src/Util/HTTPSignature.php

   1 <?php
   2 /**
   3  * @copyright Copyright (C) 2010-2023, the Friendica project
   4  *
   5  * @license GNU AGPL version 3 or any later version
   6  *
   7  * This program is free software: you can redistribute it and/or modify
   8  * it under the terms of the GNU Affero General Public License as
   9  * published by the Free Software Foundation, either version 3 of the
  10  * License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU Affero General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Affero General Public License
  18  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  19  *
  20  */
  21
  22 namespace Friendica\Util;
  23
  24 use Friendica\Core\Logger;
  25 use Friendica\Database\Database;
  26 use Friendica\Database\DBA;
  27 use Friendica\DI;
  28 use Friendica\Model\APContact;
  29 use Friendica\Model\Contact;
  30 use Friendica\Model\ItemURI;
  31 use Friendica\Model\User;
  32 use Friendica\Network\HTTPClient\Capability\ICanHandleHttpResponses;
  33 use Friendica\Network\HTTPClient\Client\HttpClientAccept;
  34 use Friendica\Network\HTTPClient\Client\HttpClientOptions;
  35
  36 /**
  37  * Implements HTTP Signatures per draft-cavage-http-signatures-07.
  38  *
  39  * Ported from Hubzilla: https://framagit.org/hubzilla/core/blob/master/Zotlabs/Web/HTTPSig.php
  40  *
  41  * Other parts of the code for HTTP signing are taken from the Osada project.
  42  * https://framagit.org/macgirvin/osada
  43  *
  44  * @see https://tools.ietf.org/html/draft-cavage-http-signatures-07
  45  */
  46
  47 class HTTPSignature
  48 {
  49         // See draft-cavage-http-signatures-08
  50         /**
  51          * Verifies a magic request
  52          *
  53          * @param $key
  54          *
  55          * @return array with verification data
  56          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
  57          */
  58         public static function verifyMagic(string $key): array
  59         {
  60                 $headers   = null;
  61                 $spoofable = false;
  62                 $result = [
  63                         'signer'         => '',
  64                         'header_signed'  => false,
  65                         'header_valid'   => false
  66                 ];
  67
  68                 // Decide if $data arrived via controller submission or curl.
  69                 $headers = [];
  70                 $headers['(request-target)'] = strtolower(DI::args()->getMethod()).' '.$_SERVER['REQUEST_URI'];
  71
  72                 foreach ($_SERVER as $k => $v) {
  73                         if (strpos($k, 'HTTP_') === 0) {
  74                                 $field = str_replace('_', '-', strtolower(substr($k, 5)));
  75                                 $headers[$field] = $v;
  76                         }
  77                 }
  78
  79                 $sig_block = null;
  80
  81                 $sig_block = self::parseSigheader($headers['authorization']);
  82
  83                 if (!$sig_block) {
  84                         Logger::notice('no signature provided.');
  85                         return $result;
  86                 }
  87
  88                 $result['header_signed'] = true;
  89
  90                 $signed_headers = $sig_block['headers'];
  91                 if (!$signed_headers) {
  92                         $signed_headers = ['date'];
  93                 }
  94
  95                 $signed_data = '';
  96                 foreach ($signed_headers as $h) {
  97                         if (array_key_exists($h, $headers)) {
  98                                 $signed_data .= $h . ': ' . $headers[$h] . "\n";
  99                         }
 100                         if (strpos($h, '.')) {
 101                                 $spoofable = true;
 102                         }
 103                 }
 104
 105                 $signed_data = rtrim($signed_data, "\n");
 106
 107                 $algorithm = 'sha512';
 108
 109                 if ($key && function_exists($key)) {
 110                         $result['signer'] = $sig_block['keyId'];
 111                         $key = $key($sig_block['keyId']);
 112                 }
 113
 114                 Logger::info('Got keyID ' . $sig_block['keyId']);
 115
 116                 if (!$key) {
 117                         return $result;
 118                 }
 119
 120                 $x = Crypto::rsaVerify($signed_data, $sig_block['signature'], $key, $algorithm);
 121
 122                 Logger::info('verified: ' . $x);
 123
 124                 if (!$x) {
 125                         return $result;
 126                 }
 127
 128                 if (!$spoofable) {
 129                         $result['header_valid'] = true;
 130                 }
 131
 132                 return $result;
 133         }
 134
 135         /**
 136          * @param array   $head
 137          * @param string  $prvkey
 138          * @param string  $keyid (optional, default 'Key')
 139          *
 140          * @return array
 141          */
 142         public static function createSig(array $head, string $prvkey, string $keyid = 'Key'): array
 143         {
 144                 $return_headers = [];
 145                 if (!empty($head)) {
 146                         $return_headers = $head;
 147                 }
 148
 149                 $alg = 'sha512';
 150                 $algorithm = 'rsa-sha512';
 151
 152                 $x = self::sign($head, $prvkey, $alg);
 153
 154                 $headerval = 'keyId="' . $keyid . '",algorithm="' . $algorithm
 155                         . '",headers="' . $x['headers'] . '",signature="' . $x['signature'] . '"';
 156
 157                 $return_headers['Authorization'] = ['Signature ' . $headerval];
 158
 159                 return $return_headers;
 160         }
 161
 162         /**
 163          * @param array  $head
 164          * @param string $prvkey
 165          * @param string $alg (optional) default 'sha256'
 166          *
 167          * @return array
 168          */
 169         private static function sign(array $head, string $prvkey, string $alg = 'sha256'): array
 170         {
 171                 $ret = [];
 172                 $headers = '';
 173                 $fields  = '';
 174
 175                 foreach ($head as $k => $v) {
 176                         if (is_array($v)) {
 177                                 $v = implode(', ', $v);
 178                         }
 179                         $headers .= strtolower($k) . ': ' . trim($v) . "\n";
 180                         if ($fields) {
 181                                 $fields .= ' ';
 182                         }
 183                         $fields .= strtolower($k);
 184                 }
 185                 // strip the trailing linefeed
 186                 $headers = rtrim($headers, "\n");
 187
 188                 $sig = base64_encode(Crypto::rsaSign($headers, $prvkey, $alg));
 189
 190                 $ret['headers']   = $fields;
 191                 $ret['signature'] = $sig;
 192
 193                 return $ret;
 194         }
 195
 196         /**
 197          * @param string $header
 198          * @return array associative array with
 199          *   - \e string \b keyID
 200          *   - \e string \b created
 201          *   - \e string \b expires
 202          *   - \e string \b algorithm
 203          *   - \e array  \b headers
 204          *   - \e string \b signature
 205          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 206          */
 207         public static function parseSigheader(string $header): array
 208         {
 209                 // Remove obsolete folds
 210                 $header = preg_replace('/\n\s+/', ' ', $header);
 211
 212                 $token = "[!#$%&'*+.^_`|~0-9A-Za-z-]";
 213
 214                 $quotedString = '"(?:\\\\.|[^"\\\\])*"';
 215
 216                 $regex = "/($token+)=($quotedString|$token+)/ism";
 217
 218                 $matches = [];
 219                 preg_match_all($regex, $header, $matches, PREG_SET_ORDER);
 220
 221                 $headers = [];
 222                 foreach ($matches as $match) {
 223                         $headers[$match[1]] = trim($match[2] ?: $match[3], '"');
 224                 }
 225
 226                 // if the header is encrypted, decrypt with (default) site private key and continue
 227                 if (!empty($headers['iv'])) {
 228                         $header = self::decryptSigheader($headers, DI::config()->get('system', 'prvkey'));
 229                         return self::parseSigheader($header);
 230                 }
 231
 232                 $return = [
 233                         'keyId'     => $headers['keyId'] ?? '',
 234                         'algorithm' => $headers['algorithm'] ?? 'rsa-sha256',
 235                         'created'   => $headers['created'] ?? null,
 236                         'expires'   => $headers['expires'] ?? null,
 237                         'headers'   => explode(' ', $headers['headers'] ?? ''),
 238                         'signature' => base64_decode(preg_replace('/\s+/', '', $headers['signature'] ?? '')),
 239                 ];
 240
 241                 if (!empty($return['signature']) && !empty($return['algorithm']) && empty($return['headers'])) {
 242                         $return['headers'] = ['date'];
 243                 }
 244
 245                 return $return;
 246         }
 247
 248         /**
 249          * @param array  $headers Signature headers
 250          * @param string $prvkey  The site private key
 251          * @return string Decrypted signature string
 252          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 253          */
 254         private static function decryptSigheader(array $headers, string $prvkey): string
 255         {
 256                 if (!empty($headers['iv']) && !empty($headers['key']) && !empty($headers['data'])) {
 257                         return Crypto::unencapsulate($headers, $prvkey);
 258                 }
 259
 260                 return '';
 261         }
 262
 263         /*
 264          * Functions for ActivityPub
 265          */
 266
 267         /**
 268          * Post given data to a target for a user, returns the result class
 269          *
 270          * @param array  $data   Data that is about to be sent
 271          * @param string $target The URL of the inbox
 272          * @param array  $owner  Sender owner-view record
 273          *
 274          * @return ICanHandleHttpResponses
 275          */
 276         public static function post(array $data, string $target, array $owner): ICanHandleHttpResponses
 277         {
 278                 $content = json_encode($data, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
 279
 280                 // Header data that is about to be signed.
 281                 $host = parse_url($target, PHP_URL_HOST);
 282                 $path = parse_url($target, PHP_URL_PATH);
 283                 $digest = 'SHA-256=' . base64_encode(hash('sha256', $content, true));
 284                 $content_length = strlen($content);
 285                 $date = DateTimeFormat::utcNow(DateTimeFormat::HTTP);
 286
 287                 $headers = [
 288                         'Date' => $date,
 289                         'Content-Length' => $content_length,
 290                         'Digest' => $digest,
 291                         'Host' => $host
 292                 ];
 293
 294                 $signed_data = "(request-target): post " . $path . "\ndate: ". $date . "\ncontent-length: " . $content_length . "\ndigest: " . $digest . "\nhost: " . $host;
 295
 296                 $signature = base64_encode(Crypto::rsaSign($signed_data, $owner['uprvkey'], 'sha256'));
 297
 298                 $headers['Signature'] = 'keyId="' . $owner['url'] . '#main-key' . '",algorithm="rsa-sha256",headers="(request-target) date content-length digest host",signature="' . $signature . '"';
 299
 300                 $headers['Content-Type'] = 'application/activity+json';
 301
 302                 $postResult = DI::httpClient()->post($target, $content, $headers, DI::config()->get('system', 'curl_timeout'));
 303                 $return_code = $postResult->getReturnCode();
 304
 305                 Logger::info('Transmit to ' . $target . ' returned ' . $return_code);
 306
 307                 self::setInboxStatus($target, ($return_code >= 200) && ($return_code <= 299));
 308
 309                 return $postResult;
 310         }
 311
 312         /**
 313          * Transmit given data to a target for a user
 314          *
 315          * @param array  $data   Data that is about to be sent
 316          * @param string $target The URL of the inbox
 317          * @param array  $owner  Sender owner-vew record
 318          *
 319          * @return boolean Was the transmission successful?
 320          */
 321         public static function transmit(array $data, string $target, array $owner): bool
 322         {
 323                 $postResult = self::post($data, $target, $owner);
 324                 $return_code = $postResult->getReturnCode();
 325
 326                 return ($return_code >= 200) && ($return_code <= 299);
 327         }
 328
 329         /**
 330          * Set the delivery status for a given inbox
 331          *
 332          * @param string  $url     The URL of the inbox
 333          * @param boolean $success Transmission status
 334          * @param boolean $shared  The inbox is a shared inbox
 335          * @throws \Exception
 336          */
 337         static public function setInboxStatus(string $url, bool $success, bool $shared = false)
 338         {
 339                 $now = DateTimeFormat::utcNow();
 340
 341                 $status = DBA::selectFirst('inbox-status', [], ['url' => $url]);
 342                 if (!DBA::isResult($status)) {
 343                         $insertFields = ['url' => $url, 'uri-id' => ItemURI::getIdByURI($url), 'created' => $now, 'shared' => $shared];
 344                         if (!DBA::insert('inbox-status', $insertFields, Database::INSERT_IGNORE)) {
 345                                 Logger::warning('Unable to insert inbox-status row', $insertFields);
 346                                 return;
 347                         }
 348
 349                         $status = DBA::selectFirst('inbox-status', [], ['url' => $url]);
 350                 }
 351
 352                 if ($success) {
 353                         $fields = ['success' => $now];
 354                 } else {
 355                         $fields = ['failure' => $now];
 356                 }
 357
 358                 if ($status['failure'] > DBA::NULL_DATETIME) {
 359                         $new_previous_stamp = strtotime($status['failure']);
 360                         $old_previous_stamp = strtotime($status['previous']);
 361
 362                         // Only set "previous" with at least one day difference.
 363                         // We use this to assure to not accidentally archive too soon.
 364                         if (($new_previous_stamp - $old_previous_stamp) >= 86400) {
 365                                 $fields['previous'] = $status['failure'];
 366                         }
 367                 }
 368
 369                 if (!$success) {
 370                         if ($status['success'] <= DBA::NULL_DATETIME) {
 371                                 $stamp1 = strtotime($status['created']);
 372                         } else {
 373                                 $stamp1 = strtotime($status['success']);
 374                         }
 375
 376                         $stamp2 = strtotime($now);
 377                         $previous_stamp = strtotime($status['previous']);
 378
 379                         // Archive the inbox when there had been failures for five days.
 380                         // Additionally ensure that at least one previous attempt has to be in between.
 381                         if ((($stamp2 - $stamp1) >= 86400 * 5) && ($previous_stamp > $stamp1)) {
 382                                 $fields['archive'] = true;
 383                         }
 384                 } else {
 385                         $fields['archive'] = false;
 386                 }
 387
 388                 if (empty($status['uri-id'])) {
 389                         $fields['uri-id'] = ItemURI::getIdByURI($url);
 390                 }
 391
 392                 DBA::update('inbox-status', $fields, ['url' => $url]);
 393         }
 394
 395         /**
 396          * Fetches JSON data for a user
 397          *
 398          * @param string  $request request url
 399          * @param integer $uid     User id of the requester
 400          *
 401          * @return array JSON array
 402          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 403          */
 404         public static function fetch(string $request, int $uid): array
 405         {
 406                 $curlResult = self::fetchRaw($request, $uid);
 407
 408                 if (empty($curlResult)) {
 409                         return [];
 410                 }
 411
 412                 if (!$curlResult->isSuccess() || empty($curlResult->getBody())) {
 413                         return [];
 414                 }
 415
 416                 $content = json_decode($curlResult->getBody(), true);
 417                 if (empty($content) || !is_array($content)) {
 418                         return [];
 419                 }
 420
 421                 return $content;
 422         }
 423
 424         /**
 425          * Fetches raw data for a user
 426          *
 427          * @param string  $request request url
 428          * @param integer $uid     User id of the requester
 429          * @param boolean $binary  TRUE if asked to return binary results (file download) (default is "false")
 430          * @param array   $opts    (optional parameters) assoziative array with:
 431          *                         'accept_content' => supply Accept: header with 'accept_content' as the value
 432          *                         'timeout' => int Timeout in seconds, default system config value or 60 seconds
 433          *                         'nobody' => only return the header
 434          *                         'cookiejar' => path to cookie jar file
 435          *
 436          * @return \Friendica\Network\HTTPClient\Capability\ICanHandleHttpResponses CurlResult
 437          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 438          */
 439         public static function fetchRaw(string $request, int $uid = 0, array $opts = [HttpClientOptions::ACCEPT_CONTENT => [HttpClientAccept::JSON_AS]])
 440         {
 441                 $header = [];
 442
 443                 if (!empty($uid)) {
 444                         $owner = User::getOwnerDataById($uid);
 445                         if (!$owner) {
 446                                 return;
 447                         }
 448                 } else {
 449                         $owner = User::getSystemAccount();
 450                         if (!$owner) {
 451                                 return;
 452                         }
 453                 }
 454
 455                 if (!empty($owner['uprvkey'])) {
 456                         // Header data that is about to be signed.
 457                         $host = parse_url($request, PHP_URL_HOST);
 458                         $path = parse_url($request, PHP_URL_PATH);
 459                         $date = DateTimeFormat::utcNow(DateTimeFormat::HTTP);
 460
 461                         $header['Date'] = $date;
 462                         $header['Host'] = $host;
 463
 464                         $signed_data = "(request-target): get " . $path . "\ndate: ". $date . "\nhost: " . $host;
 465
 466                         $signature = base64_encode(Crypto::rsaSign($signed_data, $owner['uprvkey'], 'sha256'));
 467
 468                         $header['Signature'] = 'keyId="' . $owner['url'] . '#main-key' . '",algorithm="rsa-sha256",headers="(request-target) date host",signature="' . $signature . '"';
 469                 }
 470
 471                 $curl_opts                             = $opts;
 472                 $curl_opts[HttpClientOptions::HEADERS] = $header;
 473
 474                 if (!empty($opts['nobody'])) {
 475                         $curlResult = DI::httpClient()->head($request, $curl_opts);
 476                 } else {
 477                         $curlResult = DI::httpClient()->get($request, HttpClientAccept::JSON_AS, $curl_opts);
 478                 }
 479                 $return_code = $curlResult->getReturnCode();
 480
 481                 Logger::info('Fetched for user ' . $uid . ' from ' . $request . ' returned ' . $return_code);
 482
 483                 return $curlResult;
 484         }
 485
 486         /**
 487          * Fetch the apcontact entry of the keyId in the given header
 488          *
 489          * @param array $http_headers
 490          *
 491          * @return array APContact entry
 492          */
 493         public static function getKeyIdContact(array $http_headers): array
 494         {
 495                 if (empty($http_headers['HTTP_SIGNATURE'])) {
 496                         Logger::debug('No HTTP_SIGNATURE header', ['header' => $http_headers]);
 497                         return [];
 498                 }
 499
 500                 $sig_block = self::parseSigHeader($http_headers['HTTP_SIGNATURE']);
 501
 502                 if (empty($sig_block['keyId'])) {
 503                         Logger::debug('No keyId', ['sig_block' => $sig_block]);
 504                         return [];
 505                 }
 506
 507                 $url = (strpos($sig_block['keyId'], '#') ? substr($sig_block['keyId'], 0, strpos($sig_block['keyId'], '#')) : $sig_block['keyId']);
 508                 return APContact::getByURL($url);
 509         }
 510
 511         /**
 512          * Gets a signer from a given HTTP request
 513          *
 514          * @param string $content
 515          * @param array $http_headers
 516          *
 517          * @return string|null|false Signer
 518          * @throws \Friendica\Network\HTTPException\InternalServerErrorException
 519          */
 520         public static function getSigner(string $content, array $http_headers)
 521         {
 522                 if (empty($http_headers['HTTP_SIGNATURE'])) {
 523                         Logger::debug('No HTTP_SIGNATURE header');
 524                         return false;
 525                 }
 526
 527                 if (!empty($content)) {
 528                         $object = json_decode($content, true);
 529                         if (empty($object)) {
 530                                 Logger::info('No object');
 531                                 return false;
 532                         }
 533
 534                         $actor = JsonLD::fetchElement($object, 'actor', 'id') ?? '';
 535                 } else {
 536                         $actor = '';
 537                 }
 538
 539                 $headers = [];
 540                 $headers['(request-target)'] = strtolower(DI::args()->getMethod()) . ' ' . parse_url($http_headers['REQUEST_URI'], PHP_URL_PATH);
 541
 542                 // First take every header
 543                 foreach ($http_headers as $k => $v) {
 544                         $field = str_replace('_', '-', strtolower($k));
 545                         $headers[$field] = $v;
 546                 }
 547
 548                 // Now add every http header
 549                 foreach ($http_headers as $k => $v) {
 550                         if (strpos($k, 'HTTP_') === 0) {
 551                                 $field = str_replace('_', '-', strtolower(substr($k, 5)));
 552                                 $headers[$field] = $v;
 553                         }
 554                 }
 555
 556                 $sig_block = self::parseSigHeader($http_headers['HTTP_SIGNATURE']);
 557
 558                 // Add fields from the signature block to the header. See issue 8845
 559                 if (!empty($sig_block['created']) && empty($headers['(created)'])) {
 560                         $headers['(created)'] = $sig_block['created'];
 561                 }
 562
 563                 if (!empty($sig_block['expires']) && empty($headers['(expires)'])) {
 564                         $headers['(expires)'] = $sig_block['expires'];
 565                 }
 566
 567                 if (empty($sig_block) || empty($sig_block['headers']) || empty($sig_block['keyId'])) {
 568                         Logger::info('No headers or keyId');
 569                         return false;
 570                 }
 571
 572                 $signed_data = '';
 573                 foreach ($sig_block['headers'] as $h) {
 574                         if (array_key_exists($h, $headers)) {
 575                                 $signed_data .= $h . ': ' . $headers[$h] . "\n";
 576                         } else {
 577                                 Logger::info('Requested header field not found', ['field' => $h, 'header' => $headers]);
 578                         }
 579                 }
 580                 $signed_data = rtrim($signed_data, "\n");
 581
 582                 if (empty($signed_data)) {
 583                         Logger::info('Signed data is empty');
 584                         return false;
 585                 }
 586
 587                 $algorithm = null;
 588
 589                 // Wildcard value where signing algorithm should be derived from keyId
 590                 // @see https://tools.ietf.org/html/draft-ietf-httpbis-message-signatures-00#section-4.1
 591                 // Defaulting to SHA256 as it seems to be the prevalent implementation
 592                 // @see https://arewehs2019yet.vpzom.click
 593                 if ($sig_block['algorithm'] === 'hs2019') {
 594                         $algorithm = 'sha256';
 595                 }
 596
 597                 if ($sig_block['algorithm'] === 'rsa-sha256') {
 598                         $algorithm = 'sha256';
 599                 }
 600
 601                 if ($sig_block['algorithm'] === 'rsa-sha512') {
 602                         $algorithm = 'sha512';
 603                 }
 604
 605                 if (empty($algorithm)) {
 606                         Logger::info('No alagorithm');
 607                         return false;
 608                 }
 609
 610                 $key = self::fetchKey($sig_block['keyId'], $actor);
 611                 if (empty($key)) {
 612                         Logger::info('Empty key');
 613                         return false;
 614                 }
 615
 616                 if (!empty($key['url']) && !empty($key['type']) && ($key['type'] == 'Tombstone')) {
 617                         Logger::info('Actor is a tombstone', ['key' => $key]);
 618
 619                         if (!Contact::isLocal($key['url'])) {
 620                                 // We now delete everything that we possibly knew from this actor
 621                                 Contact::deleteContactByUrl($key['url']);
 622                         }
 623                         return null;
 624                 }
 625
 626                 if (empty($key['pubkey'])) {
 627                         Logger::info('Empty pubkey');
 628                         return false;
 629                 }
 630
 631                 if (!Crypto::rsaVerify($signed_data, $sig_block['signature'], $key['pubkey'], $algorithm)) {
 632                         Logger::info('Verification failed', ['signed_data' => $signed_data, 'algorithm' => $algorithm, 'header' => $sig_block['headers'], 'http_headers' => $http_headers]);
 633                         return false;
 634                 }
 635
 636                 $hasGoodSignedContent = false;
 637
 638                 // Check the digest when it is part of the signed data
 639                 if (!empty($content) && in_array('digest', $sig_block['headers'])) {
 640                         $digest = explode('=', $headers['digest'], 2);
 641                         if ($digest[0] === 'SHA-256') {
 642                                 $hashalg = 'sha256';
 643                         }
 644                         if ($digest[0] === 'SHA-512') {
 645                                 $hashalg = 'sha512';
 646                         }
 647
 648                         /// @todo add all hashes from the rfc
 649
 650                         if (!empty($hashalg) && base64_encode(hash($hashalg, $content, true)) != $digest[1]) {
 651                                 Logger::info('Digest does not match');
 652                                 return false;
 653                         }
 654
 655                         $hasGoodSignedContent = true;
 656                 }
 657
 658                 if (in_array('date', $sig_block['headers']) && !empty($headers['date'])) {
 659                         $created = strtotime($headers['date']);
 660                 } elseif (in_array('(created)', $sig_block['headers']) && !empty($sig_block['created'])) {
 661                         $created = $sig_block['created'];
 662                 } else {
 663                         $created = 0;
 664                 }
 665
 666                 if (in_array('(expires)', $sig_block['headers']) && !empty($sig_block['expires'])) {
 667                         $expired = min($sig_block['expires'], $created + 300);
 668                 } else {
 669                         $expired = $created + 300;
 670                 }
 671
 672                 //  Check if the signed date field is in an acceptable range
 673                 if (!empty($created)) {
 674                         $current = time();
 675
 676                         // Calculate with a grace period of 60 seconds to avoid slight time differences between the servers
 677                         if (($created - 60) > $current) {
 678                                 Logger::notice('Signature created in the future', ['created' => date(DateTimeFormat::MYSQL, $created), 'expired' => date(DateTimeFormat::MYSQL, $expired), 'current' => date(DateTimeFormat::MYSQL, $current)]);
 679                                 return false;
 680                         }
 681
 682                         if ($current > $expired) {
 683                                 Logger::notice('Signature expired', ['created' => date(DateTimeFormat::MYSQL, $created), 'expired' => date(DateTimeFormat::MYSQL, $expired), 'current' => date(DateTimeFormat::MYSQL, $current)]);
 684                                 return false;
 685                         }
 686
 687                         Logger::debug('Valid creation date', ['created' => date(DateTimeFormat::MYSQL, $created), 'expired' => date(DateTimeFormat::MYSQL, $expired), 'current' => date(DateTimeFormat::MYSQL, $current)]);
 688                         $hasGoodSignedContent = true;
 689                 }
 690
 691                 // Check the content-length when it is part of the signed data
 692                 if (in_array('content-length', $sig_block['headers'])) {
 693                         if (strlen($content) != $headers['content-length']) {
 694                                 Logger::info('Content length does not match');
 695                                 return false;
 696                         }
 697                 }
 698
 699                 // Ensure that the authentication had been done with some content
 700                 // Without this check someone could authenticate with fakeable data
 701                 if (!$hasGoodSignedContent) {
 702                         Logger::info('No good signed content');
 703                         return false;
 704                 }
 705
 706                 return $key['url'];
 707         }
 708
 709         /**
 710          * fetches a key for a given id and actor
 711          *
 712          * @param string $id
 713          * @param string $actor
 714          *
 715          * @return array with actor url and public key
 716          * @throws \Exception
 717          */
 718         private static function fetchKey(string $id, string $actor): array
 719         {
 720                 $url = (strpos($id, '#') ? substr($id, 0, strpos($id, '#')) : $id);
 721
 722                 $profile = APContact::getByURL($url);
 723                 if (!empty($profile)) {
 724                         Logger::info('Taking key from id', ['id' => $id]);
 725                         return ['url' => $url, 'pubkey' => $profile['pubkey'], 'type' => $profile['type']];
 726                 } elseif ($url != $actor) {
 727                         $profile = APContact::getByURL($actor);
 728                         if (!empty($profile)) {
 729                                 Logger::info('Taking key from actor', ['actor' => $actor]);
 730                                 return ['url' => $actor, 'pubkey' => $profile['pubkey'], 'type' => $profile['type']];
 731                         }
 732                 }
 733
 734                 Logger::notice('Key could not be fetched', ['url' => $url, 'actor' => $actor]);
 735                 return [];
 736         }
 737 }