Rails plugin for a generic actor/resource permissions framework
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README.rdoc

Credentials

Description

A generic actor/resource permission framework.

Installation

  • sudo gem install credentials

Examples

class User
  credentials do |user|
    # Users should only be able to edit their own details...
    user.can :edit, User, :if => lambda { |a, b| if a == b }

    # ...unless they are administrators!
    user.can :edit, User, :if => :admin?
  end
end

a = User.new
b = User.new :admin => true
a.can_edit?(a) #=> true
a.can_edit?(b) #=> false
b.can_edit?(b) #=> true
b.can_edit?(a) #=> true

Philosophy

Credentials is NOT a role-based permission system. Permissions are based on code, not on database objects. That said, there's nothing to stop you from doing something like this:

class User
  has_and_belongs_to_many :roles

  credentials do |user|
    user.can :access, :admin_pages, :if => :admin?
  end

  def admin?
    !roles.find_by_name("admin").nil?
  end
end

I just figured there were dozens of systems out there for implementing role-based permissions, and everyone likes to do it differently, so I wouldn't reinvent the wheel. Instead, I wanted to focus on capturing the logic behind permissions, and avoid having to grant individual permissions for things that should be implemented algorithmically.

For example, say you want to allow users to edit user profiles under the following rules:

  • Users can edit their own profile

  • Admin users can edit any profile

  • Selected users can edit selected other individual profiles

Ordinarily, that's three separate checks: sure, I can bundle these up into a method on my User object, but the controller still needs to call that method and take appropriate action if it's not satisfied.

With Credentials, I can write one method in my ApplicationController, and then do this:

class UsersController
  def update
    @user = User.find params[:id]
    requires_permission_to :edit, @user
    @user.update_attributes params[:user]
    # ...
  end
end

The requires_permission_to method would call current_user.can?(:edit, @user), and, if appropriate, raise an exception which would get handled by Rails and turned into a nice pretty error page.

To do

  • Better support for groups would make integration with RBA systems easier.

License

Copyright © 2009 Matt Powell (fauxparse@gmail.com)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.