Horton

Re: Postgres 11 release notes

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Michael Paquier <michael@paquier.xyz>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-05-17T00:20:49Z
Lists: pgsql-hackers 
On Wed, May 16, 2018 at 08:59:23PM +0900, Michael Paquier wrote:
> On Wed, May 16, 2018 at 01:09:07PM +0300, Heikki Linnakangas wrote:
> > I have to agree with Bruce, that it's pretty useless to implement channel
> > binding, if there is no way to require it in libpq. IMHO that must be
> > fixed.
> 
> Wouldn't we want to also do something for the case where a client is
> willing to use SCRAM but that the server forces back MD5?  In which
> case, one possibility is a connection parameter like the following,
> named say authmethod:
> - An empty value is equivalent to the current behavior, and is the
> default.
> - 'scram' means that client is willing to use SCRAM, which would cause a
> failure if server attempts to enforce MD5.
> - 'scram-plus' means that client enforces SCRAM and channel binding.
> 
> Or we could just have a channel_binding_mode, which has a "require"
> value like sslmode, and "prefer" mode, which is the default and the
> current behavior...  Still what to do with MD5 requests in this case?

Just to reiterate, MD5 and SCRAM-less-binding is designed to avoid
packet _replay_.  It assumes no man-in-the-middle has adjusted what is
supported by the two endpoints.

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.

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.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +

Commits

  1. doc: update PG 11 release notes

  2. Fix misspelled pg_trgm contrib name in PostgreSQL 11 release notes

  3. Doc: clarify release note text about v11's new window function features.

  4. Improve wording of release notes item

  5. Fix typos in release notes

  6. Doc: preliminary list of PG11 major features.

  7. Make numeric power() handle NaNs according to the modern POSIX spec.

  8. Various improvements of skipping index scan during vacuum technics

  9. Revert back-branch changes in power()'s behavior for NaN inputs.

  10. Avoid wrong results for power() with NaN input on more platforms.

  11. Avoid wrong results for power() with NaN input on some platforms.

  12. Skip full index scan during cleanup of B-tree indexes when possible

  13. Rewrite the code that applies scan/join targets to paths.

  14. Postpone generate_gather_paths for topmost scan/join rel.

  15. Add casts from jsonb

  16. Make plpgsql use its DTYPE_REC code paths for composite-type variables.

  17. Don't allow VACUUM VERBOSE ANALYZE VERBOSE.

  18. Pass InitPlan values to workers via Gather (Merge).

  19. Account for the effect of lossy pages when costing bitmap scans.

  20. Allow no-op GiST support functions to be omitted.

  21. Rearm statement_timeout after each executed query.

  22. Push limit through subqueries to underlying sort, where possible.