]> git.mxchange.org Git - friendica.git/blobdiff - src/Protocol/ActivityPub/Receiver.php
Merge remote-tracking branch 'upstream/develop' into untrusted
[friendica.git] / src / Protocol / ActivityPub / Receiver.php
index 4504cee4c49367b7e587d0b2d767ba21a0e55aff..66653579ea7f6739b0250dfbe373699f9cf7ed94 100644 (file)
@@ -27,6 +27,8 @@ use Friendica\Content\Text\HTML;
 use Friendica\Content\Text\Markdown;
 use Friendica\Core\Logger;
 use Friendica\Core\Protocol;
+use Friendica\Core\System;
+use Friendica\DI;
 use Friendica\Model\Contact;
 use Friendica\Model\APContact;
 use Friendica\Model\Item;
@@ -37,6 +39,7 @@ use Friendica\Protocol\ActivityPub;
 use Friendica\Util\HTTPSignature;
 use Friendica\Util\JsonLD;
 use Friendica\Util\LDSignature;
+use Friendica\Util\Network;
 use Friendica\Util\Strings;
 
 /**
@@ -68,15 +71,22 @@ class Receiver
        const TARGET_ANSWER = 6;
        const TARGET_GLOBAL = 7;
 
+       const COMPLETION_NONE    = 0;
+       const COMPLETION_ANNOUCE = 1;
+       const COMPLETION_RELAY   = 2;
+       const COMPLETION_MANUAL  = 3;
+       const COMPLETION_AUTO    = 4;
+
        /**
         * Checks incoming message from the inbox
         *
-        * @param         $body
-        * @param         $header
+        * @param string  $body Body string
+        * @param array   $header Header lines
         * @param integer $uid User ID
+        * @return void
         * @throws \Exception
         */
-       public static function processInbox($body, $header, $uid)
+       public static function processInbox(string $body, array $header, int $uid)
        {
                $activity = json_decode($body, true);
                if (empty($activity)) {
@@ -86,13 +96,14 @@ class Receiver
 
                $ldactivity = JsonLD::compact($activity);
 
-               $actor = JsonLD::fetchElement($ldactivity, 'as:actor', '@id');
+               $actor = JsonLD::fetchElement($ldactivity, 'as:actor', '@id') ?? '';
 
                $apcontact = APContact::getByURL($actor);
+
                if (empty($apcontact)) {
                        Logger::notice('Unable to retrieve AP contact for actor - message is discarded', ['actor' => $actor]);
                        return;
-               } elseif ($apcontact['type'] == 'Application' && $apcontact['nick'] == 'relay') {
+               } elseif (APContact::isRelay($apcontact)) {
                        self::processRelayPost($ldactivity, $actor);
                        return;
                } else {
@@ -142,7 +153,7 @@ class Receiver
                        $trust_source = false;
                }
 
-               self::processActivity($ldactivity, $body, $uid, $trust_source, true, $signer);
+               self::processActivity($ldactivity, $body, $uid, $trust_source, true, $signer, $http_signer);
        }
 
        /**
@@ -156,18 +167,18 @@ class Receiver
        {
                $type = JsonLD::fetchElement($activity, '@type');
                if (!$type) {
-                       Logger::info('Empty type', ['activity' => $activity]);
+                       Logger::info('Empty type', ['activity' => $activity, 'actor' => $actor]);
                        return;
                }
 
                if ($type != 'as:Announce') {
-                       Logger::info('Not an announcement', ['activity' => $activity]);
+                       Logger::info('Not an announcement', ['activity' => $activity, 'actor' => $actor]);
                        return;
                }
 
                $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
                if (empty($object_id)) {
-                       Logger::info('No object id found', ['activity' => $activity]);
+                       Logger::info('No object id found', ['activity' => $activity, 'actor' => $actor]);
                        return;
                }
 
@@ -182,25 +193,25 @@ class Receiver
                        return;
                }
 
-               Logger::info('Got relayed message id', ['id' => $object_id]);
+               Logger::info('Got relayed message id', ['id' => $object_id, 'actor' => $actor]);
 
                $item_id = Item::searchByLink($object_id);
                if ($item_id) {
-                       Logger::info('Relayed message already exists', ['id' => $object_id, 'item' => $item_id]);
+                       Logger::info('Relayed message already exists', ['id' => $object_id, 'item' => $item_id, 'actor' => $actor]);
                        return;
                }
 
-               $id = Processor::fetchMissingActivity($object_id, [], $actor);
+               $id = Processor::fetchMissingActivity($object_id, [], $actor, self::COMPLETION_RELAY);
                if (empty($id)) {
-                       Logger::notice('Relayed message had not been fetched', ['id' => $object_id]);
+                       Logger::notice('Relayed message had not been fetched', ['id' => $object_id, 'actor' => $actor]);
                        return;
                }
 
                $item_id = Item::searchByLink($object_id);
                if ($item_id) {
-                       Logger::info('Relayed message had been fetched and stored', ['id' => $object_id, 'item' => $item_id]);
+                       Logger::info('Relayed message had been fetched and stored', ['id' => $object_id, 'item' => $item_id, 'actor' => $actor]);
                } else {
-                       Logger::notice('Relayed message had not been stored', ['id' => $object_id]);
+                       Logger::notice('Relayed message had not been stored', ['id' => $object_id, 'actor' => $actor]);
                }
        }
 
@@ -211,11 +222,11 @@ class Receiver
         * @param string  $object_id Object ID of the the provided object
         * @param integer $uid       User ID
         *
-        * @return string with object type
+        * @return string with object type or NULL
         * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         * @throws \ImagickException
         */
-       private static function fetchObjectType($activity, $object_id, $uid = 0)
+       private static function fetchObjectType(array $activity, string $object_id, int $uid = 0)
        {
                if (!empty($activity['as:object'])) {
                        $object_type = JsonLD::fetchElement($activity['as:object'], '@type');
@@ -259,18 +270,28 @@ class Receiver
         * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         * @throws \ImagickException
         */
-       public static function prepareObjectData($activity, $uid, $push, &$trust_source)
+       public static function prepareObjectData(array $activity, int $uid, bool $push, bool &$trust_source): array
        {
                $id = JsonLD::fetchElement($activity, '@id');
+               $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
+
                if (!empty($id) && !$trust_source) {
-                       $fetched_activity = ActivityPub::fetchContent($id, $uid ?? 0);
+                       $fetch_uid = $uid ?: self::getBestUserForActivity($activity);
+
+                       $fetched_activity = ActivityPub::fetchContent($id, $fetch_uid);
                        if (!empty($fetched_activity)) {
                                $object = JsonLD::compact($fetched_activity);
                                $fetched_id = JsonLD::fetchElement($object, '@id');
                                if ($fetched_id == $id) {
                                        Logger::info('Activity had been fetched successfully', ['id' => $id]);
                                        $trust_source = true;
-                                       $activity = $object;
+                                       if ($id != $object_id) {
+                                               $activity = $object;
+                                       } else {
+                                               Logger::info('Fetched data is the object instead of the activity', ['id' => $id]);
+                                               unset($object['@context']);
+                                               $activity['as:object'] = $object;
+                                       }
                                } else {
                                        Logger::info('Activity id is not equal', ['id' => $id, 'fetched' => $fetched_id]);
                                }
@@ -295,19 +316,25 @@ class Receiver
                        $reception_types[$data['uid']] = $data['type'] ?? self::TARGET_UNKNOWN;
                }
 
+               $urls = self::getReceiverURL($activity);
+
                // When it is a delivery to a personal inbox we add that user to the receivers
                if (!empty($uid)) {
                        $additional = [$uid => $uid];
                        $receivers = array_replace($receivers, $additional);
                        if (empty($activity['thread-completion']) && (empty($reception_types[$uid]) || in_array($reception_types[$uid], [self::TARGET_UNKNOWN, self::TARGET_FOLLOWER, self::TARGET_ANSWER, self::TARGET_GLOBAL]))) {
                                $reception_types[$uid] = self::TARGET_BCC;
+                               $owner = User::getOwnerDataById($uid);
+                               if (!empty($owner['url'])) {
+                                       $urls['as:bcc'][] = $owner['url'];
+                               }
                        }
-               } else {
-                       // We possibly need some user to fetch private content,
-                       // so we fetch the first out ot the list.
-                       $uid = self::getFirstUserFromReceivers($receivers);
                }
 
+               // We possibly need some user to fetch private content,
+               // so we fetch one out of the receivers if no uid is provided.
+               $fetch_uid = $uid ?: self::getBestUserForActivity($activity);
+
                $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
                if (empty($object_id)) {
                        Logger::info('No object found');
@@ -319,11 +346,11 @@ class Receiver
                        return [];
                }
 
-               $object_type = self::fetchObjectType($activity, $object_id, $uid);
+               $object_type = self::fetchObjectType($activity, $object_id, $fetch_uid);
 
                // Fetch the activity on Lemmy "Announce" messages (announces of activities)
                if (($type == 'as:Announce') && in_array($object_type, array_merge(self::ACTIVITY_TYPES, ['as:Delete', 'as:Undo', 'as:Update']))) {
-                       $data = ActivityPub::fetchContent($object_id, $uid);
+                       $data = ActivityPub::fetchContent($object_id, $fetch_uid);
                        if (!empty($data)) {
                                $type = $object_type;
                                $activity = JsonLD::compact($data);
@@ -331,7 +358,7 @@ class Receiver
                                // Some variables need to be refetched since the activity changed
                                $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
                                $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
-                               $object_type = self::fetchObjectType($activity, $object_id, $uid);
+                               $object_type = self::fetchObjectType($activity, $object_id, $fetch_uid);
                        }
                }
 
@@ -344,11 +371,15 @@ class Receiver
                        $object_data['object_object'] = JsonLD::fetchElement($activity['as:object'], 'as:object');
                        $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
                        $object_data['push'] = $push;
-               } elseif (in_array($type, ['as:Create', 'as:Update', 'as:Announce']) || strpos($type, '#emojiReaction')) {
-               // Fetch the content only on activities where this matters
-               // We can receive "#emojiReaction" when fetching content from Hubzilla systems
+                       if ($type == 'as:Delete') {
+                               $apcontact = APContact::getByURL($object_data['object_id'], true);
+                               $trust_source = ($apcontact['type'] == 'Tombstone');
+                       }
+               } elseif (in_array($type, ['as:Create', 'as:Update', 'as:Announce', 'as:Invite']) || strpos($type, '#emojiReaction')) {
+                       // Fetch the content only on activities where this matters
+                       // We can receive "#emojiReaction" when fetching content from Hubzilla systems
                        // Always fetch on "Announce"
-                       $object_data = self::fetchObject($object_id, $activity['as:object'], $trust_source && ($type != 'as:Announce'), $uid);
+                       $object_data = self::fetchObject($object_id, $activity['as:object'], $trust_source && ($type != 'as:Announce'), $fetch_uid);
                        if (empty($object_data)) {
                                Logger::info("Object data couldn't be processed");
                                return [];
@@ -368,7 +399,7 @@ class Receiver
                        } else {
                                $object_data['directmessage'] = JsonLD::fetchElement($activity, 'litepub:directMessage');
                        }
-               } elseif (in_array($type, array_merge(self::ACTIVITY_TYPES, ['as:Follow'])) && in_array($object_type, self::CONTENT_TYPES)) {
+               } elseif (in_array($type, array_merge(self::ACTIVITY_TYPES, ['as:Follow', 'litepub:EmojiReact', 'as:View'])) && in_array($object_type, self::CONTENT_TYPES)) {
                        // Create a mostly empty array out of the activity data (instead of the object).
                        // This way we later don't have to check for the existence of each individual array element.
                        $object_data = self::processObject($activity);
@@ -377,7 +408,7 @@ class Receiver
                        $object_data['object_id'] = $object_id;
                        $object_data['object_type'] = ''; // Since we don't fetch the object, we don't know the type
                        $object_data['push'] = $push;
-               } elseif (in_array($type, ['as:Add'])) {
+               } elseif (in_array($type, ['as:Add', 'as:Remove'])) {
                        $object_data = [];
                        $object_data['id'] = JsonLD::fetchElement($activity, '@id');
                        $object_data['target_id'] = JsonLD::fetchElement($activity, 'as:target', '@id');
@@ -396,7 +427,11 @@ class Receiver
 
                        // An Undo is done on the object of an object, so we need that type as well
                        if (($type == 'as:Undo') && !empty($object_data['object_object'])) {
-                               $object_data['object_object_type'] = self::fetchObjectType([], $object_data['object_object'], $uid);
+                               $object_data['object_object_type'] = self::fetchObjectType([], $object_data['object_object'], $fetch_uid);
+                       }
+
+                       if (($type == 'as:Delete') && in_array($object_data['object_type'], array_merge(['as:Tombstone'], self::CONTENT_TYPES))) {
+                               $trust_source = Processor::isActivityGone($object_data['object_id']);
                        }
                }
 
@@ -406,23 +441,30 @@ class Receiver
                        $object_data['object_type'] = $object_type;
                }
 
+               foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
+                       if ((empty($object_data['receiver_urls'][$element]) || in_array($element, ['as:bto', 'as:bcc'])) && !empty($urls[$element])) {
+                               $object_data['receiver_urls'][$element] = array_unique(array_merge($object_data['receiver_urls'][$element] ?? [], $urls[$element]));
+                       }
+               }
+
                $object_data['type'] = $type;
                $object_data['actor'] = $actor;
                $object_data['item_receiver'] = $receivers;
                $object_data['receiver'] = array_replace($object_data['receiver'] ?? [], $receivers);
                $object_data['reception_type'] = array_replace($object_data['reception_type'] ?? [], $reception_types);
 
-               $author = $object_data['author'] ?? $actor;
-               if (!empty($author) && !empty($object_data['id'])) {
-                       $author_host = parse_url($author, PHP_URL_HOST);
-                       $id_host = parse_url($object_data['id'], PHP_URL_HOST);
-                       if ($author_host == $id_host) {
-                               Logger::info('Valid hosts', ['type' => $type, 'host' => $id_host]);
-                       } else {
-                               Logger::notice('Differing hosts on author and id', ['type' => $type, 'author' => $author_host, 'id' => $id_host]);
-                               $trust_source = false;
-                       }
-               }
+//             This check here interferes with Hubzilla posts where the author host differs from the host the post was created
+//             $author = $object_data['author'] ?? $actor;
+//             if (!empty($author) && !empty($object_data['id'])) {
+//                     $author_host = parse_url($author, PHP_URL_HOST);
+//                     $id_host = parse_url($object_data['id'], PHP_URL_HOST);
+//                     if ($author_host == $id_host) {
+//                             Logger::info('Valid hosts', ['type' => $type, 'host' => $id_host]);
+//                     } else {
+//                             Logger::notice('Differing hosts on author and id', ['type' => $type, 'author' => $author_host, 'id' => $id_host]);
+//                             $trust_source = false;
+//                     }
+//             }
 
                Logger::info('Processing ' . $object_data['type'] . ' ' . $object_data['object_type'] . ' ' . $object_data['id']);
 
@@ -435,7 +477,7 @@ class Receiver
         * @param array $receivers Array with receivers
         * @return integer user id;
         */
-       public static function getFirstUserFromReceivers($receivers)
+       public static function getFirstUserFromReceivers(array $receivers): int
        {
                foreach ($receivers as $receiver) {
                        if (!empty($receiver)) {
@@ -448,14 +490,16 @@ class Receiver
        /**
         * Processes the activity object
         *
-        * @param array   $activity     Array with activity data
-        * @param string  $body
-        * @param integer $uid          User ID
-        * @param boolean $trust_source Do we trust the source?
-        * @param boolean $push         Message had been pushed to our system
-        * @throws \Exception
+        * @param array      $activity     Array with activity data
+        * @param string     $body         The unprocessed body
+        * @param int|null   $uid          User ID
+        * @param boolean    $trust_source Do we trust the source?
+        * @param boolean    $push         Message had been pushed to our system
+        * @param array      $signer       The signer of the post
+        * @throws \Friendica\Network\HTTPException\InternalServerErrorException
+        * @throws \ImagickException
         */
-       public static function processActivity($activity, string $body = '', int $uid = null, bool $trust_source = false, bool $push = false, array $signer = [])
+       public static function processActivity(array $activity, string $body = '', int $uid = null, bool $trust_source = false, bool $push = false, array $signer = [], string $http_signer = '')
        {
                $type = JsonLD::fetchElement($activity, '@type');
                if (!$type) {
@@ -502,11 +546,6 @@ class Receiver
                        $type = $object_data['type'];
                }
 
-               if (!$trust_source) {
-                       Logger::info('Activity trust could not be achieved.',  ['id' => $object_data['object_id'], 'type' => $type, 'signer' => $signer, 'actor' => $actor, 'attributedTo' => $attributed_to]);
-                       return;
-               }
-
                if (!empty($body) && empty($object_data['raw'])) {
                        $object_data['raw'] = $body;
                }
@@ -516,67 +555,153 @@ class Receiver
                        $object_data['thread-completion'] = $activity['thread-completion'];
                }
 
+               if (!empty($activity['completion-mode'])) {
+                       $object_data['completion-mode'] = $activity['completion-mode'];
+               }
+
+               if (!empty($activity['thread-children-type'])) {
+                       $object_data['thread-children-type'] = $activity['thread-children-type'];
+               }
+
                // Internal flag for posts that arrived via relay
                if (!empty($activity['from-relay'])) {
                        $object_data['from-relay'] = $activity['from-relay'];
                }
 
+               if ($type == 'as:Announce') {
+                       $object_data['object_activity'] = $activity;
+               }
+
+               if ($trust_source || DI::config()->get('debug', 'ap_inbox_store_untrusted')) {
+                       $object_data = Queue::add($object_data, $type, $uid, $http_signer, $push, $trust_source);
+               }
+
+               if (!$trust_source) {
+                       Logger::info('Activity trust could not be achieved.',  ['id' => $object_data['object_id'], 'type' => $type, 'signer' => $signer, 'actor' => $actor, 'attributedTo' => $attributed_to]);
+                       return;
+               }
+
+               if (!empty($activity['recursion-depth'])) {
+                       $object_data['recursion-depth'] = $activity['recursion-depth'];
+               }
+
+               if (in_array('as:Question', [$object_data['object_type'] ?? '', $object_data['object_object_type'] ?? ''])) {
+                       self::storeUnhandledActivity(false, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+               }
+
+               if (!self::routeActivities($object_data, $type, $push)) {
+                       self::storeUnhandledActivity(true, $type, $object_data, $activity, $body, $uid, $trust_source, $push, $signer);
+                       Queue::remove($object_data);
+               }
+       }
+
+       /**
+        * Route activities
+        *
+        * @param array   $object_data
+        * @param string  $type
+        * @param boolean $push
+        *
+        * @return boolean Could the activity be routed?
+        */
+       public static function routeActivities(array $object_data, string $type, bool $push): bool
+       {
+               $activity = $object_data['object_activity']     ?? [];
+
                switch ($type) {
                        case 'as:Create':
                                if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
                                        $item = ActivityPub\Processor::createItem($object_data);
                                        ActivityPub\Processor::postItem($object_data, $item);
+                               } elseif (in_array($object_data['object_type'], ['pt:CacheFile'])) {
+                                       // Unhandled Peertube activity
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
+                               }
+                               break;
+
+                       case 'as:Invite':
+                               if (in_array($object_data['object_type'], ['as:Event'])) {
+                                       $item = ActivityPub\Processor::createItem($object_data);
+                                       ActivityPub\Processor::postItem($object_data, $item);
+                               } else {
+                                       return false;
                                }
                                break;
 
                        case 'as:Add':
                                if ($object_data['object_type'] == 'as:tag') {
                                        ActivityPub\Processor::addTag($object_data);
+                               } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+                                       ActivityPub\Processor::addToFeaturedCollection($object_data);
+                               } elseif ($object_data['object_type'] == '') {
+                                       // The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
                                }
                                break;
 
                        case 'as:Announce':
                                if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+                                       $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
                                        $object_data['thread-completion'] = Contact::getIdForURL($actor);
+                                       $object_data['completion-mode']   = self::COMPLETION_ANNOUCE;
 
                                        $item = ActivityPub\Processor::createItem($object_data);
                                        if (empty($item)) {
-                                               return;
+                                               return false;
                                        }
 
                                        $item['post-reason'] = Item::PR_ANNOUNCEMENT;
                                        ActivityPub\Processor::postItem($object_data, $item);
 
-                                       $announce_object_data = self::processObject($activity);
-                                       $announce_object_data['name'] = $type;
-                                       $announce_object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
-                                       $announce_object_data['object_id'] = $object_data['object_id'];
-                                       $announce_object_data['object_type'] = $object_data['object_type'];
-                                       $announce_object_data['push'] = $push;
+                                       if (!empty($activity)) {
+                                               $announce_object_data = self::processObject($activity);
+                                               $announce_object_data['name'] = $type;
+                                               $announce_object_data['author'] = $actor;
+                                               $announce_object_data['object_id'] = $object_data['object_id'];
+                                               $announce_object_data['object_type'] = $object_data['object_type'];
+                                               $announce_object_data['push'] = $push;
 
-                                       if (!empty($body)) {
-                                               $announce_object_data['raw'] = $body;
+                                               if (!empty($object_data['raw'])) {
+                                                       $announce_object_data['raw'] = $object_data['raw'];
+                                               }
+                                               ActivityPub\Processor::createActivity($announce_object_data, Activity::ANNOUNCE);
                                        }
-
-                                       ActivityPub\Processor::createActivity($announce_object_data, Activity::ANNOUNCE);
+                               } else {
+                                       return false;
                                }
                                break;
 
                        case 'as:Like':
                                if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
                                        ActivityPub\Processor::createActivity($object_data, Activity::LIKE);
+                               } elseif ($object_data['object_type'] == '') {
+                                       // The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
                                }
                                break;
 
                        case 'as:Dislike':
                                if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
                                        ActivityPub\Processor::createActivity($object_data, Activity::DISLIKE);
+                               } elseif ($object_data['object_type'] == '') {
+                                       // The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
                                }
                                break;
 
                        case 'as:TentativeAccept':
                                if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
                                        ActivityPub\Processor::createActivity($object_data, Activity::ATTENDMAYBE);
+                               } else {
+                                       return false;
                                }
                                break;
 
@@ -585,14 +710,43 @@ class Receiver
                                        ActivityPub\Processor::updateItem($object_data);
                                } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
                                        ActivityPub\Processor::updatePerson($object_data);
+                               } elseif (in_array($object_data['object_type'], ['pt:CacheFile'])) {
+                                       // Unhandled Peertube activity
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
                                }
                                break;
 
                        case 'as:Delete':
-                               if ($object_data['object_type'] == 'as:Tombstone') {
+                               if (in_array($object_data['object_type'], array_merge(['as:Tombstone'], self::CONTENT_TYPES))) {
                                        ActivityPub\Processor::deleteItem($object_data);
                                } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
                                        ActivityPub\Processor::deletePerson($object_data);
+                               } elseif ($object_data['object_type'] == '') {
+                                       // The object type couldn't be determined. Most likely we don't have it here. We ignore this activity.
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
+                               }
+                               break;
+
+                       case 'as:Block':
+                               if (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
+                                       ActivityPub\Processor::blockAccount($object_data);
+                               } else {
+                                       return false;
+                               }
+                               break;
+
+                       case 'as:Remove':
+                               if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+                                       ActivityPub\Processor::removeFromFeaturedCollection($object_data);
+                               } elseif ($object_data['object_type'] == '') {
+                                       // The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
                                }
                                break;
 
@@ -602,6 +756,8 @@ class Receiver
                                } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
                                        $object_data['reply-to-id'] = $object_data['object_id'];
                                        ActivityPub\Processor::createActivity($object_data, Activity::FOLLOW);
+                               } else {
+                                       return false;
                                }
                                break;
 
@@ -610,6 +766,8 @@ class Receiver
                                        ActivityPub\Processor::acceptFollowUser($object_data);
                                } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
                                        ActivityPub\Processor::createActivity($object_data, Activity::ATTEND);
+                               } else {
+                                       return false;
                                }
                                break;
 
@@ -618,6 +776,8 @@ class Receiver
                                        ActivityPub\Processor::rejectFollowUser($object_data);
                                } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
                                        ActivityPub\Processor::createActivity($object_data, Activity::ATTENDNO);
+                               } else {
+                                       return false;
                                }
                                break;
 
@@ -625,19 +785,149 @@ class Receiver
                                if (($object_data['object_type'] == 'as:Follow') &&
                                        in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
                                        ActivityPub\Processor::undoFollowUser($object_data);
+                               } elseif (($object_data['object_type'] == 'as:Follow') &&
+                                       in_array($object_data['object_object_type'], self::CONTENT_TYPES)) {
+                                       ActivityPub\Processor::undoActivity($object_data);
                                } elseif (($object_data['object_type'] == 'as:Accept') &&
                                        in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
                                        ActivityPub\Processor::rejectFollowUser($object_data);
-                               } elseif (in_array($object_data['object_type'], self::ACTIVITY_TYPES) &&
-                                       in_array($object_data['object_object_type'], self::CONTENT_TYPES)) {
+                               } elseif (($object_data['object_type'] == 'as:Block') &&
+                                       in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
+                                       ActivityPub\Processor::unblockAccount($object_data);
+                               } elseif (in_array($object_data['object_type'], array_merge(self::ACTIVITY_TYPES, ['as:Announce'])) &&
+                                       in_array($object_data['object_object_type'], array_merge(['as:Tombstone'], self::CONTENT_TYPES))) {
                                        ActivityPub\Processor::undoActivity($object_data);
+                               } elseif (in_array($object_data['object_type'], array_merge(self::ACTIVITY_TYPES, ['as:Announce', 'as:Create', ''])) &&
+                                       empty($object_data['object_object_type'])) {
+                                       // We cannot detect the target object. So we can ignore it.
+                                       Queue::remove($object_data);
+                               } elseif (in_array($object_data['object_type'], ['as:Create']) &&
+                                       in_array($object_data['object_object_type'], ['pt:CacheFile'])) {
+                                       // Unhandled Peertube activity
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
+                               }
+                               break;
+
+                       case 'as:View':
+                               if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+                                       ActivityPub\Processor::createActivity($object_data, Activity::VIEW);
+                               } elseif ($object_data['object_type'] == '') {
+                                       // The object type couldn't be determined. Most likely we don't have it here. We ignore this activity.
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
+                               }
+                               break;
+
+                       case 'litepub:EmojiReact':
+                               if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
+                                       ActivityPub\Processor::createActivity($object_data, Activity::EMOJIREACT);
+                               } elseif ($object_data['object_type'] == '') {
+                                       // The object type couldn't be determined. We don't have it and we can't fetch it. We ignore this activity.
+                                       Queue::remove($object_data);
+                               } else {
+                                       return false;
                                }
                                break;
 
                        default:
                                Logger::info('Unknown activity: ' . $type . ' ' . $object_data['object_type']);
-                               break;
+                               return false;
+               }
+               return true;
+       }
+
+       /**
+        * Stores unhandled or unknown Activities as a file
+        *
+        * @param boolean $unknown      "true" if the activity is unknown, "false" if it is unhandled
+        * @param string  $type         Activity type
+        * @param array   $object_data  Preprocessed array that is generated out of the received activity
+        * @param array   $activity     Array with activity data
+        * @param string  $body         The unprocessed body
+        * @param integer $uid          User ID
+        * @param boolean $trust_source Do we trust the source?
+        * @param boolean $push         Message had been pushed to our system
+        * @param array   $signer       The signer of the post
+        * @return void
+        */
+       private static function storeUnhandledActivity(bool $unknown, string $type, array $object_data, array $activity, string $body = '', int $uid = null, bool $trust_source = false, bool $push = false, array $signer = [])
+       {
+               if (!DI::config()->get('debug', 'ap_log_unknown')) {
+                       return;
                }
+
+               $file = ($unknown  ? 'unknown-' : 'unhandled-') . str_replace(':', '-', $type) . '-';
+
+               if (!empty($object_data['object_type'])) {
+                       $file .= str_replace(':', '-', $object_data['object_type']) . '-';
+               }
+
+               if (!empty($object_data['object_object_type'])) {
+                       $file .= str_replace(':', '-', $object_data['object_object_type']) . '-';
+               }
+
+               $tempfile = tempnam(System::getTempPath(), $file);
+               file_put_contents($tempfile, json_encode(['activity' => $activity, 'body' => $body, 'uid' => $uid, 'trust_source' => $trust_source, 'push' => $push, 'signer' => $signer, 'object_data' => $object_data], JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT));
+               Logger::notice('Unknown activity stored', ['type' => $type, 'object_type' => $object_data['object_type'], $object_data['object_object_type'] ?? '', 'file' => $tempfile]);
+       }
+
+       /**
+        * Fetch a user id from an activity array
+        *
+        * @param array  $activity
+        * @param string $actor
+        *
+        * @return int   user id
+        */
+       public static function getBestUserForActivity(array $activity): int
+       {
+               $uid = 0;
+               $actor = JsonLD::fetchElement($activity, 'as:actor', '@id') ?? '';
+
+               $receivers = self::getReceivers($activity, $actor);
+               foreach ($receivers as $receiver) {
+                       if ($receiver['type'] == self::TARGET_GLOBAL) {
+                               return 0;
+                       }
+                       if (empty($uid) || ($receiver['type'] == self::TARGET_TO)) {
+                               $uid = $receiver['uid'];
+                       }
+               }
+
+               // When we haven't found any user yet, we just chose a user who most likely could have access to the content
+               if (empty($uid)) {
+                       $contact = Contact::selectFirst(['uid'], ['nurl' => Strings::normaliseLink($actor), 'rel' => [Contact::SHARING, Contact::FRIEND]]);
+                       if (!empty($contact['uid'])) {
+                               $uid = $contact['uid'];
+                       }
+               }
+
+               return $uid;
+       }
+
+       // @TODO Missing documentation
+       public static function getReceiverURL(array $activity): array
+       {
+               $urls = [];
+
+               foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
+                       $receiver_list = JsonLD::fetchElementArray($activity, $element, '@id');
+                       if (empty($receiver_list)) {
+                               continue;
+                       }
+
+                       foreach ($receiver_list as $receiver) {
+                               if ($receiver == self::PUBLIC_COLLECTION) {
+                                       $receiver = ActivityPub::PUBLIC_COLLECTION;
+                               }
+                               $urls[$element][] = $receiver;
+                       }
+               }
+
+               return $urls;
        }
 
        /**
@@ -651,9 +941,9 @@ class Receiver
         * @return array with receivers (user id)
         * @throws \Exception
         */
-       private static function getReceivers($activity, $actor, $tags = [], $fetch_unlisted = false)
+       private static function getReceivers(array $activity, string $actor, array $tags = [], bool $fetch_unlisted = false): array
        {
-               $reply = $receivers = [];
+               $reply = $receivers = $profile = [];
 
                // When it is an answer, we inherite the receivers from the parent
                $replyto = JsonLD::fetchElement($activity, 'as:inReplyTo', '@id');
@@ -713,7 +1003,7 @@ class Receiver
 
                                // Fetch the receivers for the public and the followers collection
                                if ((($receiver == $followers) || (($receiver == self::PUBLIC_COLLECTION) && !$is_forum)) && !empty($actor)) {
-                                       $receivers = self::getReceiverForActor($actor, $tags, $receivers, $follower_target);
+                                       $receivers = self::getReceiverForActor($actor, $tags, $receivers, $follower_target, $profile);
                                        continue;
                                }
 
@@ -775,33 +1065,46 @@ class Receiver
         * @param array   $tags
         * @param array   $receivers
         * @param integer $target_type
+        * @param array   $profile
         *
         * @return array with receivers (user id)
         * @throws \Exception
         */
-       private static function getReceiverForActor($actor, $tags, $receivers, $target_type)
+       private static function getReceiverForActor(string $actor, array $tags, array $receivers, int $target_type, array $profile): array
        {
                $basecondition = ['rel' => [Contact::SHARING, Contact::FRIEND, Contact::FOLLOWER],
                        'network' => Protocol::FEDERATED, 'archive' => false, 'pending' => false];
 
-               $condition = DBA::mergeConditions($basecondition, ["`nurl` = ? AND `uid` != ?", Strings::normaliseLink($actor), 0]);
-               $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
-               while ($contact = DBA::fetch($contacts)) {
-                       if (empty($receivers[$contact['uid']]) && self::isValidReceiverForActor($contact, $tags)) {
-                               $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $target_type];
+               if (!empty($profile['uri-id'])) {
+                       $condition = DBA::mergeConditions($basecondition, ["`uri-id` = ? AND `uid` != ?", $profile['uri-id'], 0]);
+                       $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
+                       while ($contact = DBA::fetch($contacts)) {
+                               if (empty($receivers[$contact['uid']]) && self::isValidReceiverForActor($contact, $tags)) {
+                                       $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $target_type];
+                               }
                        }
-               }
-               DBA::close($contacts);
-
-               // The queries are split because of performance issues
-               $condition = DBA::mergeConditions($basecondition, ["`alias` IN (?, ?) AND `uid` != ?", Strings::normaliseLink($actor), $actor, 0]);
-               $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
-               while ($contact = DBA::fetch($contacts)) {
-                       if (empty($receivers[$contact['uid']]) && self::isValidReceiverForActor($contact, $tags)) {
-                               $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $target_type];
+                       DBA::close($contacts);
+               } else {
+                       // This part will only be called while post update 1426 wasn't finished
+                       $condition = DBA::mergeConditions($basecondition, ["`nurl` = ? AND `uid` != ?", Strings::normaliseLink($actor), 0]);
+                       $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
+                       while ($contact = DBA::fetch($contacts)) {
+                               if (empty($receivers[$contact['uid']]) && self::isValidReceiverForActor($contact, $tags)) {
+                                       $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $target_type];
+                               }
                        }
+                       DBA::close($contacts);
+
+                       // The queries are split because of performance issues
+                       $condition = DBA::mergeConditions($basecondition, ["`alias` IN (?, ?) AND `uid` != ?", Strings::normaliseLink($actor), $actor, 0]);
+                       $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
+                       while ($contact = DBA::fetch($contacts)) {
+                               if (empty($receivers[$contact['uid']]) && self::isValidReceiverForActor($contact, $tags)) {
+                                       $receivers[$contact['uid']] = ['uid' => $contact['uid'], 'type' => $target_type];
+                               }
+                       }
+                       DBA::close($contacts);
                }
-               DBA::close($contacts);
                return $receivers;
        }
 
@@ -809,13 +1112,12 @@ class Receiver
         * Tests if the contact is a valid receiver for this actor
         *
         * @param array  $contact
-        * @param string $actor
         * @param array  $tags
         *
         * @return bool with receivers (user id)
         * @throws \Exception
         */
-       private static function isValidReceiverForActor($contact, $tags)
+       private static function isValidReceiverForActor(array $contact, array $tags): bool
        {
                // Are we following the contact? Then this is a valid receiver
                if (in_array($contact['rel'], [Contact::SHARING, Contact::FRIEND])) {
@@ -848,10 +1150,11 @@ class Receiver
         * @param integer $cid Contact ID
         * @param integer $uid User ID
         * @param string  $url Profile URL
+        * @return void
         * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         * @throws \ImagickException
         */
-       public static function switchContact($cid, $uid, $url)
+       public static function switchContact(int $cid, int $uid, string $url)
        {
                if (DBA::exists('contact', ['id' => $cid, 'network' => Protocol::ACTIVITYPUB])) {
                        Logger::info('Contact is already ActivityPub', ['id' => $cid, 'uid' => $uid, 'url' => $url]);
@@ -870,10 +1173,11 @@ class Receiver
        }
 
        /**
-        *
+        * @TODO Fix documentation and type-hints
         *
         * @param $receivers
         * @param $actor
+        * @return void
         * @throws \Friendica\Network\HTTPException\InternalServerErrorException
         * @throws \ImagickException
         */
@@ -897,14 +1201,14 @@ class Receiver
        }
 
        /**
-        *
+        * @TODO Fix documentation and type-hints
         *
         * @param       $object_data
         * @param array $activity
         *
         * @return mixed
         */
-       private static function addActivityFields($object_data, $activity)
+       private static function addActivityFields($object_data, array $activity)
        {
                if (!empty($activity['published']) && empty($object_data['published'])) {
                        $object_data['published'] = JsonLD::fetchElement($activity, 'as:published', '@value');
@@ -1024,7 +1328,7 @@ class Receiver
         * @param array $languages
         * @return array Languages
         */
-       public static function processLanguages(array $languages)
+       public static function processLanguages(array $languages): array
        {
                if (empty($languages)) {
                        return [];
@@ -1047,7 +1351,7 @@ class Receiver
         *
         * @return array with tags in a simplified format
         */
-       public static function processTags(array $tags)
+       public static function processTags(array $tags): array
        {
                $taglist = [];
 
@@ -1079,7 +1383,7 @@ class Receiver
         * @param array $emojis
         * @return array with emojis in a simplified format
         */
-       private static function processEmojis(array $emojis)
+       private static function processEmojis(array $emojis): array
        {
                $emojilist = [];
 
@@ -1105,7 +1409,7 @@ class Receiver
         *
         * @return array Attachments in a simplified format
         */
-       private static function processAttachments(array $attachments)
+       private static function processAttachments(array $attachments): array
        {
                $attachlist = [];
 
@@ -1215,16 +1519,75 @@ class Receiver
                return $attachlist;
        }
 
+       /**
+        * Convert questions from JSON-LD format into a simplified format
+        *
+        * @param array $object
+        *
+        * @return array Questions in a simplified format
+        */
+       private static function processQuestion(array $object): array
+       {
+               $question = [];
+
+               if (!empty($object['as:oneOf'])) {
+                       $question['multiple'] = false;
+                       $options = JsonLD::fetchElementArray($object, 'as:oneOf') ?? [];
+               } elseif (!empty($object['as:anyOf'])) {
+                       $question['multiple'] = true;
+                       $options = JsonLD::fetchElementArray($object, 'as:anyOf') ?? [];
+               } else {
+                       return [];
+               }
+
+               $closed = JsonLD::fetchElement($object, 'as:closed', '@value');
+               if (!empty($closed)) {
+                       $question['end-time'] = $closed;
+               } else {
+                       $question['end-time'] = JsonLD::fetchElement($object, 'as:endTime', '@value');
+               }
+
+               $question['voters']  = (int)JsonLD::fetchElement($object, 'toot:votersCount', '@value');
+               $question['options'] = [];
+
+               $voters = 0;
+
+               foreach ($options as $option) {
+                       if (JsonLD::fetchElement($option, '@type') != 'as:Note') {
+                               continue;
+                       }
+
+                       $name = JsonLD::fetchElement($option, 'as:name', '@value');
+
+                       if (empty($option['as:replies'])) {
+                               continue;
+                       }
+
+                       $replies = JsonLD::fetchElement($option['as:replies'], 'as:totalItems', '@value');
+
+                       $question['options'][] = ['name' => $name, 'replies' => $replies];
+
+                       $voters += (int)$replies;
+               }
+
+               // For single choice question we can count the number of voters if not provided (like with Misskey)
+               if (empty($question['voters']) && !$question['multiple']) {
+                       $question['voters'] = $voters;
+               }
+
+               return $question;
+       }
+
        /**
         * Fetch the original source or content with the "language" Markdown or HTML
         *
         * @param array $object
         * @param array $object_data
         *
-        * @return array
+        * @return array Object data (?)
         * @throws \Exception
         */
-       private static function getSource($object, $object_data)
+       private static function getSource(array $object, array $object_data): array
        {
                $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/bbcode');
                $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
@@ -1353,10 +1716,10 @@ class Receiver
         *
         * @param array $object
         *
-        * @return array
+        * @return array|bool Object data or FALSE if $object does not contain @id element
         * @throws \Exception
         */
-       private static function processObject($object)
+       private static function processObject(array $object)
        {
                if (!JsonLD::fetchElement($object, '@id')) {
                        return false;
@@ -1449,48 +1812,42 @@ class Receiver
                        }
                }
 
+               if (!empty($object_data['alternate-url']) && !Network::isValidHttpUrl($object_data['alternate-url'])) {
+                       $object_data['alternate-url'] = null;
+               }
+
                if (in_array($object_data['object_type'], ['as:Audio', 'as:Video'])) {
                        $object_data['alternate-url'] = self::extractAlternateUrl($object['as:url'] ?? []) ?: $object_data['alternate-url'];
                        $object_data['attachments'] = array_merge($object_data['attachments'], self::processAttachmentUrls($object['as:url'] ?? []));
                }
 
-               $receiverdata = self::getReceivers($object, $object_data['actor'], $object_data['tags'], true);
+               // For page types we expect that the alternate url posts to some page.
+               // So we add this to the attachments if it differs from the id.
+               // Currently only Lemmy is using the page type.
+               if (($object_data['object_type'] == 'as:Page') && !empty($object_data['alternate-url']) && !Strings::compareLink($object_data['alternate-url'], $object_data['id'])) {
+                       $object_data['attachments'][] = ['url' => $object_data['alternate-url']];
+                       $object_data['alternate-url'] = null;
+               }
+
+               if ($object_data['object_type'] == 'as:Question') {
+                       $object_data['question'] = self::processQuestion($object);
+               }
+
+               $receiverdata = self::getReceivers($object, $object_data['actor'] ?? '', $object_data['tags'], true);
                $receivers = $reception_types = [];
                foreach ($receiverdata as $key => $data) {
                        $receivers[$key] = $data['uid'];
                        $reception_types[$data['uid']] = $data['type'] ?? 0;
                }
 
-               $object_data['receiver'] = $receivers;
+               $object_data['receiver_urls']  = self::getReceiverURL($object);
+               $object_data['receiver']       = $receivers;
                $object_data['reception_type'] = $reception_types;
 
                $object_data['unlisted'] = in_array(-1, $object_data['receiver']);
                unset($object_data['receiver'][-1]);
                unset($object_data['reception_type'][-1]);
 
-               // Common object data:
-
-               // Unhandled
-               // @context, type, actor, signature, mediaType, duration, replies, icon
-
-               // Also missing: (Defined in the standard, but currently unused)
-               // audience, preview, endTime, startTime, image
-
-               // Data in Notes:
-
-               // Unhandled
-               // contentMap, announcement_count, announcements, context_id, likes, like_count
-               // inReplyToStatusId, shares, quoteUrl, statusnetConversationId
-
-               // Data in video:
-
-               // To-Do?
-               // category, licence, language, commentsEnabled
-
-               // Unhandled
-               // views, waitTranscoding, state, support, subtitleLanguage
-               // likes, dislikes, shares, comments
-
                return $object_data;
        }
 }