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2.3.2.1 Ensure systemd-timesyncd configured with authorized timeserver

Audit#

Run the following command to verify the NTP and/or FallbackNTP option is set to local site approved authoritative time server(s): 

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#!/usr/bin/env bash
{
a_output=() a_output2=() a_output3=() a_out=() a_out2=() a_parlist=("NTP=[^#\n\r]+" "FallbackNTP=[^#\n\r]+")
l_analyze_cmd="$(readlink -f /bin/systemd-analyze)"
l_systemd_config_file="/etc/systemd/timesyncd.conf"
f_config_file_parameter_chk()
{
l_used_parameter_setting=""
while IFS= read -r l_file; do
l_file="$(tr -d '# ' <<< "$l_file")"
l_used_parameter_setting="$(grep -PHs -- '^\h*'"$l_parameter_name"'\b' "$l_file" | tail -n 1)"
[ -n "$l_used_parameter_setting" ] && break
done < <($l_analyze_cmd cat-config "$l_systemd_config_file" | tac | grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b')
if [ -n "$l_used_parameter_setting" ]; then
while IFS=: read -r l_file_name l_file_parameter; do
while IFS="=" read -r l_file_parameter_name l_file_parameter_value; do
if grep -Pq -- "$l_parameter_value" <<< "$l_file_parameter_value"; then
a_out+=(" - Parameter: \"${l_file_parameter_name// /}\"" \"correctly set to: \"${l_file_parameter_value// /}\"" \"in the file:\"$l_file_name\"")
else
a_out2+=(" - Parameter: \"${l_file_parameter_name// /}\"" \"incorrectly set to: \"${l_file_parameter_value// /}\"" \"in the file:\"$l_file_name\"" \"Should be set to: \"$l_value_out\"")
fi
done <<< "$l_file_parameter"
done <<< "$l_used_parameter_setting"
else
a_out2+=(" - Parameter: \"$l_parameter_name\" is not set in an included file" \"*** Note: \"$l_parameter_name\" May be set in a file that's ignored by load procedure ***")
fi
}
while IFS="=" read -r l_parameter_name l_parameter_value; do # Assess and check parameters
l_parameter_name="${l_parameter_name// /}"; l_parameter_value="${l_parameter_value// /}"
l_value_out="${l_parameter_value//-/ through }"; l_value_out="${l_value_out//|/ or }"
l_value_out="$(tr -d '(){}' <<< "$l_value_out")"
f_config_file_parameter_chk
done < <(printf '%s\n' "${a_parlist[@]}")
if [ "${#a_out[@]}" -gt 0 ]; then
a_output+=("${a_out[@]}"); [ "${#a_out2[@]}" -gt 0 ] && a_output3+=(" ** INFO: **" "${a_out2[@]}")
else
a_output2+=("${a_out2[@]}")
fi
if [ "${#a_output2[@]}" -le 0 ]; then
printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" ""[ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "${a_output3[@]}"
else
printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" ""
fi
}

Note: Please ensure the output for NTP and/or FallbackNTP is in accordance with local site policy. The timeservers in the example output are provided as an example of possible timeservers and they may not follow local site policy. 

## Remediation
Set **NTP** and/or **FallbackNPT** parameters to local site approved authoritative time server(s) in **/etc/systemd/timesyncd.conf** or a file in **/etc/systemd/timesyncd.conf.d/** ending in **.conf** in the **[Time]** section:
Example file:
```bash
[Time]
NTP=time.nist.gov # Uses the generic name for NIST's time servers
FallbackNTP=time-a-g.nist.gov time-b-g.nist.gov time-c-g.nist.gov # Space separated list of NIST time servers

Example script to create the systemd drop-in configuration file: 

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#!/usr/bin/env bash
{
a_settings=("NTP=time.nist.gov" "FallbackNTP=time-a-g.nist.gov time-b-g.nist.gov time-c-g.nist.gov")
[ ! -d /etc/systemd/timesyncd.conf.d/ ] && mkdir /etc/systemd/timesyncd.conf.d/
if grep -Psq -- '^\h*\[Time\]' /etc/systemd/timesyncd.conf.d/60-timesyncd.conf; then
printf '%s\n' "" "${a_settings[@]}" >> /etc/systemd/timesyncd.conf.d/60-timesyncd.conf
else
printf '%s\n' "" "[Time]" "${a_settings[@]}" >> /etc/systemd/timesyncd.conf.d/60-timesyncd.conf
fi
}

Note: If this setting appears in a canonically later file, or later in the same file, the setting will be overwritten

Run to following command to update the parameters in the service: 

# systemctl reload-or-restart systemd-timesyncd

Default Value: 

#NTP=
#FallbackNTP=