linux-kernel - Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)

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Message-ID: <20100114092328.GB11500@atrey.karlin.mff.cuni.cz>
Date:	Thu, 14 Jan 2010 10:23:28 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Michael Stone <michael@...top.org>, 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>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Am?rico Wang <xiyou.wangcong@...il.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Samir Bellabes <sam@...ack.fr>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	Kyle Moffett <kyle@...fetthome.net>
Subject: Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)

> Quoting Michael Stone (michael@...top.org):
> > Serge Hallyn wrote:
> > >Michael, I'm sorry, I should go back and search the thread for the
> > >answer, but don't have time right now - do you really need
> > >disablenetwork to be available to unprivileged users?
> > 
> > Rainbow can only drop the networking privileges when we know at app launch time
> > (e.g. based on a manifest or from the human operator) that privileges can be
> > dropped. Unfortunately, most of the really interesting uses of disablenetwork
> > happen *after* rainbow has dropped privilege and handed control the app.
> > Therefore, having an API which can be used by at least some low-privilege
> > processes is important to me.
> > 
> > >is it ok to require CAP_SETPCAP (same thing required for dropping privs from
> > >bounding set)?
> > 
> > Let me try to restate your idea:
> > 
> >   We can make disablenetwork safer by permitting its use only where explicitly
> >   permitted by some previously privileged ancestor. The securebits facility
> >   described in
> > 
> >     http://lwn.net/Articles/280279/
> > 
> >   may be a good framework in which to implement this control.
> > 
> > Did I understand correctly? If so, then yes, this approach seems like it would
> > work for me.
> 
> That is a little more than I was saying this time though I think I
> suggested it earlier.
> 
> But really I don't think anyone would care to separate a system into
> some processes allowed to do unprivileged disablenetwork and other
> processes not allowed to, so a (root-owned mode 644) sysctl seems just
> as useful.

Global solution like that is always wrong. (And we have better
solution available.)
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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