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zones: add explicit CNAME-to-apex for RFC 4592 empty-non-terminals

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Wildcards in DNS only synthesize for names that don't already exist
in the zone tree. A `_acme-challenge.<sub>` TXT record makes <sub>
an "empty non-terminal" — exists in the tree (as a parent node) but
has no records of its own. Per RFC 4592 §2.2.3, wildcards skip these,
so RFC-compliant resolvers (HE, BIND) return NODATA for <sub> even
when the zone has `* CNAME @`.

Fix: for each <sub> that's an empty non-terminal in a zone with a
wildcard, add an explicit `<sub> CNAME @` so the resolution outcome
matches what the wildcard would have produced. Zero-knowledge — no
need to identify the specific service IP per name.

30 records added across 14 zones:
  acrazy.org (langfuse.dootie)
  context.bet (studio)
  copper-springs.online (docs.butler.dev)
  demostar.io (cw.cw, doom, meet)
  home-inspector.store (api, dashboard, mailpit)
  inspect.pics (admin)
  log.doctor (app, docs)
  malloys.us (cp, cp-sandbox, mary)
  nielsen-inspections.com (calendar, cw, files, v2-calendar)
  qubeseptic.com (api.dispatch, dispatch, leads, mail.dispatch,
                  rentcache.dispatch)
  ryanmalloy.com (c4ai)
  sidejob.pro (api)
  upc.llc (catalog, minio.or, or, s3)

CoreDNS (lenient) was returning the wildcard CNAME for these names
anyway; HE (strict RFC-compliant) was returning empty. After this
change, both behave identically.
This commit is contained in:
Ryan Malloy 2026-05-18 18:34:51 -06:00
parent c19df5d0a5
commit f8363e5ea7
13 changed files with 69 additions and 13 deletions
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5
zones/context.bet.zone
View file

@ -29,4 +29,7 @@ _acme-challenge 300 IN TXT "8lJ4Ury26qHtSwLaABC9UB_ZdFja3ZmujmUg7-5Y4Bg"
_acme-challenge 300 IN TXT "FSMb7Ru6xgzIIUvlzSzzVnOsGQD2Dgxm_qhx6hyymnE"
_acme-challenge 300 IN TXT "yB9kMNkHqVDe5vMvkgN5SFxiXgDSlSyUgldfW971BXw"
_acme-challenge 300 IN TXT "dpheXmHW0vH_NW5t8Ie_OWXiJkZT0l2U2Yu9w5n5uZg"
_acme-challenge 300 IN TXT "K6DYSkbn2Fk_P0fA1fxbIZszce4NzjTtgodaUNxDS1w"
_acme-challenge 300 IN TXT "K6DYSkbn2Fk_P0fA1fxbIZszce4NzjTtgodaUNxDS1w"
; Explicit CNAMEs added to fix RFC 4592 empty-non-terminal cases
; (parent name has _acme-challenge children, so wildcard would skip it)
studio 300 IN CNAME context.bet