On Thu, May 17, 2018 at 2:56 AM, Michael Paquier <michael@paquier.xyz> wrote:
On Wed, May 16, 2018 at 08:20:49PM -0400, Bruce Momjian wrote: > SCRAM-with-binding is the first password method that attempts to avoid > man-in-the-middle attacks, and therefore is much less likely to be able > to trust what the endpoints supports. I think it is really the > channel_binding_mode that we want to control at the client. The lesser > modes are much more reasonable to use an automatic best-supported > negotiation, which is what we do now.
Noted. Which means that the parameter is ignored when using a non-SSL connection, as well as when the server tries to enforce the use of anything else than SCRAM.
(apologies if this was covered earlier, as I'm entering late into the discussion)
"ignored" in combination with a security parameter is generally a very very red flag.
If the client requests channel binding and ends up using a non encrypted connection, surely the correct thing to do is fail the connection, rather than downgrade the authentication?
We should really make sure we don't re-implement something as silly as our current "sslmode=prefer", because it makes no sense. From the client side perspective, there really only needs to be two choices -- "enforce channel binding at level <x>" or "meh, I don't care". In the "meh, I don't care" mode, go with whatever the server picks (through enforcement in pg_hba.conf for example).
> FYI, I think the server could also require channel binding for SCRAM. We > already have scram-sha-256 in pg_hba.conf, and I think > scram-sha-256-plus would be reasonable.
Noted as well. There is of course the question of v10 libpq versions which don't support channel binding, but if an admin is willing to set up scram-sha-256-plus in pg_hba.conf then he can request his users to update his drivers/libs as well.
Yes. And they *should* fail if they don't upgrade. That's what requirement means... :)
What's the take of others? Magnus, Stephen or Heikki perhaps (you've been the most involved with SCRAM early talks)?
Saw it by luck. It would probably be better if it wasn't hidden deep in a thread about release notes.
