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

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Date:	Thu, 17 Jun 2010 10:04:53 -0700
From:	Kees Cook <kees.cook@...onical.com>
To:	James Morris <jmorris@...ei.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, 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>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-doc@...r.kernel.org, Stephen Smalley <sds@...ho.nsa.gov>,
	Daniel J Walsh <dwalsh@...hat.com>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] ptrace: allow restriction of ptrace scope

Hi James,

On Thu, Jun 17, 2010 at 11:45:42PM +1000, James Morris wrote:
> On Wed, 16 Jun 2010, Kees Cook wrote:
> 
> [Note: it would be useful to cc: the LSM list on security discussions]

Sorry, I was blindly using get_maintainer output.

> > Certainly.  PTRACE can already be confined by SELinux and AppArmor.  I'm
> > looking for a general approach that doesn't require a system builder to
> > create MAC policies for unknown software.  I want to define a common core
> > behavior.
> > 
> > > And even if you don't care about using the same security stuff the rest
> > > of the world is using to solve the problem this like the other half baked
> > > stuff you posted for links belongs as a security module.
> > 
> > The LSM isn't stackable, so I can't put it there and choose this and
> > SELinux (for the case of software-without-a-policy).
> 
> SELinux already supports a global switch for ptrace via the allow_ptrace 
> boolean.  You don't need to write any policy, just set it to 0.
> 
> Global behavior can be further customized and refined (e.g. create a 
> generic policy module for apps without an existing policy, which allows 
> everything except things like ptrace and dangerous symlinks).
> 
> SELinux users would not need the other LSM, and stacking is thus not 
> required.

But if a user wants to disable ptrace using the SELinux LSM and then
also disable sticky-symlinks via the ItsHideous LSM, they're out of luck.

-Kees

-- 
Kees Cook
Ubuntu Security Team
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