linux-kernel - Re: [patch 7/8] fdmap v2

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Message-ID: <20070609151521.GD4095@ftp.linux.org.uk>
Date:	Sat, 9 Jun 2007 16:15:21 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Ulrich Drepper <drepper@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Davide Libenzi <davidel@...ilserver.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Theodore Tso <tytso@....edu>,
	Eric Dumazet <dada1@...mosbay.com>,
	Kyle Moffett <mrmacman_g4@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch 7/8] fdmap v2 - implement sys_socket2

On Fri, Jun 08, 2007 at 07:10:03PM -0700, Ulrich Drepper wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Al Viro wrote:
> > Any real-world examples of exploitable holes based on that?
> 
> Return to libc exploit, calling dup2, where some privileged data is
> redirected from the normal file descriptor to one of the attackers
> choosing.  The latter could be an outgoing socket connection which would
> result in leaking the data to the outside.
> 
>          normal code                         intruder
> 
>                                           so = socket()
> 
>     fd = open ("local-file")
> 
>                                           dup2(so, fd);
> 
>     write (fd, privileged data)
> 
> 
> It's just a little function call.  If the arguments of dup2() are known
> this is not a big issue to construct.

So which code is supposed to do that open/write in your example?  Library?
Unmodified application?  Application specifically modified to make *that*
open() randomized?
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