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ACL

A simple Role based Access Control List build on Zend Framework 2 ACL.

Introduction

Northern\Acl is a role based ACL that allows for easy definition of permissions for specific roles. Roles can inherit from other roles. Simply by storing a role against a user, using that role would allow you to test if that role is permitted a certain access criteria.

Installation

To use Northern\Acl add it to your project using Composer:

"northern/acl": "1.*"

Usage

To use Northern\Acl start by defining a permissions list. We can start with an empty list:

$permissions = [
   'roles'     => [],
   'resources' => [],
   'rules'     => [],
];

Our permissions list contains three top-level requirements, roles, resources and rules. The idea behind a role based ACL is that a specific role has access to resources through specified rules. Don't confuse the elements you define in this list with 'real' objects in your application. The permissions list is simply a structure (or model) we test against, it is static and therefore it doesn't need to be stored in a database but can simply be defined in a business object in your application as part of your business rules.

Let's add some permissions..

For the purpose of this demonstration we define four roles; guest, member, author and admin. For the sake of argument, we define the resources for a simple blog so we have post and comment as resources:

$permissions = [
   'roles'     => [
      ['name' => 'guest'],
      ['name' => 'member', 'parent' => 'guest'],
      ['name' => 'author', 'parent' => 'member'],
      ['name' => 'admin',  'parent' => 'author'],
   ],
   'resources' => [
      ['name' => 'post'],
      ['name' => 'comment'],
   ],
   'rules'     => [],
];

Easy as. Now lets define a rule that allows guests to view both posts and comments:

$permissions = [
   'roles'     => [
      ['name' => 'guest'],
      ['name' => 'member', 'parent' => 'guest'],
      ['name' => 'author', 'parent' => 'member'],
      ['name' => 'admin',  'parent' => 'author'],
   ],
   'resources' => [
      ['name' => 'post'],
      ['name' => 'comment'],
   ],
   'rules'     => [
      [
         'access'      => 'allow',
         'role'        => 'guest',
         'permissions' => ['view'],
         'resources'   => ['post', 'comment'],
      ]
   ],
];

As you can see, the rule is pretty straight forward. both permissions and resources can either be set as single values or as an array. Let's create a rule that allows members to create comments:

$permissions = [
   'roles'     => [
      ['name' => 'guest'],
      ['name' => 'member', 'parent' => 'guest'],
      ['name' => 'author', 'parent' => 'member'],
      ['name' => 'admin',  'parent' => 'author'],
   ],
   'resources' => [
      ['name' => 'post'],
      ['name' => 'comment'],
   ],
   'rules'     => [
      [
         'access'      => 'allow',
         'role'        => 'guest',
         'permissions' => ['view'],
         'resources'   => ['post', 'comment'],
      ], [
         'access'      => 'allow',
         'role'        => 'member',
         'permissions' => ['create'],
         'resources'   => ['comment'],
      ]
   ],
];

Great. Now let's fill in the rest of the permissions:

$permissions = [
   'roles'     => [
      ['name' => 'guest'],
      ['name' => 'member', 'parent' => 'guest'],
      ['name' => 'author', 'parent' => 'member'],
      ['name' => 'admin',  'parent' => 'author'],
   ],
   'resources' => [
      ['name' => 'post'],
      ['name' => 'comment'],
   ],
   'rules'     => [
      [
         'access'      => 'allow',
         'role'        => 'guest',
         'permissions' => ['view'],
         'resources'   => ['post', 'comment'],
      ], [
         'access'      => 'allow',
         'role'        => 'member',
         'permissions' => ['create'],
         'resources'   => ['comment'],
      ], [
         'access'      => 'allow',
         'role'        => 'author',
         'permissions' => ['create', 'edit', 'delete'],
         'resources'   => ['post'],
      ], [
         'access'      => 'allow',
         'role'        => 'admin',
         'permissions' => NULL,
         'resources'   => NULL,
      ]
   ],
];

We added the author permissions and set the admin permissions to allow all access on all resources.

To use these permissions we need to load them into the ACL, like this:

$acl = new \Northern\Acl\Acl();
$acl->loadPermissions( $permissions );

The $acl instance will allow us to test for permissions through the isAllowed method. However, the true power of Northern\Acl is in the Permissions class of which need to create a subclass:

class Permissions extends \Northern\Acl\Permissions {

    public function getRoles()
    {
       return ['guest', 'member', 'author', 'admin'];
    }

    public function getResources()
    {
       return ['post', 'comment'];
    }

    public function getRules()
    {
          return ['create', 'view', 'edit', 'delete'];
    }

}

We can now use this Permissions class to do some magic:

$acl = new \Northern\Acl\Acl();
$acl->loadPermissions( $permissions );

$authorPermissions = new Permissions( $acl, 'author' );

$authorPermissions->canCreatePost();
// TRUE!

As you can see. The Permissions instance allows you to test for permissions on a role through magic methods.

That's all folks!