131 lines
5.2 KiB
Plaintext
131 lines
5.2 KiB
Plaintext
#!/usr/bin/nft -f
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flush ruleset
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table inet filter {
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set ip-connlimit-ssh {
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type ipv4_addr
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flags dynamic
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}
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set ip6-connlimit-ssh {
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type ipv6_addr
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flags dynamic
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}
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set ip-connlimit-main {
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type ipv4_addr
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flags dynamic
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}
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set ip6-connlimit-main {
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type ipv6_addr
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flags dynamic
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}
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chain prerouting-raw {
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type filter hook prerouting priority raw
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policy drop
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# drop packets without a reverse path (strict reverse path filtering)
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fib saddr . iif oif missing counter drop
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iif lo notrack accept
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# drop packets to address not configured on incoming interface (strong host model)
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#
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# ordered after accepting loopback to permit using external IPs via loopback
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fib daddr . iif type != { local, broadcast, multicast } counter drop
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udp dport 53 notrack accept
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# handle new TCP connections beyond rate limit via synproxy to avoid conntrack table exhaustion
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tcp dport { 22, 53, 80, 443, 853 } tcp flags syn limit rate over 1024/second burst 1024 packets counter notrack accept
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meta l4proto { tcp, udp } accept
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meta l4proto { icmp, ipv6-icmp } notrack accept
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}
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chain input {
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type filter hook input priority filter
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policy drop
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tcp dport { 22, 53, 80, 443, 853 } goto input-tcp-service
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ct state vmap { invalid : drop, established : accept, related : accept, new : drop, untracked: accept }
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}
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chain input-tcp-service {
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iif lo goto input-tcp-service-loopback
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# for synproxy, SYN is untracked and first ACK is invalid which are handled via fallthrough
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ct state vmap { established : goto input-tcp-service-established, related : accept, new : goto input-tcp-service-new }
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tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
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tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
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tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
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tcp dport { 53, 80, 443, 853 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
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synproxy mss 1460 wscale 7 timestamp sack-perm
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}
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chain input-tcp-service-new {
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tcp dport 22 ip saddr @ip-connlimit-ssh counter reject with tcp reset
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tcp dport 22 ip6 saddr and ffff:ffff:ffff:ffff:ffff:: @ip6-connlimit-ssh counter reject with tcp reset
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tcp dport { 53, 80, 443, 853 } ip saddr @ip-connlimit-main counter reject with tcp reset
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tcp dport { 53, 80, 443, 853 } ip6 saddr and ffff:ffff:ffff:ffff:: @ip6-connlimit-main counter reject with tcp reset
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accept
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}
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# add connections established without synproxy to connection limit sets with limits enforced
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chain input-tcp-service-established {
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ct mark 0x1 accept
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tcp dport 22 add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
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tcp dport 22 add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
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tcp dport { 53, 80, 443, 853 } add @ip-connlimit-main { ip saddr ct count over 16 } counter reject with tcp reset
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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
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ct mark set 0x1 accept
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}
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# add connections established with synproxy to connection limit sets with limits enforced
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chain input-tcp-service-loopback {
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tcp flags != syn accept
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tcp dport 22 add @ip-connlimit-ssh { ip saddr ct count over 1 } counter reject with tcp reset
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tcp dport 22 add @ip6-connlimit-ssh { ip6 saddr and ffff:ffff:ffff:ffff:ffff:: ct count over 1 } counter reject with tcp reset
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tcp dport { 53, 80, 443, 853 } add @ip-connlimit-main { ip saddr ct count over 16 } counter reject with tcp reset
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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
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ct mark set 0x1 accept
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}
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chain forward {
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type filter hook forward priority filter
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policy drop
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}
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chain output-raw {
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type filter hook output priority raw
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oif lo goto output-raw-loopback
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skuid != { root, systemd-network, unbound, chrony, http, powerdns, geoipupdate } counter goto graceful-reject
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udp sport 53 notrack accept
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meta l4proto { icmp, ipv6-icmp } notrack accept
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}
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chain output-raw-loopback {
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skuid unbound meta l4proto { tcp, udp } th sport 53 th dport >= 1024 notrack accept
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skuid { chrony, geoipupdate } meta l4proto { tcp, udp } th sport >= 1024 th dport 53 notrack accept
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skuid powerdns meta l4proto tcp th sport 54 th dport >= 1024 notrack accept
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skuid http meta l4proto tcp th sport >= 1024 th dport 54 notrack accept
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skuid powerdns meta l4proto tcp th sport 81 th dport >= 1024 notrack accept
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skuid != root counter goto graceful-reject
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notrack accept
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}
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chain graceful-reject {
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meta l4proto udp reject
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meta l4proto tcp reject with tcp reset
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reject
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}
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}
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