Horton

Re: SCRAM with channel binding downgrade attack

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Magnus Hagander <magnus@hagander.net>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Michael Paquier <michael@paquier.xyz>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Stephen Frost <sfrost@snowman.net>
Date: 2018-05-23T22:41:16Z
Lists: pgsql-hackers 
On Wed, May 23, 2018 at 11:15:28AM +0200, Magnus Hagander wrote:
> On Wed, May 23, 2018 at 11:08 AM, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>     SCRAM, even without channel binding, does prove that you're talking to the
>     correct server. Or to be precise, it proves to the client, that the server
>     also knows the password, so assuming that you're using strong passwords and
>     not sharing them across servers, you know that you're talking to the
>     correct server.
> 
> Right. It provides a very different guarantee from what ssl certs provide. They
> are not replaceable, or mutually exclusive. Trying to force those into a single
> configuration parameter doesn't make a lot of sense IMO.

True.  sslmode is checking the the SSL endpoint with which you have a
shared secret has access to the private key of a server certificate that
is signed by a trusted CA, and perhaps the certificate's subject name
also matches the hostname.

With channel binding, you are proving that the SSL endpoint with which
you have a shared secret has access to the user password hash.

I can imagine someone wanting both checks so merging them into a single
options seems unwise, as Magnus mentioned.

-- 
  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.