Visitorbook LE Multiple Vulnerabilities

[Paul Johnston <paul () westpoint ltd uk>]

Westpoint Security Advisory

Title:        VisitorBook LE Mail Relay and Cross Site Scripting
Risk Rating:  Moderate
Software:     FreeScripts VisitorBook LE
Platforms:    Most Unix
Vendor URL:   http://www.freescripts.com/
Author:       Paul Johnston <paul () westpoint ltd uk>
Date:         10th December 2003
Advisory ID#: wp-03-0001

Overview
========

VisitorBook is a "customizable, database-driven guestbook software ... 
used all
over the net", which fails to escape various control characters in user 
input.
This results in:

 * Mail relaying
 * Data loss
 * Cross site scripting


Details
=======

Open mail relay
---------------
If $mailuser is set to 1 (not the default) then the script can be used as a
mail relay. This arises because line breaks are not escaped in the email 
field,
so you can relay mail by setting the email address to something like:

 victim () example com
 From: spammer () example com
 Subject: $$$ hardcore XXX
 ...

Guestbook database deleting / DoS
---------------------------------
Another consequence of the script failing to escape line breaks is that 
anyone
can remotely delete the log - they just need to submit an entry with 
more line
breaks that the value of $max_posts.

If you do this with Windows line breaks, then the database file is so 
corrupted
afterwards that the script always gives "500 Internal Server Error".

The script also fails to escape pipe "|" characters, which it uses as a 
field
deliminator, although it's unlikely this can be exploited.

Cross site scripting
--------------------
The "do" parameter is not escaped at all, which you can exploit like:
 http://fester/cgi-bin/visitorbook.pl?do=<script>alert('hello')</script>

The user parameter is also not escaped. To exploit this you need to use 
a rogue
DNS server to poison the script with a malicious reverse DNS response. More
about this below. Note: this would be difficult to exploit in practice 
and was
not actually exploited in my tests.

Quote marks are not escaped in any parameters. You can exploit this by 
signing
an entry with a web link like this:
 http://"; onmouseover="alert('hello')" crap="

Also, ampersands (&) are not escaped in any parameters, although it's 
unlikely
this can be exploited.

Trust of reverse dns
--------------------
The script uses the logic that it logs the user's reverse DNS name if
available, or IP address otherwise. The problem with this is that the 
reverse
DNS is untrusted data - someone can easily change their identity by setting
their reverse DNS to, say, "www.whitehouse.gov". This also leads to the 
cross-
site scripting attack mentioned above.


Workarounds
===========

Mail relay
 Disable user mails, by setting $mailuser to 0
Data deleting
 Modify code to escape line break characters on all parameters
Cross site scripting
 Modify code to escape <>&" characters on all parameters
Trusting reverse DNS
 In Apache config set HostNameLookups to Off


Vendor notification
===================

4 Nov 2003    Mailed all the email addresses in the source code, whois 
contacts
             for domain.
             No response.

5 Nov 2003    Raised a support ticket.
             The vendor indicated that the free version of the code had not
             been maintained for some time, but that sharing security 
related
             findings would be much appreciated.

10 Nov 2003   First detailed notification of vulnerabilities.
             No response.

21 Nov 2003   Passed draft advisory to vendor; indicated intention to 
publish
             on 10 Dec.
             No response.

9 Dec 2003    Reminded vendor of impending publication.
             No response.


This advisory is available online at:
 http://www.westpoint.ltd.uk/advisories/wp-03-0001.txt


--
Paul Johnston
Internet Security Specialist
Westpoint Limited
Albion Wharf, 19 Albion Street,
Manchester, M1 5LN
England
Tel: +44 (0)161 237 1028
Fax: +44 (0)161 237 1031
email: paul () westpoint ltd uk
web: www.westpoint.ltd.uk