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