AbuseIPDB scores for clients that committed an offence, within a daily budget (closes #105)

With SWWAF_ABUSEIPDB_KEY set, a client whose history counts an offence
(a broken limit, a ban rule's match or a block rule's refusal, counted
by kind) is checked in the background, at most
SWWAF_ABUSEIPDB_DAILY_BUDGET checks a day, the count kept in
reputation.json. A client, an IPv4 address or an IPv6 /64, is checked by
the address it sent from, and its score serves all its addresses. A
score at or over SWWAF_ABUSEIPDB_MIN_SCORE is a hit for
SWWAF_REPUTATION_ACTION, logged as abuseipdb and alerted with its score.
A failure or the used-up budget gives no score and raises
source_failure. The key goes only in the Key header.

Judgement call: the budget's day is UTC; AbuseIPDB documents no reset time.
Judgement call: each check sent spends budget; a minute's pause after a failure.

Model: opus-5-5

internal/proxy/reputation.go

@@ -4,8 +4,14 @@ import (
 	"context"
 
 	"sneak.berlin/go/smallwebwaf/internal/alerts"
+	"sneak.berlin/go/smallwebwaf/internal/ratelimit"
+	"sneak.berlin/go/smallwebwaf/internal/reputation"
 )
 
+// deny is the SWWAF_BLOCKLIST_ACTION and the SWWAF_REPUTATION_ACTION that
+// refuses the requests of a client a source lists.
+const deny = "deny"
+
 // blocklistDenied notes the blocklists that list the client, as
 // noteListed does, and reports whether SWWAF_BLOCKLIST_ACTION, being deny,
 // refuses the request. Being limit, it lowers the client's limits instead
@@ -15,7 +21,7 @@ func (rq *request) blocklistDenied() bool {
 	rq.blocklisted = len(listedBy) > 0
 	rq.noteListed(listedBy, "listed by a blocklist")
 
-	return rq.blocklisted && rq.h.config.BlocklistAction == "deny"
+	return rq.blocklisted && rq.h.config.BlocklistAction == deny
 }
 
 // dnsblDenied notes the DNSBL zones whose verdict lists the client, as
@@ -30,27 +36,63 @@ func (rq *request) dnsblDenied(ctx context.Context) bool {
 	rq.dnsblListed = len(listedBy) > 0
 	rq.noteListed(listedBy, "listed by a DNSBL zone")
 
-	return rq.dnsblListed && rq.h.config.ReputationAction == "deny"
+	return rq.dnsblListed && rq.h.config.ReputationAction == deny
 }
 
-// noteListed adds sources, the URLs of the blocklists or the DNSBL zones,
-// their keys masked, that list the client, to the log line's reputation,
-// counts each of them in the metrics, and raises a reputation_hit alert,
-// with reason, for each.
-func (rq *request) noteListed(sources []string, reason string) {
-	rq.line.Reputation = append(rq.line.Reputation, sources...)
+// abuseIPDBDenied notes AbuseIPDB, as noteHit does, with the score, when
+// its score of the client is a hit, and reports whether
+// SWWAF_REPUTATION_ACTION, being deny, refuses the request, as dnsblDenied
+// does for a zone. While SWWAF_ABUSEIPDB_KEY is unset it does nothing. A
+// client without a score is checked in the background, by the request's
+// address, if its history counts an offence, and the request does not
+// wait for the answer. The score is then used for each address of the
+// client. ctx is the request's own context.
+func (rq *request) abuseIPDBDenied(ctx context.Context) bool {
+	if rq.h.config.AbuseIPDBKey == "" {
+		return false
+	}
 
+	client := clientGroup(rq.client)
+	held, _ := rq.h.limiter.Client(client)
+	offender := held.History.Offences != ratelimit.Offences{}
+
+	score, hit := rq.h.abuseIPDB.Hit(ctx, client, rq.client, offender)
+	if !hit {
+		return false
+	}
+
+	rq.abuseIPDBHit = true
+	rq.noteHit(reputation.AbuseIPDBSource, "scored by AbuseIPDB at or over "+
+		"SWWAF_ABUSEIPDB_MIN_SCORE", map[string]any{
+		"source": reputation.AbuseIPDBSource, "score": score,
+	})
+
+	return rq.h.config.ReputationAction == deny
+}
+
+// noteListed notes each of sources, the URLs of the blocklists or the
+// DNSBL zones, their keys masked, that list the client, as noteHit does,
+// with reason, and the source in the alert's detail.
+func (rq *request) noteListed(sources []string, reason string) {
 	for _, source := range sources {
-		rq.h.metrics.ReputationHit(source)
-		rq.h.alerts.Raise(alerts.Alert{
-			Event:    alerts.EventReputationHit,
-			Client:   rq.client,
-			Netblock: clientGroup(rq.client),
-			ASN:      rq.line.ASN,
-			ASName:   rq.line.ASName,
-			Country:  rq.line.Country,
-			Reason:   reason,
-			Detail:   map[string]any{"source": source},
-		})
+		rq.noteHit(source, reason, map[string]any{"source": source})
 	}
 }
+
+// noteHit adds source, which lists the client, to the log line's
+// reputation, counts it in the metrics, and raises a reputation_hit alert
+// with reason and detail.
+func (rq *request) noteHit(source, reason string, detail map[string]any) {
+	rq.line.Reputation = append(rq.line.Reputation, source)
+	rq.h.metrics.ReputationHit(source)
+	rq.h.alerts.Raise(alerts.Alert{
+		Event:    alerts.EventReputationHit,
+		Client:   rq.client,
+		Netblock: clientGroup(rq.client),
+		ASN:      rq.line.ASN,
+		ASName:   rq.line.ASName,
+		Country:  rq.line.Country,
+		Reason:   reason,
+		Detail:   detail,
+	})
+}