Implement etag; fix related bugs in encode and templates middlewares

modules/caddyhttp/encode/encode.go

@@ -135,6 +135,17 @@ func (rw *responseWriter) Write(p []byte) (int, error) {
 		}()
 	}
 
+	// before we write to the response, we need to make
+	// sure the header is written exactly once; we do
+	// that by checking if a status code has been set,
+	// and if so, that means we haven't written the
+	// header OR the default status code will be written
+	// by the standard library
+	if rw.statusCode > 0 {
+		rw.ResponseWriter.WriteHeader(rw.statusCode)
+		rw.statusCode = 0
+	}
+
 	switch {
 	case rw.w != nil:
 		n, err = rw.w.Write(p)
@@ -148,7 +159,7 @@ func (rw *responseWriter) Write(p []byte) (int, error) {
 	return n, err
 }
 
-// init should be called before we write a response, if rw.buf is not nil.
+// init should be called before we write a response, if rw.buf has contents.
 func (rw *responseWriter) init() {
 	if rw.Header().Get("Content-Encoding") == "" && rw.buf.Len() >= rw.config.MinLength {
 		rw.w = rw.config.writerPools[rw.encodingName].Get().(Encoder)
@@ -157,11 +168,6 @@ func (rw *responseWriter) init() {
 		rw.Header().Set("Content-Encoding", rw.encodingName)
 	}
 	rw.Header().Del("Accept-Ranges") // we don't know ranges for dynamically-encoded content
-	status := rw.statusCode
-	if status == 0 {
-		status = http.StatusOK
-	}
-	rw.ResponseWriter.WriteHeader(status)
 }
 
 // Close writes any remaining buffered response and
@@ -187,6 +193,14 @@ func (rw *responseWriter) Close() error {
 		default:
 			_, err = rw.ResponseWriter.Write(p)
 		}
+	} else if rw.statusCode != 0 {
+		// it is possible that a body was not written, and
+		// a header was not even written yet, even though
+		// we are closing; ensure the proper status code is
+		// written exactly once, or we risk breaking requests
+		// that rely on If-None-Match, for example
+		rw.ResponseWriter.WriteHeader(rw.statusCode)
+		rw.statusCode = 0
 	}
 	if rw.w != nil {
 		err2 := rw.w.Close()

modules/caddyhttp/fileserver/staticfiles.go

@@ -184,7 +184,9 @@ func (fsrv *FileServer) ServeHTTP(w http.ResponseWriter, r *http.Request) error
 	}
 	defer file.Close()
 
-	// TODO: Etag
+	// set the ETag - note that a conditional If-None-Match request is handled
+	// by http.ServeContent below, which checks against this ETag value
+	w.Header().Set("ETag", calculateEtag(info))
 
 	if w.Header().Get("Content-Type") == "" {
 		mtyp := mime.TypeByExtension(filepath.Ext(filename))
@@ -419,6 +421,17 @@ func fileHidden(filename string, hide []string) bool {
 	return false
 }
 
+// calculateEtag produces a strong etag by default, although, for
+// efficiency reasons, it does not actually consume the contents
+// of the file to make a hash of all the bytes. ¯\_(ツ)_/¯
+// Prefix the etag with "W/" to convert it into a weak etag.
+// See: https://tools.ietf.org/html/rfc7232#section-2.3
+func calculateEtag(d os.FileInfo) string {
+	t := strconv.FormatInt(d.ModTime().Unix(), 36)
+	s := strconv.FormatInt(d.Size(), 36)
+	return `"` + t + s + `"`
+}
+
 var defaultIndexNames = []string{"index.html"}
 
 const minBackoff, maxBackoff = 2, 5

modules/caddyhttp/templates/templates.go

@@ -22,9 +22,18 @@ func init() {
 // Templates is a middleware which execute response bodies as templates.
 type Templates struct {
 	FileRoot   string   `json:"file_root,omitempty"`
+	MIMETypes  []string `json:"mime_types,omitempty"`
 	Delimiters []string `json:"delimiters,omitempty"`
 }
 
+// Provision provisions t.
+func (t *Templates) Provision(ctx caddy.Context) error {
+	if t.MIMETypes == nil {
+		t.MIMETypes = defaultMIMETypes
+	}
+	return nil
+}
+
 // Validate ensures t has a valid configuration.
 func (t *Templates) Validate() error {
 	if len(t.Delimiters) != 0 && len(t.Delimiters) != 2 {
@@ -38,8 +47,16 @@ func (t *Templates) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddy
 	buf.Reset()
 	defer bufPool.Put(buf)
 
+	// shouldBuf determines whether to execute templates on this response,
+	// since generally we will not want to execute for images or CSS, etc.
 	shouldBuf := func(status int) bool {
-		return strings.HasPrefix(w.Header().Get("Content-Type"), "text/")
+		ct := w.Header().Get("Content-Type")
+		for _, mt := range t.MIMETypes {
+			if strings.Contains(ct, mt) {
+				return true
+			}
+		}
+		return false
 	}
 
 	rec := caddyhttp.NewResponseRecorder(w, buf, shouldBuf)
@@ -59,9 +76,14 @@ func (t *Templates) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddy
 
 	w.Header().Set("Content-Length", strconv.Itoa(buf.Len()))
 	w.Header().Del("Accept-Ranges") // we don't know ranges for dynamically-created content
-	w.Header().Del("Etag")          // don't know a way to quickly generate etag for dynamic content
 	w.Header().Del("Last-Modified") // useless for dynamic content since it's always changing
 
+	// we don't know a way to guickly generate etag for dynamic content,
+	// but we can convert this to a weak etag to kind of indicate that
+	if etag := w.Header().Get("ETag"); etag != "" {
+		w.Header().Set("ETag", "W/"+etag)
+	}
+
 	w.WriteHeader(rec.Status())
 	io.Copy(w, buf)
 
@@ -110,8 +132,15 @@ func (vrw *virtualResponseWriter) Write(data []byte) (int, error) {
 	return vrw.body.Write(data)
 }
 
+var defaultMIMETypes = []string{
+	"text/html",
+	"text/plain",
+	"text/markdown",
+}
+
 // Interface guards
 var (
+	_ caddy.Provisioner           = (*Templates)(nil)
 	_ caddy.Validator             = (*Templates)(nil)
 	_ caddyhttp.MiddlewareHandler = (*Templates)(nil)
 )