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).