Skip to content

Fix: improve encoder functions according to RFC #8

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
lohanidamodar merged 12 commits into from
Jul 28, 2025
Merged

Fix: improve encoder functions according to RFC #8

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
12 commits
Select commit Hold shift + click to select a range
a3101f2
Fix: improve encoder functions according to RFC
lohanidamodar Jul 27, 2025
be5f654
Fix zone tokenizer to handle quoted strings
lohanidamodar Jul 27, 2025
bb861d0
fix validation
lohanidamodar Jul 27, 2025
56bc8cc
add test
lohanidamodar Jul 27, 2025
fdf0efc
update client
lohanidamodar Jul 27, 2025
6656468
improve client
lohanidamodar Jul 27, 2025
614b63d
improve client
lohanidamodar Jul 27, 2025
957e01e
fix zone import/export
lohanidamodar Jul 27, 2025
23ff429
fix zone
lohanidamodar Jul 27, 2025
eddb5d8
fix reviews
lohanidamodar Jul 27, 2025
7650f28
improvements with validation and constants
lohanidamodar Jul 28, 2025
d806436
relevant RFC links
lohanidamodar Jul 28, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 3 additions & 2 deletions src/DNS/Client.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -226,10 +226,11 @@ private function parseRdata(string $packet, int &$offset, int $type, int $rdleng
while ($offset < $end) {
$len = ord($packet[$offset]);
$offset++;
$txts[] = substr($packet, $offset, $len);
$chunk = ($len > 0) ? substr($packet, $offset, $len) : '';
$txts[] = $chunk;
$offset += $len;
}
return implode(' ', $txts);
return implode('', $txts);
case 33: // SRV record
$priority = unpack('n', substr($packet, $offset, 2));
$weight = unpack('n', substr($packet, $offset + 2, 2));
Expand Down
192 changes: 140 additions & 52 deletions src/DNS/Server.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
use Utopia\Telemetry\Histogram;

/**
* Refference about DNS packet:
* Reference about DNS packet:
*
* HEADER
* > 16 bits identificationField (1-65535. 0 means no ID). ID provided by client. Helps to match async responses. Usage may allow DNS Cache Poisoning
Expand All @@ -29,7 +29,7 @@
* > 16 bits numberOfAdditionals (0-65535)
*
* QUESTIONS SECTION
* > Each question contians:
* > Each question contains:
* > -- dynamic-length name. Includes domain name we are looking for. Split into labels. To get domain, join labels with dot symbol.
* > -- -- Following pattern repeats:
* > -- -- -- 8 bits labelLength (0-255). Defines length of label. We use it in next step
Expand All @@ -42,16 +42,33 @@
* ANSWERS SECTION
* > Follows same pattern as questions section.
* > Each answer also has (at the end):
* > -- 32 bits ttl. Time to live of the naswer
* > -- 32 bits ttl. Time to live of the answer
* > -- 16 bit length. Length of the answer data.
* > -- X bits data X length is length from above. Gives answer itself. Structure changes based on type.
*
* AUTHORITIES SECTION
* ADDITIONALS SECTION
*
* RFCs:
* - RFC 1035: https://datatracker.ietf.org/doc/html/rfc1035
* - RFC 3596: https://datatracker.ietf.org/doc/html/rfc3596
* - RFC 6844: https://datatracker.ietf.org/doc/html/rfc6844
* - RFC 2782: https://datatracker.ietf.org/doc/html/rfc2782
*/

class Server
// DNS protocol constants
{
public const IPV4_LEN = 4;
public const IPV6_LEN = 16;
public const MAX_LABEL_LEN = 63;
public const MAX_LABELS = 127;
public const MAX_DOMAIN_NAME_LEN = 255; // RFC 1035: max length of domain name in wire format
public const MAX_PRIORITY = 65535;
public const MAX_WEIGHT = 65535;
public const MAX_PORT = 65535;
public const MAX_CAA_FLAGS = 255;
public const MAX_TXT_CHUNK = 255;
protected Adapter $adapter;
protected Resolver $resolver;
/** @var array<int, callable> */
Expand Down Expand Up @@ -330,105 +347,176 @@ protected function resolve(array $question): array
return $this->resolver->resolve($question);
}

/**
* Encode an IPv4 address (A record) according to RFC 1035.
* @see https://datatracker.ietf.org/doc/html/rfc1035
*
* @param string $ip
* @param int $ttl
* @return string
*/
protected function encodeIP(string $ip, int $ttl): string
{
$result = \pack('Nn', $ttl, 4);

$binaryIP = inet_pton($ip);
if ($binaryIP === false) {
if ($binaryIP === false || strlen($binaryIP) !== self::IPV4_LEN) {
throw new \Exception("Invalid IPv4 address format: {$ip}");
}

// Append the binary IPv4 address directly
$result .= $binaryIP;

$result = pack('Nn', $ttl, self::IPV4_LEN) . $binaryIP;
return $result;
}

/**
* Encode an IPv6 address (AAAA record) according to RFC 3596.
* @see https://datatracker.ietf.org/doc/html/rfc3596
*
* @param string $ip
* @param int $ttl
* @return string
*/
protected function encodeIPv6(string $ip, int $ttl): string
{
$result = \pack('Nn', $ttl, 16);

$binaryIP = inet_pton($ip);
if ($binaryIP === false) {
if ($binaryIP === false || strlen($binaryIP) !== self::IPV6_LEN) {
throw new \Exception("Invalid IPv6 address format: {$ip}");
}

$result .= $binaryIP;

$result = pack('Nn', $ttl, self::IPV6_LEN) . $binaryIP;
return $result;
}

/**
* Encode a domain name (CNAME, NS, PTR) according to RFC 1035.
* @see https://datatracker.ietf.org/doc/html/rfc1035
*
* @param string $domain
* @param int $ttl
* @return string
*/
protected function encodeDomain(string $domain, int $ttl): string
{
$labels = explode('.', rtrim($domain, '.'));
$result = '';
$totalLength = 0;

foreach (\explode('.', $domain) as $label) {
$labelLength = \strlen($label);
$result .= \chr($labelLength);
$result .= $label;
foreach ($labels as $label) {
$labelLength = strlen($label);
if ($labelLength === 0) {
throw new \Exception("Empty label in domain: '{$domain}'");
}
if ($labelLength > self::MAX_LABEL_LEN) {
throw new \Exception("Label too long in domain: {$label}");
}
$result .= chr($labelLength) . $label;
$totalLength += 1 + $labelLength;
}

$result .= \chr(0);
$result .= chr(0);
$totalLength += 1;

$result = \pack('Nn', $ttl, $totalLength) . $result;

if ($totalLength > self::MAX_DOMAIN_NAME_LEN) {
throw new \Exception("Encoded domain name too long: {$domain}");
}
$result = pack('Nn', $ttl, $totalLength) . $result;
return $result;
}

/**
* Encode a TXT record according to RFC 1035.
* @see https://datatracker.ietf.org/doc/html/rfc1035
*
* @param string $text
* @param int $ttl
* @return string
*/
protected function encodeText(string $text, int $ttl): string
{
$textLength = \strlen($text);
$result = \pack('Nn', $ttl, 1 + $textLength) . \chr($textLength) . $text;

$chunks = [];
$len = strlen($text);
for ($i = 0; $i < $len; $i += self::MAX_TXT_CHUNK) {
$chunk = substr($text, $i, self::MAX_TXT_CHUNK);
$chunks[] = chr(strlen($chunk)) . $chunk;
}
$txtData = implode('', $chunks);
$result = pack('Nn', $ttl, strlen($txtData)) . $txtData;
return $result;
}

/**
* Encode an MX record according to RFC 1035.
* @see https://datatracker.ietf.org/doc/html/rfc1035
*
* @param string $domain
* @param int $ttl
* @param int $priority
* @return string
*/
protected function encodeMx(string $domain, int $ttl, int $priority): string
{
$result = \pack('n', $priority);
$labels = explode('.', rtrim($domain, '.'));
$result = pack('n', $priority);
$totalLength = 2;

foreach (\explode('.', $domain) as $label) {
$labelLength = \strlen($label);
$result .= \chr($labelLength);
$result .= $label;
foreach ($labels as $label) {
$labelLength = strlen($label);
if ($labelLength > self::MAX_LABEL_LEN) {
throw new \Exception("Label too long in MX domain: {$label}");
}
$result .= chr($labelLength) . $label;
$totalLength += 1 + $labelLength;
}

$result .= \chr(0);
$result .= chr(0);
$totalLength += 1;

$result = \pack('Nn', $ttl, $totalLength) . $result;

if ($totalLength > self::MAX_DOMAIN_NAME_LEN) {
throw new \Exception("Encoded MX domain name too long: {$domain}");
}
$result = pack('Nn', $ttl, $totalLength) . $result;
return $result;
Comment thread
lohanidamodar marked this conversation as resolved.
}

/**
* Encode an SRV record according to RFC 2782.
* @see https://datatracker.ietf.org/doc/html/rfc2782
*
* @param string $domain
* @param int $ttl
* @param int $priority
* @param int $weight
* @param int $port
* @return string
*/
protected function encodeSrv(string $domain, int $ttl, int $priority, int $weight, int $port): string
{
$result = \pack('nnn', $priority, $weight, $port);
// Validate SRV parameters
if ($priority < 0 || $priority > self::MAX_PRIORITY) {
throw new \Exception("SRV priority out of range: {$priority}");
}
if ($weight < 0 || $weight > self::MAX_WEIGHT) {
throw new \Exception("SRV weight out of range: {$weight}");
}
if ($port < 0 || $port > self::MAX_PORT) {
throw new \Exception("SRV port out of range: {$port}");
}
$labels = explode('.', rtrim($domain, '.'));
$result = pack('nnn', $priority, $weight, $port);
$totalLength = 6;

foreach (\explode('.', $domain) as $label) {
$labelLength = \strlen($label);
$result .= \chr($labelLength);
$result .= $label;
foreach ($labels as $label) {
$labelLength = strlen($label);
if ($labelLength === 0) {
throw new \Exception("Empty label in SRV domain: '{$domain}'");
}
if ($labelLength > self::MAX_LABEL_LEN) {
throw new \Exception("Label too long in SRV domain: {$label}");
}
$result .= chr($labelLength) . $label;
$totalLength += 1 + $labelLength;
}

$result .= \chr(0);
$result .= chr(0);
$totalLength += 1;

$result = \pack('Nn', $ttl, $totalLength) . $result;

if ($totalLength > self::MAX_DOMAIN_NAME_LEN) {
throw new \Exception("Encoded SRV domain name too long: {$domain}");
}
$result = pack('Nn', $ttl, $totalLength) . $result;
return $result;
}

/**
* Encode a CAA record according to RFC 6844.
* @see https://datatracker.ietf.org/doc/html/rfc6844
*
* @param array{flags?:int,tag?:string,value?:string}|string $rdata
* @param int $ttl
Expand Down Expand Up @@ -460,7 +548,7 @@ protected function encodeCAA(array|string $rdata, int $ttl): string
}
}
// Validate flags (must be 0-255)
$flags = max(0, min(255, $flags));
$flags = max(0, min(self::MAX_CAA_FLAGS, $flags));
$tagLen = strlen($tag);
$valueLen = strlen($value);
$rdataBin = chr($flags) . chr($tagLen) . $tag . $value;
Expand Down
Loading