biod/init/biod.conf

# Copyright 2016 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

description   "Start the Chromium OS biometrics daemon"
author        "chromium-os-dev@chromium.org"

start on started system-services and stopped bio_crypto_init and started uinput
stop on stopping system-services
respawn
respawn limit 3 10  # if the job respawns 3 times in 10 seconds, stop trying.

env LOG_DIR=/var/log/biod
env FP_DEV=/dev/cros_fp

pre-start script
  mkdir -m 755 -p "${LOG_DIR}"
  chown biod:biod "${LOG_DIR}"
  # Check the existence of ${FP_DEV}.
  if [ ! -c "${FP_DEV}" ]; then
    echo "${FP_DEV} not available, stopping." > /var/log/biod.out
    stop
    exit 0
  fi
end script

# Here (in order) are a list of the args added:
# - Create and enter new UTS namespace (hostname/NIS domain name).
# - Create and enter new network namespace.
# - Create and enter new IPC namespace.
# - Create and enter new cgroup namespace.
# - Create and enter new PID namespace.
# - Set mount namespace to be a slave mount.
# - Set up a new VFS namespace (although this should be covered by
#   minimalistic-mountns, leaving this out yields the following error:
#   "Can't skip marking mounts as MS_PRIVATE without mount namespaces.")
# - Use the minimal mountns profile to start.
# - Get a writeable and empty /run tmpfs path.
# - Mount dbus.
# - Provide access to chromeos-config thru /run/chromeos-config/v1.
# - Mount daemon store with the MS_BIND|MS_REC options to handle the case
#   biod starts after the user's cryptohome is already mounted (e.g. after a
#   crash).
# - Get a writeable and empty /var tmpfs path.
# - Mount the log directory in it.
# - Mount the metrics directory.
# - Mount the FPMCU dev node.
# - Mount the /dev/uinput directory.
# - Mount the /sys directory as chromeos-config tries to get the product name,
#   sku and other details from sysfs files.
# - Run as biod user and group.
# - Inherit supplementary groups from from user biod.
# - Grant no caps.
# - No new privileges (no_new_privs).
# - Use biod seccomp policy.
# - Execute the daemon.
# - Add the log dir.
# - Pipe output to biod.out.
exec minijail0                                                               \
  --uts                                                                      \
  -e                                                                         \
  -l                                                                         \
  -N                                                                         \
  -p                                                                         \
  -Kslave                                                                    \
  -v                                                                         \
  --profile minimalistic-mountns                                             \
  -k 'tmpfs,/run,tmpfs,MS_NODEV|MS_NOEXEC|MS_NOSUID,mode=755,size=10M'       \
  -b /run/dbus                                                               \
  -b /run/chromeos-config/v1                                                 \
  -k '/run/daemon-store/biod,/run/daemon-store/biod,none,MS_BIND|MS_REC'     \
  -k 'tmpfs,/var,tmpfs,MS_NODEV|MS_NOEXEC|MS_NOSUID,mode=755,size=10M'       \
  -b ${LOG_DIR},,1                                                           \
  -b /var/lib/metrics,,1                                                     \
  -b ${FP_DEV}                                                               \
  -b /dev/uinput                                                             \
  -b /sys                                                                    \
  -u biod -g biod                                                            \
  -G                                                                         \
  -c 0                                                                       \
  -n                                                                         \
  -S /usr/share/policy/biod-seccomp.policy                                   \
  -- /usr/bin/biod                                                           \
  --log_dir=${LOG_DIR}                                                       \
  >/var/log/biod.out 2>&1