<?php
  
  /**
   * ownCloud
   *
   * @author Florin Peter
   * @copyright 2013 Florin Peter <owncloud@florin-peter.de>
   *
   * 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 OCA\Encryption;
  
  /**

   * Class to manage registration of hooks an various helper methods

   * @package OCA\Encryption
   */
  class Helper {

  	private static $tmpFileMapping; // Map tmp files to files in data/user/files

  	/**

  	 * register share related hooks

  	 *
  	 */
  	public static function registerShareHooks() {
  
  		\OCP\Util::connectHook('OCP\Share', 'pre_shared', 'OCA\Encryption\Hooks', 'preShared');
  		\OCP\Util::connectHook('OCP\Share', 'post_shared', 'OCA\Encryption\Hooks', 'postShared');
  		\OCP\Util::connectHook('OCP\Share', 'post_unshare', 'OCA\Encryption\Hooks', 'postUnshare');
  	}
  
  	/**

  	 * register user related hooks

  	 *
  	 */
  	public static function registerUserHooks() {
  
  		\OCP\Util::connectHook('OC_User', 'post_login', 'OCA\Encryption\Hooks', 'login');

  		\OCP\Util::connectHook('OC_User', 'logout', 'OCA\Encryption\Hooks', 'logout');

  		\OCP\Util::connectHook('OC_User', 'post_setPassword', 'OCA\Encryption\Hooks', 'setPassphrase');
  		\OCP\Util::connectHook('OC_User', 'pre_setPassword', 'OCA\Encryption\Hooks', 'preSetPassphrase');
  		\OCP\Util::connectHook('OC_User', 'post_createUser', 'OCA\Encryption\Hooks', 'postCreateUser');
  		\OCP\Util::connectHook('OC_User', 'post_deleteUser', 'OCA\Encryption\Hooks', 'postDeleteUser');
  	}
  
  	/**

  	 * register filesystem related hooks

  	 *
  	 */
  	public static function registerFilesystemHooks() {

  		\OCP\Util::connectHook('OC_Filesystem', 'rename', 'OCA\Encryption\Hooks', 'preRename');

  		\OCP\Util::connectHook('OC_Filesystem', 'post_rename', 'OCA\Encryption\Hooks', 'postRenameOrCopy');
  		\OCP\Util::connectHook('OC_Filesystem', 'copy', 'OCA\Encryption\Hooks', 'preCopy');
  		\OCP\Util::connectHook('OC_Filesystem', 'post_copy', 'OCA\Encryption\Hooks', 'postRenameOrCopy');

  		\OCP\Util::connectHook('OC_Filesystem', 'post_delete', 'OCA\Encryption\Hooks', 'postDelete');
  		\OCP\Util::connectHook('OC_Filesystem', 'delete', 'OCA\Encryption\Hooks', 'preDelete');

  		\OCP\Util::connectHook('OC_Filesystem', 'post_umount', 'OCA\Encryption\Hooks', 'postUmount');
  		\OCP\Util::connectHook('OC_Filesystem', 'umount', 'OCA\Encryption\Hooks', 'preUmount');

  	}
  
  	/**

  	 * register app management related hooks

  	 *
  	 */
  	public static function registerAppHooks() {
  
  		\OCP\Util::connectHook('OC_App', 'pre_disable', 'OCA\Encryption\Hooks', 'preDisable');

  		\OCP\Util::connectHook('OC_App', 'post_disable', 'OCA\Encryption\Hooks', 'postEnable');

  	}
  
  	/**

  	 * setup user for files_encryption

  	 *
  	 * @param Util $util
  	 * @param string $password
  	 * @return bool
  	 */
  	public static function setupUser($util, $password) {
  		// Check files_encryption infrastructure is ready for action
  		if (!$util->ready()) {
  
  			\OCP\Util::writeLog('Encryption library', 'User account "' . $util->getUserId()
  													  . '" is not ready for encryption; configuration started', \OCP\Util::DEBUG);
  
  			if (!$util->setupServerSide($password)) {
  				return false;
  			}
  		}
  
  		return true;
  	}
  
  	/**

  	 * enable recovery

  	 *

  	 * @param string $recoveryKeyId
  	 * @param string $recoveryPassword

  	 * @internal param \OCA\Encryption\Util $util
  	 * @internal param string $password
  	 * @return bool
  	 */
  	public static function adminEnableRecovery($recoveryKeyId, $recoveryPassword) {
  
  		$view = new \OC\Files\View('/');

  		$appConfig = \OC::$server->getAppConfig();

  
  		if ($recoveryKeyId === null) {
  			$recoveryKeyId = 'recovery_' . substr(md5(time()), 0, 8);

  			$appConfig->setValue('files_encryption', 'recoveryKeyId', $recoveryKeyId);

  		}
  
  		if (!$view->is_dir('/owncloud_private_key')) {
  			$view->mkdir('/owncloud_private_key');
  		}
  
  		if (
  			(!$view->file_exists("/public-keys/" . $recoveryKeyId . ".public.key")
  			 || !$view->file_exists("/owncloud_private_key/" . $recoveryKeyId . ".private.key"))
  		) {
  
  			$keypair = \OCA\Encryption\Crypt::createKeypair();
  
  			\OC_FileProxy::$enabled = false;
  
  			// Save public key
  
  			if (!$view->is_dir('/public-keys')) {
  				$view->mkdir('/public-keys');
  			}
  
  			$view->file_put_contents('/public-keys/' . $recoveryKeyId . '.public.key', $keypair['publicKey']);

  			$cipher = \OCA\Encryption\Helper::getCipher();
  			$encryptedKey = \OCA\Encryption\Crypt::symmetricEncryptFileContent($keypair['privateKey'], $recoveryPassword, $cipher);
  			if ($encryptedKey) {
  				Keymanager::setPrivateSystemKey($encryptedKey, $recoveryKeyId . '.private.key');
  				// Set recoveryAdmin as enabled
  				$appConfig->setValue('files_encryption', 'recoveryAdminEnabled', 1);
  				$return = true;
  			}

  
  			\OC_FileProxy::$enabled = true;

  		} else { // get recovery key and check the password

  			$util = new \OCA\Encryption\Util(new \OC\Files\View('/'), \OCP\User::getUser());

  			$return = $util->checkRecoveryPassword($recoveryPassword);
  			if ($return) {

  				$appConfig->setValue('files_encryption', 'recoveryAdminEnabled', 1);

  			}
  		}
  
  		return $return;
  	}

  	/**

  	 * Check if a path is a .part file

  	 * @param string $path Path that may identify a .part file
  	 * @return bool
  	 */
  	public static function isPartialFilePath($path) {
  
  		$extension = pathinfo($path, PATHINFO_EXTENSION);
  		if ( $extension === 'part') {
  			return true;
  		} else {
  			return false;
  		}
  
  	}
  
  
  	/**

  	 * Remove .path extension from a file path

  	 * @param string $path Path that may identify a .part file
  	 * @return string File path without .part extension
  	 * @note this is needed for reusing keys
  	 */
  	public static function stripPartialFileExtension($path) {
  		$extension = pathinfo($path, PATHINFO_EXTENSION);
  
  		if ( $extension === 'part') {
  
  			$newLength = strlen($path) - 5; // 5 = strlen(".part") = strlen(".etmp")
  			$fPath = substr($path, 0, $newLength);
  
  			// if path also contains a transaction id, we remove it too
  			$extension = pathinfo($fPath, PATHINFO_EXTENSION);
  			if(substr($extension, 0, 12) === 'ocTransferId') { // 12 = strlen("ocTransferId")
  				$newLength = strlen($fPath) - strlen($extension) -1;
  				$fPath = substr($fPath, 0, $newLength);
  			}
  			return $fPath;
  
  		} else {
  			return $path;
  		}
  	}

  
  	/**

  	 * disable recovery

  	 *

  	 * @param string $recoveryPassword

  	 * @return bool
  	 */
  	public static function adminDisableRecovery($recoveryPassword) {

  		$util = new Util(new \OC\Files\View('/'), \OCP\User::getUser());

  		$return = $util->checkRecoveryPassword($recoveryPassword);
  
  		if ($return) {
  			// Set recoveryAdmin as disabled

  			\OC::$server->getAppConfig()->setValue('files_encryption', 'recoveryAdminEnabled', 0);

  		}
  
  		return $return;
  	}

  	/**

  	 * checks if access is public/anonymous user

  	 * @return bool
  	 */
  	public static function isPublicAccess() {

  		if (\OCP\User::getUser() === false) {

  			return true;
  		} else {
  			return false;
  		}
  	}
  
  	/**

  	 * Format a path to be relative to the /user/files/ directory

  	 * @param string $path the absolute path
  	 * @return string e.g. turns '/admin/files/test.txt' into 'test.txt'
  	 */
  	public static function stripUserFilesPath($path) {
  		$trimmed = ltrim($path, '/');
  		$split = explode('/', $trimmed);

  
  		// it is not a file relative to data/user/files
  		if (count($split) < 3 || $split[1] !== 'files') {
  			return false;
  		}

  		$sliced = array_slice($split, 2);
  		$relPath = implode('/', $sliced);
  
  		return $relPath;
  	}
  
  	/**

  	 * try to get the user from the path if no user is logged in

  	 * @param string $path
  	 * @return mixed user or false if we couldn't determine a user
  	 */
  	public static function getUser($path) {
  
  		$user = \OCP\User::getUser();
  
  
  		// if we are logged in, then we return the userid
  		if ($user) {
  			return $user;
  		}
  
  		// if no user is logged in we try to access a publicly shared files.
  		// In this case we need to try to get the user from the path
  
  		$trimmed = ltrim($path, '/');
  		$split = explode('/', $trimmed);
  
  		// it is not a file relative to data/user/files

  		if (count($split) < 2 || ($split[1] !== 'files' && $split[1] !== 'cache')) {

  			return false;
  		}
  
  		$user = $split[0];
  
  		if (\OCP\User::userExists($user)) {
  			return $user;
  		}
  
  		return false;
  	}
  
  	/**

  	 * get path to the corresponding file in data/user/files if path points

  	 *        to a version or to a file in cache
  	 * @param string $path path to a version or a file in the trash
  	 * @return string path to corresponding file relative to data/user/files
  	 */
  	public static function getPathToRealFile($path) {
  		$trimmed = ltrim($path, '/');
  		$split = explode('/', $trimmed);
  		$result = false;
  
  		if (count($split) >= 3 && ($split[1] === "files_versions" || $split[1] === 'cache')) {
  			$sliced = array_slice($split, 2);
  			$result = implode('/', $sliced);
  			if ($split[1] === "files_versions") {
  				// we skip user/files
  				$sliced = array_slice($split, 2);
  				$relPath = implode('/', $sliced);
  				//remove the last .v
  				$result = substr($relPath, 0, strrpos($relPath, '.v'));
  			}
  			if ($split[1] === "cache") {
  				// we skip /user/cache/transactionId
  				$sliced = array_slice($split, 3);
  				$result = implode('/', $sliced);
  				//prepare the folders
  				self::mkdirr($path, new \OC\Files\View('/'));
  			}
  		}
  
  		return $result;
  	}
  
  	/**

  	 * create directory recursively

  	 * @param string $path
  	 * @param \OC\Files\View $view
  	 */
  	public static function mkdirr($path, $view) {

  		$dirname = \OC\Files\Filesystem::normalizePath(dirname($path));

  		$dirParts = explode('/', $dirname);
  		$dir = "";
  		foreach ($dirParts as $part) {
  			$dir = $dir . '/' . $part;
  			if (!$view->file_exists($dir)) {
  				$view->mkdir($dir);
  			}
  		}
  	}
  
  	/**

  	 * redirect to a error page
  	 * @param Session $session

  	 */

  	public static function redirectToErrorPage($session, $errorCode = null) {
  
  		if ($errorCode === null) {
  			$init = $session->getInitialized();
  			switch ($init) {
  				case \OCA\Encryption\Session::INIT_EXECUTED:
  					$errorCode = \OCA\Encryption\Crypt::ENCRYPTION_PRIVATE_KEY_NOT_VALID_ERROR;
  					break;
  				case \OCA\Encryption\Session::NOT_INITIALIZED:
  					$errorCode = \OCA\Encryption\Crypt::ENCRYPTION_NOT_INITIALIZED_ERROR;
  					break;
  				default:
  					$errorCode = \OCA\Encryption\Crypt::ENCRYPTION_UNKNOWN_ERROR;
  			}
  		}

  		$location = \OC_Helper::linkToAbsolute('apps/files_encryption/files', 'error.php');
  		$post = 0;
  		if(count($_POST) > 0) {
  			$post = 1;

  		}
  
  		if(defined('PHPUNIT_RUN') and PHPUNIT_RUN) {
  			throw new \Exception("Encryption error: $errorCode");
  		}
  
  		header('Location: ' . $location . '?p=' . $post . '&errorCode=' . $errorCode);
  		exit();

  	}
  
  	/**
  	 * check requirements for encryption app.
  	 * @return bool true if requirements are met
  	 */
  	public static function checkRequirements() {
  		$result = true;
  
  		//openssl extension needs to be loaded
  		$result &= extension_loaded("openssl");
  		// we need php >= 5.3.3
  		$result &= version_compare(phpversion(), '5.3.3', '>=');
  
  		return (bool) $result;
  	}

  	/**
  	 * check some common errors if the server isn't configured properly for encryption
  	 * @return bool true if configuration seems to be OK
  	 */
  	public static function checkConfiguration() {

  		if(self::getOpenSSLPkey()) {

  			return true;
  		} else {
  			while ($msg = openssl_error_string()) {
  				\OCP\Util::writeLog('Encryption library', 'openssl_pkey_new() fails:  ' . $msg, \OCP\Util::ERROR);
  			}
  			return false;
  		}
  	}
  
  	/**

  	 * Create an openssl pkey with config-supplied settings
  	 * WARNING: This initializes a new private keypair, which is computationally expensive
  	 * @return resource The pkey resource created
  	 */
  	public static function getOpenSSLPkey() {
  		return openssl_pkey_new(self::getOpenSSLConfig());
  	}
  
  	/**
  	 * Return an array of OpenSSL config options, default + config
  	 * Used for multiple OpenSSL functions
  	 * @return array The combined defaults and config settings
  	 */
  	public static function getOpenSSLConfig() {
  		$config = array('private_key_bits' => 4096);
  		$config = array_merge(\OCP\Config::getSystemValue('openssl', array()), $config);
  		return $config;
  	}
  
  	/**

  	 * find all share keys for a given file
  	 * @param string $path to the file
  	 * @param \OC\Files\View $view view, relative to data/
  	 * @return array list of files, path relative to data/

  	 */

  	public static function findShareKeys($path, $view) {
  		$result = array();
  		$pathinfo = pathinfo($path);
  		$dirContent = $view->opendir($pathinfo['dirname']);
  
  		if (is_resource($dirContent)) {
  			while (($file = readdir($dirContent)) !== false) {
  				if (!\OC\Files\Filesystem::isIgnoredDir($file)) {
  					if (preg_match("/" . $pathinfo['filename'] . ".(.*).shareKey/", $file)) {
  						$result[] = $pathinfo['dirname'] . '/' . $file;
  					}
  				}
  			}
  			closedir($dirContent);
  		}
  
  		return $result;

  	}

  
  	/**

  	 * remember from which file the tmp file (getLocalFile() call) was created

  	 * @param string $tmpFile path of tmp file
  	 * @param string $originalFile path of the original file relative to data/
  	 */
  	public static function addTmpFileToMapper($tmpFile, $originalFile) {
  		self::$tmpFileMapping[$tmpFile] = $originalFile;
  	}
  
  	/**

  	 * get the path of the original file

  	 * @param string $tmpFile path of the tmp file

  	 * @return string|false path of the original file or false

  	 */
  	public static function getPathFromTmpFile($tmpFile) {
  		if (isset(self::$tmpFileMapping[$tmpFile])) {
  			return self::$tmpFileMapping[$tmpFile];
  		}
  
  		return false;
  	}

  
  	/**
  	 * read the cipher used for encryption from the config.php
  	 *
  	 * @return string
  	 */
  	public static function getCipher() {
  
  		$cipher = \OCP\Config::getSystemValue('cipher', Crypt::DEFAULT_CIPHER);
  
  		if ($cipher !== 'AES-256-CFB' && $cipher !== 'AES-128-CFB') {
  			\OCP\Util::writeLog('files_encryption',
  					'wrong cipher defined in config.php, only AES-128-CFB and AES-256-CFB is supported. Fall back ' . Crypt::DEFAULT_CIPHER,
  					\OCP\Util::WARN);
  
  			$cipher = Crypt::DEFAULT_CIPHER;
  		}
  
  		return $cipher;
  	}

  }