biod/init/bio_crypto_init.conf

# Copyright 2018 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   "Binary to program bio sensors with TPM seed."
author        "chromium-os-dev@chromium.org"

start on starting boot-services

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

pre-start script
  mkdir -m 755 -p "${LOG_DIR}"
  chown biod:biod "${LOG_DIR}"
  if [ -c "${FP_DEV}" ]; then
    # Since we are running before udev executes, we need to manually make the
    # dev node accessible inside the sandbox.
    chown root:biod "${FP_DEV}"
    chmod 660 "${FP_DEV}"
  fi
end script

script
  # Check the existence of ${FP_DEV}.
  if [ ! -c "${FP_DEV}" ]; then
    echo "${FP_DEV} not available, exiting." > "${LOG_DIR}/bio_crypto_init.log"
    exit 0
  fi

  # 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.
  # - Same options as minimalistic-mountns except we do not mount /dev/log
  #   because it doesn't necessarily exist since journald hasn't started yet.
  # - Get a writeable and empty /run tmpfs path.
  # - Mount the /run/biod_seed file.
  # - Get a writeable and empty /var tmpfs path.
  # - Mount the log directory in it.
  # - Mount the FPMCU dev node.
  # - Run as biod user and group.
  # - Inherit supplementary groups from from user biod.
  # - Grant no caps.
  # - No new privileges (no_new_privs).
  # - Use bio_crypto_init seccomp policy.
  # - Execute the binary.
  exec minijail0                                                         \
    --uts                                                                \
    -e                                                                   \
    -l                                                                   \
    -N                                                                   \
    -p                                                                   \
    -v -P /mnt/empty -b / -b /proc -t -r --mount-dev                     \
    -k 'tmpfs,/run,tmpfs,MS_NODEV|MS_NOEXEC|MS_NOSUID,mode=755,size=10M' \
    -b /run/bio_crypto_init,,1                                           \
    -k 'tmpfs,/var,tmpfs,MS_NODEV|MS_NOEXEC|MS_NOSUID,mode=755,size=10M' \
    -b ${LOG_DIR},,1                                                     \
    -b ${FP_DEV}                                                         \
    -u biod -g biod                                                      \
    -G                                                                   \
    -c 0                                                                 \
    -n                                                                   \
    -S /usr/share/policy/bio-crypto-init-seccomp.policy                  \
    -- /usr/bin/bio_crypto_init                                          \
    --log_dir=${LOG_DIR}
end script

# Ensure the /run file is cleaned up in case it still exists.
post-stop script
  rm -f /run/bio_crypto_init/seed
end script