nextcloud/apps/files_encryption/lib/stream.php

701 lines
22 KiB
PHP

<?php
/**
* @author Björn Schießle <schiessle@owncloud.com>
* @author Florin Peter <github@florin-peter.de>
* @author jknockaert <jasper@knockaert.nl>
* @author Joas Schilling <nickvergessen@owncloud.com>
* @author Morris Jobke <hey@morrisjobke.de>
* @author Robin McCorkell <rmccorkell@karoshi.org.uk>
* @author Sam Tuke <mail@samtuke.com>
* @author Vincent Petry <pvince81@owncloud.com>
*
* @copyright Copyright (c) 2015, ownCloud, Inc.
* @license AGPL-3.0
*
* This code is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program 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, version 3,
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
/**
* 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\Files_Encryption;
use OCA\Files_Encryption\Exception\EncryptionException;
/**
* 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.
* @note When files are deleted via webdav, or when they are updated and the
* previous version deleted, this is handled by OC\Files\View, and thus the
* encryption proxies are used and keyfiles deleted.
*/
class Stream {
const PADDING_CHAR = '-';
private $plainKey;
private $encKeyfiles;
private $rawPath; // The raw path relative to the data dir
private $relPath; // rel path to users file dir
private $userId;
private $keyId;
private $handle; // Resource returned by fopen
private $meta = array(); // Header / meta for source stream
private $cache; // Current block unencrypted
private $position; // Current pointer position in the unencrypted stream
private $writeFlag; // Flag to write current block when leaving it
private $size;
private $headerSize = 0; // Size of header
private $unencryptedSize;
private $publicKey;
private $encKeyfile;
private $newFile; // helper var, we only need to write the keyfile for new files
private $isLocalTmpFile = false; // do we operate on a local tmp file
private $localTmpFile; // path of local tmp file
private $containHeader = false; // the file contain a header
private $cipher; // cipher used for encryption/decryption
/** @var \OCA\Files_Encryption\Util */
private $util;
/**
* @var \OC\Files\View
*/
private $rootView; // a fsview object set to '/'
/**
* @var \OCA\Files_Encryption\Session
*/
private $session;
private $privateKey;
/**
* @param string $path raw path relative to data/
* @param string $mode
* @param int $options
* @param string $opened_path
* @return bool
* @throw \OCA\Files_Encryption\Exception\EncryptionException
*/
public function stream_open($path, $mode, $options, &$opened_path) {
// read default cipher from config
$this->cipher = Helper::getCipher();
// assume that the file already exist before we decide it finally in getKey()
$this->newFile = false;
$this->rootView = new \OC\Files\View('/');
$this->session = new Session($this->rootView);
$this->privateKey = $this->session->getPrivateKey();
if ($this->privateKey === false) {
throw new EncryptionException('Session does not contain a private key, maybe your login password changed?',
EncryptionException::PRIVATE_KEY_MISSING);
}
$normalizedPath = \OC\Files\Filesystem::normalizePath(str_replace('crypt://', '', $path));
$originalFile = Helper::getPathFromTmpFile($normalizedPath);
if ($originalFile) {
$this->rawPath = $originalFile;
$this->isLocalTmpFile = true;
$this->localTmpFile = $normalizedPath;
} else {
$this->rawPath = $normalizedPath;
}
$this->util = new Util($this->rootView, Helper::getUser($this->rawPath));
// get the key ID which we want to use, can be the users key or the
// public share key
$this->keyId = $this->util->getKeyId();
$fileType = Helper::detectFileType($this->rawPath);
switch ($fileType) {
case Util::FILE_TYPE_FILE:
$this->relPath = Helper::stripUserFilesPath($this->rawPath);
$user = \OC::$server->getUserSession()->getUser();
$this->userId = $user ? $user->getUID() : Helper::getUserFromPath($this->rawPath);
break;
case Util::FILE_TYPE_VERSION:
$this->relPath = Helper::getPathFromVersion($this->rawPath);
$this->userId = Helper::getUserFromPath($this->rawPath);
break;
case Util::FILE_TYPE_CACHE:
$this->relPath = Helper::getPathFromCachedFile($this->rawPath);
Helper::mkdirr($this->rawPath, new \OC\Files\View('/'));
$user = \OC::$server->getUserSession()->getUser();
$this->userId = $user ? $user->getUID() : Helper::getUserFromPath($this->rawPath);
break;
default:
\OCP\Util::writeLog('Encryption library', 'failed to open file "' . $this->rawPath . '" expecting a path to "files", "files_versions" or "cache"', \OCP\Util::ERROR);
return false;
}
// Disable fileproxies so we can get the file size and open the source file without recursive encryption
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
$this->position = 0;
$this->cache = '';
$this->writeFlag = 0;
// Setting handle so it can be used for reading the header
if ($this->isLocalTmpFile) {
$this->handle = fopen($this->localTmpFile, $mode);
} else {
$this->handle = $this->rootView->fopen($this->rawPath, $mode);
}
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;
$this->unencryptedSize = 0;
} else {
$this->size = $this->rootView->filesize($this->rawPath);
\OC_FileProxy::$enabled = true;
$this->unencryptedSize = $this->rootView->filesize($this->rawPath);
\OC_FileProxy::$enabled = false;
$this->readHeader();
}
\OC_FileProxy::$enabled = $proxyStatus;
if (!is_resource($this->handle)) {
\OCP\Util::writeLog('Encryption library', 'failed to open file "' . $this->rawPath . '"', \OCP\Util::ERROR);
} else {
$this->meta = stream_get_meta_data($this->handle);
// sometimes fopen changes the mode, e.g. for a url "r" convert to "r+"
// but we need to remember the original access type
$this->meta['mode'] = $mode;
}
return is_resource($this->handle);
}
private function readHeader() {
if (is_resource($this->handle)) {
$data = fread($this->handle, Crypt::BLOCKSIZE);
$header = Crypt::parseHeader($data);
$this->cipher = Crypt::getCipher($header);
// remeber that we found a header
if (!empty($header)) {
$this->containHeader = true;
$this->headerSize = Crypt::BLOCKSIZE;
// if there's no header then decrypt the block and store it in the cache
} else {
if (!$this->getKey()) {
throw new \Exception('Encryption key not found for "' . $this->rawPath . '" during attempted read via stream');
} else {
$this->cache = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
}
}
}
}
/**
* Returns the current position of the file pointer
* @return int position of the file pointer
*/
public function stream_tell() {
return $this->position;
}
/**
* @param int $offset
* @param int $whence
* @return bool true if fseek was successful, otherwise false
*/
// seeking the stream tries to move the pointer on the encrypted stream to the beginning of the target block
// if that works, it flushes the current block and changes the position in the unencrypted stream
public function stream_seek($offset, $whence = SEEK_SET) {
// this wrapper needs to return "true" for success.
// the fseek call itself returns 0 on succeess
$return=false;
switch($whence) {
case SEEK_SET:
if($offset < $this->unencryptedSize && $offset >= 0) {
$newPosition=$offset;
}
break;
case SEEK_CUR:
if($offset>=0) {
$newPosition=$offset+$this->position;
}
break;
case SEEK_END:
if($this->unencryptedSize + $offset >= 0) {
$newPosition=$this->unencryptedSize+$offset;
}
break;
default:
return $return;
}
$newFilePosition=floor($newPosition/6126)*Crypt::BLOCKSIZE+$this->headerSize;
if (fseek($this->handle, $newFilePosition)===0) {
$this->flush();
$this->position=$newPosition;
$return=true;
}
return $return;
}
/**
* @param int $count
* @return bool|string
* @throws \OCA\Files_Encryption\Exception\EncryptionException
*/
public function stream_read($count) {
$result = '';
// limit to the end of the unencrypted file; otherwise getFileSize will fail and it is good practise anyway
$count=min($count,$this->unencryptedSize - $this->position);
// loop over the 6126 sized unencrypted blocks
while ($count > 0) {
$remainingLength = $count;
// update the cache of the current block
$this->readCache();
// determine the relative position in the current block
$blockPosition=($this->position % 6126);
// if entire read inside current block then only position needs to be updated
if ($remainingLength<(6126 - $blockPosition)) {
$result .= substr($this->cache,$blockPosition,$remainingLength);
$this->position += $remainingLength;
$count=0;
// otherwise remainder of current block is fetched, the block is flushed and the position updated
} else {
$result .= substr($this->cache,$blockPosition);
$this->flush();
$this->position += (6126 - $blockPosition);
$count -= (6126 - $blockPosition);
}
}
return $result;
}
/**
* Encrypt and pad data ready for writing to disk
* @param string $plainData data to be encrypted
* @param string $key key to use for encryption
* @return string encrypted data on success, false on failure
*/
public function preWriteEncrypt($plainData, $key) {
// Encrypt data to 'catfile', which includes IV
if ($encrypted = Crypt::symmetricEncryptFileContent($plainData, $key, $this->cipher)) {
return $encrypted;
} else {
return false;
}
}
/**
* Fetch the plain encryption key for the file and set it as plainKey property
* @internal param bool $generate if true, a new key will be generated if none can be found
* @return bool true on key found and set, false on key not found and new key generated and set
*/
public function getKey() {
// Check if key is already set
if (isset($this->plainKey) && isset($this->encKeyfile)) {
return true;
}
// Fetch and decrypt keyfile
// Fetch existing keyfile
$this->encKeyfile = Keymanager::getFileKey($this->rootView, $this->util, $this->relPath);
// If a keyfile already exists
if ($this->encKeyfile) {
$shareKey = Keymanager::getShareKey($this->rootView, $this->keyId, $this->util, $this->relPath);
// if there is no valid private key return false
if ($this->privateKey === false) {
// if private key is not valid redirect user to a error page
Helper::redirectToErrorPage($this->session);
return false;
}
if ($shareKey === false) {
// if no share key is available redirect user to a error page
Helper::redirectToErrorPage($this->session, Crypt::ENCRYPTION_NO_SHARE_KEY_FOUND);
return false;
}
$this->plainKey = Crypt::multiKeyDecrypt($this->encKeyfile, $shareKey, $this->privateKey);
return true;
} else {
$this->newFile = true;
return false;
}
}
/**
* write header at beginning of encrypted file
*
* @throws \OCA\Files_Encryption\Exception\EncryptionException
*/
private function writeHeader() {
$header = Crypt::generateHeader();
if (strlen($header) > Crypt::BLOCKSIZE) {
throw new EncryptionException('max header size exceeded', EncryptionException::ENCRYPTION_HEADER_TO_LARGE);
}
$paddedHeader = str_pad($header, Crypt::BLOCKSIZE, self::PADDING_CHAR, STR_PAD_RIGHT);
fwrite($this->handle, $paddedHeader);
$this->headerWritten = true;
$this->containHeader = true;
$this->headerSize = Crypt::BLOCKSIZE;
$this->size += $this->headerSize;
}
/**
* 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 $data, a cache is used to carry over data which would not fit in the required block size
* @note Padding is added to each encrypted block to ensure that the resulting block is exactly 8192 bytes. This is removed during stream_read
* @note PHP automatically updates the file pointer after writing data to reflect it's length. There is generally no need to update the poitner manually using fseek
*/
public function stream_write($data) {
// if there is no valid private key return false
if ($this->privateKey === false) {
$this->size = 0;
return strlen($data);
}
if ($this->size === 0) {
$this->writeHeader();
}
// Get / generate the keyfile for the file we're handling
// If we're writing a new file (not overwriting an existing
// one), save the newly generated keyfile
if (!$this->getKey()) {
$this->plainKey = Crypt::generateKey();
}
$length=0;
// loop over $data to fit it in 6126 sized unencrypted blocks
while (strlen($data) > 0) {
$remainingLength = strlen($data);
// set the cache to the current 6126 block
$this->readCache();
// only allow writes on seekable streams, or at the end of the encrypted stream
// for seekable streams the pointer is moved back to the beginning of the encrypted block
// flush will start writing there when the position moves to another block
if((fseek($this->handle, floor($this->position/6126)*Crypt::BLOCKSIZE + $this->headerSize) === 0) || (floor($this->position/6126)*Crypt::BLOCKSIZE + $this->headerSize === $this->size)) {
// switch the writeFlag so flush() will write the block
$this->writeFlag=1;
// determine the relative position in the current block
$blockPosition=($this->position % 6126);
// check if $data fits in current block
// if so, overwrite existing data (if any)
// update position and liberate $data
if ($remainingLength<(6126 - $blockPosition)) {
$this->cache=substr($this->cache,0,$blockPosition).$data.substr($this->cache,$blockPosition+$remainingLength);
$this->position += $remainingLength;
$length += $remainingLength;
$data = '';
// if $data doens't fit the current block, the fill the current block and reiterate
// after the block is filled, it is flushed and $data is updated
} else {
$this->cache=substr($this->cache,0,$blockPosition).substr($data,0,6126-$blockPosition);
$this->flush();
$this->position += (6126 - $blockPosition);
$length += (6126 - $blockPosition);
$data = substr($data, 6126 - $blockPosition);
}
} else {
$data='';
}
}
$this->unencryptedSize = max($this->unencryptedSize,$this->position);
return $length;
}
/**
* @param int $option
* @param int $arg1
* @param int|null $arg2
*/
public function stream_set_option($option, $arg1, $arg2) {
$return = false;
switch ($option) {
case STREAM_OPTION_BLOCKING:
$return = stream_set_blocking($this->handle, $arg1);
break;
case STREAM_OPTION_READ_TIMEOUT:
$return = stream_set_timeout($this->handle, $arg1, $arg2);
break;
case STREAM_OPTION_WRITE_BUFFER:
$return = stream_set_write_buffer($this->handle, $arg1);
}
return $return;
}
/**
* @return array
*/
public function stream_stat() {
return fstat($this->handle);
}
/**
* @param int $mode
*/
public function stream_lock($mode) {
return flock($this->handle, $mode);
}
/**
* @return bool
*/
public function stream_flush() {
$this->flush();
return fflush($this->handle);
// Not a typo: http://php.net/manual/en/function.fflush.php
}
/**
* @return bool
*/
public function stream_eof() {
return ($this->position>=$this->unencryptedSize);
}
private function flush() {
// write to disk only when writeFlag was set to 1
if ($this->writeFlag === 1) {
// 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
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
// Set keyfile property for file in question
$this->getKey();
$encrypted = $this->preWriteEncrypt($this->cache, $this->plainKey);
fwrite($this->handle, $encrypted);
$this->writeFlag = 0;
$this->size = max($this->size,ftell($this->handle));
\OC_FileProxy::$enabled = $proxyStatus;
}
// always empty the cache (otherwise readCache() will not fill it with the new block)
$this->cache = '';
}
private function readCache() {
// cache should always be empty string when this function is called
// don't try to fill the cache when trying to write at the end of the unencrypted file when it coincides with new block
if ($this->cache === '' && !($this->position===$this->unencryptedSize && ($this->position % 6126)===0)) {
// Get the data from the file handle
$data = fread($this->handle, Crypt::BLOCKSIZE);
$result = '';
if (strlen($data)) {
if (!$this->getKey()) {
// Error! We don't have a key to decrypt the file with
throw new \Exception('Encryption key not found for "'. $this->rawPath . '" during attempted read via stream');
} else {
// Decrypt data
$result = Crypt::symmetricDecryptFileContent($data, $this->plainKey, $this->cipher);
}
}
$this->cache = $result;
}
}
/**
* @return bool
*/
public function stream_close() {
$this->flush();
// if there is no valid private key return false
if ($this->privateKey === false) {
// cleanup
if ($this->meta['mode'] !== 'r' && $this->meta['mode'] !== 'rb' && !$this->isLocalTmpFile) {
// Disable encryption proxy to prevent recursive calls
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
if ($this->rootView->file_exists($this->rawPath) && $this->size === $this->headerSize) {
fclose($this->handle);
$this->rootView->unlink($this->rawPath);
}
// Re-enable proxy - our work is done
\OC_FileProxy::$enabled = $proxyStatus;
}
// if private key is not valid redirect user to a error page
Helper::redirectToErrorPage($this->session);
}
if (
$this->meta['mode'] !== 'r' &&
$this->meta['mode'] !== 'rb' &&
$this->isLocalTmpFile === false &&
$this->size > $this->headerSize &&
$this->unencryptedSize > 0
) {
// only write keyfiles if it was a new file
if ($this->newFile === true) {
// Disable encryption proxy to prevent recursive calls
$proxyStatus = \OC_FileProxy::$enabled;
\OC_FileProxy::$enabled = false;
// Fetch user's public key
$this->publicKey = Keymanager::getPublicKey($this->rootView, $this->keyId);
// Check if OC sharing api is enabled
$sharingEnabled = \OCP\Share::isEnabled();
// Get all users sharing the file includes current user
$uniqueUserIds = $this->util->getSharingUsersArray($sharingEnabled, $this->relPath);
$checkedUserIds = $this->util->filterShareReadyUsers($uniqueUserIds);
// Fetch public keys for all sharing users
$publicKeys = Keymanager::getPublicKeys($this->rootView, $checkedUserIds['ready']);
// Encrypt enc key for all sharing users
$this->encKeyfiles = Crypt::multiKeyEncrypt($this->plainKey, $publicKeys);
// Save the new encrypted file key
Keymanager::setFileKey($this->rootView, $this->util, $this->relPath, $this->encKeyfiles['data']);
// Save the sharekeys
Keymanager::setShareKeys($this->rootView, $this->util, $this->relPath, $this->encKeyfiles['keys']);
// Re-enable proxy - our work is done
\OC_FileProxy::$enabled = $proxyStatus;
}
// we need to update the file info for the real file, not for the
// part file.
$path = Helper::stripPartialFileExtension($this->rawPath);
$fileInfo = array(
'mimetype' => $this->rootView->getMimeType($this->rawPath),
'encrypted' => true,
'unencrypted_size' => $this->unencryptedSize,
);
// if we write a part file we also store the unencrypted size for
// the part file so that it can be re-used later
$this->rootView->putFileInfo($this->rawPath, $fileInfo);
if ($path !== $this->rawPath) {
$this->rootView->putFileInfo($path, $fileInfo);
}
}
$result = fclose($this->handle);
if ($result === false) {
\OCP\Util::writeLog('Encryption library', 'Could not close stream, file could be corrupted', \OCP\Util::FATAL);
}
return $result;
}
}