Blog Tutorial - Authentication and Authorization

Following our Blog Tutorial example, imagine we wanted to secure access to certain URLs, based on the logged-in user. We also have another requirement: to allow our blog to have multiple authors who can create, edit, and delete their own articles while disallowing other authors from making changes to articles they do not own.

Authentication (Login and Logout)

We’re now ready to add our authentication layer. In CakePHP this is handled by the Cake\Controller\Component\AuthComponent, a class responsible for requiring login for certain actions, handling user login and logout, and also authorizing logged-in users to the actions they are allowed to reach.

To add this component to your application open your src/Controller/AppController.php file and add the following lines:

// src/Controller/AppController.php

namespace App\Controller;

use Cake\Controller\Controller;
use Cake\Event\Event;

class AppController extends Controller
{
    //...

    public function initialize()
    {
        $this->loadComponent('Flash');
        $this->loadComponent('Auth', [
            'loginRedirect' => [
                'controller' => 'Articles',
                'action' => 'index'
            ],
            'logoutRedirect' => [
                'controller' => 'Pages',
                'action' => 'display',
                'home'
            ]
        ]);
    }

    public function beforeFilter(Event $event)
    {
        $this->Auth->allow(['index', 'view', 'display']);
    }
    //...
}

There is not much to configure, as we used the conventions for the users table. We just set up the URLs that will be loaded after the login and logout actions is performed, in our case to /articles/ and / respectively.

What we did in the beforeFilter() function was to tell the AuthComponent to not require a login for all index() and view() actions, in every controller. We want our visitors to be able to read and list the entries without registering in the site.

Now, we need to be able to register new users, save their username and password, and more importantly, hash their password so it is not stored as plain text in our database. Let’s tell the AuthComponent to let un-authenticated users access the users add function and implement the login and logout action:

// src/Controller/UsersController.php
namespace App\Controller;

use App\Controller\AppController;
use Cake\Event\Event;

class UsersController extends AppController
{
    // Other methods..

    public function beforeFilter(Event $event)
    {
        parent::beforeFilter($event);
        // Allow users to register and logout.
        // You should not add the "login" action to allow list. Doing so would
        // cause problems with normal functioning of AuthComponent.
        $this->Auth->allow(['add', 'logout']);
    }

    public function login()
    {
        if ($this->request->is('post')) {
            $user = $this->Auth->identify();
            if ($user) {
                $this->Auth->setUser($user);
                return $this->redirect($this->Auth->redirectUrl());
            }
            $this->Flash->error(__('Invalid username or password, try again'));
        }
    }

    public function logout()
    {
        return $this->redirect($this->Auth->logout());
    }
}

Password hashing is not done yet, we need an Entity class for our User in order to handle its own specific logic. Create the src/Model/Entity/User.php entity file and add the following:

// src/Model/Entity/User.php
namespace App\Model\Entity;

use Cake\Auth\DefaultPasswordHasher;
use Cake\ORM\Entity;

class User extends Entity
{

    // Make all fields mass assignable except for primary key field "id".
    protected $_accessible = [
        '*' => true,
        'id' => false
    ];

    // ...

    protected function _setPassword($password)
    {
        if (strlen($password) > 0) {
            return (new DefaultPasswordHasher)->hash($password);
        }
    }

    // ...
}

Now every time the password property is assigned to the user it will be hashed using the DefaultPasswordHasher class. We’re just missing a template view file for the login function. Open up your src/Template/Users/login.ctp file and add the following lines:

<!-- File: src/Template/Users/login.ctp -->

<div class="users form">
<?= $this->Flash->render() ?>
<?= $this->Form->create() ?>
    <fieldset>
        <legend><?= __('Please enter your username and password') ?></legend>
        <?= $this->Form->control('username') ?>
        <?= $this->Form->control('password') ?>
    </fieldset>
<?= $this->Form->button(__('Login')); ?>
<?= $this->Form->end() ?>
</div>

You can now register a new user by accessing the /users/add URL and log in with the newly created credentials by going to /users/login URL. Also, try to access any other URL that was not explicitly allowed such as /articles/add, you will see that the application automatically redirects you to the login page.

And that’s it! It looks too simple to be true. Let’s go back a bit to explain what happened. The beforeFilter() function is telling the AuthComponent to not require a login for the add() action in addition to the index() and view() actions that were already allowed in the AppController’s beforeFilter() function.

The login() action calls the $this->Auth->identify() function in the AuthComponent, and it works without any further config because we are following conventions as mentioned earlier. That is, having a Users table with a username and a password column, and use a form posted to a controller with the user data. This function returns whether the login was successful or not, and in the case it succeeds, then we redirect the user to the configured redirection URL that we used when adding the AuthComponent to our application.

The logout works by just accessing the /users/logout URL and will redirect the user to the configured logoutUrl formerly described. This URL is the result of the AuthComponent::logout() function on success.

Authorization (who’s allowed to access what)

As stated before, we are converting this blog into a multi-user authoring tool, and in order to do this, we need to modify the articles table a bit to add the reference to the Users table:

ALTER TABLE articles ADD COLUMN user_id INT(11);

Also, a small change in the ArticlesController is required to store the currently logged in user as a reference for the created article:

// src/Controller/ArticlesController.php

public function add()
{
    $article = $this->Articles->newEntity();
    if ($this->request->is('post')) {
        $article = $this->Articles->patchEntity($article, $this->request->getData());
        // Added this line
        $article->user_id = $this->Auth->user('id');
        // You could also do the following
        //$newData = ['user_id' => $this->Auth->user('id')];
        //$article = $this->Articles->patchEntity($article, $newData);
        if ($this->Articles->save($article)) {
            $this->Flash->success(__('Your article has been saved.'));
            return $this->redirect(['action' => 'index']);
        }
        $this->Flash->error(__('Unable to add your article.'));
    }
    $this->set('article', $article);

    // Just added the categories list to be able to choose
    // one category for an article
    $categories = $this->Articles->Categories->find('treeList');
    $this->set(compact('categories'));
}

The user() function provided by the component returns any column from the currently logged in user. We used this method to add the data into the request info that is saved.

Let’s secure our app to prevent some authors from editing or deleting the others’ articles. Basic rules for our app are that admin users can access every URL, while normal users (the author role) can only access the permitted actions. Again, open the AppController class and add a few more options to the Auth config:

// src/Controller/AppController.php

public function initialize()
{
    $this->loadComponent('Flash');
    $this->loadComponent('Auth', [
        'authorize' => ['Controller'], // Added this line
        'loginRedirect' => [
            'controller' => 'Articles',
            'action' => 'index'
        ],
        'logoutRedirect' => [
            'controller' => 'Pages',
            'action' => 'display',
            'home'
        ]
    ]);
}

public function isAuthorized($user)
{
    // Admin can access every action
    if (isset($user['role']) && $user['role'] === 'admin') {
        return true;
    }

    // Default deny
    return false;
}

We just created a simple authorization mechanism. Users with the admin role will be able to access any URL in the site when logged-in. All other users – those with the author role – will have the same access as users who aren’t logged-in.

This is not exactly what we want. We need to supply more rules to our isAuthorized() method. However instead of doing it in AppController, we’ll delegate supplying those extra rules to each individual controller. The rules we’re going to add to ArticlesController should permit authors to create articles but prevent authors from editing articles they do not own. Add the following content to your ArticlesController.php:

// src/Controller/ArticlesController.php

public function isAuthorized($user)
{
    // All registered users can add articles
    if ($this->request->getParam('action') === 'add') {
        return true;
    }

    // The owner of an article can edit and delete it
    if (in_array($this->request->getParam('action'), ['edit', 'delete'])) {
        $articleId = (int)$this->request->getParam('pass.0');
        if ($this->Articles->isOwnedBy($articleId, $user['id'])) {
            return true;
        }
    }

    return parent::isAuthorized($user);
}

We’re now overriding the AppController’s isAuthorized() call and internally checking if the parent class is already authorizing the user. If he isn’t, then just allow him to access the add action, and conditionally access edit and delete. One final thing has not been implemented. To tell whether or not the user is authorized to edit the article, we’re calling a isOwnedBy() function in the Articles table. Let’s then implement that function:

// src/Model/Table/ArticlesTable.php

public function isOwnedBy($articleId, $userId)
{
    return $this->exists(['id' => $articleId, 'user_id' => $userId]);
}

This concludes our simple authentication and authorization tutorial. For securing the UsersController you can follow the same technique we did for ArticlesController. You could also be more creative and code something more general in AppController based on your own rules.

Should you need more control, we suggest you read the complete Auth guide in the Authentication section where you will find more about configuring the component, creating custom Authorization classes, and much more.

Suggested Follow-up Reading

  1. Code Generation with Bake Generating basic CRUD code
  2. Authentication: User registration and login