implement basic encryption functionallity in core to enable multiple encryption modules

1 files changed, 385 insertions, 0 deletions

diff --git a/lib/private/files/stream/encryption.php b/lib/private/files/stream/encryption.php
new file mode 100644
index 00000000000..ddef9067bad
--- /dev/null
+++ b/lib/private/files/stream/encryption.php
@@ -0,0 +1,385 @@
+<?php
+
+/**
+ * ownCloud - Encryption stream wrapper
+ *
+ * @copyright (C) 2015 ownCloud, Inc.
+ *
+ * @author Bjoern Schiessle <schiessle@owncloud.com>
+ *
+ * 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 <http://www.gnu.org/licenses/>.
+ */
+
+namespace OC\Files\Stream;
+
+use Icewind\Streams\Wrapper;
+use OC\Encryption\Exceptions\EncryptionHeaderKeyExistsException;
+
+class Encryption extends Wrapper {
+
+	/** @var \OC\Encryption\Util */
+	protected $util;
+
+	/** @var \OCP\Encryption\IEncryptionModule */
+	protected $encryptionModule;
+
+	/** @var \OC\Files\Storage\Storage */
+	protected $storage;
+
+	/** @var \OC\Files\Storage\Wrapper\Encryption */
+	protected $encryptionStorage;
+
+	/** @var string */
+	protected $internalPath;
+
+	/** @var integer */
+	protected $size;
+
+	/** @var integer */
+	protected $position;
+
+	/** @var integer */
+	protected $unencryptedSize;
+
+	/** @var integer */
+	protected $unencryptedBlockSize;
+
+	/** @var array */
+	protected $header;
+
+	/** @var string */
+	protected $fullPath;
+
+	/**
+	 * header data returned by the encryption module, will be written to the file
+	 * in case of a write operation
+	 *
+	 * @var array
+	 */
+	protected $newHeader;
+
+	/**
+	 * user who perform the read/write operation null for public access
+	 *
+	 *  @var string
+	 */
+	protected $uid;
+
+	/** @var bool */
+	protected $readOnly;
+
+	/** @var array */
+	protected $expectedContextProperties;
+
+	public function __construct() {
+		$this->expectedContextProperties = array(
+			'source',
+			'storage',
+			'internalPath',
+			'fullPath',
+			'encryptionModule',
+			'header',
+			'uid',
+			'util',
+			'size',
+			'unencryptedSize',
+			'encryptionStorage'
+		);
+	}
+
+
+	/**
+	 * Wraps a stream with the provided callbacks
+	 *
+	 * @param resource $source
+	 * @param string $internalPath relative to mount point
+	 * @param string $fullPath relative to data/
+	 * @param array $header
+	 * @param sting $uid
+	 * @param \OCP\Encryption\IEncryptionModule $encryptionModule
+	 * @param \OC\Files\Storage\Storage $storage
+	 * @param OC\Files\Storage\Wrapper\Encryption $encStorage
+	 * @param \OC\Encryption\Util $util
+	 * @param string $mode
+	 * @param int $size
+	 * @param int $unencryptedSize
+	 * @return resource
+	 *
+	 * @throws \BadMethodCallException
+	 */
+	public static function wrap($source, $internalPath, $fullPath, array $header,
+		$uid, \OCP\Encryption\IEncryptionModule $encryptionModule,
+		\OC\Files\Storage\Storage $storage, \OC\Files\Storage\Wrapper\Encryption $encStorage,
+		\OC\Encryption\Util $util, $mode, $size, $unencryptedSize) {
+
+		$context = stream_context_create(array(
+			'ocencryption' => array(
+				'source' => $source,
+				'storage' => $storage,
+				'internalPath' => $internalPath,
+				'fullPath' => $fullPath,
+				'encryptionModule' => $encryptionModule,
+				'header' => $header,
+				'uid' => $uid,
+				'util' => $util,
+				'size' => $size,
+				'unencryptedSize' => $unencryptedSize,
+				'encryptionStorage' => $encStorage
+			)
+		));
+
+		return self::wrapSource($source, $mode, $context, 'ocencryption', 'OC\Files\Stream\Encryption');
+	}
+
+	/**
+	 * add stream wrapper
+	 *
+	 * @param resource $source
+	 * @param string $mode
+	 * @param array $context
+	 * @param string $protocol
+	 * @param string $class
+	 * @return resource
+	 * @throws \BadMethodCallException
+	 */
+	protected static function wrapSource($source, $mode, $context, $protocol, $class) {
+		try {
+			stream_wrapper_register($protocol, $class);
+			if (@rewinddir($source) === false) {
+				$wrapped = fopen($protocol . '://', $mode, false, $context);
+			} else {
+				$wrapped = opendir($protocol . '://', $context);
+			}
+		} catch (\BadMethodCallException $e) {
+			stream_wrapper_unregister($protocol);
+			throw $e;
+		}
+		stream_wrapper_unregister($protocol);
+		return $wrapped;
+	}
+
+	/**
+	 * Load the source from the stream context and return the context options
+	 *
+	 * @param string $name
+	 * @return array
+	 * @throws \BadMethodCallException
+	 */
+	protected function loadContext($name) {
+		$context = parent::loadContext($name);
+
+		foreach ($this->expectedContextProperties as $property) {
+			if (isset($context[$property])) {
+				$this->{$property} = $context[$property];
+			} else {
+				throw new \BadMethodCallException('Invalid context, "' . $property . '" options not set');
+			}
+		}
+		return $context;
+
+	}
+
+	public function stream_open($path, $mode, $options, &$opened_path) {
+		$this->loadContext('ocencryption');
+
+		$this->position = 0;
+		$this->unencryptedBlockSize = $this->encryptionModule->getUnencryptedBlockSize();
+
+		if (
+			$mode === 'w'
+			|| $mode === 'w+'
+			|| $mode === 'wb'
+			|| $mode === 'wb+'
+		) {
+			// We're writing a new file so start write counter with 0 bytes
+			// TODO can we remove this completely?
+			//$this->unencryptedSize = 0;
+			//$this->size = 0;
+			$this->readOnly = false;
+		} else {
+			$this->readOnly = true;
+		}
+
+		$sharePath = $this->fullPath;
+		if (!$this->storage->file_exists($this->internalPath)) {
+			$sharePath = dirname($path);
+		}
+
+		$accessList = $this->util->getSharingUsersArray($sharePath);
+		$this->newHeader = $this->encryptionModule->begin($this->fullPath, $this->uid, $this->header, $accessList);
+
+		return true;
+
+	}
+
+	public function stream_read($count) {
+
+		$result = '';
+
+		// skip the header if we read the file from the beginning
+		if ($this->position === 0 && !empty($this->header)) {
+			parent::stream_read($this->util->getBlockSize());
+		}
+
+		while ($count > 0) {
+			$remainingLength = $count;
+			// update the cache of the current block
+			$data = parent::stream_read($this->util->getBlockSize());
+			$decrypted = $this->encryptionModule->decrypt($data);
+			// determine the relative position in the current block
+			$blockPosition = ($this->position % $this->unencryptedBlockSize);
+			// if entire read inside current block then only position needs to be updated
+			if ($remainingLength < ($this->unencryptedBlockSize - $blockPosition)) {
+				$result .= substr($decrypted, $blockPosition, $remainingLength);
+				$this->position += $remainingLength;
+				$count = 0;
+			// otherwise remainder of current block is fetched, the block is flushed and the position updated
+			} else {
+				$result .= substr($decrypted, $blockPosition);
+				$this->position += ($this->unencryptedBlockSize - $blockPosition);
+				$count -= ($this->unencryptedBlockSize - $blockPosition);
+			}
+		}
+		return $result;
+
+	}
+
+	public function stream_write($data) {
+
+		if ($this->position === 0) {
+			$this->writeHeader();
+		}
+
+		$length = 0;
+		// loop over $data to fit it in 6126 sized unencrypted blocks
+		while (strlen($data) > 0) {
+			$remainingLength = strlen($data);
+
+			// read current block
+			$currentBlock = parent::stream_read($this->util->getBlockSize());
+			$decrypted = $this->encryptionModule->decrypt($currentBlock, $this->uid);
+
+			// 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
+			$positionInFile = floor($this->position / $this->unencryptedBlockSize) *
+				$this->util->getBlockSize() + $this->util->getHeaderSize();
+			$resultFseek = parent::stream_seek($positionInFile);
+
+			// only allow writes on seekable streams, or at the end of the encrypted stream
+			if ($resultFseek || $positionInFile === $this->size) {
+
+				// determine the relative position in the current block
+				$blockPosition = ($this->position % $this->unencryptedBlockSize);
+				// check if $data fits in current block
+				// if so, overwrite existing data (if any)
+				// update position and liberate $data
+				if ($remainingLength < ($this->unencryptedBlockSize - $blockPosition)) {
+					$decrypted = substr($decrypted, 0, $blockPosition)
+						. $data . substr($decrypted, $blockPosition + $remainingLength);
+					$encrypted = $this->encryptionModule->encrypt($decrypted);
+					parent::stream_write($encrypted);
+					$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 updatedxxx
+				} else {
+					$decrypted = substr($decrypted, 0, $blockPosition) .
+						substr($data, 0, $this->unencryptedBlockSize - $blockPosition);
+					$encrypted = $this->encryptionModule->encrypt($decrypted);
+					parent::stream_write($encrypted);
+					$this->position += ($this->unencryptedBlockSize - $blockPosition);
+					$this->size = max($this->size, $this->stream_tell());
+					$length += ($this->unencryptedBlockSize - $blockPosition);
+					$data = substr($data, $this->unencryptedBlockSize - $blockPosition);
+				}
+			} else {
+				$encrypted = $this->encryptionModule->encrypt($data);
+				parent::stream_write($encrypted);
+				$data = '';
+			}
+		}
+		$this->unencryptedSize = max($this->unencryptedSize, $this->position);
+		return $length;
+	}
+
+	public function stream_tell() {
+		return $this->position;
+	}
+
+	public function stream_seek($offset, $whence = SEEK_SET) {
+
+		$return = false;
+
+		switch ($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 / $this->unencryptedBlockSize)
+			* $this->util->getBlockSize() + $this->util->getHeaderSize();
+
+		if (parent::stream_seek($newFilePosition)) {
+			$this->position = $newPosition;
+			$return = true;
+		}
+		return $return;
+
+	}
+
+	public function stream_close() {
+		$this->flush();
+		return parent::stream_close();
+	}
+
+	/**
+	 * tell encryption module that we are done and write remaining data to the file
+	 */
+	protected function flush() {
+		$remainingData = $this->encryptionModule->end($this->fullPath);
+		if ($this->readOnly === false) {
+			if(!empty($remainingData)) {
+				parent::stream_write($remainingData);
+			}
+			$this->encryptionStorage->updateUnencryptedSize($this->fullPath, $this->unencryptedSize);
+		}
+	}
+
+
+	/**
+	 * write header at beginning of encrypted file
+	 *
+	 * @throws EncryptionHeaderKeyExistsException if header key is already in use
+	 */
+	private function writeHeader() {
+		$header = $this->util->createHeader($this->newHeader, $this->encryptionModule);
+		parent::stream_write($header);
+	}
+
+}