ip.php

<?php
/*
 * Copyright (C) 2010 Daniel Richman
 * This is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this.  If not, see <http://www.gnu.org/licenses/>.
 */

@error_reporting(E_ALL);
Header("Content-type: text/plain");

/* Get info */
$remote_ip = $_SERVER["REMOTE_ADDR"];
$remote_port = $_SERVER["REMOTE_PORT"];
$local_ip = $_SERVER["SERVER_ADDR"];
$local_port = $_SERVER["SERVER_PORT"];
$rdns = get_rdns($remote_ip);
$ident = get_ident($local_port, $remote_ip, $remote_port, 1);

/* Add failure notices */
if ($rdns == false)	$rdns = "None";
if ($ident == false)	$ident = "No response";

/* Print output */
echo "HTTP Server:  $local_ip:$local_port\n";
echo "HTTP Client:  $remote_ip:$remote_port\n";
echo "Client RDNS:  $rdns\n";
echo "Client Ident: $ident\n";

/* Functions */
function get_ident($local_port, $remote_ip, $remote_port, $timeout)
{
	$query = "$remote_port, $local_port\n";

	$errno = 0;
	$errstr = '';
        $socket = @fsockopen($remote_ip, 113, $errno, $errstr, $timeout);
        if (!$socket)   return false;

        $result = @socket_set_timeout($socket, $timeout);
        if (!$result)   { @fclose($socket); return false; }

        $result = @fwrite($socket, $query);
        if (!$result)   { @fclose($socket); return false; }

        $response = @fread($socket, 1024);
        @fclose($socket);

	if (!$response || strlen($response) == 0)	return false;

	$response_array = @explode(':', $response);
	if (count($response_array) < 3)			return false;

	$response_port_array = explode(',', $response_array[0]);
	if (trim($response_port_array[0]) != $remote_port ||
	    trim($response_port_array[1]) != $local_port)
		return false;

	array_shift($response_array);
	foreach ($response_array as $key => $value)
		$response_array[$key] = trim($value);

	return implode(' : ', $response_array);
}

function get_rdns($ip)
{
	$segments = array_reverse(explode('.', $ip));
	$segments[] = "in-addr";
	$segments[] = "arpa";
	$result = timed_dns($segments, 12 /* QTYPE PTR */, '8.8.4.4', 1);

	if ($result === false)	return false;
	return implode('.', $result);
}

assert(mt_getrandmax() >= 65535);
function timed_dns($segments, $type, $server, $timeout)
{
	/* Header */
	$identifier = mt_rand(0, 65535);
	$header_length = 12;
	$header = pack('nC2n4',
			$identifier,
			0x01, /* options1: RD set, all others unset. */
			0x00, /* options2: unset */
			1, 0, 0, 0); /* one question, no answers, etc. */
	assert(strlen($header) == $header_length);

	/* Question Section */
	$data = '';
	foreach ($segments as $segment)
	{
		$data .= pack('C', strlen($segment));
		$data .= $segment;
	}

	$data .= pack('Cnn',
			0, /* Null terminator */
			$type, /* QTYPE */
			1); /* QCLASS: 1 - internet */

	$errno = 0;
	$errstr = '';
        $socket = @fsockopen("udp://$server", 53, $errno, $errstr, $timeout);
	if (!$socket)	return false;

	$result = @socket_set_timeout($socket, $timeout);
	if (!$result)	{ @fclose($socket); return false; }

	$result = @fwrite($socket, $header.$data);
	if (!$result)	{ @fclose($socket); return false; }

	$response = @fread($socket, 1024);
	@fclose($socket);
	if (!$response || strlen($response) == 0)	{ return false; }

	/* Unpack the header */
	$reply_header = unpack('nid/C2op/n4c',
				substr($response, 0, $header_length));

	/* Inspect the header */
	if ($reply_header["id"] != $identifier)	return false; /* wrong ID */
	if (!($reply_header["op1"] & 0x80))	return false; /* not a reply */
	if (($reply_header["op2"] & 0x0F)!= 0)	return false; /* error */
	if ($reply_header["c1"] != 1)		return false; /* qdcount bad */
	if ($reply_header["c2"] == 0)		return false; /* ancount bad */

	/* Check the query was the same */
	if ($data != substr($response, $header_length, strlen($data)))
		return false;
	
	/* Grab the first answer */
	$answer = substr($response, $header_length + strlen($data));

	$answer_info_len = 12;
	$answer_info = unpack('nname/ntype/nclass/Nttl/nrdlength',
				substr($answer, 0, $answer_info_len));
	if ($answer_info["type"] != $type)		return false;
	if ($answer_info["class"] != 1 /* internet */)	return false;
	if (strlen($answer) != $answer_info["rdlength"] + $answer_info_len)
		return false;

	$answer = substr($answer, $answer_info_len);
	$answer_segments = Array();

	while (true)
	{
		$length_r = unpack('Clen', $answer{0});
		$length = $length_r["len"];
		if (!$length) break;
		$answer_segments[] = substr($answer, 1, $length);
		$answer = substr($answer, 1 + $length);
	}

	/* All done */
	return $answer_segments;
}
?>