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CIS Ubuntu 14.04 LTS - 2.2.1.2 Ensure ntp is configured

DevOps & Security
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Verify that NTP is properly configured with restrict options and running as ntp user

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2.2.1.2 Ensure ntp is configured (Scored)

Profile Applicability

  • Level 1 - Server
  • Level 1 - Workstation

Description

ntp 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.

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.

Audit Procedure

Run the following command and verify output matches:

grep "^restrict" /etc/ntp.conf

Expected output:

restrict -4 default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

The -4 in the first line is optional and options after default can appear in any order. Additional restriction lines may exist.

Run the following command and verify remote server is configured properly:

grep "^(server|pool)" /etc/ntp.conf

Expected output:

server <remote-server>

Multiple servers may be configured.

Verify that ntp is configured to run as the ntp user by running the following command:

grep "RUNASUSER=ntp" /etc/init.d/ntp

Expected output:

RUNASUSER=ntp

Expected Result

  • Restrict lines should include default kod nomodify notrap nopeer noquery for both IPv4 and IPv6.
  • At least one remote server or pool should be configured.
  • NTP should run as the ntp user.

Remediation

Add or edit restrict lines in /etc/ntp.conf to match the following:

restrict -4 default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

Add or edit server or pool lines to /etc/ntp.conf as appropriate:

server <remote-server>

Configure ntp to run as the ntp user by adding or editing the /etc/init.d/ntp file:

RUNASUSER=ntp

Default Value

NTP restrict and server settings are not configured by default.

References

  • http://www.ntp.org
  • CIS Controls: 6.1 Use At Least Two Synchronized Time Sources For All Servers And Network Equipment

Profile

  • Level 1 - Server
  • Level 1 - Workstation