- public static function verifySignature($content, $http_headers)
- {
- $object = json_decode($content, true);
-
- if (empty($object)) {
- return false;
- }
-
- $actor = self::processElement($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;
- }
- }
-
- $sig_block = ActivityPub::parseSigHeader($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, $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) != $headers['content-length']) {
- return false;
- }
- }
-
- return true;
-
- }
-
- private static function fetchKey($id, $actor)
- {
- $url = (strpos($id, '#') ? substr($id, 0, strpos($id, '#')) : $id);
-
- $profile = self::fetchprofile($url);
- if (!empty($profile)) {
- return $profile['pubkey'];
- } elseif ($url != $actor) {
- $profile = self::fetchprofile($actor);
- if (!empty($profile)) {
- return $profile['pubkey'];
- }
- }
-
- return false;
- }
-
- /**
- * @brief
- *
- * @param string $header
- * @return array associate array with
- * - \e string \b keyID
- * - \e string \b algorithm
- * - \e array \b headers
- * - \e string \b signature
- */
- private static function parseSigHeader($header)
- {
- $ret = [];
- $matches = [];
-
- if (preg_match('/keyId="(.*?)"/ism',$header,$matches)) {
- $ret['keyId'] = $matches[1];
- }
-
- if (preg_match('/algorithm="(.*?)"/ism',$header,$matches)) {
- $ret['algorithm'] = $matches[1];
- }
-
- if (preg_match('/headers="(.*?)"/ism',$header,$matches)) {
- $ret['headers'] = explode(' ', $matches[1]);
- }
-
- if (preg_match('/signature="(.*?)"/ism',$header,$matches)) {
- $ret['signature'] = base64_decode(preg_replace('/\s+/','',$matches[1]));
- }
-
- return $ret;
- }
-