Re: [secdir] Security review of draft-ietf-rtcweb-fec-08 (was Re: Security review of draft-ietf-perc-srtp-ekt-diet-08)

Justin Uberti <justin@uberti.name> Sat, 09 February 2019 01:51 UTC

Return-Path: <juberti@gmail.com>
X-Original-To: secdir@ietfa.amsl.com
Delivered-To: secdir@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id DD4E91310C4; Fri, 8 Feb 2019 17:51:48 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.879
X-Spam-Level:
X-Spam-Status: No, score=-1.879 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, FREEMAIL_FORGED_FROMDOMAIN=0.018, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
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 L--6Vn0yGZDS; Fri, 8 Feb 2019 17:51:46 -0800 (PST)
Received: from mail-lj1-f173.google.com (mail-lj1-f173.google.com [209.85.208.173]) (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 EF0861310C1; Fri, 8 Feb 2019 17:51:45 -0800 (PST)
Received: by mail-lj1-f173.google.com with SMTP id t9-v6so4557959ljh.6; Fri, 08 Feb 2019 17:51:45 -0800 (PST)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=gVyCToMRsWFVhW59F189oc2ugbAAEp3+NGa3Eab/9pU=; b=TlFVx8pxNJHxoPpV7DlcbLTcsn/9IBThL1QTQ6As7svvgUwrrbe09LgnPfqt55FBi6 I88mftMEvRfGPLENV76akO2rWtFuEzLM3OrbHdY/pMBA0OkgsWns9z+GyBiQhKe+3j0G 8kWkIdOn7VWmVyN6/w3PbT/OVu5BlFBkcksQ5AvfdGBdcCMok2jilvMMkmzX1mnc/fEn ZYDhXmHdU96Vbe8gTVeM61hrGywgri7V1YP+MNXNWo7hULJI46fKRPIgZfkj4sDZfA+p 2gK3u2dOVB2aCs5uaf7dkAt15y2a2UNUvupI3LQbL3tjO5Fstgwj1Y99FlqrYgLpYGBP NnBA==
X-Gm-Message-State: AHQUAuaoXwGf9j1hiKMK1yFmp8Fr64AxIEw7YCGTWBlZY/jGkBje7WZj wvO+AwxdJmHI7BpAn4xintV7q+BGljn5M51PwEc=
X-Google-Smtp-Source: AHgI3Ibf7w6IM8PsMUIRS+dkHjZvO8I4aATdVVlRb4Zk1griIN0sGd7tOrXyVrvvHxSF1/acOmbNvasygqKI7BuyEvw=
X-Received: by 2002:a2e:884b:: with SMTP id z11-v6mr8411201ljj.68.1549677103839; Fri, 08 Feb 2019 17:51:43 -0800 (PST)
MIME-Version: 1.0
References: <201902010742.x117gdGm030846@rumpleteazer.rhmr.com> <F44FA6A0-4599-4BFF-8BEB-C67774714762@nostrum.com> <CALe60zD=OeTfjof3Q5UqnJRHsAQC-kS1oZYaQZ5HahAVOJgVKQ@mail.gmail.com> <240284129.169422738.1549676775109.JavaMail.zimbra@purplestreak.com>
In-Reply-To: <240284129.169422738.1549676775109.JavaMail.zimbra@purplestreak.com>
From: Justin Uberti <justin@uberti.name>
Date: Fri, 08 Feb 2019 17:51:32 -0800
Message-ID: <CALe60zA6qwLLHpHHDp4Y5_PAX-wfBUmqw3gd5OWGx0zFJ57tvw@mail.gmail.com>
To: Hilarie Orman <hilarie@purplestreak.com>
Cc: Ben Campbell <ben@nostrum.com>, The IESG <iesg@ietf.org>, secdir@ietf.org, draft-ietf-rtcweb-fec all <draft-ietf-rtcweb-fec.all@tools.ietf.org>
Content-Type: multipart/alternative; boundary="0000000000004a7e4c05816c51ab"
Archived-At: <https://mailarchive.ietf.org/arch/msg/secdir/XMnaD0PVxVVqh1ZTR3WsfUcoEK0>
Subject: Re: [secdir] Security review of draft-ietf-rtcweb-fec-08 (was Re: Security review of draft-ietf-perc-srtp-ekt-diet-08)
X-BeenThere: secdir@ietf.org
X-Mailman-Version: 2.1.29
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: <https://mailarchive.ietf.org/arch/browse/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: Sat, 09 Feb 2019 01:51:49 -0000

Any suggestions on the sort of text you would like to see?

e.g. "In the WebRTC context, FEC is specifically concerned with recovering
data from lost packets; any corrupted packets will be discarded by the SRTP
decryption process. Therefore, as described in [RFC3711], Section 10..."

On Fri, Feb 8, 2019 at 5:46 PM Hilarie Orman <hilarie@purplestreak.com>
wrote:

> I think that the purpose of the FEC should be explicit, else the
> interaction with
> encryption will remain a source of confusion forever.
>
> Hilarie
>
> ----- Original Message -----
> From: Justin Uberti <justin@uberti.name>
> To: Ben Campbell <ben@nostrum.com>
> Cc: Hilarie Orman <hilarie@purplestreak.com>, The IESG <iesg@ietf.org>,
> secdir@ietf.org, draft-ietf-rtcweb-fec all <
> draft-ietf-rtcweb-fec.all@tools.ietf.org>
> Sent: Fri, 08 Feb 2019 18:20:41 -0700 (MST)
> Subject: Re: Security review of draft-ietf-rtcweb-fec-08 (was Re: Security
> review of draft-ietf-perc-srtp-ekt-diet-08)
>
> On Fri, Feb 1, 2019 at 2:49 PM Ben Campbell <ben@nostrum.com> wrote:
>
> > Hi,
> >
> > Please note that this review is for draft-ietf-rtcweb-fec-08, not the
> PERC
> > draft referenced in the subject.
> >
> > Thanks!
> >
> > Ben.
> >
> >
> > > On Feb 1, 2019, at 1:42 AM, Hilarie Orman <hilarie@purplestreak.com>
> > wrote:
> > >
> > > Security Review of WebRTC Forward Error Correction Requirements
> > > draft-ietf-rtcweb-fec-08
> > >
> > > Do not be alarmed.  I have reviewed this document as part of the
> > > security directorate's ongoing effort to review all IETF documents
> > > being processed by the IESG.  These comments were written primarily
> > > for the benefit of the security area directors.  Document editors and
> > > WG chairs should treat these comments just like any other last call
> > > comments.
> > >
> > > The document describes the appropriate uses of FEC for web content when
> > > using WebRTC.  It also describes how to indicate that FEC is being
> used.
> > >
> > > The Security Considerations mention the possibility of additional
> network
> > > congestion when using FEC.  Although this can be a problem, I do not
> > think
> > > it is a security issue, thus it does not belong in this section.
> >
>
> Understood. I think this paragraph could easily be moved to the preceding
> section.
>
> > >
> > > There is a security-related issue wrt to FEC and encryption.  If the
> > > error model is that message blocks may be lost but not altered in
> > > transit, then FEC with encryption is fine.  But if FEC is added for
> > > the purpose of correcting corrupted bits in a message block, then it
> > > is important that FEC is done after encryption.  The draft seems to
> > > ignore the issue, and it also seems to recommend a processing scheme
> > > that would result in encryption of the FEC data.  If there is a body
> > > of practice for other IETF FEC protocols that explains these issues,
> > > an explicit reference to it in the Security Considerations would be
> > > very helpful.
> >
> > FEC is added specifically to protect against lost blocks. Any corruption
> of the blocks will be detected by the decryption procedure, and such blocks
> will be discarded.
>
> There is a reference to RFC 3711, which stipulates the fec-then-encrypt
> ordering. RFC 3711 is admittedly terse on this subject, but it is quite
> clear about the ordering.
>
>