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


=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
DESCRIPTION
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

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:
$user =3D escapeshellarg($_GET['user']);
$pwd =3D escapeshellarg($_GET['pwd']);

system("htpasswd -nb $user $pwd", $return);
If an attacker enters '" || dir || ' (without the single quotes) for
user (or pwd), the command dir is executed.


=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
GENERAL REMARKS
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

- 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).

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D
Recommended Hotfixes
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3 D=3D=3D=3D

Update PHP to version 4.3.7.


EOF Daniel Fabian / @2004
d.fabian at sec-consult dot com

=3D=3D=3D=3D=3D=3D=3D
Contact
=3D=3D=3D=3D=3D=3D=3D

SEC CONSULT Unternehmensberatung GmbH

B=FCro 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