Salesloft Payload decryption in PHP

gistfile1.txt

<?php

namespace Modules\Integrations\Salesloft\Services;

use Jose\Component\Core\AlgorithmManager;
use Jose\Component\Encryption\Algorithm\KeyEncryption\A256GCMKW;
use Jose\Component\Encryption\Algorithm\ContentEncryption\A256GCM;
use Jose\Component\Encryption\Compression\CompressionMethodManager;
use Jose\Component\Encryption\Compression\Deflate;
use Jose\Component\Encryption\JWEDecrypter;

use Jose\Component\Core\Converter\StandardConverter;
use Jose\Component\Core\JWK;
use Jose\Component\Encryption\Serializer\JWESerializerManager;
use Jose\Component\Encryption\Serializer\CompactSerializer;
use Base64Url\Base64Url;
use Exception;
use Log;


/**
 * Class SalesloftPayloadEncryptionService
 * @package Integrations\Salesloft\Services
 */
class SalesloftPayloadService {

    public function decrypt($secret, $payload) {
        try {
            $jweDecrypter = $this->getDecrypter();
            $jwk = $this->getJwk($secret);
            $jwe = $this->getJwe($payload);
            $jweDecrypter->decryptUsingKey($jwe, $jwk, 0);

            $decryptedPayload = json_decode($jwe->getPayload());
            return $decryptedPayload;
        } catch(Exception $e) {
            Log::info(config('salesloft.name').$e->getMessage());
            return null;
        }
    }

    private function getDecrypter() {
        $keyEncryptionAlgorithmManager = AlgorithmManager::create([
            new A256GCMKW()
        ]);

        $contentEncryptionAlgorithmManager = AlgorithmManager::create([
            new A256GCM()
        ]);

        $compressionMethodManager = CompressionMethodManager::create([
            new Deflate(),
        ]);

        return new JWEDecrypter(
            $keyEncryptionAlgorithmManager,
            $contentEncryptionAlgorithmManager,
            $compressionMethodManager
        );
    }

    private function getJwk($secret) {
        $key = Base64Url::encode(hash('sha256', $secret, true));

        return JWK::create([
            'kty' => 'oct',
            'k' => $key,
        ]);
    }

    private function getJwe($payload) {
        $jsonConverter = new StandardConverter();

        // The serializer manager. We only use the JWE Compact Serialization Mode.
        $serializerManager = JWESerializerManager::create([
            new CompactSerializer($jsonConverter),
        ]);

        // We try to load the token.
        return $serializerManager->unserialize($payload);
    }


}