143 lines
4.3 KiB
PHP
143 lines
4.3 KiB
PHP
<?php
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declare(strict_types=1);
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/**
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* @copyright Copyright (c) 2016, ownCloud, Inc.
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*
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* @author Andreas Fischer <bantu@owncloud.com>
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* @author Lukas Reschke <lukas@statuscode.ch>
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* @author Morris Jobke <hey@morrisjobke.de>
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* @author Roeland Jago Douma <roeland@famdouma.nl>
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*
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* @license AGPL-3.0
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*
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* This code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License, version 3,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License, version 3,
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* along with this program. If not, see <http://www.gnu.org/licenses/>
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*
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*/
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namespace OC\Security;
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use OCP\IConfig;
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use OCP\Security\ICrypto;
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use OCP\Security\ISecureRandom;
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use phpseclib\Crypt\AES;
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use phpseclib\Crypt\Hash;
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/**
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* Class Crypto provides a high-level encryption layer using AES-CBC. If no key has been provided
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* it will use the secret defined in config.php as key. Additionally the message will be HMAC'd.
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*
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* Usage:
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* $encryptWithDefaultPassword = \OC::$server->getCrypto()->encrypt('EncryptedText');
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* $encryptWithCustompassword = \OC::$server->getCrypto()->encrypt('EncryptedText', 'password');
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*
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* @package OC\Security
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*/
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class Crypto implements ICrypto {
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/** @var AES $cipher */
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private $cipher;
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/** @var int */
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private $ivLength = 16;
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/** @var IConfig */
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private $config;
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/** @var ISecureRandom */
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private $random;
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/**
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* @param IConfig $config
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* @param ISecureRandom $random
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*/
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public function __construct(IConfig $config, ISecureRandom $random) {
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$this->cipher = new AES();
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$this->config = $config;
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$this->random = $random;
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}
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/**
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* @param string $message The message to authenticate
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* @param string $password Password to use (defaults to `secret` in config.php)
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* @return string Calculated HMAC
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*/
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public function calculateHMAC(string $message, string $password = ''): string {
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if($password === '') {
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$password = $this->config->getSystemValue('secret');
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}
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// Append an "a" behind the password and hash it to prevent reusing the same password as for encryption
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$password = hash('sha512', $password . 'a');
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$hash = new Hash('sha512');
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$hash->setKey($password);
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return $hash->hash($message);
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}
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/**
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* Encrypts a value and adds an HMAC (Encrypt-Then-MAC)
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* @param string $plaintext
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* @param string $password Password to encrypt, if not specified the secret from config.php will be taken
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* @return string Authenticated ciphertext
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*/
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public function encrypt(string $plaintext, string $password = ''): string {
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if($password === '') {
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$password = $this->config->getSystemValue('secret');
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}
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$this->cipher->setPassword($password);
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$iv = $this->random->generate($this->ivLength);
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$this->cipher->setIV($iv);
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$ciphertext = bin2hex($this->cipher->encrypt($plaintext));
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$hmac = bin2hex($this->calculateHMAC($ciphertext.$iv, $password));
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return $ciphertext.'|'.$iv.'|'.$hmac;
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}
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/**
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* Decrypts a value and verifies the HMAC (Encrypt-Then-Mac)
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* @param string $authenticatedCiphertext
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* @param string $password Password to encrypt, if not specified the secret from config.php will be taken
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* @return string plaintext
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* @throws \Exception If the HMAC does not match
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* @throws \Exception If the decryption failed
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*/
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public function decrypt(string $authenticatedCiphertext, string $password = ''): string {
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if ($password === '') {
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$password = $this->config->getSystemValue('secret');
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}
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$this->cipher->setPassword($password);
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$parts = explode('|', $authenticatedCiphertext);
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if (\count($parts) !== 3) {
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throw new \Exception('Authenticated ciphertext could not be decoded.');
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}
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$ciphertext = hex2bin($parts[0]);
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$iv = $parts[1];
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$hmac = hex2bin($parts[2]);
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$this->cipher->setIV($iv);
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if (!hash_equals($this->calculateHMAC($parts[0] . $parts[1], $password), $hmac)) {
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throw new \Exception('HMAC does not match.');
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}
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$result = $this->cipher->decrypt($ciphertext);
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if ($result === false) {
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throw new \Exception('Decryption failed');
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}
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return $result;
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}
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}
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