fix(docker): make host Docker socket opt-in (#4902)

* fix(docker): make host socket compose opt-in

* fix(cookbook): gate container Docker access

* fix(docker): gate socket group setup on opt-in

* fix(cookbook): gate generated docker exec serve commands

* fix(cookbook): narrow generated docker exec forms

docker/entrypoint.sh

@@ -29,12 +29,12 @@ fi
 ODY_USER="$(getent passwd "$PUID" | cut -d: -f1)"
 [ -z "$ODY_USER" ] && ODY_USER=odysseus
 
-# Docker-socket group plumbing. When /var/run/docker.sock is bind-mounted
-# (Cookbook uses docker exec to reach sibling containers), the socket is
-# owned by root:<host docker gid>. Add the app user to that group and later
-# call gosu by username so supplementary groups are retained.
+# Docker-socket group plumbing for the explicit host-Docker overlay. When
+# opted in, the socket is owned by root:<host docker gid>. Add the app user
+# to that group and later call gosu by username so supplementary groups are
+# retained.
 DOCKER_SOCK="${DOCKER_SOCK:-/var/run/docker.sock}"
-if [ -S "$DOCKER_SOCK" ]; then
+if [ "${ODYSSEUS_ENABLE_HOST_DOCKER:-}" = "true" ] && [ -S "$DOCKER_SOCK" ]; then
     SOCK_GID="$(stat -c '%g' "$DOCKER_SOCK" 2>/dev/null || echo '')"
     if [ -n "$SOCK_GID" ] && [ "$SOCK_GID" != "0" ]; then
         if ! getent group "$SOCK_GID" >/dev/null 2>&1; then

docker/host-docker.yml

@@ -0,0 +1,12 @@
+# High-trust host Docker access. Enable only when local Docker-daemon
+# management from Cookbook is required and you accept that raw socket access
+# grants broad control over the host Docker daemon.
+#   COMPOSE_FILE=docker-compose.yml:docker/host-docker.yml
+#   DOCKER_GID=<numeric host Docker group id>
+services:
+  odysseus:
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+    group_add: ["${DOCKER_GID:-963}"]
+    environment:
+      - ODYSSEUS_ENABLE_HOST_DOCKER=true