PHP escapeshellarg Windows Vulnerability
SEC-CONSULT Security Advisory - PHP: Hypertext Preprocessor
Vendor: PHP (http://www.php.net)
Product: PHP 4.3.6 and below (verified in 4.3.5 which was current when
the bug was discovered)
Vendor status: vendor contacted (04-04-2004)
Patch status: Problem fixed in 4.3.7
===========
DESCRIPTION
===========
PHP offers the function escapeshellarg() to escape arguments to shell
commands in a way that makes it impossible for an attacker to execute
additional commands. However due to a bug in the function, this does not
work with the windows version of PHP.
Vulnerable is for example the following code:
[code]
$user = escapeshellarg($_GET['user']);
$pwd = escapeshellarg($_GET['pwd']);
system("htpasswd -nb $user $pwd", $return);
[/code]
If an attacker enters '" || dir || ' (without the single quotes) for
user (or pwd), the command dir is executed.
===============
GENERAL REMARKS
===============
- The bug was successfully verified in PHP 4.3.3 and 4.3.5. In former
version (4.3.3) the execution of additional commands was only possible
when single quotes were used.
- While correcting the vulnerability, the PHP staff seems to have
noticed that the function escapeshellcmd is vulnerable too (according to
the changelog of v4.3.7).
====================
Recommended Hotfixes
====================
Update PHP to version 4.3.7.
EOF Daniel Fabian / @2004
d.fabian at sec-consult dot com
=======
Contact
=======
SEC CONSULT Unternehmensberatung GmbH
Büro Wien
Blindengasse 3
A-1080 Wien
Austria
Tel.: +43 / 1 / 409 0307 - 570
Fax.: +43 / 1 / 409 0307 - 590
Mail: office at sec-consult dot com
http://www.sec-consult.com