Horton

Re: Password identifiers, protocol aging and SCRAM protocol

Heikki Linnakangas <hlinnaka@iki.fi>

View thread View on postgr.es
From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Michael Paquier <michael.paquier@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, David Steele <david@pgmasters.net>, Tom Lane <tgl@sss.pgh.pa.us>, David Fetter <david@fetter.org>, Alvaro Herrera <alvherre@2ndquadrant.com>, Magnus Hagander <magnus@hagander.net>, Julian Markwort <julian.markwort@uni-muenster.de>, Stephen Frost <sfrost@snowman.net>, PostgreSQL mailing lists <pgsql-hackers@postgresql.org>, Valery Popov <v.popov@postgrespro.ru>
Date: 2016-12-09T08:11:17Z
Lists: pgsql-hackers 
Couple of things I should write down before I forget:

1. It's a bit cumbersome that the scram verifiers stored in 
pg_authid.rolpassword don't have any clear indication that they're scram 
verifiers. MD5 hashes are readily identifiable by the "md5" prefix. I 
think we should use a "scram-sha-256:" for scram verifiers.

Actually, I think it'd be awfully nice to also prefix plaintext 
passwords with "plain:", but I'm not sure it's worth breaking the 
compatibility, if there are tools out there that peek into rolpassword. 
Thoughts?

2. It's currently not possible to use the plaintext "password" 
authentication method, for a user that has a SCRAM verifier in 
rolpassword. That seems like an oversight. We can't do MD5 
authentication with a SCRAM verifier, but "password" we could.

- Heikki

Commits

  1. Support SCRAM-SHA-256 authentication (RFC 5802 and 7677).

  2. Refactor SHA2 functions and move them to src/common/.

  3. Replace isMD5() with a more future-proof way to check if pw is encrypted.

  4. Remove bogus notice that older clients might not work with MD5 passwords.

  5. Refactor the code for verifying user's password.

  6. Replace PostmasterRandom() with a stronger source, second attempt.

  7. Remove support for (insecure) crypt authentication.