add favicon hiding when not authenticated

Signed-off-by: Ronni Skansing <rskansing@gmail.com>

backend/app/administration.go

@@ -220,12 +220,13 @@ const (
 
 // administrationServer is the administrationServer app
 type administrationServer struct {
-	Server          *http.Server
-	router          *gin.Engine
-	logger          *zap.SugaredLogger
-	production      bool
-	embedBackendFS  *embed.FS
-	certMagicConfig *certmagic.Config
+	Server             *http.Server
+	router             *gin.Engine
+	logger             *zap.SugaredLogger
+	production         bool
+	embedBackendFS     *embed.FS
+	certMagicConfig    *certmagic.Config
+	softSessionHandler gin.HandlerFunc
 }
 
 // NewAdministrationServer creates a new administration app
@@ -240,10 +241,11 @@ func NewAdministrationServer(
 	router = setupRoutes(router, controllers, middlewares)
 
 	return &administrationServer{
-		router:          router,
-		logger:          logger,
-		production:      production,
-		certMagicConfig: certMagicConfig,
+		router:             router,
+		logger:             logger,
+		production:         production,
+		certMagicConfig:    certMagicConfig,
+		softSessionHandler: middlewares.SoftSessionHandler,
 	}
 }
 
@@ -713,6 +715,15 @@ func (a *administrationServer) loadEmbeddedFileSystem(
 	embedFS := frontend.GetEmbededFS()
 	// make embedded .html work
 	frontend.LoadHTMLFromEmbedFS(a.router, *embedFS, "build/*.html")
+	// serve favicons only to authenticated users — unauthenticated requests get 404
+	// so the file is not indexable by scanners probing common paths
+	for _, faviconPath := range []string{"/favicon.ico", "/favicon.png"} {
+		fp := faviconPath
+		a.router.GET(fp, a.softSessionHandler, func(c *gin.Context) {
+			name := fp[1:] // strip leading /
+			c.FileFromFS("build/"+name, http.FS(*embedFS))
+		})
+	}
 	rootDir, err := embedFS.ReadDir("build")
 	if err != nil {
 		return errs.Wrap(err)
@@ -728,6 +739,10 @@ func (a *administrationServer) loadEmbeddedFileSystem(
 				})
 				continue
 			}
+			// skip favicons — registered separately with session gating
+			if path == "favicon.png" || path == "favicon.ico" {
+				continue
+			}
 			// any file in the root folder gets server as a file
 			a.router.GET("/"+path, func(c *gin.Context) {
 				c.FileFromFS("build/"+path, http.FS(*embedFS))

backend/app/middleware.go

@@ -11,9 +11,10 @@ import (
 
 // Middlwares is a collection of middlewares
 type Middlewares struct {
-	IPLimiter        gin.HandlerFunc
-	LoginRateLimiter gin.HandlerFunc
-	SessionHandler   gin.HandlerFunc
+	IPLimiter          gin.HandlerFunc
+	LoginRateLimiter   gin.HandlerFunc
+	SessionHandler     gin.HandlerFunc
+	SoftSessionHandler gin.HandlerFunc
 }
 
 // NewMiddlewares creates a collection of middlewares
@@ -36,11 +37,17 @@ func NewMiddlewares(
 		utils.JSONResponseHandler,
 		logger,
 	)
+	softSessionHandler := middleware.NewSoftSessionHandler(
+		services.Session,
+		services.User,
+		logger,
+	)
 
 	return &Middlewares{
-		IPLimiter:        ipLimiter,
-		LoginRateLimiter: loginThrottle,
-		SessionHandler:   sessionHandler,
+		IPLimiter:          ipLimiter,
+		LoginRateLimiter:   loginThrottle,
+		SessionHandler:     sessionHandler,
+		SoftSessionHandler: softSessionHandler,
 	}
 }
 

backend/middleware/session.go

@@ -3,6 +3,7 @@ package middleware
 import (
 	"crypto/sha256"
 	"crypto/subtle"
+	"net/http"
 	"time"
 
 	"github.com/gin-gonic/gin"
@@ -15,6 +16,32 @@ import (
 	"go.uber.org/zap"
 )
 
+// NewSoftSessionHandler is like NewSessionHandler but returns 404 on auth failure
+// instead of 401, so unauthenticated requests are indistinguishable from missing resources.
+func NewSoftSessionHandler(
+	sessionService *service.Session,
+	userService *service.User,
+	logger *zap.SugaredLogger,
+) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		isValidAPISession := handleAPISession(c, userService, logger)
+		if isValidAPISession {
+			return
+		}
+		s, err := sessionService.GetAndExtendSession(c)
+		if err != nil {
+			c.AbortWithStatus(http.StatusNotFound)
+			return
+		}
+		if s.User == nil {
+			c.AbortWithStatus(http.StatusNotFound)
+			return
+		}
+		controller.SetSessionInGinContext(c, s)
+		c.Next()
+	}
+}
+
 // NewSessionHandler creates a middleware that authenticates the user
 // by checking it has a session, and if it does, it extends the session and puts
 // the user and the session in the gin context.