PHP API: Authentication

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PHP API: Authentication

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By Josh Cunningham

This tutorial demonstrates how to add authentication and authorization to a PHP API. We recommend that you log in to follow this quickstart with examples configured for your account.

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System requirements: PHP 7.3 or greater | Composer

New to Auth0? Learn how Auth0 works and read about implementing API authentication and authorization using the OAuth 2.0 framework.

Configure Auth0 APIs

Create an API

In the APIs section of the Auth0 dashboard, click Create API. Provide a name and an identifier for your API, for example, https://quickstarts/api. You will use the identifier as an audience later, when you are configuring the Access Token verification. Leave the Signing Algorithm as RS256.

Create API

By default, your API uses RS256 as the algorithm for signing tokens. Since RS256 uses a private/public keypair, it verifies the tokens against the public key for your Auth0 account. The public key is in the JSON Web Key Set (JWKS) format, and can be accessed here.

We recommend using the default RS256 signing algorithm for your API. If you need to use the HS256 algorithm, see the HS256 integration sample.

Define permissions

Permissions let you define how resources can be accessed on behalf of the user with a given access token. For example, you might choose to grant read access to the messages resource if users have the manager access level, and a write access to that resource if they have the administrator access level.

You can define allowed permissions in the Permissions tab of the Auth0 Dashboard's APIs section.

Configure Permissions

This example uses the read:messages scope.

This example demonstrates:

  • How to check for a JSON Web Token (JWT) in the Authorization header of an incoming HTTP request.

  • How to check if the token is valid, using the JSON Web Key Set (JWKS) for your Auth0 account. To learn more about validating Access Tokens, see Validate Access Tokens.

Validate Access Tokens

Install dependencies

In this example, token validation is done with the Auth0 PHP SDK, which can be applied to any endpoints you wish to protect. The kodus/file-cache is a PSR-16 compliant caching library to store the contents of the public keys used to check the token signature. The bramus/router library is used in this example for simple API URLs and is not required for your application.

composer require auth0/auth0-php kodus/file-cache bramus/router

Composer is a tool for dependency management in PHP. It allows you to declare the dependent libraries your project needs and it will install them in your project for you. See Composer's getting started doc for information on how to use it.

Configure JWT Validation

Create an instance of TokenVerifier with your Auth0 domain as a URL and your API audience. We will also create methods which will be called to return a message when a request is made to a protected endpoint.

<?php
// src/Main.php

namespace App;

use Auth0\SDK\Exception\InvalidTokenException;
use Auth0\SDK\Helpers\JWKFetcher;
use Auth0\SDK\Helpers\Tokens\AsymmetricVerifier;
use Auth0\SDK\Helpers\Tokens\TokenVerifier;
use Kodus\Cache\FileCache;

class Main {

    protected $issuer;
    protected $audience;
    protected $token;
    protected $tokenInfo;

    public function __construct( $issuer, $audience ) {
        $this->issuer = $issuer;
        $this->audience = $audience;
    }

    public function setCurrentToken($token) {
        $cacheHandler = new FileCache('./cache', 600);
        $jwksUri      = $this->issuer . '.well-known/jwks.json';

        $jwksFetcher   = new JWKFetcher($cacheHandler, [ 'base_uri' => $jwksUri ]);
        $sigVerifier   = new AsymmetricVerifier($jwksFetcher);
        $tokenVerifier = new TokenVerifier($this->issuer, $this->audience, $sigVerifier);

        try {
            $this->tokenInfo = $tokenVerifier->verify($token);
            $this->token = $token;
        }
        catch(InvalidTokenException $e) {
            // Handle invalid JWT exception ...
        }
    }

    // This endpoint doesn't need authentication
    public function publicEndpoint() {
        return array(
            "status" => "ok",
            "message" => "Hello from a public endpoint! You don't need to be authenticated to see this."
        );
    }

    public function privateEndpoint() {
        return array(
            "status" => "ok",
            "message" => "Hello from a private endpoint! You need to be authenticated to see this."
        );
    }
}

To include this class with Composer autoloading, add the following to your composer.json:

{
    // ...
    "autoload": {
        "psr-4": {
            "App\\": "src/"
        }
    }
}

Protect API Endpoints

The routes shown below are available for the following requests:

  • GET /api/public: available for non-authenticated requests
  • GET /api/private: available for authenticated requests containing an Access Token with no additional scopes
  • GET /api/private-scoped: available for authenticated requests containing an Access Token with the read:messages scope granted

The before hook from the router package can be used to configure which routes are to be protected. For example, you may wish to protect all routes under a URL of /api/private.

// index.php

// ...
// Require composer autoloader
require __DIR__ . '/vendor/autoload.php';

$app = new \App\Main( 'https://YOUR_DOMAIN/', 'YOUR_API_IDENTIFIER' );

// Create Router instance
$router = new \Bramus\Router\Router();

// Activate CORS
function sendCorsHeaders() {
  header("Access-Control-Allow-Origin: *");
  header("Access-Control-Allow-Headers: Authorization");
  header("Access-Control-Allow-Methods: GET,HEAD,PUT,PATCH,POST,DELETE");
}

$router->options('/.*', function() {
    sendCorsHeaders();
});

sendCorsHeaders();

// Check JWT on private routes
$router->before('GET', '/api/private.*', function() use ($app) {

  $requestHeaders = apache_request_headers();

  if (!isset($requestHeaders['authorization']) && !isset($requestHeaders['Authorization'])) {
    header('HTTP/1.0 401 Unauthorized');
    header('Content-Type: application/json; charset=utf-8');
    echo json_encode(array("message" => "No token provided."));
    exit();
  }

  $authorizationHeader = isset($requestHeaders['authorization']) ? $requestHeaders['authorization'] : $requestHeaders['Authorization'];

  if ($authorizationHeader == null) {
    header('HTTP/1.0 401 Unauthorized');
    header('Content-Type: application/json; charset=utf-8');
    echo json_encode(array("message" => "No authorization header sent."));
    exit();
  }

  $authorizationHeader = str_replace('bearer ', '', $authorizationHeader);
  $token = str_replace('Bearer ', '', $authorizationHeader);

  try {
    $app->setCurrentToken($token);
  }
  catch(\Auth0\SDK\Exception\CoreException $e) {
    header('HTTP/1.0 401 Unauthorized');
    header('Content-Type: application/json; charset=utf-8');
    echo json_encode(array("message" => $e->getMessage()));
    exit();
  }
});

With this configuration, any time an endpoint which includes /api/private is reached, a valid JWT Access Token will be required before the resource can be released. With this in place, private routes can be defined.

// index.php

// This route doesn't need authentication
$router->get('/api/public', function() use ($app){
  header('Content-Type: application/json; charset=utf-8');
  echo json_encode($app->publicEndpoint());
});

$router->get('/api/private', function() use ($app){
  header('Content-Type: application/json; charset=utf-8');
  echo json_encode($app->privateEndpoint());
});

Protect endpoints with specific scopes

To add authorization you need to define the method checkScope to check for a particular scope in the Access Token.

// src/Main.php

class Main {
    // ...

    public function checkScope($scope){
      if ($this->tokenInfo){
        $scopes = explode(" ", $this->tokenInfo->scope);
        foreach ($scopes as $s){
          if ($s === $scope)
            return true;
        }
      }

      return false;
    }

    public function privateScopedEndpoint() {
      return array(
        "status" => "ok",
        "message" => "Hello from a private endpoint! You need to be authenticated and have a scope of read:messages to see this."
      );
    }

    // ...
}

The function privateScopedEndpoint will return the message when a request is made from a protected endpoint, and the Access Token has a scope of read:messages.

Add a before hook to the router to configure routes that require the scope of read:messages.

// index.php

// Check for read:messages scope
$router->before('GET', '/api/private-scoped', function() use ($app) {
  if (!$app->checkScope('read:messages')){
    header('HTTP/1.0 403 forbidden');
    header('Content-Type: application/json; charset=utf-8');
    echo json_encode(array("message" => "Insufficient scope."));
    exit();
  }
});

// ...

$router->get('/api/private-scoped', function() use ($app){
  header('Content-Type: application/json; charset=utf-8');
  echo json_encode($app->privateScopedEndpoint());
});

The route /api/private-scoped will be accessible only if has a valid Access Token with the scope read:messages.

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