[ActivityPub] Ensuring federation with other software

ActivityPubPlugin:
- Prevent sending a Delete for an Announce

Activitypub_announce:
- Update announce_to_array to add id, to and cc information to the retrieved object

Activitypub_follow:
- Add id to the arguments of follow_to_array, useful for Accept-Follow activities

Activitypub_notice:
- Fix notice validation, url isn't a MUST

Activitypub_inbox_handler:
- Make handle_follow use the received activity id for the later Accept-Follow

Activitypub_postman:
- Fix call to the updated announce_to_array
- Fix successive unnecessary calls to ActivityPubPlugin::actor_uri()

plugins/ActivityPub/ActivityPubPlugin.php

@@ -747,10 +747,12 @@ class ActivityPubPlugin extends Plugin
             return true;
         }
 
-        // The deleting user must have permission to do so, but
-        // it still doesn't own the notitce, so we just need to
-        // handle things locally
-        if (!$notice->isLocal()) {
+        // We handle things locally either because:
+        // 1. the deleting user has special permissions to do so,
+        //    but still doesn't own the notice
+        // 2. the notice is an announce, and there's no undo-share
+        //    logic in GS's AP implementation
+        if (!$notice->isLocal() || $notice->isRepeat()) {
             return true;
         }
 

plugins/ActivityPub/classes/Activitypub_announce.php

@@ -39,18 +39,31 @@ class Activitypub_announce extends Managed_DataObject
     /**
      * Generates an ActivityPub representation of a Announce
      *
-     * @param $actor
-     * @param array $object
+     * @param Profile $actor
+     * @param Notice $notice
      * @return array pretty array to be used in a response
      * @author Diogo Cordeiro <diogo@fc.up.pt>
      */
-    public static function announce_to_array($actor, $object)
+    public static function announce_to_array(Profile $actor, Notice $notice): array
     {
+        $actor_uri = ActivityPubPlugin::actor_uri($actor);
+        $notice_url = Activitypub_notice::getUrl($notice);
+
+        $to = [common_local_url('apActorFollowers', ['id' => $actor->getID()])];
+        foreach ($notice->getAttentionProfiles() as $to_profile) {
+            $to[] = $to_profile->getUri();
+        }
+
+        $cc[]= 'https://www.w3.org/ns/activitystreams#Public';
+
         $res = [
             '@context' => 'https://www.w3.org/ns/activitystreams',
+            'id'     => common_root_url().'share_from_'.urlencode($actor_uri).'_to_'.urlencode($notice_url),
             "type"   => "Announce",
-            "actor"  => $actor,
-            "object" => $object
+            "actor"  => $actor_uri,
+            "object" => $notice_url,
+            "to"     => $to,
+            "cc"     => $cc
         ];
         return $res;
     }

plugins/ActivityPub/classes/Activitypub_follow.php

@@ -42,13 +42,18 @@ class Activitypub_follow extends Managed_DataObject
      * @author Diogo Cordeiro <diogo@fc.up.pt>
      * @param string $actor
      * @param string $object
+     * @param string|null $id Activity id, to be used when generating for an Accept Activity
      * @return array pretty array to be used in a response
      */
-    public static function follow_to_array($actor, $object)
+    public static function follow_to_array(string $actor, string $object, ?string $id = null): array
     {
+        if ($id === null) {
+            $id = common_root_url().'follow_from_'.urlencode($actor).'_to_'.urlencode($object);
+        }
+
         $res = [
             '@context' => 'https://www.w3.org/ns/activitystreams',
-            'id'     => common_root_url().'follow_from_'.urlencode($actor).'_to_'.urlencode($object),
+            'id'     => $id,
             'type'   => 'Follow',
             'actor'  => $actor,
             'object' => $object
@@ -61,13 +66,14 @@ class Activitypub_follow extends Managed_DataObject
      *
      * @param Profile $actor_profile Remote Actor
      * @param string $object Local Actor
+     * @param string $id Activity id
      * @throws AlreadyFulfilledException
      * @throws HTTP_Request2_Exception
      * @throws NoProfileException
      * @throws ServerException
      * @author Diogo Cordeiro <diogo@fc.up.pt>
      */
-    public static function follow($actor_profile, $object)
+    public static function follow(Profile $actor_profile, string $object, string $id)
     {
         // Get Actor's Aprofile
         $actor_aprofile = Activitypub_profile::from_profile($actor_profile);
@@ -87,6 +93,6 @@ class Activitypub_follow extends Managed_DataObject
         // Notify remote instance that we have accepted their request
         common_debug('ActivityPubPlugin: Notifying remote instance that we have accepted their Follow request request from '.ActivityPubPlugin::actor_uri($actor_profile).' to '.$object);
         $postman = new Activitypub_postman($object_profile, [$actor_aprofile]);
-        $postman->accept_follow();
+        $postman->accept_follow($id);
     }
 }

plugins/ActivityPub/classes/Activitypub_notice.php

@@ -77,7 +77,7 @@ class Activitypub_notice extends Managed_DataObject
             'published'    => str_replace(' ', 'T', $notice->getCreated()).'Z',
             'url'          => self::getUrl($notice),
             'attributedTo' => ActivityPubPlugin::actor_uri($profile),
-            'to'           => ['https://www.w3.org/ns/activitystreams#Public'],
+            'to'           => $to,
             'cc'           => $cc,
             'conversation' => $notice->getConversationUrl(),
             'content'      => $notice->getRendered(),
@@ -235,9 +235,7 @@ class Activitypub_notice extends Managed_DataObject
             common_debug('ActivityPub Notice Validator: Rejected because Content was not specified.');
             throw new Exception('Object content was not specified.');
         }
-        if (!isset($object['url'])) {
-            throw new Exception('Object URL was not specified.');
-        } elseif (!filter_var($object['url'], FILTER_VALIDATE_URL)) {
+        if (isset($object['url']) && !filter_var($object['url'], FILTER_VALIDATE_URL)) {
             common_debug('ActivityPub Notice Validator: Rejected because Object URL is invalid.');
             throw new Exception('Invalid Object URL.');
         }

plugins/ActivityPub/lib/inbox_handler.php

@@ -129,7 +129,7 @@ class Activitypub_inbox_handler
                 $this->handle_delete($this->actor, $this->object);
                 break;
             case 'Follow':
-                $this->handle_follow($this->actor, $this->object);
+                $this->handle_follow($this->actor, $this->activity);
                 break;
             case 'Like':
                 $this->handle_like($this->actor, $this->object);
@@ -232,7 +232,7 @@ class Activitypub_inbox_handler
      * Handles a Follow Activity received by our inbox.
      *
      * @param Profile $actor Actor
-     * @param array $object Activity
+     * @param array $activity Activity
      * @throws AlreadyFulfilledException
      * @throws HTTP_Request2_Exception
      * @throws NoProfileException
@@ -241,9 +241,9 @@ class Activitypub_inbox_handler
      * @throws \HttpSignatures\Exception
      * @author Diogo Cordeiro <diogo@fc.up.pt>
      */
-    private function handle_follow($actor, $object)
+    private function handle_follow($actor, $activity)
     {
-        Activitypub_follow::follow($actor, $object);
+        Activitypub_follow::follow($actor, $activity['object'], $activity['id']);
     }
 
     /**

plugins/ActivityPub/lib/postman.php

@@ -119,7 +119,7 @@ class Activitypub_postman
      */
     public function follow()
     {
-        $data = Activitypub_follow::follow_to_array(ActivityPubPlugin::actor_uri($this->actor), $this->to[0]->getUrl());
+        $data = Activitypub_follow::follow_to_array($this->actor_uri, $this->to[0]->getUrl());
         $res = $this->send(json_encode($data, JSON_UNESCAPED_SLASHES), $this->to[0]->get_inbox());
         $res_body = json_decode($res->getBody());
 
@@ -149,7 +149,7 @@ class Activitypub_postman
     {
         $data = Activitypub_undo::undo_to_array(
             Activitypub_follow::follow_to_array(
-                ActivityPubPlugin::actor_uri($this->actor),
+                $this->actor_uri,
                 $this->to[0]->getUrl()
                     )
                 );
@@ -171,23 +171,21 @@ class Activitypub_postman
     /**
      * Send a Accept Follow notification to remote instance
      *
+     * @param string $id Follow activity id
      * @return bool
      * @throws HTTP_Request2_Exception
-     * @throws Exception
-     * @throws Exception
-     * @throws Exception
-     * @throws Exception
+     * @throws Exception Description of HTTP Response error or generic error message.
      * @author Diogo Cordeiro <diogo@fc.up.pt>
      */
-    public function accept_follow()
+    public function accept_follow(string $id): bool
     {
         $data = Activitypub_accept::accept_to_array(
             Activitypub_follow::follow_to_array(
                 $this->to[0]->getUrl(),
-                ActivityPubPlugin::actor_uri($this->actor)
-
-                    )
-               );
+                $this->actor_uri,
+                $id
+                )
+            );
         $res = $this->send(json_encode($data, JSON_UNESCAPED_SLASHES), $this->to[0]->get_inbox());
         $res_body = json_decode($res->getBody());
 
@@ -214,7 +212,7 @@ class Activitypub_postman
     public function like($notice)
     {
         $data = Activitypub_like::like_to_array(
-            ActivityPubPlugin::actor_uri($this->actor),
+            $this->actor_uri,
             Activitypub_notice::getUrl($notice)
                 );
         $data = json_encode($data, JSON_UNESCAPED_SLASHES);
@@ -248,7 +246,7 @@ class Activitypub_postman
     {
         $data = Activitypub_undo::undo_to_array(
             Activitypub_like::like_to_array(
-                ActivityPubPlugin::actor_uri($this->actor),
+                $this->actor_uri,
                 Activitypub_notice::getUrl($notice)
                          )
                 );
@@ -314,11 +312,8 @@ class Activitypub_postman
      */
     public function announce($notice)
     {
-        $data = Activitypub_announce::announce_to_array(
-            ActivityPubPlugin::actor_uri($this->actor),
-            Activitypub_notice::getUrl($notice)
-                        );
-        $data = json_encode($data, JSON_UNESCAPED_SLASHES);
+        $data = json_encode(Activitypub_announce::announce_to_array($this->actor, $notice),
+                            JSON_UNESCAPED_SLASHES);
 
         foreach ($this->to_inbox() as $inbox) {
             $res = $this->send($data, $inbox);