fleet-manager: point acme DNS-01 propagation check at a public resolver

Split-horizon DNS made lego's propagation check query the container's internal
resolver, which doesn't serve the public _acme-challenge TXT record, so the
challenge timed out. Add ACME_RESOLVERS (comma-separated host:port, default
8.8.8.8:53) → one --dns.resolvers flag each. Documented in .env + DEPLOY.md.

serving/fleet-manager/.env.example

@@ -31,6 +31,10 @@ AWS_REGION=us-east-1
 # Optional but recommended: pin the Route 53 zone. Skips ListHostedZonesByName
 # (so you can drop it from the IAM policy) and disambiguates public/private zones.
 AWS_HOSTED_ZONE_ID=
+# Public resolver(s) for the DNS-01 propagation check (comma-separated host:port).
+# Needed because internal/split-horizon DNS won't resolve the public challenge
+# record. Defaults to Google DNS; override if 8.8.8.8 is blocked (e.g. 1.1.1.1:53).
+ACME_RESOLVERS=8.8.8.8:53
 # ACME_STAGING=1   # uncomment for a dry-run vs LE staging (UNTRUSTED certs, no rate limit)
 
 # --- agent plane (gRPC + mTLS, fleet CA) ---------------------------------------

serving/fleet-manager/DEPLOY.md

@@ -151,6 +151,12 @@ A publicly-trusted cert also keeps the WebAuthn secure-context clean (no browser
 warnings). The side-car keeps renewing on its 12-hour loop; the manager reloads
 each new cert automatically.
 
+> **Split-horizon DNS:** the side-car defaults `ACME_RESOLVERS=8.8.8.8:53` so
+> lego checks TXT propagation against **public** DNS. Without it, lego uses the
+> container's internal resolver, which doesn't serve the public
+> `_acme-challenge` record, and the challenge times out. Override if 8.8.8.8 is
+> blocked (e.g. `1.1.1.1:53`, comma-separated for several).
+
 > **Origin match:** the cert CN/SAN (`FLEET_MGR_RP_ID`) must equal the origin the
 > browser uses *and* `FLEET_MGR_RP_ORIGIN` — passkeys are origin-bound. The admin
 > listener binds loopback (`127.0.0.1:9500`) by default; expose it as

serving/fleet-manager/acme/renew-loop.sh

@@ -32,6 +32,17 @@ LEGO=$(command -v lego 2>/dev/null || true)
 [ -z "$LEGO" ] && [ -x /lego ] && LEGO=/lego
 [ -z "$LEGO" ] && { echo "acme: FATAL lego binary not found (looked on PATH and /lego)"; exit 1; }
 
+# Force the DNS-01 propagation check against a PUBLIC resolver — the container's
+# internal/split-horizon DNS doesn't serve the public _acme-challenge record, so
+# lego's default (system resolver) never sees the TXT and times out. Accepts a
+# comma-separated list of host:port; each becomes a --dns.resolvers flag.
+RESOLVERS=""
+if [ -n "${ACME_RESOLVERS:-}" ]; then
+  OLDIFS=$IFS; IFS=','
+  for r in $ACME_RESOLVERS; do RESOLVERS="$RESOLVERS --dns.resolvers $r"; done
+  IFS=$OLDIFS
+fi
+
 while true; do
   # First pass issues; later passes renew when near expiry.
   if [ -f "/le/certificates/$DOMAIN.crt" ]; then
@@ -41,9 +52,9 @@ while true; do
   fi
   echo "acme: lego $* for $DOMAIN (Route 53 DNS-01)"
 
-  # shellcheck disable=SC2086  # $STAGING is intentionally two words when set
+  # shellcheck disable=SC2086  # $STAGING/$RESOLVERS intentionally word-split
   if "$LEGO" --accept-tos --email "$EMAIL" --dns route53 --domains "$DOMAIN" \
-          --path /le $STAGING "$@"; then
+          --path /le $RESOLVERS $STAGING "$@"; then
     install -m 644 "/le/certificates/$DOMAIN.crt" /out/fullchain.pem
     install -m 600 "/le/certificates/$DOMAIN.key" /out/privkey.pem
     chown "$UID_OUT:$UID_OUT" /out/fullchain.pem /out/privkey.pem 2>/dev/null \

serving/fleet-manager/docker-compose.yml

@@ -125,6 +125,9 @@ services:
       ACME_DOMAIN: "${FLEET_MGR_RP_ID:?set FLEET_MGR_RP_ID in .env}"  # = the UI hostname
       ACME_EMAIL: "${ACME_EMAIL:?set ACME_EMAIL in .env}"
       ACME_STAGING: "${ACME_STAGING:-}"                               # set 1 for a dry-run
+      # Public resolver(s) for the propagation check — the internal/split-horizon
+      # DNS doesn't serve the public _acme-challenge record. Comma-separated host:port.
+      ACME_RESOLVERS: "${ACME_RESOLVERS:-8.8.8.8:53}"
       # AWS creds for the Route 53 DNS-01 challenge (or omit + use an instance role).
       AWS_ACCESS_KEY_ID: "${AWS_ACCESS_KEY_ID:-}"
       AWS_SECRET_ACCESS_KEY: "${AWS_SECRET_ACCESS_KEY:-}"