BaseHandler.php

<?php

declare(strict_types=1);

/**
 * This file is part of CodeIgniter 4 framework.
 *
 * (c) CodeIgniter Foundation <admin@codeigniter.com>
 *
 * For the full copyright and license information, please view
 * the LICENSE file that was distributed with this source code.
 */

namespace CodeIgniter\Encryption\Handlers;

use CodeIgniter\Encryption\EncrypterInterface;
use CodeIgniter\Encryption\Exceptions\EncryptionException;
use Config\Encryption;
use SensitiveParameter;

/**
 * Base class for encryption handling
 */
abstract class BaseHandler implements EncrypterInterface
{
    /**
     * List of previous keys for fallback decryption.
     *
     * @var list<string>
     */
    protected array $previousKeys = [];

    /**
     * Constructor
     */
    public function __construct(?Encryption $config = null)
    {
        $config ??= config(Encryption::class);

        // make the parameters conveniently accessible
        foreach (get_object_vars($config) as $key => $value) {
            if (property_exists($this, $key)) {
                $this->{$key} = $value;
            }
        }
    }

    /**
     * Byte-safe substr()
     *
     * @param string $str
     * @param int    $start
     * @param int    $length
     *
     * @return string
     */
    protected static function substr($str, $start, $length = null)
    {
        return mb_substr($str, $start, $length, '8bit');
    }

    /**
     * Attempts to decrypt using the provided callback, and if it fails,
     * tries again with any previous keys we may have.
     *
     * @param string                                                      $data            Data to decrypt
     * @param array<string, string>|string|null                           $params          Decryption parameters
     * @param callable(string, array<string, string>|string|null): string $decryptCallback Callback that performs decryption
     *
     * @return string Decrypted data
     *
     * @throws EncryptionException
     */
    protected function tryDecryptWithFallback($data, #[SensitiveParameter] array|string|null $params, callable $decryptCallback)
    {
        try {
            return $decryptCallback($data, $params);
        } catch (EncryptionException $e) {
            if ($this->previousKeys === []) {
                throw $e;
            }

            if (is_string($params) || (is_array($params) && isset($params['key']))) {
                throw $e;
            }

            foreach ($this->previousKeys as $previousKey) {
                try {
                    $previousParams = is_array($params)
                        ? array_merge($params, ['key' => $previousKey])
                        : $previousKey;

                    return $decryptCallback($data, $previousParams);
                } catch (EncryptionException) {
                    continue;
                }
            }

            throw $e;
        }
    }

    /**
     * __get() magic, providing readonly access to some of our properties
     *
     * @param string $key Property name
     *
     * @return array|bool|int|string|null
     */
    public function __get($key)
    {
        if ($this->__isset($key)) {
            return $this->{$key};
        }

        return null;
    }

    /**
     * __isset() magic, providing checking for some of our properties
     *
     * @param string $key Property name
     */
    public function __isset($key): bool
    {
        return property_exists($this, $key);
    }
}