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

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Date:	Tue, 12 Jan 2010 09:52:46 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
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>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Américo Wang <xiyou.wangcong@...il.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Samir Bellabes <sam@...ack.fr>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Pavel Machek <pavel@....cz>, 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.

> Regards, and thanks very much for your help,
> 
> Michael
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