Advisory 22/2005:Multiple vulnerabilities in phpSysInfo




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Hardened PHP Project
www.hardened-php.net

-= Security Advisory =-


Advisory: Multiple vulnerabilities in phpSysInfo
Release Date: 2005/11/13
Last Modified: 2005/11/12
Author: Christopher Kunz <christopher.kunz@hardened-php.net>
Application: phpSysInfo 2.4 and prior
Severity: Cross-Site Scripting, HTTP Response Splitting,
Arbitrary local file inclusion
Risk: Medium
Vendor Status: Vendor has released an updated version.
References: http://www.hardened-php.net/advisory_222005.81.html

Overview:

phpSysInfo is a PHP script that displays information about the host being
accessed. It will displays things like Uptime, CPU, Memory, SCSI, IDE, PCI,
Ethernet, Floppy, and Video Information.
A number of holes - all of them attributed to a rather crude (and unneeded)
register_globals emulation - allow for arbitrary file inclusion, amongst
other things.


Details:

It is important to note that due to the nature of phpSysInfo, it is unlikely
to be run inside an open_basedir, since most of the information the software
obtains is from the /proc or /etc directories. Furthermore, few admin-
istrators will restrict its access to PHP's shell functions, since a such
restriction would render the software unusable. In fact, the author requires
that safe_mode be set to Off and no other restrictions be imposed on the PHP
installation.

A hole that was reported in CVE-2003-0536 and is reported as "fixed" in the
phpSysInfo README still persists. The reason for this problem lies in the
incorrect handling of variables by the "globalization layer" implemented in
phpSysInfo's index.php - quote:
if (!empty($HTTP_GET_VARS)) while (list($name, $value) =
each($HTTP_GET_VARS)) $$name = $value;
if (!empty($HTTP_POST_VARS)) while (list($name, $value) =
each($HTTP_POST_VARS)) $$name = $value;
As the interested reader will easily see, this two-liner overwrites the
complete scope, including the superglobal variable $_SERVER. By injecting
a local path name into $_SERVER['HTTP_ACCEPT_LANGUAGE'], an attacker can now
include arbitrary files. If they have a way to create content on the target
server (such as an entry in syslog or the web server log file), they can use
this to execute arbitrary code.
In the Debian Sarge package, injecting only HTTP_ACCEPT_LANGUAGE is suffi-
cient - the current source tree (phpsysinfo-dev from sf.net) requires the
attacker to additionally inject the $lng parameter.
Example: /index.php?_SERVER[HTTP_ACCEPT_LANGUAGE]=../../README%00
/index.php?_SERVER[HTTP_ACCEPT_LANGUAGE]=../../README%00&lng=../../
README%00

The variable $sensor_program is set in config.php, but can be overwritten
since config.php is actually included *before* reglobalization takes place.
With this variable, arbitrary file inclusion is possible on some platforms,
dependant on the local realpath() implementation.
Example: /index.php?sensor_program=lmsensors.inc.php/../../README%00

Additionally, $sensor_program can *still* be used to inject active contents
into the page, known as Cross-Site Scripting. This issue was discussed in
CVE-2005-0870 and still exists. The other XSS holes mentioned in that ad-
visory are still valid, too. They can be abused with register_globals Off,
this is different from the advisory by ISS. It is, however, not exploitable
on Debian systems.
An additional attack vector for Cross-Site Scripting attacks is the variable
$VERSION, which is used for the version string displayed on the bottom of
each page.
Example: /index.php?VERSION=%22%3E%3Cscript%3Ealert('xss')%3C/script%3E

A fairly unknown attack class is so-called HTTP Response Splitting, an at-
tack that allows for "selective defacement" of web pages by poisoning for-
warding or reverse proxies. An explanation of this attack class is beyond
the scope of this advisory, a whitepaper can be obtained at [1].
Using HTTP Response Splitting, arbitrary strings can be injected into the
variable $charset, which is meant to include a value such as "iso-8859-1"

or similar, but is only set to a value inside a language include file if a
language in fact requires a character set different from iso-8859-1. In all
other cases, it can be set via the URL. This variable is fed to a header()
call without any additional checks. By breaking up the argument with \r\n,
the attacker can inject a complete second HTTP response. This response is
the only one that will be returned by any intermediate proxy, showing what-
ever HTML the attacker injected previously.
Example:
/index.php?charset=%0d%0aContent-Length:%200%0d%0a%0d%0aHTTP/1.1%20200%20OK%
0d%0aContent-Type:%20text/html%0d%0aContent-Length:%2019%0d%0a%0d%0a<html>Ha
cked!</html>
This example will print out a simple (and invalid) HTML page containing only
the string "Hacked!" if the victim accesses the phpSysInfo instance from be-
hind a proxy. Direct access will probably yield an empty page, since many
browsers do not know how to handle more than one response to a HTTP request.


Proof of Concept:

The examples above should provide you with enough PoC to validate the ex-
istance of the vulnerabilities.


Disclosure Timeline:

10. November 2005 - Bug disclosed to vendor.
10. November 2005 - Updated version 2.4 released.
11. November 2005 - 2.4 does not seem to fix - own patch sent to vendor.
12. November 2005 - New updated version 2.4.1 fixes the issues.
13. November 2005 - Public disclosure.


Credits:

All vulnerabilities were investigated by the Hardened-PHP Project. Credit to
referred vulnerabilities goes to the original authors, as mentioned on CVE.


Recommendation:

We have provided a bugfix to the vendor, which, in addition to their own
fix, will be included in version 2.4.1 of phpSysInfo.
We also recommend installing the Hardening Patch for PHP which would have
mitigated the response splitting problem (by not allowing multiline headers)
and the $_SERVER overwriting issues (by not allowing certain superglobals to
be overwritten from the outside).
If you want to fix the issue yourself, just comment out the lines mentioned
in an earlier paragraph of this advisory and selectively infer the variables
$_REQUEST['lng'] and $_REQUEST['template'] from the outside.
Additionally, access to the includes/ directory should be restricted by
appropriate means, e.g. a .htaccess file.


CVE Information:

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CVE-2005-3347 to the file inclusion issue and the name
name CVE-2005-3348 to the HTTP response splitting problem.


References:

[1] http://www.packetstormsecurity.org/papers/general/whitepaper_httprespons
e.pdf
[2] http://phpsysinfo.sourceforge.net/


Plug:

You can discuss this and other vulnerabilities in our forum at
http://forum.hardened-php.net/ - an up-to-date list of advisories can be
found at http://www.hardened-php.net/.


GPG-Key:

http://www.hardened-php.net/hardened-php-signature-key.asc

pub 1024D/0A864AA1 2004-04-17 Hardened-PHP Signature Key
Key fingerprint = 066F A6D0 E57E 9936 9082 7E52 4439 14CC 0A86 4AA1

Copyright 2005 Christopher Kunz / Hardened PHP Project. All rights reserved.

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