[ActivityPub] Fix handling of Delete Activity

inbox_handler:
- Call stronger validation method for Delete Activity objects
- Take into account mixed object in handle_delete

Activitypub_delete:
- Add validation method for Delete Activity objects

plugins/ActivityPub/classes/Activitypub_delete.php

@@ -39,12 +39,12 @@ class Activitypub_delete extends Managed_DataObject
     /**
      * Generates an ActivityPub representation of a Delete
      *
-     * @param $actor
+     * @param string $actor actor URI
-     * @param array $object
+     * @param string $object object URI
      * @return array pretty array to be used in a response
      * @author Diogo Cordeiro <diogo@fc.up.pt>
      */
-    public static function delete_to_array($actor, $object)
+    public static function delete_to_array(string $actor, string $object): array
     {
         $res = [
             '@context' => 'https://www.w3.org/ns/activitystreams',
@@ -55,4 +55,33 @@ class Activitypub_delete extends Managed_DataObject
         ];
         return $res;
     }
+
+    /**
+     * Verifies if a given object is acceptable for a Delete Activity.
+     *
+     * @param array|string $object
+     * @return bool
+     * @throws Exception
+     * @author Bruno Casteleiro <brunoccast@fc.up.pt>
+     */
+    public static function validate_object($object): bool
+    {
+        if (!is_array($object)) {
+            if (!filter_var($object, FILTER_VALIDATE_URL)) {
+                throw new Exception('Object is not a valid Object URI for Activity.');
+            }
+        } else {
+            if (!isset($object['type'])) {
+                throw new Exception('Object type was not specified for Delete Activity.');
+            } else if ($object['type'] !== "Tombstone") {
+                throw new Exception('Invalid Object type for Delete Activity.');
+            }
+
+            if (!isset($object['id'])) {
+                throw new Exception('Object id was not specified for Delete Activity.');
+            }
+        }
+
+        return true;
+    }
 }

plugins/ActivityPub/lib/inbox_handler.php

@@ -96,6 +96,8 @@ class Activitypub_inbox_handler
                 Activitypub_create::validate_object($this->object);
                 break;
             case 'Delete':
+                Activitypub_delete::validate_object($this->object);
+                break;
             case 'Follow':
             case 'Like':
             case 'Announce':
@@ -207,12 +209,16 @@ class Activitypub_inbox_handler
      * Handles a Delete Activity received by our inbox.
      *
      * @param Profile $actor Actor
-     * @param array $object Activity
+     * @param array|string $object Activity's object
      * @throws AuthorizationException
      * @author Diogo Cordeiro <diogo@fc.up.pt>
      */
-    private function handle_delete($actor, $object)
+    private function handle_delete(Profile $actor, $object)
     {
+        if (is_array($object)) {
+            $object = $object['id'];
+        }
+
         // some moderator could already have deleted the
         // notice, so we test it first
         try {