Re: Direct SSL connection with ALPN and HBA rules

On Mon, Apr 29, 2024 at 12:06 PM Heikki Linnakangas <hlinnaka@iki.fi> wrote:
> On 29/04/2024 21:43, Jacob Champion wrote:
> > But if you're in that situation, what does the use of directonly give
> > you over `sslnegotiation=direct`? You already know that servers
> > support direct, so there's no additional performance penalty from the
> > less strict mode.
>
> Well, by that argument we don't need requiredirect/directonly at all.
> This goes back to whether it's a security feature or a performance feature.

That's what I've been trying to argue, yeah. If it's not a security
feature... why's it there?

> There is a small benefit with sslmode=prefer if you connect to a server
> that doesn't support SSL, though. With sslnegotiation=direct, if the
> server rejects the direct SSL connection, the client will reconnect and
> try SSL with SSLRequest. The server will respond with 'N', and the
> client will proceed without encryption. sslnegotiation=directonly
> removes that SSLRequest attempt, eliminating one roundtrip.

Okay, agreed that in this case, there is a performance benefit. It's
not enough to convince me, honestly, but are there any other cases I
missed as well?

> Oh I was not aware sslrootcert=system works like that. That's a bit
> surprising, none of the other ssl-related settings imply or require that
> SSL is actually used.

For sslrootcert=system in particular, the danger of accidentally weak
sslmodes is pretty high, especially for verify-ca mode. (It goes back
to that other argument -- there should be, effectively, zero users who
both opt in to the public CA system, and are also okay with silently
falling back and not using it.)

> Did we intend to set a precedence for new settings
> with that?

(I'll let committers answer whether they intended that or not -- I was
just bringing up that we already have a setting that works like that,
and I really like how it works in practice. But it's probably
unsurprising that I like it.)

--Jacob