Hardened-PHP Project Security Advisory 2005-21.81

`-----BEGIN PGP SIGNED MESSAGE-----  
Hash: SHA1  
  
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 <[email protected]>  
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_212005.81.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.  
  
-----BEGIN PGP SIGNATURE-----  
Version: GnuPG v1.0.6 (GNU/Linux)  
Comment: For info see http://www.gnupg.org  
  
iD8DBQFDdyOFRDkUzAqGSqERAt9KAJ4uCXhrcapN/zxWDS6n7y8ezp6xsQCgw28i  
HSdHc4zKJ8aCj5gSC8Zxlj4=  
=XRw5  
-----END PGP SIGNATURE-----  
`