add std.crypto.tls.Server

[andrewrk]

Extracted from #13980.

We already have std.crypto.tls.Client. Now it's time to additionally add a server.

Once we have both, they can be used to test each other.

[richiejp]

Is anyone currently working on this? I'd like it for an experiment, but I'm not sure how long it will take for me to implement.

[laoshaw]

I read somewhere tls.server was not the focus for stdlib as tls.client is here for package management, it will be really cool though for zig has tls.server implemented just like what golang does, so zig can be easily used for web without external dependencies.

in the meantime this looks good: https://github.com/mattnite/zig-mbedtls

[richiejp]

Yup. I did also realise that my HTTP/2 server can use h2c with a proxy that simply wraps the TCP connection in TLS with ALPN.

[laoshaw]

that's good for use cases where a zig-http(h2c) server runs behind a proxy who does the ssl termination(ALPN termination?), however zig will be used in embedded systems and typically has no proxy, the embedded device will have to deal with https directly, which is why zig-mbedtls exists I think.

[clickingbuttons]

I'm currently working on this in order to debug the TLS client.

[clickingbuttons]

Happy to report I've followed along with https://tls13.xargs.org/ (which I've used as a unit test) until the server new session tickets. The client and server can send application data messages!

I skipped cert verification and there are some memory optimizations left.

Big PR coming in the next week or two.