Ryan Malloy
6268e6eafd
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.
coredns-rfc2136
A CoreDNS plugin that accepts RFC 2136 dynamic DNS updates (TSIG-authenticated), filling a gap in the official plugin set.
CoreDNS as-shipped has no plugin for accepting dynamic updates — its
plugin model treats authoritative data as read-only (loaded from auto,
file, secondary, etc.). This plugin adds the missing piece.
Primary use case: self-hosted ACME DNS-01
The motivating problem: automate Let's Encrypt cert issuance for many domains without depending on registrar APIs (Vultr/Route53/Cloudflare). The architecture:
_acme-challenge.example.com CNAME <uuid>.auth.supported.systems
│
│ delegated NS to your CoreDNS host
▼
CoreDNS + rfc2136 plugin
│
│ accepts TSIG UPDATEs from Caddy
│ (caddy-dns/rfc2136) or any other
│ ACME client
▼
Let's Encrypt validates
One-time per protected domain: add a CNAME glue line in your static
zones. After that, all cert issuance + renewal happens via UPDATE
messages — zero static zone-file churn.
Status
Phase 1 (skeleton): compiles, registers with CoreDNS, parses the
Corefile directive. Does not yet handle UPDATE messages or serve any
records. ServeDNS is a pass-through. See phases.md for the roadmap.
Configuration
rfc2136 <zone> [<zone>...] {
tsig-key <key-name> <algorithm> <base64-secret>
ttl <seconds>
persist <path>
}
Example:
.:53 auth.example.com {
rfc2136 auth.example.com {
tsig-key acme-key. hmac-sha256 BASE64SECRET==
ttl 60
}
errors
log
}
Building
This plugin is consumed by a custom CoreDNS build via plugin.cfg:
# In CoreDNS source's plugin.cfg, BEFORE the `cache` plugin:
rfc2136:git.supported.systems/rsp2k/coredns-rfc2136
Then go get git.supported.systems/rsp2k/coredns-rfc2136 && make.
License
MIT (TODO: add LICENSE file).