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

3 files changed, 3 insertions, 1 deletions

diff --git a/etc/group b/etc/group
index c20f1d93dd3c..1a409312d69d 100644
--- a/etc/group
+++ b/etc/group
@@ -29,6 +29,7 @@ dialer:*:68:
 network:*:69:
 audit:*:77:
 www:*:80:
+ntpd:*:123:
 _ypldap:*:160:
 hast:*:845:
 nogroup:*:65533:
diff --git a/etc/master.passwd b/etc/master.passwd
index 4b0f3645cd3d..a7903f08a576 100644
--- a/etc/master.passwd
+++ b/etc/master.passwd
@@ -22,6 +22,7 @@ uucp:*:66:66::0:0:UUCP pseudo-user:/var/spool/uucppublic:/usr/local/libexec/uucp
 pop:*:68:6::0:0:Post Office Owner:/nonexistent:/usr/sbin/nologin
 auditdistd:*:78:77::0:0:Auditdistd unprivileged user:/var/empty:/usr/sbin/nologin
 www:*:80:80::0:0:World Wide Web Owner:/nonexistent:/usr/sbin/nologin
+ntpd:*:123:123::0:0:NTP Daemon:/var/db/ntp:/usr/sbin/nologin
 _ypldap:*:160:160::0:0:YP LDAP unprivileged user:/var/empty:/usr/sbin/nologin
 hast:*:845:845::0:0:HAST unprivileged user:/var/empty:/usr/sbin/nologin
 nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/usr/sbin/nologin
diff --git a/etc/mtree/BSD.var.dist b/etc/mtree/BSD.var.dist
index e522549fffd0..fc6021aad9ac 100644
--- a/etc/mtree/BSD.var.dist
+++ b/etc/mtree/BSD.var.dist
@@ -46,7 +46,7 @@
         ..
         ipf             mode=0700
         ..
-        ntp             mode=0700
+        ntp             uname=ntpd gname=ntpd
         ..
         pkg
         ..