<?php
namespace App\Classes\Protocol;
use App\Models\Address;
use App\Models\Domain;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Log;
use App\Http\Controllers\DomainController;
final class DNS
{
private const LOGKEY = 'PD-';
private string $rx_buf;
private array $header;
private array $remote;
private int $rx_ptr;
private \Socket $socket;
// DNS Response codes
public const DNS_NOERROR = 0; // No error
public const DNS_FORMERR = 1; // Format Error - The dns server could not read / understand the query
public const DNS_SERVFAIL = 2; // Server Failure - There was a dns error with the dns server
public const DNS_NAMEERR = 3; // Name Error - This specifies that the domain name in the query does not exist, it is only valid from an authoritative server
public const DNS_NOTIMPLEMENTED = 4;// Not implemented - The requested query is not supported by the dns server
public const DNS_REFUSED = 5; // Refused - The dns server refuses to process the dns query
// DNS Query Classes
public const DNS_QUERY_IN = 1; // Internet (this is the main one that is used)
// DNS Query Types
public const DNS_TYPE_A = 1; // A Records
public const DNS_TYPE_NS = 2; // NS Records
public const DNS_TYPE_CNAME = 5; // CNAME Records
public const DNS_TYPE_SOA = 6; // SOA Records
public const DNS_TYPE_MX = 15; // MX Records
public const DNS_TYPE_TXT = 16; // TXT Records
public const DNS_TYPE_AAAA = 28; // AAAA Records
// https://github.com/guyinatuxedo/dns-fuzzer/blob/master/dns.md
private const header = [ // Struct of a DNS query
'id' => [0x00,'n',1], // ID
'header' => [0x01,'n',1], // Header
'qdcount' => [0x02,'n',1], // Entries in the question
'ancount' => [0x03,'n',1], // Resource Records in the answer
'nscount' => [0x04,'n',1], // Server Resource Records in the answer
'arcount' => [0x05,'n',1], // Resource Records in the addition records section
];
/**
* Handle a DNS query
*
* https://www.ietf.org/rfc/rfc1035.txt
* https://github.com/guyinatuxedo/dns-fuzzer/blob/master/dns.md
*
* labels 63 octets or less
* names 255 octets or less
* TTL positive values of a signed 32 bit number.
* UDP messages 512 octets or less
*
* @param array $remote
* @param string $buf
* @param \Socket $socket
* @return void
*
dig +noedns -t CNAME mail.dcml.au @1.1.1.1
; <<>> DiG 9.10.6 <<>> +noedns -t CNAME mail.dcml.au @1.1.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6473
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;mail.dcml.au. IN CNAME
;; ANSWER SECTION:
mail.dcml.au. 300 IN CNAME l.dege.au.
;; Query time: 43 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Thu Apr 20 06:47:55 PST 2023
;; MSG SIZE rcvd: 51
06:47:54.995929 IP 192.168.130.184.51502 > one.one.one.one.domain: 6473+ CNAME? mail.dcml.au. (30)
0x0000: cc03 d9cc 88cb bcd0 7414 d055 0800 4500 ........t..U..E.
0x0010: 003a eee2 0000 4011 466e c0a8 82b8 0101 .:....@.Fn......
0x0020: 0101 c92e 0035 0026 bb5f|1949 0120 0001 .....5.&._.I....
0x0030: 0000 0000 0000 046d 6169 6c04 6463 6d6c .......mail.dcml
0x0040: 0261 7500 0005 0001 .au.....
06:47:55.034171 IP one.one.one.one.domain > 192.168.130.184.51502: 6473$ 1/0/0 CNAME l.dege.au. (51)
0x0000: bcd0 7414 d055 cc03 d9cc 88cb 0800 4588 ..t..U........E.
0x0010: 004f 514a 4000 3a11 a969 0101 0101 c0a8 .OQJ@.:..i......
0x0020: 82b8 0035 c92e 003b 9274|1949 81a0 0001 ...5...;.t.I....
0x0030: 0001 0000 0000 046d 6169 6c04 6463 6d6c .......mail.dcml
0x0040: 0261 7500 0005 0001 c00c 0005 0001 0000 .au.............
0x0050: 012c 0009 016c 0464 6567 65c0 16 .,...l.dege..
*/
public function onConnect(array $remote,string $buf,\Socket $socket)
{
Log::debug(sprintf('%s:+ DNS Query',self::LOGKEY));
$header_len = collect(self::header)->sum(function($item) { return $item[2]*2; });
$this->rx_buf = $buf;
$this->rx_ptr = 0;
// DNS Query header
$this->header = unpack(self::unpackheader(self::header),$buf);
$this->rx_ptr += $header_len;
$this->remote = $remote;
$this->socket = $socket;
// If there is no query count, then its an error
if ($this->header['qdcount'] !== 1) {
Log::error(sprintf('%s:! DNS query doesnt have the right number of queries [%d]',self::LOGKEY,$this->header['qdcount']));
$this->reply(self::DNS_FORMERR);
return;
}
// Get the query elements
$labels = collect();
while (($len=ord($this->read(1))) !== 0x00)
$labels->push($this->read($len));
$this->question = substr($this->rx_buf,$header_len,$this->rx_ptr-$header_len+4);
// We need a minimum of f.n.z.d.root
if ($labels->count() < 5) {
Log::error(sprintf('%s:! DNS query for a resource we dont manage [%s]',self::LOGKEY,$labels->join('.')));
$this->reply(self::DNS_NAMEERR);
return;
}
// First check that it is a query we can answer
// First label should be p.. or f..
if (! is_null($p=$this->parse('p',$labels->first())))
$labels->shift();
if (is_null($f=$this->parse('f',$labels->shift())))
return $this->nameerr($labels);
if (is_null($n=$this->parse('n',$labels->shift())))
return $this->nameerr($labels);
if (is_null($z=$this->parse('z',$labels->shift())))
return $this->nameerr($labels);
if (is_null($d=$labels->shift()))
return $this->nameerr($labels);
// Make sure we have a root/base domain
if (! $labels->count())
return $this->nameerr($labels);
$rootdn = $labels->join('.');
$ao = Address::findFTN(sprintf('%d:%d/%d.%d@%s',$z,$n,$f,$p,$d));
// Check we have the right record
if ((! $ao) || (! $ao->system->mailer_address) || (($rootdn !== 'ftn') && ((! $ao->zone->domain->dnsdomain) || ($ao->zone->domain->dnsdomain !== $d.'.'.$rootdn))))
return $this->nameerr($labels);
// Get the query type/class
$result = unpack('ntype/nclass',$x=$this->read(4));
// If the wrong class
if ($result['class'] !== self::DNS_QUERY_IN) {
Log::error(sprintf('%s:! We only service Internet queries [%d]',self::LOGKEY,$result['class']));
$this->reply(self::DNS_NOTIMPLEMENTED);
return;
}
// Check the class
switch ($result['type']) {
case self::DNS_TYPE_CNAME:
case self::DNS_TYPE_A:
case self::DNS_TYPE_AAAA:
Log::debug(sprintf('%s:= Returning [%s] for DNS query [%s]',self::LOGKEY,$ao->system->mailer_address,$ao->ftn));
$this->reply(
self::DNS_NOERROR,
$this->question,
[serialize(explode('.',$ao->system->mailer_address)) => self::DNS_TYPE_CNAME]);
break;
default:
Log::error(sprintf('%s:! We dont support DNS query types [%d]',self::LOGKEY,$result['type']));
$this->reply(self::DNS_NOTIMPLEMENTED);
}
}
/**
* Return a compression string for a specific offset
*
* @param int $offset
* @return string
*/
private function compress(int $offset): string
{
return pack('n',$offset | (3 << 14));
}
private function nameerr(Collection $labels)
{
Log::error(sprintf('%s:! DNS query for a resource we dont manage [%s]',self::LOGKEY,$labels->join('.')));
$this->reply(self::DNS_NAMEERR);
}
/**
* Parse a label for a fido address nibble
*
* @param string $prefix
* @param string $label
* @return string|null
*/
private function parse(string $prefix,string $label): ?string
{
$m = [];
return (preg_match('/^'.$prefix.'([0-9]+)+/',$label,$m) && ($m[1] <= DomainController::NUMBER_MAX))
? $m[1]
: NULL;
}
/**
* Return a DNS response
*
* @param int $code
* @param string $question
* @param array $answer
* @return bool
*/
private function reply(int $code,string $question='',array $answer=[]): bool
{
$header = (1 << 15); // 1b: Query/Response
$header |= (0 << 11); // 4b: Opcode
$header |= (0 << 10); // 1b: Authoritative Answer
$header |= (0 << 9); // 1b: Truncated
$header |= (0 << 8); // 1b: Recursion Desired (in queries)
$header |= (0 << 7); // 1b: Recursion Available (in responses)
$header |= (0 << 4); // 3b: Zero (future, should be zero)
$header |= $code; // 4b: Result Code
$q = $question ? 1 : 0;
$r = count($answer);
$nscount = 0;
$arcount = 0;
$reply = pack('nnnnnn',$this->header['id'],$header,$q,$r,$nscount,$arcount);
// Return the answer
if ($r) {
// Question
$reply .= $question;
// @todo In the case we return a CNAME and an A record, this should reference the CNAME domain when returning the A record
foreach ($answer as $item => $type)
$reply .= $this->rr($this->compress(12),unserialize($item),$type,300);
} else {
$reply .= $question;
}
// nscount
//$reply .= $this->rr($this->domain_split('net1.fsxnet.nz'),["a","root-servers","net"],self::DNS_TYPE_NS,300);
if (! socket_sendto($this->socket,$reply,strlen($reply),0,(string)$this->remote['ip'],(int)$this->remote['port'])) {
Log::error(sprintf('%s:! Error [%s] sending DNS reply to [%s:%d]',
self::LOGKEY,
socket_strerror(socket_last_error()),
$this->remote['ip'],
$this->remote['port']
));
return FALSE;
}
return TRUE;
}
private function domain_split(string $domain): string
{
$a = '';
foreach (explode('.',$domain) as $item)
$a .= pack('C',strlen($item)).$item;
return $a;
}
/**
* Read from a rx_buf
*
* @param int $len
* @return string
*/
private function read(int $len): string
{
$result = substr($this->rx_buf,$this->rx_ptr,$len);
$this->rx_ptr += $len;
return $result;
}
/**
* Return a DNS Resource Record
*
* @param string $query - Domain in the query
* @param mixed $ars - Answer resources
* @param int $type - Resource type
* @param int $ttl - Time to live
* @return string
*/
private function rr(string $query,mixed $ars,int $type,int $ttl): string
{
// Reference the domain query in the question
$reply = $query;
// Record Type
$reply .= pack('n',$type);
// Internet
$reply .= pack('n',self::DNS_QUERY_IN);
$reply .= pack('n',0);
// TTL
$reply .= pack('n',$ttl);
// Answer
$a = '';
switch ($type) {
case self::DNS_TYPE_CNAME:
case self::DNS_TYPE_NS:
foreach ($ars as $item)
$a .= pack('C',strlen($item)).$item;
$a .= "\x00";
break;
case self::DNS_TYPE_A:
case self::DNS_TYPE_AAAA:
$a .= $ars;
}
$reply .= pack('n',strlen($a)).$a;
return $reply;
}
/**
* Unpack our configured DNS header
*
* @param array $pack
* @return string
*/
protected static function unpackheader(array $pack): string
{
return join('/',
collect($pack)
->sortBy(function($k,$v) {return $k[0];})
->transform(function($k,$v) {return $k[1].$v;})
->values()
->toArray()
);
}
}