Container security hardening (phase 3, breaking) (#24081)

* Run the frigate service as the frigate user

* Run go2rtc as its own restricted user

* Run nginx as the frigate user with writable state in /tmp/nginx

* Disable bandwidth stats gracefully when not running as root

* Hand TensorRT model cache ownership to the runtime user

* Document non-root operation and per-hardware device access

* Create /media/frigate after the ownership sweep

* Assert non-root services, JWT migration, and escape hatch in CI

* only write the sweep sentinel when a media volume is mounted

* tolerate homekit config chown failures in the go2rtc run script

* chown the s6 log pipe so non-root nginx can reopen /dev/stdout

* set HOME to /config for non-root services

* run smoke nginx -t and the write probe as the runtime user

* re-own the nginx shm cache on service restart

* discard stdout for the unprivileged smoke nginx -t

* unwrap hard-wrapped prose in the installation docs

* report progress during the ownership sweep

* document EXTRA_GROUPS as the only device access path for dropped services

* expand the non-root device access docs with diagnosis steps and udev rules

* document network storage ownership and the remaining detector hardware

* skip lost+found during the ownership sweep

* hand /tmp/cache to the runtime user before services start

* make bundled models readable by the runtime user

* reload nginx by signaling the master instead of parsing its config as root

* harden root writes into unprivileged-owned paths

Restrict the sweep sentinel to a mount at or below /media/frigate so a
parent /media mount cannot bless a later-shadowed volume. Rebuild
/tmp/nginx root-owned each start so root's cp and tempio writes cannot
follow a symlink an unprivileged nginx planted in the previous run.

* collapse the duplicated sentinel comment

* add a service-runs-as-root helper for granular root services

* validate FRIGATE_ROOT_SERVICES and fail fast on unknown names

* let services listed in FRIGATE_ROOT_SERVICES skip the privilege drop

* record the root-services mode in the sentinel and sweep small trees each boot

* cache the runtime ids in the ownership helper

* chown recordings, previews, and exports to the runtime user at create

* chown the database files after init

* recommend FRIGATE_ROOT_SERVICES in the bandwidth stats warning

* assert granular root services in CI

* document FRIGATE_ROOT_SERVICES

* own every directory level created for a recording segment

* clear the cached runtime ids when ownership tests finish

* skip missing media paths in the per-boot ownership sweep

* clarify granular root services docs

* clean up

* install acl for device access grants

* grant runtime users access to mapped device nodes at boot

* assert device access grants in CI

* document automatic device access grants

* stop telling users device access needs host side setup

* clarify the non-root docs

* link the migration script to the repo

* group the manual device setup under one section

* harden against symlink attacks

/config is owned by the unprivileged runtime user after the ownership sweep, so root operations on files there could be redirected by a planted symlink.

- go2rtc HomeKit setup: replace the root yq/jq normalization and chown with an O_NOFOLLOW helper (prepare_homekit.py), so a symlink at go2rtc_homekit.yml can't redirect a root write or chown onto another file
- go2rtc binary override: ignore /config/go2rtc whenever the service runs as root, so a planted binary can't exec as root under FRIGATE_ROOT_SERVICES
- sweep sentinel: read and write it through safe-sentinel, which trusts only a root-owned regular file and never follows a symlink, so it can't be forged to skip the migration or symlinked to clobber a root file
- ownership sweep: chown with -execdir so a parent directory swapped for a symlink mid-walk can't redirect the chown out of the volume
- validate inputs: restrict DEVICE_ACL_PATHS to /dev, require nonzero numeric EXTRA_GROUPS, and reject PUID/PGID that collide with the go2rtc ids
- docs: correct the TLS key ownership note to match what actually happens

* tweak docs

* stop the ownership sweep chasing entries other mechanisms own

* keep custom binaries out of root services only under granular root

docker/main/rootfs/etc/s6-overlay/s6-rc.d/prepare/run

@@ -153,7 +153,50 @@ if [[ "$(id -u)" -eq 0 ]]; then
     if [[ "${FRIGATE_RUN_AS_ROOT:-false}" == "true" ]]; then
         rm -f /config/.permissions_version
     else
-        /usr/local/bin/fix-ownership --sentinel /config/.permissions_version \
+        # Only when a mount backs /media/frigate itself: under a parent /media
+        # mount, a dedicated volume added later would be shadowed and skipped
+        sentinel_args=(--sentinel /config/.permissions_version)
+        root_services_mode=""
+        if [[ -n "${FRIGATE_ROOT_SERVICES:-}" ]]; then
+            # || true: an all-empty list (",") fails grep -v and errexit would kill the boot
+            root_services_mode=$(tr ',' '\n' <<< "${FRIGATE_ROOT_SERVICES//[[:space:]]/}" | grep -v '^$' | sort -u | paste -sd, - || true)
+            if [[ -n "$root_services_mode" ]]; then
+                sentinel_args+=(--mode "$root_services_mode")
+            fi
+        fi
+        if ! awk '$2 == "/media/frigate" || $2 ~ /^\/media\/frigate\//' /proc/mounts | grep -q .; then
+            sentinel_args=()
+        fi
+        /usr/local/bin/fix-ownership "${sentinel_args[@]}" \
             "${PUID:-1000}" "${PGID:-1000}" /config /media/frigate
+
+        # Root services write clips stragglers and caches mid-run; realign the
+        # small trees every boot. Recordings are chowned at create instead.
+        if [[ -n "$root_services_mode" ]]; then
+            # only sweep what exists; clips and exports appear after the first run
+            boot_sweep_paths=(/config)
+            for extra in /media/frigate/clips /media/frigate/exports; do
+                if [[ -d "$extra" ]]; then
+                    boot_sweep_paths+=("$extra")
+                fi
+            done
+            /usr/local/bin/fix-ownership \
+                "${PUID:-1000}" "${PGID:-1000}" "${boot_sweep_paths[@]}"
+        fi
     fi
 fi
+
+# Must stay after the sweep, which reads an absent /media/frigate as an
+# unmounted volume rather than a swept one
+if [[ "$(id -u)" -eq 0 && ! -d /media/frigate ]]; then
+    mkdir -p /media/frigate
+    if [[ "${FRIGATE_RUN_AS_ROOT:-false}" != "true" ]]; then
+        chown "${PUID:-1000}:${PGID:-1000}" /media/frigate
+    fi
+fi
+
+# usually a tmpfs mount: root-owned on arrival and outside the swept volumes
+if [[ "$(id -u)" -eq 0 && "${FRIGATE_RUN_AS_ROOT:-false}" != "true" ]]; then
+    mkdir -p /tmp/cache
+    chown "${PUID:-1000}:${PGID:-1000}" /tmp/cache
+fi