#!/usr/bin/env nft -f

################################################################################
#
# Configuration for nftables firewall under Linux.
#
# /etc/nftables/inet-filter
#
# More info: https://www.librobert.net/book/internet
#
################################################################################
#
# Copyright (c) 2019 Robert LA LAU < https://www.librobert.net/ >
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice,
#    this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its contributors
#    may be used to endorse or promote products derived from this software
#    without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
################################################################################

flush ruleset

define interface = "enp1s0"

table inet filter {
	set tcp_ok {
		type inet_service
	}

	set udp_ok {
		type inet_service
	}

	set trusted {
		type ipv4_addr
	}

	set filter {
		type ipv4_addr
	}

	set martians {
		type ipv4_addr
		flags constant, interval
		elements = {
			0.0.0.0/8,
			127.0.0.0/8,
			172.16.0.0/12,
			192.0.0.0/24,
			192.0.2.0/24,
			192.168.0.0/16,
			198.18.0.0/15,
			198.51.100.0/24,
			203.0.113.0/24
		}
	}

	chain input {
		type filter hook input priority 0
		policy drop
		ct state established,related accept
		iif lo accept
		iifname $interface ip saddr @trusted accept
		ip saddr @filter drop
		ip saddr @martians drop
		ip daddr @martians drop
		iifname $interface tcp dport 22 accept
		iifname $interface tcp dport @tcp_ok accept
		iifname $interface udp dport @udp_ok accept
	}
}