Re: [Last-Call] [DNSOP] Secdir last call review of draft-ietf-dnsop-server-cookies-04

Willem Toorop <willem@nlnetlabs.nl> Wed, 02 December 2020 22:07 UTC

Return-Path: <willem@nlnetlabs.nl>
X-Original-To: last-call@ietfa.amsl.com
Delivered-To: last-call@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 1949B3A1574; Wed, 2 Dec 2020 14:07:50 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.1
X-Spam-Level:
X-Spam-Status: No, score=-2.1 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=nlnetlabs.nl
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 Q7x2Ex7apzYE; Wed, 2 Dec 2020 14:07:48 -0800 (PST)
Received: from outbound.soverin.net (outbound.soverin.net [IPv6:2a01:4f8:fff0:2d:8::218]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id D0E343A1570; Wed, 2 Dec 2020 14:07:47 -0800 (PST)
Received: from smtp.soverin.net (unknown [10.10.3.24]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by outbound.soverin.net (Postfix) with ESMTPS id B2D0760805; Wed, 2 Dec 2020 22:07:45 +0000 (UTC)
Received: from smtp.soverin.net (smtp.soverin.net [159.69.232.138]) by soverin.net
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=nlnetlabs.nl; s=soverin; t=1606946864; bh=qXZHLfxefBQdvVHHYh5Z+23RI4ERIw2OgA08IMz0Y5s=; h=To:Cc:References:From:Subject:Date:In-Reply-To:From; b=sWV5r69GNQOZBxKm1qkjfjOZmGAPJsvfbKioBd7uKT99g43WkVzGZ/xq4yBF5nOKU TuHRJOAZRW3P7dQtYycik7kaKtN5D1nauaDqpKGZeQapakkf2+7jGsd+7v1OYIkdcc Cw8BJPRVNaY7pP/K4KTN5h2DvHK3wGm4x4IjwVIKY1Pfx9OItC4PhSB/9gF6ja81B1 EKJ2BP9tyWHZ7YI0RZkhWtsNN0mQb16QiZ5euNWZj6U3+xyK4YcGl6AG97L2Q+uGud AqNDviXiGgoew4uQ2usmdGFfdnUAt5hJKZtBop8pX1VfR7WyUvJ28t5e64aPpHR+pc 3YHiu7qpbUe3Q==
To: Stephen Farrell <stephen.farrell@cs.tcd.ie>, Ondřej Sur ý <ondrej@isc.org>
Cc: last-call@ietf.org, draft-ietf-dnsop-server-cookies.all@ietf.org, dnsop@ietf.org, secdir@ietf.org
References: <160693121881.9413.5642470305677631145@ietfa.amsl.com> <17AFD6F5-11DA-41BC-8C37-E1893648041D@isc.org> <75c266ba-573a-29e3-621d-aea9b27f195f@cs.tcd.ie> <b23d3f2b-4b4f-f70c-ff53-cbd2c229a887@nlnetlabs.nl> <d263c879-6c85-fbc3-3484-02402b1c52aa@cs.tcd.ie>
From: Willem Toorop <willem@nlnetlabs.nl>
Message-ID: <9a15fe4b-7850-3558-78d8-7ad7f90fd97d@nlnetlabs.nl>
Date: Wed, 02 Dec 2020 23:07:40 +0100
MIME-Version: 1.0
In-Reply-To: <d263c879-6c85-fbc3-3484-02402b1c52aa@cs.tcd.ie>
Content-Type: text/plain; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/last-call/80ykQ_6rUp4vpyRbg9YRVHtAtpY>
Subject: Re: [Last-Call] [DNSOP] Secdir last call review of draft-ietf-dnsop-server-cookies-04
X-BeenThere: last-call@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: IETF Last Calls <last-call.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/last-call>, <mailto:last-call-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/last-call/>
List-Post: <mailto:last-call@ietf.org>
List-Help: <mailto:last-call-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/last-call>, <mailto:last-call-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 02 Dec 2020 22:07:50 -0000


Op 02-12-2020 om 22:49 schreef Stephen Farrell:
> 
> Hiya,
> 
> On 02/12/2020 21:38, Willem Toorop wrote:
>> Op 02-12-2020 om 21:37 schreef Stephen Farrell:
>>
>> <snip>
>>
>>>> ad 2) we need a value that’s synchronized well enough and monotonic.
>>>> I honestly don’t see any value in using 64-bit value here. Using
>>>> unixtime has a value in itself, it’s a well-known and there’s a
>>>> little room for any implementer to make a mistake in an
>>>> implementation. The interoperability is more important than the
>>>> actual value of the counter. It’s write only counter, nobody is going
>>>> to interpret it after it has been generated, and it’s wide enough to
>>>> prevent brute forcing.
>>>
>>> So what happens after 2038? That's really not v. far in the
>>> future any more.
>>
>> The draft states that `All comparisons involving these fields MUST
>> use "Serial number arithmetic", as defined in [RFC1982]'. So it can not
>> be used to compare differences larger than 68 years, but comparisons of
>> cookie timestamps are more in the "hours" order of magnitude.
> 
> Sorry for being dim, but is clear what value to put
> in those 4 octets in say 2039 such that different
> implementations will do the right thing
Well the text does specify an "32-bit unsigned number of seconds elapsed
since 1 January 1970 00:00:00 UTC", so because of the "unsigned" the
wrap to 0 is only in 2106, not 2038.

But even then, in 2106, it should not be a problem to check the age of a
cookie because of the rfc1982 comparison (which takes care of the wrap)
and the fact that Server Cookies will not be older than hours (and not
years).

Cheers,
-- Willem

> I did glance
> at rfc1982, so there may be very far-sighted text
> in there that I missed:-) And it may even be fine
> for this purpose if different servers differ by a
> second or so at that point, but even if so, it may
> be a bad plan to leave that unspecified in case
> other timestamps use the same code.
> 
> Cheers,
> S.
> 
>>
>> Cheers,
>> -- Willem
>>
>>>
>>> Cheers,
>>> S.
>>>
>>>>
>>>> Cheers, Ondřej -- Ondřej Surý — ISC (He/Him)
>>>>
>>>>> On 2. 12. 2020, at 18:47, Stephen Farrell via Datatracker
>>>>> <noreply@ietf.org> wrote:
>>>>>
>>>>> Reviewer: Stephen Farrell Review result: Has Issues
>>>>>
>>>>> I see two issues here worth checking:
>>>>>
>>>>> 1. I don't recall SipHash being used as a MAC in any IETF standard
>>>>> before. We normally use HMAC, even if truncated. Why make this
>>>>> change and was that checked with e.g. CFRG? (And the URL given in
>>>>> the reference gets me a 404.)
>>>>>
>>>>> 2. Is it really a good idea to use a 32 bit seconds since
>>>>> 1970-01-01 in 2020? I'd have thought that e.g. a timestamp in hours
>>>>> since then or seconds since some date in 2020 would be better.
>>>>>
>>>>> Here's a couple of nits too: - section 1: what's a "strong
>>>>> cookie"? - "gallimaufry" - cute! but not sure it'll help readers to
>>>>> learn that word.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> _______________________________________________ DNSOP mailing list
>>>> DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
>>>>
>>>
>>> _______________________________________________
>>> DNSOP mailing list
>>> DNSOP@ietf.org
>>> https://www.ietf.org/mailman/listinfo/dnsop
>>>
>>
>> _______________________________________________
>> DNSOP mailing list
>> DNSOP@ietf.org
>> https://www.ietf.org/mailman/listinfo/dnsop
>>