fix: security audit remediation (AUDIT-001, 003, 004, 005, 006, 018)

- AUDIT-001: Validate OpenSSL revoke inputs (hex-only serials, RFC 5280 reasons)
- AUDIT-003: Enforce /20 CIDR size cap at API level (create + update)
- AUDIT-004: Support comma-separated CERTCTL_AUTH_SECRET for zero-downtime key rotation
- AUDIT-005: Add ReadHeaderTimeout (5s) to prevent Slowloris
- AUDIT-006: Document audit trail query parameter exclusion rationale
- AUDIT-018: Add immediate-run-on-start to short-lived expiry scheduler loop

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/api/middleware/auth_test.go

@@ -0,0 +1,189 @@
+package middleware
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestNewAuth_MultiKeyAcceptsBothKeys(t *testing.T) {
+	cfg := AuthConfig{
+		Type:   "api-key",
+		Secret: "key-one,key-two",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	// First key should work
+	req1 := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req1.Header.Set("Authorization", "Bearer key-one")
+	rr1 := httptest.NewRecorder()
+	handler.ServeHTTP(rr1, req1)
+	if rr1.Code != http.StatusOK {
+		t.Errorf("expected 200 for first key, got %d", rr1.Code)
+	}
+
+	// Second key should work
+	req2 := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req2.Header.Set("Authorization", "Bearer key-two")
+	rr2 := httptest.NewRecorder()
+	handler.ServeHTTP(rr2, req2)
+	if rr2.Code != http.StatusOK {
+		t.Errorf("expected 200 for second key, got %d", rr2.Code)
+	}
+}
+
+func TestNewAuth_MultiKeyRejectsInvalidKey(t *testing.T) {
+	cfg := AuthConfig{
+		Type:   "api-key",
+		Secret: "key-one,key-two",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	// Invalid key should be rejected
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req.Header.Set("Authorization", "Bearer wrong-key")
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	if rr.Code != http.StatusUnauthorized {
+		t.Errorf("expected 401 for invalid key, got %d", rr.Code)
+	}
+}
+
+func TestNewAuth_MultiKeyWithSpaces(t *testing.T) {
+	// Keys with leading/trailing spaces should be trimmed
+	cfg := AuthConfig{
+		Type:   "api-key",
+		Secret: " key-one , key-two ",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req.Header.Set("Authorization", "Bearer key-one")
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	if rr.Code != http.StatusOK {
+		t.Errorf("expected 200 for trimmed key, got %d", rr.Code)
+	}
+}
+
+func TestNewAuth_SingleKeyStillWorks(t *testing.T) {
+	cfg := AuthConfig{
+		Type:   "api-key",
+		Secret: "my-single-key",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req.Header.Set("Authorization", "Bearer my-single-key")
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	if rr.Code != http.StatusOK {
+		t.Errorf("expected 200 for single key, got %d", rr.Code)
+	}
+}
+
+func TestNewAuth_NoneMode(t *testing.T) {
+	cfg := AuthConfig{
+		Type:   "none",
+		Secret: "",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	// No auth header needed in none mode
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	if rr.Code != http.StatusOK {
+		t.Errorf("expected 200 in none mode, got %d", rr.Code)
+	}
+}
+
+func TestNewAuth_MissingAuthHeader(t *testing.T) {
+	cfg := AuthConfig{
+		Type:   "api-key",
+		Secret: "test-key",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	if rr.Code != http.StatusUnauthorized {
+		t.Errorf("expected 401 for missing auth, got %d", rr.Code)
+	}
+}
+
+func TestNewAuth_InvalidBearerFormat(t *testing.T) {
+	cfg := AuthConfig{
+		Type:   "api-key",
+		Secret: "test-key",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req.Header.Set("Authorization", "Basic dGVzdDp0ZXN0")
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	if rr.Code != http.StatusUnauthorized {
+		t.Errorf("expected 401 for non-Bearer auth, got %d", rr.Code)
+	}
+}
+
+func TestNewAuth_RemovedKeyIsRejected(t *testing.T) {
+	// Simulate key rotation: only key-two is configured (key-one was removed)
+	cfg := AuthConfig{
+		Type:   "api-key",
+		Secret: "key-two",
+	}
+
+	mw := NewAuth(cfg)
+	handler := mw(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	// Old key should be rejected
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req.Header.Set("Authorization", "Bearer key-one")
+	rr := httptest.NewRecorder()
+	handler.ServeHTTP(rr, req)
+	if rr.Code != http.StatusUnauthorized {
+		t.Errorf("expected 401 for removed key, got %d", rr.Code)
+	}
+
+	// New key should work
+	req2 := httptest.NewRequest(http.MethodGet, "/api/v1/certificates", nil)
+	req2.Header.Set("Authorization", "Bearer key-two")
+	rr2 := httptest.NewRecorder()
+	handler.ServeHTTP(rr2, req2)
+	if rr2.Code != http.StatusOK {
+		t.Errorf("expected 200 for current key, got %d", rr2.Code)
+	}
+}