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/config/config_test.go

@@ -42,6 +42,7 @@ const (
 	limitBanDuration        = "SWWAF_LIMIT_BAN_DURATION"
 	limitBanRepeatWindow    = "SWWAF_LIMIT_BAN_REPEAT_WINDOW"
 	maxBanDuration          = "SWWAF_MAX_BAN_DURATION"
+	attackBanDuration       = "SWWAF_ATTACK_BAN_DURATION"
 	maxBans                 = "SWWAF_MAX_BANS"
 	banScopeV4Prefix        = "SWWAF_BAN_SCOPE_V4_PREFIX"
 	stateDir                = "SWWAF_STATE_DIR"
@@ -51,6 +52,8 @@ const (
 	metricsTopN             = "SWWAF_METRICS_TOP_N"
 	instanceName            = "SWWAF_INSTANCE_NAME"
 	logRequestHeaders       = "SWWAF_LOG_REQUEST_HEADERS"
+	rulesDir                = "SWWAF_RULES_DIR"
+	rulesEnabled            = "SWWAF_RULES_ENABLED"
 )
 
 // defaultLogRequestHeaders is the default of SWWAF_LOG_REQUEST_HEADERS.
@@ -108,6 +111,7 @@ func TestDefaults(t *testing.T) {
 		LimitBanDuration:            time.Hour,
 		LimitBanRepeatWindow:        24 * time.Hour,
 		MaxBanDuration:              7 * 24 * time.Hour,
+		AttackBanDuration:           7 * 24 * time.Hour,
 		MaxBans:                     5000,
 		BanScopeV4Prefix:            32,
 		StateDir:                    "/var/lib/smallwebwaf",
@@ -115,6 +119,8 @@ func TestDefaults(t *testing.T) {
 		StateCounterInterval:        15 * time.Minute,
 		MetricsToken:                "",
 		MetricsTopN:                 50,
+		RulesDir:                    "/etc/smallwebwaf/rules.d",
+		RulesEnabled:                true,
 	})
 
 	if cfg.UpstreamURL.String() != "http://127.0.0.1:8081" {
@@ -168,13 +174,13 @@ func TestValuesAsSet(t *testing.T) {
 		rateLimitPerMinute:      "60",
 		rateLimitPerHour:        "600",
 		rateLimitPerDay:         "6000",
-		rateLimitExemptPaths:    "/assets/, /favicon.ico",
 		deniedCountries:         "cn, RU,kp,Xk",
 		allowedCountries:        "de",
 		banResponse:             "429",
 		limitBanDuration:        "15m",
 		limitBanRepeatWindow:    "2d",
 		maxBanDuration:          "30d",
+		attackBanDuration:       "1d",
 		maxBans:                 "100",
 		banScopeV4Prefix:        "24",
 		stateDir:                "/srv/waf-state",
@@ -182,6 +188,8 @@ func TestValuesAsSet(t *testing.T) {
 		stateCounterInterval:    "1h",
 		metricsToken:            token,
 		metricsTopN:             "10",
+		rulesDir:                "/srv/waf-rules",
+		rulesEnabled:            "false",
 	})
 
 	wantSettings(t, cfg, config.Config{
@@ -202,6 +210,7 @@ func TestValuesAsSet(t *testing.T) {
 		LimitBanDuration:            15 * time.Minute,
 		LimitBanRepeatWindow:        48 * time.Hour,
 		MaxBanDuration:              30 * 24 * time.Hour,
+		AttackBanDuration:           24 * time.Hour,
 		MaxBans:                     100,
 		BanScopeV4Prefix:            24,
 		StateDir:                    "/srv/waf-state",
@@ -209,6 +218,8 @@ func TestValuesAsSet(t *testing.T) {
 		StateCounterInterval:        time.Hour,
 		MetricsToken:                token,
 		MetricsTopN:                 10,
+		RulesDir:                    "/srv/waf-rules",
+		RulesEnabled:                false,
 	})
 
 	if cfg.UpstreamURL.String() != "https://app.internal:8443/" {
@@ -221,6 +232,12 @@ func TestValuesAsSet(t *testing.T) {
 	wantNetblocks(t, cfg.DenyNets, "198.51.100.0/24")
 	wantCountries(t, deniedCountries, cfg.DeniedCountries, "CN", "RU", "KP", "XK")
 	wantCountries(t, allowedCountries, cfg.ExclusivelyAllowedCountries, "DE")
+}
+
+func TestRateLimitExemptPathsAsSet(t *testing.T) {
+	t.Parallel()
+
+	cfg := fromEnvironment(t, environment{rateLimitExemptPaths: "/assets/, /favicon.ico"})
 
 	if !slices.Equal(cfg.RateLimitExemptPaths, []string{"/assets/", "/favicon.ico"}) {
 		t.Errorf("%s gave %v, want /assets/ and /favicon.ico",
@@ -356,7 +373,7 @@ func TestTrustedProxiesSetButEmptyTrustNothing(t *testing.T) {
 func TestInvalidValueStopsTheStart(t *testing.T) {
 	t.Parallel()
 
-	for _, tc := range []struct{ name, value string }{
+	wantStartStopped(t, []struct{ name, value string }{
 		{listenAddr, "8080"}, {listenAddr, ":http"}, {listenAddr, ":65536"},
 		{upstreamURL, "127.0.0.1:8081"},
 		{upstreamURL, "ftp://127.0.0.1:8081"},
@@ -406,21 +423,37 @@ func TestInvalidValueStopsTheStart(t *testing.T) {
 		{allowedCountries, "uk"},
 		{allowedCountries, "zz"},
 		{allowedCountries, "de,germany"},
-		{banResponse, "404"}, {banResponse, "drop"}, {banResponse, ""},
-		{limitBanDuration, off}, {limitBanDuration, "0s"}, {limitBanDuration, "1"},
-		{limitBanRepeatWindow, off}, {limitBanRepeatWindow, "-1h"},
-		{maxBanDuration, off}, {maxBanDuration, "1w"},
-		{maxBans, off}, {maxBans, "0"}, {maxBans, "5K"},
-		{banScopeV4Prefix, "33"}, {banScopeV4Prefix, "-1"}, {banScopeV4Prefix, "/24"},
-		{stateDir, ""}, {stateDir, "state"}, {stateDir, "./var/lib/smallwebwaf"},
-		{stateWriteDelay, off}, {stateWriteDelay, "0s"},
-		{stateCounterInterval, off}, {stateCounterInterval, "15"},
 		{metricsTopN, off}, {metricsTopN, "0"}, {metricsTopN, "-1"},
 		{logRequestHeaders, "accept,,origin"}, {logRequestHeaders, "accept;origin"},
 		{logRequestHeaders, "accept language"}, {logRequestHeaders, "x-foo:"},
 		{logRequestHeaders, "host"}, {logRequestHeaders, "accept,Host"},
 		{logRequestHeaders, "transfer-encoding"}, {logRequestHeaders, "TRANSFER-ENCODING"},
-	} {
+		{rulesEnabled, "yes"}, {rulesEnabled, "True"},
+	})
+}
+
+func TestInvalidBanOrStateValueStopsTheStart(t *testing.T) {
+	t.Parallel()
+
+	wantStartStopped(t, []struct{ name, value string }{
+		{banResponse, "404"}, {banResponse, "drop"}, {banResponse, ""},
+		{limitBanDuration, off}, {limitBanDuration, "0s"}, {limitBanDuration, "1"},
+		{limitBanRepeatWindow, off}, {limitBanRepeatWindow, "-1h"},
+		{maxBanDuration, off}, {maxBanDuration, "1w"}, {attackBanDuration, off},
+		{maxBans, off}, {maxBans, "0"}, {maxBans, "5K"},
+		{banScopeV4Prefix, "33"}, {banScopeV4Prefix, "-1"}, {banScopeV4Prefix, "/24"},
+		{stateDir, ""}, {stateDir, "state"}, {stateDir, "./var/lib/smallwebwaf"},
+		{stateWriteDelay, off}, {stateWriteDelay, "0s"},
+		{stateCounterInterval, off}, {stateCounterInterval, "15"},
+	})
+}
+
+// wantStartStopped checks that each setting, set to its value, stops the
+// start with an error that names the setting.
+func wantStartStopped(t *testing.T, invalid []struct{ name, value string }) {
+	t.Helper()
+
+	for _, tc := range invalid {
 		t.Run(tc.name+"="+tc.value, func(t *testing.T) {
 			t.Parallel()
 
@@ -536,6 +569,7 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		limitBanDuration:        "1h",
 		limitBanRepeatWindow:    "24h",
 		maxBanDuration:          "7d",
+		attackBanDuration:       "7d",
 		maxBans:                 "5000",
 		banScopeV4Prefix:        "32",
 		stateDir:                "/var/lib/smallwebwaf",
@@ -545,6 +579,8 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		metricsTopN:             "50",
 		instanceName:            hostname,
 		logRequestHeaders:       defaultLogRequestHeaders,
+		rulesDir:                "/etc/smallwebwaf/rules.d",
+		rulesEnabled:            "true",
 	}
 	if !maps.Equal(line.Settings, want) {
 		t.Errorf("logged settings\n%v\nwant\n%v", line.Settings, want)
@@ -574,8 +610,8 @@ func wantSettings(t *testing.T, got *config.Config, want config.Config) {
 	wantBanSettings(t, got, want)
 }
 
-// wantBanSettings checks the settings for bans, the state files and the
-// metrics.
+// wantBanSettings checks the settings for bans, the state files, the
+// metrics and the rule files.
 func wantBanSettings(t *testing.T, got *config.Config, want config.Config) {
 	t.Helper()
 
@@ -583,11 +619,17 @@ func wantBanSettings(t *testing.T, got *config.Config, want config.Config) {
 		got.LimitBanDuration != want.LimitBanDuration ||
 		got.LimitBanRepeatWindow != want.LimitBanRepeatWindow ||
 		got.MaxBanDuration != want.MaxBanDuration ||
+		got.AttackBanDuration != want.AttackBanDuration ||
 		got.MaxBans != want.MaxBans ||
 		got.BanScopeV4Prefix != want.BanScopeV4Prefix {
 		t.Errorf("ban settings\n%+v\nwant\n%+v", got, want)
 	}
 
+	if got.RulesDir != want.RulesDir || got.RulesEnabled != want.RulesEnabled {
+		t.Errorf("rule files in %q, on: %t, want %q, %t",
+			got.RulesDir, got.RulesEnabled, want.RulesDir, want.RulesEnabled)
+	}
+
 	if got.StateDir != want.StateDir ||
 		got.StateWriteDelay != want.StateWriteDelay ||
 		got.StateCounterInterval != want.StateCounterInterval {