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<?php |
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/* |
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* This file is part of PHP DNS Server. |
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* |
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* (c) Yif Swery <[email protected]> |
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* |
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* For the full copyright and license information, please view the LICENSE |
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* file that was distributed with this source code. |
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*/ |
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namespace yswery\DNS; |
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class Decoder |
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{ |
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/** |
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* @param string $message |
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* |
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* @return Message |
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*/ |
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public static function decodeMessage(string $message): Message |
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{ |
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$offset = 0; |
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$header = self::decodeHeader($message, $offset); |
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$messageObject = new Message($header); |
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$messageObject->setQuestions(self::decodeResourceRecords($message, $header->getQuestionCount(), $offset, true)); |
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$messageObject->setAnswers(self::decodeResourceRecords($message, $header->getAnswerCount(), $offset)); |
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$messageObject->setAuthoritatives(self::decodeResourceRecords($message, $header->getNameServerCount(), $offset)); |
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$messageObject->setAdditionals(self::decodeResourceRecords($message, $header->getAdditionalRecordsCount(), $offset)); |
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return $messageObject; |
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} |
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/** |
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* @param string $string |
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* @param int $offset |
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* |
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* @return string |
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*/ |
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public static function decodeDomainName(string $string, int &$offset = 0): string |
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{ |
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$len = ord($string[$offset]); |
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++$offset; |
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if (0 === $len) { |
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return '.'; |
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} |
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$domainName = ''; |
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while (0 !== $len) { |
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$domainName .= substr($string, $offset, $len).'.'; |
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$offset += $len; |
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$len = ord($string[$offset]); |
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++$offset; |
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} |
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return $domainName; |
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} |
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/** |
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* @param string $pkt |
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* @param int $offset |
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* @param int $count The number of resource records to decode |
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* @param bool $isQuestion Is the resource record from the question section |
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* |
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* @return ResourceRecord[] |
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*/ |
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public static function decodeResourceRecords(string $pkt, int $count = 1, int &$offset = 0, bool $isQuestion = false): array |
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{ |
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$resourceRecords = []; |
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for ($i = 0; $i < $count; ++$i) { |
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($rr = new ResourceRecord()) |
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->setQuestion($isQuestion) |
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->setName(self::decodeDomainName($pkt, $offset)); |
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if ($rr->isQuestion()) { |
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$values = unpack('ntype/nclass', substr($pkt, $offset, 4)); |
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$rr->setType($values['type'])->setClass($values['class']); |
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$offset += 4; |
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} else { |
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$values = unpack('ntype/nclass/Nttl/ndlength', substr($pkt, $offset, 10)); |
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$rr->setType($values['type'])->setClass($values['class'])->setTtl($values['ttl']); |
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$offset += 10; |
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//Ignore unsupported types. |
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try { |
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$rr->setRdata(self::decodeRdata($rr->getType(), substr($pkt, $offset, $values['dlength']))); |
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} catch (UnsupportedTypeException $e) { |
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$offset += $values['dlength']; |
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continue; |
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} |
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$offset += $values['dlength']; |
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} |
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$resourceRecords[] = $rr; |
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} |
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return $resourceRecords; |
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} |
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/** |
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* @param int $type |
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* @param string $rdata |
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* |
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* @return array|string|null |
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* |
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* @throws UnsupportedTypeException |
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*/ |
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public static function decodeRdata(int $type, string $rdata) |
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{ |
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switch ($type) { |
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case RecordTypeEnum::TYPE_A: |
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case RecordTypeEnum::TYPE_AAAA: |
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return inet_ntop($rdata); |
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case RecordTypeEnum::TYPE_NS: |
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case RecordTypeEnum::TYPE_CNAME: |
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case RecordTypeEnum::TYPE_PTR: |
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return self::decodeDomainName($rdata); |
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case RecordTypeEnum::TYPE_SOA: |
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$offset = 0; |
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return array_merge( |
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[ |
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'mname' => self::decodeDomainName($rdata, $offset), |
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'rname' => self::decodeDomainName($rdata, $offset), |
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], |
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unpack('Nserial/Nrefresh/Nretry/Nexpire/Nminimum', substr($rdata, $offset)) |
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); |
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case RecordTypeEnum::TYPE_MX: |
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return [ |
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'preference' => unpack('npreference', $rdata)['preference'], |
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'exchange' => self::decodeDomainName(substr($rdata, 2)), |
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]; |
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case RecordTypeEnum::TYPE_TXT: |
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$len = ord($rdata[0]); |
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if ((strlen($rdata) + 1) < $len) { |
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return null; |
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} |
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return substr($rdata, 1, $len); |
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case RecordTypeEnum::TYPE_SRV: |
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$offset = 6; |
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$values = unpack('npriority/nweight/nport', $rdata); |
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$values['target'] = self::decodeDomainName($rdata, $offset); |
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return $values; |
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case RecordTypeEnum::TYPE_AXFR: |
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case RecordTypeEnum::TYPE_ANY: |
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return null; |
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default: |
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throw new UnsupportedTypeException( |
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sprintf('Record type "%s" is not a supported type.', RecordTypeEnum::getName($type)) |
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); |
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} |
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} |
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/** |
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* @param string $pkt |
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* @param int $offset |
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* |
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* @return Header |
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*/ |
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public static function decodeHeader(string $pkt, int &$offset = 0): Header |
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{ |
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$data = unpack('nid/nflags/nqdcount/nancount/nnscount/narcount', $pkt); |
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$flags = self::decodeFlags($data['flags']); |
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$offset += 12; |
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return (new Header()) |
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->setId($data['id']) |
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->setResponse($flags['qr']) |
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->setOpcode($flags['opcode']) |
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->setAuthoritative($flags['aa']) |
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->setTruncated($flags['tc']) |
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->setRecursionDesired($flags['rd']) |
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->setRecursionAvailable($flags['ra']) |
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->setZ($flags['z']) |
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->setRcode($flags['rcode']) |
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->setQuestionCount($data['qdcount']) |
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->setAnswerCount($data['ancount']) |
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->setNameServerCount($data['nscount']) |
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->setAdditionalRecordsCount($data['arcount']); |
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} |
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/** |
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* @param string $flags |
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* |
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* @return array |
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*/ |
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private static function decodeFlags($flags): array |
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{ |
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return [ |
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'qr' => $flags >> 15 & 0x1, |
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'opcode' => $flags >> 11 & 0xf, |
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'aa' => $flags >> 10 & 0x1, |
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'tc' => $flags >> 9 & 0x1, |
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'rd' => $flags >> 8 & 0x1, |
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'ra' => $flags >> 7 & 0x1, |
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'z' => $flags >> 4 & 0x7, |
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'rcode' => $flags & 0xf, |
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]; |
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} |
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} |
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samuelwilliams /
PHP-DNS-SERVER
