security: harden remote-access stack (pentest remediation R1-R4)

App layer (R1): bind frps NewProxy to token-owned subdomain (anti-hijack),
default-deny unknown webhook ops, HMAC-verify stripe-stub billing webhook,
enforce bandwidth quota kill-switch (Ping op), least-privilege table grants
(migrations 0002/0003), GOTRUE_PASSWORD_MIN_LENGTH=12.

Infra/net (R2): unpublish internal host ports (kong/pooler/analytics/frps-dash),
read-only docker-socket-proxy for vector (no host breakout), on-demand-TLS
allow-list authorizer, edge-block machine-only webhooks, no-new-privileges on
custom containers.

Secrets (R3): rotate Postgres password (all roles) + frps dashboard; replace
predictable supavisor defaults; secrets externalized to gitignored .env.

Med/Low (R4): security response headers (HSTS/XCTO/XFO/Referrer/Permissions/COOP),
restrict frp proxy_type to http (no open relay), disable destructive redis
commands, tighten frps.toml perms.

No secrets committed; rotated values live only in gitignored .env files.

caddy/Caddyfile

@@ -1,10 +1,27 @@
 {
 	email office@linumiq.com
 	on_demand_tls {
-		# Self-hosted ask endpoint on :9999 (always 200 in Wave A).
-		# TODO Wave B: point ask at https://api.linumiq.net/functions/v1/check-subdomain
-		# (an Edge Function that returns 200 only for subdomains present in tunnels table).
-		ask http://localhost:9999/check
+		# SECURITY (R2/F3): closed allow-list authorizer. The edge function returns
+		# 200 only for reserved hosts (apex/app/api) and subdomains registered in
+		# the tunnels table; 403 otherwise. This prevents unbounded on-demand
+		# certificate issuance for arbitrary hostnames.
+		ask http://supabase-edge-functions:9000/check-subdomain
+	}
+}
+
+# SECURITY (R4/F10/W5): baseline response-hardening headers applied to the
+# LinumIQ-controlled surfaces (apex/app/api). HSTS forces HTTPS for a year and
+# is safe for first-party hostnames we fully control.
+(security_headers) {
+	header {
+		Strict-Transport-Security "max-age=31536000; includeSubDomains; preload"
+		X-Content-Type-Options "nosniff"
+		X-Frame-Options "SAMEORIGIN"
+		Referrer-Policy "no-referrer"
+		Permissions-Policy "geolocation=(), microphone=(), camera=()"
+		Cross-Origin-Opener-Policy "same-origin"
+		-Server
+		-X-Powered-By
 	}
 }
 
@@ -13,6 +30,7 @@ linumiq.net {
 	tls {
 		on_demand
 	}
+	import security_headers
 	redir https://app.linumiq.net{uri} permanent
 }
 
@@ -21,6 +39,7 @@ app.linumiq.net {
 	tls {
 		on_demand
 	}
+	import security_headers
 	reverse_proxy web:3000
 }
 
@@ -29,18 +48,23 @@ api.linumiq.net {
 	tls {
 		on_demand
 	}
+	import security_headers
+	# SECURITY (R2): block machine-only webhook functions from the public edge.
+	# auth-webhook and stripe-webhook are invoked internally over the docker
+	# network (supabase-edge-functions:9000) and must never be callable from the
+	# internet. get-node stays public for the Home Assistant add-on.
+	@blocked_webhooks path /functions/v1/auth-webhook* /functions/v1/stripe-webhook*
+	respond @blocked_webhooks 403
 	reverse_proxy supabase-kong:8000
 }
 
 # Wildcard tunnel subdomains -> frps vhost HTTP. Per-name HTTP-01 issued on first hit.
+# NOTE: only HSTS is injected here; Home Assistant sets its own security headers
+# (X-Frame-Options, etc.) and we must not override its CSP / framing behaviour.
 *.linumiq.net {
 	tls {
 		on_demand
 	}
+	header Strict-Transport-Security "max-age=31536000; includeSubDomains"
 	reverse_proxy frps:7080
 }
-
-# Internal ask endpoint for on-demand TLS. Bound to loopback inside the container.
-http://localhost:9999 {
-	respond /check 200
-}

caddy/docker-compose.yml

@@ -3,6 +3,8 @@ services:
     image: caddy:2.10.2-alpine
     container_name: caddy
     restart: unless-stopped
+    security_opt:
+      - no-new-privileges:true
     ports:
       - "80:80"
       - "443:443"