host_firewall: drop inbound traffic from internet-wide scanners (OpenFilters internet-scanners), v4 and v6, daily refresh

host_firewall/templates/host.nft.j2

@@ -38,6 +38,9 @@ include "/etc/nftables.d/host-spamhaus.nft"
 {% if firewall.firehol %}
 include "/etc/nftables.d/host-firehol.nft"
 {% endif %}
+{% if firewall.scanners %}
+include "/etc/nftables.d/host-scanners.nft"
+{% endif %}
 
 table inet host {
 	{{ addr_set('admin_v4', 'ipv4_addr', firewall.admin.v4) }}
@@ -69,6 +72,13 @@ table inet host {
 
 {% endif %}
 		ct state established,related accept
+{% if firewall.scanners %}
+
+		# After the established rule: only inbound connections of scanners drop.
+		ip saddr @scanners_v4 jump scanners_in
+		ip6 saddr @scanners_v6 jump scanners_in
+
+{% endif %}
 		ct state invalid jump drop_log
 		iif lo accept
 
@@ -143,6 +153,16 @@ table inet host {
 		reject
 	}
 {% endif %}
+{% if firewall.scanners %}
+
+	# Own limit and prefix, so scanners use up neither the fw-in-drop budget
+	# nor the one of the blocklists. CrowdSec whitelists the prefix: scans of
+	# these networks are known and need no decision.
+	chain scanners_in {
+		limit rate {{ firewall.log.spamhaus_rate }} log prefix "fw-scanners-in: "
+		drop
+	}
+{% endif %}
 {% if firewall.block_smtp_out or blocklists %}
 
 	# Outbound mail goes through the mail host only. Loopback stays open for a
@@ -220,7 +240,7 @@ table inet host {
 		ip6 saddr @geo_v6 accept
 {% endif %}
 	}
-{% if forward_guard or blocklists %}
+{% if forward_guard or blocklists or firewall.scanners %}
 
 	chain forward {
 		type filter hook forward priority filter; policy accept;
@@ -236,6 +256,11 @@ table inet host {
 		ip saddr @firehol_v4 jump firehol_in
 		ip daddr @firehol_v4 jump firehol_out
 {% endif %}
+{% if firewall.scanners %}
+
+		ct state new ip saddr @scanners_v4 jump scanners_in
+		ct state new ip6 saddr @scanners_v6 jump scanners_in
+{% endif %}
 {% for guard in forward_guard %}
 
 		# {{ guard.key }}

host_firewall/templates/nft-host-scanners.allowlist.j2

@@ -0,0 +1,11 @@
+# {{ ansible_managed }}
+{% set maps = [
+  (crowdsec | default({}, true)).whitelist | default({}, true),
+  firewall.admin.v4 | default({}, true), firewall.admin.v6 | default({}, true),
+  firewall.scrapers.v4 | default({}, true), firewall.scrapers.v6 | default({}, true),
+  firewall.cluster.v4 | default({}, true), firewall.cluster.v6 | default({}, true)] %}
+{% set entries = (maps | map('dict2items') | sum(start=[]) | rejectattr('value', 'none') | map(attribute='value') | map('string') | list
+  + groups['all'] | map('extract', hostvars, 'public_ips') | select('defined') | flatten) | unique %}
+{% for entry in entries %}
+{{ entry }}
+{% endfor %}