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

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Date:	Fri, 18 Jun 2010 23:19:53 -0400
From:	fche@...hat.com (Frank Ch. Eigler)
To:	Kees Cook <kees.cook@...onical.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Randy Dunlap <rdunlap@...otime.net>,
	James Morris <jmorris@...ei.org>, linux-kernel@...r.kernel.org,
	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, systemtap@...rceware.org
Subject: Re: [PATCH] ptrace: allow restriction of ptrace scope

Kees Cook <kees.cook@...onical.com> writes:

> [...]  At present, I'm aware of global PTRACE control being possible
> in SELinux, AppArmor, grsecurity, and as a patch in Ubuntu's kernel.
> I don't know about TOMOYO or Smack, but configuring the default
> scope of PTRACE in at least 4 different ways so far (or not being
> able to change it at all) just seems crazy. [...]

For the curious, below is a demonstration an interactive systemtap
script that can implement this sort of local policy, independently of
the other security APIs.

http://sourceware.org/systemtap/examples/keyword-index.html#SECURITY

just a user         sammy sysadmin
===========         ==============

8232% echo $$
8232

                    root# noptrace.stp -x 8232 &

8232% do-stuff &
[1] 8888
                    root# cat /proc/systemtap/stap_*/blocked
                    8232 /bin/bash
                    8888 /usr/local/bin/do-stuff

8232% strace ls
strace: ptrace(PTRACE_TRACEME, ...): No such process
8232% gdb do-stuff 8888
Attaching to program: /usr/local/bin/do-stuff, process 8888
ptrace: No such process.

                    root# echo 8232 > /proc/systemtap/stap_*/unblock

8232% strace ls
[...working again...]


- FChE
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