Re: tls 1.3: sending multiple tickets

On 18/06/2024 16:11, Daniel Gustafsson wrote:
>> On 17 Jun 2024, at 19:38, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> Seems we ought to use SSL_CTX_set_num_tickets() to prevent issuing the useless
>> tickets?
>
> Agreed, in 1.1.1 and above as the API was only introduced then. LibreSSL added
> the API in 3.5.4 but only for compatibility since it doesn't support TLS
> tickets at all.

Wow, that's a bizarre API. The OpenSSL docs are not clear on what the
possible values for SSL_CTX_set_num_tickets() are. It talks about 0, and
mentions that 2 is the default, but what does it mean to set it to 1, or
5, for example?

Anyway, it's pretty clear that SSL_CTX_set_num_tickets(0) can be used to
disable tickets, so that's fine.

>> It seems like a buglet in openssl that it forces each session tickets to be
>> sent in its own packet (it does an explicit BIO_flush(), so even if we
>> buffered between openssl and OS, as I think we should, we'd still send it
>> separately), but I don't really understand most of this stuff.
>
> I don't see anything in the RFCs so not sure.
>
> The attached applies this, and I think this is backpatching material since we
> arguably fail to do what we say in the code. AFAIK we don't have a hard rule
> against backpatching changes to autoconf/meson?

Looks good to me. Backpatching autoconf/meson changes is fine, we've
done it before.

--
Heikki Linnakangas
Neon (https://neon.tech)