Rule files, and bans for a clear sign of attack (closes #24)

Every *.rules file in SWWAF_RULES_DIR not named with a leading dot is
read at start, and again 2 seconds after the directory's last change.
Each request is checked against the rules after the rate limits: log
notes a match, block refuses with 403, ban refuses and bans the netblock
for SWWAF_ATTACK_BAN_DURATION, made permanent by its next request or
attack. path, query and uri are matched as the request line sent them;
header:Host and header:Transfer-Encoding are refused. Bans gain a cause.
The image ships 00-default.rules.

Judgement call: a header sent twice is matched with its values joined
by ", ".
Judgement call: SWWAF_MAX_BAN_DURATION does not cap a ban for an attack.
Not in this unit: offences for rule matches, with the error burst.

Model: opus-5-5

internal/bans/bans_test.go

@@ -24,8 +24,9 @@ func TestRepeatsTripleUntilPermanent(t *testing.T) {
 		ban := ledger.BanForLimit(netblock, now, bans.Notes{})
 
 		length := time.Duration(hours) * time.Hour
-		if !ban.Expires.Equal(now.Add(length)) || ban.Notes.EarlierBans != i {
-			t.Fatalf("ban %d lasts %s with %d earlier bans, want %d hours and %d",
+		if !ban.Expires.Equal(now.Add(length)) ||
+			ban.Notes.EarlierBans != (bans.EarlierBans{Limit: i}) {
+			t.Fatalf("ban %d lasts %s with earlier bans %+v, want %d hours and %d for a limit",
 				i+1, ban.Expires.Sub(now), ban.Notes.EarlierBans, hours, i)
 		}
 
@@ -66,8 +67,9 @@ func TestRepeatWindowRunsOut(t *testing.T) {
 			first := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
 			second := ledger.BanForLimit(netblock, first.Expires.Add(tc.gap), bans.Notes{})
 
-			if second.Expires.Sub(second.Start) != tc.want || second.Notes.EarlierBans != 1 {
-				t.Errorf("second ban lasts %s with %d earlier bans, want %s and 1",
+			if second.Expires.Sub(second.Start) != tc.want ||
+				second.Notes.EarlierBans != (bans.EarlierBans{Limit: 1}) {
+				t.Errorf("second ban lasts %s with earlier bans %+v, want %s and 1 for a limit",
 					second.Expires.Sub(second.Start), second.Notes.EarlierBans, tc.want)
 			}
 		})
@@ -235,9 +237,102 @@ func TestFullLedgerDropsTheEarlierBanOfTheNetblockBannedAgain(t *testing.T) {
 	second := ledger.BanForLimit(netblock, first.Expires, bans.Notes{})
 
 	held := ledger.Bans(netblock)
-	if len(held) != 1 || held[0] != second || held[0].Notes.EarlierBans != 1 {
-		t.Errorf("the ledger holds %+v, want only the second ban, with 1 earlier ban",
-			held)
+	if len(held) != 1 || held[0] != second ||
+		held[0].Notes.EarlierBans != (bans.EarlierBans{Limit: 1}) {
+		t.Errorf("the ledger holds %+v, want only the second ban, "+
+			"with 1 earlier ban for a limit", held)
+	}
+}
+
+func TestRequestDuringAnAttackBanMakesItPermanent(t *testing.T) {
+	t.Parallel()
+
+	ledger := bans.New(defaultRules())
+	netblock := netip.MustParsePrefix("203.0.113.9/32")
+	notes := bans.Notes{RuleID: "env-file", Target: "path"}
+
+	ban := ledger.BanForAttack(netblock, midnight(), notes)
+	if !ban.Expires.Equal(midnight().Add(7*day)) || ban.Cause != bans.CauseAttack ||
+		ban.Notes.RuleID != "env-file" || ledger.Made(bans.CauseAttack) != 1 ||
+		ledger.Made(bans.CauseLimit) != 0 {
+		t.Fatalf("the ban is %+v, with %d made for an attack and %d for a limit, "+
+			"want one for an attack, of seven days", ban,
+			ledger.Made(bans.CauseAttack), ledger.Made(bans.CauseLimit))
+	}
+
+	wantChanged(t, ledger, true)
+
+	// In observe mode the ban refuses nothing, and stays as it is.
+	got, _ := ledger.Find(netblock.Addr(), midnight().Add(time.Hour))
+	if got.Permanent() {
+		t.Fatal("a request found under the ban made it permanent")
+	}
+
+	// A request it refuses makes it permanent, and bans.json due.
+	got, _ = ledger.Check(netblock.Addr(), midnight().Add(time.Hour))
+	if !got.Permanent() || !ledger.Bans(netblock)[0].Permanent() {
+		t.Fatalf("after a request during the ban, it is %+v, want it permanent", got)
+	}
+
+	wantChanged(t, ledger, true)
+
+	_, banned := ledger.Check(netblock.Addr(), midnight().Add(100*365*day))
+	if !banned {
+		t.Error("the permanent ban ended")
+	}
+}
+
+func TestAttackAfterAnAttackBanHasEndedBansPermanently(t *testing.T) {
+	t.Parallel()
+
+	ledger := bans.New(defaultRules())
+	netblock := netip.MustParsePrefix("203.0.113.9/32")
+
+	// A ban for a broken limit before does not count.
+	first := ledger.BanForLimit(netblock, midnight(), bans.Notes{})
+	second := ledger.BanForAttack(netblock, first.Expires, bans.Notes{})
+
+	if second.Expires.Sub(second.Start) != 7*day {
+		t.Fatalf("the first ban for an attack lasts %s, want 7 days",
+			second.Expires.Sub(second.Start))
+	}
+
+	// Once that has run out without a request, the netblock is served, and
+	// its next clear sign of attack bans it for good.
+	_, banned := ledger.Check(netblock.Addr(), second.Expires)
+	if banned {
+		t.Fatal("the ban did not end")
+	}
+
+	// Its notes show the earlier ban for an attack that makes it permanent,
+	// beside the one for a limit.
+	third := ledger.BanForAttack(netblock, second.Expires.Add(30*day), bans.Notes{})
+	if !third.Permanent() ||
+		third.Notes.EarlierBans != (bans.EarlierBans{Limit: 1, Attack: 1}) {
+		t.Errorf("the next ban for an attack is %+v, want a permanent one, "+
+			"with 1 earlier ban for a limit and 1 for an attack", third)
+	}
+}
+
+func TestAttackBanDoesNotLengthenTheNextBanForALimit(t *testing.T) {
+	t.Parallel()
+
+	ledger := bans.New(defaultRules())
+	netblock := netip.MustParsePrefix("203.0.113.9/32")
+
+	// Three times the seven days would be permanent; a limit broken as the
+	// ban for an attack ends bans for an hour, as a first broken limit does.
+	attack := ledger.BanForAttack(netblock, midnight(), bans.Notes{})
+	limit := ledger.BanForLimit(netblock, attack.Expires, bans.Notes{})
+
+	if limit.Expires.Sub(limit.Start) != time.Hour || limit.Cause != bans.CauseLimit {
+		t.Errorf("the ban for a limit is %+v, want one of an hour", limit)
+	}
+
+	// And a request during the ban for a limit leaves it as it is.
+	got, _ := ledger.Check(netblock.Addr(), limit.Start)
+	if got.Permanent() {
+		t.Error("a request during a ban for a limit made it permanent")
 	}
 }
 
@@ -269,6 +364,7 @@ func defaultRules() bans.Rules {
 		LimitBanDuration:     time.Hour,
 		LimitBanRepeatWindow: day,
 		MaxBanDuration:       7 * day,
+		AttackBanDuration:    7 * day,
 		MaxBans:              5000,
 	}
 }