From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>,
Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
Florian Westphal <fw@strlen.de>,
NetFilter <netfilter-devel@vger.kernel.org>,
coreteam@netfilter.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
info@jablonka.cz, eric@regit.org
Subject: Re: [RFC PATCH 0/2] restore original default of nf_conntrack_helper sysctl
Date: Tue, 24 Jan 2017 02:28:59 +0100 [thread overview]
Message-ID: <20170124012859.GA6375@salvia> (raw)
In-Reply-To: <CA+55aFyDbDxcT+OjcxLxJ87MsFgNi0WWNoBSzZvWgA+yuQSXkg@mail.gmail.com>
On Mon, Jan 23, 2017 at 05:09:55PM -0800, Linus Torvalds wrote:
> On Mon, Jan 23, 2017 at 4:06 PM, Jiri Kosina <jikos@kernel.org> wrote:
> >
> > Considering this being really close to the "userspace breakage"
> > borderline, I'm CCing Linus as well.
>
> For all I know, there may be some security reason why we really don't
> want the automatic helpers, even if they can be convenient.
Yes, with helper modules in place, this is known to allow attackers to
push holes in your firewall. Eric Leblond actually show that it's
perfectly feasible to exploit this via handcrafted packets [1]. The
problem is documented here [2].
> Also, you can just enable them with a kernel command line or a sysctl,
> so it's not like you can't get the old behavior back.
Right.
[1] https://cansecwest.com/csw12/conntrack-attack.pdf
[2] https://home.regit.org/netfilter-en/secure-use-of-helpers/
next prev parent reply other threads:[~2017-01-24 1:29 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-24 0:06 [RFC PATCH 0/2] restore original default of nf_conntrack_helper sysctl Jiri Kosina
2017-01-24 1:09 ` Linus Torvalds
2017-01-24 1:28 ` Pablo Neira Ayuso [this message]
2017-01-24 7:40 ` [PATCH] netfilter: nf_ct_helper: warn when not applying default helper assignment (was Re: [RFC PATCH 0/2] restore original default of nf_conntrack_helper sysctl) Jiri Kosina
2017-01-24 10:17 ` [PATCH v2] netfilter: nf_ct_helper: warn when not applying default helper assignment Jiri Kosina
2017-01-25 19:13 ` Linus Torvalds
2017-01-25 20:43 ` Jiri Kosina
2017-01-26 5:40 ` Joe Perches
2017-02-01 16:27 ` Pablo Neira Ayuso
2017-02-01 19:43 ` Jiri Kosina
2017-02-01 20:01 ` [PATCH v3] " Jiri Kosina
2017-02-02 13:26 ` Pablo Neira Ayuso
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