The Ubuntu operating system must, for networked systems, compare internal information system clocks at least every 24 hours with a server which is synchronized to one of the redundant United States Naval Observatory (USNO) time servers, or a time server designated for the appropriate DoD network (NIPRNet/SIPRNet), and/or the Global Positioning System (GPS).

STIG ID: UBTU-20-010435  |  SRG: SRG-OS-000355-GPOS-00143 |  Severity: medium |  CCI: CCI-001891 |  Vulnerability Id: V-238356 | 

Vulnerability Discussion

Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate.

Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network.

Organizations should consider endpoints that may not have regular access to the authoritative time server (e.g., mobile, teleworking, and tactical endpoints).

Check

If the system is not networked, this requirement is Not Applicable.

The system clock must be configured to compare the system clock at least every 24 hours to the authoritative time source.

Check the value of "maxpoll" in the "/etc/chrony/chrony.conf" file with the following command:

$ sudo grep maxpoll /etc/chrony/chrony.conf
server tick.usno.navy.mil iburst maxpoll 16

If the "maxpoll" option is set to a number greater than 16 or the line is commented out, this is a finding.

Verify that the "chrony.conf" file is configured to an authoritative DoD time source by running the following command:

$ grep -i server /etc/chrony/chrony.conf
server tick.usno.navy.mil iburst maxpoll 16
server tock.usno.navy.mil iburst maxpoll 16
server ntp2.usno.navy.mil iburst maxpoll 16

If the parameter "server" is not set, is not set to an authoritative DoD time source, or is commented out, this is a finding.

Fix

If the system is not networked, this requirement is Not Applicable.

To configure the system clock to compare the system clock at least every 24 hours to the authoritative time source, edit the "/etc/chrony/chrony.conf" file. Add or correct the following lines, by replacing "[source]" in the following line with an authoritative DoD time source:

server [source] iburst maxpoll = 16

If the "chrony" service was running and the value of "maxpoll" or "server" was updated, the service must be restarted using the following command:

$ sudo systemctl restart chrony.service
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