Issue #22 - Split maintenance.php into preview.php and file.php

file.php

@@ -0,0 +1,63 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * This page is used to fetch files while in maintenance mode.
+ *
+ * It should avoid as much as possible using code Moodle API.
+ *
+ * @package    auth_outage
+ * @author     Daniel Thee Roperto <daniel.roperto@catalyst-au.net>
+ * @copyright  2016 Catalyst IT
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ *
+ * @var stdClass $CFG
+ */
+
+if (!isset($_GET['file'])) {
+    http_response_code(400);
+    die('Missing file parameter.');
+}
+
+define('NO_DEBUG_DISPLAY', true);
+define('ABORT_AFTER_CONFIG', true);
+require_once(__DIR__.'/../../config.php');
+
+// We are not using any external libraries or references in this file (cli maintenance is active).
+// If you change the path below maybe you need to change maintenance_static_page::get_resources_folder() as well.
+$resourcedir = $CFG->dataroot.'/auth_outage/climaintenance';
+
+// Protect against path traversal attacks.
+$file = $resourcedir.'/'.$_GET['file'];
+if (realpath($file) !== $file) {
+    // @codingStandardsIgnoreStart
+    error_log('Invalid file: '.$_GET['file']);
+    // @codingStandardsIgnoreEnd
+    http_response_code(404);
+    die('Not found.');
+}
+
+// Detect type, we only support css or PNG images.
+header('Content-Type: '.(substr($file, -3) == 'css' ? 'text/css' : 'image/png'));
+
+// Use cache.
+$lifetime = 60 * 60 * 24; // 1 day.
+header('Expires: '.gmdate('D, d M Y H:i:s', time() + $lifetime).' GMT');
+header('Pragma: ');
+header('Cache-Control: public, max-age='.$lifetime);
+header('Accept-Ranges: none');
+
+readfile($file);