The Core Rule Set, run by Coraza, on each request's method, URL and headers (closes #25)

Coraza v3.8.1 runs the Core Rule Set 4.25.0 (coraza-coreruleset v4.25.0)
after the rule files, with the six changes and the default
SWWAF_WAF_DISABLED_RULES that SPEC.md gives; no body, no response.
SWWAF_WAF_MODE, SWWAF_WAF_PARANOIA_LEVEL, SWWAF_WAF_ANOMALY_THRESHOLD and
SWWAF_WAF_EXEMPT_PATHS as specified; SWWAF_WAF_DISABLED_RULES refuses
900000 to 900999, smallwebwaf's own rules among them. A request with more
query parameters than Coraza reads, 1000, adds 5 (rule 900300). In block
mode a match is refused with 403, an offence counted toward the error
burst; in detect mode it is let through. Both log waf_rule_ids, waf_score
and duration_waf, raise waf_block, and count
smallwebwaf_waf_matches_total.

Judgement call: waf_block is raised in block mode too.
Deviation: no engine-error path; with no body read, Coraza cannot fail.

Model: opus-5-5

internal/config/config_test.go

@@ -91,6 +91,11 @@ const (
 	logLevel                = "SWWAF_LOG_LEVEL"
 	rulesDir                = "SWWAF_RULES_DIR"
 	rulesEnabled            = "SWWAF_RULES_ENABLED"
+	wafMode                 = "SWWAF_WAF_MODE"
+	wafParanoiaLevel        = "SWWAF_WAF_PARANOIA_LEVEL"
+	wafAnomalyThreshold     = "SWWAF_WAF_ANOMALY_THRESHOLD"
+	wafDisabledRules        = "SWWAF_WAF_DISABLED_RULES"
+	wafExemptPaths          = "SWWAF_WAF_EXEMPT_PATHS"
 	trapPaths               = "SWWAF_TRAP_PATHS"
 	errorBurstThreshold     = "SWWAF_ERROR_BURST_THRESHOLD"
 	logRemoteURL            = "SWWAF_LOG_REMOTE_URL"
@@ -170,6 +175,9 @@ const (
 // defaultReputationCacheTTL is the default of SWWAF_REPUTATION_CACHE_TTL.
 const defaultReputationCacheTTL = "24h"
 
+// defaultWAFDisabledRules is the default of SWWAF_WAF_DISABLED_RULES.
+const defaultWAFDisabledRules = "920340,920420,920440,920640,930130,930140"
+
 // defaultLogRequestHeaders is the default of SWWAF_LOG_REQUEST_HEADERS.
 const defaultLogRequestHeaders = "accept,accept-language,accept-encoding," +
 	"content-type,origin,range"
@@ -553,6 +561,105 @@ func TestInvalidTrapPathOrErrorBurstThresholdStopsTheStart(t *testing.T) {
 	}
 }
 
+func TestCoreRuleSetSettings(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range []struct {
+		env  environment
+		want config.Config
+	}{
+		{
+			environment{},
+			config.Config{
+				WAFMode: config.WAFModeBlock, WAFParanoiaLevel: 1, WAFAnomalyThreshold: 5,
+				WAFDisabledRules: []int{920340, 920420, 920440, 920640, 930130, 930140},
+				WAFExemptPaths:   []string{},
+			},
+		},
+		{
+			environment{
+				wafMode: config.WAFModeDetect, wafParanoiaLevel: "4", wafAnomalyThreshold: "10",
+				wafDisabledRules: "942100, 920350", wafExemptPaths: "/api/, /static/",
+			},
+			config.Config{
+				WAFMode: config.WAFModeDetect, WAFParanoiaLevel: 4, WAFAnomalyThreshold: 10,
+				WAFDisabledRules: []int{942100, 920350},
+				WAFExemptPaths:   []string{"/api/", "/static/"},
+			},
+		},
+		{
+			environment{wafMode: off, wafAnomalyThreshold: off, wafDisabledRules: ""},
+			config.Config{
+				WAFMode: config.WAFModeOff, WAFParanoiaLevel: 1, WAFAnomalyThreshold: 0,
+				WAFDisabledRules: []int{}, WAFExemptPaths: []string{},
+			},
+		},
+	} {
+		cfg := fromEnvironment(t, tc.env)
+
+		got := config.Config{
+			WAFMode: cfg.WAFMode, WAFParanoiaLevel: cfg.WAFParanoiaLevel,
+			WAFAnomalyThreshold: cfg.WAFAnomalyThreshold,
+			WAFDisabledRules:    cfg.WAFDisabledRules, WAFExemptPaths: cfg.WAFExemptPaths,
+		}
+		if !reflect.DeepEqual(got, tc.want) {
+			t.Errorf("%v gave\n%+v\nwant\n%+v", tc.env, got, tc.want)
+		}
+	}
+}
+
+func TestInvalidCoreRuleSetSettingStopsTheStart(t *testing.T) {
+	t.Parallel()
+
+	const (
+		notParanoiaLevel = " is not a paranoia level, from 1 to 4"
+		setupRule        = " is from 900000 to 900999, the ids of the rules that set " +
+			"the Core Rule Set up and of smallwebwaf's own, which cannot be switched off"
+	)
+
+	for _, tc := range []struct{ name, value, want string }{
+		{wafMode, "enforce", `"enforce" is not off, detect or block`},
+		{wafParanoiaLevel, "0", `"0"` + notParanoiaLevel},
+		{wafParanoiaLevel, "5", `"5"` + notParanoiaLevel},
+		{wafParanoiaLevel, off, `"off"` + notParanoiaLevel},
+		{
+			wafAnomalyThreshold, "0",
+			`"0" is not a whole number above zero, such as 60, or off`,
+		},
+		{
+			wafDisabledRules, "920340,REQUEST-920",
+			`"REQUEST-920" is not the id of a Core Rule Set rule, ` +
+				`a whole number such as 942100`,
+		},
+		{
+			wafDisabledRules, "-942100",
+			`"-942100" is not the id of a Core Rule Set rule, ` +
+				`a whole number such as 942100`,
+		},
+		// The paranoia level, the allowed methods, the headers refused, and
+		// a request with more query parameters than Coraza keeps.
+		{wafDisabledRules, "942100,900000", `"900000"` + setupRule},
+		{wafDisabledRules, "942100,900200", `"900200"` + setupRule},
+		{wafDisabledRules, "942100,900250", `"900250"` + setupRule},
+		{wafDisabledRules, "942100,900300", `"900300"` + setupRule},
+		{
+			wafExemptPaths, "api/",
+			`"api/" is not a path prefix starting with /, such as /assets/`,
+		},
+	} {
+		t.Run(tc.name+"="+tc.value, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := config.FromEnvironment(environment{tc.name: tc.value}.lookupEnv)
+
+			want := tc.name + ": " + tc.want
+			if err == nil || err.Error() != want {
+				t.Errorf("error %v, want %s", err, want)
+			}
+		})
+	}
+}
+
 func TestInstanceNameAndLoggedHeadersAsSet(t *testing.T) {
 	t.Parallel()
 
@@ -2291,6 +2398,11 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		logLevel:                "info",
 		rulesDir:                "/etc/smallwebwaf/rules.d",
 		rulesEnabled:            "true",
+		wafMode:                 config.WAFModeBlock,
+		wafParanoiaLevel:        "1",
+		wafAnomalyThreshold:     "5",
+		wafDisabledRules:        defaultWAFDisabledRules,
+		wafExemptPaths:          "",
 		trapPaths:               "",
 		errorBurstThreshold:     "30",
 		logRemoteURL:            "",