From customerservice@idefense.com Mon Feb 7 15:20:07 2005 From: iDefense Customer Service To: bugtraq@securityfocus.com, vulnwatch@vulnwatch.org Date: Mon, 7 Feb 2005 15:03:01 -0500 Subject: iDEFENSE Security Advisory 02.07.05: SquirrelMail S/MIME Plugin Command Injection Vulnerability SquirrelMail S/MIME Plugin Command Injection Vulnerability iDEFENSE Security Advisory 02.07.05 www.idefense.com/application/poi/display?id=191&type=vulnerabilities February 07, 2005 I. BACKGROUND Squirrelmail S/MIME plugin enables the viewing of S/MIME-signed messages of the MIME "multipart/signed" format. More information about the plugin is available at: http://www.squirrelmail.org/plugin_view.php?id=54 II. DESCRIPTION Remote exploitation of a command injection vulnerability in the Squirrelmail S/MIME plugin allows web mail users to execute arbitrary commands with the privileges of the web server. The problem specifically exists due to insufficient filtering of user-provided data in a call to exec(). The following snippet exposes the offending area of code from viewcert.php: if(!isset($cert)) $cert=$_GET['cert']; ... function x509_open($cert) { global $cert_in_dir, $openssl; $lines = array(); exec("$openssl x509 -in $cert_in_dir$cert -subject -issuer \ -dates -serial -fingerprint -noout 2>/tmp/err", $lines); ... list ($ow, $is, $nb, $na, $sn, $fp) = x509_open($cert); The variable '$cert' from the above snippet contains unfiltered user supplied data and can be exploited. III. ANALYSIS Successful exploitation allows authenticated web mail users to execute arbitrary commands on the underlying system with the privileges of the web server. This can lead to further compromise and exposure of other users' mail to the attacker. IV. DETECTION iDEFENSE has confirmed the existence of this vulnerability in S/MIME plugin 0.5 and 0.4. Earlier versions are also suspected to be vulnerable. V. WORKAROUND PHP provides the escapeshellarg() routine to filter data to be used as an argument to calls such as exec() and system(). Modify the call to exec() from: exec("$openssl x509 -in $cert_in_dir$cert -subject -issuer -dates \ -serial -fingerprint -noout 2>/tmp/err", $lines); To: $filtered = escapeshellarg("$cert_in_dir$cert"); exec("$openssl x509 -in $filtered -subject -issuer -dates -serial \ -fingerprint -noout 2>/tmp/err", $lines); VI. VENDOR RESPONSE The vendor has released S/MIME plugin 0.6 to address this vulnerability. The plugin is available for download at: http://www.squirrelmail.org/plugin_view.php?id=54 VII. CVE INFORMATION A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet. VIII. DISCLOSURE TIMELINE 09/22/2004 Initial vendor notification 09/22/2004 Initial vendor response 02/07/2005 Coordinated public disclosure IX. CREDIT Karol Wiesek is credited with this discovery. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp X. LEGAL NOTICES Copyright (c) 2005 iDEFENSE, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice@idefense.com for permission. Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.