GeezerVison

tls: enable hybrid post-quantum key exchange (X25519MLKEM768)

The Data Plane API's HTTPS listener pins CurvePreferences to P-256 only (server.go:227). The comment there — "only use curves which have assembly implementations" — predates Go's post-quantum support: since Go 1.24, an explicit curve list without X25519MLKEM768 opts the server out of the hybrid post-quantum key exchange it would otherwise have by default. Since the Data Plane API often runs long-lived on infrastructure hosts, its admin traffic is the kind of thing "harvest now, decrypt later" collection targets. This change re-enables the hybrid group, additively — P-256 stays, and the classical-fallback handshake below demonstrates compatibility with classical-only peers.

This PR was generated by crypt 0.0.1-dev and verified before it was opened — every gate below ran against this branch's code. Machine-checked: this change touches exactly what it claims. An independent checker (sharing no code with the rewriter) compared the pre- and post-change syntax trees and confirmed the delta is precisely the edits listed below — no other declaration differs. An explicit CurvePreferences list without X25519MLKEM768 silently disables post-quantum key exchange in Go ≥ 1.24; this change re-enables it, preferred first. The change is additive: all previously accepted curves remain (crypt hard rule: rewrites never remove a working path), and compatibility is demonstrated against the tested classical-only peer below. One known ecosystem caveat: a larger ClientHello can trip fragmentation-buggy middleboxes on some network paths — Go documents GODEBUG=tlsmlkem=0 as the operator escape if that occurs.

Changes

• server.go:227 — []tls.CurveID{tls.CurveP256} → []tls.CurveID{tls.X25519MLKEM768, tls.CurveP256}

Evidence

evidence bundle: crypt-evidence.json · templates T1-tls-curvepreferences-x25519mlkem768 · generated 2026-10-24T15:54:00Z