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

Every *.rules file in SWWAF_RULES_DIR is read at start and on each
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/proxy/proxy_test.go

@@ -17,6 +17,7 @@ import (
 	"sneak.berlin/go/smallwebwaf/internal/config"
 	"sneak.berlin/go/smallwebwaf/internal/proxy"
 	"sneak.berlin/go/smallwebwaf/internal/requestlog"
+	"sneak.berlin/go/smallwebwaf/internal/rules"
 )
 
 const (
@@ -74,6 +75,8 @@ const (
 	banScopeV4Prefix        = "SWWAF_BAN_SCOPE_V4_PREFIX"
 	instanceName            = "SWWAF_INSTANCE_NAME"
 	logRequestHeaders       = "SWWAF_LOG_REQUEST_HEADERS"
+	attackBanDuration       = "SWWAF_ATTACK_BAN_DURATION"
+	rulesDir                = "SWWAF_RULES_DIR"
 )
 
 // output collects what smallwebwaf writes on stdout.
@@ -212,14 +215,15 @@ func startProxyWithGeoJS(
 }
 
 // startProxyWithClock is startProxyWithGeoJS with requests counted and
-// bans made by the time now tells, and returns the server as well.
+// bans made by the time now tells, and returns the server as well. Unless
+// env sets SWWAF_RULES_DIR, it is an empty directory, of no rules.
 func startProxyWithClock(
 	t *testing.T, appURL, geojsURL string, now func() time.Time,
 	env map[string]string,
 ) (string, *output, *proxy.Server) {
 	t.Helper()
 
-	settings := map[string]string{"SWWAF_UPSTREAM_URL": appURL}
+	settings := map[string]string{"SWWAF_UPSTREAM_URL": appURL, rulesDir: t.TempDir()}
 	maps.Copy(settings, env)
 
 	cfg, err := config.FromEnvironment(func(name string) (string, bool) {
@@ -232,12 +236,22 @@ func startProxyWithClock(
 	}
 
 	out := &output{}
+	processLog := requestlog.NewProcessLogger(out)
+
+	ruleFiles, err := rules.Load(rules.Params{
+		Dir: cfg.RulesDir, Enabled: cfg.RulesEnabled, ProcessLog: processLog,
+	})
+	if err != nil {
+		t.Fatalf("rule files: %v", err)
+	}
+
 	server := proxy.New(proxy.Params{
 		Config:     cfg,
 		RequestLog: out,
-		ProcessLog: requestlog.NewProcessLogger(out),
+		ProcessLog: processLog,
 		GeoJSURL:   geojsURL,
 		Now:        now,
+		Rules:      ruleFiles,
 	})
 
 	listener, err := (&net.ListenConfig{}).Listen(t.Context(), "tcp", localhost+":0")