Make it possible to run ntpd as a non-root user, add ntpd uid and gid.
Code analysis and runtime analysis using truss(8) indicate that the only
privileged operations performed by ntpd are adjusting system time, and
(re-)binding to privileged UDP port 123. These changes add a new mac(4)
policy module, mac_ntpd(4), which grants just those privileges to any
process running with uid 123.
This also adds a new user and group, ntpd:ntpd, (uid:gid 123:123), and makes
them the owner of the /var/db/ntp directory, so that it can be used as a
location where the non-privileged daemon can write files such as the
driftfile, and any optional logfile or stats files.
Because there are so many ways to configure ntpd, the question of how to
configure it to run without root privs can be a bit complex, so that will be
addressed in a separate commit. These changes are just what's required to
grant the limited subset of privs to ntpd, and the small change to ntpd to
prevent it from exiting with an error if running as non-root.
Differential Revision: https://reviews.freebsd.org/D16281
2018-07-19 23:55:29 +00:00
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.\" Copyright (c) 2018 Ian Lepore <ian@FreeBSD.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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2018-07-20 16:06:44 +00:00
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.Dd July 20, 2018
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Make it possible to run ntpd as a non-root user, add ntpd uid and gid.
Code analysis and runtime analysis using truss(8) indicate that the only
privileged operations performed by ntpd are adjusting system time, and
(re-)binding to privileged UDP port 123. These changes add a new mac(4)
policy module, mac_ntpd(4), which grants just those privileges to any
process running with uid 123.
This also adds a new user and group, ntpd:ntpd, (uid:gid 123:123), and makes
them the owner of the /var/db/ntp directory, so that it can be used as a
location where the non-privileged daemon can write files such as the
driftfile, and any optional logfile or stats files.
Because there are so many ways to configure ntpd, the question of how to
configure it to run without root privs can be a bit complex, so that will be
addressed in a separate commit. These changes are just what's required to
grant the limited subset of privs to ntpd, and the small change to ntpd to
prevent it from exiting with an error if running as non-root.
Differential Revision: https://reviews.freebsd.org/D16281
2018-07-19 23:55:29 +00:00
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.Dt MAC_NTPD 4
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.Os
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.Sh NAME
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.Nm mac_ntpd
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.Nd "policy allowing ntpd to run as non-root user"
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.Sh SYNOPSIS
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To compile the ntpd policy into your kernel, place the following lines
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in your kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "options MAC"
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.Cd "options MAC_NTPD"
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.Ed
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.Pp
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Alternately, to load the ntpd policy module at boot time,
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place the following line in your kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "options MAC"
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.Ed
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.Pp
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and in
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.Xr loader.conf 5 :
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2018-07-20 16:06:44 +00:00
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.Bd -literal -offset indent
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mac_ntpd_load="YES"
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.Ed
|
Make it possible to run ntpd as a non-root user, add ntpd uid and gid.
Code analysis and runtime analysis using truss(8) indicate that the only
privileged operations performed by ntpd are adjusting system time, and
(re-)binding to privileged UDP port 123. These changes add a new mac(4)
policy module, mac_ntpd(4), which grants just those privileges to any
process running with uid 123.
This also adds a new user and group, ntpd:ntpd, (uid:gid 123:123), and makes
them the owner of the /var/db/ntp directory, so that it can be used as a
location where the non-privileged daemon can write files such as the
driftfile, and any optional logfile or stats files.
Because there are so many ways to configure ntpd, the question of how to
configure it to run without root privs can be a bit complex, so that will be
addressed in a separate commit. These changes are just what's required to
grant the limited subset of privs to ntpd, and the small change to ntpd to
prevent it from exiting with an error if running as non-root.
Differential Revision: https://reviews.freebsd.org/D16281
2018-07-19 23:55:29 +00:00
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.Sh DESCRIPTION
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The
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.Nm
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policy grants any process running as user
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.Sq ntpd
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(uid 123) the privileges needed to manipulate
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system time, and to (re-)bind to the privileged NTP port.
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.Pp
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When
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.Xr ntpd 8
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is started with
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2018-07-20 16:06:44 +00:00
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.Sq Fl u Ar <user>[:group]
|
Make it possible to run ntpd as a non-root user, add ntpd uid and gid.
Code analysis and runtime analysis using truss(8) indicate that the only
privileged operations performed by ntpd are adjusting system time, and
(re-)binding to privileged UDP port 123. These changes add a new mac(4)
policy module, mac_ntpd(4), which grants just those privileges to any
process running with uid 123.
This also adds a new user and group, ntpd:ntpd, (uid:gid 123:123), and makes
them the owner of the /var/db/ntp directory, so that it can be used as a
location where the non-privileged daemon can write files such as the
driftfile, and any optional logfile or stats files.
Because there are so many ways to configure ntpd, the question of how to
configure it to run without root privs can be a bit complex, so that will be
addressed in a separate commit. These changes are just what's required to
grant the limited subset of privs to ntpd, and the small change to ntpd to
prevent it from exiting with an error if running as non-root.
Differential Revision: https://reviews.freebsd.org/D16281
2018-07-19 23:55:29 +00:00
|
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|
on the command line, it performs all initializations requiring root
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|
privileges, then drops root privileges by switching to the given user id.
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|
From that point on, the only privileges it requires are the ability
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|
to manipulate system time, and the ability to re-bind a UDP socket
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|
to the NTP port (port 123) after a network interface change.
|
2018-07-20 16:06:44 +00:00
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.Pp
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|
With the
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.Nm
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policy active, it may also be possible to start ntpd as a non-root user,
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because the default ntpd options don't require any additional root
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|
|
privileges beyond those granted by the policy.
|
Make it possible to run ntpd as a non-root user, add ntpd uid and gid.
Code analysis and runtime analysis using truss(8) indicate that the only
privileged operations performed by ntpd are adjusting system time, and
(re-)binding to privileged UDP port 123. These changes add a new mac(4)
policy module, mac_ntpd(4), which grants just those privileges to any
process running with uid 123.
This also adds a new user and group, ntpd:ntpd, (uid:gid 123:123), and makes
them the owner of the /var/db/ntp directory, so that it can be used as a
location where the non-privileged daemon can write files such as the
driftfile, and any optional logfile or stats files.
Because there are so many ways to configure ntpd, the question of how to
configure it to run without root privs can be a bit complex, so that will be
addressed in a separate commit. These changes are just what's required to
grant the limited subset of privs to ntpd, and the small change to ntpd to
prevent it from exiting with an error if running as non-root.
Differential Revision: https://reviews.freebsd.org/D16281
2018-07-19 23:55:29 +00:00
|
|
|
.Pp
|
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|
|
.Ss Privileges Granted
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|
|
The exact set of kernel privileges granted to any process running
|
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|
|
|
with the configured uid is:
|
|
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|
|
.Bl -inset -compact -offset indent
|
2018-07-20 16:06:44 +00:00
|
|
|
.It Dv PRIV_ADJTIME
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|
.It Dv PRIV_CLOCK_SETTIME
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.It Dv PRIV_NTP_ADJTIME
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.It Dv PRIV_NETINET_RESERVEDPORT
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|
|
.It Dv PRIV_NETINET_REUSEPORT
|
Make it possible to run ntpd as a non-root user, add ntpd uid and gid.
Code analysis and runtime analysis using truss(8) indicate that the only
privileged operations performed by ntpd are adjusting system time, and
(re-)binding to privileged UDP port 123. These changes add a new mac(4)
policy module, mac_ntpd(4), which grants just those privileges to any
process running with uid 123.
This also adds a new user and group, ntpd:ntpd, (uid:gid 123:123), and makes
them the owner of the /var/db/ntp directory, so that it can be used as a
location where the non-privileged daemon can write files such as the
driftfile, and any optional logfile or stats files.
Because there are so many ways to configure ntpd, the question of how to
configure it to run without root privs can be a bit complex, so that will be
addressed in a separate commit. These changes are just what's required to
grant the limited subset of privs to ntpd, and the small change to ntpd to
prevent it from exiting with an error if running as non-root.
Differential Revision: https://reviews.freebsd.org/D16281
2018-07-19 23:55:29 +00:00
|
|
|
.El
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.Pp
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.Ss Runtime Configuration
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|
The following
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.Xr sysctl 8
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|
MIBs are available for fine-tuning this MAC policy.
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All
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.Xr sysctl 8
|
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|
variables can also be set as
|
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|
|
.Xr loader 8
|
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|
tunables in
|
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|
|
.Xr loader.conf 5 .
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|
.Bl -tag -width indent
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|
.It Va security.mac.ntpd.enabled
|
|
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Enable the
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.Nm
|
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|
policy.
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(Default: 1).
|
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.It Va security.mac.ntpd.uid
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|
The numeric uid of the ntpd user.
|
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|
(Default: 123).
|
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.El
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|
.Sh SEE ALSO
|
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|
.Xr mac 4 ,
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.Xr ntpd 8
|
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|
|
.Sh HISTORY
|
|
|
|
|
MAC first appeared in
|
|
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|
|
.Fx 5.0
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|
and
|
|
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|
|
.Nm
|
|
|
|
|
first appeared in
|
|
|
|
|
.Fx 12.0 .
|