CheckoutVerifier

CheckoutVerifier helps you Verify your In-App Purchase receipts & protect your Apps from hacking, patching used by Piracy Apps like Lucky Patcher.
Since I was using these classes in every project, the copy / pasting of classes was annoying so thought of releasing it as a library which might be of help to others too!

How does it work?

Well, the library sends the Signed Json Response & Signature that you receive after a purchase is completed on a specified server url where it checks the signature of that response data with your BASE64 Key provided to you in your Developer Console.

Set Up

* Get Licensing API Key

Navigate to Developer Console & Select your App.
Go to Development Tools > Services & API.
Copy the BASE64 Licensing Key

* Creating a Verifying PHP File

Just a create a File & name it as verify.php or anything you want.
Paste the following code in it & Upload it to your server.

<?php
    $data = $_GET['jsonResponse'];
    $signature = $_GET['signature'];
    $key_64 = "YOUR BASE64 KEY THAT YOU GOT FROM DEVELOPER CONSOLE, THERE SHOULD BE NO SPACES!";

    $key =  "-----BEGIN PUBLIC KEY-----\n".
            chunk_split($key_64, 64,"\n").
            "-----END PUBLIC KEY-----";

    $key = openssl_get_publickey($key);

    $ok = openssl_verify($data, base64_decode($signature), $key, OPENSSL_ALGO_SHA1);
    if ($ok == 1) {
        echo "verified";
    } elseif ($ok == 0) {
        echo "unverified";
    } else {
        die ("fault, error checking signature");
    }

    openssl_free_key($key);
?>

* Implementing Library (Gradle)

Note: Add mavenCentral() in repositories block.

dependencies {
    // CheckoutVerifier now internally uses Kotlin Coroutines.
    implementation 'com.lazygeniouz:checkout-verifier:$library_version'
}

* CheckoutVerifier

Just pass on the required PurchaseBundle in the Constructor & call authenticate();
The authenticate() returns a Result object.

If the connection to the server was successful & a result was returned,
CompletionResult(isVerified: Boolean) is returned,
ErrorResult(exception: Exception) otherwise.

Example:

yourScope.launch {
    val purchaseBundle = PurchaseBundle(url, jsonResponse, signature)
    when (val result = CheckoutVerifier(purchaseBundle).authenticate()) {
        is CompletionResult -> {
            val verified = result.isVerified
            // Do something
        }
      is ErrorResult -> Log.d(TAG, result.exception.message)
    }
}