src/Protocol/ActivityPub/Receiver.php

   1 <?php
   2 /**
   3  * @file src/Protocol/ActivityPub/Receiver.php
   4  */
   5 namespace Friendica\Protocol\ActivityPub;
   6
   7 use Friendica\Database\DBA;
   8 use Friendica\Core\Logger;
   9 use Friendica\Core\Protocol;
  10 use Friendica\Model\Contact;
  11 use Friendica\Model\APContact;
  12 use Friendica\Model\Conversation;
  13 use Friendica\Model\Item;
  14 use Friendica\Model\User;
  15 use Friendica\Protocol\ActivityPub;
  16 use Friendica\Util\DateTimeFormat;
  17 use Friendica\Util\HTTPSignature;
  18 use Friendica\Util\JsonLD;
  19 use Friendica\Util\LDSignature;
  20 use Friendica\Util\Strings;
  21
  22 /**
  23  * @brief ActivityPub Receiver Protocol class
  24  *
  25  * To-Do:
  26  * - Undo Announce
  27  *
  28  * Check what this is meant to do:
  29  * - Add
  30  * - Block
  31  * - Flag
  32  * - Remove
  33  * - Undo Block
  34  */
  35 class Receiver
  36 {
  37         const PUBLIC_COLLECTION = 'as:Public';
  38         const ACCOUNT_TYPES = ['as:Person', 'as:Organization', 'as:Service', 'as:Group', 'as:Application'];
  39         const CONTENT_TYPES = ['as:Note', 'as:Article', 'as:Video', 'as:Image', 'as:Event'];
  40         const ACTIVITY_TYPES = ['as:Like', 'as:Dislike', 'as:Accept', 'as:Reject', 'as:TentativeAccept'];
  41
  42         /**
  43          * Checks if the web request is done for the AP protocol
  44          *
  45          * @return bool is it AP?
  46          */
  47         public static function isRequest()
  48         {
  49                 return stristr(defaults($_SERVER, 'HTTP_ACCEPT', ''), 'application/activity+json') ||
  50                         stristr(defaults($_SERVER, 'HTTP_ACCEPT', ''), 'application/ld+json');
  51         }
  52
  53         /**
  54          * Checks incoming message from the inbox
  55          *
  56          * @param         $body
  57          * @param         $header
  58          * @param integer $uid User ID
  59          * @throws \Exception
  60          */
  61         public static function processInbox($body, $header, $uid)
  62         {
  63                 $http_signer = HTTPSignature::getSigner($body, $header);
  64                 if (empty($http_signer)) {
  65                         Logger::warning('Invalid HTTP signature, message will be discarded.');
  66                         return;
  67                 } else {
  68                         Logger::info('Valid HTTP signature', ['signer' => $http_signer]);
  69                 }
  70
  71                 $activity = json_decode($body, true);
  72
  73                 if (empty($activity)) {
  74                         Logger::warning('Invalid body.');
  75                         return;
  76                 }
  77
  78                 $ldactivity = JsonLD::compact($activity);
  79
  80                 $actor = JsonLD::fetchElement($ldactivity, 'as:actor', '@id');
  81
  82                 Logger::info('Message for user ' . $uid . ' is from actor ' . $actor);
  83
  84                 if (LDSignature::isSigned($activity)) {
  85                         $ld_signer = LDSignature::getSigner($activity);
  86                         if (empty($ld_signer)) {
  87                                 Logger::log('Invalid JSON-LD signature from ' . $actor, Logger::DEBUG);
  88                         }
  89                         if (!empty($ld_signer && ($actor == $http_signer))) {
  90                                 Logger::log('The HTTP and the JSON-LD signature belong to ' . $ld_signer, Logger::DEBUG);
  91                                 $trust_source = true;
  92                         } elseif (!empty($ld_signer)) {
  93                                 Logger::log('JSON-LD signature is signed by ' . $ld_signer, Logger::DEBUG);
  94                                 $trust_source = true;
  95                         } elseif ($actor == $http_signer) {
  96                                 Logger::log('Bad JSON-LD signature, but HTTP signer fits the actor.', Logger::DEBUG);
  97                                 $trust_source = true;
  98                         } else {
  99                                 Logger::log('Invalid JSON-LD signature and the HTTP signer is different.', Logger::DEBUG);
 100                                 $trust_source = false;
 101                         }
 102                 } elseif ($actor == $http_signer) {
 103                         Logger::log('Trusting post without JSON-LD signature, The actor fits the HTTP signer.', Logger::DEBUG);
 104                         $trust_source = true;
 105                 } else {
 106                         Logger::log('No JSON-LD signature, different actor.', Logger::DEBUG);
 107                         $trust_source = false;
 108                 }
 109
 110                 self::processActivity($ldactivity, $body, $uid, $trust_source);
 111         }
 112
 113         /**
 114          * Fetches the object type for a given object id
 115          *
 116          * @param array   $activity
 117          * @param string  $object_id Object ID of the the provided object
 118          * @param integer $uid       User ID
 119          *
 120          * @return string with object type
 121          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 122          * @throws \ImagickException
 123          */
 124         private static function fetchObjectType($activity, $object_id, $uid = 0)
 125         {
 126                 if (!empty($activity['as:object'])) {
 127                         $object_type = JsonLD::fetchElement($activity['as:object'], '@type');
 128                         if (!empty($object_type)) {
 129                                 return $object_type;
 130                         }
 131                 }
 132
 133                 if (Item::exists(['uri' => $object_id, 'gravity' => [GRAVITY_PARENT, GRAVITY_COMMENT]])) {
 134                         // We just assume "note" since it doesn't make a difference for the further processing
 135                         return 'as:Note';
 136                 }
 137
 138                 $profile = APContact::getByURL($object_id);
 139                 if (!empty($profile['type'])) {
 140                         return 'as:' . $profile['type'];
 141                 }
 142
 143                 $data = ActivityPub::fetchContent($object_id, $uid);
 144                 if (!empty($data)) {
 145                         $object = JsonLD::compact($data);
 146                         $type = JsonLD::fetchElement($object, '@type');
 147                         if (!empty($type)) {
 148                                 return $type;
 149                         }
 150                 }
 151
 152                 return null;
 153         }
 154
 155         /**
 156          * Prepare the object array
 157          *
 158          * @param array   $activity
 159          * @param integer $uid User ID
 160          * @param         $trust_source
 161          *
 162          * @return array with object data
 163          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 164          * @throws \ImagickException
 165          */
 166         private static function prepareObjectData($activity, $uid, &$trust_source)
 167         {
 168                 $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 169                 if (empty($actor)) {
 170                         Logger::log('Empty actor', Logger::DEBUG);
 171                         return [];
 172                 }
 173
 174                 $type = JsonLD::fetchElement($activity, '@type');
 175
 176                 // Fetch all receivers from to, cc, bto and bcc
 177                 $receivers = self::getReceivers($activity, $actor);
 178
 179                 // When it is a delivery to a personal inbox we add that user to the receivers
 180                 if (!empty($uid)) {
 181                         $additional = ['uid:' . $uid => $uid];
 182                         $receivers = array_merge($receivers, $additional);
 183                 } else {
 184                         // We possibly need some user to fetch private content,
 185                         // so we fetch the first out ot the list.
 186                         $uid = self::getFirstUserFromReceivers($receivers);
 187                 }
 188
 189                 Logger::log('Receivers: ' . $uid . ' - ' . json_encode($receivers), Logger::DEBUG);
 190
 191                 $object_id = JsonLD::fetchElement($activity, 'as:object', '@id');
 192                 if (empty($object_id)) {
 193                         Logger::log('No object found', Logger::DEBUG);
 194                         return [];
 195                 }
 196
 197                 if (!is_string($object_id)) {
 198                         Logger::info('Invalid object id', ['object' => $object_id]);
 199                         return [];
 200                 }
 201
 202                 $object_type = self::fetchObjectType($activity, $object_id, $uid);
 203
 204                 // Fetch the content only on activities where this matters
 205                 if (in_array($type, ['as:Create', 'as:Update', 'as:Announce'])) {
 206                         if ($type == 'as:Announce') {
 207                                 $trust_source = false;
 208                         }
 209                         $object_data = self::fetchObject($object_id, $activity['as:object'], $trust_source, $uid);
 210                         if (empty($object_data)) {
 211                                 Logger::log("Object data couldn't be processed", Logger::DEBUG);
 212                                 return [];
 213                         }
 214                         $object_data['object_id'] = $object_id;
 215
 216                         // Test if it is an answer to a mail
 217                         if (DBA::exists('mail', ['uri' => $object_data['reply-to-id']])) {
 218                                 $object_data['directmessage'] = true;
 219                         } else {
 220                                 $object_data['directmessage'] = JsonLD::fetchElement($activity, 'litepub:directMessage');
 221                         }
 222
 223                         // We had been able to retrieve the object data - so we can trust the source
 224                         $trust_source = true;
 225                 } elseif (in_array($type, array_merge(self::ACTIVITY_TYPES, ['as:Follow'])) && in_array($object_type, self::CONTENT_TYPES)) {
 226                         // Create a mostly empty array out of the activity data (instead of the object).
 227                         // This way we later don't have to check for the existence of ech individual array element.
 228                         $object_data = self::processObject($activity);
 229                         $object_data['name'] = $type;
 230                         $object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
 231                         $object_data['object_id'] = $object_id;
 232                         $object_data['object_type'] = ''; // Since we don't fetch the object, we don't know the type
 233                 } elseif (in_array($type, ['as:Add'])) {
 234                         $object_data = [];
 235                         $object_data['id'] = JsonLD::fetchElement($activity, '@id');
 236                         $object_data['target_id'] = JsonLD::fetchElement($activity, 'as:target', '@id');
 237                         $object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
 238                         $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
 239                         $object_data['object_content'] = JsonLD::fetchElement($activity['as:object'], 'as:content', '@type');
 240                 } else {
 241                         $object_data = [];
 242                         $object_data['id'] = JsonLD::fetchElement($activity, '@id');
 243                         $object_data['object_id'] = JsonLD::fetchElement($activity, 'as:object', '@id');
 244                         $object_data['object_actor'] = JsonLD::fetchElement($activity['as:object'], 'as:actor', '@id');
 245                         $object_data['object_object'] = JsonLD::fetchElement($activity['as:object'], 'as:object');
 246                         $object_data['object_type'] = JsonLD::fetchElement($activity['as:object'], '@type');
 247
 248                         // An Undo is done on the object of an object, so we need that type as well
 249                         if ($type == 'as:Undo') {
 250                                 $object_data['object_object_type'] = self::fetchObjectType([], $object_data['object_object'], $uid);
 251                         }
 252                 }
 253
 254                 $object_data = self::addActivityFields($object_data, $activity);
 255
 256                 if (empty($object_data['object_type'])) {
 257                         $object_data['object_type'] = $object_type;
 258                 }
 259
 260                 $object_data['type'] = $type;
 261                 $object_data['actor'] = $actor;
 262                 $object_data['item_receiver'] = $receivers;
 263                 $object_data['receiver'] = array_merge(defaults($object_data, 'receiver', []), $receivers);
 264
 265                 Logger::log('Processing ' . $object_data['type'] . ' ' . $object_data['object_type'] . ' ' . $object_data['id'], Logger::DEBUG);
 266
 267                 return $object_data;
 268         }
 269
 270         /**
 271          * Fetches the first user id from the receiver array
 272          *
 273          * @param array $receivers Array with receivers
 274          * @return integer user id;
 275          */
 276         public static function getFirstUserFromReceivers($receivers)
 277         {
 278                 foreach ($receivers as $receiver) {
 279                         if (!empty($receiver)) {
 280                                 return $receiver;
 281                         }
 282                 }
 283                 return 0;
 284         }
 285
 286         /**
 287          * Store the unprocessed data into the conversation table
 288          * This has to be done outside the regular function,
 289          * since we store everything - not only item posts.
 290          *
 291          * @param array  $activity Array with activity data
 292          * @param string $body     The raw message
 293          * @throws \Exception
 294          */
 295         private static function storeConversation($activity, $body)
 296         {
 297                 if (empty($body) || empty($activity['id'])) {
 298                         return;
 299                 }
 300
 301                 $conversation = [
 302                         'protocol' => Conversation::PARCEL_ACTIVITYPUB,
 303                         'item-uri' => $activity['id'],
 304                         'reply-to-uri' => defaults($activity, 'reply-to-id', ''),
 305                         'conversation-href' => defaults($activity, 'context', ''),
 306                         'conversation-uri' => defaults($activity, 'conversation', ''),
 307                         'source' => $body,
 308                         'received' => DateTimeFormat::utcNow()];
 309
 310                 DBA::insert('conversation', $conversation, true);
 311         }
 312
 313         /**
 314          * Processes the activity object
 315          *
 316          * @param array   $activity     Array with activity data
 317          * @param string  $body
 318          * @param integer $uid          User ID
 319          * @param boolean $trust_source Do we trust the source?
 320          * @throws \Exception
 321          */
 322         public static function processActivity($activity, $body = '', $uid = null, $trust_source = false)
 323         {
 324                 $type = JsonLD::fetchElement($activity, '@type');
 325                 if (!$type) {
 326                         Logger::log('Empty type', Logger::DEBUG);
 327                         return;
 328                 }
 329
 330                 if (!JsonLD::fetchElement($activity, 'as:object', '@id')) {
 331                         Logger::log('Empty object', Logger::DEBUG);
 332                         return;
 333                 }
 334
 335                 if (!JsonLD::fetchElement($activity, 'as:actor', '@id')) {
 336                         Logger::log('Empty actor', Logger::DEBUG);
 337                         return;
 338
 339                 }
 340
 341                 // Don't trust the source if "actor" differs from "attributedTo". The content could be forged.
 342                 if ($trust_source && ($type == 'as:Create') && is_array($activity['as:object'])) {
 343                         $actor = JsonLD::fetchElement($activity, 'as:actor', '@id');
 344                         $attributed_to = JsonLD::fetchElement($activity['as:object'], 'as:attributedTo', '@id');
 345                         $trust_source = ($actor == $attributed_to);
 346                         if (!$trust_source) {
 347                                 Logger::log('Not trusting actor: ' . $actor . '. It differs from attributedTo: ' . $attributed_to, Logger::DEBUG);
 348                         }
 349                 }
 350
 351                 // $trust_source is called by reference and is set to true if the content was retrieved successfully
 352                 $object_data = self::prepareObjectData($activity, $uid, $trust_source);
 353                 if (empty($object_data)) {
 354                         Logger::log('No object data found', Logger::DEBUG);
 355                         return;
 356                 }
 357
 358                 if (!$trust_source) {
 359                         Logger::log('No trust for activity type "' . $type . '", so we quit now.', Logger::DEBUG);
 360                         return;
 361                 }
 362
 363                 // Only store content related stuff - and no announces, since they possibly overwrite the original content
 364                 if (in_array($object_data['object_type'], self::CONTENT_TYPES) && ($type != 'as:Announce')) {
 365                         self::storeConversation($object_data, $body);
 366                 }
 367
 368                 // Internal flag for thread completion. See Processor.php
 369                 if (!empty($activity['thread-completion'])) {
 370                         $object_data['thread-completion'] = $activity['thread-completion'];
 371                 }
 372
 373                 switch ($type) {
 374                         case 'as:Create':
 375                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 376                                         ActivityPub\Processor::createItem($object_data);
 377                                 }
 378                                 break;
 379
 380                         case 'as:Add':
 381                                 if ($object_data['object_type'] == 'as:tag') {
 382                                         ActivityPub\Processor::addTag($object_data);
 383                                 }
 384                                 break;
 385
 386                         case 'as:Announce':
 387                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 388                                         $profile = APContact::getByURL($object_data['actor']);
 389                                         if ($profile['type'] == 'Person') {
 390                                                 // Reshared posts from persons appear as summary at the bottom
 391                                                 // If this isn't set, then a single reshare appears on top. This is used for groups.
 392                                                 $object_data['thread-completion'] = true;
 393                                         }
 394                                         ActivityPub\Processor::createItem($object_data);
 395
 396                                         // Add the bottom reshare information only for persons
 397                                         if ($profile['type'] == 'Person') {
 398                                                 $announce_object_data = self::processObject($activity);
 399                                                 $announce_object_data['name'] = $type;
 400                                                 $announce_object_data['author'] = JsonLD::fetchElement($activity, 'as:actor', '@id');
 401                                                 $announce_object_data['object_id'] = $object_data['object_id'];
 402                                                 $announce_object_data['object_type'] = $object_data['object_type'];
 403
 404                                                 ActivityPub\Processor::createActivity($announce_object_data, ACTIVITY2_ANNOUNCE);
 405                                         }
 406                                 }
 407                                 break;
 408
 409                         case 'as:Like':
 410                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 411                                         ActivityPub\Processor::createActivity($object_data, ACTIVITY_LIKE);
 412                                 }
 413                                 break;
 414
 415                         case 'as:Dislike':
 416                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 417                                         ActivityPub\Processor::createActivity($object_data, ACTIVITY_DISLIKE);
 418                                 }
 419                                 break;
 420
 421                         case 'as:TentativeAccept':
 422                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 423                                         ActivityPub\Processor::createActivity($object_data, ACTIVITY_ATTENDMAYBE);
 424                                 }
 425                                 break;
 426
 427                         case 'as:Update':
 428                                 if (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 429                                         ActivityPub\Processor::updateItem($object_data);
 430                                 } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 431                                         ActivityPub\Processor::updatePerson($object_data);
 432                                 }
 433                                 break;
 434
 435                         case 'as:Delete':
 436                                 if ($object_data['object_type'] == 'as:Tombstone') {
 437                                         ActivityPub\Processor::deleteItem($object_data);
 438                                 } elseif (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 439                                         ActivityPub\Processor::deletePerson($object_data);
 440                                 }
 441                                 break;
 442
 443                         case 'as:Follow':
 444                                 if (in_array($object_data['object_type'], self::ACCOUNT_TYPES)) {
 445                                         ActivityPub\Processor::followUser($object_data);
 446                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 447                                         $object_data['reply-to-id'] = $object_data['object_id'];
 448                                         ActivityPub\Processor::createActivity($object_data, ACTIVITY_FOLLOW);
 449                                 }
 450                                 break;
 451
 452                         case 'as:Accept':
 453                                 if ($object_data['object_type'] == 'as:Follow') {
 454                                         ActivityPub\Processor::acceptFollowUser($object_data);
 455                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 456                                         ActivityPub\Processor::createActivity($object_data, ACTIVITY_ATTEND);
 457                                 }
 458                                 break;
 459
 460                         case 'as:Reject':
 461                                 if ($object_data['object_type'] == 'as:Follow') {
 462                                         ActivityPub\Processor::rejectFollowUser($object_data);
 463                                 } elseif (in_array($object_data['object_type'], self::CONTENT_TYPES)) {
 464                                         ActivityPub\Processor::createActivity($object_data, ACTIVITY_ATTENDNO);
 465                                 }
 466                                 break;
 467
 468                         case 'as:Undo':
 469                                 if (($object_data['object_type'] == 'as:Follow') &&
 470                                         in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 471                                         ActivityPub\Processor::undoFollowUser($object_data);
 472                                 } elseif (($object_data['object_type'] == 'as:Accept') &&
 473                                         in_array($object_data['object_object_type'], self::ACCOUNT_TYPES)) {
 474                                         ActivityPub\Processor::rejectFollowUser($object_data);
 475                                 } elseif (in_array($object_data['object_type'], self::ACTIVITY_TYPES) &&
 476                                         in_array($object_data['object_object_type'], self::CONTENT_TYPES)) {
 477                                         ActivityPub\Processor::undoActivity($object_data);
 478                                 }
 479                                 break;
 480
 481                         default:
 482                                 Logger::log('Unknown activity: ' . $type . ' ' . $object_data['object_type'], Logger::DEBUG);
 483                                 break;
 484                 }
 485         }
 486
 487         /**
 488          * Fetch the receiver list from an activity array
 489          *
 490          * @param array  $activity
 491          * @param string $actor
 492          * @param array  $tags
 493          *
 494          * @return array with receivers (user id)
 495          * @throws \Exception
 496          */
 497         private static function getReceivers($activity, $actor, $tags = [])
 498         {
 499                 $receivers = [];
 500
 501                 // When it is an answer, we inherite the receivers from the parent
 502                 $replyto = JsonLD::fetchElement($activity, 'as:inReplyTo', '@id');
 503                 if (!empty($replyto)) {
 504                         $parents = Item::select(['uid'], ['uri' => $replyto]);
 505                         while ($parent = Item::fetch($parents)) {
 506                                 $receivers['uid:' . $parent['uid']] = $parent['uid'];
 507                         }
 508                 }
 509
 510                 if (!empty($actor)) {
 511                         $profile = APContact::getByURL($actor);
 512                         $followers = defaults($profile, 'followers', '');
 513
 514                         Logger::log('Actor: ' . $actor . ' - Followers: ' . $followers, Logger::DEBUG);
 515                 } else {
 516                         Logger::log('Empty actor', Logger::DEBUG);
 517                         $followers = '';
 518                 }
 519
 520                 foreach (['as:to', 'as:cc', 'as:bto', 'as:bcc'] as $element) {
 521                         $receiver_list = JsonLD::fetchElementArray($activity, $element, '@id');
 522                         if (empty($receiver_list)) {
 523                                 continue;
 524                         }
 525
 526                         foreach ($receiver_list as $receiver) {
 527                                 if ($receiver == self::PUBLIC_COLLECTION) {
 528                                         $receivers['uid:0'] = 0;
 529                                 }
 530
 531                                 if (($receiver == self::PUBLIC_COLLECTION) && !empty($actor)) {
 532                                         // This will most likely catch all OStatus connections to Mastodon
 533                                         $condition = ['alias' => [$actor, Strings::normaliseLink($actor)], 'rel' => [Contact::SHARING, Contact::FRIEND]
 534                                                 , 'archive' => false, 'pending' => false];
 535                                         $contacts = DBA::select('contact', ['uid'], $condition);
 536                                         while ($contact = DBA::fetch($contacts)) {
 537                                                 if ($contact['uid'] != 0) {
 538                                                         $receivers['uid:' . $contact['uid']] = $contact['uid'];
 539                                                 }
 540                                         }
 541                                         DBA::close($contacts);
 542                                 }
 543
 544                                 if (in_array($receiver, [$followers, self::PUBLIC_COLLECTION]) && !empty($actor)) {
 545                                         $receivers = array_merge($receivers, self::getReceiverForActor($actor, $tags));
 546                                         continue;
 547                                 }
 548
 549                                 // Fetching all directly addressed receivers
 550                                 $condition = ['self' => true, 'nurl' => Strings::normaliseLink($receiver)];
 551                                 $contact = DBA::selectFirst('contact', ['uid', 'contact-type'], $condition);
 552                                 if (!DBA::isResult($contact)) {
 553                                         continue;
 554                                 }
 555
 556                                 // Check if the potential receiver is following the actor
 557                                 // Exception: The receiver is targetted via "to" or this is a comment
 558                                 if ((($element != 'as:to') && empty($replyto)) || ($contact['contact-type'] == Contact::TYPE_COMMUNITY)) {
 559                                         $networks = [Protocol::ACTIVITYPUB, Protocol::DFRN, Protocol::DIASPORA, Protocol::OSTATUS];
 560                                         $condition = ['nurl' => Strings::normaliseLink($actor), 'rel' => [Contact::SHARING, Contact::FRIEND],
 561                                                 'network' => $networks, 'archive' => false, 'pending' => false, 'uid' => $contact['uid']];
 562
 563                                         // Forum posts are only accepted from forum contacts
 564                                         if ($contact['contact-type'] == Contact::TYPE_COMMUNITY) {
 565                                                 $condition['rel'] = [Contact::SHARING, Contact::FRIEND, Contact::FOLLOWER];
 566                                         }
 567
 568                                         if (!DBA::exists('contact', $condition)) {
 569                                                 continue;
 570                                         }
 571                                 }
 572
 573                                 $receivers['uid:' . $contact['uid']] = $contact['uid'];
 574                         }
 575                 }
 576
 577                 self::switchContacts($receivers, $actor);
 578
 579                 return $receivers;
 580         }
 581
 582         /**
 583          * Fetch the receiver list of a given actor
 584          *
 585          * @param string $actor
 586          * @param array  $tags
 587          *
 588          * @return array with receivers (user id)
 589          * @throws \Exception
 590          */
 591         public static function getReceiverForActor($actor, $tags)
 592         {
 593                 $receivers = [];
 594                 $networks = [Protocol::ACTIVITYPUB, Protocol::DFRN, Protocol::DIASPORA, Protocol::OSTATUS];
 595                 $condition = ['nurl' => Strings::normaliseLink($actor), 'rel' => [Contact::SHARING, Contact::FRIEND, Contact::FOLLOWER],
 596                         'network' => $networks, 'archive' => false, 'pending' => false];
 597                 $contacts = DBA::select('contact', ['uid', 'rel'], $condition);
 598                 while ($contact = DBA::fetch($contacts)) {
 599                         if (self::isValidReceiverForActor($contact, $actor, $tags)) {
 600                                 $receivers['uid:' . $contact['uid']] = $contact['uid'];
 601                         }
 602                 }
 603                 DBA::close($contacts);
 604                 return $receivers;
 605         }
 606
 607         /**
 608          * Tests if the contact is a valid receiver for this actor
 609          *
 610          * @param array  $contact
 611          * @param string $actor
 612          * @param array  $tags
 613          *
 614          * @return bool with receivers (user id)
 615          * @throws \Exception
 616          */
 617         private static function isValidReceiverForActor($contact, $actor, $tags)
 618         {
 619                 // Public contacts are no valid receiver
 620                 if ($contact['uid'] == 0) {
 621                         return false;
 622                 }
 623
 624                 // Are we following the contact? Then this is a valid receiver
 625                 if (in_array($contact['rel'], [Contact::SHARING, Contact::FRIEND])) {
 626                         return true;
 627                 }
 628
 629                 // When the possible receiver isn't a community, then it is no valid receiver
 630                 $owner = User::getOwnerDataById($contact['uid']);
 631                 if (empty($owner) || ($owner['contact-type'] != Contact::TYPE_COMMUNITY)) {
 632                         return false;
 633                 }
 634
 635                 // Is the community account tagged?
 636                 foreach ($tags as $tag) {
 637                         if ($tag['type'] != 'Mention') {
 638                                 continue;
 639                         }
 640
 641                         if ($tag['href'] == $owner['url']) {
 642                                 return true;
 643                         }
 644                 }
 645
 646                 return false;
 647         }
 648
 649         /**
 650          * Switches existing contacts to ActivityPub
 651          *
 652          * @param integer $cid Contact ID
 653          * @param integer $uid User ID
 654          * @param string  $url Profile URL
 655          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 656          * @throws \ImagickException
 657          */
 658         public static function switchContact($cid, $uid, $url)
 659         {
 660                 $profile = ActivityPub::probeProfile($url);
 661                 if (empty($profile)) {
 662                         return;
 663                 }
 664
 665                 Logger::log('Switch contact ' . $cid . ' (' . $profile['url'] . ') for user ' . $uid . ' to ActivityPub');
 666
 667                 $photo = defaults($profile, 'photo', null);
 668                 unset($profile['photo']);
 669                 unset($profile['baseurl']);
 670                 unset($profile['guid']);
 671
 672                 $profile['nurl'] = Strings::normaliseLink($profile['url']);
 673                 DBA::update('contact', $profile, ['id' => $cid]);
 674
 675                 Contact::updateAvatar($photo, $uid, $cid);
 676
 677                 // Send a new follow request to be sure that the connection still exists
 678                 if (($uid != 0) && DBA::exists('contact', ['id' => $cid, 'rel' => [Contact::SHARING, Contact::FRIEND]])) {
 679                         ActivityPub\Transmitter::sendActivity('Follow', $profile['url'], $uid);
 680                         Logger::log('Send a new follow request to ' . $profile['url'] . ' for user ' . $uid, Logger::DEBUG);
 681                 }
 682         }
 683
 684         /**
 685          *
 686          *
 687          * @param $receivers
 688          * @param $actor
 689          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 690          * @throws \ImagickException
 691          */
 692         private static function switchContacts($receivers, $actor)
 693         {
 694                 if (empty($actor)) {
 695                         return;
 696                 }
 697
 698                 foreach ($receivers as $receiver) {
 699                         $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver, 'network' => Protocol::OSTATUS, 'nurl' => Strings::normaliseLink($actor)]);
 700                         if (DBA::isResult($contact)) {
 701                                 self::switchContact($contact['id'], $receiver, $actor);
 702                         }
 703
 704                         $contact = DBA::selectFirst('contact', ['id'], ['uid' => $receiver, 'network' => Protocol::OSTATUS, 'alias' => [Strings::normaliseLink($actor), $actor]]);
 705                         if (DBA::isResult($contact)) {
 706                                 self::switchContact($contact['id'], $receiver, $actor);
 707                         }
 708                 }
 709         }
 710
 711         /**
 712          *
 713          *
 714          * @param       $object_data
 715          * @param array $activity
 716          *
 717          * @return mixed
 718          */
 719         private static function addActivityFields($object_data, $activity)
 720         {
 721                 if (!empty($activity['published']) && empty($object_data['published'])) {
 722                         $object_data['published'] = JsonLD::fetchElement($activity, 'as:published', '@value');
 723                 }
 724
 725                 if (!empty($activity['diaspora:guid']) && empty($object_data['diaspora:guid'])) {
 726                         $object_data['diaspora:guid'] = JsonLD::fetchElement($activity, 'diaspora:guid', '@value');
 727                 }
 728
 729                 $object_data['service'] = JsonLD::fetchElement($activity, 'as:instrument', 'as:name', '@type', 'as:Service');
 730                 $object_data['service'] = JsonLD::fetchElement($object_data, 'service', '@value');
 731
 732                 return $object_data;
 733         }
 734
 735         /**
 736          * Fetches the object data from external ressources if needed
 737          *
 738          * @param string  $object_id    Object ID of the the provided object
 739          * @param array   $object       The provided object array
 740          * @param boolean $trust_source Do we trust the provided object?
 741          * @param integer $uid          User ID for the signature that we use to fetch data
 742          *
 743          * @return array|false with trusted and valid object data
 744          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 745          * @throws \ImagickException
 746          */
 747         private static function fetchObject(string $object_id, array $object = [], bool $trust_source = false, int $uid = 0)
 748         {
 749                 // By fetching the type we check if the object is complete.
 750                 $type = JsonLD::fetchElement($object, '@type');
 751
 752                 if (!$trust_source || empty($type)) {
 753                         $data = ActivityPub::fetchContent($object_id, $uid);
 754                         if (!empty($data)) {
 755                                 $object = JsonLD::compact($data);
 756                                 Logger::log('Fetched content for ' . $object_id, Logger::DEBUG);
 757                         } else {
 758                                 Logger::log('Empty content for ' . $object_id . ', check if content is available locally.', Logger::DEBUG);
 759
 760                                 $item = Item::selectFirst([], ['uri' => $object_id]);
 761                                 if (!DBA::isResult($item)) {
 762                                         Logger::log('Object with url ' . $object_id . ' was not found locally.', Logger::DEBUG);
 763                                         return false;
 764                                 }
 765                                 Logger::log('Using already stored item for url ' . $object_id, Logger::DEBUG);
 766                                 $data = ActivityPub\Transmitter::createNote($item);
 767                                 $object = JsonLD::compact($data);
 768                         }
 769                 } else {
 770                         Logger::log('Using original object for url ' . $object_id, Logger::DEBUG);
 771                 }
 772
 773                 $type = JsonLD::fetchElement($object, '@type');
 774
 775                 if (empty($type)) {
 776                         Logger::log('Empty type', Logger::DEBUG);
 777                         return false;
 778                 }
 779
 780                 if (in_array($type, self::CONTENT_TYPES)) {
 781                         return self::processObject($object);
 782                 }
 783
 784                 if ($type == 'as:Announce') {
 785                         $object_id = JsonLD::fetchElement($object, 'object', '@id');
 786                         if (empty($object_id) || !is_string($object_id)) {
 787                                 return false;
 788                         }
 789                         return self::fetchObject($object_id, [], false, $uid);
 790                 }
 791
 792                 Logger::log('Unhandled object type: ' . $type, Logger::DEBUG);
 793                 return false;
 794         }
 795
 796         /**
 797          * Convert tags from JSON-LD format into a simplified format
 798          *
 799          * @param array $tags Tags in JSON-LD format
 800          *
 801          * @return array with tags in a simplified format
 802          */
 803         private static function processTags($tags)
 804         {
 805                 $taglist = [];
 806
 807                 if (empty($tags)) {
 808                         return [];
 809                 }
 810
 811                 foreach ($tags as $tag) {
 812                         if (empty($tag)) {
 813                                 continue;
 814                         }
 815
 816                         $element = ['type' => str_replace('as:', '', JsonLD::fetchElement($tag, '@type')),
 817                                 'href' => JsonLD::fetchElement($tag, 'as:href', '@id'),
 818                                 'name' => JsonLD::fetchElement($tag, 'as:name', '@value')];
 819
 820                         if (empty($element['type'])) {
 821                                 continue;
 822                         }
 823
 824                         $taglist[] = $element;
 825                 }
 826                 return $taglist;
 827         }
 828
 829         /**
 830          * Convert emojis from JSON-LD format into a simplified format
 831          *
 832          * @param $emojis
 833          * @return array with emojis in a simplified format
 834          */
 835         private static function processEmojis($emojis)
 836         {
 837                 $emojilist = [];
 838
 839                 if (empty($emojis)) {
 840                         return [];
 841                 }
 842
 843                 foreach ($emojis as $emoji) {
 844                         if (empty($emoji) || (JsonLD::fetchElement($emoji, '@type') != 'toot:Emoji') || empty($emoji['as:icon'])) {
 845                                 continue;
 846                         }
 847
 848                         $url = JsonLD::fetchElement($emoji['as:icon'], 'as:url', '@id');
 849                         $element = ['name' => JsonLD::fetchElement($emoji, 'as:name', '@value'),
 850                                 'href' => $url];
 851
 852                         $emojilist[] = $element;
 853                 }
 854                 return $emojilist;
 855         }
 856
 857         /**
 858          * Convert attachments from JSON-LD format into a simplified format
 859          *
 860          * @param array $attachments Attachments in JSON-LD format
 861          *
 862          * @return array with attachmants in a simplified format
 863          */
 864         private static function processAttachments($attachments)
 865         {
 866                 $attachlist = [];
 867
 868                 if (empty($attachments)) {
 869                         return [];
 870                 }
 871
 872                 foreach ($attachments as $attachment) {
 873                         if (empty($attachment)) {
 874                                 continue;
 875                         }
 876
 877                         $attachlist[] = ['type' => str_replace('as:', '', JsonLD::fetchElement($attachment, '@type')),
 878                                 'mediaType' => JsonLD::fetchElement($attachment, 'as:mediaType', '@value'),
 879                                 'name' => JsonLD::fetchElement($attachment, 'as:name', '@value'),
 880                                 'url' => JsonLD::fetchElement($attachment, 'as:url', '@id')];
 881                 }
 882                 return $attachlist;
 883         }
 884
 885         /**
 886          * Fetches data from the object part of an activity
 887          *
 888          * @param array $object
 889          *
 890          * @return array
 891          * @throws \Exception
 892          */
 893         private static function processObject($object)
 894         {
 895                 if (!JsonLD::fetchElement($object, '@id')) {
 896                         return false;
 897                 }
 898
 899                 $object_data = [];
 900                 $object_data['object_type'] = JsonLD::fetchElement($object, '@type');
 901                 $object_data['id'] = JsonLD::fetchElement($object, '@id');
 902                 $object_data['reply-to-id'] = JsonLD::fetchElement($object, 'as:inReplyTo', '@id');
 903
 904                 // An empty "id" field is translated to "./" by the compactor, so we have to check for this content
 905                 if (empty($object_data['reply-to-id']) || ($object_data['reply-to-id'] == './')) {
 906                         $object_data['reply-to-id'] = $object_data['id'];
 907                 }
 908
 909                 $object_data['published'] = JsonLD::fetchElement($object, 'as:published', '@value');
 910                 $object_data['updated'] = JsonLD::fetchElement($object, 'as:updated', '@value');
 911
 912                 if (empty($object_data['updated'])) {
 913                         $object_data['updated'] = $object_data['published'];
 914                 }
 915
 916                 if (empty($object_data['published']) && !empty($object_data['updated'])) {
 917                         $object_data['published'] = $object_data['updated'];
 918                 }
 919
 920                 $actor = JsonLD::fetchElement($object, 'as:attributedTo', '@id');
 921                 if (empty($actor)) {
 922                         $actor = JsonLD::fetchElement($object, 'as:actor', '@id');
 923                 }
 924
 925                 $object_data['diaspora:guid'] = JsonLD::fetchElement($object, 'diaspora:guid', '@value');
 926                 $object_data['diaspora:comment'] = JsonLD::fetchElement($object, 'diaspora:comment', '@value');
 927                 $object_data['diaspora:like'] = JsonLD::fetchElement($object, 'diaspora:like', '@value');
 928                 $object_data['actor'] = $object_data['author'] = $actor;
 929                 $object_data['context'] = JsonLD::fetchElement($object, 'as:context', '@id');
 930                 $object_data['conversation'] = JsonLD::fetchElement($object, 'ostatus:conversation', '@id');
 931                 $object_data['sensitive'] = JsonLD::fetchElement($object, 'as:sensitive');
 932                 $object_data['name'] = JsonLD::fetchElement($object, 'as:name', '@value');
 933                 $object_data['summary'] = JsonLD::fetchElement($object, 'as:summary', '@value');
 934                 $object_data['content'] = JsonLD::fetchElement($object, 'as:content', '@value');
 935                 $object_data['source'] = JsonLD::fetchElement($object, 'as:source', 'as:content', 'as:mediaType', 'text/bbcode');
 936                 $object_data['source'] = JsonLD::fetchElement($object_data, 'source', '@value');
 937                 $object_data['start-time'] = JsonLD::fetchElement($object, 'as:startTime', '@value');
 938                 $object_data['end-time'] = JsonLD::fetchElement($object, 'as:endTime', '@value');
 939                 $object_data['location'] = JsonLD::fetchElement($object, 'as:location', 'as:name', '@type', 'as:Place');
 940                 $object_data['location'] = JsonLD::fetchElement($object_data, 'location', '@value');
 941                 $object_data['latitude'] = JsonLD::fetchElement($object, 'as:location', 'as:latitude', '@type', 'as:Place');
 942                 $object_data['latitude'] = JsonLD::fetchElement($object_data, 'latitude', '@value');
 943                 $object_data['longitude'] = JsonLD::fetchElement($object, 'as:location', 'as:longitude', '@type', 'as:Place');
 944                 $object_data['longitude'] = JsonLD::fetchElement($object_data, 'longitude', '@value');
 945                 $object_data['attachments'] = self::processAttachments(JsonLD::fetchElementArray($object, 'as:attachment'));
 946                 $object_data['tags'] = self::processTags(JsonLD::fetchElementArray($object, 'as:tag'));
 947                 $object_data['emojis'] = self::processEmojis(JsonLD::fetchElementArray($object, 'as:tag', 'toot:Emoji'));
 948                 $object_data['generator'] = JsonLD::fetchElement($object, 'as:generator', 'as:name', '@type', 'as:Application');
 949                 $object_data['generator'] = JsonLD::fetchElement($object_data, 'generator', '@value');
 950                 $object_data['alternate-url'] = JsonLD::fetchElement($object, 'as:url', '@id');
 951
 952                 // Special treatment for Hubzilla links
 953                 if (is_array($object_data['alternate-url'])) {
 954                         $object_data['alternate-url'] = JsonLD::fetchElement($object_data['alternate-url'], 'as:href', '@id');
 955
 956                         if (!is_string($object_data['alternate-url'])) {
 957                                 $object_data['alternate-url'] = JsonLD::fetchElement($object['as:url'], 'as:href', '@id');
 958                         }
 959                 }
 960
 961                 $object_data['receiver'] = self::getReceivers($object, $object_data['actor'], $object_data['tags']);
 962
 963                 // Common object data:
 964
 965                 // Unhandled
 966                 // @context, type, actor, signature, mediaType, duration, replies, icon
 967
 968                 // Also missing: (Defined in the standard, but currently unused)
 969                 // audience, preview, endTime, startTime, image
 970
 971                 // Data in Notes:
 972
 973                 // Unhandled
 974                 // contentMap, announcement_count, announcements, context_id, likes, like_count
 975                 // inReplyToStatusId, shares, quoteUrl, statusnetConversationId
 976
 977                 // Data in video:
 978
 979                 // To-Do?
 980                 // category, licence, language, commentsEnabled
 981
 982                 // Unhandled
 983                 // views, waitTranscoding, state, support, subtitleLanguage
 984                 // likes, dislikes, shares, comments
 985
 986                 return $object_data;
 987         }
 988 }