From: Andy Lutomirski <luto@amacapital.net>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kees Cook" <keescook@chromium.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Richard Weinberger" <richard@nod.at>,
"Robert Święcki" <robert@swiecki.net>,
"Dmitry Vyukov" <dvyukov@google.com>,
"David Howells" <dhowells@redhat.com>,
"Miklos Szeredi" <mszeredi@suse.cz>,
"Kostya Serebryany" <kcc@google.com>,
"Alexander Potapenko" <glider@google.com>,
"Eric Dumazet" <edumazet@google.com>,
"Sasha Levin" <sasha.levin@oracle.com>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH 0/2] sysctl: allow CLONE_NEWUSER to be disabled
Date: Sun, 24 Jan 2016 14:22:19 -0800 [thread overview]
Message-ID: <CALCETrWYRvqhyCwx5RX6L3TEYCfW0j6ThFUc+ASL7BpxgO5dEQ@mail.gmail.com> (raw)
In-Reply-To: <8737tp0zhr.fsf@x220.int.ebiederm.org>
On Fri, Jan 22, 2016 at 7:02 PM, Eric W. Biederman
<ebiederm@xmission.com> wrote:
> Kees Cook <keescook@chromium.org> writes:
>
>> There continues to be unexpected side-effects and security exposures
>> via CLONE_NEWUSER. For many end-users running distro kernels with
>> CONFIG_USER_NS enabled, there is no way to disable this feature when
>> desired. As such, this creates a sysctl to restrict CLONE_NEWUSER so
>> admins not running containers or Chrome can avoid the risks of this
>> feature.
>
> I don't actually think there do continue to be unexpected side-effects
> and security exposures with CLONE_NEWUSER. It takes a while for all of
> the fixes to trickle out to distros. At most what I have seen recently
> are problems with other kernel interfaces being amplified with user
> namespaces. AKA the current mess with devpts, and the unexpected
> issues with bind mounts in mount namespaces.
>
>
> So to keep this productive. Please tell me about the threat model
> you envision, and how you envision knobs in the kernel being used to
> counter those threats.
I consider the ability to use CLONE_NEWUSER to acquire CAP_NET_ADMIN
over /any/ network namespace and to thus access the network
configuration API to be a huge risk. For example, unprivileged users
can program iptables. I'll eat my hat if there are no privilege
escalations in there. (They can't request module loading, but still.)
--Andy
next prev parent reply other threads:[~2016-01-24 22:22 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-22 22:39 [PATCH 0/2] sysctl: allow CLONE_NEWUSER to be disabled Kees Cook
2016-01-22 22:39 ` [PATCH 1/2] sysctl: expand use of proc_dointvec_minmax_sysadmin Kees Cook
2016-01-23 3:10 ` Eric W. Biederman
2016-01-23 22:25 ` [kernel-hardening] " Jann Horn
2016-01-24 1:20 ` Eric W. Biederman
2016-01-24 1:43 ` Al Viro
2016-01-24 1:56 ` Jann Horn
2016-01-24 6:02 ` Eric W. Biederman
2016-01-24 6:32 ` Jann Horn
2016-01-24 6:44 ` Eric W. Biederman
2016-01-22 22:39 ` [PATCH 2/2] sysctl: allow CLONE_NEWUSER to be disabled Kees Cook
2016-01-22 22:47 ` Robert Święcki
2016-01-22 22:50 ` Kees Cook
2016-01-22 22:55 ` Robert Święcki
2016-01-22 23:00 ` Kees Cook
2016-01-23 0:44 ` Serge Hallyn
2016-01-23 0:44 ` Serge Hallyn
2016-01-23 0:59 ` [kernel-hardening] " Ben Hutchings
2016-01-24 20:59 ` Kees Cook
2016-01-24 22:20 ` Andy Lutomirski
2016-01-25 18:51 ` Kees Cook
2016-01-22 22:49 ` [PATCH 0/2] " Richard Weinberger
2016-01-23 3:02 ` Eric W. Biederman
2016-01-24 20:57 ` Kees Cook
2016-01-26 7:38 ` [kernel-hardening] " Serge Hallyn
2016-01-24 22:22 ` Andy Lutomirski [this message]
2016-01-25 18:51 ` Kees Cook
2016-01-25 18:53 ` Andy Lutomirski
2016-01-25 18:56 ` Kees Cook
2016-01-25 19:33 ` Eric W. Biederman
2016-01-25 22:34 ` Kees Cook
2016-01-25 23:33 ` Andy Lutomirski
2016-01-26 2:27 ` [kernel-hardening] " Daniel Micay
2016-01-26 4:57 ` Eric W. Biederman
2016-01-26 14:38 ` Josh Boyer
2016-01-26 14:46 ` Austin S. Hemmelgarn
2016-01-26 14:56 ` Josh Boyer
2016-01-26 17:20 ` [kernel-hardening] " Serge Hallyn
2016-01-26 19:56 ` Josh Boyer
2016-01-26 20:11 ` Austin S. Hemmelgarn
2016-01-26 17:15 ` Serge Hallyn
2016-01-26 18:09 ` Austin S. Hemmelgarn
2016-01-26 18:27 ` Andy Lutomirski
2016-01-26 18:45 ` Austin S. Hemmelgarn
2016-01-26 23:15 ` Kees Cook
2016-01-26 23:13 ` Kees Cook
2016-01-27 10:27 ` Eric W. Biederman
2016-01-27 12:32 ` Austin S. Hemmelgarn
2016-01-28 14:41 ` Robert Święcki
2016-01-26 16:37 ` Kees Cook
2016-01-28 8:56 ` [kernel-hardening] " Serge E. Hallyn
2016-01-28 12:53 ` Austin S. Hemmelgarn
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