Production hardening II Phase 4 — wire RFC 7232 conditional-request
support into GetDERCRL so CDNs and reverse proxies in front of certctl
can serve repeated CRL fetches from edge caches. Saves bandwidth +
removes the per-request DB read on the certctl side when a relying
party honors max-age.
ETag: weak form (W/) per RFC 7232 §2.3 wrapping the first 16 bytes
of SHA-256(DER) — sufficient ID space for the cache layer + leaves
headroom for a future builder that might emit signature randomness
that doesn't change the CRL semantics.
If-None-Match: when the inbound header matches the computed ETag,
short-circuit to 304 Not Modified with no body. Identical inbound
ETag → identical CRL → no need to retransmit the bytes.
Cache-Control: public, max-age=3600, must-revalidate. The 1h max-age
matches the default CRL regen cadence; relying parties that cache
won't re-fetch within the window. must-revalidate forces revalidation
once the window expires (so a stale relying party doesn't keep
returning expired-cache CRLs after the regen tick).
The pre-existing Cache-Control: max-age=3600 is preserved
syntactically (the new line replaces it with the more complete form);
existing relying parties see the same ceiling, just with the addition
of public + must-revalidate hints for downstream caches.
Pre-commit verification: go build ./... clean; go test -short
-count=1 green for handler/. The existing TestGetDERCRL_* tests still
pass — the new headers are additive, the response body is unchanged.
shankar0123
db854ecc6f