bugtraq - Re: @(#)Mordred Labs advisory - Integer overflow in PHP str

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Date: Fri, 4 Apr 2003 00:10:32 +0200
From: Jedi/Sector One <j@...eftpd.org>
To: Goran Krajnovic <goran.krajnovic@...et.hr>
Subject: Re: @(#)Mordred Labs advisory - Integer overflow in PHP str_repeat() function

On Thu, Apr 03, 2003 at 08:39:03AM +0200, Goran Krajnovic wrote:
> This is a bit pointless, IMHO. 99% of PHP installations run the PHP code with
> the user-id of the web server process (usually a low privilege user like
> 'nobody' or 'apache').
[snip snip]
> If an attacker has the opportunity to execude PHP code of his choice on a
> target server [1], he does not need to exploit a buffer overflow in PHP just to
> get the privileges of the web server user

  You missed an important point.

  Hosting services offering a PHP interpreter to untrusted people rely on
PHP features to restrict their field of action.

  Specifically, the open_basedir and safe_mode features are a must to avoid
people going outside their home directory with PHP scripts.

  If arbitrary code can be run through a PHP vulnerability, these
restrictions disappear. People can walk through files that are supposed to
be inaccessible.

  Given that many people just chmod -R 777 their directories when their
script doesn't work and leave plaintext SQL passwords everywhere, this is
definitely ann issue.

  Also don't forget that all PHP extensions aren't always enabled. For
instance, the socket extension is typically disabled by most hosting service
providers for obvious reasons.

  Once and again, a vulnerability in the PHP interpreter can bypass this
restriction and gain access to other machines of the LAN, run DOS agents, etc.

  Of course, one shouldn't rely 100% on PHP userland security barriers, this
is where tools like NetBSD/OpenBSD's systrace can really add another
efficient layer of security.

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