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#!/usr/sbin/nft -f
define in-tcp-ports = {
{{ ansible_port|default(22) }}
{% if 'MX' in group_names %}
, 25 # SMTP
{% endif %}
{% if 'LDAP_provider' in group_names %}
, 636 # ldaps
{% endif %}
{% if 'IMAP' in group_names %}
, 993 # imaps
, 4190 # ManageSieve
{% endif %}
{% if 'MSA' in group_names %}
, 587 # submission [RFC4409]
, 465 # submission over TLS [RFC8314]
{% endif %}
{% if 'webmail' in group_names or 'lists' in group_names or 'wiki' in group_names or 'nextcloud' in group_names %}
, 80 # HTTP
, 443 # HTTP over SSL/TLS
{% endif %}
}
define out-tcp-ports = {
22
, 80 # HTTP
, 443 # HTTP over SSL/TLS
{% if 'out' in group_names or 'MSA' in group_names %}
, 25 # SMTP
{% endif %}
{% if 'LDAP_provider' in group_names %}
, 11371 # OpenPGP HTTP Keyserver
, 43 # whois
{% elif 'MX' in group_names or 'lists' in group_names or 'nextcloud' in group_names %}
, 636 # ldaps
{% endif %}
{% if 'IMAP' in group_names %}
, 2703 # Razor2
{% endif %}
}
###############################################################################
flush ruleset
table netdev filter {
{% for if in ansible_interfaces %}
{% if if != "lo" and ansible_facts[if].active %}
{% set addr = (ansible_facts[if].ipv4 | default({'address': '0.0.0.0'})).address %}
chain INGRESS-{{ if }} {
type filter hook ingress device {{ if }} priority -499
policy accept
# IPsec traffic (refined later in the filter rule)
ip saddr {{ ipsec_subnet }} ip daddr {{ ipsec[inventory_hostname_short] }} meta secpath exists accept
# rate-limiting is done directly by the kernel (net.ipv4.icmp_{ratelimit,ratemask} runtime options)
icmp type { echo-reply, echo-request, destination-unreachable, time-exceeded } counter accept
icmpv6 type { echo-reply, echo-request, destination-unreachable,
packet-too-big, time-exceeded, parameter-problem } counter accept
# accept neighbour discovery for autoconfiguration, RFC 4890 sec. 4.4.1
ip6 hoplimit 255 icmpv6 type { 133,134,135,136,141,142 } counter accept
# accept link-local multicast receiver notification messages
ip6 saddr fe80::/10 ip6 daddr ff02::/16 ip6 hoplimit 1 icmpv6 type { 130,131,132,143 } counter accept
# drop all remaining ICMP/ICMPv6 traffic
meta l4proto { icmp, icmpv6 } counter drop
# bogon filter (cf. RFC 6890 for non-global ip addresses)
define bogon = {
0.0.0.0/8 # this host, on this network (RFC 1122 sec. 3.2.1.3)
{% if not addr | ansible.utils.ipaddr('10.0.0.0/8') %}
, 10.0.0.0/8 # private-use (RFC 1918)
{% endif %}
, 100.64.0.0/10 # shared address space (RFC 6598)
, 127.0.0.0/8 # loopback (RFC 1122, sec. 3.2.1.3)
, 169.254.0.0/16 # link local (RFC 3927)
, 172.16.0.0/12 # private-use (RFC 1918)
, 192.0.0.0/24 # IETF protocol assignments (RFC 6890 sec. 2.1)
, 192.0.2.0/24 # documentation (RFC 5737)
{% if not addr | ansible.utils.ipaddr('192.168.0.0/16') %}
, 192.168.0.0/16 # private-use (RFC 1918)
{% endif %}
, 198.18.0.0/15 # benchmarking (RFC 2544)
, 198.51.100.0/24 # documentation (RFC 5737)
, 203.0.113.0/24 # documentation (RFC 5737)
, 224.0.0.0/3 # multicast - class D 224.0.0.0/4 + class E 240.0.0.0/4 (RFC 1112 sec. 4)
, 255.255.255.255/32 # limited broadcast (RFC 0919 sec. 7)
}
ip saddr $bogon counter drop
ip daddr $bogon counter drop
# See also https://www.team-cymru.org/Services/Bogons/fullbogons-ipv6.txt
define bogon6 = {
::1/128 # loopback address (RFC 4291)
, ::/128 # unspecified (RFC 4291)
, ::ffff:0:0/96 # IPv4-mapped address (RFC 4291)
, 100::/64 # discard-only address block (RFC 6666)
, 2001::/23 # IETF protocol assignments (RFC 2928)
, 2001::/32 # TEREDO (RFC 4380)
, 2001:2::/48 # benchmarking (RFC 5180)
, 2001:db8::/32 # documentation (RFC 3849)
, 2001:10::/28 # ORCHID (RFC 4843)
, 2002::/16 # 6to4 (RFC 3056)
, fc00::/7 # unique-local (RFC 4193)
, fe80::/10 # linked-scoped unicast (RFC 4291)
}
ip6 saddr $bogon6 counter drop
ip6 saddr $bogon6 counter drop
}
{% endif %}
{% endfor %}
}
table inet raw {
chain PREROUTING-stateless {
# XXX can't add that to the ingress hook as that happens before IP defragmentation
# so we don't have the TCP header in later fragments (we don't want to drop IP
# fragments, see https://blog.cloudflare.com/ip-fragmentation-is-broken/ )
type filter hook prerouting priority -399 # > NF_IP_PRI_CONNTRACK_DEFRAG (-400)
policy accept
# stateless filter for bogus TCP packets
tcp flags & (fin|syn|rst|psh|ack|urg) == 0x0 counter drop # null packet
tcp flags & (fin|psh|urg) == fin|psh|urg counter drop # XMAS packet
tcp flags & (syn|rst) == syn|rst counter drop
tcp flags & (fin|rst) == fin|rst counter drop
tcp flags & (fin|syn) == fin|syn counter drop
tcp flags & (fin|psh|ack) == fin|psh counter drop
}
chain PREROUTING {
type filter hook prerouting priority -199 # > NF_IP_PRI_CONNTRACK (-200)
policy accept
# stateful filter
ct state invalid counter drop
}
}
table inet filter {
# blackholes
set fail2ban { type ipv4_addr; timeout 10m; }
set fail2ban6 { type ipv6_addr; timeout 10m; }
chain input {
type filter hook input priority 0
policy drop
iif lo accept
# XXX Bullseye: this is a rather crude match as nftables 0.9.0 lacks support for ipsec expressions
# to match match inbound resp. outbound policies and source resp. destination tunnel addresses.
# https://serverfault.com/questions/971735/how-to-match-reqid-in-nftables
# https://blog.fraggod.net/2016/09/25/nftables-re-injected-ipsec-matching-without-xt_policy.html
# (We can't use marks to match post-ESP decapsulation here because that doesn't work well with UDP
# encapsulation.) We'll also pin the reqid to the lowest address byte in ipsec.conf(5); that way
# peers can't impersonate each other.
meta l4proto esp accept
# ip saddr {{ ipsec_subnet }} ip daddr {{ ipsec[inventory_hostname_short] }} ipsec in reqid $i accept
ip saddr {{ ipsec_subnet }} ip daddr {{ ipsec[inventory_hostname_short] }} meta secpath exists accept
# incoming ICMP/ICMPv6 traffic was filtered in the ingress chain already
meta l4proto { icmp, icmpv6 } counter accept
# NTP (ntpd uses sport 123 but systemd-timesyncd does not)
udp sport 123 ct state related,established accept
{% if groups.all | length > 1 %}
udp sport 500 udp dport 500 ct state new,related,established accept
{% if groups.NATed | length > 0 %}
udp sport 4500 udp dport 4500 ct state new,related,established accept
{% endif %}
{% endif %}
udp sport 53 ct state related,established accept
tcp sport 53 ct state related,established accept
{% if 'dhclient' in group_names %}
ip version 4 udp sport 67 udp dport 68 ct state related,established accept
ip6 version 6 udp sport 547 udp dport 546 ct state related,established accept
{% endif %}
meta l4proto tcp ip saddr @fail2ban counter drop
meta l4proto tcp ip6 saddr @fail2ban6 counter drop
tcp dport $in-tcp-ports ct state related,established accept
tcp dport $in-tcp-ports ct state new counter accept
tcp sport $out-tcp-ports ct state related,established accept
}
chain output {
type filter hook output priority 0
policy drop
oif lo accept
# XXX Bullseye: unlike for input we can't use marks or test for
# secpath existence here, because by the time we see a packet to
# 172.16.0.0/24 we don't know if it'll be encapsulated
meta l4proto esp accept
# ip saddr {{ ipsec[inventory_hostname_short] }} ip daddr {{ ipsec_subnet }} ipsec out reqid $i accept
ip saddr {{ ipsec[inventory_hostname_short] }} ip daddr {{ ipsec_subnet }} accept
meta l4proto { icmp, icmpv6 } counter accept
# NTP (ntpd uses sport 123 but systemd-timesyncd does not)
udp dport 123 ct state new,related,established accept
{% if groups.all | length > 1 %}
udp sport 500 udp dport 500 ct state new,related,established accept
{% if groups.NATed | length > 0 %}
udp sport 4500 udp dport 4500 ct state new,related,established accept
{% endif %}
{% endif %}
udp dport 53 ct state new,related,established accept
tcp dport 53 ct state new,related,established accept
{% if 'dhclient' in group_names %}
ip version 4 udp sport 68 udp dport 67 ct state new,related,established accept
ip6 version 6 udp sport 546 udp dport 547 ct state new,related,established accept
{% endif %}
tcp sport $in-tcp-ports ct state related,established accept
tcp dport $out-tcp-ports ct state related,established accept
tcp dport $out-tcp-ports ct state new counter accept
meta l4proto tcp counter reject with tcp reset
meta l4proto udp counter reject
counter reject
}
}
|
