The Red Hat Enterprise Linux operating system must, for networked systems, synchronize clocks with a server that is synchronized to one of the redundant United States Naval Observatory (USNO) time servers, a time server designated for the appropriate DoD network (NIPRNet/SIPRNet), and/or the Global Positioning System (GPS).

STIG ID: RHEL-07-040500  |  SRG: SRG-OS-000355-GPOS-00143 |  Severity: medium |  CCI: CCI-001891,CCI-002046 |  Vulnerability Id: V-204603 | 

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).

Satisfies: SRG-OS-000355-GPOS-00143, SRG-OS-000356-GPOS-00144

Check

Check to see if NTP is running in continuous mode:

# ps -ef | grep ntp

If NTP is not running, check to see if "chronyd" is running in continuous mode:

# ps -ef | grep chronyd

If NTP or "chronyd" is not running, this is a finding.

If the NTP process is found, then check the "ntp.conf" file for the "maxpoll" option setting:

# grep maxpoll /etc/ntp.conf

server 0.rhel.pool.ntp.org 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.

If the file does not exist, check the "/etc/cron.daily" subdirectory for a crontab file controlling the execution of the "ntpd -q" command.

# grep -i "ntpd -q" /etc/cron.daily/*
# ls -al /etc/cron.* | grep ntp

ntp

If a crontab file does not exist in the "/etc/cron.daily" that executes the "ntpd -q" command, this is a finding.

If the "chronyd" process is found, then check the "chrony.conf" file for the "maxpoll" option setting:

# grep maxpoll /etc/chrony.conf

server 0.rhel.pool.ntp.org iburst maxpoll 16

If the option is not set or the line is commented out, this is a finding.

Fix

Edit the "/etc/ntp.conf" or "/etc/chrony.conf" file and add or update an entry to define "maxpoll" to "16" as follows:

server 0.rhel.pool.ntp.org iburst maxpoll 16

If NTP was running and "maxpoll" was updated, the NTP service must be restarted:

# systemctl restart ntpd

If NTP was not running, it must be started:

# systemctl start ntpd

If "chronyd" was running and "maxpoll" was updated, the service must be restarted:

# systemctl restart chronyd.service

If "chronyd" was not running, it must be started:

# systemctl start chronyd.service
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