lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <20050702071212.GD23228@hardened-php.net> Date: Sat Jul 2 08:14:08 2005 From: sesser at hardened-php.net (Stefan Esser) Subject: Advisory 05/2005: Cacti Authentification/Addslashes Bypass Vulnerability -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hardened - PHP Project www.hardened-php.net -= Security Advisory =- Advisory: Cacti Authentification/Addslashes Bypass Vulnerability Release Date: 2005/07/01 Last Modified: 2005/07/01 Author: Stefan Esser [sesser@...dened-php.net] Application: Cacti <= 0.8.6e Severity: A HTTP headers bypass switch can also be used to completely bypass the authentification system of Cacti. As admin it is possible to execute shell commands with the permission of the webserver. Risk: Critical Vendor Status: Vendor has released an updated version References: http://www.hardened-php.net/advisory-052005.php Overview: Quote from http://www.cacti.net "Cacti is a complete network graphing solution designed to harness the power of RRDTool's data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices." While looking at the source of Cacti a HTTP headers bypass switch was discovered, that also switches off a call to session_start() and the manual application of addslashes() in case of magic_quotes_gpc=Off. When register_globals is turned on* an attacker can use this switch to disables Cacti's use of PHP's session support and therefore supply the session variables on his own through f.e. the URL. Additionally using the switch renders several SQL statements vulnerable to SQL Injections attacks, when magic_quotes_gpc is turned off, which is the recommended setting. Logged in as an admin it is possible to issue shell commands. (*) register_globals is turned off by default since PHP 4.2 but is activated on most servers because of older scripts requiring it. Details: Within "config.php" there is code to bypass the output of several HTTP headers for caching purposes. This is controlled by the 'no_http_headers' switch. When register_globals is on a potential attacker can control this f.e. through one of the URL variables. if ((isset($no_http_headers) ? $no_http_headers : false) != true) { /* we don't want these pages cached */ header("Expires: Mon, 26 Jul 1997 05:00:00 GMT"); ... header("Pragma: no-cache"); /* initilize php session */ session_start(); /* detect and handle get_magic_quotes */ if (!get_magic_quotes_gpc()) { function addslashes_deep($value) { $value = is_array($value) ? array_map('addslashes_deep', $value) : addslashes($value); return $value; } $_POST = array_map('addslashes_deep', $_POST); $_GET = array_map('addslashes_deep', $_GET); $_COOKIE = array_map('addslashes_deep', $_COOKIE); } ... } The problem with this is, that not calling session_start() also means, that the _SESSION superglobal is never created and therefore it is possible to overwrite _SESSION["sess_user_id"] or other session variables because of register_globals. This means that any request, that comes f.e. with a Cookie: _SESSION[sess_user_id]=1;no_http_headers=1; will be automaticly logged in as user 1 (which is usually the admin). On the other hand it is quite obvious that the no_http_headers switch will disable the automatic addslashes() on _GET, _POST and _COOKIE which can lead f.e. to SQL Injections on the login formular when magic_quotes_gpc is turned off, which is the recommended setting. Logged in as an admin the attacker can execute arbitrary shell commands by f.e. changing the path to rrdtool in the configuration into commands of his choice and then triggering it by viewing a graph. Because of this register_globals=On problem we recommendend that the Cacti developers add a register_globals deregistration layer to Cacti. This is usually a recommendation from us to everyone writing PHP applications, because programmers that use the _GET, _POST and _COOKIE superglobals are often under the wrong assumption, that their code will only run on servers with register_globals turned off and still do not initialise their variables properly. Proof of Concept: The Hardened-PHP Project is not going to release exploits for this vulnerabilities to the public. Disclosure Timeline: 25. June 2005 - Contacted Cacti developers via email 29. June 2005 - Review of patch from our side 1. July 2005 - Release of updated Cacti and Public Disclosure Recommendation: We strongly recommend upgrading to Cacti 0.8.6f which you can get at http://www.cacti.net/download_cacti.php 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 Stefan Esser. All rights reserved. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQFCxBccRDkUzAqGSqERAppnAJ9xNIh1kY7wAtKu/LysBiMHwlpJFgCg6FtK wb123sPmzM3MRmGtc0PDb/w= =Wk7r -----END PGP SIGNATURE-----
Powered by blists - more mailing lists