Xerox WorkCentre 5665/5675/5687 Backdoor

Type packetstorm
Reporter Daniel Fabian
Modified 2010-02-23T00:00:00


                                            `SEC Consult Security Advisory < 20100208-0 >  
title: Backdoor and Vulnerabilities in Xerox   
WorkCentre Printers Web Interface  
products: Xerox WorkCentre 5665/5675/5687  
vulnerable version: and possibly others  
fixed version:  
impact: critical  
found: 2009-10-05  
by: D. Fabian / SEC Consult /  
Vendor description:  
WorkCentre 5665 / 5675 / 5687  
High-speed performance, outstanding productivity and advanced  
multifunction capabilities. These are the essentials of the all-in-one  
offce powerhouse that easily handles the high-volume print demands of  
large, busy workgroups. And with robust copying, scanning, faxing and a  
host of innovative Xerox technologies, you get a total workfow solution  
that excels at streamlining your unique job processes.  
Vulnerability 1: Backdoor to Mailboxes  
For some reasons, Xerox decided to integrate a backdoor into the scan  
system of the WorkCentre 5665 / 5675 / 5678 web interface. Scan folders  
("mailboxes") can be protected with a password. The documentation says  
on folder passwords:  
"A folder password may or may not be required depending on the Scan  
Policies set by the administrator. If a password is required to create  
a folder, type the password here. If no password is required by the  
Scan Policies, you can optionally choose whether or not to password  
protect your folder."  
Some files require a job password. If someone tries to access a private  
folder without logging in previously, this does not work since a cookie  
is compared to a precomputed checksum. However there is a script named  
"YoUgoT_It.php" that creates the correct checksum for any folder. By  
simply calling the script with the folder name as argument, an attacker  
can access any folder.  
Here is the relevant code from the file folder.php that allows access,  
if the checksum is correct:  
/* see if the private folder is trying to be accessed, without  
logging in previously; this can be done by checking to see if  
the cookie matches the computed "checksum" */  
if ( $gFolderName === $_SESSION['MBOX_FOLDER'] )  
// continue on as this is okay  
elseif (( false === isset( $_COOKIE[$gFolderName] )) ||  
( $theChecksum !== $_COOKIE[$gFolderName] ))  
header( "Location: /mailbox/pin.php?" . NAME_KEY .  
"=" . $gFolderName ); exit;  
Vulnerability 2: Authentication not validated  
In multiple instances, when a password is required to access certain  
pages, the developers seemed to forget the vital "die()" or "exit()"  
statement after the redirect. This allows an attacker access to  
multiple pages that would require authentication.  
Here are a couple of examples:  
if ( "" === $gUserName )  
header( "Location: /properties/authentication/login.php?redir=" .  
elseif ( false === $gSaLoggedIn )  
header( "Location: /properties/no_modify.php" );  
/php_includes/sa_check.php: This script seems to check whether the  
currently logged in user is an administrative user  
if ( "" === $gUserName )  
header( "Location: /properties/authentication/login.php?redir=" .  
elseif (( false === $gSaLoggedIn ) &&  
( "" !== $gUserName ))  
header( "Location: /properties/no_modify.php" );  
As you can see from the code, if the user is logged in, but not an  
administrator, he is correctly denied access. However if the  
user is not logged in at all, only a Location-header is sent,  
but the rest of the script can continue to run.  
The very same vulnerability can be found in many cases. In some cases,  
the authentication is also only in the page that provides only the  
frameset. The actual content-pages can be called without any  
authentication at all.  
Vulnerable versions:  
The vulnerabilities were discovered in version It is  
likely that other versions are affected also.  
Vendor contact timeline:  
2009-10-06: Contacting the Xerox Security Team via Email  
Advisory URL:  
SEC Consult Unternehmensberatung GmbH  
Office Vienna  
Mooslackengasse 17  
A-1190 Vienna  
Tel.: +43 / 1 / 890 30 43 - 0  
Fax.: +43 / 1 / 890 30 43 - 25  
Mail: research at sec-consult dot com  
SEC Consult conducts periodical information security workshops on ISO   
27001/BS 7799 in cooperation with BSI Management Systems. For more   
information, please refer to  
EOF D. Fabian / @2009