MDL-58132 repositories: Controlled link file type

This introduces a new "controlled link" file type where the file is not
stored in Moodle - but Moodle will control the access permissions on the file.

Plugins can "freeze" a filearea which means Moodle will take ownership of all the remote
files of this type.

When accessing a file, if the "filebrowser" infomation indicates the current user can write to the file, they
will be granted temporary write access.

Part of MDL-58220

backup/backupfilesedit_form.php

@@ -30,7 +30,8 @@ class backup_files_edit_form extends moodleform {
     public function definition() {
         $mform =& $this->_form;
 
-        $options = array('subdirs' => 0, 'maxfiles' => -1, 'accepted_types' => '*', 'return_types' => FILE_INTERNAL | FILE_REFERENCE);
+        $types = (FILE_INTERNAL | FILE_REFERENCE | FILE_CONTRLLED_LINK);
+        $options = array('subdirs' => 0, 'maxfiles' => -1, 'accepted_types' => '*', 'return_types' => $types);
 
         $mform->addElement('filemanager', 'files_filemanager', get_string('files'), null, $options);
 

files/renderer.php

@@ -772,6 +772,12 @@ protected function fp_js_template_selectlayout() {
                         <input type="radio"/>
                     </div>
                 </div>
+                <div class="fp-linktype-8 control-group control-radio clearfix">
+                    <label class="control-label control-radio">'.get_string('makefilecontrolledlink', 'repository').'</label>
+                    <div class="controls control-radio">
+                        <input type="radio"/>
+                    </div>
+                </div>
                 <div class="fp-saveas control-group clearfix">
                     <label class="control-label">'.get_string('saveas', 'repository').'</label>
                     <div class="controls">

lang/en/repository.php

@@ -160,6 +160,7 @@
 $string['makefileinternal'] = 'Make a copy of the file';
 $string['makefilelink'] = 'Link to the file directly';
 $string['makefilereference'] = 'Create an alias/shortcut to the file';
+$string['makefilecontrolledlink'] = 'Create an access controlled link to the file';
 $string['manage'] = 'Manage repositories';
 $string['manageinstances'] = 'Manage instances';
 $string['manageurl'] = 'Manage';

lib/filelib.php

@@ -256,6 +256,21 @@ function file_postupdate_standard_editor($data, $field, array $options, $context
     return $data;
 }
 
+/**
+ * For all files in this file area - walk the file list and copy each to a system owned account, making them read-only.
+ *
+ * @category files
+ * @param stdClass $context context - must already exist
+ * @param string $component
+ * @param string $filearea file area name
+ * @param int $itemid
+ * @return bool
+ */
+function file_prevent_changes_to_external_files($contextid, $component, $filearea, $itemid=false) {
+    $fs = get_file_storage();
+    return $fs->prevent_changes_to_external_files($contextid, $component, $filearea, $itemid);
+}
+
 /**
  * Saves text and files modified by Editor formslib element
  *
@@ -813,7 +828,7 @@ function file_save_draft_area_files($draftitemid, $contextid, $component, $filea
         $options['areamaxbytes'] = FILE_AREA_MAX_BYTES_UNLIMITED; // Unlimited.
     }
     $allowreferences = true;
-    if (isset($options['return_types']) && !($options['return_types'] & FILE_REFERENCE)) {
+    if (isset($options['return_types']) && !($options['return_types'] & (FILE_REFERENCE | FILE_CONTROLLED_LINK))) {
         // we assume that if $options['return_types'] is NOT specified, we DO allow references.
         // this is not exactly right. BUT there are many places in code where filemanager options
         // are not passed to file_save_draft_area_files()

lib/filestorage/file_storage.php

@@ -2323,4 +2323,35 @@ public function update_references($referencefileid, $lastsync, $lifetime, $conte
         $data = array('id' => $referencefileid, 'lastsync' => $lastsync);
         $DB->update_record('files_reference', (object)$data);
     }
+
+    /**
+     * For an entire file area - walk through the files and for each one that is a controlled link,
+     * call prevent_changes on the repository. Typically this will copy the external file to a system
+     * account controlled by Moodle, remove all write access and update the file reference.
+     *
+     * @param int $contextid
+     * @param string $component
+     * @param string $filearea
+     * @param int $itemid
+     */
+    public function prevent_changes_to_external_files($contextid, $component, $filearea, $itemid = false) {
+        global $DB;
+
+        $transaction = $DB->start_delegated_transaction();
+
+        $files = $this->get_area_files($contextid, $component, $filearea, $itemid, 'id', false);
+
+        foreach ($files as $file) {
+            if ($file->is_external_file()) {
+                // Note that this function uses a cache, so we don't need to
+                // double cache these.
+                $repo = repository::get_repository_by_id($file->get_repository_id(), SYSCONTEXTID);
+
+                // We expect this function to throw exceptions on failure.
+                $repo->prevent_changes_to_external_file($file);
+            }
+        }
+        $transaction->allow_commit();
+        return true;
+    }
 }

lib/filestorage/stored_file.php

@@ -102,6 +102,15 @@ public function is_external_file() {
         return !empty($this->repository);
     }
 
+    /**
+     * Whether or not this is a controlled link. Note that repositories cannot support FILE_REFERENCE and FILE_CONTROLLED_LINK.
+     *
+     * @return bool
+     */
+    public function is_controlled_link() {
+        return $this->is_external_file() && $this->repository->supported_returntypes() & FILE_CONTROLLED_LINK;
+    }
+
     /**
      * Update some file record fields
      * NOTE: Must remain protected

lib/form/editor.php

@@ -58,8 +58,8 @@ class MoodleQuickForm_editor extends HTML_QuickForm_element implements templatab
     /** @var array options provided to initalize filepicker */
     protected $_options = array('subdirs' => 0, 'maxbytes' => 0, 'maxfiles' => 0, 'changeformat' => 0,
             'areamaxbytes' => FILE_AREA_MAX_BYTES_UNLIMITED, 'context' => null, 'noclean' => 0, 'trusttext' => 0,
-            'return_types' => 7, 'enable_filemanagement' => true);
-    // $_options['return_types'] = FILE_INTERNAL | FILE_EXTERNAL | FILE_REFERENCE
+            'return_types' => 15, 'enable_filemanagement' => true);
+    // $_options['return_types'] = FILE_INTERNAL | FILE_EXTERNAL | FILE_REFERENCE | FILE_CONTROLLED_LINK
 
     /** @var array values for editor */
     protected $_values     = array('text'=>null, 'format'=>null, 'itemid'=>null);

lib/form/filemanager.php

@@ -78,7 +78,7 @@ public function __construct($elementName=null, $elementLabel=null, $attributes=n
             $this->_options['maxbytes'] = get_user_max_upload_file_size($PAGE->context, $CFG->maxbytes, $options['maxbytes']);
         }
         if (empty($options['return_types'])) {
-            $this->_options['return_types'] = (FILE_INTERNAL | FILE_REFERENCE);
+            $this->_options['return_types'] = (FILE_INTERNAL | FILE_REFERENCE | FILE_CONTROLLED_LINK);
         }
         $this->_type = 'filemanager';
         parent::__construct($elementName, $elementLabel, $attributes);

lib/upgrade.txt

@@ -1,6 +1,11 @@
 This files describes API changes in core libraries and APIs,
 information provided here is intended especially for developers.
 === 3.3 ===
+* Support added for a new type of external file: FILE_CONTROLLED_LINK. This is an external file that Moodle can control
+  the permissions. Moodle can make files read-only or grant temporary write access.
+    To make all the files in file area read only (owned by Moodle) - use file_prevent_changes_to_external_files().
+    When accessing a URL, the info from file_browser::get_file_info will be checked to determine if the user has write access,
+    if they do - the remote file will have access controls set to allow editing.
 * The method moodleform::after_definition() has been added and can now be used to add some logic
   to be performed after the form's definition was set. This is useful for intermediate subclasses.
 * Moodle has support for font-awesome icons. Plugins should use the xxx_get_fontawesome_icon_map callback

mod/assign/assignmentplugin.php

@@ -580,17 +580,26 @@ public function get_file_areas() {
     public function get_file_info($browser, $filearea, $itemid, $filepath, $filename) {
         global $CFG, $DB, $USER;
         $urlbase = $CFG->wwwroot.'/pluginfile.php';
-
+        $writeaccess = false;
         // Permission check on the itemid.
 
         if ($this->get_subtype() == 'assignsubmission') {
             if ($itemid) {
-                $record = $DB->get_record('assign_submission', array('id'=>$itemid), 'userid', IGNORE_MISSING);
+                $record = $DB->get_record('assign_submission', array('id'=>$itemid), 'userid,groupid', IGNORE_MISSING);
                 if (!$record) {
                     return null;
                 }
-                if (!$this->assignment->can_view_submission($record->userid)) {
-                    return null;
+                if (!empty($record->userid)) {
+                    if (!$this->assignment->can_view_submission($record->userid)) {
+                        return null;
+                    }
+                    $writeaccess = $this->assignment->can_edit_submission($record->userid);
+                } else {
+                    // Must be a team submission with a group.
+                    if (!$this->assignment->can_view_group_submission($record->groupid)) {
+                        return null;
+                    }
+                    $writeaccess = $this->assignment->can_edit_group_submission($record->groupid);
                 }
             }
         } else {
@@ -609,14 +618,15 @@ public function get_file_info($browser, $filearea, $itemid, $filepath, $filename
                                           $filename))) {
             return null;
         }
+
         return new file_info_stored($browser,
                                     $this->assignment->get_context(),
                                     $storedfile,
                                     $urlbase,
                                     $filearea,
                                     $itemid,
                                     true,
-                                    true,
+                                    $writeaccess,
                                     false);
     }
 

mod/assign/lang/en/assign.php

@@ -155,6 +155,7 @@
 $string['duedatereached'] = 'The due date for this assignment has now passed';
 $string['duedatevalidation'] = 'Due date must be after the allow submissions from date.';
 $string['editattemptfeedback'] = 'Edit the grade and feedback for attempt number {$a}.';
+$string['editonline'] = 'Edit online';
 $string['editingpreviousfeedbackwarning'] = 'You are editing the feedback for a previous attempt. This is attempt {$a->attemptnumber} out of {$a->totalattempts}.';
 $string['editoverride'] = 'Edit override';
 $string['editsubmission'] = 'Edit submission';

mod/assign/locallib.php

@@ -4360,6 +4360,25 @@ protected function is_graded($userid) {
         return false;
     }
 
+    /**
+     * Perform an access check to see if the current $USER can edit this group submission.
+     *
+     * @param int $groupid
+     * @return bool
+     */
+    public function can_edit_group_submission($groupid) {
+        global $USER;
+
+        $members = $this->get_submission_group_members($groupid, true);
+        foreach ($members as $member) {
+            // If we can edit any members submission, we can edit the submission for the group.
+            if ($this->can_edit_submission($member->id)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     /**
      * Perform an access check to see if the current $USER can view this group submission.
      *

mod/assign/renderable.php

@@ -911,6 +911,7 @@ public function __construct(context $context, $sid, $filearea, $component) {
      */
     public function preprocess($dir, $filearea, $component) {
         global $CFG;
+
         foreach ($dir['subdirs'] as $subdir) {
             $this->preprocess($subdir, $filearea, $component);
         }

mod/assign/renderer.php

@@ -1420,7 +1420,7 @@ protected function htmllize_tree(assign_files $tree, $dir) {
             $result .= '<li yuiConfig=\'' . json_encode($yuiconfig) . '\'>' .
                        '<div>' . $image . ' ' .
                                  $file->fileurl . ' ' .
-                                 $plagiarismlinks .
+                                 $plagiarismlinks . ' ' .
                                  $file->portfoliobutton . '</div>' .
                        '</li>';
         }

mod/assign/submission/file/locallib.php

@@ -125,11 +125,11 @@ public function save_settings(stdClass $data) {
      * @return array
      */
     private function get_file_options() {
-        $fileoptions = array('subdirs'=>1,
-                                'maxbytes'=>$this->get_config('maxsubmissionsizebytes'),
-                                'maxfiles'=>$this->get_config('maxfilesubmissions'),
-                                'accepted_types'=>'*',
-                                'return_types'=>FILE_INTERNAL);
+        $fileoptions = array('subdirs' => 1,
+                                'maxbytes' => $this->get_config('maxsubmissionsizebytes'),
+                                'maxfiles' => $this->get_config('maxfilesubmissions'),
+                                'accepted_types' => '*',
+                                'return_types' => (FILE_INTERNAL | FILE_CONTROLLED_LINK));
         if ($fileoptions['maxbytes'] == 0) {
             // Use module default.
             $fileoptions['maxbytes'] = get_config('assignsubmission_file', 'maxbytes');
@@ -174,7 +174,6 @@ public function get_form_elements($submission, MoodleQuickForm $mform, stdClass
      * @return int
      */
     private function count_files($submissionid, $area) {
-
         $fs = get_file_storage();
         $files = $fs->get_area_files($this->assignment->get_context()->id,
                                      'assignsubmission_file',
@@ -553,6 +552,19 @@ public function get_external_parameters() {
         );
     }
 
+    /**
+     * Make any controlled links in the submission area read-only for the student.
+     *
+     * @param stdClass $submission the assign_submission record being submitted.
+     * @return void
+     */
+    public function submit_for_grading($submission) {
+        file_prevent_changes_to_external_files($this->assignment->get_context()->id,
+                                               'assignsubmission_file',
+                                               ASSIGNSUBMISSION_FILE_FILEAREA,
+                                               $submission->id);
+    }
+
     /**
      * Return the plugin configs for external functions.
      *

mod/assign/submission/onlinetext/locallib.php

@@ -174,7 +174,7 @@ private function get_edit_options() {
            'maxfiles' => EDITOR_UNLIMITED_FILES,
            'maxbytes' => $this->assignment->get_course()->maxbytes,
            'context' => $this->assignment->get_context(),
-           'return_types' => FILE_INTERNAL | FILE_EXTERNAL
+           'return_types' => (FILE_INTERNAL | FILE_EXTERNAL | FILE_CONTROLLED_LINK)
         );
         return $editoroptions;
     }

mod/data/field/file/field.class.php

@@ -85,7 +85,7 @@ function display_add_field($recordid = 0, $formdata = null) {
         $options->maxfiles  = 1; // Limit to one file for the moment, this may be changed if requested as a feature in the future.
         $options->itemid    = $itemid;
         $options->accepted_types = '*';
-        $options->return_types = FILE_INTERNAL;
+        $options->return_types = FILE_INTERNAL | FILE_CONTROLLED_LINK;
         $options->context = $PAGE->context;
 
         $fm = new form_filemanager($options);
@@ -185,6 +185,8 @@ function update_content($recordid, $value, $name='') {
         $usercontext = context_user::instance($USER->id);
         $files = $fs->get_area_files($this->context->id, 'mod_data', 'content', $content->id, 'itemid, filepath, filename', false);
 
+        file_prevent_changes_to_external_files($this->context->id, 'mod_data', 'content', $content->id);
+
         // We expect no or just one file (maxfiles = 1 option is set for the form_filemanager).
         if (count($files) == 0) {
             $content->content = null;

mod/forum/classes/post_form.php

@@ -50,7 +50,7 @@ public static function attachment_options($forum) {
             'maxbytes' => $maxbytes,
             'maxfiles' => $forum->maxattachments,
             'accepted_types' => '*',
-            'return_types' => FILE_INTERNAL
+            'return_types' => FILE_INTERNAL | FILE_CONTROLLED_LINK
         );
     }
 

mod/forum/lib.php

@@ -559,13 +559,16 @@ function forum_cron() {
                 }
             }
 
+            // We need to prevent changes to controlled links in attachments.
+            $modcontext = context_module::instance($coursemodules[$forumid]->id);
+            file_prevent_changes_to_external_files($modcontext->id, 'mod_forum', 'attachment', $pid);
+
             // Save the Inbound Message datakey here to reduce DB queries later.
             $messageinboundgenerator->set_data($pid);
             $messageinboundhandlers[$pid] = $messageinboundgenerator->fetch_data_key();
 
             // Caching subscribed users of each forum.
             if (!isset($subscribedusers[$forumid])) {
-                $modcontext = context_module::instance($coursemodules[$forumid]->id);
                 if ($subusers = \mod_forum\subscriptions::fetch_subscribed_users($forums[$forumid], 0, $modcontext, 'u.*', true)) {
 
                     foreach ($subusers as $postuser) {

mod/wiki/filesedit.php

@@ -83,7 +83,8 @@
 $data->returnurl = $returnurl;
 $data->subwikiid = $subwiki->id;
 $maxbytes = get_max_upload_file_size($CFG->maxbytes, $COURSE->maxbytes);
-$options = array('subdirs'=>0, 'maxbytes'=>$maxbytes, 'maxfiles'=>-1, 'accepted_types'=>'*', 'return_types'=>FILE_INTERNAL | FILE_REFERENCE);
+$types = FILE_INTERNAL | FILE_REFERENCE | FILE_CONTROLLED_LINK;
+$options = array('subdirs'=>0, 'maxbytes'=>$maxbytes, 'maxfiles'=>-1, 'accepted_types'=>'*', 'return_types'=>$types);
 file_prepare_standard_filemanager($data, 'files', $options, $context, 'mod_wiki', 'attachments', $subwiki->id);
 
 $mform = new mod_wiki_filesedit_form(null, array('data'=>$data, 'options'=>$options));

mod/workshop/locallib.php

@@ -1843,6 +1843,13 @@ public function switch_phase($newphase) {
             workshop_update_grades($workshop);
         }
 
+        if (self::PHASE_ASSESSMENT == $newphase) {
+            file_prevent_changes_to_external_files($this->context, 'mod_workshop', 'submission_content');
+        }
+        if (self::PHASE_EVALUATION == $newphase) {
+            file_prevent_changes_to_external_files($this->context, 'mod_workshop', 'overallfeedback_attachment');
+        }
+
         $DB->set_field('workshop', 'phase', $newphase, array('id' => $this->id));
         $this->phase = $newphase;
         $eventdata = array(
@@ -2512,7 +2519,7 @@ public function submission_attachment_options() {
             'subdirs' => true,
             'maxfiles' => $this->nattachments,
             'maxbytes' => $this->maxbytes,
-            'return_types' => FILE_INTERNAL,
+            'return_types' => FILE_INTERNAL | FILE_CONTROLLED_LINK,
         );
 
         if ($acceptedtypes = self::normalize_file_extensions($this->submissionfiletypes)) {
@@ -2554,7 +2561,7 @@ public function overall_feedback_attachment_options() {
             'subdirs' => 1,
             'maxbytes' => $this->overallfeedbackmaxbytes,
             'maxfiles' => $this->overallfeedbackfiles,
-            'return_types' => FILE_INTERNAL,
+            'return_types' => FILE_INTERNAL | FILE_CONTROLLED_LINK,
         );
 
         if ($acceptedtypes = self::normalize_file_extensions($this->overallfeedbackfiletypes)) {

question/type/essay/renderer.php

@@ -115,7 +115,7 @@ public function files_input(question_attempt $qa, $numallowed,
         $pickeroptions->itemid = $qa->prepare_response_files_draft_itemid(
                 'attachments', $options->context->id);
         $pickeroptions->context = $options->context;
-        $pickeroptions->return_types = FILE_INTERNAL;
+        $pickeroptions->return_types = FILE_INTERNAL | FILE_CONTROLLED_LINK;
 
         $pickeroptions->itemid = $qa->prepare_response_files_draft_itemid(
                 'attachments', $options->context->id);