nextcloud/apps/files_encryption/lib/proxy.php

<?php

/**
 * ownCloud
 *
 * @author Sam Tuke, Robin Appelman
 * @copyright 2012 Sam Tuke samtuke@owncloud.com, Robin Appelman
 * icewind1991@gmail.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/>.
 *
 */

/**
 * @brief Encryption proxy which handles filesystem operations before and after
 *        execution and encrypts, and handles keyfiles accordingly. Used for
 *        webui.
 */

namespace OCA\Encryption;

/**
 * Class Proxy
 * @package OCA\Encryption
 */
class Proxy extends \OC_FileProxy
{

	private static $blackList = null; //mimetypes blacklisted from encryption

	private static $enableEncryption = null;

	/**
	 * Check if a file requires encryption
	 * @param string $path
	 * @return bool
	 *
	 * Tests if server side encryption is enabled, and file is allowed by blacklists
	 */
	private static function shouldEncrypt( $path ) {

		if ( is_null( self::$enableEncryption ) ) {

			if (
				\OCP\Config::getAppValue( 'files_encryption', 'enable_encryption', 'true' ) == 'true'
				&& Crypt::mode() == 'server'
			) {

				self::$enableEncryption = true;

			} else {

				self::$enableEncryption = false;

			}

		}

		if ( !self::$enableEncryption ) {

			return false;

		}

		if ( is_null( self::$blackList ) ) {

			self::$blackList = explode( ',', \OCP\Config::getAppValue( 'files_encryption', 'type_blacklist', '' ) );

		}

		if ( Crypt::isCatfileContent( $path ) ) {

			return true;

		}

		$extension = substr( $path, strrpos( $path, '.' ) + 1 );

		if ( array_search( $extension, self::$blackList ) === false ) {

			return true;

		}

		return false;
	}

	/**
	 * @param $path
	 * @param $data
	 * @return bool
	 */
	public function preFile_put_contents( $path, &$data ) {

		if ( self::shouldEncrypt( $path ) ) {

			// Stream put contents should have been converted to fopen
			if ( !is_resource( $data ) ) {

				$userId = \OCP\USER::getUser();
				$view = new \OC_FilesystemView( '/' );
				$util = new Util( $view, $userId );
				$session = new Session( $view );
				$privateKey = $session->getPrivateKey();
				$filePath = $util->stripUserFilesPath( $path );
				// Set the filesize for userland, before encrypting
				$size = strlen( $data );

				// Disable encryption proxy to prevent recursive calls
				$proxyStatus = \OC_FileProxy::$enabled;
				\OC_FileProxy::$enabled = false;

				// Check if there is an existing key we can reuse
				if ( $encKeyfile = Keymanager::getFileKey( $view, $userId, $filePath ) ) {

					// Fetch shareKey
					$shareKey = Keymanager::getShareKey( $view, $userId, $filePath );

					// Decrypt the keyfile
					$plainKey = Crypt::multiKeyDecrypt( $encKeyfile, $shareKey, $privateKey );

				} else {

					// Make a new key
					$plainKey = Crypt::generateKey();

				}

				// Encrypt data
				$encData = Crypt::symmetricEncryptFileContent( $data, $plainKey );

				$sharingEnabled = \OCP\Share::isEnabled();

				// if file exists try to get sharing users
				if ( $view->file_exists( $path ) ) {
					$uniqueUserIds = $util->getSharingUsersArray( $sharingEnabled, $filePath, $userId );
				} else {
					$uniqueUserIds[] = $userId;
				}

				// Fetch public keys for all users who will share the file
				$publicKeys = Keymanager::getPublicKeys( $view, $uniqueUserIds );

				// Encrypt plain keyfile to multiple sharefiles
				$multiEncrypted = Crypt::multiKeyEncrypt( $plainKey, $publicKeys );

				// Save sharekeys to user folders
				Keymanager::setShareKeys( $view, $filePath, $multiEncrypted['keys'] );

				// Set encrypted keyfile as common varname
				$encKey = $multiEncrypted['data'];

				// Save keyfile for newly encrypted file in parallel directory tree
				Keymanager::setFileKey( $view, $filePath, $userId, $encKey );

				// Replace plain content with encrypted content by reference
				$data = $encData;

				// Update the file cache with file info
				\OC\Files\Filesystem::putFileInfo( $filePath, array( 'encrypted' => true, 'size' => strlen( $data ), 'unencrypted_size' => $size ), '' );

				// Re-enable proxy - our work is done
				\OC_FileProxy::$enabled = $proxyStatus;

			}
		}

		return true;

	}

	/**
	 * @param string $path Path of file from which has been read
	 * @param string $data Data that has been read from file
	 */
	public function postFile_get_contents( $path, $data ) {

		$userId = \OCP\USER::getUser();
		$view = new \OC_FilesystemView( '/' );
		$util = new Util( $view, $userId );

		$relPath = $util->stripUserFilesPath( $path );

		// Disable encryption proxy to prevent recursive calls
		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		// init session
		$session = new Session( $view );

		// If data is a catfile
		if (
			Crypt::mode() == 'server'
			&& Crypt::isCatfileContent( $data )
		) {

			$privateKey = $session->getPrivateKey( $userId );

			// Get the encrypted keyfile
			$encKeyfile = Keymanager::getFileKey( $view, $userId, $relPath );

			// Attempt to fetch the user's shareKey
			$shareKey = Keymanager::getShareKey( $view, $userId, $relPath );

			// Decrypt keyfile with shareKey
			$plainKeyfile = Crypt::multiKeyDecrypt( $encKeyfile, $shareKey, $privateKey );

			$plainData = Crypt::symmetricDecryptFileContent( $data, $plainKeyfile );

		} elseif (
			Crypt::mode() == 'server'
			&& isset( $_SESSION['legacyenckey'] )
			&& Crypt::isEncryptedMeta( $path )
		) {
			$plainData = Crypt::legacyDecrypt( $data, $session->getLegacyKey() );
		}

		\OC_FileProxy::$enabled = $proxyStatus;

		if ( !isset( $plainData ) ) {

			$plainData = $data;

		}

		return $plainData;

	}

	/**
	 * @brief When a file is deleted, remove its keyfile also
	 */
	public function preUnlink( $path ) {

		// let the trashbin handle this  
		if ( \OCP\App::isEnabled( 'files_trashbin' ) ) {
			return true;
		}

		// Disable encryption proxy to prevent recursive calls
		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		$view = new \OC_FilesystemView( '/' );

		$userId = \OCP\USER::getUser();

		$util = new Util( $view, $userId );

		// Format path to be relative to user files dir
		$relPath = $util->stripUserFilesPath( $path );

		list( $owner, $ownerPath ) = $util->getUidAndFilename( $relPath );

		// Delete keyfile & shareKey so it isn't orphaned
		if ( !Keymanager::deleteFileKey( $view, $owner, $ownerPath ) ) {
			\OC_Log::write( 'Encryption library', 'Keyfile or shareKey could not be deleted for file "' . $ownerPath . '"', \OC_Log::ERROR );
		}

		Keymanager::delAllShareKeys( $view, $owner, $ownerPath );

		\OC_FileProxy::$enabled = $proxyStatus;

		// If we don't return true then file delete will fail; better
		// to leave orphaned keyfiles than to disallow file deletion
		return true;

	}

	/**
	 * @param $path
	 * @return bool
	 */
	public function postTouch( $path ) {
		$this->handleFile( $path );

		return true;
	}

	/**
	 * @param $path
	 * @param $result
	 * @return resource
	 */
	public function postFopen( $path, &$result ) {

		if ( !$result ) {

			return $result;

		}

		// Reformat path for use with OC_FSV
		$path_split = explode( '/', $path );
		$path_f = implode( '/', array_slice( $path_split, 3 ) );

		// FIXME: handling for /userId/cache used by webdav for chunking. The cache chunks are NOT encrypted
		if ( count($path_split) >= 2 && $path_split[2] == 'cache' ) {
			return $result;
		}

		// Disable encryption proxy to prevent recursive calls
		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		$meta = stream_get_meta_data( $result );

		$view = new \OC_FilesystemView( '' );

		$util = new Util( $view, \OCP\USER::getUser() );

		// If file is already encrypted, decrypt using crypto protocol
		if (
			Crypt::mode() == 'server'
			&& $util->isEncryptedPath( $path )
		) {

			// Close the original encrypted file
			fclose( $result );

			// Open the file using the crypto stream wrapper 
			// protocol and let it do the decryption work instead
			$result = fopen( 'crypt://' . $path_f, $meta['mode'] );

		} elseif (
			self::shouldEncrypt( $path )
			and $meta ['mode'] != 'r'
			and $meta['mode'] != 'rb'
		) {
			$result = fopen( 'crypt://' . $path_f, $meta['mode'] );
		}

		// Re-enable the proxy
		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;

	}

	/**
	 * @param $path
	 * @param $data
	 * @return array
	 */
	public function postGetFileInfo( $path, $data ) {

		// if path is a folder do nothing
		if ( is_array( $data ) && array_key_exists( 'size', $data ) ) {

			// Disable encryption proxy to prevent recursive calls
			$proxyStatus = \OC_FileProxy::$enabled;
			\OC_FileProxy::$enabled = false;

			// get file size
			$data['size'] = self::postFileSize( $path, $data['size'] );

			// Re-enable the proxy
			\OC_FileProxy::$enabled = $proxyStatus;
		}

		return $data;
	}

	/**
	 * @param $path
	 * @param $size
	 * @return bool
	 */
	public function postFileSize( $path, $size ) {

		$view = new \OC_FilesystemView( '/' );

		// if path is a folder do nothing
		if ( $view->is_dir( $path ) ) {
			return $size;
		}

		// Reformat path for use with OC_FSV
		$path_split = explode( '/', $path );
		$path_f = implode( '/', array_slice( $path_split, 3 ) );

		// if path is empty we cannot resolve anything
		if ( empty( $path_f ) ) {
			return $size;
		}

		$fileInfo = false;
		// get file info from database/cache if not .part file
		if ( !Keymanager::isPartialFilePath( $path ) ) {
			$fileInfo = $view->getFileInfo( $path );
		}

		// if file is encrypted return real file size
		if ( is_array( $fileInfo ) && $fileInfo['encrypted'] === true ) {
			$size = $fileInfo['unencrypted_size'];
		} else {
			// self healing if file was removed from file cache
			if ( !is_array( $fileInfo ) ) {
				$fileInfo = array();
			}

			$userId = \OCP\User::getUser();
			$util = new Util( $view, $userId );
			$fixSize = $util->getFileSize( $path );
			if ( $fixSize > 0 ) {
				$size = $fixSize;

				$fileInfo['encrypted'] = true;
				$fileInfo['unencrypted_size'] = $size;

				// put file info if not .part file
				if ( !Keymanager::isPartialFilePath( $path_f ) ) {
					$view->putFileInfo( $path, $fileInfo );
				}
			}

		}
		return $size;
	}

	/**
	 * @param $path
	 */
	public function handleFile( $path ) {

		// Disable encryption proxy to prevent recursive calls
		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		$view = new \OC_FilesystemView( '/' );
		$session = new Session( $view );
		$userId = \OCP\User::getUser();
		$util = new Util( $view, $userId );

		// Reformat path for use with OC_FSV
		$path_split = explode( '/', $path );
		$path_f = implode( '/', array_slice( $path_split, 3 ) );

		// only if file is on 'files' folder fix file size and sharing
		if ( count($path_split) >= 2 && $path_split[2] == 'files' && $util->fixFileSize( $path ) ) {

			// get sharing app state
			$sharingEnabled = \OCP\Share::isEnabled();

			// get users
			$usersSharing = $util->getSharingUsersArray( $sharingEnabled, $path_f );

			// update sharing-keys
			$util->setSharedFileKeyfiles( $session, $usersSharing, $path_f );
		}

		\OC_FileProxy::$enabled = $proxyStatus;
	}
}