+
+ /*
+ * Functions for ActivityPub
+ */
+
+ /**
+ * @brief Transmit given data to a target for a user
+ *
+ * @param $data
+ * @param $target
+ * @param $uid
+ */
+ public static function transmit($data, $target, $uid)
+ {
+ $owner = User::getOwnerDataById($uid);
+
+ if (!$owner) {
+ return;
+ }
+
+ $content = json_encode($data, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
+
+ // Header data that is about to be signed.
+ $host = parse_url($target, PHP_URL_HOST);
+ $path = parse_url($target, PHP_URL_PATH);
+ $digest = 'SHA-256=' . base64_encode(hash('sha256', $content, true));
+ $content_length = strlen($content);
+
+ $headers = ['Content-Length: ' . $content_length, 'Digest: ' . $digest, 'Host: ' . $host];
+
+ $signed_data = "(request-target): post " . $path . "\ncontent-length: " . $content_length . "\ndigest: " . $digest . "\nhost: " . $host;
+
+ $signature = base64_encode(Crypto::rsaSign($signed_data, $owner['uprvkey'], 'sha256'));
+
+ $headers[] = 'Signature: keyId="' . $owner['url'] . '#main-key' . '",algorithm="rsa-sha256",headers="(request-target) content-length digest host",signature="' . $signature . '"';
+
+ $headers[] = 'Content-Type: application/activity+json';
+
+ Network::post($target, $content, $headers);
+ $return_code = BaseObject::getApp()->get_curl_code();
+
+ logger('Transmit to ' . $target . ' returned ' . $return_code);
+ }
+
+ /**
+ * @brief Gets a signer from a given HTTP request
+ *
+ * @param $content
+ * @param $http_headers
+ *
+ * @return signer string
+ */
+ public static function getSigner($content, $http_headers)
+ {
+ $object = json_decode($content, true);
+
+ if (empty($object)) {
+ return false;
+ }
+
+ $actor = JsonLD::fetchElement($object, 'actor', 'id');
+
+ $headers = [];
+ $headers['(request-target)'] = strtolower($http_headers['REQUEST_METHOD']) . ' ' . $http_headers['REQUEST_URI'];
+
+ // First take every header
+ foreach ($http_headers as $k => $v) {
+ $field = str_replace('_', '-', strtolower($k));
+ $headers[$field] = $v;
+ }
+
+ // Now add every http header
+ foreach ($http_headers as $k => $v) {
+ if (strpos($k, 'HTTP_') === 0) {
+ $field = str_replace('_', '-', strtolower(substr($k, 5)));
+ $headers[$field] = $v;
+ }
+ }
+
+ $sig_block = self::parseSigHeader($http_headers['HTTP_SIGNATURE']);
+
+ if (empty($sig_block) || empty($sig_block['headers']) || empty($sig_block['keyId'])) {
+ return false;
+ }
+
+ $signed_data = '';
+ foreach ($sig_block['headers'] as $h) {
+ if (array_key_exists($h, $headers)) {
+ $signed_data .= $h . ': ' . $headers[$h] . "\n";
+ }
+ }
+ $signed_data = rtrim($signed_data, "\n");
+
+ if (empty($signed_data)) {
+ return false;
+ }
+
+ $algorithm = null;
+
+ if ($sig_block['algorithm'] === 'rsa-sha256') {
+ $algorithm = 'sha256';
+ }
+
+ if ($sig_block['algorithm'] === 'rsa-sha512') {
+ $algorithm = 'sha512';
+ }
+
+ if (empty($algorithm)) {
+ return false;
+ }
+
+ $key = self::fetchKey($sig_block['keyId'], $actor);
+
+ if (empty($key)) {
+ return false;
+ }
+
+ if (!Crypto::rsaVerify($signed_data, $sig_block['signature'], $key['pubkey'], $algorithm)) {
+ return false;
+ }
+
+ // Check the digest when it is part of the signed data
+ if (in_array('digest', $sig_block['headers'])) {
+ $digest = explode('=', $headers['digest'], 2);
+ if ($digest[0] === 'SHA-256') {
+ $hashalg = 'sha256';
+ }
+ if ($digest[0] === 'SHA-512') {
+ $hashalg = 'sha512';
+ }
+
+ /// @todo add all hashes from the rfc
+
+ if (!empty($hashalg) && base64_encode(hash($hashalg, $content, true)) != $digest[1]) {
+ return false;
+ }
+ }
+
+ // Check the content-length when it is part of the signed data
+ if (in_array('content-length', $sig_block['headers'])) {
+ if (strlen($content) != $headers['content-length']) {
+ return false;
+ }
+ }
+
+ return $key['url'];
+ }
+
+ /**
+ * @brief fetches a key for a given id and actor
+ *
+ * @param $id
+ * @param $actor
+ *
+ * @return array with actor url and public key
+ */
+ private static function fetchKey($id, $actor)
+ {
+ $url = (strpos($id, '#') ? substr($id, 0, strpos($id, '#')) : $id);
+
+ $profile = APContact::getByURL($url);
+ if (!empty($profile)) {
+ logger('Taking key from id ' . $id, LOGGER_DEBUG);
+ return ['url' => $url, 'pubkey' => $profile['pubkey']];
+ } elseif ($url != $actor) {
+ $profile = APContact::getByURL($actor);
+ if (!empty($profile)) {
+ logger('Taking key from actor ' . $actor, LOGGER_DEBUG);
+ return ['url' => $actor, 'pubkey' => $profile['pubkey']];
+ }
+ }
+
+ return false;
+ }