nftables-workstation.nft

   1 #!/usr/sbin/nft -f
   2 #
   3 # nftables ruleset for an End Node acting as a workstation in a LAN.
   4 #
   5 # Copyright (C) 2018  Antonio Ospite <ao2@ao2.it>
   6 # SPDX-License-Identifier: MIT
   7 #
   8 # Based on:
   9 # https://wiki.nftables.org/wiki-nftables/index.php/Quick_reference-nftables_in_10_minutes#Simple_IP.2FIPv6_Firewall
  10 # https://wiki.archlinux.org/index.php/Nftables#Workstation
  11 # https://stosb.com/blog/explaining-my-configs-nftables/
  12
  13 flush ruleset
  14
  15 table inet filter {
  16
  17     define common_open_ports = {
  18             xmpp-client,
  19             xmpp-server,
  20             5298, # Link-local XMPP, for backward compatibility, XEP-0174
  21     }
  22
  23     set tcp_open_ports {
  24         type inet_service
  25         flags interval
  26
  27         elements = {
  28             $common_open_ports,
  29         }
  30     }
  31
  32     set udp_open_ports {
  33         type inet_service
  34         flags interval
  35
  36         elements = {
  37             $common_open_ports,
  38         }
  39     }
  40
  41     chain input {
  42         type filter hook input priority 0
  43         policy drop
  44
  45         ct state established,related accept
  46         ct state invalid drop
  47         ct state new jump in-new
  48
  49         iif lo accept
  50
  51         ip protocol icmp icmp type {
  52             echo-reply,
  53             echo-request,
  54             time-exceeded,
  55             parameter-problem,
  56             destination-unreachable
  57         } accept
  58
  59         # ICMPv6 configuration based on:
  60         # https://github.com/intel/intel-iot-refkit/blob/master/meta-refkit-core/recipes-security/nftables-settings-default/files/firewall.template
  61         ip6 nexthdr ipv6-icmp icmpv6 type {
  62             echo-reply,
  63             echo-request,
  64             time-exceeded,
  65             parameter-problem,
  66             destination-unreachable,
  67             packet-too-big
  68         } accept
  69
  70         # Allow auto configuration support.
  71         ip6 nexthdr ipv6-icmp icmpv6 type {
  72             nd-router-advert,
  73             nd-router-solicit,
  74             nd-neighbor-advert,
  75             nd-neighbor-solicit
  76         } ip6 hoplimit 255 accept
  77
  78         # Allow multicast listener discovery on link-local addresses.
  79         # RFC2710 specifies that a Hop-by-Hop Options header is used.
  80         hbh nexthdr ipv6-icmp icmpv6 type {
  81             mld-listener-query,
  82             mld-listener-report,
  83             mld-listener-reduction
  84         } ip6 saddr fe80::/10 accept
  85
  86         # Allow multicast router discovery messages on link-local addresses (hop limit 1).
  87         ip6 nexthdr ipv6-icmp icmpv6 type {
  88             nd-router-advert,
  89             nd-router-solicit
  90         } ip6 hoplimit 1 ip6 saddr fe80::/10 accept
  91
  92         # Allow IGMPv3 queries.
  93         ip protocol igmp ip daddr 224.0.0.1 accept
  94
  95         # Silently drop other incoming broadcast and multicast traffic.
  96         meta pkttype {broadcast, multicast} drop
  97
  98         limit rate 3/minute burst 10 packets log prefix "[INPUT]: "
  99         counter reject
 100     }
 101
 102     chain in-new {
 103         # Silently drop DHCPv4 Discover and Request packets from other clients.
 104         ip saddr 0.0.0.0 ip daddr 255.255.255.255 udp sport bootpc udp dport bootps drop
 105
 106         # Silently drop DHCPv6 from other clients.
 107         ip6 saddr fe80::/64 ip6 daddr fe80::/64 udp sport dhcpv6-client udp dport dhcpv6-server drop
 108
 109         # mDNS (ZeroConf/Bonjour)
 110         ip  daddr 224.0.0.251 udp dport mdns accept
 111         ip6 daddr ff02::fb    udp dport mdns accept
 112
 113         # SSDP: https://en.wikipedia.org/wiki/Simple_Service_Discovery_Protocol
 114         ip daddr 239.255.255.250 udp dport 1900 accept
 115         ip6 daddr {
 116             ff02::c,
 117             ff05::c,
 118             ff08::c,
 119             ff0e::c
 120         } udp dport 1900 accept
 121
 122         tcp dport @tcp_open_ports tcp flags & (fin | syn | rst | ack) == syn accept
 123         udp dport @udp_open_ports accept
 124     }
 125
 126     chain forward {
 127         type filter hook forward priority 0
 128         policy drop
 129
 130         limit rate 3/minute burst 10 packets log prefix "[FORWARD]: "
 131         counter reject
 132     }
 133
 134     chain output {
 135         type filter hook output priority 0
 136         policy drop
 137
 138         counter accept
 139     }
 140 }