]> git.mxchange.org Git - friendica.git/blobdiff - src/Protocol/ActivityPub.php
Merge remote-tracking branch 'upstream/2018.08-rc' into ap1
[friendica.git] / src / Protocol / ActivityPub.php
index 36cc32d64b961b5c1b1f3101ef84be757e4520ad..95542ba966200b9fb14aa261f11013814e0468cc 100644 (file)
@@ -19,6 +19,8 @@ use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Crypto;
 use Friendica\Content\Text\BBCode;
 use Friendica\Content\Text\HTML;
+use Friendica\Util\JsonLD;
+use Friendica\Util\LDSignature;
 
 /**
  * @brief ActivityPub Protocol class
@@ -44,13 +46,13 @@ use Friendica\Content\Text\HTML;
  * - Object Types: Person, Tombstome
  *
  * Transmitter:
- * - Activities: Like, Dislike, Update, Delete
- * - Object Tyoes: Article, Announce, Person, Tombstone
+ * - Activities: Like, Dislike, Update, Delete, Announce
+ * - Object Tyoes: Article, Person, Tombstone
  *
  * General:
- * - Message distribution
- * - Endpoints: Outbox, Object, Follower, Following
+ * - Endpoints: Outbox, Follower, Following
  * - General cleanup
+ * - Queueing unsucessful deliveries
  */
 class ActivityPub
 {
@@ -62,38 +64,6 @@ class ActivityPub
                        stristr(defaults($_SERVER, 'HTTP_ACCEPT', ''), 'application/ld+json');
        }
 
-       public static function transmit($data, $target, $uid)
-       {
-               $owner = User::getOwnerDataById($uid);
-
-               if (!$owner) {
-                       return;
-               }
-
-               $content = json_encode($data);
-
-               // Header data that is about to be signed.
-               $host = parse_url($target, PHP_URL_HOST);
-               $path = parse_url($target, PHP_URL_PATH);
-               $digest = 'SHA-256=' . base64_encode(hash('sha256', $content, true));
-               $content_length = strlen($content);
-
-               $headers = ['Content-Length: ' . $content_length, 'Digest: ' . $digest, 'Host: ' . $host];
-
-               $signed_data = "(request-target): post " . $path . "\ncontent-length: " . $content_length . "\ndigest: " . $digest . "\nhost: " . $host;
-
-               $signature = base64_encode(Crypto::rsaSign($signed_data, $owner['uprvkey'], 'sha256'));
-
-               $headers[] = 'Signature: keyId="' . $owner['url'] . '#main-key' . '",algorithm="rsa-sha256",headers="(request-target) content-length digest host",signature="' . $signature . '"';
-
-               $headers[] = 'Content-Type: application/activity+json';
-
-               Network::post($target, $content, $headers);
-               $return_code = BaseObject::getApp()->get_curl_code();
-
-               logger('Transmit to ' . $target . ' returned ' . $return_code);
-       }
-
        /**
         * Return the ActivityPub profile of the given user
         *
@@ -102,10 +72,10 @@ class ActivityPub
         */
        public static function profile($uid)
        {
-               $accounttype = ['Person', 'Organization', 'Service', 'Group', 'Application', 'page-flags'];
+               $accounttype = ['Person', 'Organization', 'Service', 'Group', 'Application'];
                $condition = ['uid' => $uid, 'blocked' => false, 'account_expired' => false,
                        'account_removed' => false, 'verified' => true];
-               $fields = ['guid', 'nickname', 'pubkey', 'account-type'];
+               $fields = ['guid', 'nickname', 'pubkey', 'account-type', 'page-flags'];
                $user = DBA::selectFirst('user', $fields, $condition);
                if (!DBA::isResult($user)) {
                        return [];
@@ -140,7 +110,7 @@ class ActivityPub
                        'vcard:region' => $profile['region'], 'vcard:locality' => $profile['locality']];
                $data['summary'] = $contact['about'];
                $data['url'] = $contact['url'];
-               $data['manuallyApprovesFollowers'] = in_array($profile['page-flags'], [Contact::PAGE_NORMAL, Contact::PAGE_PRVGROUP]);
+               $data['manuallyApprovesFollowers'] = in_array($user['page-flags'], [Contact::PAGE_NORMAL, Contact::PAGE_PRVGROUP]);
                $data['publicKey'] = ['id' => $contact['url'] . '#main-key',
                        'owner' => $contact['url'],
                        'publicKeyPem' => $user['pubkey']];
@@ -152,27 +122,76 @@ class ActivityPub
                return $data;
        }
 
+       private static function fetchPermissionBlockFromConversation($item)
+       {
+               if (empty($item['thr-parent'])) {
+                       return [];
+               }
+
+               $condition = ['item-uri' => $item['thr-parent'], 'protocol' => Conversation::PARCEL_ACTIVITYPUB];
+               $conversation = DBA::selectFirst('conversation', ['source'], $condition);
+               if (!DBA::isResult($conversation)) {
+                       return [];
+               }
+
+               $activity = json_decode($conversation['source'], true);
+
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               $profile = ActivityPub::fetchprofile($actor);
+
+               $item_profile = ActivityPub::fetchprofile($item['owner-link']);
+
+               $permissions = [];
+
+               $elements = ['to', 'cc', 'bto', 'bcc'];
+               foreach ($elements as $element) {
+                       if (empty($activity[$element])) {
+                               continue;
+                       }
+                       if (is_string($activity[$element])) {
+                               $activity[$element] = [$activity[$element]];
+                       }
+                       foreach ($activity[$element] as $receiver) {
+                               if ($receiver == $profile['followers'] && !empty($item_profile['followers'])) {
+                                       $receiver = $item_profile['followers'];
+                               }
+                               if ($receiver != $item['owner-link']) {
+                                       $permissions[$element][] = $receiver;
+                               }
+                       }
+               }
+               return $permissions;
+       }
+
        public static function createPermissionBlockForItem($item)
        {
                $data = ['to' => [], 'cc' => []];
 
+               $data = array_merge($data, self::fetchPermissionBlockFromConversation($item));
+
+               $actor_profile = ActivityPub::fetchprofile($item['author-link']);
+
                $terms = Term::tagArrayFromItemId($item['id']);
 
+               $contacts[$item['author-link']] = $item['author-link'];
+
                if (!$item['private']) {
                        $data['to'][] = self::PUBLIC;
-                       $data['cc'][] = System::baseUrl() . '/followers/' . $item['author-nick'];
+                       if (!empty($actor_profile['followers'])) {
+                               $data['cc'][] = $actor_profile['followers'];
+                       }
 
                        foreach ($terms as $term) {
                                if ($term['type'] != TERM_MENTION) {
                                        continue;
                                }
                                $profile = self::fetchprofile($term['url']);
-                               if (!empty($profile)) {
+                               if (!empty($profile) && empty($contacts[$profile['url']])) {
                                        $data['cc'][] = $profile['url'];
+                                       $contacts[$profile['url']] = $profile['url'];
                                }
                        }
                } else {
-                       //$data['cc'][] = System::baseUrl() . '/followers/' . $item['author-nick'];
                        $receiver_list = Item::enumeratePermissions($item);
 
                        $mentioned = [];
@@ -185,84 +204,84 @@ class ActivityPub
                                if (!empty($cid) && in_array($cid, $receiver_list)) {
                                        $contact = DBA::selectFirst('contact', ['url'], ['id' => $cid, 'network' => Protocol::ACTIVITYPUB]);
                                        $data['to'][] = $contact['url'];
+                                       $contacts[$contact['url']] = $contact['url'];
                                }
                        }
 
                        foreach ($receiver_list as $receiver) {
                                $contact = DBA::selectFirst('contact', ['url'], ['id' => $receiver, 'network' => Protocol::ACTIVITYPUB]);
-                               $data['cc'][] = $contact['url'];
+                               if (empty($contacts[$contact['url']])) {
+                                       $data['cc'][] = $contact['url'];
+                                       $contacts[$contact['url']] = $contact['url'];
+                               }
+                       }
+               }
+
+               $parents = Item::select(['author-link', 'owner-link'], ['parent' => $item['parent']]);
+               while ($parent = Item::fetch($parents)) {
+                       $profile = self::fetchprofile($parent['author-link']);
+                       if (!empty($profile) && empty($contacts[$profile['url']])) {
+                               $data['cc'][] = $profile['url'];
+                               $contacts[$profile['url']] = $profile['url'];
                        }
 
-                       if (empty($data['to'])) {
-                               $data['to'] = $data['cc'];
-                               $data['cc'] = [];
+                       $profile = self::fetchprofile($parent['owner-link']);
+                       if (!empty($profile) && empty($contacts[$profile['url']])) {
+                               $data['cc'][] = $profile['url'];
+                               $contacts[$profile['url']] = $profile['url'];
                        }
                }
+               DBA::close($parents);
+
+               if (empty($data['to'])) {
+                       $data['to'] = $data['cc'];
+                       $data['cc'] = [];
+               }
 
                return $data;
        }
 
-       public static function fetchTargetInboxes($item)
+       public static function fetchTargetInboxes($item, $uid)
        {
+               $permissions = self::createPermissionBlockForItem($item);
+               if (empty($permissions)) {
+                       return [];
+               }
+
                $inboxes = [];
 
-               $terms = Term::tagArrayFromItemId($item['id']);
-               if (!$item['private']) {
-                       $contacts = DBA::select('contact', ['notify', 'batch'], ['uid' => $item['uid'],
-                                       'rel' => [Contact::FOLLOWER, Contact::FRIEND], 'network' => Protocol::ACTIVITYPUB]);
-                       while ($contact = DBA::fetch($contacts)) {
-                               $contact = defaults($contact, 'batch', $contact['notify']);
-                               $inboxes[$contact] = $contact;
-                       }
-                       DBA::close($contacts);
+               $item_profile = ActivityPub::fetchprofile($item['owner-link']);
 
-                       foreach ($terms as $term) {
-                               if ($term['type'] != TERM_MENTION) {
-                                       continue;
-                               }
-                               $profile = self::fetchprofile($term['url']);
-                               if (!empty($profile)) {
-                                       $target = defaults($profile, 'sharedinbox', $profile['inbox']);
-                                       $inboxes[$target] = $target;
-                               }
+               $elements = ['to', 'cc', 'bto', 'bcc'];
+               foreach ($elements as $element) {
+                       if (empty($permissions[$element])) {
+                               continue;
                        }
-               } else {
-                       $receiver_list = Item::enumeratePermissions($item);
-
-                       $mentioned = [];
-
-                       foreach ($terms as $term) {
-                               if ($term['type'] != TERM_MENTION) {
-                                       continue;
-                               }
-                               $cid = Contact::getIdForURL($term['url'], $item['uid']);
-                               if (!empty($cid) && in_array($cid, $receiver_list)) {
-                                       $contact = DBA::selectFirst('contact', ['url'], ['id' => $cid, 'network' => Protocol::ACTIVITYPUB]);
-                                       $profile = self::fetchprofile($contact['url']);
-                                       if (!empty($profile['network'])) {
+                       foreach ($permissions[$element] as $receiver) {
+                               if ($receiver == $item_profile['followers']) {
+                                       $contacts = DBA::select('contact', ['notify', 'batch'], ['uid' => $uid,
+                                               'rel' => [Contact::FOLLOWER, Contact::FRIEND], 'network' => Protocol::ACTIVITYPUB]);
+                                       while ($contact = DBA::fetch($contacts)) {
+                                               $contact = defaults($contact, 'batch', $contact['notify']);
+                                               $inboxes[$contact] = $contact;
+                                       }
+                                       DBA::close($contacts);
+                               } else {
+                                       $profile = self::fetchprofile($receiver);
+                                       if (!empty($profile)) {
                                                $target = defaults($profile, 'sharedinbox', $profile['inbox']);
                                                $inboxes[$target] = $target;
                                        }
                                }
                        }
-
-                       foreach ($receiver_list as $receiver) {
-                               $contact = DBA::selectFirst('contact', ['url'], ['id' => $receiver, 'network' => Protocol::ACTIVITYPUB]);
-                               $profile = self::fetchprofile($contact['url']);
-                               if (!empty($profile['network'])) {
-                                       $target = defaults($profile, 'sharedinbox', $profile['inbox']);
-                                       $inboxes[$target] = $target;
-                               }
-                       }
                }
 
-               $profile = self::fetchprofile($item['author-link']);
-               if (!empty($profile['sharedinbox'])) {
-                       unset($inboxes[$profile['sharedinbox']]);
+               if (!empty($item_profile['sharedinbox'])) {
+                       unset($inboxes[$item_profile['sharedinbox']]);
                }
 
-               if (!empty($profile['inbox'])) {
-                       unset($inboxes[$profile['inbox']]);
+               if (!empty($item_profile['inbox'])) {
+                       unset($inboxes[$item_profile['inbox']]);
                }
 
                return $inboxes;
@@ -291,8 +310,8 @@ class ActivityPub
                        'conversation' => 'ostatus:conversation',
                        'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri']]];
 
-               $data['type'] = 'Create';
                $data['id'] = $item['uri'] . '#activity';
+               $data['type'] = 'Create';
                $data['actor'] = $item['author-link'];
 
                $data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
@@ -301,10 +320,16 @@ class ActivityPub
                        $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
                }
 
+               $data['context_id'] = $item['parent'];
+               $data['context'] = self::createConversationURLFromItem($item);
+
                $data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
 
-               $data['object'] = self::createNote($item);
-               return $data;
+               $data['object'] = self::createObjectTypeFromItem($item);
+
+               $owner = User::getOwnerDataById($item['uid']);
+
+               return LDSignature::sign($data, $owner);
        }
 
        public static function createObjectFromItemID($item_id)
@@ -321,7 +346,7 @@ class ActivityPub
                        'conversation' => 'ostatus:conversation',
                        'inReplyToAtomUri' => 'ostatus:inReplyToAtomUri']]];
 
-               $data = array_merge($data, self::createNote($item));
+               $data = array_merge($data, self::createObjectTypeFromItem($item));
 
 
                return $data;
@@ -344,45 +369,63 @@ class ActivityPub
                                $tags[] = ['type' => 'Mention', 'href' => $term['url'], 'name' => $mention];
                        }
                }
-
                return $tags;
        }
 
-       public static function createNote($item)
+       private static function createConversationURLFromItem($item)
        {
+               $conversation = DBA::selectFirst('conversation', ['conversation-uri'], ['item-uri' => $item['parent-uri']]);
+               if (DBA::isResult($conversation) && !empty($conversation['conversation-uri'])) {
+                       $conversation_uri = $conversation['conversation-uri'];
+               } else {
+                       $conversation_uri = $item['parent-uri'];
+               }
+               return $conversation_uri;
+       }
+
+       private static function createObjectTypeFromItem($item)
+       {
+               if (!empty($item['title'])) {
+                       $type = 'Article';
+               } else {
+                       $type = 'Note';
+               }
+
                $data = [];
-               $data['type'] = 'Note';
                $data['id'] = $item['uri'];
+               $data['type'] = $type;
+               $data['summary'] = null; // Ignore by now
 
                if ($item['uri'] != $item['thr-parent']) {
                        $data['inReplyTo'] = $item['thr-parent'];
-               }
-
-               $conversation = DBA::selectFirst('conversation', ['conversation-uri'], ['item-uri' => $item['parent-uri']]);
-               if (DBA::isResult($conversation) && !empty($conversation['conversation-uri'])) {
-                       $conversation_uri = $conversation['conversation-uri'];
                } else {
-                       $conversation_uri = $item['parent-uri'];
+                       $data['inReplyTo'] = null;
                }
 
-               $data['context'] = $data['conversation'] = $conversation_uri;
-               $data['actor'] = $item['author-link'];
-               $data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
                $data['published'] = DateTimeFormat::utc($item["created"]."+00:00", DateTimeFormat::ATOM);
 
                if ($item["created"] != $item["edited"]) {
                        $data['updated'] = DateTimeFormat::utc($item["edited"]."+00:00", DateTimeFormat::ATOM);
                }
 
+               $data['url'] = $item['plink'];
                $data['attributedTo'] = $item['author-link'];
-               $data['name'] = BBCode::convert($item['title'], false, 7);
+               $data['actor'] = $item['author-link'];
+               $data['sensitive'] = false; // - Query NSFW
+               $data['context_id'] = $item['parent'];
+               $data['conversation'] = $data['context'] = self::createConversationURLFromItem($item);
+
+               if (!empty($item['title'])) {
+                       $data['name'] = BBCode::convert($item['title'], false, 7);
+               }
+
                $data['content'] = BBCode::convert($item['body'], false, 7);
                $data['source'] = ['content' => $item['body'], 'mediaType' => "text/bbcode"];
-               $data['summary'] = ''; // Ignore by now
-               $data['sensitive'] = false; // - Query NSFW
-               //$data['emoji'] = []; // Ignore by now
-               $data['tag'] = self::createTagList($item);
                $data['attachment'] = []; // @ToDo
+               $data['tag'] = self::createTagList($item);
+               $data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
+
+               //$data['emoji'] = []; // Ignore by now
                return $data;
        }
 
@@ -400,7 +443,9 @@ class ActivityPub
                        'to' => $profile['url']];
 
                logger('Sending activity ' . $activity . ' to ' . $target . ' for user ' . $uid, LOGGER_DEBUG);
-               return self::transmit($data,  $profile['inbox'], $uid);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
        public static function transmitContactAccept($target, $id, $uid)
@@ -418,7 +463,9 @@ class ActivityPub
                        'to' => $profile['url']];
 
                logger('Sending accept to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-               return self::transmit($data,  $profile['inbox'], $uid);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
        public static function transmitContactReject($target, $id, $uid)
@@ -436,7 +483,9 @@ class ActivityPub
                        'to' => $profile['url']];
 
                logger('Sending reject to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-               return self::transmit($data,  $profile['inbox'], $uid);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
        public static function transmitContactUndo($target, $uid)
@@ -456,7 +505,9 @@ class ActivityPub
                        'to' => $profile['url']];
 
                logger('Sending undo to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-               return self::transmit($data,  $profile['inbox'], $uid);
+
+               $signed = LDSignature::sign($data, $owner);
+               return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
        }
 
        /**
@@ -514,154 +565,6 @@ class ActivityPub
                return false;
        }
 
-       public static function verifySignature($content, $http_headers)
-       {
-               $object = json_decode($content, true);
-
-               if (empty($object)) {
-                       return false;
-               }
-
-               $actor = self::processElement($object, 'actor', 'id');
-
-               $headers = [];
-               $headers['(request-target)'] = strtolower($http_headers['REQUEST_METHOD']) . ' ' . $http_headers['REQUEST_URI'];
-
-               // First take every header
-               foreach ($http_headers as $k => $v) {
-                       $field = str_replace('_', '-', strtolower($k));
-                       $headers[$field] = $v;
-               }
-
-               // Now add every http header
-               foreach ($http_headers as $k => $v) {
-                       if (strpos($k, 'HTTP_') === 0) {
-                               $field = str_replace('_', '-', strtolower(substr($k, 5)));
-                               $headers[$field] = $v;
-                       }
-               }
-
-               $sig_block = ActivityPub::parseSigHeader($http_headers['HTTP_SIGNATURE']);
-
-               if (empty($sig_block) || empty($sig_block['headers']) || empty($sig_block['keyId'])) {
-                       return false;
-               }
-
-               $signed_data = '';
-               foreach ($sig_block['headers'] as $h) {
-                       if (array_key_exists($h, $headers)) {
-                               $signed_data .= $h . ': ' . $headers[$h] . "\n";
-                       }
-               }
-               $signed_data = rtrim($signed_data, "\n");
-
-               if (empty($signed_data)) {
-                       return false;
-               }
-
-               $algorithm = null;
-
-               if ($sig_block['algorithm'] === 'rsa-sha256') {
-                       $algorithm = 'sha256';
-               }
-
-               if ($sig_block['algorithm'] === 'rsa-sha512') {
-                       $algorithm = 'sha512';
-               }
-
-               if (empty($algorithm)) {
-                       return false;
-               }
-
-               $key = self::fetchKey($sig_block['keyId'], $actor);
-
-               if (empty($key)) {
-                       return false;
-               }
-
-               if (!Crypto::rsaVerify($signed_data, $sig_block['signature'], $key, $algorithm)) {
-                       return false;
-               }
-
-               // Check the digest when it is part of the signed data
-               if (in_array('digest', $sig_block['headers'])) {
-                       $digest = explode('=', $headers['digest'], 2);
-                       if ($digest[0] === 'SHA-256') {
-                               $hashalg = 'sha256';
-                       }
-                       if ($digest[0] === 'SHA-512') {
-                               $hashalg = 'sha512';
-                       }
-
-                       /// @todo add all hashes from the rfc
-
-                       if (!empty($hashalg) && base64_encode(hash($hashalg, $content, true)) != $digest[1]) {
-                               return false;
-                       }
-               }
-
-               // Check the content-length when it is part of the signed data
-               if (in_array('content-length', $sig_block['headers'])) {
-                       if (strlen($content) != $headers['content-length']) {
-                               return false;
-                       }
-               }
-
-               return true;
-
-       }
-
-       private static function fetchKey($id, $actor)
-       {
-               $url = (strpos($id, '#') ? substr($id, 0, strpos($id, '#')) : $id);
-
-               $profile = self::fetchprofile($url);
-               if (!empty($profile)) {
-                       return $profile['pubkey'];
-               } elseif ($url != $actor) {
-                       $profile = self::fetchprofile($actor);
-                       if (!empty($profile)) {
-                               return $profile['pubkey'];
-                       }
-               }
-
-               return false;
-       }
-
-       /**
-        * @brief
-        *
-        * @param string $header
-        * @return array associate array with
-        *   - \e string \b keyID
-        *   - \e string \b algorithm
-        *   - \e array  \b headers
-        *   - \e string \b signature
-        */
-       private static function parseSigHeader($header)
-       {
-               $ret = [];
-               $matches = [];
-
-               if (preg_match('/keyId="(.*?)"/ism',$header,$matches)) {
-                       $ret['keyId'] = $matches[1];
-               }
-
-               if (preg_match('/algorithm="(.*?)"/ism',$header,$matches)) {
-                       $ret['algorithm'] = $matches[1];
-               }
-
-               if (preg_match('/headers="(.*?)"/ism',$header,$matches)) {
-                       $ret['headers'] = explode(' ', $matches[1]);
-               }
-
-               if (preg_match('/signature="(.*?)"/ism',$header,$matches)) {
-                       $ret['signature'] = base64_decode(preg_replace('/\s+/','',$matches[1]));
-               }
-
-               return $ret;
-       }
-
        public static function fetchprofile($url, $update = false)
        {
                if (empty($url)) {
@@ -706,19 +609,19 @@ class ActivityPub
                $apcontact['followers'] = defaults($data, 'followers', null);
                $apcontact['inbox'] = defaults($data, 'inbox', null);
                $apcontact['outbox'] = defaults($data, 'outbox', null);
-               $apcontact['sharedinbox'] = self::processElement($data, 'endpoints', 'sharedInbox');
+               $apcontact['sharedinbox'] = JsonLD::fetchElement($data, 'endpoints', 'sharedInbox');
                $apcontact['nick'] = defaults($data, 'preferredUsername', null);
                $apcontact['name'] = defaults($data, 'name', $apcontact['nick']);
                $apcontact['about'] = defaults($data, 'summary', '');
-               $apcontact['photo'] = self::processElement($data, 'icon', 'url');
-               $apcontact['alias'] = self::processElement($data, 'url', 'href');
+               $apcontact['photo'] = JsonLD::fetchElement($data, 'icon', 'url');
+               $apcontact['alias'] = JsonLD::fetchElement($data, 'url', 'href');
 
                $parts = parse_url($apcontact['url']);
                unset($parts['scheme']);
                unset($parts['path']);
                $apcontact['addr'] = $apcontact['nick'] . '@' . str_replace('//', '', Network::unparseURL($parts));
 
-               $apcontact['pubkey'] = trim(self::processElement($data, 'publicKey', 'publicKeyPem'));
+               $apcontact['pubkey'] = trim(JsonLD::fetchElement($data, 'publicKey', 'publicKeyPem'));
 
                // To-Do
                // manuallyApprovesFollowers
@@ -795,24 +698,51 @@ class ActivityPub
 
        public static function processInbox($body, $header, $uid)
        {
-               logger('Incoming message for user ' . $uid, LOGGER_DEBUG);
-
-               if (!self::verifySignature($body, $header)) {
-                       logger('Invalid signature, message will be discarded.', LOGGER_DEBUG);
+               $http_signer = HTTPSignature::getSigner($body, $header);
+               if (empty($http_signer)) {
+                       logger('Invalid HTTP signature, message will be discarded.', LOGGER_DEBUG);
                        return;
+               } else {
+                       logger('HTTP signature is signed by ' . $http_signer, LOGGER_DEBUG);
                }
 
                $activity = json_decode($body, true);
 
-               if (!is_array($activity)) {
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
+               logger('Message for user ' . $uid . ' is from actor ' . $actor, LOGGER_DEBUG);
+
+               if (empty($activity)) {
                        logger('Invalid body.', LOGGER_DEBUG);
                        return;
                }
 
-               self::processActivity($activity, $body, $uid);
+               if (LDSignature::isSigned($activity)) {
+                       $ld_signer = LDSignature::getSigner($activity);
+                       if (!empty($ld_signer && ($actor == $http_signer))) {
+                               logger('The HTTP and the JSON-LD signature belong to ' . $ld_signer, LOGGER_DEBUG);
+                               $trust_source = true;
+                       } elseif (!empty($ld_signer)) {
+                               logger('JSON-LD signature is signed by ' . $ld_signer, LOGGER_DEBUG);
+                               $trust_source = true;
+                       } elseif ($actor == $http_signer) {
+                               logger('Bad JSON-LD signature, but HTTP signer fits the actor.', LOGGER_DEBUG);
+                               $trust_source = true;
+                       } else {
+                               logger('Invalid JSON-LD signature and the HTTP signer is different.', LOGGER_DEBUG);
+                               $trust_source = false;
+                       }
+               } elseif ($actor == $http_signer) {
+                       logger('Trusting post without JSON-LD signature, The actor fits the HTTP signer.', LOGGER_DEBUG);
+                       $trust_source = true;
+               } else {
+                       logger('No JSON-LD signature, different actor.', LOGGER_DEBUG);
+                       $trust_source = false;
+               }
+
+               self::processActivity($activity, $body, $uid, $trust_source);
        }
 
-       public static function fetchOutbox($url)
+       public static function fetchOutbox($url, $uid)
        {
                $data = self::fetchContent($url);
                if (empty($data)) {
@@ -824,20 +754,20 @@ class ActivityPub
                } elseif (!empty($data['first']['orderedItems'])) {
                        $items = $data['first']['orderedItems'];
                } elseif (!empty($data['first'])) {
-                       self::fetchOutbox($data['first']);
+                       self::fetchOutbox($data['first'], $uid);
                        return;
                } else {
                        $items = [];
                }
 
                foreach ($items as $activity) {
-                       self::processActivity($activity);
+                       self::processActivity($activity, '', $uid, true);
                }
        }
 
-       private static function prepareObjectData($activity, $uid)
+       private static function prepareObjectData($activity, $uid, $trust_source)
        {
-               $actor = self::processElement($activity, 'actor', 'id');
+               $actor = JsonLD::fetchElement($activity, 'actor', 'id');
                if (empty($actor)) {
                        logger('Empty actor', LOGGER_DEBUG);
                        return [];
@@ -855,8 +785,6 @@ class ActivityPub
 
                logger('Receivers: ' . json_encode($receivers), LOGGER_DEBUG);
 
-               $public = in_array(0, $receivers);
-
                if (is_string($activity['object'])) {
                        $object_url = $activity['object'];
                } elseif (!empty($activity['object']['id'])) {
@@ -868,19 +796,19 @@ class ActivityPub
 
                // Fetch the content only on activities where this matters
                if (in_array($activity['type'], ['Create', 'Update', 'Announce'])) {
-                       $object_data = self::fetchObject($object_url, $activity['object']);
+                       $object_data = self::fetchObject($object_url, $activity['object'], $trust_source);
                        if (empty($object_data)) {
                                logger("Object data couldn't be processed", LOGGER_DEBUG);
                                return [];
                        }
                } elseif ($activity['type'] == 'Accept') {
                        $object_data = [];
-                       $object_data['object_type'] = self::processElement($activity, 'object', 'type');
-                       $object_data['object'] = self::processElement($activity, 'object', 'actor');
+                       $object_data['object_type'] = JsonLD::fetchElement($activity, 'object', 'type');
+                       $object_data['object'] = JsonLD::fetchElement($activity, 'object', 'actor');
                } elseif ($activity['type'] == 'Undo') {
                        $object_data = [];
-                       $object_data['object_type'] = self::processElement($activity, 'object', 'type');
-                       $object_data['object'] = self::processElement($activity, 'object', 'object');
+                       $object_data['object_type'] = JsonLD::fetchElement($activity, 'object', 'type');
+                       $object_data['object'] = JsonLD::fetchElement($activity, 'object', 'object');
                } elseif (in_array($activity['type'], ['Like', 'Dislike'])) {
                        // 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 ech individual array element.
@@ -904,7 +832,7 @@ class ActivityPub
                return $object_data;
        }
 
-       private static function processActivity($activity, $body = '', $uid = null)
+       private static function processActivity($activity, $body = '', $uid = null, $trust_source = false)
        {
                if (empty($activity['type'])) {
                        logger('Empty type', LOGGER_DEBUG);
@@ -930,7 +858,7 @@ class ActivityPub
 
                logger('Processing activity: ' . $activity['type'], LOGGER_DEBUG);
 
-               $object_data = self::prepareObjectData($activity, $uid);
+               $object_data = self::prepareObjectData($activity, $uid, $trust_source);
                if (empty($object_data)) {
                        logger('No object data found', LOGGER_DEBUG);
                        return;
@@ -981,6 +909,15 @@ class ActivityPub
        {
                $receivers = [];
 
+               // When it is an answer, we inherite the receivers from the parent
+               $replyto = JsonLD::fetchElement($activity, 'inReplyTo', 'id');
+               if (!empty($replyto)) {
+                       $parents = Item::select(['uid'], ['uri' => $replyto]);
+                       while ($parent = Item::fetch($parents)) {
+                               $receivers['uid:' . $parent['uid']] = $parent['uid'];
+                       }
+               }
+
                if (!empty($actor)) {
                        $profile = self::fetchprofile($actor);
                        $followers = defaults($profile, 'followers', '');
@@ -1054,23 +991,24 @@ class ActivityPub
                }
 
                if (!empty($activity['inReplyTo']) && empty($object_data['parent-uri'])) {
-                       $object_data['parent-uri'] = self::processElement($activity, 'inReplyTo', 'id');
+                       $object_data['parent-uri'] = JsonLD::fetchElement($activity, 'inReplyTo', 'id');
                }
 
                if (!empty($activity['instrument'])) {
-                       $object_data['service'] = self::processElement($activity, 'instrument', 'name', 'type', 'Service');
+                       $object_data['service'] = JsonLD::fetchElement($activity, 'instrument', 'name', 'type', 'Service');
                }
                return $object_data;
        }
 
-       private static function fetchObject($object_url, $object = [], $public = true)
+       private static function fetchObject($object_url, $object = [], $trust_source = false)
        {
-               if ($public) {
+               if (!$trust_source || is_string($object)) {
                        $data = self::fetchContent($object_url);
                        if (empty($data)) {
                                logger('Empty content for ' . $object_url . ', check if content is available locally.', LOGGER_DEBUG);
                                $data = $object_url;
-                               $data = $object;
+                       } else {
+                               logger('Fetched content for ' . $object_url, LOGGER_DEBUG);
                        }
                } else {
                        logger('Using original object for url ' . $object_url, LOGGER_DEBUG);
@@ -1084,7 +1022,7 @@ class ActivityPub
                                return false;
                        }
                        logger('Using already stored item for url ' . $object_url, LOGGER_DEBUG);
-                       $data = self::createNote($item);
+                       $data = self::createObjectTypeFromItem($item);
                }
 
                if (empty($data['type'])) {
@@ -1134,7 +1072,7 @@ class ActivityPub
                $object_data['uri'] = $object['id'];
 
                if (!empty($object['inReplyTo'])) {
-                       $object_data['reply-to-uri'] = self::processElement($object, 'inReplyTo', 'id');
+                       $object_data['reply-to-uri'] = JsonLD::fetchElement($object, 'inReplyTo', 'id');
                } else {
                        $object_data['reply-to-uri'] = $object_data['uri'];
                }
@@ -1147,7 +1085,7 @@ class ActivityPub
                }
 
                $object_data['uuid'] = defaults($object, 'uuid', null);
-               $object_data['owner'] = $object_data['author'] = self::processElement($object, 'attributedTo', 'id');
+               $object_data['owner'] = $object_data['author'] = JsonLD::fetchElement($object, 'attributedTo', 'id');
                $object_data['context'] = defaults($object, 'context', null);
                $object_data['conversation'] = defaults($object, 'conversation', null);
                $object_data['sensitive'] = defaults($object, 'sensitive', null);
@@ -1156,11 +1094,11 @@ class ActivityPub
                $object_data['summary'] = defaults($object, 'summary', null);
                $object_data['content'] = defaults($object, 'content', null);
                $object_data['source'] = defaults($object, 'source', null);
-               $object_data['location'] = self::processElement($object, 'location', 'name', 'type', 'Place');
+               $object_data['location'] = JsonLD::fetchElement($object, 'location', 'name', 'type', 'Place');
                $object_data['attachments'] = defaults($object, 'attachment', null);
                $object_data['tags'] = defaults($object, 'tag', null);
-               $object_data['service'] = self::processElement($object, 'instrument', 'name', 'type', 'Service');
-               $object_data['alternate-url'] = self::processElement($object, 'url', 'href');
+               $object_data['service'] = JsonLD::fetchElement($object, 'instrument', 'name', 'type', 'Service');
+               $object_data['alternate-url'] = JsonLD::fetchElement($object, 'url', 'href');
                $object_data['receiver'] = self::getReceivers($object, $object_data['owner']);
 
                // Unhandled
@@ -1207,41 +1145,6 @@ class ActivityPub
                return $object_data;
        }
 
-       private static function processElement($array, $element, $key, $type = null, $type_value = null)
-       {
-               if (empty($array)) {
-                       return false;
-               }
-
-               if (empty($array[$element])) {
-                       return false;
-               }
-
-               if (is_string($array[$element])) {
-                       return $array[$element];
-               }
-
-               if (is_null($type_value)) {
-                       if (!empty($array[$element][$key])) {
-                               return $array[$element][$key];
-                       }
-
-                       if (!empty($array[$element][0][$key])) {
-                               return $array[$element][0][$key];
-                       }
-
-                       return false;
-               }
-
-               if (!empty($array[$element][$key]) && !empty($array[$element][$type]) && ($array[$element][$type] == $type_value)) {
-                       return $array[$element][$key];
-               }
-
-               /// @todo Add array search
-
-               return false;
-       }
-
        private static function convertMentions($body)
        {
                $URLSearchString = "^\[\]";
@@ -1358,7 +1261,7 @@ class ActivityPub
 
                $item = self::constructAttachList($activity['attachments'], $item);
 
-               $source = self::processElement($activity, 'source', 'content', 'mediaType', 'text/bbcode');
+               $source = JsonLD::fetchElement($activity, 'source', 'content', 'mediaType', 'text/bbcode');
                if (!empty($source)) {
                        $item['body'] = $source;
                }
@@ -1398,6 +1301,7 @@ class ActivityPub
                $activity['object'] = $object;
                $activity['published'] = $object['published'];
                $activity['type'] = 'Create';
+
                self::processActivity($activity);
                logger('Activity ' . $url . ' had been fetched and processed.');
        }