Re: [TLS] Double-Checking after TLS 1.3 pre-RFC copy edits

[Hubert Kario <[e-mail]>]

On Saturday, 28 July 2018 01:20:43 CEST Eric Rescorla wrote:
> Dear TLS WG members.
> 
> I am doing my final copy-edits for the TLS 1.3 RFC and I noted one
> technical point and two points I would like to edit for clarity but I
> wanted more eyes on.
> 
> 
> 1. https://tools.ietf.org/html/draft-ietf-tls-tls13-28#section-4.1.2
> 
>       If the client is attempting a PSK key
>       establishment, it SHOULD advertise at least one cipher suite
>       indicating a Hash associated with the PSK.
> 
> This seems like it would be better as a MUST. It's not a disaster
> if we don't change it, but can anyone think of a reason it should
> be a SHOULD?

It can be a MUST, but then we need to add a MUST for a server not to 
overinterpret lack of them (as in MUST NOT abort) - client may send a PSK 
associated with a hash in a ciphersuite that the server does not know

-- 
Regards,
Hubert Kario
Senior Quality Engineer, QE BaseOS Security team
Web: www.cz.redhat.com
Red Hat Czech s.r.o., Purkyňova 115, 612 00  Brno, Czech Republic