nextcloud/apps/files_encryption/lib/util.php

<?php
/**
 * ownCloud
 *
 * @author Sam Tuke, Frank Karlitschek
 * @copyright 2012 Sam Tuke <samtuke@owncloud.com>,
 * Frank Karlitschek <frank@owncloud.org>
 *
 * 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/>.
 *
 */

# Bugs
# ----
# Sharing a file to a user without encryption set up will not provide them with access but won't notify the sharer
# Sharing all files to admin for recovery purposes still in progress
# Possibly public links are broken (not tested since last merge of master)


# Missing features
# ----------------
# Make sure user knows if large files weren't encrypted


# Test
# ----
# Test that writing files works when recovery is enabled, and sharing API is disabled
# Test trashbin support


// Old Todo:
//  - Crypt/decrypt button in the userinterface
//  - Setting if crypto should be on by default
//  - Add a setting "Don´t encrypt files larger than xx because of performance 
//    reasons"

namespace OCA\Encryption;

/**
 * @brief Class for utilities relating to encrypted file storage system
 * @param OC_FilesystemView $view expected to have OC '/' as root path
 * @param string $userId ID of the logged in user
 * @param int $client indicating status of client side encryption. Currently
 * unused, likely to become obsolete shortly
 */

class Util
{

	// Web UI:

	//// DONE: files created via web ui are encrypted
	//// DONE: file created & encrypted via web ui are readable in web ui
	//// DONE: file created & encrypted via web ui are readable via webdav


	// WebDAV:

	//// DONE: new data filled files added via webdav get encrypted
	//// DONE: new data filled files added via webdav are readable via webdav
	//// DONE: reading unencrypted files when encryption is enabled works via 
	////       webdav
	//// DONE: files created & encrypted via web ui are readable via webdav


	// Legacy support:

	//// DONE: add method to check if file is encrypted using new system
	//// DONE: add method to check if file is encrypted using old system
	//// DONE: add method to fetch legacy key
	//// DONE: add method to decrypt legacy encrypted data


	// Admin UI:

	//// DONE: changing user password also changes encryption passphrase

	//// TODO: add support for optional recovery in case of lost passphrase / keys
	//// TODO: add admin optional required long passphrase for users
	//// TODO: implement flag system to allow user to specify encryption by folder, subfolder, etc.


	// Integration testing:

	//// TODO: test new encryption with versioning
	//// DONE: test new encryption with sharing
	//// TODO: test new encryption with proxies


	private $view; // OC_FilesystemView object for filesystem operations
	private $userId; // ID of the currently logged-in user
	private $pwd; // User Password
	private $client; // Client side encryption mode flag
	private $publicKeyDir; // Dir containing all public user keys
	private $encryptionDir; // Dir containing user's files_encryption
	private $keyfilesPath; // Dir containing user's keyfiles
	private $shareKeysPath; // Dir containing env keys for shared files
	private $publicKeyPath; // Path to user's public key
	private $privateKeyPath; // Path to user's private key
	private $publicShareKeyId;
	private $recoveryKeyId;
	private $isPublic;

	/**
	 * @param \OC_FilesystemView $view
	 * @param $userId
	 * @param bool $client
	 */
	public function __construct( \OC_FilesystemView $view, $userId, $client = false ) {

		$this->view = $view;
		$this->userId = $userId;
		$this->client = $client;
		$this->isPublic = false;

		$this->publicShareKeyId = \OC_Appconfig::getValue( 'files_encryption', 'publicShareKeyId' );
		$this->recoveryKeyId = \OC_Appconfig::getValue( 'files_encryption', 'recoveryKeyId' );

		// if we are anonymous/public
		if ( $this->userId === false ||
			( isset( $_GET['service'] ) && $_GET['service'] == 'files' &&
				isset( $_GET['t'] ) )
		) {
			$this->userId = $this->publicShareKeyId;

			// only handle for files_sharing app
			if ( $GLOBALS['app'] === 'files_sharing' ) {
				$this->userDir = '/' . $GLOBALS['fileOwner'];
				$this->fileFolderName = 'files';
				$this->userFilesDir = '/' . $GLOBALS['fileOwner'] . '/' . $this->fileFolderName; // TODO: Does this need to be user configurable?
				$this->publicKeyDir = '/' . 'public-keys';
				$this->encryptionDir = '/' . $GLOBALS['fileOwner'] . '/' . 'files_encryption';
				$this->keyfilesPath = $this->encryptionDir . '/' . 'keyfiles';
				$this->shareKeysPath = $this->encryptionDir . '/' . 'share-keys';
				$this->publicKeyPath = $this->publicKeyDir . '/' . $this->userId . '.public.key'; // e.g. data/public-keys/admin.public.key
				$this->privateKeyPath = '/owncloud_private_key/' . $this->userId . '.private.key'; // e.g. data/admin/admin.private.key
				$this->isPublic = true;
			}

		} else {
			$this->userDir = '/' . $this->userId;
			$this->fileFolderName = 'files';
			$this->userFilesDir = '/' . $this->userId . '/' . $this->fileFolderName; // TODO: Does this need to be user configurable?
			$this->publicKeyDir = '/' . 'public-keys';
			$this->encryptionDir = '/' . $this->userId . '/' . 'files_encryption';
			$this->keyfilesPath = $this->encryptionDir . '/' . 'keyfiles';
			$this->shareKeysPath = $this->encryptionDir . '/' . 'share-keys';
			$this->publicKeyPath = $this->publicKeyDir . '/' . $this->userId . '.public.key'; // e.g. data/public-keys/admin.public.key
			$this->privateKeyPath = $this->encryptionDir . '/' . $this->userId . '.private.key'; // e.g. data/admin/admin.private.key
		}
	}

	/**
	 * @return bool
	 */
	public function ready() {

		if (
			!$this->view->file_exists( $this->encryptionDir )
			or !$this->view->file_exists( $this->keyfilesPath )
			or !$this->view->file_exists( $this->shareKeysPath )
			or !$this->view->file_exists( $this->publicKeyPath )
			or !$this->view->file_exists( $this->privateKeyPath )
		) {

			return false;

		} else {

			return true;

		}

	}

	/**
	 * @brief Sets up user folders and keys for serverside encryption
	 * @param string $passphrase passphrase to encrypt server-stored private key with
	 */
	public function setupServerSide( $passphrase = null ) {

		// Set directories to check / create
		$setUpDirs = array(
			$this->userDir
		, $this->userFilesDir
		, $this->publicKeyDir
		, $this->encryptionDir
		, $this->keyfilesPath
		, $this->shareKeysPath
		);

		// Check / create all necessary dirs
		foreach ( $setUpDirs as $dirPath ) {

			if ( !$this->view->file_exists( $dirPath ) ) {

				$this->view->mkdir( $dirPath );

			}

		}

		// Create user keypair
		// we should never override a keyfile
		if (
			!$this->view->file_exists( $this->publicKeyPath )
			&& !$this->view->file_exists( $this->privateKeyPath )
		) {

			// Generate keypair
			$keypair = Crypt::createKeypair();

			\OC_FileProxy::$enabled = false;

			// Save public key
			$this->view->file_put_contents( $this->publicKeyPath, $keypair['publicKey'] );

			// Encrypt private key with user pwd as passphrase
			$encryptedPrivateKey = Crypt::symmetricEncryptFileContent( $keypair['privateKey'], $passphrase );

			// Save private key
			$this->view->file_put_contents( $this->privateKeyPath, $encryptedPrivateKey );

			\OC_FileProxy::$enabled = true;

		} else {
			// check if public-key exists but private-key is missing
			if ( $this->view->file_exists( $this->publicKeyPath ) && !$this->view->file_exists( $this->privateKeyPath ) ) {
				\OC_Log::write( 'Encryption library', 'public key exists but private key is missing for "' . $this->userId . '"', \OC_Log::FATAL );
				return false;
			} else if ( !$this->view->file_exists( $this->publicKeyPath ) && $this->view->file_exists( $this->privateKeyPath ) ) {
				\OC_Log::write( 'Encryption library', 'private key exists but public key is missing for "' . $this->userId . '"', \OC_Log::FATAL );
				return false;
			}
		}

		// If there's no record for this user's encryption preferences
		if ( false === $this->recoveryEnabledForUser() ) {

			// create database configuration
			$sql = 'INSERT INTO `*PREFIX*encryption` (`uid`,`mode`,`recovery_enabled`) VALUES (?,?,?)';
			$args = array( $this->userId, 'server-side', 0 );
			$query = \OCP\DB::prepare( $sql );
			$query->execute( $args );

		}

		return true;

	}

	/**
	 * @return string
	 */
	public function getPublicShareKeyId() {
		return $this->publicShareKeyId;
	}

	/**
	 * @brief Check whether pwd recovery is enabled for a given user
	 * @return bool 1 = yes, 0 = no, false = no record
	 *
	 * @note If records are not being returned, check for a hidden space
	 *       at the start of the uid in db
	 */
	public function recoveryEnabledForUser() {

		$sql = 'SELECT 
				recovery_enabled
			FROM 
				`*PREFIX*encryption` 
			WHERE 
				uid = ?';

		$args = array( $this->userId );

		$query = \OCP\DB::prepare( $sql );

		$result = $query->execute( $args );

		$recoveryEnabled = array();

		while ( $row = $result->fetchRow() ) {

			$recoveryEnabled[] = $row['recovery_enabled'];

		}

		// If no record is found
		if ( empty( $recoveryEnabled ) ) {

			return false;

			// If a record is found
		} else {

			return $recoveryEnabled[0];

		}

	}

	/**
	 * @brief Enable / disable pwd recovery for a given user
	 * @param bool $enabled Whether to enable or disable recovery
	 * @return bool
	 */
	public function setRecoveryForUser( $enabled ) {

		$recoveryStatus = $this->recoveryEnabledForUser();

		// If a record for this user already exists, update it
		if ( false === $recoveryStatus ) {

			$sql = 'INSERT INTO `*PREFIX*encryption` 
					(`uid`,`mode`,`recovery_enabled`)
				VALUES (?,?,?)';

			$args = array( $this->userId, 'server-side', $enabled );

			// Create a new record instead
		} else {

			$sql = 'UPDATE 
					*PREFIX*encryption 
				SET 
					recovery_enabled = ?
				WHERE 
					uid = ?';

			$args = array( $enabled, $this->userId );

		}

		$query = \OCP\DB::prepare( $sql );

		if ( $query->execute( $args ) ) {

			return true;

		} else {

			return false;

		}

	}

	/**
	 * @brief Find all files and their encryption status within a directory
	 * @param string $directory The path of the parent directory to search
	 * @return mixed false if 0 found, array on success. Keys: name, path
	 * @note $directory needs to be a path relative to OC data dir. e.g.
	 *       /admin/files NOT /backup OR /home/www/oc/data/admin/files
	 */
	public function findEncFiles( $directory, &$found = false ) {

		// Disable proxy - we don't want files to be decrypted before
		// we handle them
		\OC_FileProxy::$enabled = false;

		if ( $found == false ) {
			$found = array( 'plain' => array(), 'encrypted' => array(), 'legacy' => array() );
		}

		if (
			$this->view->is_dir( $directory )
			&& $handle = $this->view->opendir( $directory )
		) {

			while ( false !== ( $file = readdir( $handle ) ) ) {

				if (
					$file != "."
					&& $file != ".."
				) {

					$filePath = $directory . '/' . $this->view->getRelativePath( '/' . $file );
					$relPath = $this->stripUserFilesPath( $filePath );

					// If the path is a directory, search 
					// its contents
					if ( $this->view->is_dir( $filePath ) ) {

						$this->findEncFiles( $filePath, $found );

						// If the path is a file, determine
						// its encryption status
					} elseif ( $this->view->is_file( $filePath ) ) {

						// Disable proxies again, some-
						// where they got re-enabled :/
						\OC_FileProxy::$enabled = false;

						$data = $this->view->file_get_contents( $filePath );

						// If the file is encrypted
						// NOTE: If the userId is 
						// empty or not set, file will 
						// detected as plain
						// NOTE: This is inefficient;
						// scanning every file like this
						// will eat server resources :(
						if (
							Keymanager::getFileKey( $this->view, $this->userId, $relPath )
							&& Crypt::isCatfileContent( $data )
						) {

							$found['encrypted'][] = array( 'name' => $file, 'path' => $filePath );

							// If the file uses old
							// encryption system
						} elseif ( Crypt::isLegacyEncryptedContent( $data, $relPath ) ) {

							$found['legacy'][] = array( 'name' => $file, 'path' => $filePath );

							// If the file is not encrypted
						} else {

							$found['plain'][] = array( 'name' => $file, 'path' => $relPath );

						}

					}

				}

			}

			\OC_FileProxy::$enabled = true;

			if ( empty( $found ) ) {

				return false;

			} else {

				return $found;

			}

		}

		\OC_FileProxy::$enabled = true;

		return false;

	}

	/**
	 * @brief Fetch the last lines of a file efficiently
	 * @note Safe to use on large files; does not read entire file to memory
	 * @note Derivative of http://tekkie.flashbit.net/php/tail-functionality-in-php
	 */
	public function tail( $filename, $numLines ) {

		\OC_FileProxy::$enabled = false;

		$text = '';
		$pos = -1;
		$handle = $this->view->fopen( $filename, 'r' );

		while ( $numLines > 0 ) {

			--$pos;

			if ( fseek( $handle, $pos, SEEK_END ) !== 0 ) {

				rewind( $handle );
				$numLines = 0;

			} elseif ( fgetc( $handle ) === "\n" ) {

				--$numLines;

			}

			$block_size = ( -$pos ) % 8192;
			if ( $block_size === 0 || $numLines === 0 ) {

				$text = fread( $handle, ( $block_size === 0 ? 8192 : $block_size ) ) . $text;

			}
		}

		fclose( $handle );

		\OC_FileProxy::$enabled = true;

		return $text;
	}

	/**
	 * @brief Check if a given path identifies an encrypted file
	 * @param $path
	 * @return boolean
	 */
	public function isEncryptedPath( $path ) {

		// Disable encryption proxy so data retrieved is in its
		// original form
		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		// we only need 24 byte from the last chunk
		$data = '';
		$handle = $this->view->fopen( $path, 'r' );
		if ( !fseek( $handle, -24, SEEK_END ) ) {
			$data = fgets( $handle );
		}

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

		return Crypt::isCatfileContent( $data );

	}

	/**
	 * @brief get the file size of the unencrypted file
	 * @param string $path absolute path
	 * @return bool
	 */
	public function getFileSize( $path ) {

		$result = 0;

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

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

		if ( $pathSplit[2] == 'files' && $this->view->file_exists( $path ) && $this->isEncryptedPath( $path ) ) {

			// get the size from filesystem
			$fullPath = $this->view->getLocalFile( $path );
			$size = filesize( $fullPath );

			// calculate last chunk nr
			$lastChunkNr = floor( $size / 8192 );

			// open stream
			$stream = fopen( 'crypt://' . $pathRelative, "r" );

			if ( is_resource( $stream ) ) {
				// calculate last chunk position
				$lastChunckPos = ( $lastChunkNr * 8192 );

				// seek to end
				fseek( $stream, $lastChunckPos );

				// get the content of the last chunk
				$lastChunkContent = fread( $stream, 8192 );

				// calc the real file size with the size of the last chunk
				$realSize = ( ( $lastChunkNr * 6126 ) + strlen( $lastChunkContent ) );

				// store file size
				$result = $realSize;
			}
		}

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;
	}

	/**
	 * @brief fix the file size of the encrypted file
	 * @param $path absolute path
	 * @return true / false if file is encrypted
	 */
	public function fixFileSize( $path ) {

		$result = false;

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

		$realSize = $this->getFileSize( $path );

		if ( $realSize > 0 ) {

			$cached = $this->view->getFileInfo( $path );
			$cached['encrypted'] = true;

			// set the size
			$cached['unencrypted_size'] = $realSize;

			// put file info
			$this->view->putFileInfo( $path, $cached );

			$result = true;

		}

		\OC_FileProxy::$enabled = $proxyStatus;

		return $result;
	}

	/**
	 * @brief Format a path to be relative to the /user/files/ directory
	 * @note e.g. turns '/admin/files/test.txt' into 'test.txt'
	 */
	public function stripUserFilesPath( $path ) {

		$trimmed = ltrim( $path, '/' );
		$split = explode( '/', $trimmed );
		$sliced = array_slice( $split, 2 );
		$relPath = implode( '/', $sliced );

		return $relPath;

	}

	/**
	 * @param $path
	 * @return bool
	 */
	public function isSharedPath( $path ) {

		$trimmed = ltrim( $path, '/' );
		$split = explode( '/', $trimmed );

		if ( $split[2] == "Shared" ) {

			return true;

		} else {

			return false;

		}

	}

	/**
	 * @brief Encrypt all files in a directory
	 * @param string $dirPath the directory whose files will be encrypted
	 * @param null $legacyPassphrase
	 * @param null $newPassphrase
	 * @return bool
	 * @note Encryption is recursive
	 */
	public function encryptAll( $dirPath, $legacyPassphrase = null, $newPassphrase = null ) {

		if ( $found = $this->findEncFiles( $dirPath ) ) {

			// Disable proxy to prevent file being encrypted twice
			\OC_FileProxy::$enabled = false;

			// Encrypt unencrypted files
			foreach ( $found['plain'] as $plainFile ) {

				//relative to data/<user>/file
				$relPath = $plainFile['path'];

				//relative to /data
				$rawPath = '/'.$this->userId . '/files/' . $plainFile['path'];

				// Open plain file handle for binary reading
				$plainHandle = $this->view->fopen( $rawPath, 'rb' );

				// Open enc file handle for binary writing, with same filename as original plain file
				$encHandle = fopen( 'crypt://' . $relPath.'.tmp', 'wb' );

				// Move plain file to a temporary location
				$size = stream_copy_to_stream( $plainHandle, $encHandle );

				fclose($encHandle);

				$fakeRoot = $this->view->getRoot();
				$this->view->chroot('/'.$this->userId.'/files');

				$this->view->rename($relPath . '.tmp', $relPath);

				$this->view->chroot($fakeRoot);

				// Add the file to the cache
				\OC\Files\Filesystem::putFileInfo( $relPath, array( 'encrypted' => true, 'size' => $size, 'unencrypted_size' => $size ) );
			}

			// Encrypt legacy encrypted files
			if (
				!empty( $legacyPassphrase )
				&& !empty( $newPassphrase )
			) {

				foreach ( $found['legacy'] as $legacyFile ) {

					// Fetch data from file
					$legacyData = $this->view->file_get_contents( $legacyFile['path'] );

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

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

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

					// Recrypt data, generate catfile
					$recrypted = Crypt::legacyKeyRecryptKeyfile( $legacyData, $legacyPassphrase, $publicKeys, $newPassphrase, $legacyFile['path'] );

					$rawPath = $legacyFile['path'];
					$relPath = $this->stripUserFilesPath( $rawPath );

					// Save keyfile
					Keymanager::setFileKey( $this->view, $relPath, $this->userId, $recrypted['filekey'] );

					// Save sharekeys to user folders
					Keymanager::setShareKeys( $this->view, $relPath, $recrypted['sharekeys'] );

					// Overwrite the existing file with the encrypted one
					$this->view->file_put_contents( $rawPath, $recrypted['data'] );

					$size = strlen( $recrypted['data'] );

					// Add the file to the cache
					\OC\Files\Filesystem::putFileInfo( $rawPath, array( 'encrypted' => true, 'size' => $size ), '' );
				}
			}

			\OC_FileProxy::$enabled = true;

			// If files were found, return true
			return true;
		} else {

			// If no files were found, return false
			return false;
		}
	}

	/**
	 * @brief Return important encryption related paths
	 * @param string $pathName Name of the directory to return the path of
	 * @return string path
	 */
	public function getPath( $pathName ) {

		switch ( $pathName ) {

			case 'publicKeyDir':

				return $this->publicKeyDir;

				break;

			case 'encryptionDir':

				return $this->encryptionDir;

				break;

			case 'keyfilesPath':

				return $this->keyfilesPath;

				break;

			case 'publicKeyPath':

				return $this->publicKeyPath;

				break;

			case 'privateKeyPath':

				return $this->privateKeyPath;

				break;
		}

		return false;

	}

	/**
	 * @brief get path of a file.
	 * @param int $fileId id of the file
	 * @return string path of the file
	 */
	public static function fileIdToPath( $fileId ) {

		$query = \OC_DB::prepare( 'SELECT `path`'
			. ' FROM `*PREFIX*filecache`'
			. ' WHERE `fileid` = ?' );

		$result = $query->execute( array( $fileId ) );

		$row = $result->fetchRow();

		return substr( $row['path'], 5 );

	}

	/**
	 * @brief Filter an array of UIDs to return only ones ready for sharing
	 * @param array $unfilteredUsers users to be checked for sharing readiness
	 * @return multi-dimensional array. keys: ready, unready
	 */
	public function filterShareReadyUsers( $unfilteredUsers ) {

		// This array will collect the filtered IDs
		$readyIds = $unreadyIds = array();

		// Loop through users and create array of UIDs that need new keyfiles
		foreach ( $unfilteredUsers as $user ) {

			$util = new Util( $this->view, $user );

			// Check that the user is encryption capable, or is the
			// public system user 'ownCloud' (for public shares)
			if (
				$user == $this->publicShareKeyId
				or $user == $this->recoveryKeyId
				or $util->ready()
			) {

				// Construct array of ready UIDs for Keymanager{}
				$readyIds[] = $user;

			} else {

				// Construct array of unready UIDs for Keymanager{}
				$unreadyIds[] = $user;

				// Log warning; we can't do necessary setup here
				// because we don't have the user passphrase
				\OC_Log::write( 'Encryption library', '"' . $user . '" is not setup for encryption', \OC_Log::WARN );

			}

		}

		return array(
			'ready' => $readyIds,
			'unready' => $unreadyIds
		);

	}

	/**
	 * @brief Decrypt a keyfile without knowing how it was encrypted
	 * @param string $filePath
	 * @param string $fileOwner
	 * @param string $privateKey
	 * @note Checks whether file was encrypted with openssl_seal or
	 *       openssl_encrypt, and decrypts accrdingly
	 * @note This was used when 2 types of encryption for keyfiles was used,
	 *       but now we've switched to exclusively using openssl_seal()
	 */
	public function decryptUnknownKeyfile( $filePath, $fileOwner, $privateKey ) {

		// Get the encrypted keyfile
		// NOTE: the keyfile format depends on how it was encrypted! At
		// this stage we don't know how it was encrypted
		$encKeyfile = Keymanager::getFileKey( $this->view, $this->userId, $filePath );

		// We need to decrypt the keyfile
		// Has the file been shared yet?
		if (
			$this->userId == $fileOwner
			&& !Keymanager::getShareKey( $this->view, $this->userId, $filePath ) // NOTE: we can't use isShared() here because it's a post share hook so it always returns true
		) {

			// The file has no shareKey, and its keyfile must be 
			// decrypted conventionally
			$plainKeyfile = Crypt::keyDecrypt( $encKeyfile, $privateKey );


		} else {

			// The file has a shareKey and must use it for decryption
			$shareKey = Keymanager::getShareKey( $this->view, $this->userId, $filePath );

			$plainKeyfile = Crypt::multiKeyDecrypt( $encKeyfile, $shareKey, $privateKey );

		}

		return $plainKeyfile;

	}

	/**
	 * @brief Encrypt keyfile to multiple users
	 * @param Session $session
	 * @param array $users list of users which should be able to access the file
	 * @param string $filePath path of the file to be shared
	 * @return bool
	 */
	public function setSharedFileKeyfiles( Session $session, array $users, $filePath ) {

		// Make sure users are capable of sharing
		$filteredUids = $this->filterShareReadyUsers( $users );

		// If we're attempting to share to unready users
		if ( !empty( $filteredUids['unready'] ) ) {

			\OC_Log::write( 'Encryption library', 'Sharing to these user(s) failed as they are unready for encryption:"' . print_r( $filteredUids['unready'], 1 ), \OC_Log::WARN );

			return false;

		}

		// Get public keys for each user, ready for generating sharekeys
		$userPubKeys = Keymanager::getPublicKeys( $this->view, $filteredUids['ready'] );

		// Note proxy status then disable it
		$proxyStatus = \OC_FileProxy::$enabled;
		\OC_FileProxy::$enabled = false;

		// Get the current users's private key for decrypting existing keyfile
		$privateKey = $session->getPrivateKey();

		$fileOwner = \OC\Files\Filesystem::getOwner( $filePath );

		// Decrypt keyfile
		$plainKeyfile = $this->decryptUnknownKeyfile( $filePath, $fileOwner, $privateKey );

		// Re-enc keyfile to (additional) sharekeys
		$multiEncKey = Crypt::multiKeyEncrypt( $plainKeyfile, $userPubKeys );

		// Save the recrypted key to it's owner's keyfiles directory
		// Save new sharekeys to all necessary user directory
		if (
			!Keymanager::setFileKey( $this->view, $filePath, $fileOwner, $multiEncKey['data'] )
			|| !Keymanager::setShareKeys( $this->view, $filePath, $multiEncKey['keys'] )
		) {

			\OC_Log::write( 'Encryption library', 'Keyfiles could not be saved for users sharing ' . $filePath, \OC_Log::ERROR );

			return false;

		}

		// Return proxy to original status
		\OC_FileProxy::$enabled = $proxyStatus;

		return true;
	}

	/**
	 * @brief Find, sanitise and format users sharing a file
	 * @note This wraps other methods into a portable bundle
	 */
	public function getSharingUsersArray( $sharingEnabled, $filePath, $currentUserId = false ) {

		// Check if key recovery is enabled
		if (
			\OC_Appconfig::getValue( 'files_encryption', 'recoveryAdminEnabled' )
			&& $this->recoveryEnabledForUser()
		) {

			$recoveryEnabled = true;

		} else {

			$recoveryEnabled = false;

		}

		// Make sure that a share key is generated for the owner too
		list( $owner, $ownerPath ) = $this->getUidAndFilename( $filePath );

		$userIds = array();
		if ( $sharingEnabled ) {

			// Find out who, if anyone, is sharing the file
			$result = \OCP\Share::getUsersSharingFile( $ownerPath, $owner, true, true, true );
			$userIds = $result['users'];
			if ( $result['public'] ) {
				$userIds[] = $this->publicShareKeyId;
			}

		}

		// If recovery is enabled, add the 
		// Admin UID to list of users to share to
		if ( $recoveryEnabled ) {

			// Find recoveryAdmin user ID
			$recoveryKeyId = \OC_Appconfig::getValue( 'files_encryption', 'recoveryKeyId' );

			// Add recoveryAdmin to list of users sharing
			$userIds[] = $recoveryKeyId;

		}

		// add current user if given
		if ( $currentUserId != false ) {

			$userIds[] = $currentUserId;

		}

		// Remove duplicate UIDs
		$uniqueUserIds = array_unique( $userIds );

		return $uniqueUserIds;

	}

	/**
	 * @brief Set file migration status for user
	 * @param $status
	 * @return bool
	 */
	public function setMigrationStatus( $status ) {

		$sql = 'UPDATE 
				*PREFIX*encryption 
			SET 
				migration_status = ?
			WHERE 
				uid = ?';

		$args = array( $status, $this->userId );

		$query = \OCP\DB::prepare( $sql );

		if ( $query->execute( $args ) ) {

			return true;

		} else {

			return false;

		}

	}

	/**
	 * @brief Check whether pwd recovery is enabled for a given user
	 * @return bool 1 = yes, 0 = no, false = no record
	 * @note If records are not being returned, check for a hidden space
	 *       at the start of the uid in db
	 */
	public function getMigrationStatus() {

		$sql = 'SELECT 
				migration_status
			FROM 
				`*PREFIX*encryption` 
			WHERE 
				uid = ?';

		$args = array( $this->userId );

		$query = \OCP\DB::prepare( $sql );

		$result = $query->execute( $args );

		$migrationStatus = array();

		$row = $result->fetchRow();
		if($row) {
			$migrationStatus[] = $row['migration_status'];
		}

		// If no record is found
		if ( empty( $migrationStatus ) ) {

			return false;

			// If a record is found
		} else {

			return $migrationStatus[0];

		}

	}

	/**
	 * @brief get uid of the owners of the file and the path to the file
	 * @param string $path Path of the file to check
	 * @note $shareFilePath must be relative to data/UID/files. Files
	 *       relative to /Shared are also acceptable
	 * @return array
	 */
	public function getUidAndFilename( $path ) {

		$view = new \OC\Files\View( $this->userFilesDir );
		$fileOwnerUid = $view->getOwner( $path );

		// handle public access
		if ( $this->isPublic ) {
			$filename = $path;
			$fileOwnerUid = $GLOBALS['fileOwner'];

			return array( $fileOwnerUid, $filename );
		} else {

			// Check that UID is valid
			if ( !\OCP\User::userExists( $fileOwnerUid ) ) {
				throw new \Exception( 'Could not find owner (UID = "' . var_export( $fileOwnerUid, 1 ) . '") of file "' . $path . '"' );
			}

			// NOTE: Bah, this dependency should be elsewhere
			\OC\Files\Filesystem::initMountPoints( $fileOwnerUid );

			// If the file owner is the currently logged in user
			if ( $fileOwnerUid == $this->userId ) {

				// Assume the path supplied is correct
				$filename = $path;

			} else {

				$info = $view->getFileInfo( $path );
				$ownerView = new \OC\Files\View( '/' . $fileOwnerUid . '/files' );

				// Fetch real file path from DB
				$filename = $ownerView->getPath( $info['fileid'] ); // TODO: Check that this returns a path without including the user data dir

			}

			return array( $fileOwnerUid, $filename );
		}


	}

	/**
	 * @brief go recursively through a dir and collect all files and sub files.
	 * @param string $dir relative to the users files folder
	 * @return array with list of files relative to the users files folder
	 */
	public function getAllFiles( $dir ) {

		$result = array();

		$content = $this->view->getDirectoryContent( $this->userFilesDir . $dir );

		// handling for re shared folders
		$path_split = explode( '/', $dir );

		foreach ( $content as $c ) {

			$sharedPart = $path_split[sizeof( $path_split ) - 1];
			$targetPathSplit = array_reverse( explode( '/', $c['path'] ) );

			$path = '';

			// rebuild path
			foreach ( $targetPathSplit as $pathPart ) {

				if ( $pathPart !== $sharedPart ) {

					$path = '/' . $pathPart . $path;

				} else {

					break;

				}

			}

			$path = $dir . $path;

			if ( $c['type'] === "dir" ) {

				$result = array_merge( $result, $this->getAllFiles( $path ) );

			} else {

				$result[] = $path;

			}
		}

		return $result;

	}

	/**
	 * @brief get shares parent.
	 * @param int $id of the current share
	 * @return array of the parent
	 */
	public static function getShareParent( $id ) {

		$query = \OC_DB::prepare( 'SELECT `file_target`, `item_type`'
			. ' FROM `*PREFIX*share`'
			. ' WHERE `id` = ?' );

		$result = $query->execute( array( $id ) );

		$row = $result->fetchRow();

		return $row;

	}

	/**
	 * @brief get shares parent.
	 * @param int $id of the current share
	 * @return array of the parent
	 */
	public static function getParentFromShare( $id ) {

		$query = \OC_DB::prepare( 'SELECT `parent`'
			. ' FROM `*PREFIX*share`'
			. ' WHERE `id` = ?' );

		$result = $query->execute( array( $id ) );

		$row = $result->fetchRow();

		return $row;

	}

	/**
	 * @brief get owner of the shared files.
	 * @param $id
	 * @internal param int $Id of a share
	 * @return string owner
	 */
	public function getOwnerFromSharedFile( $id ) {

		$query = \OC_DB::prepare( 'SELECT `parent`, `uid_owner` FROM `*PREFIX*share` WHERE `id` = ?', 1 );
		$source = $query->execute( array( $id ) )->fetchRow();

		$fileOwner = false;

		if ( isset( $source['parent'] ) ) {

			$parent = $source['parent'];

			while ( isset( $parent ) ) {

				$query = \OC_DB::prepare( 'SELECT `parent`, `uid_owner` FROM `*PREFIX*share` WHERE `id` = ?', 1 );
				$item = $query->execute( array( $parent ) )->fetchRow();

				if ( isset( $item['parent'] ) ) {

					$parent = $item['parent'];

				} else {

					$fileOwner = $item['uid_owner'];

					break;

				}
			}

		} else {

			$fileOwner = $source['uid_owner'];

		}

		return $fileOwner;

	}

	/**
	 * @return string
	 */
	public function getUserId() {
		return $this->userId;
	}

	/**
	 * @return string
	 */
	public function getUserFilesDir() {
		return $this->userFilesDir;
	}

	/**
	 * @param $password
	 * @return bool
	 */
	public function checkRecoveryPassword( $password ) {

		$pathKey = '/owncloud_private_key/' . $this->recoveryKeyId . ".private.key";
		$pathControlData = '/control-file/controlfile.enc';

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

		$recoveryKey = $this->view->file_get_contents( $pathKey );

		$decryptedRecoveryKey = Crypt::symmetricDecryptFileContent( $recoveryKey, $password );

		$controlData = $this->view->file_get_contents( $pathControlData );
		$decryptedControlData = Crypt::keyDecrypt( $controlData, $decryptedRecoveryKey );

		\OC_FileProxy::$enabled = $proxyStatus;

		if ( $decryptedControlData === 'ownCloud' ) {
			return true;
		}

		return false;
	}

	/**
	 * @return string
	 */
	public function getRecoveryKeyId() {
		return $this->recoveryKeyId;
	}

	/**
	 * @brief add recovery key to all encrypted files
	 */
	public function addRecoveryKeys( $path = '/' ) {
		$dirContent = $this->view->getDirectoryContent( $this->keyfilesPath . $path );
		foreach ( $dirContent as $item ) {
			// get relative path from files_encryption/keyfiles/
			$filePath = substr( $item['path'], strlen('files_encryption/keyfiles') );
			if ( $item['type'] == 'dir' ) {
				$this->addRecoveryKeys( $filePath . '/' );
			} else {
				$session = new Session( new \OC_FilesystemView( '/' ) );
				$sharingEnabled = \OCP\Share::isEnabled();
				$file = substr( $filePath, 0, -4 );
				$usersSharing = $this->getSharingUsersArray( $sharingEnabled, $file );
				$this->setSharedFileKeyfiles( $session, $usersSharing, $file );
			}
		}
	}

	/**
	 * @brief remove recovery key to all encrypted files
	 */
	public function removeRecoveryKeys( $path = '/' ) {
		$dirContent = $this->view->getDirectoryContent( $this->keyfilesPath . $path );
		foreach ( $dirContent as $item ) {
			// get relative path from files_encryption/keyfiles
			$filePath = substr( $item['path'], strlen('files_encryption/keyfiles') );
			if ( $item['type'] == 'dir' ) {
				$this->removeRecoveryKeys( $filePath . '/' );
			} else {
				$file = substr( $filePath, 0, -4 );
				$this->view->unlink( $this->shareKeysPath . '/' . $file . '.' . $this->recoveryKeyId . '.shareKey' );
			}
		}
	}

	/**
	 * @brief decrypt given file with recovery key and encrypt it again to the owner and his new key
	 * @param string $file
	 * @param string $privateKey recovery key to decrypt the file
	 */
	private function recoverFile( $file, $privateKey ) {

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

		// Find out who, if anyone, is sharing the file
		if ( $sharingEnabled ) {
			$result = \OCP\Share::getUsersSharingFile( $file, $this->userId, true, true, true );
			$userIds = $result['users'];
			$userIds[] = $this->recoveryKeyId;
			if ( $result['public'] ) {
				$userIds[] = $this->publicShareKeyId;
			}
		} else {
			$userIds = array( $this->userId, $this->recoveryKeyId );
		}
		$filteredUids = $this->filterShareReadyUsers( $userIds );

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

		//decrypt file key
		$encKeyfile = $this->view->file_get_contents( $this->keyfilesPath . $file . ".key" );
		$shareKey = $this->view->file_get_contents( $this->shareKeysPath . $file . "." . $this->recoveryKeyId . ".shareKey" );
		$plainKeyfile = Crypt::multiKeyDecrypt( $encKeyfile, $shareKey, $privateKey );
		// encrypt file key again to all users, this time with the new public key for the recovered use
		$userPubKeys = Keymanager::getPublicKeys( $this->view, $filteredUids['ready'] );
		$multiEncKey = Crypt::multiKeyEncrypt( $plainKeyfile, $userPubKeys );

		// write new keys to filesystem TDOO!
		$this->view->file_put_contents( $this->keyfilesPath . $file . '.key', $multiEncKey['data'] );
		foreach ( $multiEncKey['keys'] as $userId => $shareKey ) {
			$shareKeyPath = $this->shareKeysPath . $file . '.' . $userId . '.shareKey';
			$this->view->file_put_contents( $shareKeyPath, $shareKey );
		}

		// Return proxy to original status
		\OC_FileProxy::$enabled = $proxyStatus;
	}

	/**
	 * @brief collect all files and recover them one by one
	 * @param string $path to look for files keys
	 * @param string $privateKey private recovery key which is used to decrypt the files
	 */
	private function recoverAllFiles( $path, $privateKey ) {
		$dirContent = $this->view->getDirectoryContent( $this->keyfilesPath . $path );
		foreach ( $dirContent as $item ) {
			$filePath = substr( $item['path'], 25 );
			if ( $item['type'] == 'dir' ) {
				$this->recoverAllFiles( $filePath . '/', $privateKey );
			} else {
				$file = substr( $filePath, 0, -4 );
				$this->recoverFile( $file, $privateKey );
			}
		}
	}

	/**
	 * @brief recover users files in case of password lost
	 * @param string $recoveryPassword
	 */
	public function recoverUsersFiles( $recoveryPassword ) {

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

		$encryptedKey = $this->view->file_get_contents( '/owncloud_private_key/' . $this->recoveryKeyId . '.private.key' );
		$privateKey = Crypt::symmetricDecryptFileContent( $encryptedKey, $recoveryPassword );

		\OC_FileProxy::$enabled = $proxyStatus;

		$this->recoverAllFiles( '/', $privateKey );
	}

}