graphene-os-server-infrastr.../nftables-ns1.conf

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#!/usr/bin/nft -f
flush ruleset
table inet filter {
define ip-allowlist-ssh = {
127.0.0.1,
}
define ip6-allowlist-ssh = {
::1,
}
set ip-connlimit-ssh {
type ipv4_addr
flags dynamic
}
set ip6-connlimit-ssh {
type ipv6_addr
flags dynamic
}
set ip-connlimit-main {
type ipv4_addr
flags dynamic
}
set ip6-connlimit-main {
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)
#
# ordered after accepting loopback to permit using external IPs via loopback
fib daddr . iif type != { local, broadcast, multicast } counter drop
udp dport 53 notrack accept
# handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
tcp dport { 22, 53, 80, 443, 853 } tcp flags syn limit rate 1024/second burst 128 packets accept
tcp dport { 22, 53, 80, 443, 853 } tcp flags syn counter notrack accept
meta l4proto { icmp, ipv6-icmp } notrack accept
}
chain input {
type filter hook input priority filter
policy drop
tcp dport { 22, 53, 80, 443, 853 } goto input-tcp-service
iif lo accept
udp dport 53 accept
meta l4proto { icmp, ipv6-icmp } accept
ct state vmap { new : goto graceful-reject, established : accept, related : accept }
}
chain input-tcp-service {
iif lo goto input-tcp-service-loopback
# for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
ct state vmap { new : goto input-tcp-service-new, established : goto input-tcp-service-established, related : accept }
tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
synproxy mss 1460 wscale 7 timestamp sack-perm
}
chain input-tcp-service-new {
tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
accept
}
# add connections established without synproxy to connection limit sets with limits enforced
chain input-tcp-service-established {
ct mark 0x1 accept
tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } add @ip-connlimit-main { ip saddr ct count over 16 } counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } add @ip6-connlimit-main { ip6 saddr and ffff:ffff:ffff:ffff:: ct count over 16 } counter reject with tcp reset
ct mark set 0x1 accept
}
# add connections established with synproxy to connection limit sets with limits enforced
chain input-tcp-service-loopback {
tcp flags != syn accept
tcp dport 22 ip saddr != $ip-allowlist-ssh add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
tcp dport 22 ip6 saddr != $ip6-allowlist-ssh add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } add @ip-connlimit-main { ip saddr ct count over 16 } counter reject with tcp reset
tcp dport { 53, 80, 443, 853 } add @ip6-connlimit-main { ip6 saddr and ffff:ffff:ffff:ffff:: ct count over 16 } counter reject with tcp reset
ct mark set 0x1 accept
}
chain forward {
type filter hook forward priority filter
policy drop
}
chain output-raw {
type filter hook output priority raw
oif lo notrack accept
udp sport 53 notrack accept
meta l4proto { icmp, ipv6-icmp } notrack accept
}
chain output {
type filter hook output priority filter
oif lo goto output-loopback
skuid != { root, systemd-network, unbound, chrony, http, powerdns, geoipupdate } counter goto graceful-reject
}
chain output-loopback {
skuid unbound meta l4proto { tcp, udp } th sport 53 th dport >= 1024 accept
skuid { chrony, geoipupdate } meta l4proto { tcp, udp } th sport >= 1024 th dport 53 accept
skuid powerdns meta l4proto tcp th sport 54 th dport >= 1024 accept
skuid http meta l4proto tcp th sport >= 1024 th dport 54 accept
skuid powerdns meta l4proto tcp th sport 81 th dport >= 1024 accept
skuid != root counter goto graceful-reject
accept
}
chain graceful-reject {
meta l4proto udp reject
meta l4proto tcp reject with tcp reset
reject
}
}