127 lines
4 KiB
Text
127 lines
4 KiB
Text
#!/usr/bin/nft -f
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# vim:set ts=4 sw=4 et:
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# IPv4/IPv6 Simple & Safe firewall ruleset.
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# More examples in /usr/share/nftables/ and /usr/share/doc/nftables/examples/.
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# add a variable for each interface:
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define ext_if = eth0
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define vict_if = eth1
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define dmz_if = eth2
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define all_if = { $ext_if, $vict_if, $dmz_if }
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# ct state invalid drop comment "early drop of invalid connections"
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# ct state {established, related} accept comment "allow tracked connections"
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# iifname lo accept comment "allow from loopback"
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# ip protocol icmp accept comment "allow icmp"
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# meta l4proto ipv6-icmp accept comment "allow icmp v6"
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# tcp dport ssh accept comment "allow sshd"
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# pkttype host limit rate 5/second counter reject with icmpx type admin-prohibited
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# counter
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# Block all ipv6, don't allow any ipv6 to either enter or leave the gateway.
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# It is useless because /proc/sys/net/ipv6/conf/disable_ipv6 = 1
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# but we're never too sure so it's better to block here.
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table ip6 block_all_ipv6
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delete table ip6 block_all_ipv6
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table ip6 block_all_ipv6 {
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chain block_input {
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type filter hook input priority filter
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policy drop
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}
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chain block_output {
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type filter hook output priority filter
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policy drop
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}
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chain block_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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}
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# filter ipv4 table.
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table ip global
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delete table ip global
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table ip global {
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set denylist {
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type ipv4_addr
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flags dynamic, timeout
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timeout 2m
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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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# if somebody sent to many new connections to the gateway, it an attack.
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ip protocol tcp ct state new, untracked limit rate over 10/minute add @denylist { ip saddr }
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ip saddr @denylist drop
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ct state established accept
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iifname $vict_if icmp type echo-request limit rate 5/second accept
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iifname $vict_if tcp dport 22 accept
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iifname lo accept
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}
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chain output {
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type filter hook output priority filter
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policy drop
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udp dport 53 accept
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tcp dport 80 limit rate 20/second accept
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tcp dport 443 limit rate 20/second accept
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icmp type echo-request limit rate 5/second accept
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oifname $vict_if ct state established accept
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# accept to say on the victim interface that the gateway is up.
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# oifname $vict_if icmp type echo-reply limit rate 5/second accept
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oifname lo 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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# Block temporarly ip addresses that attemps more than 10 tcp connection per minutes from external network
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iifname $ext_if ip protocol tcp ct state new, untracked limit rate over 10/minute add @denylist { ip saddr }
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ip saddr @denylist drop
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# general authorisations
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icmp type echo-reply accept
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# dmz interface specific
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oifname $dmz_if icmp type echo-request limit rate 5/second accept
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oifname $dmz_if tcp dport 80 accept
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iifname $dmz_if ct state established tcp sport 80 accept
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# external interface specific
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oifname $ext_if icmp type echo-request accept
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oifname $ext_if udp dport 53 accept
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iifname $ext_if ct state established udp sport 53 accept
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oifname $ext_if tcp dport 80 accept
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iifname $ext_if ct state established tcp sport 80 accept
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oifname $ext_if tcp dport 443 accept
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iifname $ext_if ct state established tcp sport 443 accept
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# victim interface specific
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iifname $vict_if tcp dport 22 accept
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oifname $vict_if ct state established tcp sport 22 accept
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# block for two minutes everything else that is from the public interface.
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iifname { $ext_if, $dmz_if } add @denylist { ip saddr }
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}
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}
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#table inet my_nat
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#delete table inet my_nat
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#table inet my_nat {
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# chain postrouting {
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# type nat hook postrouting priority srcnat;
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# oifname "eth0" masquerade;
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# }
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#}
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