Core Rule Set: WordPress's ordinary requests pass by default (closes #235)

Add the ninth change: wordpress.conf switches off, per path and field, each
rule that refused recorded WordPress 7.1.4 traffic. Add the recorded requests,
a test at the defaults and reading bodies, and list WordPress in the README.

Model: opus-5-5

internal/waf/waf_test.go

@@ -1,6 +1,7 @@
 package waf_test
 
 import (
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"net/netip"
@@ -120,7 +121,7 @@ func atDefaults(t *testing.T) *waf.CoreRuleSet {
 }
 
 // wantChange checks that crs lets through passes, a gitea request one of
-// the eight changes is for, and still finds result in refused, a request
+// the nine changes is for, and still finds result in refused, a request
 // like it that the change is not for.
 func wantChange(
 	t *testing.T, crs *waf.CoreRuleSet, passes, refused request, result waf.Result,
@@ -550,6 +551,162 @@ func TestOrdinaryGiteaRequestsPassAndAttacksAreRefused(t *testing.T) {
 	}
 }
 
+// wpLogin is WordPress's sign-in path.
+const wpLogin = "/wp-login.php"
+
+// recordedRequest is a line of a file of recorded requests in testdata.
+type recordedRequest struct {
+	Method  string   `json:"method"`
+	Target  string   `json:"target"`
+	Headers []string `json:"headers"`
+	Body    string   `json:"body"`
+}
+
+// wordpressRequests returns the recorded ordinary WordPress requests in
+// testdata, each with its body.
+func wordpressRequests(t *testing.T) []recordedRequest {
+	t.Helper()
+
+	text, err := os.ReadFile(filepath.Join("testdata", "wordpress-requests.txt"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var requests []recordedRequest
+
+	for line := range strings.Lines(string(text)) {
+		if strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		var r recordedRequest
+
+		err := json.Unmarshal([]byte(line), &r)
+		if err != nil {
+			t.Fatalf("%q: %v", line, err)
+		}
+
+		requests = append(requests, r)
+	}
+
+	return requests
+}
+
+// readingBodiesUpTo64K returns the Core Rule Set as sww runs it by default,
+// but reading bodies up to the largest SWW_WAF_BODY_LIMIT.
+func readingBodiesUpTo64K(t *testing.T) *waf.CoreRuleSet {
+	t.Helper()
+
+	crs, err := waf.New(waf.Params{
+		ParanoiaLevel: 1, DisabledRules: defaultDisabledRules, BodyLimit: 64<<10 - 1,
+	})
+	if err != nil {
+		t.Fatalf("load the Core Rule Set: %v", err)
+	}
+
+	return crs
+}
+
+func TestOrdinaryWordPressRequestsPassAndAttacksAreRefused(t *testing.T) {
+	t.Parallel()
+
+	const threshold = 5 // SWW_WAF_ANOMALY_THRESHOLD's default
+
+	defaults, bodies := atDefaults(t), readingBodiesUpTo64K(t)
+
+	for _, recorded := range wordpressRequests(t) {
+		r := request{recorded.Method, recorded.Target, recorded.Headers}
+
+		crsSets := []*waf.CoreRuleSet{defaults}
+		if recorded.Body != "" {
+			crsSets = append(crsSets, bodies)
+		}
+
+		for _, crs := range crsSets {
+			got, _ := inspectBody(t, crs, r, recorded.Body)
+			if got.Score >= threshold {
+				t.Errorf("%s %s %.200q refused: %+v", r.method, r.target, recorded.Body, got)
+			}
+		}
+	}
+
+	for _, attack := range []string{
+		"1'%20OR%20'1'='1",
+		"..%2F..%2Fwp-config.php",
+		"%3Cscript%3Ealert(1)%3C%2Fscript%3E",
+	} {
+		for _, target := range []string{
+			"/?id=" + attack,
+			wpLogin + "?id=" + attack,
+			"/wp-admin/admin-ajax.php?id=" + attack,
+			"/wp-json/wp/v2/posts?id=" + attack,
+		} {
+			if got := inspect(t, defaults, get(target)); got.Score < threshold {
+				t.Errorf("%s let through: %+v", target, got)
+			}
+		}
+
+		// In a body field no exclusion names, on the paths with exclusions.
+		body := "id=" + attack
+		for _, target := range []string{
+			wpLogin,
+			"/wp-comments-post.php",
+			"/wp-admin/admin-ajax.php",
+			"/wp-admin/post.php",
+			"/wp-admin/options.php",
+		} {
+			got, _ := inspectBody(t, bodies,
+				request{http.MethodPost, target, []string{formData}}, body)
+			if got.Score < threshold {
+				t.Errorf("POST %s %q let through: %+v", target, body, got)
+			}
+		}
+	}
+}
+
+func TestWordPressExclusionsAreNarrow(t *testing.T) {
+	t.Parallel()
+
+	const (
+		query    = "SELECT name FROM users WHERE id = 1;"
+		save     = "/wp-json/wp/v2/posts/1"
+		offREST  = "/api/posts/1"
+		override = "X-HTTP-Method-Override: PUT"
+		length   = "Content-Length: 2"
+	)
+
+	crs := readingBodiesUpTo64K(t)
+	saving := request{http.MethodPost, save, []string{jsonBody, override}}
+
+	content := `{"content":"` + query + `"}`
+	wantBody(t, crs, saving, content, waf.Result{}, content)
+
+	// The other fields of the post keep the rule, and so does the same field
+	// off the REST API.
+	title := `{"title":"` + query + `"}`
+	wantBody(t, crs, saving, title, matched(942100), title)
+	wantBody(t, crs, request{http.MethodPost, offREST, []string{jsonBody}}, content,
+		matched(942100), content)
+
+	// The header X-HTTP-Method-Override is refused off the REST API.
+	defaults := atDefaults(t)
+	wantResult(t, defaults,
+		request{http.MethodPost, save, []string{jsonBody, length, override}},
+		waf.Result{})
+	wantResult(t, defaults,
+		request{http.MethodPost, offREST, []string{jsonBody, length, override}},
+		matched(920450))
+
+	// Signing in: pwd alone skips the list of system files.
+	signIn := request{http.MethodPost, wpLogin, []string{formData}}
+
+	body := "log=a&pwd=b%20%2Fetc%2Fhosts"
+	wantBody(t, crs, signIn, body, waf.Result{}, body)
+
+	body = "log=b%20%2Fetc%2Fhosts&pwd=a"
+	wantBody(t, crs, signIn, body, matched(930120), body)
+}
+
 // bodyLimit is SWW_WAF_BODY_LIMIT in the tests that read bodies.
 const bodyLimit = 8 << 10