typecd/init/typecd.conf

# Copyright 2020 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 USB Type C daemon"
author        "chromium-os-dev@chromium.org"

start on started system-services
stop on stopping system-services
expect fork
respawn
respawn limit 3 10  # if the job respawns 3 times in 10 seconds, stop trying.

# Typecd *should* be able to recover from crashes (rebuild state when we start),
# so better to get OOM-killed than cause a memory panic.
oom score -100

# Let the daemon crash if it grows too much. "as" is "address space" (vm
# size). We expect a typical VM size of about 20MB for the daemon (currently)
# so set a limit for 5x that.
limit as 100000000 unlimited

# Here (in order) are a list of the args added:
# - Exit immediately after fork. The jailed process will run in the background.
# - Create and enter new UTS namespace (hostname/NIS domain name).
# - Create and enter new cgroup namespace.
# - Create and enter new PID namespace.
# - Use the minimal mountns profile to start.
# - Get a writeable and empty /run tmpfs path.
# - Mount D-Bus.
# - Mount /run/udev so that we can receive udev monitor events.
# - Get a writeable and empty /sys tmpfs path.
# - Mount the /sys/class/typec directory required by typecd.
# - Mount the /sys/devices directory required by typecd.
# - Run as typecd user and group.
# - Inherit supplementary groups from from user typecd.
# - Grant no caps.
# - No new privileges (no_new_privs).
# - Use the typecd seccomp policy.
# - Execute the daemon.
#
# NOTE: We don't add "-e" since we want to receive udev events.
exec minijail0                                                               \
  -i                                                                         \
  --uts                                                                      \
  -N                                                                         \
  -p                                                                         \
  --profile minimalistic-mountns                                             \
  -k 'tmpfs,/run,tmpfs,MS_NODEV|MS_NOEXEC|MS_NOSUID,mode=755,size=10M'       \
  -b /run/dbus                                                               \
  -b /run/udev                                                               \
  -k 'tmpfs,/sys,tmpfs,MS_NODEV|MS_NOEXEC|MS_NOSUID,mode=755,size=10M'       \
  -b /sys/class/typec                                                        \
  -b /sys/devices                                                            \
  -u typecd -g typecd                                                        \
  -G                                                                         \
  -c 0                                                                       \
  -n                                                                         \
  -S /usr/share/policy/typecd-seccomp.policy                                 \
  -- /usr/bin/typecd                                                         \