AttributeExt

AttributeExt provides additional access control for rails model attributes. It contains two modules one to protect attributes from mass assignment and one to hide attributes when serializing models.

Just add the following to your Gemfile

gem 'attribute_ext', '~> 1.4'

and run bundle command.

You can also install AttributeExt as a rails plugin by cloning the repository to vendor/plugins.

Protects attributes from mass assignment using rails mass assignment authorizer. Also support Proc blocks.

Examples:

Always allow mass assignment for attribute.

class User < ActiveRecord::Base
  safe_attributes :attribute
end

Attributes 'login', 'admin' and 'status' can only be mass assigned if current user is an admin.

class User < ActiveRecord::Base
  safe_attributes :login, :admin, :status, :if => Proc.new { User.current.admin? }
end

Message text can not be mass assigned when post is locked.

class Message < ActiveRecord::Base
  safe_attributes :text, :unless => :locked?
  safe_attributes :body, :unless => Proc.new { |msg| msg.locked? }
end

Symbol conditions will be send to current model object with no arguments. The two lines above are equivalent.

With Rails 3 a role can be given when creating or updating an model. This role will also be available in SafeAttributes.

class User < ActiveRecord::Base
  safe_attributes :login, :as => :admin
end

or

class User < ActiveRecord::Base
  safe_attributes :login, :if => Proc.new { |user,role| role == :admin }
end

Default role and role mapper:

SafeAttributes provides helper for handling roles including a method to set a new default role as well as a method to map roles to other values. Changes to role will only affect SafeAttributes and will not be given to Rails 3.1 mass assignment authorizer.

Set default role that will be used if given role is nil or :default.

AttributeExt::SafeAttributes.default_role = :new_default

Role values can be restricted to specific values using the role mapper.

AttributeExt::SafeAttributes.role_mapper = Proc.new do |role|
  [:guest, :user, :admin].include?(role) ? role : :guest
end

or

AttributeExt::SafeAttributes.role_mapper do |role|
  [:guest, :user, :admin].include?(role) ? role : :guest
end

The role mapper is especially usefull if you want the current user model be the default role.

AttributeExt::SafeAttributes.role_mapper do |role|
  role.is_a?(User) ? role : User.current
end

You can perform checks like this now:

class User < ActiveRecord::Base
  safe_attribute :email, :if => Proc.new { |user,role| user == role or role.admin? }
end

Now a user can edit his own emails or all email if he is an admin.

Hides attributes when converting model to XML or JSON. Attributes can be dynamically hidden using if or unless Procs.

Examples:

Only shows API access key when user has API access.

class User < ActiveRecord::Base
  hide_attributes :api_access_key, :unless => Proc.new { |user| user.api_access? }
end

Always hide password hash and password salt. Hide email if user do not want to show his email.

class User < ActiveRecord::Base
  hide_attributes :password_hash, :password_salt
  hide_attributes :email, :if => Proc.new { |user| user.hide_email? }
end

Additional options are available in if and unless blocks:

Only hide email when serialzing to json.

class User < ActiveRecord::Base
  hide_attributes :email, :if => Proc.new { |user, format| format == :json }
end

Simpler format conditions can be defined using :only and :except parameters:

class User < ActiveRecord::Base
  hide_attributes :email, :only => :json
  hide_attributes :special_attr, :except => [:xml, :json]
end

Both parameters accept single attributes and arrays. When :only or :except is given the :on_hash option will be ignored.

Hide user_id if associated user model will be included. This rule will also apply when calling serializable_hash.

class Event < ActiveRecord::Base
  belongs_to :user
  hide_attributes :user_id, :on_hash => true, :if => Proc.new { |event, format, opts| opts[:include].include?(:user) }
end

By default rules do not apply when serializing to hash.

AttributeExt provides a RSpec matcher that can be used to test own safe attributes rules.

Add

require 'attribute_ext/rspec'

to your spec_helper.rb and use it like this:

model.should have_no_safe_attributes.as(:guest, 'Guest').and_as(:blocked_user, 'Blocked User')
model.should have_safe_attributes(:name, :message)
model.should have_safe_attributes(:attribute).as(:admin, 'Admin')

The matcher will generate well formatted descriptions when running RSpec with -fd:

should have no safe attributes as Guest and as Blocked User
should have safe attributes name, message as default
should have safe attributes attribute as Admin

Copyright (C) 2011 Jan Graichen

AttributeExt is licensed under the Apache License, Version 2.0. See LICENSE for more information.