#!/usr/bin/nft -f flush ruleset table inet filter { define ip-allowlist-ssh = { 127.0.0.1, 51.222.156.101, # 0.grapheneos.org 167.114.114.114, # 0.releases.grapheneos.org } define ip6-allowlist-ssh = { ::1, 2607:5300:205:200::29c6, # 0.grapheneos.org 2607:5300:201:3100::6210, # 0.releases.grapheneos.org } set ip-connlimit-ssh { type ipv4_addr flags dynamic } set ip6-connlimit-ssh { type ipv6_addr flags dynamic } chain prerouting-raw { type filter hook prerouting priority raw # drop packets without a reverse path (strict reverse path filtering) fib saddr . iif oif missing counter drop iif lo notrack accept # drop packets to address not configured on incoming interface (strong host model) fib daddr . iif type != { local, broadcast, multicast } counter drop tcp dport { 80, 443 } notrack accept tcp dport 22 tcp flags syn notrack accept meta l4proto { icmp, ipv6-icmp } notrack accept } chain output-raw { type filter hook output priority raw oif lo notrack accept tcp sport { 80, 443 } notrack accept meta l4proto { icmp, ipv6-icmp } notrack accept } chain input { type filter hook input priority filter policy drop iif lo tcp dport 22 tcp flags syn ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } reject with tcp reset iif lo tcp dport 22 tcp flags syn ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } reject with tcp reset iif lo accept tcp dport { 80, 443 } accept meta l4proto { icmp, ipv6-icmp } accept ct state vmap { established : accept, related : accept, new : goto graceful-reject } tcp dport 22 ip saddr @ip-connlimit-ssh reject with tcp reset tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh reject with tcp reset tcp dport 22 synproxy mss 1460 wscale 7 timestamp sack-perm } chain forward { type filter hook forward priority filter policy drop } chain output { type filter hook output priority filter oif lo goto output-internal skuid != { root, systemd-network, unbound, chrony, http } counter goto graceful-reject } chain output-internal { skuid unbound meta l4proto { tcp, udp } th sport 53 th dport >= 1024 accept skuid chrony meta l4proto { tcp, udp } th sport >= 1024 th dport 53 accept skuid != root counter goto graceful-reject accept } chain graceful-reject { meta l4proto udp reject meta l4proto tcp reject with tcp reset reject } }