Re: Proposal: Support custom authentication methods using hooks

Greetings,

* Jeff Davis (pgsql@j-davis.com) wrote:
> On Wed, 2022-03-16 at 11:02 -0400, Stephen Frost wrote:
> > That we're having to extend this quite a bit to work for the proposed
> > OAUTH patches and that it still doesn't do anything for the client
> > side
> > (note that the OAUTHBEARER patches are still patching libpq to add
> > support directly and surely will still be even with this latest patch
> > set ...) makes me seriously doubt that this is the right direction to
> > be
> > going in.
>
> I don't follow this concern. I assume you're referring to the last two
> bullet points, which I repeat below:
>
> * Add support for custom auth options to configure provider's
> behavior:
>
> Even without OAUTH I think this would have been requested.
> Configuration of some kind is going to be necessary. Without custom
> options, I guess the provider would need to define its own config file?
> Not the end of the world, but not ideal.

Yes, configuration of some kind will be needed and getting that
configuration correct is going to be essential to being able to have a
secure authentication system.

> > How about- if we just added OAUTH support directly into libpq and the
> > backend, would that work with Azure's OIDC provider?  If not, why
> > not?
> > If it does, then what's the justification for trying to allow custom
> > backend-only authentication methods?
>
> I understand the point, but it also has a flip side: if custom auth
> works, why do we need to block waiting for a complete core OAUTH
> feature?

First, let's be clear- we aren't actually talking about custom or
pluggable authentication here, at least when it comes to PG as a
project.  For it to actually be pluggable, it needs to be supported on
both the client side and the server side, not just the server side.

That this keeps getting swept under the carpet makes me feel like this
isn't actually an argument about the best way to move the PG project
forward but rather has another aim.  I don't think we should even
consider accepting a patch to make this something that works only on the
server side as, in such a case, we wouldn't even be able to have an
extension of our own that leverages it or tests it without bespoke code
for that purpose.  I certainly don't think we should add code to libpq
for some auth method that isn't even available in a default install of
PG, as would happen if we accepted both this patch and the patch to add
OAUTH support to libpq.  What exactly is the thinking on how this would
move forward?  We'd commit this custom support that requires an external
extension to actually work and then add hacked-in code to libpq in order
for folks to be able to use OAUTH?  What happens when, and not if,
something changes in that extension that requires a change on the client
side..?  Are we going to be dealing with CVEs for the libpq side of
this?

> Authentication seems like a good candidate for allowing custom methods.

It's not and this is clear from looking at history.  We have seen this
time and time again- PAM, SASL, RADIUS could be included, EAP, etc.
You'll note that we already support some of these, yet you'd like to now
add some set of hooks in addition to these pluggable options that
already exist because, presumably, they don't actually solve what you're
looking for.  That's actually rather typical when it comes to
authentication methods- everyone has this idea that it can be pluggable
or a few hooks to allow a custom method will work for the next great
thing, but that's not what actually happens.

> New ones are always coming along, being used in new ways, updating to
> newer crypto, or falling out of favor. We've accumulated quite a few.

I agree that we need to get rid of some of the ones that we've got, but
even so, at least the ones we have are maintained and updated to the
extent possible for us to fix issues with them.  The idea that
externally maintained custom auth methods would be taken care of in such
a way is quite far fetched in my view.

I also disagree that they're coming along so quickly and so fast that
it's actually difficult for us to include or support, we've covered
quite a few, after all, as you seem to agree with.

Thanks,

Stephen