Re: Add "password_protocol" connection parameter to libpq

On Wed, 2019-08-21 at 16:12 +0900, Michael Paquier wrote:
> This counts for other auth requests as well like krb5, no?  I think
> that we should also add the "disable" flavor for symmetry, and
> also...

Added "disable" option, and I refactored so that it would look
explicitly for an expected auth req based on the connection parameters.

I had to also make the client tell the server that it does not support
channel binding if channel_binding=disable, otherwise the server
complains.

> +#define DefaultChannelBinding  "prefer"
> If the build of Postgres does not support SSL (USE_SSL is not
> defined), I think that DefaultChannelBinding should be "disable".
> That would make things consistent with sslmode.

Done.

> Doing the filtering at the time of AUTH_REQ_OK is necessary for
> "trust", but shouldn't this be done as well earlier for other request
> types?  This could save round-trips to the server if we know that an
> exchange begins with a protocol which will never satisfy this
> request, saving efforts for a client doomed to fail after the first
> AUTH_REQ received.  That would be the case for all AUTH_REQ, except
> the SASL ones and of course AUTH_REQ_OK.

Done.

> 
> Could you please add negative tests in
> src/test/authentication/?  What
> could be covered there is that the case where "prefer" (and
> "disable"?) is defined then the authentication is able to go through,
> and that with "require" we get a proper failure as SSL is not used.
> Tests in src/test/ssl/ could include:
> - Make sure that "require" works properly.
> - Test after "disable".

Done.

> +               if (conn->channel_binding[0] == 'r')
> Maybe this should comment that this means "require", in a fashion
> similar to what is done when checking conn->sslmode.

Done.

New patch attached.

Regards,
	Jeff Davis