ac/kalinka

Flexible authorization library for PHP

0.1.1 2014-04-09 16:54 UTC

README

Build Status

Kalinka helps you determine who's allowed to do what in your app.

API Documentation

This library is for authorization, not authentication. You'll need a different library for actually logging your users in and out, managing passwords, OpenID, and so on. Kalinka is for determining what actions are available to your users after they've logged in.

Installation

You can get Kalinka via composer:

"require": {
    ...
    "ac/kalinka": "dev-master"
}

Getting Started

Create a base abstract Guard class for your app. Guards are where you define your security policies. Policies are just boolean-retuning methods whose names start with "policy". Here is an example:

use AC\Kalinka\Guard\BaseGuard;

abstract class MyAppBaseGuard extends BaseGuard
{
    protected function policyAdmin($subject)
    {
        return $subject->isAdmin();
    }
}

The subject above is the user whose privileges are being checked. This can be an instance of your app's User class (as the code above assumes), or it can be something as simple as the name of the user as a string. The important thing is that it lets you find out everything you need about the user to determine what they're allowed to do.

MyAppBaseGuard is abstract because it doesn't define any actions. Actions are strings which represent various things the subject might want to do, and which you may or may not permit. For your more specific Guard classes, you'll need to provide a getActions method which returns an array:

class DocumentGuard extends MyAppBaseGuard
{
    public function getActions()
    {
        return ["read", "write"];
    }
}

Policies may also accept an object as their second argument, which is a specific resource that the subject is trying to get at. For example, suppose you have Documents that allow access based on whether or not the user owns that particular document, and/or whether the document is "unlocked":

class DocumentGuard extends MyAppBaseGuard
{
    public function getActions()
    {
        return ["read", "write"];
    }

    protected function policyDocumentOwner($subject, $object)
    {
        return ($object->getOwnerId() == $subject->getId());
    }

    protected function policyDocumentUnlocked($subject, $object)
    {
        return !($object->isLocked());
    }
}

When your app wants to do some actual access checks, these are done through an Authorizer. The Authorizer determines what Guard policies are applied in any given situation. You can reference the policies implemented in your Guards, as well as the default "allow" policy that simply always permits access.

If you don't define any policy for an action, it is always denied by default.

For most basic use cases, you can derive from SimpleAuthorizer:

use AC\Kalinka\Authorizer\SimpleAuthorizer;
use MyApp\Guards\CommentGuard;
use MyApp\Guards\DocumentGuard;

class MyAppAuthorizer extends SimpleAuthorizer
{
    public function __construct($subject)
    {
        parent::__construct($subject);

        $this->registerGuards([
            "document" => new DocumentGuard,
            "comment" => new CommentGuard,
            // ... and so on for all your protected resources
        ]);

        $this->registerPolicies([
            "document" => [
                "read" => "allow",
                "write" => "documentOwner"
            ],
            "comment" => [
                "read" => "allow",
                "create" => "allow",
                "delete" => "admin"
            ],
            // ...
        ]);
    }
}

Now after all that, we're ready to do authorization! Whenever you want to check if access to some resource is allowed, just create an instance of your Authorizer class and call the can method:

use MyApp\MyAppAuthorizer;

$auth = new MyAppAuthorizer($currentUser);
if ($auth->can("write", "document", $someDocument)) {
    $someDocument->setContent($newValue);
} else {
    print "Access denied!\n";
}

Combining Policies

Suppose that you only want to allow documents to be edited only if they are unlocked and the user owns them. This can be done by supplying a list of policies instead of a single string:

// ...
$this->registerPolicies([
    "document" => [
        "read" => "allow",
        "write" => [
            "documentUnlocked",
            "documentOwner"
        ]
    ],
    // ...
]);

Sometimes an action is permitted if any one of several different policies allows it, even if the others do not. Suppose that for the purposes of writing documents, being an admin is as good as being the document's owner, but the rule about the document being unlocked still applies to everyone. In that case, you can use an inner list:

// ...
$this->registerPolicies([
    "document" => [
        "read" => "allow",
        "write" => [
            "documentUnlocked",
            ["documentOwner", "admin"]
        ]
    ],
    // ...
]);

The principle here is that the outer list is AND-connected, while inner lists are OR-connected.

If you need something even more complicated than that, you could always implement it as its own policy. Policies can call each other with the checkPolicy() method on BaseGuard.

Roles

SimpleAuthorizer will only work for very straightforward setups, where the same policies apply to everyone. In real systems, it's more common that you have a bunch of different roles that people can belong to, each of which has access to resources under a variety of different circumstances. The easiest way to accomplish this is to extend from RoleAuthorizer, which provides a registerRolePolicies() method that replaces the functionality of SimpleAuthorizer's registerPolicies() method:

use AC\Kalinka\Authorizer\RoleAuthorizer;
use MyApp\Guards\CommentGuard;
use MyApp\Guards\DocumentGuard;

class MyAppAuthorizer extends RoleAuthorizer
{
    public function __construct(MyUserClass $user)
    {
        $roleNames = [];
        foreach ($user->getRoles() as $role) {
            $roleNames[] = $role->getName();
        }
        parent::__construct($user, $roleNames);

        $this->registerGuards([
            "document" => new DocumentGuard,
            "comment" => new CommentGuard,
            // ... and so on for all your protected resources
        ]);

        $this->registerRolePolicies([
            "guest" => [
                "document" => [
                    "read" => "allow",
                ],
                "comment" => [
                    "read" => "allow",
                ]
                // ...
            ],
            "customer" => [
                "document" => [
                    "read" => "allow",
                    "write" => [
                        "documentUnlocked",
                        "documentOwner"
                    ]
                ],
                "comment" => [
                    "read" => "allow",
                    "create" => "allow",
                ],
                // ...
            ],
            // ...
        ]);
    }
}

The roles are supplied as a list of strings. When a permissions check is made, each role is tried individually; if any role assigned to the user allows the action, then it is allowed overall.

This is a much more flexible solution than adding role-like policies to your Guards, as we did above with the policyAdmin() method of MyAppBaseGuard.

The RoleAuthorizer also provides a special role named 'superuser', which automatically allows all actions.

Partially Included Roles

You may sometimes have special situations where the desired permissions don't match up perfectly with your roles. For example, you might have a user who has all the rights of the "contributor" role, but also can act as an "administrator" when it comes to manipulating comments. You can handle this situation with your RoleAuthorizer derivative by using the registerRoleInclusions() method:

use AC\Kalinka\Authorizer\RoleAuthorizer;

class MyAppAuthorizer extends RoleAuthorizer
{
    public function __construct(MyUserClass $user)
    {
        // ...

        if ($user->isCommentAdmin()) {
            $this->registerRoleInclusions([
                "comment" => "administrator"
            ]);
        }
    }
}

It is also possible to include only particular actions from a role:

$this->registerRoleInclusions([
    "comment" => ["update" => "administrator", "delete" => "administrator"]
]);

These included sections are treated as though they were another role; access is permitted if any included policy lists approve it, or if any of the policy lists from the user's regular roles approve it.