116 lines
3.3 KiB
PHP
116 lines
3.3 KiB
PHP
<?php
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/**
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* Copyright (c) 2014 Lukas Reschke <lukas@owncloud.com>
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* This file is licensed under the Affero General Public License version 3 or
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* later.
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* See the COPYING-README file.
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*/
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namespace OC\Security;
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use Crypt_AES;
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use Crypt_Hash;
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use OCP\Security\ICrypto;
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use OCP\Security\ISecureRandom;
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use OCP\Security\StringUtils;
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use OCP\IConfig;
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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 Crypt_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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function __construct(IConfig $config, ISecureRandom $random) {
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$this->cipher = new Crypt_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 $password Password to use (defaults to `secret` in config.php)
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* @return string Calculated HMAC
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*/
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public function calculateHMAC($message, $password = '') {
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if($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 Crypt_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 $password Password to encrypt, if not specified the secret from config.php will be taken
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* @return string Authenticated ciphertext
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*/
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public function encrypt($plaintext, $password = '') {
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if($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 = $this->random->getLowStrengthGenerator()->generate($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 $password Password to encrypt, if not specified the secret from config.php will be taken
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* @return string plaintext
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* @throws \Exception If the HMAC does not match
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*/
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public function decrypt($authenticatedCiphertext, $password = '') {
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if($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('|', $authenticatedCiphertext);
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if(sizeof($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($iv);
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if(!StringUtils::equals($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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return $this->cipher->decrypt($ciphertext);
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}
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}
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