hub: return 404 status for unknown frontend routes (#2414)

internal/hub/server.go

@@ -28,6 +28,32 @@ func modifyIndexHTML(hub *Hub, html []byte) string {
 	return strings.Replace(htmlContent, "\"{info}\"", string(content), 1)
 }
 
+// isAppRoute reports whether urlPath matches a frontend route, so unknown paths
+// can be served with a 404 status. The base path prefix is optional because
+// reverse proxies may or may not strip it before forwarding.
+//
+// Keep in sync with routes in internal/site/src/components/router.tsx.
+func isAppRoute(urlPath, basePath string) bool {
+	urlPath = strings.ToLower(urlPath)
+	if base := strings.TrimSuffix(strings.ToLower(basePath), "/"); base != "" {
+		if rest, ok := strings.CutPrefix(urlPath, base); ok && (rest == "" || rest[0] == '/') {
+			urlPath = rest
+		}
+	}
+	urlPath = strings.TrimSuffix(urlPath, "/")
+	switch urlPath {
+	case "", "/containers", "/smart", "/monitors", "/settings", "/forgot-password", "/request-otp":
+		return true
+	}
+	// routes with a single required (/system/:id) or optional (/settings/:name?) param
+	for _, prefix := range [...]string{"/system/", "/settings/"} {
+		if param, ok := strings.CutPrefix(urlPath, prefix); ok {
+			return param != "" && !strings.Contains(param, "/")
+		}
+	}
+	return false
+}
+
 func getPublicAppInfo(hub *Hub) PublicAppInfo {
 	parsedURL, _ := url.Parse(hub.appURL)
 	info := PublicAppInfo{

internal/hub/server_production.go

@@ -18,6 +18,7 @@ import (
 func (h *Hub) startServer(se *core.ServeEvent) error {
 	indexFile, _ := fs.ReadFile(site.DistDirFS, "index.html")
 	html := modifyIndexHTML(h, indexFile)
+	basePath := getPublicAppInfo(h).BASE_PATH
 	// set up static asset serving
 	staticPaths := [2]string{"/static/", "/assets/"}
 	serveStatic := apis.Static(site.DistDirFS, false)
@@ -36,7 +37,13 @@ func (h *Hub) startServer(se *core.ServeEvent) error {
 			e.Response.Header().Del("X-Frame-Options")
 			e.Response.Header().Set("Content-Security-Policy", csp)
 		}
-		return e.HTML(http.StatusOK, html)
+		// still serve the app for unknown paths (it renders a 404 page),
+		// but with a 404 status so scanners and fail2ban see the miss
+		status := http.StatusOK
+		if !isAppRoute(e.Request.URL.Path, basePath) {
+			status = http.StatusNotFound
+		}
+		return e.HTML(status, html)
 	})
 	return nil
 }

internal/hub/server_test.go

@@ -0,0 +1,59 @@
+//go:build testing
+
+package hub
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsAppRoute(t *testing.T) {
+	tests := []struct {
+		path     string
+		basePath string
+		want     bool
+	}{
+		// known routes
+		{"/", "/", true},
+		{"/containers", "/", true},
+		{"/containers/", "/", true},
+		{"/Containers", "/", true},
+		{"/smart", "/", true},
+		{"/monitors", "/", true},
+		{"/forgot-password", "/", true},
+		{"/request-otp", "/", true},
+		{"/system/abc123", "/", true},
+		{"/system/abc123/", "/", true},
+		{"/settings", "/", true},
+		{"/settings/general", "/", true},
+
+		// unknown paths
+		{"/.env", "/", false},
+		{"/phpinfo.php", "/", false},
+		{"/wp-admin/", "/", false},
+		{"/.git/config", "/", false},
+		{"/system", "/", false},
+		{"/system/", "/", false},
+		{"/system/abc/def", "/", false},
+		{"/settings/general/extra", "/", false},
+		{"/containersx", "/", false},
+
+		// base path, prefix not stripped by proxy
+		{"/beszel", "/beszel/", true},
+		{"/beszel/", "/beszel/", true},
+		{"/beszel/containers", "/beszel/", true},
+		{"/beszel/system/abc123", "/beszel/", true},
+		{"/beszel/.env", "/beszel/", false},
+		{"/beszelx", "/beszel/", false},
+
+		// base path, prefix stripped by proxy
+		{"/", "/beszel/", true},
+		{"/containers", "/beszel/", true},
+		{"/.env", "/beszel/", false},
+	}
+
+	for _, tt := range tests {
+		assert.Equal(t, tt.want, isAppRoute(tt.path, tt.basePath), "path=%q basePath=%q", tt.path, tt.basePath)
+	}
+}