src/Protocol/ActivityPub/Receiver.php

   1 <?php
   2 /**
   3  * @copyright Copyright (C) 2020, Friendica
   4  *
   5  * @license GNU AGPL version 3 or any later version
   6  *
   7  * This program is free software: you can redistribute it and/or modify
   8  * it under the terms of the GNU Affero General Public License as
   9  * published by the Free Software Foundation, either version 3 of the
  10  * License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU Affero General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Affero General Public License
  18  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  19  *
  20  */
  21
  22 namespace Friendica\Protocol\ActivityPub;
  23
  24 use Friendica\Database\DBA;
  25 use Friendica\Content\Text\HTML;
  26 use Friendica\Content\Text\Markdown;
  27 use Friendica\Core\Logger;
  28 use Friendica\Core\Protocol;
  29 use Friendica\Model\Contact;
  30 use Friendica\Model\APContact;
  31 use Friendica\Model\Conversation;
  32 use Friendica\Model\Item;
  33 use Friendica\Model\User;
  34 use Friendica\Protocol\Activity;
  35 use Friendica\Protocol\ActivityPub;
  36 use Friendica\Util\DateTimeFormat;
  37 use Friendica\Util\HTTPSignature;
  38 use Friendica\Util\JsonLD;
  39 use Friendica\Util\LDSignature;
  40 use Friendica\Util\Strings;
  41
  42 /**
  43  * ActivityPub Receiver Protocol class
  44  *
  45  * To-Do:
  46  * @todo Undo Announce
  47  *
  48  * Check what this is meant to do:
  49  * - Add
  50  * - Block
  51  * - Flag
  52  * - Remove
  53  * - Undo Block
  54  */
  55 class Receiver
  56 {
  57         const PUBLIC_COLLECTION = 'as:Public';
  58         const ACCOUNT_TYPES = ['as:Person', 'as:Organization', 'as:Service', 'as:Group', 'as:Application'];
  59         const CONTENT_TYPES = ['as:Note', 'as:Article', 'as:Video', 'as:Image', 'as:Event'];
  60         const ACTIVITY_TYPES = ['as:Like', 'as:Dislike', 'as:Accept', 'as:Reject', 'as:TentativeAccept'];
  61
  62         /**
  63          * Checks if the web request is done for the AP protocol
  64          *
  65          * @return bool is it AP?
  66          */
  67         public static function isRequest()
  68         {
  69                 return stristr($_SERVER['HTTP_ACCEPT'] ?? '', 'application/activity+json') ||
  70                         stristr($_SERVER['HTTP_ACCEPT'] ?? '', 'application/ld+json');
  71         }
  72
  73         /**
  74          * Checks incoming message from the inbox
  75          *
  76          * @param         $body
  77          * @param         $header
  78          * @param integer $uid User ID
  79          * @throws \Exception
  80          */
  81         public static function processInbox($body, $header, $uid)
  82         {
  83                 $http_signer = HTTPSignature::getSigner($body, $header);
  84                 if (empty($http_signer)) {
  85                         Logger::warning('Invalid HTTP signature, message will be discarded.');
  86                         return;
  87                 } else {
  88                         Logger::info('Valid HTTP signature', ['signer' => $http_signer]);
  89                 }
  90
  91                 $activity = json_decode($body, true);
  92
  93                 if (empty($activity)) {
  94                         Logger::warning('Invalid body.');
  95                         return;
  96                 }
  97
  98                 $ldactivity = JsonLD::compact($activity);
  99
 100                 $actor = JsonLD::fetchElement($ldactivity, 'as:actor', '@id');
 101
 102                 Logger::info('Message for user ' . $uid . ' is from actor ' . $actor);
 103
 104                 if (LDSignature::isSigned($activity)) {
 105                         $ld_signer = LDSignature::getSigner($activity);
 106                         if (empty($ld_signer)) {
 107                                 Logger::log('Invalid JSON-LD signature from ' . $actor, Logger::DEBUG);
 108                         }
 109                         if (!empty($ld_signer && ($actor == $http_signer))) {
 110                                 Logger::log('The HTTP and the JSON-LD signature belong to ' . $ld_signer, Logger::DEBUG);
 111                                 $trust_source = true;
 112                         } elseif (!empty($ld_signer)) {
 113                                 Logger::log('JSON-LD signature is signed by ' . $ld_signer, Logger::DEBUG);
 114                                 $trust_source = true;
 115                         } elseif ($actor == $http_signer) {
 116                                 Logger::log('Bad JSON-LD signature, but HTTP signer fits the actor.', Logger::DEBUG);
 117                                 $trust_source = true;
 118                         } else {
 119                                 Logger::log('Invalid JSON-LD signature and the HTTP signer is different.', Logger::DEBUG);
 120                                 $trust_source = false;
 121                         }
 122                 } elseif ($actor == $http_signer) {
 123                         Logger::log('Trusting post without JSON-LD signature, The actor fits the HTTP signer.', Logger::DEBUG);
 124                         $trust_source = true;
 125                 } else {
 126                         Logger::log('No JSON-LD signature, different actor.', Logger::DEBUG);
 127                         $trust_source = false;
 128                 }
 129
 130                 self::processActivity($ldactivity, $body, $uid, $trust_source);
 131         }
 132
 133         /**
 134          * Fetches the object type for a given object id
 135          *
 136          * @param array   $activity
 137          * @param string  $object_id Object ID of the the provided object
 138          * @param integer $uid       User ID
 139          *
 140          * @return string with object type
 141          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 142          * @throws \ImagickException
 143          */
 144         private static function fetchObjectType($activity, $object_id, $uid = 0)
 145         {
 146                 if (!empty($activity['as:object'])) {
 147                         $object_type = JsonLD::fetchElement($activity['as:object'], '@type');
 148                         if (!empty($object_type)) {
 149                                 return $object_type;
 150                         }
 151                 }
 152
 153                 if (Item::exists(['uri' => $object_id, 'gravity' => [GRAVITY_PARENT, GRAVITY_COMMENT]])) {
 154                         // We just assume "note" since it doesn't make a difference for the further processing
 155                         return 'as:Note';
 156                 }
 157
 158                 $profile = APContact::getByURL($object_id);
 159                 if (!empty($profile['type'])) {
 160                         return 'as:' . $profile['type'];
 161                 }
 162
 163                 $data = ActivityPub::fetchContent($object_id, $uid);
 164                 if (!empty($data)) {
 165                         $object = JsonLD::compact($data);
 166                         $type = JsonLD::fetchElement($object, '@type');
 167                         if (!empty($type)) {
 168                                 return $type;
 169                         }
 170                 }
 171
 172                 return null;
 173         }
 174
 175         /**
 176          * Prepare the object array
 177          *
 178          * @param array   $activity
 179          * @param integer $uid User ID
 180          * @param         $trust_source
 181          *
 182          * @return array with object data
 183          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 184          * @throws \ImagickException
 185          */
 186         private static function prepareObjectData($activity, $uid, &$trust_source)
 187         {
 188                 $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 189                 if (empty($actor)) {
 190                         Logger::log('Empty actor', Logger::DEBUG);
 191                         return [];
 192                 }
 193
 194                 $type = JsonLD::fetchElement($activity, '@type');
 195
 196                 // Fetch all receivers from to, cc, bto and bcc
 197                 $receivers = self::getReceivers($activity, $actor);
 198
 199                 // When it is a delivery to a personal inbox we add that user to the receivers
 200                 if (!empty($uid)) {
 201                         $additional = ['uid:' . $uid => $uid];
 202                         $receivers = array_merge($receivers, $additional);
 203                 } else {
 204                         // We possibly need some user to fetch private content,
 205                         // so we fetch the first out ot the list.
 206                         $uid = self::getFirstUserFromReceivers($receivers);
 207                 }
 208
 209                 Logger::log('Receivers: ' . $uid . ' - ' . json_encode($receivers), Logger::DEBUG);
 210
 211                 $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
 212                 if (empty($object_id)) {
 213                         Logger::log('No object found', Logger::DEBUG);
 214                         return [];
 215                 }
 216
 217                 if (!is_string($object_id)) {
 218                         Logger::info('Invalid object id', ['object' => $object_id]);
 219                         return [];
 220                 }
 221
 222                 $object_type = self::fetchObjectType($activity, $object_id, $uid);
 223
 224                 // Fetch the content only on activities where this matters
 225                 if (in_array($type, ['as:Create', 'as:Update', 'as:Announce'])) {
 226                         if ($type == 'as:Announce') {
 227                                 $trust_source = false;
 228                         }
 229                         $object_data = self::fetchObject($object_id, $activity['as:object'], $trust_source, $uid);
 230                         if (empty($object_data)) {
 231                                 Logger::log("Object data couldn't be processed", Logger::DEBUG);
 232                                 return [];
 233                         }
 234                         $object_data['object_id'] = $object_id;
 235
 236                         // Test if it is an answer to a mail
 237                         if (DBA::exists('mail', ['uri' => $object_data['reply-to-id']])) {
 238                                 $object_data['directmessage'] = true;
 239                         } else {
 240                                 $object_data['directmessage'] = JsonLD::fetchElement($activity, 'litepub:directMessage');
 241                         }
 242
 243                         // We had been able to retrieve the object data - so we can trust the source
 244                         $trust_source = true;
 245                 } elseif (in_array($type, array_merge(self::ACTIVITY_TYPES, ['as:Follow'])) && in_array($object_type, self::CONTENT_TYPES)) {
 246                         // Create a mostly empty array out of the activity data (instead of the object).
 247                         // This way we later don't have to check for the existence of ech individual array element.
 248                         $object_data = self::processObject($activity);
 249                         $object_data['name'] = $type;
 250                         $object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
 251                         $object_data['object_id'] = $object_id;
 252                         $object_data['object_type'] = ''; // Since we don't fetch the object, we don't know the type
 253                 } elseif (in_array($type, ['as:Add'])) {
 254                         $object_data = [];
 255                         $object_data['id'] = JsonLD::fetchElement($activity, '@id');
 256                         $object_data['target_id'] = JsonLD::fetchElement($activity, 'as:target', '@id');
 257                         $object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
 258                         $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
 259                         $object_data['object_content'] = JsonLD::fetchElement($activity['as:object'], 'as:content', '@type');
 260                 } else {
 261                         $object_data = [];
 262                         $object_data['id'] = JsonLD::fetchElement($activity, '@id');
 263                         $object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
 264                         $object_data['object_actor'] = JsonLD::fetchElement($activity['as:object'], 'as:actor', '@id');
 265                         $object_data['object_object'] = JsonLD::fetchElement($activity['as:object'], 'as:object');
 266                         $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
 267
 268                         // An Undo is done on the object of an object, so we need that type as well
 269                         if ($type == 'as:Undo') {
 270                                 $object_data['object_object_type'] = self::fetchObjectType([], $object_data['object_object'], $uid);
 271                         }
 272                 }
 273
 274                 $object_data = self::addActivityFields($object_data, $activity);
 275
 276                 if (empty($object_data['object_type'])) {
 277                         $object_data['object_type'] = $object_type;
 278                 }
 279
 280                 $object_data['type'] = $type;
 281                 $object_data['actor'] = $actor;
 282                 $object_data['item_receiver'] = $receivers;
 283                 $object_data['receiver'] = array_merge($object_data['receiver'] ?? [], $receivers);
 284
 285                 Logger::log('Processing ' . $object_data['type'] . ' ' . $object_data['object_type'] . ' ' . $object_data['id'], Logger::DEBUG);
 286
 287                 return $object_data;
 288         }
 289
 290         /**
 291          * Fetches the first user id from the receiver array
 292          *
 293          * @param array $receivers Array with receivers
 294          * @return integer user id;
 295          */
 296         public static function getFirstUserFromReceivers($receivers)
 297         {
 298                 foreach ($receivers as $receiver) {
 299                         if (!empty($receiver)) {
 300                                 return $receiver;
 301                         }
 302                 }
 303                 return 0;
 304         }
 305
 306         /**
 307          * Store the unprocessed data into the conversation table
 308          * This has to be done outside the regular function,
 309          * since we store everything - not only item posts.
 310          *
 311          * @param array  $activity Array with activity data
 312          * @param string $body     The raw message
 313          * @throws \Exception
 314          */
 315         private static function storeConversation($activity, $body)
 316         {
 317                 if (empty($body) || empty($activity['id'])) {
 318                         return;
 319                 }
 320
 321                 $conversation = [
 322                         'protocol' => Conversation::PARCEL_ACTIVITYPUB,
 323                         'item-uri' => $activity['id'],
 324                         'reply-to-uri' => $activity['reply-to-id'] ?? '',
 325                         'conversation-href' => $activity['context'] ?? '',
 326                         'conversation-uri' => $activity['conversation'] ?? '',
 327                         'source' => $body,
 328                         'received' => DateTimeFormat::utcNow()];
 329
 330                 DBA::insert('conversation', $conversation, true);
 331         }
 332
 333         /**
 334          * Processes the activity object
 335          *
 336          * @param array   $activity     Array with activity data
 337          * @param string  $body
 338          * @param integer $uid          User ID
 339          * @param boolean $trust_source Do we trust the source?
 340          * @throws \Exception
 341          */
 342         public static function processActivity($activity, $body = '', $uid = null, $trust_source = false)
 343         {
 344                 $type = JsonLD::fetchElement($activity, '@type');
 345                 if (!$type) {
 346                         Logger::log('Empty type', Logger::DEBUG);
 347                         return;
 348                 }
 349
 350                 if (!JsonLD::fetchElement($activity, 'as:object', '@id')) {
 351                         Logger::log('Empty object', Logger::DEBUG);
 352                         return;
 353                 }
 354
 355                 if (!JsonLD::fetchElement($activity, 'as:actor', '@id')) {
 356                         Logger::log('Empty actor', Logger::DEBUG);
 357                         return;
 358
 359                 }
 360
 361                 // Don't trust the source if "actor" differs from "attributedTo". The content could be forged.
 362                 if ($trust_source && ($type == 'as:Create') && is_array($activity['as:object'])) {
 363                         $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 364                         $attributed_to = JsonLD::fetchElement($activity['as:object'], 'as:attributedTo', '@id');
 365                         $trust_source = ($actor == $attributed_to);
 366                         if (!$trust_source) {
 367                                 Logger::log('Not trusting actor: ' . $actor . '. It differs from attributedTo: ' . $attributed_to, Logger::DEBUG);
 368                         }
 369                 }
 370
 371                 // $trust_source is called by reference and is set to true if the content was retrieved successfully
 372                 $object_data = self::prepareObjectData($activity, $uid, $trust_source);
 373                 if (empty($object_data)) {
 374                         Logger::log('No object data found', Logger::DEBUG);
 375                         return;
 376                 }
 377
 378                 if (!$trust_source) {
 379                         Logger::log('No trust for activity type "' . $type . '", so we quit now.', Logger::DEBUG);
 380                         return;
 381                 }
 382
 383                 // Only store content related stuff - and no announces, since they possibly overwrite the original content
 384                 if (in_array($object_data['object_type'], self::CONTENT_TYPES) && ($type != 'as:Announce')) {
 385                         self::storeConversation($object_data, $body);
 386                 }
 387
 388                 // Internal flag for thread completion. See Processor.php
 389                 if (!empty($activity['thread-completion'])) {
 390                         $object_data['thread-completion'] = $activity['thread-completion'];
 391                 }
 392
 393                 switch ($type) {
 394                         case 'as:Create':
 395                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 396                                         ActivityPub\Processor::createItem($object_data);
 397                                 }
 398                                 break;
 399
 400                         case 'as:Add':
 401                                 if ($object_data['object_type'] == 'as:tag') {
 402                                         ActivityPub\Processor::addTag($object_data);
 403                                 }
 404                                 break;
 405
 406                         case 'as:Announce':
 407                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 408                                         $profile = APContact::getByURL($object_data['actor']);
 409                                         // Reshared posts from persons appear as summary at the bottom
 410                                         // If this isn't set, then a single reshare appears on top. This is used for groups.
 411                                         $object_data['thread-completion'] = ($profile['type'] != 'Group');
 412
 413                                         ActivityPub\Processor::createItem($object_data);
 414
 415                                         // Add the bottom reshare information only for persons
 416                                         if ($profile['type'] != 'Group') {
 417                                                 $announce_object_data = self::processObject($activity);
 418                                                 $announce_object_data['name'] = $type;
 419                                                 $announce_object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
 420                                                 $announce_object_data['object_id'] = $object_data['object_id'];
 421                                                 $announce_object_data['object_type'] = $object_data['object_type'];
 422
 423                                                 ActivityPub\Processor::createActivity($announce_object_data, Activity::ANNOUNCE);
 424                                         }
 425                                 }
 426                                 break;
 427
 428                         case 'as:Like':
 429                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 430                                         ActivityPub\Processor::createActivity($object_data, Activity::LIKE);
 431                                 }
 432                                 break;
 433
 434                         case 'as:Dislike':
 435                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 436                                         ActivityPub\Processor::createActivity($object_data, Activity::DISLIKE);
 437                                 }
 438                                 break;
 439
 440                         case 'as:TentativeAccept':
 441                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 442                                         ActivityPub\Processor::createActivity($object_data, Activity::ATTENDMAYBE);
 443                                 }
 444                                 break;
 445
 446                         case 'as:Update':
 447                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 448                                         ActivityPub\Processor::updateItem($object_data);
 449                                 } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 450                                         ActivityPub\Processor::updatePerson($object_data);
 451                                 }
 452                                 break;
 453
 454                         case 'as:Delete':
 455                                 if ($object_data['object_type'] == 'as:Tombstone') {
 456                                         ActivityPub\Processor::deleteItem($object_data);
 457                                 } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 458                                         ActivityPub\Processor::deletePerson($object_data);
 459                                 }
 460                                 break;
 461
 462                         case 'as:Follow':
 463                                 if (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 464                                         ActivityPub\Processor::followUser($object_data);
 465                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 466                                         $object_data['reply-to-id'] = $object_data['object_id'];
 467                                         ActivityPub\Processor::createActivity($object_data, Activity::FOLLOW);
 468                                 }
 469                                 break;
 470
 471                         case 'as:Accept':
 472                                 if ($object_data['object_type'] == 'as:Follow') {
 473                                         ActivityPub\Processor::acceptFollowUser($object_data);
 474                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 475                                         ActivityPub\Processor::createActivity($object_data, Activity::ATTEND);
 476                                 }
 477                                 break;
 478
 479                         case 'as:Reject':
 480                                 if ($object_data['object_type'] == 'as:Follow') {
 481                                         ActivityPub\Processor::rejectFollowUser($object_data);
 482                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 483                                         ActivityPub\Processor::createActivity($object_data, Activity::ATTENDNO);
 484                                 }
 485                                 break;
 486
 487                         case 'as:Undo':
 488                                 if (($object_data['object_type'] == 'as:Follow') &&
 489                                         in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 490                                         ActivityPub\Processor::undoFollowUser($object_data);
 491                                 } elseif (($object_data['object_type'] == 'as:Accept') &&
 492                                         in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 493                                         ActivityPub\Processor::rejectFollowUser($object_data);
 494                                 } elseif (in_array($object_data['object_type'], self::ACTIVITY_TYPES) &&
 495                                         in_array($object_data['object_object_type'], self::CONTENT_TYPES)) {
 496                                         ActivityPub\Processor::undoActivity($object_data);
 497                                 }
 498                                 break;
 499
 500                         default:
 501                                 Logger::log('Unknown activity: ' . $type . ' ' . $object_data['object_type'], Logger::DEBUG);
 502                                 break;
 503                 }
 504         }
 505
 506         /**
 507          * Fetch the receiver list from an activity array
 508          *
 509          * @param array   $activity
 510          * @param string  $actor
 511          * @param array   $tags
 512          * @param boolean $fetch_unlisted
 513          *
 514          * @return array with receivers (user id)
 515          * @throws \Exception
 516          */
 517         private static function getReceivers($activity, $actor, $tags = [], $fetch_unlisted = false)
 518         {
 519                 $receivers = [];
 520
 521                 // When it is an answer, we inherite the receivers from the parent
 522                 $replyto = JsonLD::fetchElement($activity, 'as:inReplyTo', '@id');
 523                 if (!empty($replyto)) {
 524                         // Fix possibly wrong item URI (could be an answer to a plink uri)
 525                         $fixedReplyTo = Item::getURIByLink($replyto);
 526                         $replyto = $fixedReplyTo ?: $replyto;
 527
 528                         $parents = Item::select(['uid'], ['uri' => $replyto]);
 529                         while ($parent = Item::fetch($parents)) {
 530                                 $receivers['uid:' . $parent['uid']] = $parent['uid'];
 531                         }
 532                 }
 533
 534                 if (!empty($actor)) {
 535                         $profile = APContact::getByURL($actor);
 536                         $followers = $profile['followers'] ?? '';
 537
 538                         Logger::log('Actor: ' . $actor . ' - Followers: ' . $followers, Logger::DEBUG);
 539                 } else {
 540                         Logger::log('Empty actor', Logger::DEBUG);
 541                         $followers = '';
 542                 }
 543
 544                 foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
 545                         $receiver_list = JsonLD::fetchElementArray($activity, $element, '@id');
 546                         if (empty($receiver_list)) {
 547                                 continue;
 548                         }
 549
 550                         foreach ($receiver_list as $receiver) {
 551                                 if ($receiver == self::PUBLIC_COLLECTION) {
 552                                         $receivers['uid:0'] = 0;
 553                                 }
 554
 555                                 // Add receiver "-1" for unlisted posts
 556                                 if ($fetch_unlisted && ($receiver == self::PUBLIC_COLLECTION) && ($element == 'as:cc')) {
 557                                         $receivers['uid:-1'] = -1;
 558                                 }
 559
 560                                 if (($receiver == self::PUBLIC_COLLECTION) && !empty($actor)) {
 561                                         // This will most likely catch all OStatus connections to Mastodon
 562                                         $condition = ['alias' => [$actor, Strings::normaliseLink($actor)], 'rel' => [Contact::SHARING, Contact::FRIEND]
 563                                                 , 'archive' => false, 'pending' => false];
 564                                         $contacts = DBA::select('contact', ['uid'], $condition);
 565                                         while ($contact = DBA::fetch($contacts)) {
 566                                                 if ($contact['uid'] != 0) {
 567                                                         $receivers['uid:' . $contact['uid']] = $contact['uid'];
 568                                                 }
 569                                         }
 570                                         DBA::close($contacts);
 571                                 }
 572
 573                                 if (in_array($receiver, [$followers, self::PUBLIC_COLLECTION]) && !empty($actor)) {
 574                                         $receivers = array_merge($receivers, self::getReceiverForActor($actor, $tags));
 575                                         continue;
 576                                 }
 577
 578                                 // Fetching all directly addressed receivers
 579                                 $condition = ['self' => true, 'nurl' => Strings::normaliseLink($receiver)];
 580                                 $contact = DBA::selectFirst('contact', ['uid', 'contact-type'], $condition);
 581                                 if (!DBA::isResult($contact)) {
 582                                         continue;
 583                                 }
 584
 585                                 // Check if the potential receiver is following the actor
 586                                 // Exception: The receiver is targetted via "to" or this is a comment
 587                                 if ((($element != 'as:to') && empty($replyto)) || ($contact['contact-type'] == Contact::TYPE_COMMUNITY)) {
 588                                         $networks = Protocol::FEDERATED;
 589                                         $condition = ['nurl' => Strings::normaliseLink($actor), 'rel' => [Contact::SHARING, Contact::FRIEND],
 590                                                 'network' => $networks, 'archive' => false, 'pending' => false, 'uid' => $contact['uid']];
 591
 592                                         // Forum posts are only accepted from forum contacts
 593                                         if ($contact['contact-type'] == Contact::TYPE_COMMUNITY) {
 594                                                 $condition['rel'] = [Contact::SHARING, Contact::FRIEND, Contact::FOLLOWER];
 595                                         }
 596
 597                                         if (!DBA::exists('contact', $condition)) {
 598                                                 continue;
 599                                         }
 600                                 }
 601
 602                                 $receivers['uid:' . $contact['uid']] = $contact['uid'];
 603                         }
 604                 }
 605
 606                 self::switchContacts($receivers, $actor);
 607
 608                 return $receivers;
 609         }
 610
 611         /**
 612          * Fetch the receiver list of a given actor
 613          *
 614          * @param string $actor
 615          * @param array  $tags
 616          *
 617          * @return array with receivers (user id)
 618          * @throws \Exception
 619          */
 620         public static function getReceiverForActor($actor, $tags)
 621         {
 622                 $receivers = [];
 623                 $networks = Protocol::FEDERATED;
 624                 $condition = ['nurl' => Strings::normaliseLink($actor), 'rel' => [Contact::SHARING, Contact::FRIEND, Contact::FOLLOWER],
 625                         'network' => $networks, 'archive' => false, 'pending' => false];
 626                 $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
 627                 while ($contact = DBA::fetch($contacts)) {
 628                         if (self::isValidReceiverForActor($contact, $actor, $tags)) {
 629                                 $receivers['uid:' . $contact['uid']] = $contact['uid'];
 630                         }
 631                 }
 632                 DBA::close($contacts);
 633                 return $receivers;
 634         }
 635
 636         /**
 637          * Tests if the contact is a valid receiver for this actor
 638          *
 639          * @param array  $contact
 640          * @param string $actor
 641          * @param array  $tags
 642          *
 643          * @return bool with receivers (user id)
 644          * @throws \Exception
 645          */
 646         private static function isValidReceiverForActor($contact, $actor, $tags)
 647         {
 648                 // Public contacts are no valid receiver
 649                 if ($contact['uid'] == 0) {
 650                         return false;
 651                 }
 652
 653                 // Are we following the contact? Then this is a valid receiver
 654                 if (in_array($contact['rel'], [Contact::SHARING, Contact::FRIEND])) {
 655                         return true;
 656                 }
 657
 658                 // When the possible receiver isn't a community, then it is no valid receiver
 659                 $owner = User::getOwnerDataById($contact['uid']);
 660                 if (empty($owner) || ($owner['contact-type'] != Contact::TYPE_COMMUNITY)) {
 661                         return false;
 662                 }
 663
 664                 // Is the community account tagged?
 665                 foreach ($tags as $tag) {
 666                         if ($tag['type'] != 'Mention') {
 667                                 continue;
 668                         }
 669
 670                         if ($tag['href'] == $owner['url']) {
 671                                 return true;
 672                         }
 673                 }
 674
 675                 return false;
 676         }
 677
 678         /**
 679          * Switches existing contacts to ActivityPub
 680          *
 681          * @param integer $cid Contact ID
 682          * @param integer $uid User ID
 683          * @param string  $url Profile URL
 684          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 685          * @throws \ImagickException
 686          */
 687         public static function switchContact($cid, $uid, $url)
 688         {
 689                 if (DBA::exists('contact', ['id' => $cid, 'network' => Protocol::ACTIVITYPUB])) {
 690                         Logger::info('Contact is already ActivityPub', ['id' => $cid, 'uid' => $uid, 'url' => $url]);
 691                         return;
 692                 }
 693
 694                 if (Contact::updateFromProbe($cid, '', true)) {
 695                         Logger::info('Update was successful', ['id' => $cid, 'uid' => $uid, 'url' => $url]);
 696                 }
 697
 698                 // Send a new follow request to be sure that the connection still exists
 699                 if (($uid != 0) && DBA::exists('contact', ['id' => $cid, 'rel' => [Contact::SHARING, Contact::FRIEND], 'network' => Protocol::ACTIVITYPUB])) {
 700                         Logger::info('Contact had been switched to ActivityPub. Sending a new follow request.', ['uid' => $uid, 'url' => $url]);
 701                         ActivityPub\Transmitter::sendActivity('Follow', $url, $uid);
 702                 }
 703         }
 704
 705         /**
 706          *
 707          *
 708          * @param $receivers
 709          * @param $actor
 710          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 711          * @throws \ImagickException
 712          */
 713         private static function switchContacts($receivers, $actor)
 714         {
 715                 if (empty($actor)) {
 716                         return;
 717                 }
 718
 719                 foreach ($receivers as $receiver) {
 720                         $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver, 'network' => Protocol::OSTATUS, 'nurl' => Strings::normaliseLink($actor)]);
 721                         if (DBA::isResult($contact)) {
 722                                 self::switchContact($contact['id'], $receiver, $actor);
 723                         }
 724
 725                         $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver, 'network' => Protocol::OSTATUS, 'alias' => [Strings::normaliseLink($actor), $actor]]);
 726                         if (DBA::isResult($contact)) {
 727                                 self::switchContact($contact['id'], $receiver, $actor);
 728                         }
 729                 }
 730         }
 731
 732         /**
 733          *
 734          *
 735          * @param       $object_data
 736          * @param array $activity
 737          *
 738          * @return mixed
 739          */
 740         private static function addActivityFields($object_data, $activity)
 741         {
 742                 if (!empty($activity['published']) && empty($object_data['published'])) {
 743                         $object_data['published'] = JsonLD::fetchElement($activity, 'as:published', '@value');
 744                 }
 745
 746                 if (!empty($activity['diaspora:guid']) && empty($object_data['diaspora:guid'])) {
 747                         $object_data['diaspora:guid'] = JsonLD::fetchElement($activity, 'diaspora:guid', '@value');
 748                 }
 749
 750                 $object_data['service'] = JsonLD::fetchElement($activity, 'as:instrument', 'as:name', '@type', 'as:Service');
 751                 $object_data['service'] = JsonLD::fetchElement($object_data, 'service', '@value');
 752
 753                 if (!empty($object_data['object_id'])) {
 754                         // Some systems (e.g. GNU Social) don't reply to the "id" field but the "uri" field.
 755                         $objectId = Item::getURIByLink($object_data['object_id']);
 756                         if (!empty($objectId) && ($object_data['object_id'] != $objectId)) {
 757                                 Logger::notice('Fix wrong object-id', ['received' => $object_data['object_id'], 'correct' => $objectId]);
 758                                 $object_data['object_id'] = $objectId;
 759                         }
 760                 }
 761
 762                 return $object_data;
 763         }
 764
 765         /**
 766          * Fetches the object data from external ressources if needed
 767          *
 768          * @param string  $object_id    Object ID of the the provided object
 769          * @param array   $object       The provided object array
 770          * @param boolean $trust_source Do we trust the provided object?
 771          * @param integer $uid          User ID for the signature that we use to fetch data
 772          *
 773          * @return array|false with trusted and valid object data
 774          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 775          * @throws \ImagickException
 776          */
 777         private static function fetchObject(string $object_id, array $object = [], bool $trust_source = false, int $uid = 0)
 778         {
 779                 // By fetching the type we check if the object is complete.
 780                 $type = JsonLD::fetchElement($object, '@type');
 781
 782                 if (!$trust_source || empty($type)) {
 783                         $data = ActivityPub::fetchContent($object_id, $uid);
 784                         if (!empty($data)) {
 785                                 $object = JsonLD::compact($data);
 786                                 Logger::log('Fetched content for ' . $object_id, Logger::DEBUG);
 787                         } else {
 788                                 Logger::log('Empty content for ' . $object_id . ', check if content is available locally.', Logger::DEBUG);
 789
 790                                 $item = Item::selectFirst([], ['uri' => $object_id]);
 791                                 if (!DBA::isResult($item)) {
 792                                         Logger::log('Object with url ' . $object_id . ' was not found locally.', Logger::DEBUG);
 793                                         return false;
 794                                 }
 795                                 Logger::log('Using already stored item for url ' . $object_id, Logger::DEBUG);
 796                                 $data = ActivityPub\Transmitter::createNote($item);
 797                                 $object = JsonLD::compact($data);
 798                         }
 799                 } else {
 800                         Logger::log('Using original object for url ' . $object_id, Logger::DEBUG);
 801                 }
 802
 803                 $type = JsonLD::fetchElement($object, '@type');
 804
 805                 if (empty($type)) {
 806                         Logger::log('Empty type', Logger::DEBUG);
 807                         return false;
 808                 }
 809
 810                 if (in_array($type, self::CONTENT_TYPES)) {
 811                         return self::processObject($object);
 812                 }
 813
 814                 if ($type == 'as:Announce') {
 815                         $object_id = JsonLD::fetchElement($object, 'object', '@id');
 816                         if (empty($object_id) || !is_string($object_id)) {
 817                                 return false;
 818                         }
 819                         return self::fetchObject($object_id, [], false, $uid);
 820                 }
 821
 822                 Logger::log('Unhandled object type: ' . $type, Logger::DEBUG);
 823                 return false;
 824         }
 825
 826         /**
 827          * Convert tags from JSON-LD format into a simplified format
 828          *
 829          * @param array $tags Tags in JSON-LD format
 830          *
 831          * @return array with tags in a simplified format
 832          */
 833         private static function processTags($tags)
 834         {
 835                 $taglist = [];
 836
 837                 if (empty($tags)) {
 838                         return [];
 839                 }
 840
 841                 foreach ($tags as $tag) {
 842                         if (empty($tag)) {
 843                                 continue;
 844                         }
 845
 846                         $element = ['type' => str_replace('as:', '', JsonLD::fetchElement($tag, '@type')),
 847                                 'href' => JsonLD::fetchElement($tag, 'as:href', '@id'),
 848                                 'name' => JsonLD::fetchElement($tag, 'as:name', '@value')];
 849
 850                         if (empty($element['type'])) {
 851                                 continue;
 852                         }
 853
 854                         $taglist[] = $element;
 855                 }
 856                 return $taglist;
 857         }
 858
 859         /**
 860          * Convert emojis from JSON-LD format into a simplified format
 861          *
 862          * @param $emojis
 863          * @return array with emojis in a simplified format
 864          */
 865         private static function processEmojis($emojis)
 866         {
 867                 $emojilist = [];
 868
 869                 if (empty($emojis)) {
 870                         return [];
 871                 }
 872
 873                 foreach ($emojis as $emoji) {
 874                         if (empty($emoji) || (JsonLD::fetchElement($emoji, '@type') != 'toot:Emoji') || empty($emoji['as:icon'])) {
 875                                 continue;
 876                         }
 877
 878                         $url = JsonLD::fetchElement($emoji['as:icon'], 'as:url', '@id');
 879                         $element = ['name' => JsonLD::fetchElement($emoji, 'as:name', '@value'),
 880                                 'href' => $url];
 881
 882                         $emojilist[] = $element;
 883                 }
 884                 return $emojilist;
 885         }
 886
 887         /**
 888          * Convert attachments from JSON-LD format into a simplified format
 889          *
 890          * @param array $attachments Attachments in JSON-LD format
 891          *
 892          * @return array with attachmants in a simplified format
 893          */
 894         private static function processAttachments($attachments)
 895         {
 896                 $attachlist = [];
 897
 898                 if (empty($attachments)) {
 899                         return [];
 900                 }
 901
 902                 foreach ($attachments as $attachment) {
 903                         if (empty($attachment)) {
 904                                 continue;
 905                         }
 906
 907                         $attachlist[] = ['type' => str_replace('as:', '', JsonLD::fetchElement($attachment, '@type')),
 908                                 'mediaType' => JsonLD::fetchElement($attachment, 'as:mediaType', '@value'),
 909                                 'name' => JsonLD::fetchElement($attachment, 'as:name', '@value'),
 910                                 'url' => JsonLD::fetchElement($attachment, 'as:url', '@id')];
 911                 }
 912                 return $attachlist;
 913         }
 914
 915         /**
 916          * Fetch the original source or content with the "language" Markdown or HTML
 917          *
 918          * @param array $object
 919          * @param array $object_data
 920          *
 921          * @return array
 922          * @throws \Exception
 923          */
 924         private static function getSource($object, $object_data)
 925         {
 926                 $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/bbcode');
 927                 $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
 928                 if (!empty($object_data['source'])) {
 929                         return $object_data;
 930                 }
 931
 932                 $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/markdown');
 933                 $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
 934                 if (!empty($object_data['source'])) {
 935                         $object_data['source'] = Markdown::toBBCode($object_data['source']);
 936                         return $object_data;
 937                 }
 938
 939                 $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/html');
 940                 $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
 941                 if (!empty($object_data['source'])) {
 942                         $object_data['source'] = HTML::toBBCode($object_data['source']);
 943                         return $object_data;
 944                 }
 945
 946                 return $object_data;
 947         }
 948
 949         /**
 950          * Fetches data from the object part of an activity
 951          *
 952          * @param array $object
 953          *
 954          * @return array
 955          * @throws \Exception
 956          */
 957         private static function processObject($object)
 958         {
 959                 if (!JsonLD::fetchElement($object, '@id')) {
 960                         return false;
 961                 }
 962
 963                 $object_data = [];
 964                 $object_data['object_type'] = JsonLD::fetchElement($object, '@type');
 965                 $object_data['id'] = JsonLD::fetchElement($object, '@id');
 966                 $object_data['reply-to-id'] = JsonLD::fetchElement($object, 'as:inReplyTo', '@id');
 967
 968                 // An empty "id" field is translated to "./" by the compactor, so we have to check for this content
 969                 if (empty($object_data['reply-to-id']) || ($object_data['reply-to-id'] == './')) {
 970                         $object_data['reply-to-id'] = $object_data['id'];
 971                 } else {
 972                         // Some systems (e.g. GNU Social) don't reply to the "id" field but the "uri" field.
 973                         $replyToId = Item::getURIByLink($object_data['reply-to-id']);
 974                         if (!empty($replyToId) && ($object_data['reply-to-id'] != $replyToId)) {
 975                                 Logger::notice('Fix wrong reply-to', ['received' => $object_data['reply-to-id'], 'correct' => $replyToId]);
 976                                 $object_data['reply-to-id'] = $replyToId;
 977                         }
 978                 }
 979
 980                 $object_data['published'] = JsonLD::fetchElement($object, 'as:published', '@value');
 981                 $object_data['updated'] = JsonLD::fetchElement($object, 'as:updated', '@value');
 982
 983                 if (empty($object_data['updated'])) {
 984                         $object_data['updated'] = $object_data['published'];
 985                 }
 986
 987                 if (empty($object_data['published']) && !empty($object_data['updated'])) {
 988                         $object_data['published'] = $object_data['updated'];
 989                 }
 990
 991                 $actor = JsonLD::fetchElement($object, 'as:attributedTo', '@id');
 992                 if (empty($actor)) {
 993                         $actor = JsonLD::fetchElement($object, 'as:actor', '@id');
 994                 }
 995
 996                 $object_data['diaspora:guid'] = JsonLD::fetchElement($object, 'diaspora:guid', '@value');
 997                 $object_data['diaspora:comment'] = JsonLD::fetchElement($object, 'diaspora:comment', '@value');
 998                 $object_data['diaspora:like'] = JsonLD::fetchElement($object, 'diaspora:like', '@value');
 999                 $object_data['actor'] = $object_data['author'] = $actor;
1000                 $object_data['context'] = JsonLD::fetchElement($object, 'as:context', '@id');
1001                 $object_data['conversation'] = JsonLD::fetchElement($object, 'ostatus:conversation', '@id');
1002                 $object_data['sensitive'] = JsonLD::fetchElement($object, 'as:sensitive');
1003                 $object_data['name'] = JsonLD::fetchElement($object, 'as:name', '@value');
1004                 $object_data['summary'] = JsonLD::fetchElement($object, 'as:summary', '@value');
1005                 $object_data['content'] = JsonLD::fetchElement($object, 'as:content', '@value');
1006                 $object_data = self::getSource($object, $object_data);
1007                 $object_data['start-time'] = JsonLD::fetchElement($object, 'as:startTime', '@value');
1008                 $object_data['end-time'] = JsonLD::fetchElement($object, 'as:endTime', '@value');
1009                 $object_data['location'] = JsonLD::fetchElement($object, 'as:location', 'as:name', '@type', 'as:Place');
1010                 $object_data['location'] = JsonLD::fetchElement($object_data, 'location', '@value');
1011                 $object_data['latitude'] = JsonLD::fetchElement($object, 'as:location', 'as:latitude', '@type', 'as:Place');
1012                 $object_data['latitude'] = JsonLD::fetchElement($object_data, 'latitude', '@value');
1013                 $object_data['longitude'] = JsonLD::fetchElement($object, 'as:location', 'as:longitude', '@type', 'as:Place');
1014                 $object_data['longitude'] = JsonLD::fetchElement($object_data, 'longitude', '@value');
1015                 $object_data['attachments'] = self::processAttachments(JsonLD::fetchElementArray($object, 'as:attachment'));
1016                 $object_data['tags'] = self::processTags(JsonLD::fetchElementArray($object, 'as:tag'));
1017                 $object_data['emojis'] = self::processEmojis(JsonLD::fetchElementArray($object, 'as:tag', 'toot:Emoji'));
1018                 $object_data['generator'] = JsonLD::fetchElement($object, 'as:generator', 'as:name', '@type', 'as:Application');
1019                 $object_data['generator'] = JsonLD::fetchElement($object_data, 'generator', '@value');
1020                 $object_data['alternate-url'] = JsonLD::fetchElement($object, 'as:url', '@id');
1021
1022                 // Special treatment for Hubzilla links
1023                 if (is_array($object_data['alternate-url'])) {
1024                         $object_data['alternate-url'] = JsonLD::fetchElement($object_data['alternate-url'], 'as:href', '@id');
1025
1026                         if (!is_string($object_data['alternate-url'])) {
1027                                 $object_data['alternate-url'] = JsonLD::fetchElement($object['as:url'], 'as:href', '@id');
1028                         }
1029                 }
1030
1031                 $object_data['receiver'] = self::getReceivers($object, $object_data['actor'], $object_data['tags'], true);
1032                 $object_data['unlisted'] = in_array(-1, $object_data['receiver']);
1033                 unset($object_data['receiver']['uid:-1']);
1034
1035                 // Common object data:
1036
1037                 // Unhandled
1038                 // @context, type, actor, signature, mediaType, duration, replies, icon
1039
1040                 // Also missing: (Defined in the standard, but currently unused)
1041                 // audience, preview, endTime, startTime, image
1042
1043                 // Data in Notes:
1044
1045                 // Unhandled
1046                 // contentMap, announcement_count, announcements, context_id, likes, like_count
1047                 // inReplyToStatusId, shares, quoteUrl, statusnetConversationId
1048
1049                 // Data in video:
1050
1051                 // To-Do?
1052                 // category, licence, language, commentsEnabled
1053
1054                 // Unhandled
1055                 // views, waitTranscoding, state, support, subtitleLanguage
1056                 // likes, dislikes, shares, comments
1057
1058                 return $object_data;
1059         }
1060 }