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Fix: encoding decoding of CAA records #7

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Merged
lohanidamodar merged 5 commits into from
Jul 24, 2025
Merged

Fix: encoding decoding of CAA records #7

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f5fdf77
Fix missing CAA type
lohanidamodar Jul 23, 2025
671ad72
improve unpacking question
lohanidamodar Jul 23, 2025
4f3e011
update CAA encoding
lohanidamodar Jul 23, 2025
4639d0f
update for RFC compliant
lohanidamodar Jul 23, 2025
56173f0
fix codeql
lohanidamodar Jul 23, 2025
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2 changes: 2 additions & 0 deletions src/DNS/Record.php
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,7 @@ public function setType($type): self
'TXT' => 16,
'AAAA' => 28,
'SRV' => 33,
'CAA' => 257,
];
$upper = strtoupper($type);
$this->type = $map[$upper] ?? 0;
Expand Down Expand Up @@ -321,6 +322,7 @@ public function getTypeName(): string
16 => 'TXT',
28 => 'AAAA',
33 => 'SRV',
257 => 'CAA',
];
return $types[$this->type] ?? "TYPE{$this->type}";
}
Expand Down
73 changes: 51 additions & 22 deletions src/DNS/Server.php
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Original file line number Diff line number Diff line change
Expand Up @@ -173,35 +173,38 @@ public function start(): void
// Parse question domain
$domain = "";
$offset = 12;
while ($offset < \strlen($buffer)) {
// Get label length
$labelLength = \ord($buffer[$offset]);

while ($offset < strlen($buffer)) {
// Check for at least 1 byte for label length
if (($offset + 1) > strlen($buffer)) {
throw new \Exception('Malformed packet: not enough bytes for label length');
}
$labelLength = ord($buffer[$offset]);
Console::info("[PACKET] Processing label at offset {$offset}, length: {$labelLength}");

// End of question
if ($labelLength === 0 && \ord($buffer[$offset + 1]) === 0) {

@Meldiron Meldiron Jul 24, 2025

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From here, second part of statement ord(..) === 0 was removed, is this intentional?

@lohanidamodar lohanidamodar Jul 24, 2025

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yes because we now have new check above
if (($offset + 1) > strlen($buffer)) {

Console::info("[PACKET] End of domain name found at offset " . ($offset + 1));
// End of question (zero label)
if ($labelLength === 0) {
$offset += 1;
Console::info("[PACKET] End of domain name found at offset " . ($offset));
break;
}

// Extract label as string
$label = \substr($buffer, $offset + 1, $labelLength);
// Check for enough bytes for label
if (($offset + 1 + $labelLength) > strlen($buffer)) {
throw new \Exception('Malformed packet: not enough bytes for label');
}
$label = substr($buffer, $offset + 1, $labelLength);
Console::info("[PACKET] Found label: {$label}");

if (empty($domain)) {
$domain .= $label;
} else {
$domain .= '.' . $label;
}

// Skip to next label length
$offset += 1 + $labelLength;
}

// Parse question type
$unpacked = \unpack('ntype/nclass', \substr($buffer, $offset, 4));
// After domain, there should be 4 bytes for type/class
if (($offset + 4) > strlen($buffer)) {
throw new \Exception('Malformed packet: not enough bytes for question type/class');
}
$unpacked = unpack('ntype/nclass', substr($buffer, $offset, 4));
$offset += 4;
$typeByte = $unpacked['type'] ?? 0;
$classByte = $unpacked['class'] ?? 0;
Expand Down Expand Up @@ -270,23 +273,20 @@ public function start(): void

// Add answers section
foreach ($answers as $answer) {
$response .= \chr(192) . \chr(12); // 192 indicates this is pointer, 12 is offset to question.

$response .= chr(192) . chr(12); // 192 indicates this is pointer, 12 is offset to question.
// Pack the answer's type, not the question type
$response .= \pack('nn', $answer->getType(), $classByte);

$response .= pack('nn', $answer->getType(), $classByte);
/**
* @var string $type
*/
$type = $answer->getTypeName();

$response .= match ($type) {
'A' => $this->encodeIP($answer->getRdata(), $answer->getTTL()),
'AAAA' => $this->encodeIPv6($answer->getRdata(), $answer->getTTL()),
'CNAME' => $this->encodeDomain($answer->getRdata(), $answer->getTTL()),
'NS' => $this->encodeDomain($answer->getRdata(), $answer->getTTL()),
'TXT' => $this->encodeText($answer->getRdata(), $answer->getTTL()),
'CAA' => $this->encodeText($answer->getRdata(), $answer->getTTL()),
'CAA' => $this->encodeCAA($answer->getRdata(), $answer->getTTL()),
'MX' => $this->encodeMx($answer->getRdata(), $answer->getTTL(), $answer->getPriority() ?? 0),
'SRV' => $this->encodeSrv($answer->getRdata(), $answer->getTTL(), $answer->getPriority() ?? 0, $answer->getWeight() ?? 0, $answer->getPort() ?? 0),
default => ''
Expand Down Expand Up @@ -427,6 +427,35 @@ protected function encodeSrv(string $domain, int $ttl, int $priority, int $weigh
return $result;
}

protected function encodeCAA(array|string $rdata, int $ttl): string
{
// Accept either array or string for rdata
// If string, parse as 'tag value' (e.g. 'issue "letsencrypt.org"')
$flags = 0;
$tag = '';
$value = '';
if (is_array($rdata)) {
$flags = isset($rdata['flags']) ? (int)$rdata['flags'] : 0;
$tag = (string)($rdata['tag'] ?? 'issue');
$value = (string)($rdata['value'] ?? '');
} elseif (is_string($rdata)) {
// Try to parse: 'issue "letsencrypt.org"' or 'issuewild "example.com"'
if (preg_match('/^(issue|issuewild|iodef)\s+"([^"]+)"$/', $rdata, $m)) {
$tag = $m[1];
$value = $m[2];
} else {
// fallback: treat all as value
$tag = 'issue';
$value = $rdata;
}
}
$tagLen = strlen($tag);
$valueLen = strlen($value);
$rdataBin = chr($flags) . chr($tagLen) . $tag . $value;
$totalLen = 2 + $tagLen + $valueLen;
return pack('Nn', $ttl, $totalLen) . $rdataBin;
}
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/**
* Categorize error messages into standardized error types
* to prevent high cardinality in telemetry metrics
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