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Minimal PHP parser for HTTPS DNS Resource Record (type 65)
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| <?php | |
| /* | |
| Minimal HTTPS RR (DNS type 65) parser for PHP. | |
| Demonstrates how to parse HTTPS/SVCB records returned by: | |
| dns_get_record($host, 65, ..., true) | |
| Extracts ALPN values such as "h2" and "h3". | |
| Reference: | |
| RFC 9460 – Service Binding and Parameter Specification via the DNS (SVCB and HTTPS RRs) | |
| */ | |
| $records = dns_get_record('google.com', 65, $authns, $addtl, true); | |
| $data = $records[0]['data']; | |
| $rr = parseHttpsRR($data); | |
| $alpns = parseAlpn($rr['params'][1]); // key 1 = ALPN | |
| var_dump($rr); | |
| var_dump($alpns); | |
| function parseHttpsRR(string $data): array | |
| { | |
| $offset = 0; | |
| $len = strlen($data); | |
| // priority | |
| $priority = unpack('n', substr($data, $offset, 2))[1]; | |
| $offset += 2; | |
| // target name | |
| $labelLen = ord($data[$offset]); | |
| $offset++; | |
| if ($labelLen === 0) { | |
| $target = '.'; | |
| } else { | |
| $target = substr($data, $offset, $labelLen); | |
| $offset += $labelLen; | |
| } | |
| $params = []; | |
| while ($offset < $len) { | |
| $key = unpack('n', substr($data, $offset, 2))[1]; | |
| $offset += 2; | |
| $paramLen = unpack('n', substr($data, $offset, 2))[1]; | |
| $offset += 2; | |
| $value = substr($data, $offset, $paramLen); | |
| $offset += $paramLen; | |
| $params[$key] = $value; | |
| } | |
| return [ | |
| 'priority' => $priority, | |
| 'target' => $target, | |
| 'params' => $params | |
| ]; | |
| } | |
| function parseAlpn(string $value): array | |
| { | |
| $offset = 0; | |
| $alpns = []; | |
| while ($offset < strlen($value)) { | |
| $l = ord($value[$offset]); | |
| $offset++; | |
| $alpns[] = substr($value, $offset, $l); | |
| $offset += $l; | |
| } | |
| return $alpns; | |
| } |
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