Configure server restrictions for ntpd

An XCCDF Rule

Description

ntpd is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on NTP can be found at http://www.ntp.org. ntp can be configured to be a client and/or a server. To ensure that ntpd implements correct server restrictions, make sure that the following lines exist in the file /etc/ntpd.conf:

restrict -4 default kod nomodify notrap nopeer noquery

restrict -6 default kod nomodify notrap nopeer noquery

This recommendation only applies if ntp is in use on the system.

Rationale

If ntp is in use on the system proper configuration is vital to ensuring time synchronization is working properly.

ID: xccdf_org.ssgproject.content_rule_ntpd_configure_restrictions
Severity: Medium
References: 2.1.4.1
Updated: about 1 year ago

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ] && { dpkg-query --show --showformat='${db:Status-Status}\n' 'ntp' 2>/dev/null | grep -q installed; }; then

if [ -e "/etc/ntp.conf" ] ; then
    
    LC_ALL=C sed -i "/^\s*restrict \-4\s\+/Id" "/etc/ntp.conf"else
    touch "/etc/ntp.conf"
fi
# make sure file has newline at the end
sed -i -e '$a\' "/etc/ntp.conf"

cp "/etc/ntp.conf" "/etc/ntp.conf.bak"
# Insert at the end of the file
printf '%s\n' "restrict -4 default kod nomodify notrap nopeer noquery" >> "/etc/ntp.conf"
# Clean up after ourselves.
rm "/etc/ntp.conf.bak"
if [ -e "/etc/ntp.conf" ] ; then
    
    LC_ALL=C sed -i "/^\s*restrict \-6\s\+/Id" "/etc/ntp.conf"
else
    touch "/etc/ntp.conf"
fi
# make sure file has newline at the end
sed -i -e '$a\' "/etc/ntp.conf"

cp "/etc/ntp.conf" "/etc/ntp.conf.bak"
# Insert at the end of the file
printf '%s\n' "restrict -6 default kod nomodify notrap nopeer noquery" >> "/etc/ntp.conf"
# Clean up after ourselves.
rm "/etc/ntp.conf.bak"

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Configure server restrictions for ntpd

Description

Rationale

Remediation - Shell Script