Ban lists: where Guard and fail2ban ban addresses

A program bans an address (every port, or a protocol's ports) for a
time; the ban list says what it is kept from: the firewall, some hosts
behind it, or everything. Bans drop ahead of every rule, close the
address's connections, group IPv6 by /64, are kept in the database
across restarts and audited. Never banned: the inside, the firewall's
own addresses, the caller, the list's never. bans grant (bans:write:LIST),
hc banlist/bans/ban/unban, Traffic -> Bans, a fail2ban action in contrib/,
and failed logins and refused tokens logged for Guard and fail2ban.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/render/render_test.go

@@ -3,6 +3,7 @@ package render
 import (
 	"context"
 	"fmt"
+	"net/netip"
 	"os"
 	"os/exec"
 	"strings"
@@ -95,10 +96,28 @@ func router() *model.State {
 	st.Redirects = []*model.Redirect{
 		{ID: next(), Position: 1, Match: model.Match{InZones: []string{"lan"}, NotDests: true, Destinations: []string{"10.0.10.5"}, Services: []string{"udp/53"}}, Comment: "force DNS"},
 	}
+	st.BanLists = []*model.BanList{
+		{ID: next(), Name: "router", Scope: model.BanScopeFirewall, Never: []string{"trusted"}},
+		{ID: next(), Name: "web", Scope: model.BanScopeHosts, Hosts: []string{"10.0.10.57", "2a02:8013:7f3d:10::57", "dns_servers"}},
+		{ID: next(), Name: "edge", Scope: model.BanScopeEverything, GroupV6: 48},
+		{ID: next(), Name: "off", Scope: model.BanScopeEverything, Disabled: true},
+	}
 	st.Sort()
 	return st
 }
 
+// banOptions are active bans in each ban list, of every port and of one.
+func banOptions(st *model.State) []Ban {
+	var out []Ban
+	for _, b := range st.BanLists {
+		out = append(out,
+			Ban{List: b.ID, Addr: netip.MustParsePrefix("203.0.113.9/32"), Timeout: 3000},
+			Ban{List: b.ID, Addr: netip.MustParsePrefix("2001:db8:1:2::/64"), Proto: "tcp", Port: 22},
+			Ban{List: b.ID, Addr: netip.MustParsePrefix("198.51.100.7/32"), Proto: "udp", Port: 53, Timeout: 60})
+	}
+	return out
+}
+
 // quotaOptions carries quota usage, as a reload does: the guest quota's,
 // and two devices' of the per-device quota.
 func quotaOptions(st *model.State) (map[string]int64, map[string][]Element) {
@@ -257,7 +276,7 @@ func TestRenderedRulesetPassesNft(t *testing.T) {
 		q, qs := quotaOptions(st)
 		// Enforcing, and in shadow mode after and before other tables.
 		for _, mode := range []Options{{}, {Shadow: true}, {Shadow: true, ShadowBefore: true}} {
-			opt := Options{Elements: map[string][]Element{"guests": {{Addr: "10.0.30.5", Timeout: 1700}, {Addr: "2a02:8013:7f3d:30::5"}}}, Quotas: q, QuotaSets: qs,
+			opt := Options{Elements: map[string][]Element{"guests": {{Addr: "10.0.30.5", Timeout: 1700}, {Addr: "2a02:8013:7f3d:30::5"}}}, Quotas: q, QuotaSets: qs, Bans: banOptions(st),
 				DeviceSets: map[string][]Element{"stats_up_v4": {{Addr: "10.0.10.5", Timeout: 3000, Packets: 7, Bytes: 7000}}, "stats_down_v6": {{Addr: "2001:db8:1:2::", Packets: 1, Bytes: 100}}},
 				Shadow:     mode.Shadow, ShadowBefore: mode.ShadowBefore}
 			nftCheck(t, cmd, fmt.Sprintf("%s (shadow %v, before %v)", name, mode.Shadow, mode.ShadowBefore), Render(st, opt).Text)
@@ -277,3 +296,58 @@ func nftCheck(t *testing.T, cmd []string, name, text string) {
 		}
 	}
 }
+
+func TestRenderBans(t *testing.T) {
+	st := router()
+	id := map[string]int64{}
+	for _, b := range st.BanLists {
+		id[b.Name] = b.ID
+	}
+	text := Render(st, Options{Bans: banOptions(st)}).Text
+	f := func(format string, args ...any) string { return fmt.Sprintf(format, args...) }
+	r, w, e, off := id["router"], id["web"], id["edge"], id["off"]
+	for _, want := range []string{
+		f("set ban_%d_v4 { type ipv4_addr; flags timeout; }", r),
+		f("set ban_%d_v6_svc { type ipv6_addr . inet_proto . inet_service; flags timeout; }", r),
+		// The firewall: in input, every port and one port, /64 for IPv6.
+		f(`ip saddr @ban_%d_v4 counter drop comment "hc:ban%d"`, r, r),
+		f(`ip saddr . meta l4proto . th dport @ban_%d_v4_svc counter drop comment "hc:ban%d"`, r, r),
+		f(`ip6 saddr and ffff:ffff:ffff:ffff:: @ban_%d_v6 counter drop comment "hc:ban%d"`, r, r),
+		f(`ip6 saddr and ffff:ffff:ffff:ffff:: . meta l4proto . th dport @ban_%d_v6_svc counter drop comment "hc:ban%d"`, r, r),
+		// Hosts: in forward, first, to the hosts (literals and sets).
+		f(`ip daddr 10.0.10.57 ip saddr @ban_%d_v4 counter drop`, w),
+		f(`ip daddr @dns_servers_v4 ip saddr . meta l4proto . th dport @ban_%d_v4_svc counter drop`, w),
+		f(`ip6 daddr 2a02:8013:7f3d:10::57 ip6 saddr and ffff:ffff:ffff:ffff:: @ban_%d_v6 counter drop`, w),
+		// Everything: input and forward, /48.
+		f(`ip6 saddr and ffff:ffff:ffff:: @ban_%d_v6 counter drop`, e),
+		// The bans, with their time.
+		f("add element inet housecarl ban_%d_v4 { 203.0.113.9 timeout 3000s }", r),
+		f("add element inet housecarl ban_%d_v6_svc { 2001:db8:1:2:: . tcp . 22 }", w),
+		f("add element inet housecarl ban_%d_v4_svc { 198.51.100.7 . udp . 53 timeout 60s }", e),
+	} {
+		if !strings.Contains(text, want) {
+			t.Errorf("no %q in\n%s", want, text)
+		}
+	}
+	if n := strings.Count(text, f(`@ban_%d_v4 counter drop`, e)); n != 2 {
+		t.Errorf("scope everything: %d rules of every port in IPv4, want 2 (input and forward)", n)
+	}
+	if n := strings.Count(text, f(`@ban_%d_v4 counter drop`, w)); n != 2 {
+		t.Errorf("scope hosts: %d IPv4 rules of every port, want 2 (forward: the literal host and the set)", n)
+	}
+	// Ahead of the accepts: the first rules after loopback, and of forward.
+	in, _, _ := strings.Cut(text[strings.Index(text, "chain input"):], "established")
+	fw, _, _ := strings.Cut(text[strings.Index(text, "chain forward"):], "maxseg")
+	for _, part := range []string{in, fw} {
+		if strings.Contains(part, " accept comment \"hc:r") {
+			t.Errorf("a rule accepts before the bans:\n%s", part)
+		}
+	}
+	if strings.Contains(text, f("ban_%d_", off)) {
+		t.Errorf("a disabled list is rendered")
+	}
+	shadow := Render(st, Options{Shadow: true, Bans: banOptions(st)}).Text
+	if want := f(`ip saddr @ban_%d_v4 counter accept comment "hc:ban%d [would drop]"`, r, r); !strings.Contains(shadow, want) {
+		t.Errorf("shadow: no %q", want)
+	}
+}