<?php
/************************************************************************
 * This file is part of EspoCRM.
 *
 * EspoCRM - Open Source CRM application.
 * Copyright (C) 2014-2021 Yurii Kuznietsov, Taras Machyshyn, Oleksii Avramenko
 * Website: https://www.espocrm.com
 *
 * EspoCRM is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * EspoCRM is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with EspoCRM. If not, see http://www.gnu.org/licenses/.
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU General Public License version 3.
 *
 * In accordance with Section 7(b) of the GNU General Public License version 3,
 * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
 ************************************************************************/

namespace Espo\Core\Utils;

use RuntimeException;

class Crypt
{
    private $key = null;

    private $cryptKey = null;

    private $iv = null;

    public function __construct(Config $config)
    {
        $this->cryptKey = $config->get('cryptKey', '');
    }

    private function getKey(): string
    {
        if ($this->key === null) {
            $this->key = hash('sha256', $this->cryptKey, true);
        }

        if (!$this->key) {
            throw new RuntimeException("Could not hash key.");
        }

        return $this->key;
    }

    private function getIv(): string
    {
        if ($this->iv === null) {
            if (extension_loaded('openssl')) {
                $this->iv = openssl_random_pseudo_bytes(16);
            }
            else {
                $this->iv = mcrypt_create_iv(16, MCRYPT_RAND);
            }
        }

        return $this->iv;
    }

    public function encrypt(string $string): string
    {
        $iv = $this->getIv();

        if (extension_loaded('openssl')) {
            return base64_encode(
                openssl_encrypt($string, 'aes-256-cbc', $this->getKey(), OPENSSL_RAW_DATA , $iv) . $iv
            );
        }

        $block = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, 'cbc');

        $pad = $block - (strlen($string) % $block);

        $string .= str_repeat(chr($pad), $pad);

        return base64_encode(
            mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $this->getKey(), $string, MCRYPT_MODE_CBC, $iv) . $iv
        );
    }

    public function decrypt(string $encryptedString): string
    {
        $encryptedStringDecoded = base64_decode($encryptedString);

        $string = substr($encryptedStringDecoded, 0, strlen($encryptedStringDecoded) - 16);

        $iv = substr($encryptedStringDecoded, -16);

        if (extension_loaded('openssl')) {
            return trim(
                openssl_decrypt($string, 'aes-256-cbc', $this->getKey(), OPENSSL_RAW_DATA, $iv)
            );
        }

        $string = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $this->getKey(), $string, MCRYPT_MODE_CBC, $iv);

        $len = strlen($string);

        $pad = ord($string[$len - 1]);

        return substr($string, 0, strlen($string) - $pad);
    }

    public function generateKey(): string
    {
        return Util::generateSecretKey();
    }
}