crypto/tls: add ConnectionState.CurveID

[FiloSottile]

Proposal Details

With #67061, the selected "CurveID" is the difference between a post-quantum connection and not. We should expose it in ConnectionState. I actually assumed we were already exposing this.

It's unfortunate to use the CurveID misnomer, but ConnectionState doesn't feel like the place to start introducing a new name, it will only cause confusion.

/cc @golang/security

[FiloSottile]

If a deprecated RSA KEX is used, CurveID will be zero.

[rsc]

This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group

[rsc]

Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group

The proposal is to add a CurveID field of type tls.CurveID to tls.ConnectionState.

[rsc]

No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group

The proposal is to add a CurveID field of type tls.CurveID to tls.ConnectionState.