Restrict production wp-admin/wp-login to an IP allowlist (opt-in)

New WP_ADMIN_ALLOWED_IPS env var (space-separated CIDR ranges, matching
Caddy's remote_ip syntax directly). Defaults to 0.0.0.0/0 ::/0 (today's
open behavior) when unset, resolved at the Compose level rather than in
the Caddyfile so an unset var can never leave `remote_ip` with zero
arguments and fail Caddy's startup. admin-ajax.php stays exempt since
WooCommerce routes logged-out storefront AJAX through it. Production
only — staging is already LAN-only.

Verified live: a scratch Caddy instance on a Docker network, with a
sibling container's actual observed source IP used to prove both the
blocked (403 on wp-admin/wp-login, everything else unaffected) and
allowed (matching CIDR lets it through) cases, plus `docker compose
config` to confirm the unset-var default resolves correctly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MqhgnCRjjVLFnZ3Jpn93Vg

.env.example

@@ -61,3 +61,10 @@ MAILERLITE_API_KEY=
 # --- Hardcover (AO3-style tag browsing — genre/mood/content-warning/tag sync) ---
 # Get a token: hardcover.app account settings -> Hardcover API -> New API Key
 HARDCOVER_API_TOKEN=
+
+# --- Admin access restriction (production only) ---
+# Space-separated IPs/CIDR ranges allowed to reach /wp-admin and
+# /wp-login.php (matches Caddy's `remote_ip` syntax directly — no quotes,
+# space-separated even though most other values here are one token).
+# Leave blank to leave wp-admin reachable from anywhere (today's behavior).
+WP_ADMIN_ALLOWED_IPS=

README.md

@@ -123,6 +123,19 @@ is blocked on it. Go-live (switching the gateway from sandbox to Helcim's
 live environment) is a deliberate manual step on the settings screen, not
 something this repo automates.
 
+### Admin access restriction (production)
+
+`/wp-admin` and `/wp-login.php` can be restricted to specific IPs/CIDR
+ranges in production via `WP_ADMIN_ALLOWED_IPS` in `.env.production` —
+space-separated, matching Caddy's own `remote_ip` syntax directly (e.g.
+`203.0.113.5 198.51.100.0/24`). Leave it blank and wp-admin stays
+reachable from anywhere, same as today — this is opt-in, not on by
+default, and only applies in production (staging is already LAN-only).
+`/wp-admin/admin-ajax.php` is always exempt regardless of the IP list,
+since WordPress/WooCommerce route some logged-out storefront AJAX
+through it. Applying a changed value just needs `make deploy ENV=production`
+(or restarting the `caddy` container) — no code change required.
+
 ## Deploy pipeline
 
 The Git server (Gitea) and the staging/production Docker hosts are separate

docker-compose.production.yml

@@ -19,6 +19,12 @@ services:
       - "443:443"
     environment:
       SITE_DOMAIN: ${SITE_DOMAIN}
+      # Default keeps wp-admin open to everyone (today's behavior) when
+      # unset — resolved here, not in the Caddyfile, since Compose would
+      # otherwise pass an *empty* string rather than an unset var, and
+      # Caddy's own {$VAR:default} placeholder only applies to a var
+      # that's truly absent, not an empty one.
+      WP_ADMIN_ALLOWED_IPS: ${WP_ADMIN_ALLOWED_IPS:-0.0.0.0/0 ::/0}
     volumes:
       - ./docker/caddy/Caddyfile.production:/etc/caddy/Caddyfile:ro
       - wp_core:/var/www/html:ro

docker/caddy/Caddyfile.production

@@ -18,6 +18,19 @@
 	@dev_only path /wp-content/plugins/bookstore-core/tests/* /wp-content/plugins/bookstore-core/vendor/* /wp-content/plugins/bookstore-core/composer.json /wp-content/plugins/bookstore-core/composer.lock /wp-content/plugins/bookstore-core/phpunit.xml*
 	respond @dev_only 404
 
+	# WP_ADMIN_ALLOWED_IPS (.env.production) — defaults to 0.0.0.0/0 ::/0
+	# (unrestricted) in docker-compose.production.yml when unset. Excludes
+	# admin-ajax.php: WordPress/WooCommerce route logged-out-visitor AJAX
+	# (cart fragments, nonces, some add-to-cart flows) through that file
+	# even though it lives under /wp-admin/ — blocking it by IP would break
+	# the storefront for every visitor, not just admin access.
+	@blocked_admin {
+		path /wp-admin* /wp-login.php
+		not path /wp-admin/admin-ajax.php
+		not remote_ip {$WP_ADMIN_ALLOWED_IPS}
+	}
+	respond @blocked_admin 403
+
 	php_fastcgi wordpress:9000
 	file_server