Re: WIP: SCRAM authentication

On Tue, Aug 4, 2015 at 4:20 PM, Michael Paquier wrote:
> I have been looking more in depths at this one, which adds essential
> infrastructure to support multiple authentication hashes for more protocols.
> Here are some comments:
> [spec lines]
> I am willing to write a patch for the next CF following more or less those
> lines, depending of course on the outcome of the discussion we can have
> here, so feel free to comment.

OK, attached as 0001 is the patch that respects those lines for the
support of multiple password verifiers in system catalogs. I have
added a new catalog called pg_auth_verifiers that is used at
authentication to fetch a password value depending on the protocol
used. With only this patch attached there are two types of verifiers:
plain and md5. This new catalog is REVOKE'd like pg_authid (pg_authid
could be made readable be this seems sensitive to me so I am not
changing it).

I have as well done the following things:
- Added PASSWORD VERIFIER (md5 = 'hoge', plain = 'hoge') which is used
as well by pg_dump all to be able to specify password verifiers one by
one.
- password check hook has been reworked as mentioned to be able to
manage a list of password verifiers instead of a single entry.
contrib/passwordcheck has been updated as well.
- Added regression tests testing UNENCRYPTED/ENCRYPTED, PASSWORD
VERIFIER, PASSWORD, etc.
- The patch does not break backward compatibility regarding CREATE
ROLE and ALTER ROLE.
- password_encryption has been changed to a list with comma-separated
elements, for now the possible elements are 'md5' and 'plain'. This
breaks backward compatibility, so if we care about it we should
consider having a new GUC password_encryption_list or similar. Default
is md5, default that does not change backward compatibility.
- Added documentation.
- pg_shadow has been updated, switching to an array with
method:password as elements.

> I'll have a look more in-depth at the scram patch as well.

The SCRAM patch (0002~0004) has been rebased to use the new facility.
I have as well fixed a syscache leak... But I haven't been able to
enter much in the details yet.

The patch 0001 to add the multiple verifier facility is in a state
good enough to get some review, so I am registering an entry for it in
the next CF. And I'll continue the work on the SCRAM portion next
week, with hopefully a version ready for CF submission.
Regards,
-- 
Michael