Re: Support for NSS as a libpq TLS backend

On Mon, 2021-02-01 at 21:49 +0100, Daniel Gustafsson wrote:
> > On 29 Jan 2021, at 19:46, Jacob Champion <pchampion(at)vmware(dot)com> wrote:
> > I think the bad news is that the static approach will need support for
> > ENABLE_THREAD_SAFETY.
>
> I did some more reading today and noticed that the NSS documentation (and their
> sample code for doing crypto without TLS connections) says to use NSS_NoDB_Init
> to perform a read-only init which don't require a matching close call. Now,
> the docs aren't terribly clear and also seems to have gone offline from MDN,
> and skimming the code isn't entirelt self-explanatory, so I may well have
> missed something. The v24 patchset posted changes to this and at least passes
> tests with decent performance so it seems worth investigating.

Nice! Not having to close helps quite a bit.

(Looks like thread safety for NSS_Init was added in 3.13, so we have an
absolute version floor.)

> > (It looks like the NSS implementation of pgtls_close() needs some thread
> > support too?)
>
> Storing the context in conn would probably be better?

Agreed.

> > The good(?) news is that I don't understand why OpenSSL's
> > implementation of cryptohash doesn't _also_ need the thread-safety
> > code. (Shouldn't we need to call CRYPTO_set_locking_callback() et al
> > before using any of its cryptohash implementation?) So maybe we can
> > implement the same global setup/teardown API for OpenSSL too and not
> > have to one-off it for NSS...
>
> No idea here, wouldn't that impact pgcrypto as well in that case?

If pgcrypto is backend-only then I don't think it should need
multithreading protection; is that right?

--Jacob