Category: Web

Web development is the work involved in developing a website for the Internet (World Wide Web) or an intranet (a private network).^[1] Web development can range from developing a simple single static page of plain text to complex web applications, electronic businesses, and social network services. A more comprehensive list of tasks to which Web development commonly refers, may include Web engineering, Web design, Web content development, client liaison, client-side/server-side scripting, Web server and network security configuration, and e-commerce development.

App Store Server Notifications V2 with JWT, PHP and Laravel

App Store Server Notifications

App Store Server Notifications is a server-to-server service that notifies you in real-time when the status of in-app purchases and refunds changes. Use the data in the notifications to update your user-account database, and to monitor and respond to in-app purchase refunds.

App offering subscription based products must use App Store Server Notification to verify the purchase, renew the subscription, cancel the subscription, and more.

App Store Server Notification Version 1 vs Version 2

There are two types of App Store Server Notification, version 1 and version 2. Version 1 is already deprecated and is more likely to be discontinued in the near future.

This article only covers Version 2.

My Intentions

My main goal is to get originalTransactionId from the notification data then when a subscription gets Expired or Refunded, it will downgrade the user subscription status.

App Store Configuration

User purchases we verify Apple’s receipt and we save originalTransactionId in our database. So each user has originalTransactionId and we can find the user with this originalTransactionId. You can read more about this here Auto-renewable subscriptions with SwiftUI

Make sure you set your app store notification URL on the AppStoreConnect. Choose Version 2 Notifications.

Each data will look like this, call it signedPayload.

The signedPayload object is a JWS representation. To get the transaction and subscription renewal details from the notification payload, process the signedPayload as follows:

Parse signedPayload to identify the JWS header, payload, and signature representations.
Base64 URL-decode the payload to get the responseBodyV2DecodedPayload. The decoded payload contains the notificationType , subtype, other notification metadata, and a data object.
The data object contains a signedTransactionInfo (JWSTransaction) and depending on the notification type, a signedRenewalInfo (JWSRenewalInfo). Parse and Base64 URL-decode these signed JWS representations to get transaction and subscription renewal details.

Each of the signed JWS representations, signedPayload, signedTransactionInfo, and signedRenewalInfo, have a JWS signature that you can validate on your server. Use the algorithm specified in the header’s alg parameter to validate the signature. For more information about validating signatures, see the JSON Web Signature (JWS) IETF RFC 7515 specification.

Hopefully, you are already getting this data. Now let’s get originalTransactionId from this. We will do this without any 3rd party library first to understand the process.

First thing, I will download the Apple root certificate and make it.PEM file from it.

Download the certificate https://www.apple.com/certificateauthority/AppleRootCA-G3.cer

Get .PEM file from it, on your Mac Terminal

openssl x509 -in AppleRootCA-G3.cer -out apple_root.pem

For testing purposes, I’m loading apple_root.pem and my signedPayload from a file called notification.json (replace it with file_get_contents(‘php://input’);) and then decoding the signedPayload. signedPayload has three parts, separated by .(dot), line 13.

The first part is the header, the Second part is the body (payload) and the Third part is the signature. The header has an algorithm and x5c, x5c has three elements. Certificate, intermediate certificate, and root certificate. We can verify the certificate in two steps. Once the verification is completed we know we have signedPayload from Apple.

Finally, decode the payload again and get the originalTransactionId from line 56 to 65.

Server Side

For this article, our production server URL looks like inafiz.com/jwt.php. You can get whatever Apple sends you and write a log in your server if you are interested.

$appleData = file_get_contents('php://input');
$file = fopen(
    "/var/www/html/appstore_prod.log", "a"
);
fwrite($file, $appleData);
fclose($file);

Without any 3rd party library(not recommended).

<?php

ini_set('display_errors', 1);
error_reporting(E_ALL);

// Download the certificate -> https://www.apple.com/certificateauthority/AppleRootCA-G3.cer
// Convert it to .PEM file, run on macOS terminal ->  ```bash openssl x509 -in AppleRootCA-G3.cer -out apple_root.pem```

$pem = file_get_contents('apple_root.pem');
$data = file_get_contents('notification.json'); // replace with file_get_contents('php://input');
$json = json_decode($data);

$header_payload_secret = explode('.', $json->signedPayload);

//------------------------------------------
// Header
//------------------------------------------
$header = json_decode(base64_decode($header_payload_secret[0]));
$algorithm = $header->alg;
$x5c = $header->x5c; // array
$certificate = $x5c[0];
$intermediate_certificate = $x5c[1];
$root_certificate = $x5c[2];

$certificate =
      "-----BEGIN CERTIFICATE-----\n"
    . $certificate
    . "\n-----END CERTIFICATE-----";

$intermediate_certificate =
      "-----BEGIN CERTIFICATE-----\n"
    . $intermediate_certificate
    . "\n-----END CERTIFICATE-----";

$root_certificate =
      "-----BEGIN CERTIFICATE-----\n"
    . $root_certificate
    . "\n-----END CERTIFICATE-----";

//------------------------------------------
// Verify the notification request   
//------------------------------------------
if (openssl_x509_verify($intermediate_certificate, $root_certificate) != 1){ 
    echo 'Intermediate and Root certificate do not match';
    exit;
}

// Verify again with Apple root certificate
if (openssl_x509_verify($root_certificate, $pem) == 1){
    //------------------------------------------
    // Payload
    //------------------------------------------
    // https://developer.apple.com/documentation/appstoreservernotifications/notificationtype
    // https://developer.apple.com/documentation/appstoreservernotifications/subtype
    $payload = json_decode(base64_decode($header_payload_secret[1]));
    $notificationType = $payload->notificationType;
    $subtype = $payload->subtype;

    if ($notificationType == "EXPIRED" || $notificationType == "REFUND") {
        $transactionInfo = $payload->data->signedTransactionInfo;
        $ti = explode('.', $transactionInfo);
        
        $data = json_decode(base64_decode($ti[1]));
        var_dump($data); // this will contain our originalTransactionId
    }
} else {
    echo 'Header is not valid';
    exit;
}

Using firebase/php-jwt in composer (recommended), big difference is to use the public key to decode the payload using JWT.

composer require firebase/php-jwt

<?php

ini_set('display_errors', 1);
error_reporting(E_ALL);

// No need these 3 lines for Laravel
require_once './vendor/firebase/php-jwt/src/JWT.php';
require_once './vendor/firebase/php-jwt/src/JWK.php';
require_once './vendor/firebase/php-jwt/src/Key.php';

use Firebase\JWT\JWT;
use Firebase\JWT\Key;

// Download the certificate -> https://www.apple.com/certificateauthority/AppleRootCA-G3.cer
// Convert it to .PEM file, run on macOS terminal ->  ```bash openssl x509 -in AppleRootCA-G3.cer -out apple_root.pem```

$pem = file_get_contents('apple_root.pem');

$data = file_get_contents('notification.json');  // replace with file_get_contents('php://input');
$json = json_decode($data);

$header_payload_secret = explode('.', $json->signedPayload);

//------------------------------------------
// Header
//------------------------------------------
$header = json_decode(base64_decode($header_payload_secret[0]));
$algorithm = $header->alg;
$x5c = $header->x5c; // array
$certificate = $x5c[0];
$intermediate_certificate = $x5c[1];
$root_certificate = $x5c[2];

$certificate =
      "-----BEGIN CERTIFICATE-----\n"
    . $certificate
    . "\n-----END CERTIFICATE-----";

$intermediate_certificate =
      "-----BEGIN CERTIFICATE-----\n"
    . $intermediate_certificate
    . "\n-----END CERTIFICATE-----";

$root_certificate =
      "-----BEGIN CERTIFICATE-----\n"
    . $root_certificate
    . "\n-----END CERTIFICATE-----";

//------------------------------------------
// Verify the notification request   
//------------------------------------------

if (openssl_x509_verify($intermediate_certificate, $root_certificate) != 1){ 
    echo 'Intermediate and Root certificate do not match';
    exit;
}

// Verify again with Apple root certificate
if (openssl_x509_verify($root_certificate, $pem) == 1){
    $cert_object = openssl_x509_read($certificate);
    $pkey_object = openssl_pkey_get_public($cert_object);
    $pkey_array = openssl_pkey_get_details($pkey_object);
    $publicKey = $pkey_array['key'];

    //------------------------------------------
    // Payload
    //------------------------------------------
    $payload = json_decode(base64_decode($header_payload_secret[1]));
    $notificationType = $payload->notificationType;

    //if ($notificationType == "EXPIRED" || $notificationType == "REFUND") {
        $transactionInfo = $payload->data->signedTransactionInfo;
        $signedRenewalInfo = $payload->data->signedRenewalInfo;

        $transactionDecodedData = JWT::decode($transactionInfo, new Key($publicKey, $algorithm));
        var_dump($transactionDecodedData->originalTransactionId);
        echo "========================================";
        $signedRenewalDecodedData = JWT::decode($signedRenewalInfo, new Key($publicKey, $algorithm));
        var_dump($signedRenewalDecodedData);
    //}

} else {
    echo 'Header is not valid';
    exit;
}

Download the source code

Conclusion

In this article we have learned how to configure and implement App Store Server Notification version 2 in PHP and Laravel.

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August 21, 2022

Java Factory Design Pattern
Java Factory Design Pattern

The factory design pattern is a common design pattern used in software development, particularly in object-oriented programming languages like Java. The factory design pattern is a creational design pattern, which means that it deals with object creation.

The factory design pattern is a way to provide a common interface for creating objects without specifying the exact class of object that will be created. This allows the code that uses the objects to be independent of the specific implementation of the objects.

Here is an example of how the factory design pattern might be implemented in Java:
```
public interface Shape {
  void draw();
}

public class Circle implements Shape {
  @Override
  public void draw() {
    // code to draw a circle
  }
}

public class Rectangle implements Shape {
  @Override
  public void draw() {
    // code to draw a rectangle
  }
}

public class ShapeFactory {
  public static Shape getShape(String shapeType) {
    if (shapeType == null) {
      return null;
    }
    if (shapeType.equalsIgnoreCase("CIRCLE")) {
      return new Circle();
    } else if (shapeType.equalsIgnoreCase("RECTANGLE")) {
      return new Rectangle();
    }
    return null;
  }
}
```
In the example above, the ShapeFactory class provides a static method called getShape() that takes a shapeType as an input and returns an object of the specified Shape type. This allows the code that uses the ShapeFactory to create Shape objects without knowing the exact implementation of the objects.

The factory design pattern is a useful pattern to use in Java because it promotes loose coupling and code reuse. It allows you to create objects without specifying their exact class, which makes your code more flexible and easier to maintain.

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March 23, 2022

Laravel Sanctum Tutorial Step by Step

Laravel Sanctum provides a featherweight authentication system for single-page applications, mobile applications, and simple, token-based APIs. Sanctum allows each user of your application to generate multiple API tokens for their account. These tokens may be granted abilities/scopes which specify which actions the tokens are allowed to perform.

Installation

composer require laravel/sanctum and composer update

Next, you should publish the Sanctum configuration and migration files using the vendor:publish Artisan command.

php artisan vendor:publish --provider="Laravel\Sanctum\SanctumServiceProvider"

php artisan migrate

You can also use following sql for creating table, if there is a problem to run migrate command.

CREATE TABLE `personal_access_tokens` (
   `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
   `tokenable_type` varchar(255) NOT NULL,
   `tokenable_id` bigint(20) unsigned NOT NULL,
   `name` varchar(255) NOT NULL,
   `token` varchar(64) NOT NULL,
   `abilities` text DEFAULT NULL,
   `last_used_at` timestamp NULL DEFAULT NULL,
   `created_at` timestamp NULL DEFAULT NULL,
   `updated_at` timestamp NULL DEFAULT NULL,
   PRIMARY KEY (`id`),
   UNIQUE KEY `personal_access_tokens_token_unique` (`token`),
   KEY `personal_access_tokens_tokenable_type_tokenable_id_index` (`tokenable_type`,`tokenable_id`)
 ) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8

Next, if you plan to utilize Sanctum to authenticate an SPA, you should add Sanctum’s middleware to your api middleware group within your application’s app/Http/Kernel.php file:

'api' => [
            'throttle:60,1',
            'bindings',
            \Laravel\Sanctum\Http\Middleware\EnsureFrontendRequestsAreStateful::class,
        ],

Download source code