PocketMine-MP/src/network/mcpe/encryption/EncryptionContext.php

97 lines
2.9 KiB
PHP

<?php
/*
*
* ____ _ _ __ __ _ __ __ ____
* | _ \ ___ ___| | _____| |_| \/ (_)_ __ ___ | \/ | _ \
* | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
* | __/ (_) | (__| < __/ |_| | | | | | | | __/_____| | | | __/
* |_| \___/ \___|_|\_\___|\__|_| |_|_|_| |_|\___| |_| |_|_|
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* @author PocketMine Team
* @link http://www.pocketmine.net/
*
*
*/
declare(strict_types=1);
namespace pocketmine\network\mcpe\encryption;
use Crypto\Cipher;
use pocketmine\utils\Binary;
use function bin2hex;
use function openssl_digest;
use function openssl_error_string;
use function strlen;
use function substr;
class EncryptionContext{
private const ENCRYPTION_SCHEME = "AES-256-CFB8";
private const CHECKSUM_ALGO = "sha256";
/** @var bool */
public static $ENABLED = true;
/** @var string */
private $key;
/** @var Cipher */
private $decryptCipher;
/** @var int */
private $decryptCounter = 0;
/** @var Cipher */
private $encryptCipher;
/** @var int */
private $encryptCounter = 0;
public function __construct(string $encryptionKey){
//TODO: ext/crypto doesn't offer us a way to disable padding. This doesn't matter at the moment because we're
//using CFB8, but this might change in the future. This is supposed to be CFB8 no-padding.
$this->key = $encryptionKey;
$iv = substr($this->key, 0, 16);
$this->decryptCipher = new Cipher(self::ENCRYPTION_SCHEME);
$this->decryptCipher->decryptInit($this->key, $iv);
$this->encryptCipher = new Cipher(self::ENCRYPTION_SCHEME);
$this->encryptCipher->encryptInit($this->key, $iv);
}
/**
* @throws DecryptionException
*/
public function decrypt(string $encrypted) : string{
if(strlen($encrypted) < 9){
throw new DecryptionException("Payload is too short");
}
$decrypted = $this->decryptCipher->decryptUpdate($encrypted);
$payload = substr($decrypted, 0, -8);
if(($expected = $this->calculateChecksum($this->decryptCounter++, $payload)) !== ($actual = substr($decrypted, -8))){
throw new DecryptionException("Encrypted payload has invalid checksum (expected " . bin2hex($expected) . ", got " . bin2hex($actual) . ")");
}
return $payload;
}
public function encrypt(string $payload) : string{
return $this->encryptCipher->encryptUpdate($payload . $this->calculateChecksum($this->encryptCounter++, $payload));
}
private function calculateChecksum(int $counter, string $payload) : string{
$hash = openssl_digest(Binary::writeLLong($counter) . $payload . $this->key, self::CHECKSUM_ALGO, true);
if($hash === false){
throw new \RuntimeException("Encryption error: " . openssl_error_string());
}
return substr($hash, 0, 8);
}
}