SquirrelMail G/PGP Plugin deleteKey() Command Injection Vulnerability
iDefense Security Advisory 07.11.07 http://labs.idefense.com/intelligence/vulnerabilities/ Jul 11, 2007
The SquirrelMail G/PGP Encrpytion Plugin is a general purpose encryption, decryption, and digital signature plug-in for SquirrelMail that implements the OpenPGP standard using GPG. More information is available at the following URL.
Remote exploitation of a command injection vulnerability in the G/PGP Encrpytion Plugin for The SquirrelMail Project Team's SquirrelMail webmail package allows attackers to execute arbitrary commands with the privileges of the underlying web server.
The problem specifically exists within the function deleteKey() defined in gpg_keyring.php. A call is made to exec() with unfiltered user-supplied data as demonstrated in the following piece of code:
$command = "$path_to_gpg --batch --no-tty --yes --homedir \ $gpg_key_dir $flag $fpr 2>&1"; exec($command, $output, $returnval);
The deleteKey() routine is called from three files: import_key_file.php, import_key_text.php and keyring_main.php. the '$fpr' variable from above is supplied in the POST data. The attacker must have a valid authenticated session to exploit this vulnerability.
Exploitation of the described vulnerability allows authenticated remote attackers to execute arbitrary commands with the privileges of the underlying web server.
This vulnerability could be exploited by webmail users to gain shell access on the target server and potentially further compromise the system with local privilege escalation vulnerabilities.
iDefense has confirmed the existence of this vulnerability in the latest version of the G/PGP Encryption Plugin for SquirrelMail, version 2.1. Furthermore, this vulnerability has been confirmed to exist as early as version 2.0. Other versions may be affected.
Disable the G/PGP Plugin if it is not required. Alternatively, add the following line above the initialization of the '$command' variable just prior to the call to exec():
$fpr = escapeshellarg($fpr);
Please note that this is an unofficial source patch, but should be sufficient as a workaround until an official patch is released from the vendor.
VI. VENDOR RESPONSE
The maintainers of the SquirrelMail G/PGP plug-in have not responded to repeated inquires regarding this vulnerability. As such, it remains unpatched, even in the most current release made on July 7th, 2007.
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2005-1924 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.
VIII. DISCLOSURE TIMELINE
10/27/2005 Initial vendor notification 10/27/2005 Initial vendor response 03/02/2006 Second vendor notification 02/16/2007 Third vendor notification 07/11/2007 Public disclosure
The discoverer of this vulnerability wishes to remain anonymous.
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X. LEGAL NOTICES
Copyright © 2007 iDefense, Inc.
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