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Credit:
The information has been provided by Christopher Kunz.
The original article can be found at: http://www.hardened-php.net/advisory_212005.81.html
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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 administrators 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 sufficient - 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 attack that allows for "selective defacement" of web pages by poisoning forwarding or reverse proxies. An explanation of this attack class is beyond the scope of this advisory.
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 whatever HTML the attacker injected previously.
Example:
/index.php?charset=%0d%0aContent-Length:%200%0d%0a%0d%0aHTTP/1.1 200 OK%0d%0aContent-Type: text/html%0d%0aContent-Length: 19%0d%0a%0d%0a<html>Hacked!</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 behind 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.
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.
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:
CVE-2005-3347
CVE-2005-3348
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