Date: Wed, 18 Jan 2017 05:23:56 +0000
From: Noah Misch <noah@leadboat.com>
To: Michael Paquier <michael.paquier@gmail.com>
Cc: Victor Wagner <vitus@wagner.pp.ru>,
	PostgreSQL mailing lists <pgsql-hackers@postgresql.org>,
	peter.eisentraut@2ndquadrant.com
Subject: Re: Password identifiers, protocol aging and SCRAM protocol
Message-ID: <20170118052356.GA5952@gust>
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On Tue, Nov 15, 2016 at 07:52:06AM +0900, Michael Paquier wrote:
> On Sat, Nov 5, 2016 at 9:36 PM, Michael Paquier <michael.paquier@gmail.com> wrote:
> > On Sat, Nov 5, 2016 at 12:58 AM, Peter Eisentraut <peter.eisentraut@2ndquadrant.com> wrote:
> > pg_hba.conf uses "scram" as keyword, but scram refers to a family of
> > authentication methods. There is as well SCRAM-SHA-1, SCRAM-SHA-256
> > (what this patch does). Hence wouldn't it make sense to use
> > scram_sha256 in pg_hba.conf instead? If for example in the future
> > there is a SHA-512 version of SCRAM we could switch easily to that and
> > define scram_sha512.
> 
> OK, I have added more docs regarding the use of scram in pg_hba.conf,
> particularly in client-auth.sgml to describe what scram is better than
> md5 in terms of protection, and also completed the data of pg_hba.conf
> about the new keyword used in it.

The latest versions document this precisely, but I agree with Peter's concern
about plain "scram".  Suppose it's 2025 and PostgreSQL support SASL mechanisms
OAUTHBEARER, SCRAM-SHA-256, SCRAM-SHA-256-PLUS, and SCRAM-SHA3-512.  What
should the pg_hba.conf options look like at that time?  I don't think having a
single "scram" option fits in such a world.  I see two strategies that fit:

1. Single "sasl" option, with a GUC, similar to ssl_ciphers, controlling the
   mechanisms to offer.
2. Separate options "scram_sha_256", "scram_sha3_512", "oauthbearer", etc.


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