From fdf9d2c0d74770f70525963d7b0c4e1f1612e37c Mon Sep 17 00:00:00 2001
From: Juan Segarra Montesinos <juan.segarra@uji.es>
Date: Tue, 27 Oct 2020 19:07:28 +0100
Subject: [PATCH] MDL-69797 core_grades: Implement authorization into fetch
 method

---
 .../gradingpanel/point/external/fetch.php     |  8 ++-
 ...gradingpanel_point_external_fetch_test.php | 52 +++++++++++++++++--
 2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/grade/classes/grades/grader/gradingpanel/point/external/fetch.php b/grade/classes/grades/grader/gradingpanel/point/external/fetch.php
index 5feb55da73f9b..2f9dad593f9b3 100644
--- a/grade/classes/grades/grader/gradingpanel/point/external/fetch.php
+++ b/grade/classes/grades/grader/gradingpanel/point/external/fetch.php
@@ -128,7 +128,13 @@ public static function execute(string $component, int $contextid, string $itemna
         }
 
         // Fetch the actual data.
-        $gradeduser = \core_user::get_user($gradeduserid);
+        $gradeduser = \core_user::get_user($gradeduserid, '*', MUST_EXIST);
+
+        // One can access its own grades. Others just if they're graders.
+        if ($gradeduserid != $USER->id) {
+            $gradeitem->require_user_can_grade($gradeduser, $USER);
+        }
+
         $hasgrade = $gradeitem->user_has_grade($gradeduser);
         $grade = $gradeitem->get_grade_for_user($gradeduser, $USER);
         $maxgrade = (int) $gradeitem->get_grade_item()->grademax;
diff --git a/grade/tests/grades_grader_gradingpanel_point_external_fetch_test.php b/grade/tests/grades_grader_gradingpanel_point_external_fetch_test.php
index 66db17e7d0a05..cc0aa9a0f61b5 100644
--- a/grade/tests/grades_grader_gradingpanel_point_external_fetch_test.php
+++ b/grade/tests/grades_grader_gradingpanel_point_external_fetch_test.php
@@ -149,14 +149,60 @@ public function test_execute_fetch_graded(): void {
         $course = $forum->get_course_record();
         $teacher = $this->getDataGenerator()->create_and_enrol($course, 'teacher');
         $student = $this->getDataGenerator()->create_and_enrol($course, 'student');
-        $this->setUser($teacher);
+
+        $this->execute_and_assert_fetch($forum, $teacher, $teacher, $student);
+    }
+
+    /**
+     * Class mates should not get other's grades.
+     */
+    public function test_execute_fetch_does_not_return_data_to_other_students(): void {
+        $this->resetAfterTest();
+
+        $forum = $this->get_forum_instance([
+            // Negative numbers mean a scale.
+            'grade_forum' => 5,
+        ]);
+        $course = $forum->get_course_record();
+        $teacher = $this->getDataGenerator()->create_and_enrol($course, 'teacher');
+        $student = $this->getDataGenerator()->create_and_enrol($course, 'student');
+        $evilstudent = $this->getDataGenerator()->create_and_enrol($course, 'student');
+
+        $this->expectException(\required_capability_exception::class);
+        $this->execute_and_assert_fetch($forum, $evilstudent, $teacher, $student);
+    }
+
+    /**
+     * Grades can be returned to graded user.
+     */
+    public function test_execute_fetch_return_data_to_graded_user(): void {
+        $this->resetAfterTest();
+
+        $forum = $this->get_forum_instance([
+            // Negative numbers mean a scale.
+            'grade_forum' => 5,
+        ]);
+        $course = $forum->get_course_record();
+        $teacher = $this->getDataGenerator()->create_and_enrol($course, 'teacher');
+        $student = $this->getDataGenerator()->create_and_enrol($course, 'student');
+
+        $this->execute_and_assert_fetch($forum, $student, $teacher, $student);
+    }
+
+    /**
+     * Executes the fetch method with the given users and returns the result.
+     */
+    private function execute_and_assert_fetch ($forum, $fetcheruser, $grader, $gradeduser) {
+        $this->setUser($grader);
 
         $gradeitem = component_gradeitem::instance('mod_forum', $forum->get_context(), 'forum');
-        $gradeitem->store_grade_from_formdata($student, $teacher, (object) [
+        $gradeitem->store_grade_from_formdata($gradeduser, $grader, (object) [
             'grade' => 4,
         ]);
 
-        $result = fetch::execute('mod_forum', (int) $forum->get_context()->id, 'forum', (int) $student->id);
+        $this->setUser($fetcheruser);
+
+        $result = fetch::execute('mod_forum', (int) $forum->get_context()->id, 'forum', (int) $gradeduser->id);
         $result = external_api::clean_returnvalue(fetch::execute_returns(), $result);
 
         $this->assertIsArray($result);