freebsd-dev/etc/rc.d/ntpd
Ian Lepore d11f4dfd21 Automatically run ntpd as non-root when possible.
Ntpd needs only a subset of full root privileges to do its job. Specifically
it needs the ability to manipulate system time, and to re-bind to a
privileged UDP port after interface changes. The mac_ntpd(4) policy module
(see r336525) can grant these privs.

These changes detect the availability of mac_ntpd(4). If enabled, and if the
ntpd configuration is fairly vanilla, it automatically runs ntpd as the
non-root user 'ntpd' (uid 123). "Vanilla" means the config doesn't include
command line or ntp.conf options changing the location of files or using any
files/dirs likely to be inaccessible to user ntpd.  Ntpd can still run as
non-root when using such options, but the admin must ensure all required
files and dirs are accessible, and then set ntpd_user=ntpd in rc.conf.

Note that these changes also address PR 199127 by using the command_args
technique suggested in the patch. They also tangentially address PR 113552,
which is primarily about inconsistent filenames in documentation, but some
of the inconsistancy was caused by old code in rc.d/ntpd which is leftover
from the intial import from netbsd. There was code to do chroot setup which
required the use of the netbsd clockctl(4) device; that code never had any
effect on freebsd, because we lack that device and don't build ntpd with the
options that would allow using it.

PR:		113552 199127
Relnotes:	yes
Differential Revision:	https://reviews.freebsd.org/D16050
2018-07-20 13:59:29 +00:00

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#!/bin/sh
#
# $FreeBSD$
#
# PROVIDE: ntpd
# REQUIRE: DAEMON ntpdate FILESYSTEMS devfs
# BEFORE: LOGIN
# KEYWORD: nojail shutdown
. /etc/rc.subr
name="ntpd"
desc="Network Time Protocol daemon"
rcvar="ntpd_enable"
command="/usr/sbin/${name}"
extra_commands="fetch needfetch"
fetch_cmd="ntpd_fetch_leapfile"
needfetch_cmd="ntpd_needfetch_leapfile"
start_precmd="ntpd_precmd"
_ntp_tmp_leapfile="/var/run/ntpd.leap-seconds.list"
_ntp_default_dir="/var/db/ntp"
_ntp_default_driftfile="${_ntp_default_dir}/ntpd.drift"
_ntp_old_driftfile="/var/db/ntpd.drift"
pidfile="${_ntp_default_dir}/${name}.pid"
load_rc_config $name
can_run_nonroot()
{
# If the admin set what uid to use, we don't change it.
if [ -n "${ntpd_user}" ]; then
return 1
fi
# If the admin set any command line options involving files, we
# may not be able to access them as user ntpd.
case "${rc_flags}" in
*-f* | *--driftfile* | *-i* | *--jaildir* | \
*-k* | *--keyfile* | *-l* | *--logfile* | \
*-p* | *--pidfile* | *-s* | *--statsdir* )
return 1;;
esac
# If the admin set any options in ntp.conf involving files,
# we may not be able to access them as user ntpd.
local fileopts="^[ \t]*crypto|^[ \t]*driftfile|^[ \t]*key|^[ \t]*logfile|^[ \t]*statsdir"
grep -E -q "${fileopts}" "${ntpd_config}" && return 1
# Try to set up the the MAC ntpd policy so ntpd can run with reduced
# privileges. Detect whether MAC is compiled into the kernel, load
# the policy module if not already present, then check whether the
# policy has been disabled via tunable or sysctl.
[ -n "$(sysctl -qn security.mac.version)" ] || return 1
sysctl -qn security.mac.ntpd >/dev/null || kldload -qn mac_ntpd || return 1
[ "$(sysctl -qn security.mac.ntpd.enabled)" == "1" ] || return 1
# On older existing systems, the ntp dir may by owned by root, change
# it to ntpd to give the daemon create/write access to the driftfile.
if [ "$(stat -f %u ${_ntp_default_dir})" = "0" ]; then
chown ntpd:ntpd "${_ntp_default_dir}" || return 1
chmod 0755 "${_ntp_default_dir}" || return 1
logger -s -t "rc.d/ntpd" -p daemon.notice \
"${_ntp_default_dir} updated to owner ntpd:ntpd, mode 0755"
fi
# If the driftfile exists in the standard location for older existing
# systems, move it into the ntp dir and fix the ownership if we can.
if [ -f "${_ntp_old_driftfile}" ] && [ ! -L "${_ntp_old_driftfile}" ]; then
mv "${_ntp_old_driftfile}" "${_ntp_default_driftfile}" &&
chown ntpd:ntpd "${_ntp_default_driftfile}" || return 1
logger -s -t "rc.d/ntpd" -p daemon.notice \
"${_ntp_default_driftfile} updated to owner ntpd:ntpd"
logger -s -t "rc.d/ntpd" -p daemon.notice \
"${_ntp_old_driftfile} moved to ${_ntp_default_driftfile}"
fi
}
ntpd_precmd()
{
local driftopt
# If we can run as a non-root user, switch uid to ntpd and use the
# new default location for the driftfile inside the ntpd-owned dir.
# Otherwise, figure out what to do about the driftfile option. If set
# by the admin, we don't add the option. If the file exists in the old
# default location we use that, else we use the new default location.
if can_run_nonroot; then
_user="ntpd"
driftopt="-f ${_ntp_default_driftfile}"
elif [ -z "${rc_flags##*-f*}" ] ||
[ -z "${rc_flags##*--driftfile*}" ] ||
grep -q "^[ \t]*driftfile" "${ntpd_config}"; then
driftopt="" # admin set the option, we don't need to add it.
elif [ -f "${_ntp_old_driftfile}" ]; then
driftopt="-f ${_ntp_old_driftfile}"
else
driftopt="-f ${_ntp_default_driftfile}"
fi
# Set command_args based on the various config vars.
command_args="-p ${pidfile} -c ${ntpd_config} ${driftopt}"
if checkyesno ntpd_sync_on_start; then
command_args="${command_args} -g"
fi
# Make sure the leapfile is ready to use.
ntpd_init_leapfile
if [ ! -f "${ntp_db_leapfile}" ]; then
ntpd_fetch_leapfile
fi
}
current_ntp_ts() {
# Seconds between 1900-01-01 and 1970-01-01
# echo $(((70*365+17)*86400))
ntp_to_unix=2208988800
echo $(($(date -u +%s)+$ntp_to_unix))
}
get_ntp_leapfile_ver() {
# Leapfile update date (version number).
expr "$(awk '$1 == "#$" { print $2 }' "$1" 2>/dev/null)" : \
'^\([1-9][0-9]*\)$' \| 0
}
get_ntp_leapfile_expiry() {
# Leapfile expiry date.
expr "$(awk '$1 == "#@" { print $2 }' "$1" 2>/dev/null)" : \
'^\([1-9][0-9]*\)$' \| 0
}
ntpd_init_leapfile() {
# Refresh working leapfile with an invalid hash due to
# FreeBSD id header. Ntpd will ignore leapfiles with a
# mismatch hash. The file must be the virgin file from
# the source.
if [ ! -f $ntp_db_leapfile ]; then
cp -p $ntp_src_leapfile $ntp_db_leapfile
fi
}
ntpd_needfetch_leapfile() {
local rc verbose
if checkyesno ntp_leapfile_fetch_verbose; then
verbose=echo
else
verbose=:
fi
ntp_ver_no_src=$(get_ntp_leapfile_ver $ntp_src_leapfile)
ntp_expiry_src=$(get_ntp_leapfile_expiry $ntp_src_leapfile)
ntp_ver_no_db=$(get_ntp_leapfile_ver $ntp_db_leapfile)
ntp_expiry_db=$(get_ntp_leapfile_expiry $ntp_db_leapfile)
$verbose ntp_src_leapfile version is $ntp_ver_no_src expires $ntp_expiry_src
$verbose ntp_db_leapfile version is $ntp_ver_no_db expires $ntp_expiry_db
if [ "$ntp_ver_no_src" -gt "$ntp_ver_no_db" -o \
"$ntp_ver_no_src" -eq "$ntp_ver_no_db" -a \
"$ntp_expiry_src" -gt "$ntp_expiry_db" ]; then
$verbose replacing $ntp_db_leapfile with $ntp_src_leapfile
cp -p $ntp_src_leapfile $ntp_db_leapfile
ntp_ver_no_db=$ntp_ver_no_src
else
$verbose not replacing $ntp_db_leapfile with $ntp_src_leapfile
fi
ntp_leapfile_expiry_seconds=$((ntp_leapfile_expiry_days*86400))
ntp_leap_expiry=$(get_ntp_leapfile_expiry $ntp_db_leapfile)
ntp_leap_fetch_date=$((ntp_leap_expiry-ntp_leapfile_expiry_seconds))
if [ $(current_ntp_ts) -ge $ntp_leap_fetch_date ]; then
$verbose Within ntp leapfile expiry limit, initiating fetch
# Return code 0: ntp leapfile fetch needed
return 0
fi
# Return code 1: ntp leapfile fetch not needed
return 1
}
ntpd_fetch_leapfile() {
if checkyesno ntp_leapfile_fetch_verbose; then
verbose=echo
else
verbose=:
fi
if ntpd_needfetch_leapfile ; then
for url in $ntp_leapfile_sources ; do
$verbose fetching $url
fetch $ntp_leapfile_fetch_opts -o $_ntp_tmp_leapfile $url && break
done
ntp_ver_no_tmp=$(get_ntp_leapfile_ver $_ntp_tmp_leapfile)
ntp_expiry_tmp=$(get_ntp_leapfile_expiry $_ntp_tmp_leapfile)
if [ "$ntp_expiry_tmp" -gt "$ntp_expiry_db" -o \
"$ntp_expiry_tmp" -eq "$ntp_expiry_db" -a \
"$ntp_ver_no_tmp" -gt "$ntp_ver_no_db" ]; then
$verbose using $url as $ntp_db_leapfile
mv -f $_ntp_tmp_leapfile $ntp_db_leapfile ||
$verbose "warning: cannot replace $ntp_db_leapfile (read-only fs?)"
else
$verbose using existing $ntp_db_leapfile
fi
fi
}
run_rc_command "$1"