Re: Password identifiers, protocol aging and SCRAM protocol

On Tue, Dec 13, 2016 at 10:43 AM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Mon, Dec 12, 2016 at 11:39 PM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>> A few couple more things that caught my eye while hacking on this:

Looking at what we have now, in the branch...

>> * Use SASLPrep for passwords.

SASLPrep is defined here:
https://tools.ietf.org/html/rfc4013
And stringprep is here:
https://tools.ietf.org/html/rfc3454
So that's roughly applying a conversion from the mapping table, taking
into account prohibited, bi-directional, mapping characters, etc. The
spec says that the password should be in unicode. But we cannot be
sure of that, right? Those mapping tables should be likely a separated
thing.. (perl has Unicode::Stringprep::Mapping for example).

>> * Check nonces, etc. to not contain invalid characters.

Fixed this one.

>> * Derive mock SCRAM verifier for non-existent users deterministically from
>> username.

You have put in place the facility to allow that. The only thing that
comes in mind to generate something per-cluster is to have
BootStrapXLOG() generate an "authentication secret identifier" with a
uint64 and add that in the control file. Using pg_backend_random()
would be a good idea here.

>> * Allow plain 'password' authentication for users with a SCRAM verifier in
>> rolpassword.

Done.

>> * Throw an error if an "authorization identity" is given. ATM, we just
>> ignore it, but seems better to reject the attempt than do something that
>> might not be what the client expects.

Done.

>> * Add "scram-sha-256" prefix to SCRAM verifiers stored in
>> pg_authid.rolpassword.

You did it.
--
Michael