keep /config out of the root environment in the frigate run script

The script exported HOME=/config and prepended /config/.local/lib to LD_LIBRARY_PATH while still root, then ran python3, ffmpeg, grep, and opt_in_out as root. The runtime user owns /config, so it could plant a .pth file in the user site-packages or a library on the loader path and get code run as root on the next start. Root helpers now run with root's environment (and python3 -I), and HOME, LD_LIBRARY_PATH, and PATH reach only the dropped process through env on the s6-setuidgid line. opt_in_out runs as the runtime user, so the openvino marker no longer gets written into /config by root.

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

@@ -11,30 +11,14 @@ if [[ "$(id -u)" -eq 0 ]]; then
     fi
 fi
 
-# /root survives s6-setuidgid and breaks cache writes after the drop; set
-# before opt_in_out so the opt-out marker lands where the service will look
-if [[ "$runs_as_root" -eq 0 ]]; then
-    export HOME=/config
-fi
-
-# detector runtimes installed at first start (pip install --user) live under
-# $HOME/.local; the dynamic loader only reads LD_LIBRARY_PATH at exec time
-export LD_LIBRARY_PATH="${LD_LIBRARY_PATH:+${LD_LIBRARY_PATH}:}${HOME}/.local/lib"
-export PATH="${PATH}:${HOME}/.local/bin"
-
-# opt out of openvino telemetry
-if [ -e /usr/local/bin/opt_in_out ]; then
-  /usr/local/bin/opt_in_out --opt_out > /dev/null 2>&1
-fi
-
-# Logs should be sent to stdout so that s6 can collect them
-
 # Tell S6-Overlay not to restart this service
 s6-svc -O .
 
+# Runs as root before any /config path enters the environment; -I skips the
+# user site-packages under $HOME
 function set_libva_version() {
     local ffmpeg_path
-    ffmpeg_path=$(python3 /usr/local/ffmpeg/get_ffmpeg_path.py)
+    ffmpeg_path=$(python3 -I /usr/local/ffmpeg/get_ffmpeg_path.py)
     LIBAVFORMAT_VERSION_MAJOR=$("$ffmpeg_path" -version | grep -Po "libavformat\W+\K\d+")
     export LIBAVFORMAT_VERSION_MAJOR
 }
@@ -42,14 +26,30 @@ function set_libva_version() {
 echo "[INFO] Preparing Frigate..."
 set_libva_version
 
+# HOME=/root survives s6-setuidgid, so the drop sets HOME=/config. The runtime
+# user owns /config, so these paths go only to the service process, never to
+# root. Detector runtimes installed at first start (pip install --user) live
+# under $HOME/.local.
+run_as=()
+runtime_home="${HOME}"
+if [[ "$(id -u)" -eq 0 && "$runs_as_root" -eq 0 ]]; then
+    run_as=(s6-setuidgid frigate)
+    runtime_home=/config
+fi
+run_as+=(env
+    "HOME=${runtime_home}"
+    "LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+${LD_LIBRARY_PATH}:}${runtime_home}/.local/lib"
+    "PATH=${PATH}:${runtime_home}/.local/bin")
+
+# opt out of openvino telemetry; the marker lands under the service's HOME
+if [ -e /usr/local/bin/opt_in_out ]; then
+  "${run_as[@]}" /usr/local/bin/opt_in_out --opt_out > /dev/null 2>&1
+fi
+
 echo "[INFO] Starting Frigate..."
 
 cd /opt/frigate || echo "[ERROR] Failed to change working directory to /opt/frigate"
 
 # Replace the bash process with the Frigate process, redirecting stderr to stdout
 exec 2>&1
-if [[ "$(id -u)" -ne 0 || "$runs_as_root" -eq 1 ]]; then
+exec "${run_as[@]}" python3 -u -m frigate
-    exec python3 -u -m frigate
-else
-    exec s6-setuidgid frigate python3 -u -m frigate
-fi