linux-kernel - Re: Network isolation with RLIMIT

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Message-Id: <200912131032.24251.remi@remlab.net>
Date:	Sun, 13 Dec 2009 10:32:20 +0200
From:	"Rémi Denis-Courmont" <remi@...lab.net>
To:	Michael Stone <michael@...top.org>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>, David Lang <david@...g.hm>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Bryan Donlan <bdonlan@...il.com>,
	Evgeniy Polyakov <zbr@...emap.net>,
	"C. Scott Ananian" <cscott@...ott.net>,
	James Morris <jmorris@...ei.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Bernie Innocenti <bernie@...ewiz.org>,
	Mark Seaborn <mrs@...hic-beasts.com>
Subject: Re: Network isolation with RLIMIT_NETWORK, cont'd.

	Hello,

Le dimanche 13 décembre 2009 05:44:18 Michael Stone, vous avez écrit :
> You were all meant to be included on the CC-list for the letter and patches
> which I just sent to lkml:
> 
>    http://lkml.org/lkml/2009/12/12/149

You explicitly mention the need to connect to the X server over local sockets.  
But won't that allow the sandboxed application to send synthetic events to any 
other X11 applications? Hence unless the whole X server has restricted network 
access, this seems a bit broken? D-Bus, which also uses local sockets, will 
exhibit similar issues, as will any unrestricted IPC mechanism in fact.

I am not sure if restricting network access but not other file descriptors 
makes that much sense... ? Then again, I'm not entirely clear what you are 
trying to solve.

If I had to sandbox something, I'd drop the process file limit to 0. That will 
effectively cut off network, file system, and POSIX IPCs. Unfortunately, the 
process can still use SysV IPC, ptrace(), and send signals to others. So those 
are the gaps I would first try to contain.

-- 
Rémi Denis-Courmont
http://www.remlab.net/
http://fi.linkedin.com/in/remidenis
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