605 lines
15 KiB
PHP
605 lines
15 KiB
PHP
<?php
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/**
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* @author Björn Schießle <schiessle@owncloud.com>
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* @author Clark Tomlinson <fallen013@gmail.com>
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* @author Lukas Reschke <lukas@owncloud.com>
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* @author Thomas Müller <thomas.mueller@tmit.eu>
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*
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* @copyright Copyright (c) 2015, ownCloud, Inc.
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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 OCA\Encryption\Crypto;
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use OC\Encryption\Exceptions\DecryptionFailedException;
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use OC\Encryption\Exceptions\EncryptionFailedException;
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use OCA\Encryption\Exceptions\MultiKeyDecryptException;
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use OCA\Encryption\Exceptions\MultiKeyEncryptException;
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use OCA\Encryption\Vendor\PBKDF2Fallback;
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use OCP\Encryption\Exceptions\GenericEncryptionException;
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use OCP\IConfig;
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use OCP\ILogger;
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use OCP\IUser;
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use OCP\IUserSession;
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class Crypt {
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const DEFAULT_CIPHER = 'AES-256-CFB';
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// default cipher from old ownCloud versions
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const LEGACY_CIPHER = 'AES-128-CFB';
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// default key format, old ownCloud version encrypted the private key directly
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// with the user password
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const LEGACY_KEY_FORMAT = 'password';
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const HEADER_START = 'HBEGIN';
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const HEADER_END = 'HEND';
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/**
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* @var ILogger
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*/
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private $logger;
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/**
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* @var string
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*/
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private $user;
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/**
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* @var IConfig
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*/
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private $config;
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/**
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* @var array
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*/
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private $supportedKeyFormats;
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/**
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* @param ILogger $logger
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* @param IUserSession $userSession
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* @param IConfig $config
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*/
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public function __construct(ILogger $logger, IUserSession $userSession, IConfig $config) {
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$this->logger = $logger;
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$this->user = $userSession && $userSession->isLoggedIn() ? $userSession->getUser()->getUID() : '"no user given"';
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$this->config = $config;
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$this->supportedKeyFormats = ['hash', 'password'];
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}
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/**
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* create new private/public key-pair for user
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*
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* @return array|bool
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*/
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public function createKeyPair() {
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$log = $this->logger;
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$res = $this->getOpenSSLPKey();
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if (!$res) {
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$log->error("Encryption Library couldn't generate users key-pair for {$this->user}",
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['app' => 'encryption']);
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if (openssl_error_string()) {
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$log->error('Encryption library openssl_pkey_new() fails: ' . openssl_error_string(),
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['app' => 'encryption']);
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}
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} elseif (openssl_pkey_export($res,
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$privateKey,
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null,
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$this->getOpenSSLConfig())) {
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$keyDetails = openssl_pkey_get_details($res);
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$publicKey = $keyDetails['key'];
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return [
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'publicKey' => $publicKey,
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'privateKey' => $privateKey
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];
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}
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$log->error('Encryption library couldn\'t export users private key, please check your servers OpenSSL configuration.' . $this->user,
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['app' => 'encryption']);
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if (openssl_error_string()) {
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$log->error('Encryption Library:' . openssl_error_string(),
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['app' => 'encryption']);
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}
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return false;
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}
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/**
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* Generates a new private key
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*
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* @return resource
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*/
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public function getOpenSSLPKey() {
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$config = $this->getOpenSSLConfig();
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return openssl_pkey_new($config);
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}
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/**
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* get openSSL Config
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*
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* @return array
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*/
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private function getOpenSSLConfig() {
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$config = ['private_key_bits' => 4096];
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$config = array_merge(
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$config,
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$this->config->getSystemValue('openssl', [])
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);
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return $config;
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}
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/**
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* @param string $plainContent
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* @param string $passPhrase
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* @return bool|string
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* @throws GenericEncryptionException
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*/
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public function symmetricEncryptFileContent($plainContent, $passPhrase) {
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if (!$plainContent) {
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$this->logger->error('Encryption Library, symmetrical encryption failed no content given',
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['app' => 'encryption']);
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return false;
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}
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$iv = $this->generateIv();
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$encryptedContent = $this->encrypt($plainContent,
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$iv,
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$passPhrase,
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$this->getCipher());
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// combine content to encrypt the IV identifier and actual IV
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$catFile = $this->concatIV($encryptedContent, $iv);
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$padded = $this->addPadding($catFile);
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return $padded;
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}
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/**
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* generate header for encrypted file
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*
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* @param string $keyFormat (can be 'hash' or 'password')
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* @return string
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* @throws \InvalidArgumentException
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*/
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public function generateHeader($keyFormat = 'hash') {
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if (in_array($keyFormat, $this->supportedKeyFormats, true) === false) {
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throw new \InvalidArgumentException('key format "' . $keyFormat . '" is not supported');
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}
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$cipher = $this->getCipher();
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$header = self::HEADER_START
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. ':cipher:' . $cipher
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. ':keyFormat:' . $keyFormat
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. ':' . self::HEADER_END;
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return $header;
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}
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/**
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* @param string $plainContent
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* @param string $iv
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* @param string $passPhrase
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* @param string $cipher
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* @return string
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* @throws EncryptionFailedException
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*/
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private function encrypt($plainContent, $iv, $passPhrase = '', $cipher = self::DEFAULT_CIPHER) {
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$encryptedContent = openssl_encrypt($plainContent,
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$cipher,
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$passPhrase,
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false,
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$iv);
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if (!$encryptedContent) {
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$error = 'Encryption (symmetric) of content failed';
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$this->logger->error($error . openssl_error_string(),
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['app' => 'encryption']);
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throw new EncryptionFailedException($error);
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}
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return $encryptedContent;
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}
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/**
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* return Cipher either from config.php or the default cipher defined in
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* this class
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*
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* @return string
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*/
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public function getCipher() {
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$cipher = $this->config->getSystemValue('cipher', self::DEFAULT_CIPHER);
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if ($cipher !== 'AES-256-CFB' && $cipher !== 'AES-128-CFB') {
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$this->logger->warning('Wrong cipher defined in config.php only AES-128-CFB and AES-256-CFB are supported. Fall back' . self::DEFAULT_CIPHER,
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['app' => 'encryption']);
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$cipher = self::DEFAULT_CIPHER;
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}
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return $cipher;
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}
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/**
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* get key size depending on the cipher
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*
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* @param string $cipher supported ('AES-256-CFB' and 'AES-128-CFB')
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* @return int
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* @throws \InvalidArgumentException
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*/
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protected function getKeySize($cipher) {
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if ($cipher === 'AES-256-CFB') {
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return 32;
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} else if ($cipher === 'AES-128-CFB') {
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return 16;
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}
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throw new \InvalidArgumentException(
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'Wrong cipher defined only AES-128-CFB and AES-256-CFB are supported.'
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);
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}
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/**
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* get legacy cipher
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*
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* @return string
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*/
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public function getLegacyCipher() {
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return self::LEGACY_CIPHER;
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}
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/**
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* @param string $encryptedContent
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* @param string $iv
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* @return string
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*/
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private function concatIV($encryptedContent, $iv) {
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return $encryptedContent . '00iv00' . $iv;
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}
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/**
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* @param $data
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* @return string
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*/
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private function addPadding($data) {
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return $data . 'xx';
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}
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/**
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* generate password hash used to encrypt the users private key
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*
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* @param string $password
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* @param string $cipher
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* @param string $uid only used for user keys
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* @return string
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*/
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protected function generatePasswordHash($password, $cipher, $uid = '') {
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$instanceId = $this->config->getSystemValue('instanceid');
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$instanceSecret = $this->config->getSystemValue('secret');
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$salt = hash('sha256', $uid . $instanceId . $instanceSecret, true);
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$keySize = $this->getKeySize($cipher);
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if (function_exists('hash_pbkdf2')) {
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$hash = hash_pbkdf2(
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'sha256',
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$password,
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$salt,
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100000,
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$keySize,
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true
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);
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} else {
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// fallback to 3rdparty lib for PHP <= 5.4.
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// FIXME: Can be removed as soon as support for PHP 5.4 was dropped
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$fallback = new PBKDF2Fallback();
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$hash = $fallback->pbkdf2(
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'sha256',
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$password,
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$salt,
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100000,
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$keySize,
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true
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);
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}
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return $hash;
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}
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/**
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* encrypt private key
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*
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* @param string $privateKey
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* @param string $password
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* @param string $uid for regular users, empty for system keys
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* @return bool|string
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*/
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public function encryptPrivateKey($privateKey, $password, $uid = '') {
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$cipher = $this->getCipher();
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$hash = $this->generatePasswordHash($password, $cipher, $uid);
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$encryptedKey = $this->symmetricEncryptFileContent(
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$privateKey,
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$hash
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);
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return $encryptedKey;
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}
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/**
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* @param string $privateKey
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* @param string $password
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* @param string $uid for regular users, empty for system keys
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* @return bool|string
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*/
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public function decryptPrivateKey($privateKey, $password = '', $uid = '') {
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$header = $this->parseHeader($privateKey);
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if (isset($header['cipher'])) {
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$cipher = $header['cipher'];
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} else {
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$cipher = self::LEGACY_CIPHER;
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}
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if (isset($header['keyFormat'])) {
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$keyFormat = $header['keyFormat'];
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} else {
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$keyFormat = self::LEGACY_KEY_FORMAT;
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}
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if ($keyFormat === 'hash') {
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$password = $this->generatePasswordHash($password, $cipher, $uid);
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}
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// If we found a header we need to remove it from the key we want to decrypt
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if (!empty($header)) {
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$privateKey = substr($privateKey,
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strpos($privateKey,
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self::HEADER_END) + strlen(self::HEADER_END));
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}
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$plainKey = $this->symmetricDecryptFileContent($privateKey,
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$password,
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$cipher);
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if ($this->isValidPrivateKey($plainKey) === false) {
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return false;
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}
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return $plainKey;
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}
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/**
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* check if it is a valid private key
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*
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* @param $plainKey
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* @return bool
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*/
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protected function isValidPrivateKey($plainKey) {
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$res = openssl_get_privatekey($plainKey);
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if (is_resource($res)) {
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$sslInfo = openssl_pkey_get_details($res);
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if (isset($sslInfo['key'])) {
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return true;
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}
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}
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return false;
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}
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/**
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* @param $keyFileContents
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* @param string $passPhrase
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* @param string $cipher
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* @return string
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* @throws DecryptionFailedException
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*/
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public function symmetricDecryptFileContent($keyFileContents, $passPhrase, $cipher = self::DEFAULT_CIPHER) {
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// Remove Padding
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$noPadding = $this->removePadding($keyFileContents);
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$catFile = $this->splitIv($noPadding);
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return $this->decrypt($catFile['encrypted'],
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$catFile['iv'],
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$passPhrase,
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$cipher);
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}
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/**
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* remove padding
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*
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* @param $padded
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* @return bool|string
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*/
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private function removePadding($padded) {
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if (substr($padded, -2) === 'xx') {
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return substr($padded, 0, -2);
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}
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return false;
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}
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/**
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* split iv from encrypted content
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*
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* @param $catFile
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* @return array
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*/
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private function splitIv($catFile) {
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// Fetch encryption metadata from end of file
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$meta = substr($catFile, -22);
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// Fetch IV from end of file
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$iv = substr($meta, -16);
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// Remove IV and IV Identifier text to expose encrypted content
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$encrypted = substr($catFile, 0, -22);
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return [
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'encrypted' => $encrypted,
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'iv' => $iv
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];
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}
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/**
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* @param $encryptedContent
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* @param $iv
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* @param string $passPhrase
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* @param string $cipher
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* @return string
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* @throws DecryptionFailedException
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*/
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private function decrypt($encryptedContent, $iv, $passPhrase = '', $cipher = self::DEFAULT_CIPHER) {
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$plainContent = openssl_decrypt($encryptedContent,
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$cipher,
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$passPhrase,
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false,
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$iv);
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if ($plainContent) {
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return $plainContent;
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} else {
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throw new DecryptionFailedException('Encryption library: Decryption (symmetric) of content failed: ' . openssl_error_string());
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}
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}
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/**
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* @param $data
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* @return array
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*/
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protected function parseHeader($data) {
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$result = [];
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if (substr($data, 0, strlen(self::HEADER_START)) === self::HEADER_START) {
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$endAt = strpos($data, self::HEADER_END);
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$header = substr($data, 0, $endAt + strlen(self::HEADER_END));
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// +1 not to start with an ':' which would result in empty element at the beginning
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$exploded = explode(':',
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substr($header, strlen(self::HEADER_START) + 1));
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$element = array_shift($exploded);
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while ($element != self::HEADER_END) {
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$result[$element] = array_shift($exploded);
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$element = array_shift($exploded);
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}
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}
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return $result;
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}
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/**
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* generate initialization vector
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*
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* @return string
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* @throws GenericEncryptionException
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*/
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private function generateIv() {
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$random = openssl_random_pseudo_bytes(12, $strong);
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if ($random) {
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if (!$strong) {
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// If OpenSSL indicates randomness is insecure log error
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$this->logger->error('Encryption Library: Insecure symmetric key was generated using openssl_random_psudo_bytes()',
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['app' => 'encryption']);
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}
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/*
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* We encode the iv purely for string manipulation
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* purposes -it gets decoded before use
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*/
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return base64_encode($random);
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}
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// If we ever get here we've failed anyway no need for an else
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throw new GenericEncryptionException('Generating IV Failed');
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}
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/**
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* Generate a cryptographically secure pseudo-random base64 encoded 256-bit
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* ASCII key, used as file key
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*
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* @return string
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* @throws \Exception
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*/
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public function generateFileKey() {
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// Generate key
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$key = base64_encode(openssl_random_pseudo_bytes(32, $strong));
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if (!$key || !$strong) {
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// If OpenSSL indicates randomness is insecure, log error
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throw new \Exception('Encryption library, Insecure symmetric key was generated using openssl_random_pseudo_bytes()');
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}
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return $key;
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}
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/**
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* @param $encKeyFile
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* @param $shareKey
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* @param $privateKey
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* @return mixed
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* @throws MultiKeyDecryptException
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*/
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public function multiKeyDecrypt($encKeyFile, $shareKey, $privateKey) {
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if (!$encKeyFile) {
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throw new MultiKeyDecryptException('Cannot multikey decrypt empty plain content');
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}
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if (openssl_open($encKeyFile, $plainContent, $shareKey, $privateKey)) {
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return $plainContent;
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} else {
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throw new MultiKeyDecryptException('multikeydecrypt with share key failed:' . openssl_error_string());
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}
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}
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/**
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* @param string $plainContent
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* @param array $keyFiles
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* @return array
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* @throws MultiKeyEncryptException
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*/
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public function multiKeyEncrypt($plainContent, array $keyFiles) {
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// openssl_seal returns false without errors if plaincontent is empty
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// so trigger our own error
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if (empty($plainContent)) {
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throw new MultiKeyEncryptException('Cannot multikeyencrypt empty plain content');
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}
|
|
|
|
// Set empty vars to be set by openssl by reference
|
|
$sealed = '';
|
|
$shareKeys = [];
|
|
$mappedShareKeys = [];
|
|
|
|
if (openssl_seal($plainContent, $sealed, $shareKeys, $keyFiles)) {
|
|
$i = 0;
|
|
|
|
// Ensure each shareKey is labelled with its corresponding key id
|
|
foreach ($keyFiles as $userId => $publicKey) {
|
|
$mappedShareKeys[$userId] = $shareKeys[$i];
|
|
$i++;
|
|
}
|
|
|
|
return [
|
|
'keys' => $mappedShareKeys,
|
|
'data' => $sealed
|
|
];
|
|
} else {
|
|
throw new MultiKeyEncryptException('multikeyencryption failed ' . openssl_error_string());
|
|
}
|
|
}
|
|
}
|
|
|