<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @since         3.0.0
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */
namespace Cake\Utility\Crypto;

/**
 * OpenSSL implementation of crypto features for Cake\Utility\Security
 *
 * OpenSSL should be favored over mcrypt as it is actively maintained and
 * more widely available.
 *
 * This class is not intended to be used directly and should only
 * be used in the context of Cake\Utility\Security.
 *
 * @internal
 */
class OpenSsl
{

    /**
     * Not implemented
     *
     * @param string $text Encrypted string to decrypt, normal string to encrypt
     * @param string $key Key to use as the encryption key for encrypted data.
     * @param string $operation Operation to perform, encrypt or decrypt
     * @throws \LogicException Rijndael compatibility does not exist with Openssl.
     * @return void
     */
    public static function rijndael($text, $key, $operation)
    {
        throw new \LogicException('rijndael is not compatible with OpenSSL. Use mcrypt instead.');
    }

    /**
     * Encrypt a value using AES-256.
     *
     * *Caveat* You cannot properly encrypt/decrypt data with trailing null bytes.
     * Any trailing null bytes will be removed on decryption due to how PHP pads messages
     * with nulls prior to encryption.
     *
     * @param string $plain The value to encrypt.
     * @param string $key The 256 bit/32 byte key to use as a cipher key.
     * @param string|null $hmacSalt The salt to use for the HMAC process. Leave null to use Security.salt.
     * @return string Encrypted data.
     * @throws \InvalidArgumentException On invalid data or key.
     */
    public static function encrypt($plain, $key, $hmacSalt = null)
    {
        $method = 'AES-256-CBC';
        $ivSize = openssl_cipher_iv_length($method);

        $iv = openssl_random_pseudo_bytes($ivSize);
        return $iv . openssl_encrypt($plain, $method, $key, true, $iv);
    }

    /**
     * Decrypt a value using AES-256.
     *
     * @param string $cipher The ciphertext to decrypt.
     * @param string $key The 256 bit/32 byte key to use as a cipher key.
     * @return string Decrypted data. Any trailing null bytes will be removed.
     * @throws \InvalidArgumentException On invalid data or key.
     */
    public static function decrypt($cipher, $key)
    {
        $method = 'AES-256-CBC';
        $ivSize = openssl_cipher_iv_length($method);

        $iv = mb_substr($cipher, 0, $ivSize, '8bit');

        $cipher = mb_substr($cipher, $ivSize, null, '8bit');
        return openssl_decrypt($cipher, $method, $key, true, $iv);
    }
}
