Add ETag for static files

1 files changed, 37 insertions, 3 deletions

diff --git a/roseh.moe.go b/roseh.moe.go
index 206679b..95f303c 100644
--- a/roseh.moe.go
+++ b/roseh.moe.go
@@ -48,8 +48,6 @@ var (
 	holeTempDir = flag.String("hole-temp-dir", "hole", "directory to store temporary files for the wormhole")
 	codeDir     = flag.String("code-dir", "code", "directory to serve git repos")
 	nezuko      = flag.String("nezuko", "nezuko", "nezuko partition")
-
-	serverStartTime = time.Now()
 )
 
 var notepadPassword, secretKey, authenticatorKey []byte
@@ -228,6 +226,31 @@ func stallmanShooter(w http.ResponseWriter, _ *http.Request) {
 //go:embed static
 var staticFiles embed.FS
 
+var staticFileHashes = buildStaticFileHashes()
+
+func buildStaticFileHashes() map[string]string {
+	hashMap := make(map[string]string)
+	if err := fs.WalkDir(staticFiles, ".", func(path string, d fs.DirEntry, err error) error {
+		if err != nil || d.IsDir() {
+			return err
+		}
+		f, err := staticFiles.Open(path)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		h := sha256.New()
+		if _, err := io.Copy(h, f); err != nil {
+			return err
+		}
+		hashMap[path] = `"` + base64.RawURLEncoding.EncodeToString(h.Sum(nil)[:8]) + `"`
+		return nil
+	}); err != nil {
+		panic(fmt.Sprintf("Build static file hash map: %s", err))
+	}
+	return hashMap
+}
+
 func serveStaticFile(w http.ResponseWriter, r *http.Request, path string) {
 	f, err := staticFiles.Open(path)
 	if err != nil {
@@ -235,7 +258,18 @@ func serveStaticFile(w http.ResponseWriter, r *http.Request, path string) {
 		return
 	}
 	defer f.Close()
-	http.ServeContent(w, r, path, serverStartTime, f.(io.ReadSeeker))
+	stat, err := f.Stat()
+	if err != nil {
+		log.Printf("Warning: stat static file: %s", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+	if stat.IsDir() {
+		notFound(w, r)
+		return
+	}
+	w.Header().Set("ETag", staticFileHashes[path])
+	http.ServeContent(w, r, path, time.Time{}, f.(io.ReadSeeker))
 }
 
 func static(w http.ResponseWriter, r *http.Request) {