, 2011 Robin Appelman * * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE * License as published by the Free Software Foundation; either * version 3 of the License, or any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU AFFERO GENERAL PUBLIC LICENSE for more details. * * You should have received a copy of the GNU Affero General Public * License along with this library. If not, see . * */ /** * transparently encrypted filestream * * you can use it as wrapper around an existing stream by setting CryptStream::$sourceStreams['foo']=array('path'=>$path,'stream'=>$stream) * and then fopen('crypt://streams/foo'); */ namespace OCA\Encryption; /** * @brief Provides 'crypt://' stream wrapper protocol. * @note We use a stream wrapper because it is the most secure way to handle * decrypted content transfers. There is no safe way to decrypt the entire file * somewhere on the server, so we have to encrypt and decrypt blocks on the fly. * @note Paths used with this protocol MUST BE RELATIVE. Use URLs like: * crypt://filename, or crypt://subdirectory/filename, NOT * crypt:///home/user/owncloud/data. Otherwise keyfiles will be put in * [owncloud]/data/user/files_encryption/keyfiles/home/user/owncloud/data and * will not be accessible to other methods. * @note Data read and written must always be 8192 bytes long, as this is the * buffer size used internally by PHP. The encryption process makes the input * data longer, and input is chunked into smaller pieces in order to result in * a 8192 encrypted block size. */ class Stream { public static $sourceStreams = array(); // TODO: make all below properties private again once unit testing is // configured correctly public $rawPath; // The raw path relative to the data dir public $relPath; // rel path to users file dir private $userId; private $handle; // Resource returned by fopen private $path; private $readBuffer; // For streams that dont support seeking private $meta = array(); // Header / meta for source stream private $count; private $writeCache; public $size; private $publicKey; private $keyfile; private $encKeyfile; private static $view; // a fsview object set to user dir private $rootView; // a fsview object set to '/' public function stream_open( $path, $mode, $options, &$opened_path ) { $this->userId = \OCP\User::getUser(); if ( ! isset( $this->rootView ) ) { $this->rootView = new \OC_FilesystemView( '/' ); } // Strip identifier text from path, this gives us the path relative to data//files $this->relPath = str_replace( 'crypt://', '', $path ); // rawPath is relative to the data directory $this->rawPath = $this->userId . '/files/' . $this->relPath; if ( dirname( $this->rawPath ) == 'streams' and isset( self::$sourceStreams[basename( $this->rawPath )] ) ) { // Is this just for unit testing purposes? $this->handle = self::$sourceStreams[basename( $this->rawPath )]['stream']; $this->path = self::$sourceStreams[basename( $this->rawPath )]['path']; $this->size = self::$sourceStreams[basename( $this->rawPath )]['size']; } else { if ( $mode == 'w' or $mode == 'w+' or $mode == 'wb' or $mode == 'wb+' ) { // We're writing a new file so start write counter with 0 bytes $this->size = 0; } else { $this->size = $this->rootView->filesize( $this->rawPath, $mode ); //$this->size = filesize( $this->rawPath ); } // Disable fileproxies so we can open the source file without recursive encryption \OC_FileProxy::$enabled = false; //$this->handle = fopen( $this->rawPath, $mode ); $this->handle = $this->rootView->fopen( $this->rawPath, $mode ); \OC_FileProxy::$enabled = true; if ( ! is_resource( $this->handle ) ) { \OCP\Util::writeLog( 'files_encryption', 'failed to open file "' . $this->rawPath . '"', \OCP\Util::ERROR ); } else { $this->meta = stream_get_meta_data( $this->handle ); } } return is_resource( $this->handle ); } public function stream_seek( $offset, $whence = SEEK_SET ) { $this->flush(); fseek( $this->handle, $offset, $whence ); } public function stream_tell() { return ftell($this->handle); } public function stream_read( $count ) { $this->writeCache = ''; if ( $count != 8192 ) { // $count will always be 8192 https://bugs.php.net/bug.php?id=21641 // This makes this function a lot simpler, but will break this class if the above 'bug' gets 'fixed' \OCP\Util::writeLog( 'files_encryption', 'PHP "bug" 21641 no longer holds, decryption system requires refactoring', \OCP\Util::FATAL ); die(); } // $pos = ftell( $this->handle ); // // Get the data from the file handle $data = fread( $this->handle, 8192 ); if ( strlen( $data ) ) { $this->getKey(); $result = Crypt::symmetricDecryptFileContent( $data, $this->keyfile ); } else { $result = ''; } // $length = $this->size - $pos; // // if ( $length < 8192 ) { // // $result = substr( $result, 0, $length ); // // } return $result; } /** * @brief Encrypt and pad data ready for writing to disk * @param string $plainData data to be encrypted * @param string $key key to use for encryption * @return encrypted data on success, false on failure */ public function preWriteEncrypt( $plainData, $key ) { // Encrypt data to 'catfile', which includes IV if ( $encrypted = Crypt::symmetricEncryptFileContent( $plainData, $key ) ) { return $encrypted; } else { return false; } } /** * @brief Get the keyfile for the current file, generate one if necessary * @param bool $generate if true, a new key will be generated if none can be found * @return bool true on key found and set, false on key not found and new key generated and set */ public function getKey() { // If a keyfile already exists for a file named identically to // file to be written if ( $this->rootView->file_exists( $this->userId . '/'. 'files_encryption' . '/' . 'keyfiles' . '/' . $this->relPath . '.key' ) ) { // TODO: add error handling for when file exists but no // keyfile // Fetch existing keyfile $this->encKeyfile = Keymanager::getFileKey( $this->rootView, $this->userId, $this->relPath ); $this->getUser(); $session = new Session($this->rootView); $privateKey = $session->getPrivateKey( $this->userId ); $this->keyfile = Crypt::keyDecrypt( $this->encKeyfile, $privateKey ); return true; } else { return false; } } public function getuser() { // Only get the user again if it isn't already set if ( empty( $this->userId ) ) { // TODO: Move this user call out of here - it belongs // elsewhere $this->userId = \OCP\User::getUser(); } // TODO: Add a method for getting the user in case OCP\User:: // getUser() doesn't work (can that scenario ever occur?) } /** * @brief Handle plain data from the stream, and write it in 8192 byte blocks * @param string $data data to be written to disk * @note the data will be written to the path stored in the stream handle, set in stream_open() * @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 * @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 * @note Padding is added to each encrypted block to ensure that the resulting block is exactly 8192 bytes. This is removed during stream_read * @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 */ public function stream_write( $data ) { // Disable the file proxies so that encryption is not // automatically attempted when the file is written to disk - // we are handling that separately here and we don't want to // get into an infinite loop \OC_FileProxy::$enabled = false; // Get the length of the unencrypted data that we are handling $length = strlen( $data ); // So far this round, no data has been written $written = 0; // Find out where we are up to in the writing of data to the // file $pointer = ftell( $this->handle ); // Make sure the userId is set $this->getuser(); // TODO: Check if file is shared, if so, use multiKeyEncrypt and // save shareKeys in necessary user directories // Get / generate the keyfile for the file we're handling // If we're writing a new file (not overwriting an existing // one), save the newly generated keyfile if ( ! $this->getKey() ) { // TODO: Reuse the keyfile, it it exists, instead of making a new one $this->keyfile = Crypt::generateKey(); $this->publicKey = Keymanager::getPublicKey( $this->rootView, $this->userId ); $this->encKeyfile = Crypt::keyEncrypt( $this->keyfile, $this->publicKey ); $view = new \OC_FilesystemView( '/' ); $userId = \OCP\User::getUser(); // Save the new encrypted file key Keymanager::setFileKey( $view, $this->relPath, $userId, $this->encKeyfile ); } // If extra data is left over from the last round, make sure it // is integrated into the next 6126 / 8192 block if ( $this->writeCache ) { // Concat writeCache to start of $data $data = $this->writeCache . $data; // Clear the write cache, ready for resuse - it has been // flushed and its old contents processed $this->writeCache = ''; } // // // Make sure we always start on a block start if ( 0 != ( $pointer % 8192 ) ) { // if the current position of // file indicator is not aligned to a 8192 byte block, fix it // so that it is // fseek( $this->handle, - ( $pointer % 8192 ), SEEK_CUR ); // // $pointer = ftell( $this->handle ); // // $unencryptedNewBlock = fread( $this->handle, 8192 ); // // fseek( $this->handle, - ( $currentPos % 8192 ), SEEK_CUR ); // // $block = Crypt::symmetricDecryptFileContent( $unencryptedNewBlock, $this->keyfile ); // // $x = substr( $block, 0, $currentPos % 8192 ); // // $data = $x . $data; // // fseek( $this->handle, - ( $currentPos % 8192 ), SEEK_CUR ); // } // $currentPos = ftell( $this->handle ); // // While there still remains somed data to be processed & written while( strlen( $data ) > 0 ) { // // // Remaining length for this iteration, not of the // // entire file (may be greater than 8192 bytes) // $remainingLength = strlen( $data ); // // // If data remaining to be written is less than the // // size of 1 6126 byte block if ( strlen( $data ) < 6126 ) { // Set writeCache to contents of $data // The writeCache will be carried over to the // next write round, and added to the start of // $data to ensure that written blocks are // always the correct length. If there is still // data in writeCache after the writing round // has finished, then the data will be written // to disk by $this->flush(). $this->writeCache = $data; // Clear $data ready for next round $data = ''; // } else { // Read the chunk from the start of $data $chunk = substr( $data, 0, 6126 ); $encrypted = $this->preWriteEncrypt( $chunk, $this->keyfile ); // Write the data chunk to disk. This will be // attended to the last data chunk if the file // being handled totals more than 6126 bytes fwrite( $this->handle, $encrypted ); $writtenLen = strlen( $encrypted ); //fseek( $this->handle, $writtenLen, SEEK_CUR ); // Remove the chunk we just processed from // $data, leaving only unprocessed data in $data // var, for handling on the next round $data = substr( $data, 6126 ); } } $this->size = max( $this->size, $pointer + $length ); return $length; } public function stream_set_option( $option, $arg1, $arg2 ) { switch($option) { case STREAM_OPTION_BLOCKING: stream_set_blocking( $this->handle, $arg1 ); break; case STREAM_OPTION_READ_TIMEOUT: stream_set_timeout( $this->handle, $arg1, $arg2 ); break; case STREAM_OPTION_WRITE_BUFFER: stream_set_write_buffer( $this->handle, $arg1, $arg2 ); } } public function stream_stat() { return fstat($this->handle); } public function stream_lock( $mode ) { flock( $this->handle, $mode ); } public function stream_flush() { return fflush( $this->handle ); // Not a typo: http://php.net/manual/en/function.fflush.php } public function stream_eof() { return feof($this->handle); } private function flush() { if ( $this->writeCache ) { // Set keyfile property for file in question $this->getKey(); $encrypted = $this->preWriteEncrypt( $this->writeCache, $this->keyfile ); fwrite( $this->handle, $encrypted ); $this->writeCache = ''; } } public function stream_close() { $this->flush(); if ( $this->meta['mode']!='r' and $this->meta['mode']!='rb' ) { \OC\Files\Filesystem::putFileInfo( $this->path, array( 'encrypted' => true, 'size' => $this->size ), '' ); } return fclose( $this->handle ); } }