needs to be integrated into the query in order to prevent inefficient filtering afterwards and to use LIMIT and OFFSET in SQL statements. To keep authorization rules out of the source code, this plugin offers query rewriting mechanisms through named scopes. Thus, ```ruby Employee.with_permissions_to(:read) ``` returns all employee records that the current user is authorized to read. In addition, just like normal named scopes, query rewriting may be chained with the usual find method: ```ruby Employee.with_permissions_to(:read).find(:all, :conditions => ...) ``` If the current user is completely missing the permissions, an `Authorization::NotAuthorized` exception is raised. Through `Model.obligation_conditions`, application developers may retrieve the conditions for manual rewrites. ## Authorization Rules Authorization rules are defined in config/authorization_rules.rb (Or redefine rules files path via `Authorization::AUTH_DSL_FILES`). E.g. ```ruby authorization do role :admin do has_permission_on :employees, :to => [:create, :read, :update, :delete] end end ``` There is a default role `:guest` that is used if a request is not associated with any user or with a user without any roles. So, if your application has public pages, `:guest` can be used to allow access for users that are not logged in. All other roles are application defined and need to be associated with users by the application. If you need to change the default role, you can do so by adding an initializer that contains the following statement: ```ruby Authorization.default_role = :anonymous ``` Privileges, such as :create, may be put into hierarchies to simplify maintenance. So the example above has the same meaning as ```ruby authorization do role :admin do has_permission_on :employees, :to => :manage end end privileges do privilege :manage do includes :create, :read, :update, :delete end end ``` Privilege hierarchies may be context-specific, e.g. applicable to `:employees`. ```ruby privileges do privilege :manage, :employees, :includes => :increase_salary end ``` For more complex use cases, authorizations need to be based on attributes. Note that you then also need to set `:attribute_check => true` in controllers for `filter_access_to`. E.g. if a branch admin should manage only employees of his branch (see `Authorization::Reader` in the API docs for a full list of available operators): ```ruby authorization do role :branch_admin do has_permission_on :employees do to :manage # user refers to the current_user when evaluating if_attribute :branch => is {user.branch} end end end ``` To reduce redundancy in has_permission_on blocks, a rule may depend on permissions on associated objects: ```ruby authorization do role :branch_admin do has_permission_on :branches, :to => :manage do if_attribute :managers => contains {user} end has_permission_on :employees, :to => :manage do if_permitted_to :manage, :branch # instead of # if_attribute :branch => {:managers => contains {user}} end end end ``` Lastly, not only privileges may be organized in a hierarchy but roles as well. Here, project manager inherit the permissions of employees. ```ruby role :project_manager do includes :employee end ``` See also `Authorization::Reader`. ## Testing ae_declarative_authorization provides a few helpers to ease the testing with authorization in mind. In your test_helper.rb, to enable the helpers add ```ruby require 'declarative_authorization/maintenance' class Test::Unit::TestCase include Authorization::TestHelper end ``` For using the test helpers with RSpec, just add the following lines to your spec_helper.rb (somewhere after `require 'spec/rails'`): ```ruby require 'declarative_authorization/maintenance' include Authorization::TestHelper ``` Now, in unit tests, you may deactivate authorization if needed e.g. for test setup and assume certain identities for tests: ```ruby class EmployeeTest < ActiveSupport::TestCase def test_should_read without_access_control do Employee.create(...) end assert_nothing_raised do with_user(admin) do Employee.find(:first) end end end end ``` Or, with RSpec, it would work like this: ```ruby describe Employee do it 'should read' do without_access_control do Employee.create(...) end with_user(admin) do Employee.find(:first) end end end ``` In functional tests, get, posts, etc. may be tested in the name of certain users: ```ruby get_with admin, :index post_with admin, :update, :employee => {...} ``` See `Authorization::TestHelper` for more information. ## Providing the Plugin's Requirements The requirements are * Rails >= 4.2.5.2 and Ruby >= 2.1.x * An authentication mechanism * A user object returned by Controller#current_user * An array of role symbols returned by User#role_symbols * (For model security) Setting Authorization.current_user to the request's user Of the various ways to provide these requirements, here is one way employing restful_authentication. * Install restful_authentication cd vendor/plugins && git clone git://github.com/technoweenie/restful-authentication.git restful_authentication cd ../.. && ruby script/generate authenticated user sessions * Move "include AuthenticatedSystem" to ApplicationController * Add +filter_access_to+ calls as described above. * If you'd like to use model security, add a before_action that sets the user globally to your ApplicationController. This is thread-safe. before_action :set_current_user protected def set_current_user Authorization.current_user = current_user end * Add roles field to the User model through a :+has_many+ association (this is just one possible approach; you could just as easily use :+has_many+ :+through+ or a serialized roles array): * create a migration for table roles class CreateRoles < ActiveRecord::Migration def self.up create_table "roles" do |t| t.column :title, :string t.references :user end end def self.down drop_table "roles" end end * create a model Role, class Role < ActiveRecord::Base belongs_to :user end * add +has_many+ :+roles+ to the User model and a roles method that returns the roles as an Array of Symbols, e.g. class User < ActiveRecord::Base has_many :roles def role_symbols (roles || []).map {|r| r.title.to_sym} end end * add roles to your User objects using e.g. user.roles.create(:title => "admin") Note: If you choose to generate an Account model for restful_authentication instead of a User model as described above, you have to customize the examples and create a ApplicationController#current_user method. ## Debugging Authorization Currently, the main means of debugging authorization decisions is logging and exceptions. Denied access to actions is logged to `warn` or `info`, including some hints about what went wrong. All bang methods throw exceptions which may be used to retrieve more information about a denied access than a Boolean value. ## License Released under MIT license. Copyright (c) 2008 Steffen Bartsch, TZI, Universität Bremen, Germany Copyright (c) 2011-2017 AppFolio, Inc.