Trap paths, and the error burst banning a client refused too often (closes #115)

SWWAF_TRAP_PATHS: a request whose path, as a path rule sees it, is one
of them is a clear sign of attack, banned as a ban rule's match is; the
ban's notes give its trap_path. Checked after the rate limits, before the
rule files.

SWWAF_ERROR_BURST_THRESHOLD (default 30, or off): more refusals in a
minute after a block or ban rule or a trap path, or for a missing or
wrong token, ban the client as a broken limit does. Counted in
clients.json's minute_refusals; limit_hit error_burst, notes kind
refusals.

A token refusal is now the offence token_refused, and
smallwebwaf_offences_total counts every kind the history does.

Judgement call: the threshold is not lowered by a client's limit percentage.

Model: opus-5-5

internal/metrics/metrics.go

@@ -6,7 +6,6 @@ package metrics
 import (
 	"net/http"
 	"strconv"
-	"strings"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -94,8 +93,8 @@ func New(topN int, instanceName string) *Metrics {
 			Help: "How long requests passed to the app took, from then to their end.",
 		}),
 		rateLimitHits: counterVec("smallwebwaf_rate_limit_hits_total",
-			"Requests that broke a rate limit or a byte limit, by its window and "+
-				"its kind, requests or bytes.",
+			"Requests that broke a rate limit, a byte limit or the error burst, by "+
+				"its window and its kind, requests, bytes or refusals.",
 			[]string{"window", "kind"}),
 		sizeAndTimeLimitHits: counterVec("smallwebwaf_size_and_time_limit_hits_total",
 			"Requests that passed a size or time limit, by its setting.",
@@ -407,26 +406,10 @@ func (m *Metrics) RequestEnded(
 		m.upstreamDuration.Observe(upstreamDuration.Seconds())
 	}
 
-	if line.LimitHit != "" {
-		// The log line names a byte limit's window with _bytes after it.
-		window, isBytes := strings.CutSuffix(line.LimitHit, "_bytes")
-
-		kind := ratelimit.KindRequests
-		if isBytes {
-			kind = ratelimit.KindBytes
-		}
-
-		m.rateLimitHits.WithLabelValues(window, kind).Inc()
-	}
-
 	if limit != "" {
 		m.sizeAndTimeLimitHits.WithLabelValues(limit).Inc()
 	}
 
-	if line.Offence != "" {
-		m.offences.WithLabelValues(line.Offence).Inc()
-	}
-
 	if line.Country != "" {
 		m.countries.add(line.Country, line)
 	}
@@ -436,6 +419,28 @@ func (m *Metrics) RequestEnded(
 	}
 }
 
+// LimitHit counts a request that broke a rate limit, a byte limit or the
+// error burst, by the window and the kind of hit.
+func (m *Metrics) LimitHit(hit ratelimit.Hit) {
+	m.rateLimitHits.WithLabelValues(hit.Window, hit.Kind).Inc()
+}
+
+// Offences counts the offences of r, a request that has ended, as its
+// client's history counts them, by kind, named as clients.json names
+// them.
+func (m *Metrics) Offences(r ratelimit.Request) {
+	for kind, committed := range map[string]bool{
+		"limit":         r.BrokeLimit,
+		"attack":        r.Attack,
+		"rule_blocked":  r.RuleBlocked,
+		"token_refused": r.TokenRefused,
+	} {
+		if committed {
+			m.offences.WithLabelValues(kind).Inc()
+		}
+	}
+}
+
 // RuleMatched counts a request that matched the rule id, whose action is
 // action.
 func (m *Metrics) RuleMatched(id, action string) {