PHP 5.2.4 <= various mysql functions safemode & open_basedir bypass Sep 11 2007 04:38AM
laurent gaffie gmail com (2 replies)
Re: PHP 5.2.4 <= various mysql functions safemode & open_basedir bypass Sep 12 2007 12:27PM
Ben Wheeler (b wheeler ulcc ac uk)
Re: PHP 5.2.4 <= various mysql functions safemode & open_basedir bypass Sep 12 2007 05:59AM
Ronald Chmara (ron Opus1 COM)
Two years ago, I wrote a semi similar post to this one, but, well,
I'm old and tired of seeing this now. Time for folks to upgrade.

On Sep 10, 2007, at 9:38 PM, laurent.gaffie (at) gmail (dot) com [email concealed] wrote:

> Application: PHP <=5.2.4
> Web Site: http://php.net
> Platform: unix
> Bug: safemode & open_basedir bypass
> ======
> 2) Bug
> ======
> various mysql functions safemode & open_basedir bypass

Not a PHP *bug*, so much as yet another reason why "safe mode" and
"open_basedir" are fundamentally wrong ideas (and are being
terminated, with prejudice, in future PHP development). Users (and
hosting companies) are unedumacated on how the whole concepts of
permissions work, turn on something they think is "safe", and are
surprised by the results.

> <?php
> mysql_connect("localhost", "granted_user","something");
> mysql_query("select load_file(0x2F6574632F706173737764)into
> dumpfile'/test/123.txt';");
> ?>

In this case:
PHP has basedir restrictions.
Apache has directory restrictions.
....But, well, mysql?

What restrictions have you placed upon it, per user, and filesystem?

Apparently, it's allowed to write to /test/, *and* the user perms
used to talk to mysql seem horribly broad, since it can get user
perms. So, since any Apache/PHP/mysql user on a shared host (or
whatever) in the above scenario can write to whatever they want from
mysql to /test/, it's fair game.

You see, any PHP library used, be it mysql, odbc, *whatever*, that
can be given arguments, *and does not filter* those arguments *in the
library*, based on per-apache-instance-per-user restrictions, can be
used to cross boundaries, escalate boundaries, etc.

Since on a shared host, it's often the case that 20. or 50, or
whatever many users have permissions (though apache and mysql) to
write to any directories that apache and mysql have write permissions
to, yes, PHP can *try* to clean up the activities involves, but it's
a fools errand.

mysql_query("select load_file (foo) into dumpfile'/
# if the mysql user has perms, Game over. PHP/apache isn't even
relevant anymore, if *mysql*
# has perms to write to the user's directory

So, for mental exercise: A GD library creating an "image" in another
directory, because apache and PHP trust GD? How about a PDF file? A
blog backup file?

You see, the problem *isn't* PHP, it's underlying libraries
inheriting perms, and using perms, that are not appropriate for the
purpose of isolating users.

The fix?

Give each user their own apache, their own mysql, their own chroot'ed
box (or vm/xen image..).

Since that's not gonna happen anytime soon for resellers who over-
subscribed their hardware, the current solution seems to be "point
and giggle".


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