MM-46004 Add Focalboard webpack dev server to dev CSP policy (#20888)

* MM-46004 Add Focalboard webpack dev server to dev CSP policy

* Fix tests and prevent duplicated CSP values

web/handlers.go

@@ -87,16 +87,17 @@ type Handler struct {
 }
 
 func generateDevCSP(c Context) string {
+	var devCSP []string
+
 	// Add unsafe-eval to the content security policy for faster source maps in development mode
-	devCSPMap := make(map[string]bool)
 	if model.BuildNumber == "dev" {
-		devCSPMap["unsafe-eval"] = true
+		devCSP = append(devCSP, "'unsafe-eval'")
 	}
 
 	// Add unsafe-inline to unlock extensions like React & Redux DevTools in Firefox
 	// see https://github.com/reduxjs/redux-devtools/issues/380
 	if model.BuildNumber == "dev" {
-		devCSPMap["unsafe-inline"] = true
+		devCSP = append(devCSP, "'unsafe-inline'")
 	}
 
 	// Add supported flags for debugging during development, even if not on a dev build.
@@ -118,21 +119,29 @@ func generateDevCSP(c Context) string {
 			// Honour only supported keys
 			switch devFlagKey {
 			case "unsafe-eval", "unsafe-inline":
-				devCSPMap[devFlagKey] = true
+				if model.BuildNumber == "dev" {
+					// These flags are added automatically for dev builds
+					continue
+				}
+
+				devCSP = append(devCSP, "'"+devFlagKey+"'")
 			default:
 				c.Logger.Warn("Unrecognized developer flag", mlog.String("developer_flag", devFlagKVStr))
 			}
 		}
 	}
-	var devCSP string
-	supportedCSPFlags := []string{"unsafe-eval", "unsafe-inline"}
-	for _, devCSPFlag := range supportedCSPFlags {
-		if devCSPMap[devCSPFlag] {
-			devCSP += fmt.Sprintf(" '%s'", devCSPFlag)
-		}
+
+	// Add flags for Webpack dev servers used by other products during development
+	if model.BuildNumber == "dev" {
+		// Focalboard runs on http://localhost:9006
+		devCSP = append(devCSP, "http://localhost:9006")
 	}
 
-	return devCSP
+	if len(devCSP) == 0 {
+		return ""
+	}
+
+	return " " + strings.Join(devCSP, " ")
 }
 
 func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {

web/handlers_test.go

@@ -388,7 +388,7 @@ func TestHandlerServeCSPHeader(t *testing.T) {
 		response := httptest.NewRecorder()
 		handler.ServeHTTP(response, request)
 		assert.Equal(t, 200, response.Code)
-		assert.Equal(t, []string{"frame-ancestors 'self'; script-src 'self' cdn.rudderlabs.com 'unsafe-eval' 'unsafe-inline'"}, response.Header()["Content-Security-Policy"])
+		assert.Equal(t, []string{"frame-ancestors 'self'; script-src 'self' cdn.rudderlabs.com 'unsafe-eval' 'unsafe-inline' http://localhost:9006"}, response.Header()["Content-Security-Policy"])
 	})
 
 }
@@ -411,9 +411,9 @@ func TestGenerateDevCSP(t *testing.T) {
 
 		devCSP := generateDevCSP(*c)
 
-		assert.Equal(t, " 'unsafe-eval' 'unsafe-inline'", devCSP)
-
+		assert.Equal(t, " 'unsafe-eval' 'unsafe-inline' http://localhost:9006", devCSP)
 	})
+
 	t.Run("allowed dev flags", func(t *testing.T) {
 		th := Setup(t)
 		defer th.TearDown()
@@ -436,7 +436,7 @@ func TestGenerateDevCSP(t *testing.T) {
 
 		devCSP := generateDevCSP(*c)
 
-		assert.Equal(t, " 'unsafe-eval' 'unsafe-inline'", devCSP)
+		assert.Equal(t, " 'unsafe-inline' 'unsafe-eval'", devCSP)
 	})
 
 	t.Run("partial dev flags", func(t *testing.T) {