Re: [PoC] Federated Authn/z with OAUTHBEARER

On Mon, Oct 28, 2024 at 6:24 AM Daniel Gustafsson <daniel(at)yesql(dot)se> wrote:
> > On 25 Oct 2024, at 20:22, Jacob Champion <jacob(dot)champion(at)enterprisedb(dot)com> wrote:
>
> > I have combed almost all of Daniel's feedback backwards into the main
> > patch (just the new bzero code remains, with the open question
> > upthread),
>
> Re-reading I can't see a vector there, I guess I am just scarred from what
> seemed to be harmless leaks in auth codepaths and treat every bit as
> potentially important. Feel free to drop from the patchset for now.

Okay. For authn_id specifically, which isn't secret and doesn't have
any power unless it's somehow copied into the ClientConnectionInfo,
I'm not sure that the bzero() gives us much. But I do see value in
clearing out, say, the Bearer token once we're finished with it.

Also in this validate() code path, I'm taking a look at the added
memory management with the pfree():
1. Should we add any more ceremony to the returned struct, to try to
ensure that the ABI matches? Or is it good enough to declare that
modules need to be compiled against a specific server version?
2. Should we split off a separate memory context to contain
allocations made by the validator?

> Looking more at the patchset I think we need to apply conditional compilation
> of the backend for oauth like how we do with other opt-in schemes in configure
> and meson. The attached .txt has a diff for making --with-oauth a requirement
> for compiling support into backend libpq.

Do we get the flexibility we need with that approach? With other
opt-in schemes, the backend and the frontend both need some sort of
third-party dependency, but that's not true for OAuth. I could see
some people wanting to support an offline token validator on the
server side but not wanting to build the HTTP dependency into their
clients.

I was considering going in the opposite direction: With the client
hooks, a user could plug in their own implementation without ever
having to touch the built-in flow, and I'm wondering if --with-oauth
should really just be --with-builtin-oauth or similar. Then if the
server sends OAUTHBEARER, the client only complains if it doesn't have
a flow available to use, rather than checking USE_OAUTH. This kind of
ties into the other big open question of "what do we do about users
that don't want the additional overhead of something they're not
using?"

--Jacob