484 lines
13 KiB
PHP
484 lines
13 KiB
PHP
<?php
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/**
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* ownCloud
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*
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* @author Robin Appelman
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* @copyright 2012 Sam Tuke <samtuke@owncloud.com>, 2011 Robin Appelman
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* <icewind1991@gmail.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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/**
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* transparently encrypted filestream
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*
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* you can use it as wrapper around an existing stream by setting CryptStream::$sourceStreams['foo']=array('path'=>$path,'stream'=>$stream)
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* and then fopen('crypt://streams/foo');
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*/
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namespace OCA\Encryption;
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/**
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* @brief Provides 'crypt://' stream wrapper protocol.
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* @note We use a stream wrapper because it is the most secure way to handle
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* decrypted content transfers. There is no safe way to decrypt the entire file
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* somewhere on the server, so we have to encrypt and decrypt blocks on the fly.
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* @note Paths used with this protocol MUST BE RELATIVE. Use URLs like:
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* crypt://filename, or crypt://subdirectory/filename, NOT
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* crypt:///home/user/owncloud/data. Otherwise keyfiles will be put in
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* [owncloud]/data/user/files_encryption/keyfiles/home/user/owncloud/data and
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* will not be accessible to other methods.
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* @note Data read and written must always be 8192 bytes long, as this is the
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* buffer size used internally by PHP. The encryption process makes the input
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* data longer, and input is chunked into smaller pieces in order to result in
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* a 8192 encrypted block size.
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* @note When files are deleted via webdav, or when they are updated and the
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* previous version deleted, this is handled by OC\Files\View, and thus the
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* encryption proxies are used and keyfiles deleted.
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*/
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class Stream
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{
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private $plainKey;
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private $encKeyfiles;
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private $rawPath; // The raw path relative to the data dir
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private $relPath; // rel path to users file dir
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private $userId;
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private $handle; // Resource returned by fopen
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private $path;
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private $readBuffer; // For streams that dont support seeking
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private $meta = array(); // Header / meta for source stream
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private $count;
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private $writeCache;
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private $size;
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private $unencryptedSize;
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private $publicKey;
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private $keyfile;
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private $encKeyfile;
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private static $view; // a fsview object set to user dir
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private $rootView; // a fsview object set to '/'
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/**
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* @param $path
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* @param $mode
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* @param $options
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* @param $opened_path
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* @return bool
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*/
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public function stream_open( $path, $mode, $options, &$opened_path ) {
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if ( !isset( $this->rootView ) ) {
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$this->rootView = new \OC_FilesystemView( '/' );
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}
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$util = new Util( $this->rootView, \OCP\USER::getUser() );
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$this->userId = $util->getUserId();
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// Strip identifier text from path, this gives us the path relative to data/<user>/files
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$this->relPath = \OC\Files\Filesystem::normalizePath( str_replace( 'crypt://', '', $path ) );
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// rawPath is relative to the data directory
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$this->rawPath = $util->getUserFilesDir() . $this->relPath;
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// Disable fileproxies so we can get the file size and open the source file without recursive encryption
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$proxyStatus = \OC_FileProxy::$enabled;
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\OC_FileProxy::$enabled = false;
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if (
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$mode == 'w'
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or $mode == 'w+'
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or $mode == 'wb'
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or $mode == 'wb+'
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) {
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// We're writing a new file so start write counter with 0 bytes
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$this->size = 0;
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$this->unencryptedSize = 0;
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} else {
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$this->size = $this->rootView->filesize( $this->rawPath, $mode );
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}
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$this->handle = $this->rootView->fopen( $this->rawPath, $mode );
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\OC_FileProxy::$enabled = $proxyStatus;
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if ( !is_resource( $this->handle ) ) {
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\OCP\Util::writeLog( 'files_encryption', 'failed to open file "' . $this->rawPath . '"', \OCP\Util::ERROR );
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} else {
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$this->meta = stream_get_meta_data( $this->handle );
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}
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return is_resource( $this->handle );
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}
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/**
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* @param $offset
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* @param int $whence
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*/
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public function stream_seek( $offset, $whence = SEEK_SET ) {
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$this->flush();
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fseek( $this->handle, $offset, $whence );
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}
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/**
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* @param $count
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* @return bool|string
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* @throws \Exception
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*/
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public function stream_read( $count ) {
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$this->writeCache = '';
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if ( $count != 8192 ) {
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// $count will always be 8192 https://bugs.php.net/bug.php?id=21641
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// This makes this function a lot simpler, but will break this class if the above 'bug' gets 'fixed'
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\OCP\Util::writeLog( 'files_encryption', 'PHP "bug" 21641 no longer holds, decryption system requires refactoring', \OCP\Util::FATAL );
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die();
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}
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// Get the data from the file handle
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$data = fread( $this->handle, 8192 );
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$result = '';
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if ( strlen( $data ) ) {
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if ( !$this->getKey() ) {
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// Error! We don't have a key to decrypt the file with
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throw new \Exception( 'Encryption key not found for "' . $this->rawPath . '" during attempted read via stream' );
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}
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// Decrypt data
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$result = Crypt::symmetricDecryptFileContent( $data, $this->plainKey );
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}
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return $result;
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}
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/**
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* @brief Encrypt and pad data ready for writing to disk
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* @param string $plainData data to be encrypted
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* @param string $key key to use for encryption
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* @return string encrypted data on success, false on failure
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*/
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public function preWriteEncrypt( $plainData, $key ) {
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// Encrypt data to 'catfile', which includes IV
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if ( $encrypted = Crypt::symmetricEncryptFileContent( $plainData, $key ) ) {
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return $encrypted;
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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 Fetch the plain encryption key for the file and set it as plainKey property
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* @internal param bool $generate if true, a new key will be generated if none can be found
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* @return bool true on key found and set, false on key not found and new key generated and set
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*/
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public function getKey() {
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// Check if key is already set
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if ( isset( $this->plainKey ) && isset( $this->encKeyfile ) ) {
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return true;
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}
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// Fetch and decrypt keyfile
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// Fetch existing keyfile
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$this->encKeyfile = Keymanager::getFileKey( $this->rootView, $this->userId, $this->relPath );
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// If a keyfile already exists
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if ( $this->encKeyfile ) {
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$session = new Session( $this->rootView );
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$privateKey = $session->getPrivateKey( $this->userId );
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$shareKey = Keymanager::getShareKey( $this->rootView, $this->userId, $this->relPath );
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$this->plainKey = Crypt::multiKeyDecrypt( $this->encKeyfile, $shareKey, $privateKey );
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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 Handle plain data from the stream, and write it in 8192 byte blocks
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* @param string $data data to be written to disk
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* @note the data will be written to the path stored in the stream handle, set in stream_open()
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* @note $data is only ever be a maximum of 8192 bytes long. This is set by PHP internally. stream_write() is called multiple times in a loop on data larger than 8192 bytes
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* @note Because the encryption process used increases the length of $data, a writeCache is used to carry over data which would not fit in the required block size
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* @note Padding is added to each encrypted block to ensure that the resulting block is exactly 8192 bytes. This is removed during stream_read
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* @note PHP automatically updates the file pointer after writing data to reflect it's length. There is generally no need to update the poitner manually using fseek
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*/
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public function stream_write( $data ) {
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// Disable the file proxies so that encryption is not
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// automatically attempted when the file is written to disk -
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// we are handling that separately here and we don't want to
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// get into an infinite loop
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$proxyStatus = \OC_FileProxy::$enabled;
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\OC_FileProxy::$enabled = false;
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// Get the length of the unencrypted data that we are handling
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$length = strlen( $data );
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// Find out where we are up to in the writing of data to the
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// file
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$pointer = ftell( $this->handle );
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// Get / generate the keyfile for the file we're handling
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// If we're writing a new file (not overwriting an existing
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// one), save the newly generated keyfile
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if ( !$this->getKey() ) {
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$this->plainKey = Crypt::generateKey();
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}
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// If extra data is left over from the last round, make sure it
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// is integrated into the next 6126 / 8192 block
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if ( $this->writeCache ) {
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// Concat writeCache to start of $data
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$data = $this->writeCache . $data;
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// Clear the write cache, ready for reuse - it has been
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// flushed and its old contents processed
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$this->writeCache = '';
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}
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// While there still remains some data to be processed & written
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while ( strlen( $data ) > 0 ) {
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// Remaining length for this iteration, not of the
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// entire file (may be greater than 8192 bytes)
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$remainingLength = strlen( $data );
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// If data remaining to be written is less than the
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// size of 1 6126 byte block
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if ( $remainingLength < 6126 ) {
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// Set writeCache to contents of $data
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// The writeCache will be carried over to the
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// next write round, and added to the start of
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// $data to ensure that written blocks are
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// always the correct length. If there is still
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// data in writeCache after the writing round
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// has finished, then the data will be written
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// to disk by $this->flush().
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$this->writeCache = $data;
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// Clear $data ready for next round
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$data = '';
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} else {
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// Read the chunk from the start of $data
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$chunk = substr( $data, 0, 6126 );
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$encrypted = $this->preWriteEncrypt( $chunk, $this->plainKey );
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// Write the data chunk to disk. This will be
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// attended to the last data chunk if the file
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// being handled totals more than 6126 bytes
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fwrite( $this->handle, $encrypted );
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// Remove the chunk we just processed from
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// $data, leaving only unprocessed data in $data
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// var, for handling on the next round
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$data = substr( $data, 6126 );
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}
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}
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$this->size = max( $this->size, $pointer + $length );
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$this->unencryptedSize += $length;
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\OC_FileProxy::$enabled = $proxyStatus;
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return $length;
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}
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/**
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* @param $option
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* @param $arg1
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* @param $arg2
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*/
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public function stream_set_option( $option, $arg1, $arg2 ) {
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$return = false;
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switch ( $option ) {
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case STREAM_OPTION_BLOCKING:
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$return = stream_set_blocking( $this->handle, $arg1 );
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break;
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case STREAM_OPTION_READ_TIMEOUT:
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$return = stream_set_timeout( $this->handle, $arg1, $arg2 );
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break;
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case STREAM_OPTION_WRITE_BUFFER:
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$return = stream_set_write_buffer( $this->handle, $arg1 );
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}
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return $return;
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}
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/**
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* @return array
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*/
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public function stream_stat() {
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return fstat( $this->handle );
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}
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/**
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* @param $mode
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*/
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public function stream_lock( $mode ) {
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return flock( $this->handle, $mode );
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}
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/**
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* @return bool
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*/
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public function stream_flush() {
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return fflush( $this->handle );
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// Not a typo: http://php.net/manual/en/function.fflush.php
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}
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/**
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* @return bool
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*/
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public function stream_eof() {
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return feof( $this->handle );
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}
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private function flush() {
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if ( $this->writeCache ) {
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// Set keyfile property for file in question
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$this->getKey();
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$encrypted = $this->preWriteEncrypt( $this->writeCache, $this->plainKey );
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fwrite( $this->handle, $encrypted );
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$this->writeCache = '';
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}
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}
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/**
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* @return bool
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*/
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public function stream_close() {
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$this->flush();
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if (
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$this->meta['mode'] != 'r'
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and $this->meta['mode'] != 'rb'
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and $this->size > 0
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) {
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// Disable encryption proxy to prevent recursive calls
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$proxyStatus = \OC_FileProxy::$enabled;
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\OC_FileProxy::$enabled = false;
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// Fetch user's public key
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$this->publicKey = Keymanager::getPublicKey( $this->rootView, $this->userId );
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// Check if OC sharing api is enabled
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$sharingEnabled = \OCP\Share::isEnabled();
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$util = new Util( $this->rootView, $this->userId );
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// Get all users sharing the file includes current user
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$uniqueUserIds = $util->getSharingUsersArray( $sharingEnabled, $this->relPath, $this->userId );
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// Fetch public keys for all sharing users
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$publicKeys = Keymanager::getPublicKeys( $this->rootView, $uniqueUserIds );
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// Encrypt enc key for all sharing users
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$this->encKeyfiles = Crypt::multiKeyEncrypt( $this->plainKey, $publicKeys );
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$view = new \OC_FilesystemView( '/' );
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// Save the new encrypted file key
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Keymanager::setFileKey( $this->rootView, $this->relPath, $this->userId, $this->encKeyfiles['data'] );
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// Save the sharekeys
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Keymanager::setShareKeys( $view, $this->relPath, $this->encKeyfiles['keys'] );
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// get file info
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$fileInfo = $view->getFileInfo( $this->rawPath );
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if ( !is_array( $fileInfo ) ) {
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$fileInfo = array();
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}
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// Re-enable proxy - our work is done
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\OC_FileProxy::$enabled = $proxyStatus;
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// set encryption data
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$fileInfo['encrypted'] = true;
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$fileInfo['size'] = $this->size;
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$fileInfo['unencrypted_size'] = $this->unencryptedSize;
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// set fileinfo
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$view->putFileInfo( $this->rawPath, $fileInfo );
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}
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return fclose( $this->handle );
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}
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}
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