owncloud/core

<?php
/**
 * @author Bart Visscher <bartv@thisnet.nl>
 * @author Felix Moeller <mail@felixmoeller.de>
 * @author Lukas Reschke <lukas@statuscode.ch>
 * @author Morris Jobke <hey@morrisjobke.de>
 * @author Robin Appelman <icewind@owncloud.com>
 * @author Thomas Müller <thomas.mueller@tmit.eu>
 * @author Vincent Petry <pvince81@owncloud.com>
 *
 * @copyright Copyright (c) 2018, ownCloud GmbH
 * @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/>
 *
 */

/**
 * wrapper for server side events (http://en.wikipedia.org/wiki/Server-sent_events)
 * includes a fallback for older browsers and IE
 *
 * use server side events with caution, to many open requests can hang the server
 */
class OC_EventSource implements \OCP\IEventSource {
    /**
     * @var bool
     */
    private $fallback;

    /**
     * @var int
     */
    private $fallBackId = 0;

    /**
     * @var bool
     */
    private $started = false;

    protected function init() {
        if ($this->started) {
            return;
        }
        $this->started = true;

        // prevent php output buffering, caching and nginx buffering
        OC_Util::obEnd();
        \header('Cache-Control: no-cache');
        \header('X-Accel-Buffering: no');
        $this->fallback = isset($_GET['fallback']) and $_GET['fallback'] == 'true';
        if ($this->fallback) {
            $this->fallBackId = (int)$_GET['fallback_id'];
            /**
             * FIXME: The default content-security-policy of ownCloud forbids inline
             * JavaScript for security reasons. IE starting on Windows 10 will
             * however also obey the CSP which will break the event source fallback.
             *
             * As a workaround thus we set a custom policy which allows the execution
             * of inline JavaScript.
             *
             * @link https://github.com/owncloud/core/issues/14286
             */
            \header("Content-Security-Policy: default-src 'none'; script-src 'unsafe-inline'");
            \header("Content-Type: text/html");
            echo \str_repeat('<span></span>' . PHP_EOL, 10); //dummy data to keep IE happy
        } else {
            \header("Content-Type: text/event-stream");
        }
        if (!(\OC::$server->getRequest()->passesCSRFCheck())) {
            $this->send('error', 'Possible CSRF attack. Connection will be closed.');
            $this->close();
            exit();
        }
        \flush();
    }

    /**
     * send a message to the client
     *
     * @param string $type
     * @param mixed $data
     *
     * @throws \BadMethodCallException
     * if only one parameter is given, a typeless message will be send with that parameter as data
     */
    public function send($type, $data = null) {
        if ($data and !\preg_match('/^[A-Za-z0-9_]+$/', $type)) {
            throw new BadMethodCallException('Type needs to be alphanumeric ('. $type .')');
        }
        $this->init();
        if ($data === null) {
            $data = $type;
            $type = null;
        }
        if ($this->fallback) {
            $response = '<script type="text/javascript">window.parent.OC.EventSource.fallBackCallBack('
                . $this->fallBackId . ',"' . $type . '",' . OCP\JSON::encode($data) . ')</script>' . PHP_EOL;
            echo $response;
        } else {
            if ($type) {
                echo 'event: ' . $type . PHP_EOL;
            }
            echo 'data: ' . OCP\JSON::encode($data) . PHP_EOL;
        }
        echo PHP_EOL;
        \flush();
    }

    /**
     * close the connection of the event source
     */
    public function close() {
        $this->send('__internal__', 'close'); //server side closing can be an issue, let the client do it
    }
}