Re: SCRAM authentication, take three

On Sat, Apr 8, 2017 at 1:59 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Apr 7, 2017 at 3:59 AM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>> I think the "SCRAM" part is more important than "SHA-256", so -1 on that.
>
> I agree. The point here isn't that we're using a better hashing
> method, even if a lot of people *think* that's the point. The point
> is we're using a modern algorithm that has nice properties like "you
> can't impersonate the client by steeling the verifier, or even by
> snooping the exchange".
>
> But "sasl" might be even better.

FWIW, my opinion has not changed much on the matter, I would still
favor "sasl" as the keyword used in pg_hba.conf. What has changed in
my mind though is that defining no mechanisms with an additional
option mean that all possible choices are sent to the client. But if
you define a list of mechanisms, then we'll just send back to the
client the specified list as a possible choice of exchange mechanism:
host all all blah.com sasl mechanism=scram-sha-256-plus
Here for example the user would not be allowed to use SCRAM-SHA-256,
just SCRAM with channel binding.

Such an option makes sense once we add support for one more mechanism
in SASL, like channel binding, but that's by far a generic approach
that can serve us for years to come, and by admitting that nothing
listed means all possible options we don't need any immediate action.
--
Michael