Page Contents

Authorization Middleware
- Identity Decorator

Authorization Middleware¶

Authorization is applied to your application as a middleware. The AuthorizationMiddleware handles the following responsibilities:

Decorating the request ‘identity’ with a decorator that adds the can, canResult, and applyScope methods if necessary.
Ensuring that authorization has been checked/bypassed in the request.

To use the middleware implement AuthorizationServiceProviderInterface in your application class. Then pass your app instance into the middleware and add the middleware to the queue.

A basic example would be:

namespace App;

use Authorization\AuthorizationService;
use Authorization\AuthorizationServiceProviderInterface;
use Authorization\Middleware\AuthorizationMiddleware;
use Authorization\Policy\OrmResolver;
use Cake\Http\BaseApplication;

class Application extends BaseApplication implements AuthorizationServiceProviderInterface
{
    public function getAuthorizationService(ServerRequestInterface $request, ResponseInterface $response)
    {
        $resolver = new OrmResolver();

        return new AuthorizationService($resolver);
    }

    public function middleware($middlewareQueue)
    {
        // other middleware
        $middlewareQueue->add(new AuthorizationMiddleware($this));

        return $middlewareQueue;
    }
}

The authorization service requires a policy resolver. See the Policies documentation on what resolvers are available and how to use them.

Identity Decorator¶

By default the identity in the request will be decorated (wrapped) with Authorization\IdentityDecorator. The decorator class proxies method calls, array access and property access to the decorated identity object. To access the underlying identity directly use getOriginalData():

$originalUser = $user->getOriginalData();

If your application uses the cakephp/authentication plugin then the Authorization\Identity class will be used. This class implements the Authentication\IdentityInterface in addition to the Authorization\IdentityInterface. This allows you to use the Authentication lib’s component and helper to get the decorated identity.

Using your User class as the Identity¶

If you have an existing User or identity class you can skip the decorator by implementing the Authorization\IdentityInterface and using the identityDecorator middleware option. First lets update our User class:

namespace App\Model\Entity;

use Authorization\AuthorizationServiceInterface;
use Authorization\IdentityInterface;
use Authorization\Policy\ResultInterface;
use Cake\ORM\Entity;

class User extends Entity implements IdentityInterface
{
    /**
     * Authorization\IdentityInterface method
     */
    public function can($action, $resource): bool
    {
        return $this->authorization->can($this, $action, $resource);
    }

    /**
     * Authorization\IdentityInterface method
     */
    public function canResult($action, $resource): ResultInterface
    {
        return $this->authorization->canResult($this, $action, $resource);
    }

    /**
     * Authorization\IdentityInterface method
     */
    public function applyScope($action, $resource)
    {
        return $this->authorization->applyScope($this, $action, $resource);
    }

    /**
     * Authorization\IdentityInterface method
     */
    public function getOriginalData()
    {
        return $this;
    }

    /**
     * Setter to be used by the middleware.
     */
    public function setAuthorization(AuthorizationServiceInterface $service)
    {
        $this->authorization = $service;

        return $this;
    }

    // Other methods
}

Now that our user implements the necessary interface, lets update our middleware setup:

// In your Application::middleware() method;

// Authorization
$middlewareQueue->add(new AuthorizationMiddleware($this, [
    'identityDecorator' => function ($auth, $user) {
        return $user->setAuthorization($auth);
    }
]));

You no longer have to change any existing typehints, and can start using authorization policies anywhere you have access to your user.

If you also use the Authentication plugin make sure to implement both interfaces.:

use Authorization\IdentityInterface as AuthorizationIdentity;
use Authentication\IdentityInterface as AuthenticationIdentity;

class User extends Entity implements AuthorizationIdentity, AuthenticationIdentity
{
    ...

    /**
     * Authentication\IdentityInterface method
     *
     * @return string
     */
    public function getIdentifier()
    {
        return $this->id;
    }

    ...
}

Ensuring Authorization is Applied¶

By default the AuthorizationMiddleware will ensure that each request containing an identity also has authorization checked/bypassed. If authorization is not checked an AuthorizationRequiredException will be raised. This exception is raised after your other middleware/controller actions are complete, so you cannot rely on it to prevent unauthorized access, however it is a helpful aid during development/testing. You can disable this behavior via an option:

$middlewareQueue->add(new AuthorizationMiddleware($this, [
    'requireAuthorizationCheck' => false
]));

Handling Unauthorized Requests¶

By default authorization exceptions thrown by the application are rethrown by the middleware. You can configure handlers for unauthorized requests and perform custom action, e.g. redirect the user to the login page.

The built-in handlers are:

Exception - this handler will rethrow the exception, this is a default behavior of the middleware.
Redirect - this handler will redirect the request to the provided URL.
CakeRedirect - redirect handler with support for CakePHP Router.

Both redirect handlers share the same configuration options:

url - URL to redirect to (CakeRedirect supports CakePHP Router syntax).
exceptions - a list of exception classes that should be redirected. By default only MissingIdentityException is redirected.
queryParam - the accessed request URL will be attached to the redirect URL query parameter (redirect by default).
statusCode - HTTP status code of a redirect, 302 by default.

For example:

use Authorization\Exception\MissingIdentityException;

$middlewareQueue->add(new AuthorizationMiddleware($this, [
    'unauthorizedHandler' => [
        'className' => 'Authorization.Redirect',
        'url' => '/pages/unauthorized',
        'queryParam' => 'redirectUrl',
        'exceptions' => [
            MissingIdentityException::class,
            OtherException::class,
        ],
    ],
]));

All handlers get the thrown exception object given as a parameter. This exception will always be an instance of Authorization\Exception\Exception. In this example the Authorization.Redirect handler just gives you the option to specify which exceptions you want to listen to.

So in this example where we use the Authorization.Redirect handler we can add other Authorization\Exception\Exception based exceptions to the execeptions array if we want to handle them gracefully:

'exceptions' => [
    MissingIdentityException::class,
    ForbiddenException::class
],

See the RedirectHandler source

Configuration options are passed to the handler’s handle() method as the last parameter.

Add a flash message after being redirected by an unauthorized request¶

Currently there is no straightforward way to add a flash message to the unauthorized redirect.

Therefore you need to create your own Handler which adds the flash message (or any other logic you want to happen on redirect)

How to create a custom UnauthorizedHandler¶

Create this file src/Middleware/UnauthorizedHandler/CustomRedirectHandler.php:

<?php
declare( strict_types = 1 );

namespace App\Middleware\UnauthorizedHandler;

use Authorization\Exception\Exception;
use Authorization\Middleware\UnauthorizedHandler\RedirectHandler;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;

class CustomRedirectHandler extends RedirectHandler {
    public function handle( Exception $exception, ServerRequestInterface $request, array $options = [] ): ResponseInterface {
        $response = parent::handle( $exception, $request, $options );
        $request->getFlash()->error( 'You are not authorized to access that location' );
        return $response;
    }
}

Tell the AuthorizationMiddleware that it should use your new custom Handler:

// in your src/Application.php

use Authorization\Exception\MissingIdentityException;
use Authorization\Exception\ForbiddenException;

$middlewareQueue->add(new AuthorizationMiddleware($this, [
    'unauthorizedHandler' => [
        'className' => 'CustomRedirect', // <--- see here
        'url' => '/users/login',
        'queryParam' => 'redirectUrl',
        'exceptions' => [
            MissingIdentityException::class,
            ForbiddenException::class
        ],
        'custom_param' => true,
    ],
]));

As you can see you still have the same config parameters as if we are using Authorization.Redirect as a className.

This is, because we extend our handler based on the RedirectHandler present in the plugin. Therefore all that functionality is present + our own funtionality in the handle() function.

The custom_param appears in the $options array given to you in the handle() function inside your CustomRedirectHandler if you wish to add some more config parameters to your functionality.

You can look at CakeRedirectHandler or RedirectHandler how such a Handler can/should look like.

B CakePHP Authorization 2.x Book

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