582 lines
16 KiB
PHP
582 lines
16 KiB
PHP
<?php
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/**
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* ownCloud
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*
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* @copyright (C) 2014 ownCloud, Inc.
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*
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* @author Bjoern Schiessle <schiessle@owncloud.com>
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* @author Sam Tuke <samtuke@owncloud.com>
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* @author Frank Karlitschek <frank@owncloud.com>
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* @author Robin Appelman <icewind@owncloud.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
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* License as published by the Free Software Foundation; either
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* version 3 of the License, or any later version.
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*
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* This library 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
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* License along with this library. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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namespace OCA\Files_Encryption;
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/**
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* Class for common cryptography functionality
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*/
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class Crypt {
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const ENCRYPTION_UNKNOWN_ERROR = -1;
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const ENCRYPTION_NOT_INITIALIZED_ERROR = 1;
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const ENCRYPTION_PRIVATE_KEY_NOT_VALID_ERROR = 2;
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const ENCRYPTION_NO_SHARE_KEY_FOUND = 3;
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const BLOCKSIZE = 8192; // block size will always be 8192 for a PHP stream https://bugs.php.net/bug.php?id=21641
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const DEFAULT_CIPHER = 'AES-256-CFB';
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const HEADERSTART = 'HBEGIN';
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const HEADEREND = 'HEND';
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/**
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* return encryption mode client or server side encryption
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* @param string $user name (use system wide setting if name=null)
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* @return string 'client' or 'server'
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* @note at the moment we only support server side encryption
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*/
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public static function mode($user = null) {
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return 'server';
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}
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/**
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* Create a new encryption keypair
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* @return array publicKey, privatekey
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*/
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public static function createKeypair() {
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$return = false;
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$res = Helper::getOpenSSLPkey();
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if ($res === false) {
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\OCP\Util::writeLog('Encryption library', 'couldn\'t generate users key-pair for ' . \OCP\User::getUser(), \OCP\Util::ERROR);
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while ($msg = openssl_error_string()) {
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\OCP\Util::writeLog('Encryption library', 'openssl_pkey_new() fails: ' . $msg, \OCP\Util::ERROR);
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}
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} elseif (openssl_pkey_export($res, $privateKey, null, Helper::getOpenSSLConfig())) {
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// Get public key
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$keyDetails = openssl_pkey_get_details($res);
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$publicKey = $keyDetails['key'];
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$return = array(
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'publicKey' => $publicKey,
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'privateKey' => $privateKey
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);
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} else {
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\OCP\Util::writeLog('Encryption library', 'couldn\'t export users private key, please check your servers openSSL configuration.' . \OCP\User::getUser(), \OCP\Util::ERROR);
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while($errMsg = openssl_error_string()) {
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\OCP\Util::writeLog('Encryption library', $errMsg, \OCP\Util::ERROR);
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}
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}
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return $return;
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}
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/**
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* Add arbitrary padding to encrypted data
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* @param string $data data to be padded
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* @return string padded data
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* @note In order to end up with data exactly 8192 bytes long we must
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* add two letters. It is impossible to achieve exactly 8192 length
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* blocks with encryption alone, hence padding is added to achieve the
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* required length.
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*/
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private static function addPadding($data) {
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$padded = $data . 'xx';
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return $padded;
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}
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/**
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* Remove arbitrary padding to encrypted data
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* @param string $padded padded data to remove padding from
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* @return string unpadded data on success, false on error
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*/
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private static function removePadding($padded) {
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if (substr($padded, -2) === 'xx') {
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$data = substr($padded, 0, -2);
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return $data;
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} else {
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// TODO: log the fact that unpadded data was submitted for removal of padding
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return false;
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}
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}
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/**
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* Check if a file's contents contains an IV and is symmetrically encrypted
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* @param string $content
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* @return boolean
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* @note see also \OCA\Files_Encryption\Util->isEncryptedPath()
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*/
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public static function isCatfileContent($content) {
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if (!$content) {
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return false;
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}
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$noPadding = self::removePadding($content);
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// Fetch encryption metadata from end of file
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$meta = substr($noPadding, -22);
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// Fetch IV from end of file
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$iv = substr($meta, -16);
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// Fetch identifier from start of metadata
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$identifier = substr($meta, 0, 6);
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if ($identifier === '00iv00') {
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return true;
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} else {
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return false;
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}
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}
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/**
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* Check if a file is encrypted according to database file cache
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* @param string $path
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* @return bool
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*/
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public static function isEncryptedMeta($path) {
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// TODO: Use DI to get \OC\Files\Filesystem out of here
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// Fetch all file metadata from DB
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$metadata = \OC\Files\Filesystem::getFileInfo($path);
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// Return encryption status
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return isset($metadata['encrypted']) && ( bool )$metadata['encrypted'];
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}
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/**
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* Symmetrically encrypt a string
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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 $cypher used for encryption, currently we support AES-128-CFB and AES-256-CFB
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* @return string encrypted file content
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* @throws \OCA\Files_Encryption\Exception\EncryptionException
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*/
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private static function encrypt($plainContent, $iv, $passphrase = '', $cipher = Crypt::DEFAULT_CIPHER) {
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$encryptedContent = openssl_encrypt($plainContent, $cipher, $passphrase, false, $iv);
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if (!$encryptedContent) {
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$error = "Encryption (symmetric) of content failed: " . openssl_error_string();
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\OCP\Util::writeLog('Encryption library', $error, \OCP\Util::ERROR);
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throw new Exception\EncryptionException($error, Exception\EncryptionException::ENCRYPTION_FAILED);
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}
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return $encryptedContent;
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}
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/**
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* Symmetrically decrypt a string
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* @param string $encryptedContent
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* @param string $iv
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* @param string $passphrase
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* @param string $cipher cipher user for decryption, currently we support aes128 and aes256
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* @throws \Exception
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* @return string decrypted file content
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*/
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private static function decrypt($encryptedContent, $iv, $passphrase, $cipher = Crypt::DEFAULT_CIPHER) {
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$plainContent = openssl_decrypt($encryptedContent, $cipher, $passphrase, false, $iv);
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if ($plainContent) {
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return $plainContent;
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} else {
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throw new \Exception('Encryption library: Decryption (symmetric) of content failed');
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}
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}
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/**
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* Concatenate encrypted data with its IV and padding
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* @param string $content content to be concatenated
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* @param string $iv IV to be concatenated
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* @return string concatenated content
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*/
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private static function concatIv($content, $iv) {
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$combined = $content . '00iv00' . $iv;
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return $combined;
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}
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/**
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* Split concatenated data and IV into respective parts
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* @param string $catFile concatenated data to be split
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* @return array keys: encrypted, iv
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*/
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private static function splitIv($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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$split = array(
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'encrypted' => $encrypted,
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'iv' => $iv
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);
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return $split;
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}
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/**
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* Symmetrically encrypts a string and returns keyfile content
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* @param string $plainContent content to be encrypted in keyfile
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* @param string $passphrase
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* @param string $cypher used for encryption, currently we support AES-128-CFB and AES-256-CFB
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* @return false|string encrypted content combined with IV
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* @note IV need not be specified, as it will be stored in the returned keyfile
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* and remain accessible therein.
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*/
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public static function symmetricEncryptFileContent($plainContent, $passphrase = '', $cipher = Crypt::DEFAULT_CIPHER) {
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if (!$plainContent) {
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\OCP\Util::writeLog('Encryption library', 'symmetrically encryption failed, no content given.', \OCP\Util::ERROR);
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return false;
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}
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$iv = self::generateIv();
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try {
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$encryptedContent = self::encrypt($plainContent, $iv, $passphrase, $cipher);
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// Combine content to encrypt with IV identifier and actual IV
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$catfile = self::concatIv($encryptedContent, $iv);
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$padded = self::addPadding($catfile);
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return $padded;
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} catch (Exception\EncryptionException $e) {
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$message = 'Could not encrypt file content (code: ' . $e->getCode() . '): ';
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\OCP\Util::writeLog('files_encryption', $message . $e->getMessage(), \OCP\Util::ERROR);
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return false;
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}
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}
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/**
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* Symmetrically decrypts keyfile content
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* @param string $keyfileContent
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* @param string $passphrase
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* @param string $cipher cipher used for decryption, currently aes128 and aes256 is supported.
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* @throws \Exception
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* @return string|false
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* @internal param string $source
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* @internal param string $target
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* @internal param string $key the decryption key
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* @return string decrypted content
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*
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* This function decrypts a file
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*/
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public static function symmetricDecryptFileContent($keyfileContent, $passphrase = '', $cipher = Crypt::DEFAULT_CIPHER) {
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if (!$keyfileContent) {
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throw new \Exception('Encryption library: no data provided for decryption');
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}
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// Remove padding
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$noPadding = self::removePadding($keyfileContent);
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// Split into enc data and catfile
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$catfile = self::splitIv($noPadding);
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if ($plainContent = self::decrypt($catfile['encrypted'], $catfile['iv'], $passphrase, $cipher)) {
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return $plainContent;
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} else {
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return false;
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}
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}
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/**
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* Decrypt private key and check if the result is a valid keyfile
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*
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* @param string $encryptedKey encrypted keyfile
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* @param string $passphrase to decrypt keyfile
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* @return string|false encrypted private key or false
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*
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* This function decrypts a file
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*/
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public static function decryptPrivateKey($encryptedKey, $passphrase) {
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$header = self::parseHeader($encryptedKey);
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$cipher = self::getCipher($header);
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// if we found a header we need to remove it from the key we want to decrypt
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if (!empty($header)) {
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$encryptedKey = substr($encryptedKey, strpos($encryptedKey, self::HEADEREND) + strlen(self::HEADEREND));
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}
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$plainKey = self::symmetricDecryptFileContent($encryptedKey, $passphrase, $cipher);
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// check if this a valid private key
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$res = openssl_pkey_get_private($plainKey);
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if (is_resource($res)) {
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$sslInfo = openssl_pkey_get_details($res);
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if (!isset($sslInfo['key'])) {
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$plainKey = false;
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}
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} else {
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$plainKey = false;
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}
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return $plainKey;
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}
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/**
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* Create asymmetrically encrypted keyfile content using a generated key
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* @param string $plainContent content to be encrypted
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* @param array $publicKeys array keys must be the userId of corresponding user
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* @return array keys: keys (array, key = userId), data
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* @throws \OCA\Files_Encryption\Exception\MultiKeyEncryptException if encryption failed
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* @note symmetricDecryptFileContent() can decrypt files created using this method
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*/
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public static function multiKeyEncrypt($plainContent, array $publicKeys) {
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// openssl_seal returns false without errors if $plainContent
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// is empty, so trigger our own error
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if (empty($plainContent)) {
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throw new Exception\MultiKeyEncryptException('Cannot multiKeyEncrypt empty plain content', Exception\MultiKeyEncryptException::EMPTY_DATA);
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}
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// Set empty vars to be set by openssl by reference
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$sealed = '';
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$shareKeys = array();
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$mappedShareKeys = array();
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if (openssl_seal($plainContent, $sealed, $shareKeys, $publicKeys)) {
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$i = 0;
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// Ensure each shareKey is labelled with its
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// corresponding userId
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foreach ($publicKeys as $userId => $publicKey) {
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$mappedShareKeys[$userId] = $shareKeys[$i];
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$i++;
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}
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return array(
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'keys' => $mappedShareKeys,
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'data' => $sealed
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);
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} else {
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throw new Exception\MultiKeyEncryptException('multi key encryption failed: ' . openssl_error_string(),
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Exception\MultiKeyEncryptException::OPENSSL_SEAL_FAILED);
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}
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}
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/**
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* Asymmetrically encrypt a file using multiple public keys
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* @param string $encryptedContent
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* @param string $shareKey
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* @param mixed $privateKey
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* @throws \OCA\Files_Encryption\Exception\MultiKeyDecryptException if decryption failed
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* @internal param string $plainContent contains decrypted content
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* @return string $plainContent decrypted string
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* @note symmetricDecryptFileContent() can be used to decrypt files created using this method
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*
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* This function decrypts a file
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*/
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public static function multiKeyDecrypt($encryptedContent, $shareKey, $privateKey) {
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if (!$encryptedContent) {
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throw new Exception\MultiKeyDecryptException('Cannot mutliKeyDecrypt empty plain content',
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Exception\MultiKeyDecryptException::EMPTY_DATA);
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}
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if (openssl_open($encryptedContent, $plainContent, $shareKey, $privateKey)) {
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return $plainContent;
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} else {
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throw new Exception\MultiKeyDecryptException('multiKeyDecrypt with share-key' . $shareKey . 'failed: ' . openssl_error_string(),
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Exception\MultiKeyDecryptException::OPENSSL_OPEN_FAILED);
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}
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}
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/**
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* Generates a pseudo random initialisation vector
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* @return String $iv generated IV
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*/
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private static function generateIv() {
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if ($random = openssl_random_pseudo_bytes(12, $strong)) {
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if (!$strong) {
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// If OpenSSL indicates randomness is insecure, log error
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\OCP\Util::writeLog('Encryption library', 'Insecure symmetric key was generated using openssl_random_pseudo_bytes()', \OCP\Util::WARN);
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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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$iv = base64_encode($random);
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return $iv;
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} else {
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throw new \Exception('Generating IV failed');
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}
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}
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/**
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* Generate a pseudo random 256-bit ASCII key, used as file key
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* @return string|false Generated key
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*/
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public static function generateKey() {
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// Generate key
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if ($key = base64_encode(openssl_random_pseudo_bytes(32, $strong))) {
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if (!$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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} else {
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return false;
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}
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}
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/**
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* read header into array
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*
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* @param string $data
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* @return array
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*/
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public static function parseHeader($data) {
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$result = array();
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if (substr($data, 0, strlen(self::HEADERSTART)) === self::HEADERSTART) {
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$endAt = strpos($data, self::HEADEREND);
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$header = substr($data, 0, $endAt + strlen(self::HEADEREND));
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// +1 to not start with an ':' which would result in empty element at the beginning
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$exploded = explode(':', substr($header, strlen(self::HEADERSTART)+1));
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$element = array_shift($exploded);
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while ($element !== self::HEADEREND) {
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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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* check if data block is the header
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*
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* @param string $data
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* @return boolean
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*/
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public static function isHeader($data) {
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if (substr($data, 0, strlen(self::HEADERSTART)) === self::HEADERSTART) {
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return true;
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}
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return false;
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}
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/**
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* get chiper from header
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*
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* @param array $header
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* @throws \OCA\Files_Encryption\Exception\EncryptionException
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*/
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public static function getCipher($header) {
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$cipher = isset($header['cipher']) ? $header['cipher'] : 'AES-128-CFB';
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if ($cipher !== 'AES-256-CFB' && $cipher !== 'AES-128-CFB') {
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throw new Exception\EncryptionException('file header broken, no supported cipher defined',
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Exception\EncryptionException::UNKNOWN_CIPHER);
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}
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return $cipher;
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}
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/**
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* generate header for encrypted file
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*/
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public static function generateHeader() {
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$cipher = Helper::getCipher();
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$header = self::HEADERSTART . ':cipher:' . $cipher . ':' . self::HEADEREND;
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return $header;
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}
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}
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