coredns: DoT (:853) + DoH (:443) listeners with self-signed cert

- New Corefile snippet (common) shared across plain DNS / DoT / DoH so
  zone-loading + forward + cache stay DRY across all three transports
- scripts/generate-certs.sh: openssl-only self-signed RSA cert with SANs
  for localhost / 127.0.0.1 / ::1 / coredns / dns.local. Idempotent —
  skips regeneration if cert is valid >24h ahead; FORCE=1 to rotate.
- Key chmod is 0644 so the CoreDNS container's nonroot user can read it
  via the bind mount. Acceptable for local dev; production should mount
  real certs with proper UID/GID.
- DOT_PORT=8853, DOH_PORT=8443 (avoids Caddy already-on-443 collision)
- Makefile: `make certs`, `make test-tls`
- All three transports verified end-to-end (dig +tls, dig +https,
  curl with raw RFC 8484 wire format)

.env

@@ -8,3 +8,11 @@ COREDNS_IMAGE=coredns/coredns:1.11.3
 DNS_PORT=1053
 METRICS_PORT=9153
 HEALTH_PORT=8080
+
+# DoT (DNS-over-TLS, RFC 7858) — IANA port 853. Host port 8853 to
+# stay unprivileged.
+DOT_PORT=8853
+
+# DoH (DNS-over-HTTPS, RFC 8484) — typically 443. Host port 8443
+# because Caddy already owns 443 on this host.
+DOH_PORT=8443

.gitignore

@@ -1,5 +1,8 @@
 # Prepared zones are generated from zones/ by scripts/prepare-zones.sh
 zones-prepared/*.zone
 
+# Self-signed certs (re-generated by scripts/generate-certs.sh)
+certs/*.pem
+
 # Local-only env overrides
 .env.local

Corefile

@@ -1,25 +1,37 @@
-. {
+# Shared zone-loading + recursive-forwarding config.
-    # Authoritative: load every <zone>.zone in /zones via the auto plugin.
+# CoreDNS snippets are textually expanded by `import`, so we keep anything
-    # Filename pattern (.*)\.zone yields the zone name from the first group.
+# that's not transport-specific (TLS) in here.
-    # CoreDNS reloads modified files every 30s.
+(common) {
     auto {
         directory /zones (.*)\.zone {1}
         reload 30s
     }
-
-    # Anything not authoritative falls through to upstream resolvers.
     forward . 1.1.1.1 1.0.0.1 9.9.9.9 {
         max_concurrent 1000
     }
-
-    # In-memory cache (TTL clamp 30s for both pos/neg).
     cache 30
-
-    # Operational plugins
-    health :8080
-    prometheus :9153
     errors
     log
     loop
     reload 10s
 }
+
+# Plain DNS — UDP/TCP :53. Health + metrics live here only (one binding).
+. {
+    import common
+    health :8080
+    prometheus :9153
+}
+
+# DNS-over-TLS — RFC 7858. Port 853 is the IANA-assigned DoT port.
+tls://.:853 {
+    tls /etc/coredns/certs/cert.pem /etc/coredns/certs/key.pem
+    import common
+}
+
+# DNS-over-HTTPS — RFC 8484. Default path is /dns-query.
+# Clients: curl -H 'accept: application/dns-message' https://host:8443/dns-query?dns=...
+https://.:443 {
+    tls /etc/coredns/certs/cert.pem /etc/coredns/certs/key.pem
+    import common
+}

Makefile

@@ -2,7 +2,7 @@
 SHELL := /usr/bin/env bash
 COMPOSE := docker compose
 
-.PHONY: help prep up down restart logs ps test reload clean
+.PHONY: help prep certs up down restart logs ps test test-tls reload clean
 
 help: ## Show this help
 	@awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_-]+:.*?## / {printf "  \033[36m%-12s\033[0m %s\n", $$1, $$2}' $(MAKEFILE_LIST)
@@ -10,7 +10,10 @@ help: ## Show this help
 prep: ## Re-inject SOA records into all zones (writes zones-prepared/)
 	@./scripts/prepare-zones.sh
 
-up: prep ## Start CoreDNS (prepares zones first)
+certs: ## Generate self-signed cert for DoT/DoH (re-run with FORCE=1 to rotate)
+	@./scripts/generate-certs.sh
+
+up: prep certs ## Start CoreDNS (prepares zones + ensures certs exist first)
 	$(COMPOSE) up -d
 	@sleep 2 && $(COMPOSE) logs --tail=20 coredns
 
@@ -29,11 +32,28 @@ logs: ## Tail CoreDNS logs
 ps: ## Show container status
 	$(COMPOSE) ps
 
-test: ## Smoke-test against a known zone (uses DNS_PORT from .env)
+test: ## Smoke-test plain DNS (uses DNS_PORT from .env)
-	@. ./.env && echo "Querying acrazy.org @ 127.0.0.1:$$DNS_PORT" && \
+	@. ./.env && echo "Querying acrazy.org @ 127.0.0.1:$$DNS_PORT (plain DNS)" && \
 		dig @127.0.0.1 -p $$DNS_PORT acrazy.org SOA +short && \
 		dig @127.0.0.1 -p $$DNS_PORT acrazy.org NS +short && \
 		dig @127.0.0.1 -p $$DNS_PORT or.acrazy.org A +short
 
-clean: down ## Remove containers + prepared zones
+test-tls: ## Smoke-test DoT + DoH (pins self-signed cert via +tls-ca)
-	rm -rf zones-prepared/*.zone
+	@. ./.env && \
+		echo "=== DoT @ 127.0.0.1:$$DOT_PORT ===" && \
+		dig @127.0.0.1 -p $$DOT_PORT +tls +tls-ca=certs/cert.pem \
+			+tls-hostname=localhost acrazy.org SOA +short && \
+		echo "" && \
+		echo "=== DoH @ https://localhost:$$DOH_PORT/dns-query ===" && \
+		dig @localhost -p $$DOH_PORT +https +tls-ca=certs/cert.pem \
+			acrazy.org A +short && \
+		echo "" && \
+		echo "=== DoH via curl (raw wire-format) ===" && \
+		curl -sk --cacert certs/cert.pem \
+			-H 'accept: application/dns-message' \
+			--data-binary @<(printf '\x00\x00\x01\x20\x00\x01\x00\x00\x00\x00\x00\x00\x06acrazy\x03org\x00\x00\x01\x00\x01') \
+			-H 'content-type: application/dns-message' \
+			"https://localhost:$$DOH_PORT/dns-query" | xxd | head -5
+
+clean: down ## Remove containers + prepared zones + certs
+	rm -rf zones-prepared/*.zone certs/*.pem

docker-compose.yml

@@ -7,11 +7,14 @@ services:
     ports:
       - "${DNS_PORT}:53/udp"
       - "${DNS_PORT}:53/tcp"
+      - "${DOT_PORT}:853/tcp"
+      - "${DOH_PORT}:443/tcp"
       - "${METRICS_PORT}:9153/tcp"
       - "${HEALTH_PORT}:8080/tcp"
     volumes:
       - ./Corefile:/etc/coredns/Corefile:ro
       - ./zones-prepared:/zones:ro
+      - ./certs:/etc/coredns/certs:ro
     healthcheck:
       test: ["CMD", "wget", "-qO-", "http://127.0.0.1:8080/health"]
       interval: 30s

scripts/generate-certs.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+# Generate a self-signed RSA cert for CoreDNS DoT/DoH (local dev only).
+# Production deployments should mount real Let's Encrypt certs (e.g. from
+# Caddy's shared volume) into certs/ instead.
+#
+# SANs cover the names a local resolver client is likely to use:
+#   - localhost (loopback by name)
+#   - 127.0.0.1 / ::1 (loopback by IP)
+#   - coredns (docker container DNS name)
+#   - dns.local (convenient pinning hostname)
+set -euo pipefail
+
+CERT_DIR="${CERT_DIR:-certs}"
+DAYS="${DAYS:-825}"   # 825 is the historical macOS/Apple cap; safe ceiling
+
+mkdir -p "$CERT_DIR"
+
+if [[ -f "$CERT_DIR/cert.pem" && -f "$CERT_DIR/key.pem" ]]; then
+  # Skip regeneration if not expired and re-prep was not forced.
+  if [[ "${FORCE:-0}" != "1" ]]; then
+    # openssl returns 0 if cert is valid beyond the given window (24h here).
+    if openssl x509 -checkend 86400 -noout -in "$CERT_DIR/cert.pem" >/dev/null 2>&1; then
+      echo "Cert at $CERT_DIR/cert.pem still valid (>24h). Set FORCE=1 to regenerate."
+      exit 0
+    fi
+  fi
+fi
+
+# Single-shot self-signed cert with SANs. -addext requires openssl >= 1.1.1.
+openssl req -x509 -newkey rsa:2048 -nodes -days "$DAYS" \
+  -keyout "$CERT_DIR/key.pem" \
+  -out "$CERT_DIR/cert.pem" \
+  -subj "/CN=coredns-local" \
+  -addext "subjectAltName=DNS:localhost,DNS:coredns,DNS:dns.local,IP:127.0.0.1,IP:::1" \
+  >/dev/null 2>&1
+
+# 0644 (not 0600) on the key so the CoreDNS container's `nonroot` user
+# can read it via the bind mount. Acceptable for a local-dev self-signed
+# cert whose private key never leaves this directory. For production
+# certs, mount with explicit UID/GID via :ro,uid=65532 or use a tmpfs/
+# secret instead.
+chmod 644 "$CERT_DIR/key.pem"
+chmod 644 "$CERT_DIR/cert.pem"
+
+echo "Generated $CERT_DIR/{cert,key}.pem  (valid ${DAYS} days)"
+openssl x509 -in "$CERT_DIR/cert.pem" -noout -subject -issuer -dates \
+  -ext subjectAltName 2>&1 | sed 's/^/  /'