When a request arrives with TSIG, attach a TSIG record to the response
so dns.ResponseWriter computes the MAC at write time using the secret
in TsigSecret. Without this, BIND nsupdate complains "expected a TSIG
or SIG(0)" on every UPDATE, even when the update applies successfully.
Two response paths fixed:
- handleUpdate success/per-rcode replies (update.go)
- ServeDNS rejection when TSIG verification fails (plugin.go)
The new helper in tsig.go is a no-op for unsigned requests. Unknown
keys still silently skip signing — we can't authenticate to a peer we
don't share a key with.
Tests verify both branches: signed request → response carries matching
TSIG (key name + algorithm); unsigned request → response stays plain.
Major architectural pivot per the user's "RFC 2136 mechanism for the
existing zonefiles, not a new in-memory thing" framing. The plugin no
longer maintains its own in-memory state OR serves any queries -- both
of those are now the auto plugin's job, reading the same zone files.
The plugin's sole responsibility is now: receive TSIG-authed UPDATE
messages, edit the matching zones/<zone>.zone file, bump the SOA
serial in CalVer (YYYYMMDDNN) form, and optionally auto-commit to git.
What changed:
- DELETED: store.go (in-memory recordStore), store_test.go (12 tests),
plugin_test.go (10 ServeDNS query tests), old update_test.go.
- NEW: zonefile.go -- file-backed authority for one zone. loadRRs via
miekg/dns zone parser; mutation helpers (lookupIn/nameExistsIn/
removeRRsetFrom/removeRRFrom/removeNameFrom/addRRTo) on []dns.RR
slices; bumpSerial with CalVer semantics + NN exhaustion handling;
writeAtomic via temp-file rename; commit shells to `git add && git
commit` with configurable author.
- NEW: zonefile_test.go -- 17 tests covering load/lookup/mutate/bump/
write paths.
- REWRITTEN: plugin.go -- ServeDNS is now thin: UPDATE → TSIG → handler;
everything else → Next. No synthetic SOA/NS, no query serving.
- REWRITTEN: update.go -- handleUpdate now opens the zoneFile, loads,
applies (with prereq checks against the loaded RRs), bumps serial,
writes, commits. Detects no-op updates to avoid spurious file writes.
- REWRITTEN: setup.go -- new directives: `zones-dir` (required),
`auto-commit` (default true), `git-author <name> <email>`. Dropped
`nameserver` and `persist`. Validates each declared zone has a file
on disk via os.Stat before CoreDNS finishes starting.
- REWRITTEN: setup_test.go -- 17 cases for the new grammar.
- REWRITTEN: update_test.go -- 11 cases using real temp zone files
via t.TempDir().
Total: 30 tests passing, 0 failures.
Next: Phase 2c (custom CoreDNS image, deploy, smoke test with nsupdate).
Replaces the Phase-1.3 refuseUpdate() stub with a real RFC 2136 handler.
Caddy via caddy-dns/rfc2136 can now inject and remove records.
UPDATE message handling (update.go):
- Zone section validation: must be exactly one SOA-typed record naming
a zone we're authoritative for. Returns FORMERR/NOTAUTH otherwise.
- Prerequisites (§3.2): name-exists, RRset-exists, name-NOT-exists,
RRset-NOT-exists semantics implemented. First failure short-circuits
with the spec's rcode (NXDOMAIN/NXRRSET/YXDOMAIN/YXRRSET).
- Updates (§3.4.2): add RR, delete RRset (CLASS=ANY+RDLEN=0), delete
all RRsets at name (CLASS=ANY+TYPE=ANY), delete specific RR (CLASS=
NONE).
- Apex SOA/NS protected: synthetic and cannot be added or removed via
UPDATE. Apex wipe (TYPE=ANY at apex) also refused.
- Default TTL applied to incoming records with TTL=0.
TSIG (tsig.go + setup.go):
- setup() now populates dnsserver.Config.TsigSecret so the underlying
dns.Server auto-verifies signatures via miekg/dns.
- checkTSIG() in ServeDNS gates UPDATEs: rejects if no TSIG, unknown
key name, algorithm-downgrade attempt, or w.TsigStatus() != nil.
- No TSIG keys configured → all UPDATEs refused (safety default).
- Algorithm pinning prevents downgrade attacks (e.g. forced HMAC-MD5).
Tests (update_test.go): 11 new cases covering happy paths and every
error rcode. Total: 35 top-level test passes, 0 failures.
ServeDNS dispatch now calls handleUpdate after auth gate. The
refuseUpdate() stub is gone. UPDATE end-to-end via nsupdate requires
the custom CoreDNS image (Phase 2) to verify TSIG plumbing on the
dns.Server side.
