linux-kernel - Re: [PATCH] ptrace: allow restriction of ptrace scope

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Date:	Thu, 17 Jun 2010 14:14:41 -0700
From:	Kees Cook <kees.cook@...onical.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	linux-kernel@...r.kernel.org, Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Dave Young <hidave.darkstar@...il.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Roland McGrath <roland@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Howells <dhowells@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-doc@...r.kernel.org,
	Linux Containers <containers@...ts.osdl.org>,
	"Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [PATCH] ptrace: allow restriction of ptrace scope

On Thu, Jun 17, 2010 at 01:45:02PM -0700, Eric W. Biederman wrote:
> Kees Cook <kees.cook@...onical.com> writes:
> > On Thu, Jun 17, 2010 at 05:29:53AM -0700, Eric W. Biederman wrote:
> >> Kees Cook <kees.cook@...onical.com> writes:
> >> > running state of any of their processes. For example, if one application
> >> > (e.g. Pidgin) was compromised, it would be possible for an attacker to
> >> > attach to other running processes (e.g. Firefox, SSH sessions, GPG agent,
> >> > etc) to extract additional credentials and continue to expand the scope
> >> > of their attack without resorting to user-assisted phishing.
> >> 
> >> This is ineffective.  As an attacker after I gain access to a users
> >> system on ubuntu I can wait around until a package gets an update,
> >> and then run sudo and gain the power to do whatever I want.
> >
> > I doesn't stop phishing, correct.  But it does stop immediate expansion of
> > an attack using already-existing credentials.
> 
> sudo last I checked caches your password for a couple of seconds.
> So if you can probe the system to see when those couple of seconds
> are.

Sure, that's a downside of sudo, which is why privilege elevation has been
tending to move towards PolicyKit, FWIW.

> The archives of the containers list.
> https://lists.linux-foundation.org/pipermail/containers/ or just
> looking.

I'll go dig around.

>   Things like /proc/sys/ will be default stay in the same user_namespace
>   and root in other user namespaces will only get world permissions when
>   accessing files.

Excellent.  I'll move my questions about this to the containers mailing
list.

-Kees

-- 
Kees Cook
Ubuntu Security Team
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