Ensure nftables Rules are Permanent

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Description

nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames. The nftables service reads the /etc/nftables.conf file for a nftables file or files to include in the nftables ruleset. A nftables ruleset containing the input, forward, and output base chains allow network traffic to be filtered.

Rationale

Changes made to nftables ruleset only affect the live system, you will also need to configure the nftables ruleset to apply on boot

Remediation

Shell script

The following script can be run on the host to remediate the issue.

#!/bin/bash

# Remediation is applicable only in certain platforms
if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q installed ); then

var_nftables_master_config_file='/etc/nftables.conf'


var_nftables_family='inet'


if [ ! -f "${var_nftables_master_config_file}" ]; then
    touch "${var_nftables_master_config_file}"
fi

nft list ruleset > "/etc/${var_nftables_family}-filter.rules"

grep -qxF 'include "/etc/'"${var_nftables_family}"'-filter.rules"' "${var_nftables_master_config_file}" \
    || echo 'include "/etc/'"${var_nftables_family}"'-filter.rules"' >> "${var_nftables_master_config_file}"

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