Re: [secdir] secdir review of draft-ietf-httpbis-tunnel-protocol-04

Martin Thomson <martin.thomson@gmail.com> Wed, 10 June 2015 20:02 UTC

Return-Path: <martin.thomson@gmail.com>
X-Original-To: secdir@ietfa.amsl.com
Delivered-To: secdir@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 71A8A1A8AB3; Wed, 10 Jun 2015 13:02:31 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Level:
X-Spam-Status: No, score=-2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, SPF_PASS=-0.001] autolearn=ham
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id GX74P-4lpMOF; Wed, 10 Jun 2015 13:02:27 -0700 (PDT)
Received: from mail-yk0-x236.google.com (mail-yk0-x236.google.com [IPv6:2607:f8b0:4002:c07::236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 53E941A8AAC; Wed, 10 Jun 2015 13:02:27 -0700 (PDT)
Received: by ykaz81 with SMTP id z81so1212200yka.3; Wed, 10 Jun 2015 13:02:26 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=ES8HFFcox31RxvNJDxItqooBajunakrztMOIlFT3Nd4=; b=ZoRw/5AjAauye6KR4nZGu1SMLbfbfX+qtifl7b6j4OWI3OGZXxsyWs/98xKL49/wMc z+nGQpJLeGF8LTocaoClEeIAK6TkzHAzKgERIcEYFtxBqS7pslQGxdEixNhQVJT/7pDV iJbUz7pL1jixo2xT2IKksCIWmWolT2KGSojArbC/za5Hi542Umt+hS512dvj0euv+oAK q8i3jjSGA80+6YV7794D5Ml1EBk4966ZakVBRV0jP32zo6aI18DnBMnH8LA4oOsIqLnP HaTyf4MDxJBvuA5yja3uUNOLe7wm1HKUU2mRUC1s4aJkLU60atvWumyI1DhBEVtFNURA /sqg==
MIME-Version: 1.0
X-Received: by 10.129.93.136 with SMTP id r130mr1901303ywb.52.1433966545309; Wed, 10 Jun 2015 13:02:25 -0700 (PDT)
Received: by 10.129.110.138 with HTTP; Wed, 10 Jun 2015 13:02:25 -0700 (PDT)
In-Reply-To: <93D1B0AD-7CA0-4143-9687-A9CE05170120@hyperthought.com>
References: <DA0CCE5D-D67A-4AD0-8DCB-87F0F397D342@hyperthought.com> <CABkgnnUPmUQq6VaCKWu8=yZUABScbzTfoNQMwrg-Nr511R-XRQ@mail.gmail.com> <93D1B0AD-7CA0-4143-9687-A9CE05170120@hyperthought.com>
Date: Wed, 10 Jun 2015 13:02:25 -0700
Message-ID: <CABkgnnXeZpzxpQwzxrTpJJMcaWFdhh6zxNBEdFnwssychNX2Lg@mail.gmail.com>
From: Martin Thomson <martin.thomson@gmail.com>
To: Scott Kelly <scott@hyperthought.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Archived-At: <http://mailarchive.ietf.org/arch/msg/secdir/HLobglA2mCMNfIwngeLvYHoFNNE>
Cc: draft-ietf-httpbis-tunnel-protocol.all@tools.ietf.org, The IESG <iesg@ietf.org>, "secdir@ietf.org" <secdir@ietf.org>
Subject: Re: [secdir] secdir review of draft-ietf-httpbis-tunnel-protocol-04
X-BeenThere: secdir@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: Security Area Directorate <secdir.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/secdir>, <mailto:secdir-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/secdir/>
List-Post: <mailto:secdir@ietf.org>
List-Help: <mailto:secdir-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/secdir>, <mailto:secdir-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 10 Jun 2015 20:02:31 -0000

On 10 June 2015 at 12:09, Scott Kelly <scott@hyperthought.com>; wrote:
>
> +          A proxy can use the value of the ALPN header field as input to
> +          authorization decisions.  The header field exposes protocol
> +          information at the HTTP layer, allowing authorization decisions to be
> +          made earlier, with better error reporting (such as a 403 status code).
>
> The term “authorization” evokes notions of security, at least for me. This text gives me the impression that the ALPN header is suitable for use in security decisions.
>
> I can think of a couple of ways to address this. One easy way is to replace “authorization” with something more security-neutral (“filtering”? “allow/deny”?). Another is to simply add a statement saying this header may be falsified by either the client or a MitM, and therefore should not be relied upon for security-relevant decisions unless additional security measures are applied.


Would it make more sense like this?

          A proxy can use the value of the ALPN header field to more cleanly and
          efficiently reject requests for a CONNECT tunnel.  Exposing protocol
          information at the HTTP layer allows a proxy to deny requests earlier,
          with better error reporting (such as a 403 status code).  The ALPN
          header field can be falsified and is therefore not sufficient basis
          for authorizing a request.