575 lines
14 KiB
PHP
Executable file
575 lines
14 KiB
PHP
Executable file
<?php
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/**
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* ownCloud
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*
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* @author Sam Tuke, Frank Karlitschek, Robin Appelman
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* @copyright 2012 Sam Tuke samtuke@owncloud.com,
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* Robin Appelman icewind@owncloud.com, Frank Karlitschek
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* frank@owncloud.org
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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\Encryption;
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require_once __DIR__ . '/../3rdparty/Crypt_Blowfish/Blowfish.php';
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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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/**
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* @brief return encryption mode client or server side encryption
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* @param string $user name (use system wide setting if name=null)
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* @return string 'client' or 'server'
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*/
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public static function mode($user = null) {
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return 'server';
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}
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/**
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* @brief 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 = openssl_pkey_new(array('private_key_bits' => 4096));
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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, $privateKey)) {
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// Get public key
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$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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\OCP\Util::writeLog('Encryption library', openssl_error_string(), \OCP\Util::ERROR);
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}
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return $return;
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}
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/**
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* @brief 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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* @brief 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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* @brief Check if a file's contents contains an IV and is symmetrically encrypted
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* @param $content
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* @return boolean
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* @note see also OCA\Encryption\Util->isEncryptedPath()
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*/
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public static function isCatfileContent($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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* @brief Check if a file is encrypted via legacy system
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* @param $data
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* @param string $relPath The path of the file, relative to user/data;
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* e.g. filename or /Docs/filename, NOT admin/files/filename
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* @return boolean
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*/
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public static function isLegacyEncryptedContent($isCatFileContent, $relPath) {
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// Fetch all file metadata from DB
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$metadata = \OC\Files\Filesystem::getFileInfo($relPath, '');
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// If a file is flagged with encryption in DB, but isn't a
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// valid content + IV combination, it's probably using the
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// legacy encryption system
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if (isset($metadata['encrypted'])
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&& $metadata['encrypted'] === true
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&& $isCatFileContent === false
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) {
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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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* @brief Symmetrically encrypt a string
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* @param $plainContent
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* @param $iv
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* @param string $passphrase
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* @return string encrypted file content
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*/
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private static function encrypt($plainContent, $iv, $passphrase = '') {
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if ($encryptedContent = openssl_encrypt($plainContent, 'AES-128-CFB', $passphrase, false, $iv)) {
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return $encryptedContent;
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} else {
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\OCP\Util::writeLog('Encryption library', 'Encryption (symmetric) of content failed', \OCP\Util::ERROR);
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\OCP\Util::writeLog('Encryption library', openssl_error_string(), \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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* @brief Symmetrically decrypt a string
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* @param $encryptedContent
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* @param $iv
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* @param $passphrase
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* @throws \Exception
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* @return string decrypted file content
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*/
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private static function decrypt($encryptedContent, $iv, $passphrase) {
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if ($plainContent = openssl_decrypt($encryptedContent, 'AES-128-CFB', $passphrase, false, $iv)) {
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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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* @brief 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 $iv IV to be concatenated
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* @returns string concatenated content
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*/
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private static function concatIv($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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* @brief Split concatenated data and IV into respective parts
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* @param string $catFile concatenated data to be split
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* @returns array keys: encrypted, iv
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*/
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private static function splitIv($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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* @brief 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 $passphrase
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* @return bool|string
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* @return string encrypted content combined with IV
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* @note IV need not be specified, as it will be stored in the returned keyfile
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* and remain accessible therein.
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*/
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public static function symmetricEncryptFileContent($plainContent, $passphrase = '') {
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if (!$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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$iv = self::generateIv();
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if ($encryptedContent = self::encrypt($plainContent, $iv, $passphrase)) {
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// Combine content to encrypt with IV identifier and actual IV
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$catfile = self::concatIv($encryptedContent, $iv);
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$padded = self::addPadding($catfile);
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return $padded;
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} else {
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\OCP\Util::writeLog('Encryption library', 'Encryption (symmetric) of keyfile content failed', \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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* @brief Symmetrically decrypts keyfile content
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* @param $keyfileContent
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* @param string $passphrase
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* @throws \Exception
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* @return bool|string
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* @internal param string $source
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* @internal param string $target
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* @internal param string $key the decryption key
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* @returns string decrypted content
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*
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* This function decrypts a file
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*/
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public static function symmetricDecryptFileContent($keyfileContent, $passphrase = '') {
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if (!$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)) {
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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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* @brief Decrypt private key and check if the result is a valid keyfile
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* @param string $encryptedKey encrypted keyfile
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* @param string $passphrase to decrypt keyfile
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* @returns encrypted private key or false
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*
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* This function decrypts a file
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*/
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public static function decryptPrivateKey($encryptedKey, $passphrase) {
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$plainKey = self::symmetricDecryptFileContent($encryptedKey, $passphrase);
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// check if this a valid private key
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$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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* @brief 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 $publicKeys array keys must be the userId of corresponding user
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* @returns array keys: keys (array, key = userId), data
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* @note symmetricDecryptFileContent() can decrypt files created using this method
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*/
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public static function multiKeyEncrypt($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('Cannot mutliKeyEncrypt empty plain content');
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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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return false;
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}
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}
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/**
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* @brief Asymmetrically encrypt a file using multiple public keys
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* @param $encryptedContent
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* @param $shareKey
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* @param $privateKey
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* @return bool
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* @internal param string $plainContent content to be encrypted
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* @returns 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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return false;
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}
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if (openssl_open($encryptedContent, $plainContent, $shareKey, $privateKey)) {
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return $plainContent;
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} else {
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\OCP\Util::writeLog('Encryption library', 'Decryption (asymmetric) of sealed content with share-key "'.$shareKey.'" failed', \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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* @brief 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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* @brief Generate a pseudo random 1024kb ASCII key, used as file key
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* @returns $key Generated key
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*/
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public static function generateKey() {
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// Generate key
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if ($key = base64_encode(openssl_random_pseudo_bytes(183, $strong))) {
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if (!$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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* @brief Get the blowfish encryption handler for a key
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* @param $key string (optional)
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* @return \Crypt_Blowfish blowfish object
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*
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* if the key is left out, the default handler will be used
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*/
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private static function getBlowfish($key = '') {
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if ($key) {
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return new \Crypt_Blowfish($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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* @brief decrypts content using legacy blowfish system
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* @param string $content the cleartext message you want to decrypt
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* @param string $passphrase
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* @return string cleartext content
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*
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* This function decrypts an content
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*/
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public static function legacyDecrypt($content, $passphrase = '') {
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$bf = self::getBlowfish($passphrase);
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$decrypted = $bf->decrypt($content);
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return $decrypted;
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}
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/**
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* @param $data
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* @param string $key
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* @param int $maxLength
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* @return string
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*/
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public static function legacyBlockDecrypt($data, $key = '', $maxLength = 0) {
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$result = '';
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while (strlen($data)) {
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$result .= self::legacyDecrypt(substr($data, 0, 8192), $key);
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$data = substr($data, 8192);
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}
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if ($maxLength > 0) {
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return substr($result, 0, $maxLength);
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} else {
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return rtrim($result, "\0");
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}
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}
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}
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