linux-kernel - Re: [kernel-hardening] Re: [PATCH 0/2] sysctl: allow CLONE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 26 Jan 2016 15:13:29 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Serge Hallyn <serge.hallyn@...ntu.com>
Cc:	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Richard Weinberger <richard@....at>,
	Robert Święcki <robert@...ecki.net>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	David Howells <dhowells@...hat.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [kernel-hardening] Re: [PATCH 0/2] sysctl: allow CLONE_NEWUSER to
 be disabled

On Tue, Jan 26, 2016 at 9:15 AM, Serge Hallyn <serge.hallyn@...ntu.com> wrote:
> Quoting Josh Boyer (jwboyer@...oraproject.org):
>> What you're saying is true for the "oh crap" case of a new userns
>> related CVE being found.  However, there is the case where sysadmins
>> know for a fact that a set of machines should not allow user
>> namespaces to be enabled.  Currently they have 2 choices, 1) use their
>
> Hi - can you give a specific example of this?  (Where users really should
> not be able to use them - not where they might not need them)  I think
> it'll help the discussion tremendously.  Because so far the only good
> arguments I've seen have been about actual bugs in the user namespaces,
> which would not warrant a designed-in permanent disable switch.  If
> there are good use cases where such a disable switch will always be
> needed (and compiling out can't satisfy) that'd be helpful.

My example is a machine in a colo rack serving web pages. A site gets
attacked, and www-data uses user namespaces to continue their attack
to gain root privileges.

The admin of such a machine could have disabled userns months earlier
and limited the scope of the attack.

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security