Moodle32-Check-file-license-and-expiry-date.patch

From 853aef386a56ccd334b6ae9ee6ac9d2f5652cbd5 Mon Sep 17 00:00:00 2001
From: Martin Gauk <gauk@math.tu-berlin.de>
Date: Tue, 20 Jun 2017 14:40:21 +0000
Subject: [PATCH] [ISIS] Check file license and expiry date
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Used to conform to law (§ 52a UrhG) and to make
copyrighted texts unavailable to students.

lib/filestorage/zip_packer.php is changed because mod_folder
allows to bulk download files as a zip through this class.
---
 lang/en/license.php             |  2 ++
 lib/filelib.php                 |  2 ++
 lib/filestorage/stored_file.php | 57 +++++++++++++++++++++++++++++++++++++++++
 lib/filestorage/zip_packer.php  |  5 ++++
 4 files changed, 66 insertions(+)

diff --git a/lang/en/license.php b/lang/en/license.php
index cf25bce..45e264b 100644
--- a/lang/en/license.php
+++ b/lang/en/license.php
@@ -22,6 +22,8 @@
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
+$string['fileexpired'] = 'The requested file is no longer available for copyright reasons. If you think the file is blocked for no reason, please contact a teacher.';
+
 $string['allrightsreserved'] = 'All rights reserved';
 $string['cc'] = 'Creative Commons';
 $string['cc-nc'] = 'Creative Commons - No Commercial';
diff --git a/lib/filelib.php b/lib/filelib.php
index b568436..4c2b0b4 100644
--- a/lib/filelib.php
+++ b/lib/filelib.php
@@ -2288,6 +2288,8 @@ function send_file($path, $filename, $lifetime = null , $filter=0, $pathisstring
 function send_stored_file($stored_file, $lifetime=null, $filter=0, $forcedownload=false, array $options=array()) {
     global $CFG, $COURSE;
 
+    $stored_file->check_mimetype_license_expiry_date(true); // ISIS, MG, 20.06.2017
+
     if (empty($options['filename'])) {
         $filename = null;
     } else {
diff --git a/lib/filestorage/stored_file.php b/lib/filestorage/stored_file.php
index 7d3b64f..9ddd2de 100644
--- a/lib/filestorage/stored_file.php
+++ b/lib/filestorage/stored_file.php
@@ -1087,4 +1087,61 @@ class stored_file {
         // Generate the resized image.
         return resize_image_from_image($original, $imageinfo, $width, $height);
     }
+    
+    /**
+     * Check if a file with a specific license has expired.
+     *
+     * This checks if a file has been expired because:
+     *  - it is a document (has a particular mimetype),
+     *  - has been provided under a specific license
+     *  - and the expiry date has exceeded (in respect of the course start date and the file creation time).
+     *
+     * Users with moodle/course:managefiles right (teachers) are always allowed to access the files.
+     *
+     * The following settings need to be defined in the config.php:
+     *   array $CFG->fileexpirylicenses which licenses (shortnames) expire
+     *   int $CFG->fileexpirydate when do files expire (unix time)
+     *   array $CFG->filemimetypes['document'] mime types of documents
+     *
+     * These adjustments were made by Technische Universität Berlin in order to conform to § 52a UrhG.
+     *
+     * @param bool $exit if true, terminate execution with a message
+     * @return boolean whether file is allowed to be delivered
+     * @copyright 2017 Martin Gauk (ISIS, innoCampus, TU Berlin)
+     */
+    public function check_mimetype_license_expiry_date($exit = false) {
+        global $CFG, $COURSE;
+
+        // Check if enabled/configured.
+        if (!isset($CFG->fileexpirydate, $CFG->fileexpirylicenses, $CFG->filemimetypes['document'])) {
+            return true;
+        }
+
+        if (in_array($this->get_license(), $CFG->fileexpirylicenses) &&
+                !has_capability('moodle/course:managefiles', context::instance_by_id($this->get_contextid(), MUST_EXIST))) {
+            $isdoc = false;
+            $fmimetype = $this->get_mimetype();
+            foreach ($CFG->filemimetypes['document'] as $mime) {
+                if ($mime === $fmimetype || (substr($mime, -1) === '%' && strncmp($mime, $fmimetype, strlen($mime) - 1) === 0)) {
+                    $isdoc = true;
+                    break;
+                }
+            }
+            $coursestart = isset($COURSE->startdate) ? $COURSE->startdate : 0;
+            if ($isdoc && $CFG->fileexpirydate > max($coursestart, $this->get_timecreated())) {
+                if ($exit) {
+                    global $OUTPUT, $PAGE;
+                    http_response_code(451);
+                    $PAGE->set_title('451 Unavailable For Legal Reasons');
+                    echo $OUTPUT->header();
+                    \core\notification::add(get_string('fileexpired', 'core_license'), \core\output\notification::NOTIFY_ERROR);
+                    echo $OUTPUT->footer();
+                    exit();
+                }
+                return false;
+            }
+        }
+
+        return true;
+    }
 }
diff --git a/lib/filestorage/zip_packer.php b/lib/filestorage/zip_packer.php
index 47395f7..a13b3d9 100644
--- a/lib/filestorage/zip_packer.php
+++ b/lib/filestorage/zip_packer.php
@@ -199,6 +199,11 @@ class zip_packer extends file_packer {
             if (!$file->is_directory()) {
                 $path = $path.$file->get_filename();
             }
+
+            if (!$file->check_mimetype_license_expiry_date()) { // ISIS, MG, 20.06.2017
+                continue; // ISIS, MG, 20.06.2017
+            } // ISIS, MG, 20.06.2017
+
             // Ignore result here, partial zipping is ok for now.
             $file->archive_file($ziparch, $path);
         }
-- 
2.1.4