Re: [TLS] WGLC for draft-ietf-tls-ticketrequests

Daniel Migault <mglt.ietf@gmail.com> Mon, 03 February 2020 23:54 UTC

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From: Daniel Migault <mglt.ietf@gmail.com>
Date: Mon, 3 Feb 2020 18:54:37 -0500
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To: Eric Rescorla <ekr@rtfm.com>
Cc: Rob Sayre <sayrer@gmail.com>, "<tls@ietf.org>" <tls@ietf.org>, Daniel Migault <daniel.migault=40ericsson.com@dmarc.ietf.org>
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Subject: Re: [TLS] WGLC for draft-ietf-tls-ticketrequests
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C.4 is clearly in a context where privacy is needed and by writing "SHOULD
NOT" TLS 1.3 takes instead the position there are some cases this is not
required.

"""

C.4 <https://tools.ietf.org/html/rfc8446#appendix-C.4>.  Client
Tracking Prevention

   Clients SHOULD NOT reuse a ticket for multiple connections.  Reuse of
   a ticket allows passive observers to correlate different connections.
   Servers that issue tickets SHOULD offer at least as many tickets as
   the number of connections that a client might use; for example, a web
   browser using HTTP/1.1 [RFC7230
<https://tools.ietf.org/html/rfc7230>] might open six connections to a
   server.  Servers SHOULD issue new tickets with every connection.
   This ensures that clients are always able to use a new ticket when

   creating a new connection.
"""

On Mon, Feb 3, 2020 at 12:02 AM Eric Rescorla <ekr@rtfm.com> wrote:

>
>
> On Sun, Feb 2, 2020 at 7:40 PM Rob Sayre <sayrer@gmail.com> wrote:
>
>> On Sun, Feb 2, 2020 at 11:52 AM Daniel Migault <daniel.migault=
>> 40ericsson.com@dmarc.ietf.org> wrote:
>>
>>>
>>> On Sun, Feb 2, 2020 at 12:09 PM Eric Rescorla <ekr@rtfm.com> wrote:
>>>
>>>>
>>>>
>>>> 1. TLS 1.3 takes the position that reuse is bad and that position
>>>>    is for good reasons, so we shouldn't undercut it in a new
>>>>    extension.
>>>>
>>>>
>>
>>> . Appendix C.4 discourages tickets re-use when Client tracking is a
>>> concern. The section uses SHOULD and not MUST. So, in fact, TLS 1.3 takes
>>> position this is not mandatory to renew tickets.
>>>
>>
> Somehow I didn't get Daniel's email, so responding to it here.
>
> C.4 is not conditional. It simply says "Clients SHOULD NOT reuse a ticket
> for multiple connections." My point is not that servers which do not renew
> are not compliant but rather that TLS 1.3 has taken the position that reuse
> is bad and therefore we should not add an extension to facilitate it.
>
> -Ekr
>
>
>> thanks,
>> Rob
>>
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-- 
Daniel Migault
Ericsson