Container security hardening (phase 2) (#24068)

* Create frigate and go2rtc runtime users in the image

* Add single fix-ownership helper for volume permission migration

* Add init-usermod oneshot for PUID and PGID remapping

* Chown newly created runtime directories to the frigate user

* Run sentinel-guarded ownership sweep during prepare

* Add host-side volume permission migration script

* Guard log directory ownership for user-mode startup

* Fall back to plain s6-log when running without root

* Assert PUID remapping and sweep sentinel in CI smoke test

* Skip the ownership sweep in the devcontainer

* Pin FRIGATE_RUN_AS_ROOT in ownership tests

* Do not record the sweep as complete when a chown failed

* Validate PUID and PGID in the migration script

* Treat a failed ownership scan as an incomplete sweep

* Reject PUID and PGID of 0 during remapping

* Handle symlinks, dry runs, and sentinel write failures in the sweep

* Treat an absent sweep root as an incomplete sweep

.github/workflows/ci.yml

@@ -94,6 +94,34 @@ jobs:
           docker exec frigate /usr/local/nginx/sbin/nginx -t
           docker exec frigate stat -c %a /etc/letsencrypt/live/frigate/privkey.pem | grep -qx 600
           docker exec frigate stat -c %a /dev/shm/go2rtc.yaml | grep -qx 640
+      - name: Assert PUID/PGID remapping
+        run: |
+          mkdir -p /tmp/frigate-config-puid
+          printf 'mqtt:\n  enabled: false\ncameras: {}\n' > /tmp/frigate-config-puid/config.yml
+          docker run -d --name frigate-puid --shm-size 256m \
+            -e PUID=1500 -e PGID=1500 \
+            -v /tmp/frigate-config-puid:/config \
+            ${{ steps.setup.outputs.image-name }}-amd64
+          up=0
+          for i in $(seq 1 60); do
+            docker exec frigate-puid curl -fs http://127.0.0.1:5000/api/version && up=1 && break
+            sleep 5
+          done
+          if [ "$up" -ne 1 ]; then echo "PUID container never became healthy"; docker logs frigate-puid; exit 1; fi
+          docker exec frigate-puid id -u frigate | grep -qx 1500
+          docker exec frigate-puid id -g frigate | grep -qx 1500
+          docker exec frigate-puid cat /config/.permissions_version | grep -qx "1:1500:1500"
+          # second boot must skip the sweep (sentinel hit). Poll rather than
+          # sleep: the string can only come from the second boot (the first
+          # had no sentinel), so grepping the full log is unambiguous.
+          docker restart frigate-puid
+          ok=0
+          for i in $(seq 1 30); do
+            docker logs frigate-puid 2>&1 | grep -q "already applied" && ok=1 && break
+            sleep 2
+          done
+          if [ "$ok" -ne 1 ]; then echo "sentinel skip never logged"; docker logs frigate-puid; exit 1; fi
+          docker rm -f frigate-puid
       - name: Teardown
         if: always()
         run: docker rm -f frigate || true

docker/main/Dockerfile

@@ -265,6 +265,23 @@ ENV PATH="/usr/local/go2rtc/bin:/usr/local/tempio/bin:/usr/local/nginx/sbin:${PA
 RUN --mount=type=bind,source=docker/main/install_deps.sh,target=/deps/install_deps.sh \
     /deps/install_deps.sh
 
+# Runtime users. frigate may be remapped at start via PUID/PGID (init-usermod)
+# or replaced entirely with docker's --user. go2rtc is intentionally separate
+# and more restricted. frigate-data is the shared group for /config access.
+# -o tolerates variant base images that already contain uid/gid 1000.
+RUN groupadd -o --gid 1000 frigate \
+    && useradd -o --uid 1000 --gid frigate --no-create-home --shell /usr/sbin/nologin frigate \
+    && groupadd --system go2rtc \
+    && useradd --system --gid go2rtc --no-create-home --shell /usr/sbin/nologin go2rtc \
+    && groupadd --system frigate-data \
+    && usermod -aG frigate-data frigate \
+    && usermod -aG frigate-data go2rtc \
+    && for grp in video render plugdev audio; do \
+         if getent group "$grp" >/dev/null; then \
+           usermod -aG "$grp" frigate && usermod -aG "$grp" go2rtc; \
+         fi; \
+       done
+
 ENV DEFAULT_FFMPEG_VERSION="8.0"
 ENV INCLUDED_FFMPEG_VERSIONS="${DEFAULT_FFMPEG_VERSION}:7.0:5.0"
 
@@ -307,6 +324,11 @@ HEALTHCHECK --start-period=300s --start-interval=5s --interval=15s --timeout=5s
 # Frigate deps with Node.js and NPM for devcontainer
 FROM deps AS devcontainer
 
+# /config here is the developer's bind-mounted checkout, not a data volume, so
+# the prepare ownership sweep must not run: it would chown the source tree to
+# the runtime uid and lock out any container user that isn't 1000.
+ENV FRIGATE_RUN_AS_ROOT=true
+
 # Do not start the actual Frigate service on devcontainer as it will be started by VS Code
 # But start a fake service for simulating the logs
 COPY docker/main/fake_frigate_run /etc/s6-overlay/s6-rc.d/frigate/run

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

@@ -1,4 +1,12 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash
 
-exec logutil-service /dev/shm/logs/certsync
+if [[ "$(id -u)" -eq 0 ]]; then
+    # logutil-service drops to nobody and applies S6_LOGGING_SCRIPT
+    exec logutil-service /dev/shm/logs/certsync
+fi
+
+# Non-root (--user) fallback: logutil-service cannot change UID, so run
+# s6-log directly with the same directives S6_LOGGING_SCRIPT configures.
+# shellcheck disable=SC2086
+exec s6-log ${S6_LOGGING_SCRIPT:-T 1 n0 s10000000 T} /dev/shm/logs/certsync

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

@@ -1,4 +1,12 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash
 
-exec logutil-service /dev/shm/logs/frigate
+if [[ "$(id -u)" -eq 0 ]]; then
+    # logutil-service drops to nobody and applies S6_LOGGING_SCRIPT
+    exec logutil-service /dev/shm/logs/frigate
+fi
+
+# Non-root (--user) fallback: logutil-service cannot change UID, so run
+# s6-log directly with the same directives S6_LOGGING_SCRIPT configures.
+# shellcheck disable=SC2086
+exec s6-log ${S6_LOGGING_SCRIPT:-T 1 n0 s10000000 T} /dev/shm/logs/frigate

docker/main/rootfs/etc/s6-overlay/s6-rc.d/go2rtc-log/run

@@ -1,4 +1,12 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash
 
-exec logutil-service /dev/shm/logs/go2rtc
+if [[ "$(id -u)" -eq 0 ]]; then
+    # logutil-service drops to nobody and applies S6_LOGGING_SCRIPT
+    exec logutil-service /dev/shm/logs/go2rtc
+fi
+
+# Non-root (--user) fallback: logutil-service cannot change UID, so run
+# s6-log directly with the same directives S6_LOGGING_SCRIPT configures.
+# shellcheck disable=SC2086
+exec s6-log ${S6_LOGGING_SCRIPT:-T 1 n0 s10000000 T} /dev/shm/logs/go2rtc

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

@@ -0,0 +1,61 @@
+#!/command/with-contenv bash
+# shellcheck shell=bash
+# Remap the frigate user to PUID/PGID and register EXTRA_GROUPS.
+# No-op when: started with --user (euid != 0), FRIGATE_RUN_AS_ROOT=true,
+# or PUID/PGID already match.
+
+set -o errexit -o nounset -o pipefail
+
+if [[ "$(id -u)" -ne 0 ]]; then
+    # Started with docker --user; the host owns UID mapping entirely.
+    exit 0
+fi
+
+if [[ "${FRIGATE_RUN_AS_ROOT:-false}" == "true" ]]; then
+    echo "[INFO] FRIGATE_RUN_AS_ROOT=true: skipping user remapping"
+    exit 0
+fi
+
+puid="${PUID:-1000}"
+pgid="${PGID:-1000}"
+
+if ! [[ "$puid" =~ ^[0-9]+$ && "$pgid" =~ ^[0-9]+$ ]]; then
+    echo "[ERROR] PUID and PGID must be numeric, got '${puid}' and '${pgid}'" >&2
+    exit 1
+fi
+
+# Remapping to 0 would make the frigate user root, so every service would keep
+# full privilege while reporting a successful migration.
+if [[ "$puid" -eq 0 || "$pgid" -eq 0 ]]; then
+    echo "[ERROR] PUID/PGID 0 would run the services as root and defeat the privilege separation." >&2
+    echo "[ERROR] Set FRIGATE_RUN_AS_ROOT=true if you want to keep running as root." >&2
+    exit 1
+fi
+
+current_uid="$(id -u frigate)"
+current_gid="$(id -g frigate)"
+
+if [[ "$puid" != "$current_uid" || "$pgid" != "$current_gid" ]]; then
+    if [[ ! -w /etc/passwd ]]; then
+        echo "[ERROR] PUID/PGID remapping needs a writable /etc and is not compatible with read_only: true." >&2
+        echo "[ERROR] Either remove read_only and keep PUID, or drop PUID/PGID and use docker's user: ${puid}:${pgid} instead." >&2
+        echo "[ERROR] See https://docs.frigate.video/configuration/non_root for the compatibility matrix." >&2
+        exit 1
+    fi
+    echo "[INFO] Remapping frigate user to ${puid}:${pgid}"
+    groupmod -o -g "$pgid" frigate
+    usermod -o -u "$puid" frigate
+fi
+
+# EXTRA_GROUPS: numeric host GIDs granting device access (e.g. host render/video)
+if [[ -n "${EXTRA_GROUPS:-}" ]]; then
+    for gid in ${EXTRA_GROUPS//,/ }; do
+        if ! getent group "$gid" >/dev/null; then
+            groupadd -o -g "$gid" "frigate-extra-${gid}"
+        fi
+        group_name="$(getent group "$gid" | cut -d: -f1)"
+        usermod -aG "$group_name" frigate
+        usermod -aG "$group_name" go2rtc
+        echo "[INFO] Added frigate and go2rtc to supplementary group ${group_name} (gid ${gid})"
+    done
+fi

docker/main/rootfs/etc/s6-overlay/s6-rc.d/init-usermod/type

@@ -0,0 +1 @@
+oneshot

docker/main/rootfs/etc/s6-overlay/s6-rc.d/init-usermod/up

@@ -0,0 +1 @@
+/etc/s6-overlay/s6-rc.d/init-usermod/run

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

@@ -7,5 +7,12 @@ set -o errexit -o nounset -o pipefail
 dirs=(/dev/shm/logs/frigate /dev/shm/logs/go2rtc /dev/shm/logs/nginx /dev/shm/logs/certsync)
 
 mkdir -p "${dirs[@]}"
-chown nobody:nogroup "${dirs[@]}"
+
+# logutil-service drops s6-log to nobody, so the dirs must stay nobody-owned
+# in root mode. Under docker --user we are already the (only) target user,
+# chown would fail, and the plain s6-log fallback in the *-log services
+# writes as us (the mkdir above is sufficient, /dev/shm is 1777).
+if [[ "$(id -u)" -eq 0 ]]; then
+    chown nobody:nogroup "${dirs[@]}"
+fi
 chmod 02755 "${dirs[@]}"

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

@@ -1,4 +1,12 @@
 #!/command/with-contenv bash
 # shellcheck shell=bash
 
-exec logutil-service /dev/shm/logs/nginx
+if [[ "$(id -u)" -eq 0 ]]; then
+    # logutil-service drops to nobody and applies S6_LOGGING_SCRIPT
+    exec logutil-service /dev/shm/logs/nginx
+fi
+
+# Non-root (--user) fallback: logutil-service cannot change UID, so run
+# s6-log directly with the same directives S6_LOGGING_SCRIPT configures.
+# shellcheck disable=SC2086
+exec s6-log ${S6_LOGGING_SCRIPT:-T 1 n0 s10000000 T} /dev/shm/logs/nginx

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

@@ -144,3 +144,16 @@ rm -f /dev/shm/.frigate-is-stopping
 
 migrate_addon_config_dir
 migrate_db_from_media_to_config
+
+# Align volume ownership with the runtime user (one sweep per PUID/schema
+# change, guarded by the sentinel; see fix-ownership). The escape hatch
+# deletes the sentinel instead: ownership is never mutated while it is on,
+# so the next non-root boot must re-sweep whatever root created meanwhile.
+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 \
+            "${PUID:-1000}" "${PGID:-1000}" /config /media/frigate
+    fi
+fi

docker/main/rootfs/usr/local/bin/fix-ownership

@@ -0,0 +1,129 @@
+#!/bin/bash
+# Single source of truth for aligning volume ownership with the runtime user.
+#
+# Usage: fix-ownership [--dry-run] [--sentinel FILE] UID GID PATH [PATH...]
+#
+#   --dry-run    report what would change, touch nothing
+#   --sentinel   skip entirely when FILE already records "SCHEMA:UID:GID";
+#                write it after a successful run (used by the boot path so
+#                multi-TB volumes are swept once per UID/schema change, not
+#                on every boot)
+#
+# Only files whose uid OR gid differs are touched, so re-runs are cheap.
+# Top-level /config additionally grants group frigate-data TRAVERSE ONLY
+# (g+rx) so the separate go2rtc user can reach its pre-created HomeKit file
+# on hosts where /config is mounted 0700. Never g+w: directory write means
+# unlink rights over frigate.db/config.yml, and would let a compromised
+# go2rtc plant /config/go2rtc, which the go2rtc run script executes
+# preferentially, as root under the escape hatch.
+
+set -o errexit -o nounset -o pipefail
+
+# Permissions-layout epoch. Bump to force a one-time re-sweep on upgrade
+# (e.g. when the privilege-drop release must capture files created as root
+# since the previous sweep).
+schema=1
+
+dry_run=0
+sentinel=""
+
+while [[ "${1:-}" == --* ]]; do
+    case "$1" in
+        --dry-run) dry_run=1; shift ;;
+        --sentinel)
+            if [[ -z "${2:-}" ]]; then
+                echo "[ERROR] fix-ownership: --sentinel requires a file argument" >&2
+                exit 2
+            fi
+            sentinel="$2"; shift 2 ;;
+        *) echo "[ERROR] fix-ownership: unknown option $1" >&2; exit 2 ;;
+    esac
+done
+
+if [[ $# -lt 3 ]]; then
+    echo "Usage: fix-ownership [--dry-run] [--sentinel FILE] UID GID PATH..." >&2
+    exit 2
+fi
+
+target_uid="$1"
+target_gid="$2"
+shift 2
+
+if [[ "$(id -u)" -ne 0 ]]; then
+    echo "[INFO] fix-ownership: not running as root, skipping (ownership is managed by the host in --user mode)"
+    exit 0
+fi
+
+# A dry run always inspects: the sentinel records what a past sweep did, not
+# what the volume looks like now, and reporting from it would hide later drift.
+if [[ "$dry_run" -eq 0 && -n "$sentinel" && -f "$sentinel" && "$(cat "$sentinel")" == "${schema}:${target_uid}:${target_gid}" ]]; then
+    echo "[INFO] fix-ownership: ${target_uid}:${target_gid} (schema ${schema}) already applied, skipping"
+    exit 0
+fi
+
+# A sweep that could not chown everything must not be recorded as complete:
+# the sentinel would make every later boot skip it and the entries would stay
+# unreachable once services run unprivileged.
+swept_clean=1
+
+for path in "$@"; do
+    # An absent root is an incomplete sweep, not a finished one: /media/frigate
+    # is not in the image, so a boot before the volume is mounted would
+    # otherwise record success and the volume would never be swept once added.
+    if [[ ! -d "$path" ]]; then
+        swept_clean=0
+        echo "[WARN] fix-ownership: $path does not exist, skipping; will retry on next boot"
+        continue
+    fi
+
+    # find may fail mid-walk on a live volume (file deleted under it) or on a
+    # stale mount. Tolerate it rather than aborting under errexit, but never
+    # read a failed scan as "nothing to do": that would record the sweep as
+    # complete without having looked.
+    if ! count=$(find "$path" \( -not -uid "$target_uid" -o -not -gid "$target_gid" \) -printf '.' 2>/dev/null | wc -c); then
+        swept_clean=0
+        echo "[WARN] fix-ownership: could not scan ${path}; will retry on next boot"
+        continue
+    fi
+
+    if [[ "$count" -eq 0 ]]; then
+        echo "[INFO] fix-ownership: $path already owned by ${target_uid}:${target_gid}, nothing to do"
+        continue
+    fi
+
+    # find does not descend symlinks and chown -h retargets the link itself, so
+    # anything behind a symlinked directory is outside this sweep. Following
+    # them is not an option: a link could walk the chown out of the volume.
+    if [[ -n "$(find "$path" -type l -xtype d -print -quit 2>/dev/null)" ]]; then
+        echo "[WARN] fix-ownership: ${path} contains symlinked directories; ownership behind them is not managed and must be aligned by hand"
+    fi
+
+    echo "[WARN] fix-ownership: adjusting ownership of ${count} entries under ${path}; on large recordings volumes this can take a long time"
+    if [[ "$dry_run" -eq 1 ]]; then
+        echo "[INFO] fix-ownership: dry run, not changing ${path}"
+        continue
+    fi
+
+    find "$path" \( -not -uid "$target_uid" -o -not -gid "$target_gid" \) \
+        -exec chown -h "${target_uid}:${target_gid}" {} + || {
+        swept_clean=0
+        echo "[WARN] fix-ownership: some entries under ${path} could not be updated (deleted mid-sweep or chown denied); will retry on next mismatch"
+    }
+done
+
+# go2rtc (separate user) must be able to REACH its HomeKit state in /config.
+# Write access is per-file, not per-directory: go2rtc's PatchConfig rewrites
+# the first -config file via os.WriteFile (in-place truncate, no rename,
+# verified against go2rtc v1.9.14 internal/app/config.go), and the file is
+# always pre-created by setup_homekit_config before go2rtc starts, so
+# O_CREATE never needs directory write. See header comment for why g+w is
+# forbidden here.
+if [[ "$dry_run" -eq 0 && -d /config ]]; then
+    chgrp frigate-data /config 2>/dev/null || true
+    chmod g+rx /config 2>/dev/null || true
+fi
+
+if [[ "$dry_run" -eq 0 && -n "$sentinel" && "$swept_clean" -eq 1 ]]; then
+    echo "${schema}:${target_uid}:${target_gid}" > "$sentinel" || \
+        echo "[WARN] fix-ownership: could not write ${sentinel}; the sweep will run again on next boot"
+fi

docker/migration/fix-permissions.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+# Ahead-of-time volume ownership migration for switching Frigate to non-root.
+# Run from the host BEFORE enabling PUID/PGID or --user:
+#
+#   ./fix-permissions.sh [--dry-run] <config_dir> <media_dir> [PUID] [PGID]
+#
+# Wraps the image's fix-ownership helper so there is exactly one
+# implementation of the chown logic. Requires an image that contains the
+# helper (any release that includes non-root support).
+
+set -o errexit -o nounset -o pipefail
+
+IMAGE="${FRIGATE_IMAGE:-ghcr.io/blakeblackshear/frigate:stable}"
+
+dry_run_flag=""
+if [[ "${1:-}" == "--dry-run" ]]; then
+    dry_run_flag="--dry-run"
+    shift
+fi
+
+if [[ $# -lt 2 ]]; then
+    echo "Usage: $0 [--dry-run] <config_dir> <media_dir> [PUID] [PGID]" >&2
+    exit 2
+fi
+
+config_dir="$1"
+media_dir="$2"
+puid="${3:-1000}"
+pgid="${4:-1000}"
+
+# The ids are interpolated into the container's bash -c source below, so
+# anything but digits would be reparsed as shell rather than passed through
+if ! [[ "$puid" =~ ^[0-9]+$ && "$pgid" =~ ^[0-9]+$ ]]; then
+    echo "[ERROR] PUID and PGID must be numeric, got '${puid}' and '${pgid}'" >&2
+    exit 2
+fi
+
+echo "[INFO] Using image ${IMAGE} (override with FRIGATE_IMAGE=...)"
+# shellcheck disable=SC2086
+docker run --rm \
+    -v "${config_dir}:/config" \
+    -v "${media_dir}:/media/frigate" \
+    --entrypoint bash \
+    "${IMAGE}" \
+    -c "command -v fix-ownership >/dev/null || { echo '[ERROR] this Frigate image predates non-root support; set FRIGATE_IMAGE to a release that includes it' >&2; exit 1; }; exec fix-ownership ${dry_run_flag} ${puid} ${pgid} /config /media/frigate"

frigate/app.py

@@ -86,6 +86,7 @@ from frigate.timeline import TimelineProcessor
 from frigate.track.object_processing import TrackedObjectProcessor
 from frigate.util.builtin import empty_and_close_queue
 from frigate.util.image import UntrackedSharedMemory
+from frigate.util.ownership import chown_to_runtime
 from frigate.util.process import FrigateProcess
 from frigate.util.services import set_file_limit
 from frigate.version import VERSION
@@ -149,6 +150,7 @@ class FrigateApp:
             if not os.path.exists(d) and not os.path.islink(d):
                 logger.info(f"Creating directory: {d}")
                 os.makedirs(d, exist_ok=True)
+                chown_to_runtime(d)
             else:
                 logger.debug(f"Skipping directory: {d}")
 

frigate/test/test_ownership.py

@@ -0,0 +1,59 @@
+"""Tests for runtime ownership helpers."""
+
+import unittest
+from unittest.mock import patch
+
+from frigate.util import ownership
+
+
+class FakePwEntry:
+    pw_uid = 1500
+    pw_gid = 1500
+
+
+# The devcontainer image exports FRIGATE_RUN_AS_ROOT, so any test that has to
+# reach past the escape-hatch check pins the variable instead of inheriting it.
+class TestGetRuntimeIds(unittest.TestCase):
+    @patch("frigate.util.ownership.os.geteuid", return_value=1000)
+    def test_returns_none_when_not_root(self, _):
+        assert ownership.get_runtime_ids() is None
+
+    @patch.dict("os.environ", {"FRIGATE_RUN_AS_ROOT": "true"})
+    @patch("frigate.util.ownership.os.geteuid", return_value=0)
+    def test_returns_none_with_escape_hatch(self, _):
+        assert ownership.get_runtime_ids() is None
+
+    @patch.dict("os.environ", {"FRIGATE_RUN_AS_ROOT": "false"})
+    @patch("frigate.util.ownership.pwd.getpwnam", side_effect=KeyError)
+    @patch("frigate.util.ownership.os.geteuid", return_value=0)
+    def test_returns_none_outside_frigate_image(self, *_):
+        assert ownership.get_runtime_ids() is None
+
+    @patch.dict("os.environ", {"FRIGATE_RUN_AS_ROOT": "false"})
+    @patch("frigate.util.ownership.pwd.getpwnam", return_value=FakePwEntry())
+    @patch("frigate.util.ownership.os.geteuid", return_value=0)
+    def test_returns_frigate_ids_as_root(self, *_):
+        assert ownership.get_runtime_ids() == (1500, 1500)
+
+
+class TestChownToRuntime(unittest.TestCase):
+    @patch("frigate.util.ownership.os.chown")
+    @patch("frigate.util.ownership.get_runtime_ids", return_value=None)
+    def test_noop_when_no_runtime_ids(self, _, chown):
+        ownership.chown_to_runtime("/config/test")
+        chown.assert_not_called()
+
+    @patch("frigate.util.ownership.os.chown")
+    @patch("frigate.util.ownership.get_runtime_ids", return_value=(1500, 1500))
+    def test_chowns_to_runtime_ids(self, _, chown):
+        ownership.chown_to_runtime("/config/test")
+        chown.assert_called_once_with("/config/test", 1500, 1500)
+
+    @patch("frigate.util.ownership.os.chown", side_effect=OSError("ro fs"))
+    @patch("frigate.util.ownership.get_runtime_ids", return_value=(1500, 1500))
+    def test_swallows_oserror(self, *_):
+        ownership.chown_to_runtime("/config/test")  # must not raise
+
+
+if __name__ == "__main__":
+    unittest.main()

frigate/util/ownership.py

@@ -0,0 +1,43 @@
+"""Helpers for aligning created files with the non-root runtime user."""
+
+import logging
+import os
+import pwd
+
+logger = logging.getLogger(__name__)
+
+RUNTIME_USER = "frigate"
+
+
+def get_runtime_ids() -> tuple[int, int] | None:
+    """Return (uid, gid) that services run as, or None when chown is not applicable.
+
+    None when: not root (docker --user, so the host already mapped us),
+    FRIGATE_RUN_AS_ROOT=true (escape hatch must not mutate ownership),
+    or outside the Frigate container image (no frigate user).
+    """
+    if os.geteuid() != 0:
+        return None
+
+    if os.environ.get("FRIGATE_RUN_AS_ROOT", "false") == "true":
+        return None
+
+    try:
+        user = pwd.getpwnam(RUNTIME_USER)
+    except KeyError:
+        return None
+
+    return (user.pw_uid, user.pw_gid)
+
+
+def chown_to_runtime(path: str) -> None:
+    """Best-effort chown of path to the runtime user."""
+    ids = get_runtime_ids()
+
+    if ids is None:
+        return
+
+    try:
+        os.chown(path, *ids)
+    except OSError as err:
+        logger.warning(f"Unable to set ownership of {path}: {err}")