cmd/strelaypoolsrv, lib/api: Factor out static asset serving (#6624)

build.go

@@ -687,7 +687,7 @@ func listFiles(dir string) []string {
 
 func rebuildAssets() {
 	os.Setenv("SOURCE_DATE_EPOCH", fmt.Sprint(buildStamp()))
-	runPrint(goCmd, "generate", "github.com/syncthing/syncthing/lib/auto", "github.com/syncthing/syncthing/cmd/strelaypoolsrv/auto")
+	runPrint(goCmd, "generate", "github.com/syncthing/syncthing/lib/api/auto", "github.com/syncthing/syncthing/cmd/strelaypoolsrv/auto")
 }
 
 func lazyRebuildAssets() {

cmd/strelaypoolsrv/main.go

@@ -12,7 +12,6 @@ import (
 	"io"
 	"io/ioutil"
 	"log"
-	"mime"
 	"net"
 	"net/http"
 	"net/url"
@@ -27,6 +26,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/syncthing/syncthing/cmd/strelaypoolsrv/auto"
+	"github.com/syncthing/syncthing/lib/assets"
 	"github.com/syncthing/syncthing/lib/rand"
 	"github.com/syncthing/syncthing/lib/relay/client"
 	"github.com/syncthing/syncthing/lib/sync"
@@ -263,78 +263,22 @@ func handleMetrics(w http.ResponseWriter, r *http.Request) {
 func handleAssets(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Cache-Control", "no-cache, must-revalidate")
 
-	assets := auto.Assets()
 	path := r.URL.Path[1:]
 	if path == "" {
 		path = "index.html"
 	}
 
-	bs, ok := assets[path]
+	content, ok := auto.Assets()[path]
 	if !ok {
 		w.WriteHeader(http.StatusNotFound)
 		return
 	}
 
-	etag := fmt.Sprintf("%d", auto.Generated)
+	assets.Serve(w, r, assets.Asset{
-	modified := time.Unix(auto.Generated, 0).UTC()
+		ContentGz: content,
-
+		Filename:  path,
-	w.Header().Set("Last-Modified", modified.Format(http.TimeFormat))
+		Modified:  time.Unix(auto.Generated, 0).UTC(),
-	w.Header().Set("Etag", etag)
+	})
-
-	mtype := mimeTypeForFile(path)
-	if len(mtype) != 0 {
-		w.Header().Set("Content-Type", mtype)
-	}
-
-	if t, err := time.Parse(http.TimeFormat, r.Header.Get("If-Modified-Since")); err == nil && modified.Add(time.Second).After(t) {
-		w.WriteHeader(http.StatusNotModified)
-		return
-	}
-
-	if match := r.Header.Get("If-None-Match"); match != "" {
-		if strings.Contains(match, etag) {
-			w.WriteHeader(http.StatusNotModified)
-			return
-		}
-	}
-	if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
-		w.Header().Set("Content-Encoding", "gzip")
-		w.Header().Set("Content-Length", strconv.Itoa(len(bs)))
-		io.WriteString(w, bs)
-	} else {
-		// ungzip if browser not send gzip accepted header
-		var gr *gzip.Reader
-		gr, _ = gzip.NewReader(strings.NewReader(bs))
-		io.Copy(w, gr)
-		gr.Close()
-	}
-}
-
-func mimeTypeForFile(file string) string {
-	// We use a built in table of the common types since the system
-	// TypeByExtension might be unreliable. But if we don't know, we delegate
-	// to the system.
-	ext := filepath.Ext(file)
-	switch ext {
-	case ".htm", ".html":
-		return "text/html"
-	case ".css":
-		return "text/css"
-	case ".js":
-		return "application/javascript"
-	case ".json":
-		return "application/json"
-	case ".png":
-		return "image/png"
-	case ".ttf":
-		return "application/x-font-ttf"
-	case ".woff":
-		return "application/x-font-woff"
-	case ".svg":
-		return "image/svg+xml"
-	default:
-		return mime.TypeByExtension(ext)
-	}
 }
 
 func handleRequest(w http.ResponseWriter, r *http.Request) {

lib/api/api_statics.go

@@ -7,18 +7,15 @@
 package api
 
 import (
-	"compress/gzip"
 	"fmt"
-	"io"
-	"mime"
 	"net/http"
 	"os"
 	"path/filepath"
-	"strconv"
 	"strings"
 	"time"
 
-	"github.com/syncthing/syncthing/lib/auto"
+	"github.com/syncthing/syncthing/lib/api/auto"
+	"github.com/syncthing/syncthing/lib/assets"
 	"github.com/syncthing/syncthing/lib/config"
 	"github.com/syncthing/syncthing/lib/sync"
 )
@@ -111,7 +108,7 @@ func (s *staticsServer) serveAsset(w http.ResponseWriter, r *http.Request) {
 	if s.assetDir != "" {
 		p := filepath.Join(s.assetDir, theme, filepath.FromSlash(file))
 		if _, err := os.Stat(p); err == nil {
-			mtype := s.mimeTypeForFile(file)
+			mtype := assets.MimeTypeForFile(file)
 			if len(mtype) != 0 {
 				w.Header().Set("Content-Type", mtype)
 			}
@@ -127,7 +124,7 @@ func (s *staticsServer) serveAsset(w http.ResponseWriter, r *http.Request) {
 		if s.assetDir != "" {
 			p := filepath.Join(s.assetDir, config.DefaultTheme, filepath.FromSlash(file))
 			if _, err := os.Stat(p); err == nil {
-				mtype := s.mimeTypeForFile(file)
+				mtype := assets.MimeTypeForFile(file)
 				if len(mtype) != 0 {
 					w.Header().Set("Content-Type", mtype)
 				}
@@ -144,39 +141,11 @@ func (s *staticsServer) serveAsset(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	etag := fmt.Sprintf("%d", modificationTime.Unix())
+	assets.Serve(w, r, assets.Asset{
-	w.Header().Set("Last-Modified", modificationTime.Format(http.TimeFormat))
+		ContentGz: bs,
-	w.Header().Set("Etag", etag)
+		Filename:  file,
-
+		Modified:  modificationTime,
-	if t, err := time.Parse(http.TimeFormat, r.Header.Get("If-Modified-Since")); err == nil {
+	})
-		if modificationTime.Equal(t) || modificationTime.Before(t) {
-			w.WriteHeader(http.StatusNotModified)
-			return
-		}
-	}
-
-	if match := r.Header.Get("If-None-Match"); match != "" {
-		if strings.Contains(match, etag) {
-			w.WriteHeader(http.StatusNotModified)
-			return
-		}
-	}
-
-	mtype := s.mimeTypeForFile(file)
-	if len(mtype) != 0 {
-		w.Header().Set("Content-Type", mtype)
-	}
-	if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
-		w.Header().Set("Content-Encoding", "gzip")
-		w.Header().Set("Content-Length", strconv.Itoa(len(bs)))
-		io.WriteString(w, bs)
-	} else {
-		// ungzip if browser not send gzip accepted header
-		var gr *gzip.Reader
-		gr, _ = gzip.NewReader(strings.NewReader(bs))
-		io.Copy(w, gr)
-		gr.Close()
-	}
 }
 
 func (s *staticsServer) serveThemes(w http.ResponseWriter, r *http.Request) {
@@ -185,33 +154,6 @@ func (s *staticsServer) serveThemes(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
-func (s *staticsServer) mimeTypeForFile(file string) string {
-	// We use a built in table of the common types since the system
-	// TypeByExtension might be unreliable. But if we don't know, we delegate
-	// to the system. All our files are UTF-8.
-	ext := filepath.Ext(file)
-	switch ext {
-	case ".htm", ".html":
-		return "text/html; charset=utf-8"
-	case ".css":
-		return "text/css; charset=utf-8"
-	case ".js":
-		return "application/javascript; charset=utf-8"
-	case ".json":
-		return "application/json; charset=utf-8"
-	case ".png":
-		return "image/png"
-	case ".ttf":
-		return "application/x-font-ttf"
-	case ".woff":
-		return "application/x-font-woff"
-	case ".svg":
-		return "image/svg+xml; charset=utf-8"
-	default:
-		return mime.TypeByExtension(ext)
-	}
-}
-
 func (s *staticsServer) setTheme(theme string) {
 	s.mut.Lock()
 	s.theme = theme

lib/api/auto/auto_test.go

@@ -13,7 +13,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/syncthing/syncthing/lib/auto"
+	"github.com/syncthing/syncthing/lib/api/auto"
 )
 
 func TestAssets(t *testing.T) {

lib/api/auto/doc.go

@@ -4,7 +4,7 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this file,
 // You can obtain one at https://mozilla.org/MPL/2.0/.
 
-//go:generate go run ../../script/genassets.go -o gui.files.go ../../gui
+//go:generate go run ../../../script/genassets.go -o gui.files.go ../../../gui
 
 // Package auto contains auto generated files for web assets.
 package auto

lib/assets/assets.go

@@ -0,0 +1,97 @@
+// Copyright (C) 2014-2020 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// Package assets hold utilities for serving static assets.
+//
+// The actual assets live in auto subpackages instead of here,
+// because the set of assets varies per program.
+package assets
+
+import (
+	"compress/gzip"
+	"fmt"
+	"io"
+	"mime"
+	"net/http"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Asset is the type of arguments to Serve.
+type Asset struct {
+	ContentGz string    // gzipped contents of asset.
+	Filename  string    // Original filename, determines Content-Type.
+	Modified  time.Time // Determines ETag and Last-Modified.
+}
+
+// Serve writes a gzipped asset to w.
+func Serve(w http.ResponseWriter, r *http.Request, asset Asset) {
+	header := w.Header()
+
+	mtype := MimeTypeForFile(asset.Filename)
+	if mtype != "" {
+		header.Set("Content-Type", mtype)
+	}
+
+	etag := fmt.Sprintf(`"%x"`, asset.Modified.Unix())
+	header.Set("ETag", etag)
+	header.Set("Last-Modified", asset.Modified.Format(http.TimeFormat))
+
+	t, err := time.Parse(http.TimeFormat, r.Header.Get("If-Modified-Since"))
+	if err == nil && !asset.Modified.After(t) {
+		w.WriteHeader(http.StatusNotModified)
+		return
+	}
+
+	if r.Header.Get("If-None-Match") == etag {
+		w.WriteHeader(http.StatusNotModified)
+		return
+	}
+
+	if strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
+		header.Set("Content-Encoding", "gzip")
+		header.Set("Content-Length", strconv.Itoa(len(asset.ContentGz)))
+		io.WriteString(w, asset.ContentGz)
+	} else {
+		// gunzip for browsers that don't want gzip.
+		var gr *gzip.Reader
+		gr, _ = gzip.NewReader(strings.NewReader(asset.ContentGz))
+		io.Copy(w, gr)
+		gr.Close()
+	}
+}
+
+// MimeTypeForFile returns the appropriate MIME type for an asset,
+// based on the filename.
+//
+// We use a built in table of the common types since the system
+// TypeByExtension might be unreliable. But if we don't know, we delegate
+// to the system. All our text files are in UTF-8.
+func MimeTypeForFile(file string) string {
+	ext := filepath.Ext(file)
+	switch ext {
+	case ".htm", ".html":
+		return "text/html; charset=utf-8"
+	case ".css":
+		return "text/css; charset=utf-8"
+	case ".js":
+		return "application/javascript; charset=utf-8"
+	case ".json":
+		return "application/json; charset=utf-8"
+	case ".png":
+		return "image/png"
+	case ".ttf":
+		return "application/x-font-ttf"
+	case ".woff":
+		return "application/x-font-woff"
+	case ".svg":
+		return "image/svg+xml; charset=utf-8"
+	default:
+		return mime.TypeByExtension(ext)
+	}
+}

lib/assets/assets_test.go

@@ -0,0 +1,103 @@
+// Copyright (C) 2020 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package assets
+
+import (
+	"bytes"
+	"compress/gzip"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+func compress(s string) string {
+	var sb strings.Builder
+	gz := gzip.NewWriter(&sb)
+
+	io.WriteString(gz, s)
+	gz.Close()
+	return sb.String()
+}
+
+func decompress(p []byte) (out []byte) {
+	r, err := gzip.NewReader(bytes.NewBuffer(p))
+	if err == nil {
+		out, err = ioutil.ReadAll(r)
+	}
+	if err != nil {
+		panic(err)
+	}
+	return out
+}
+
+func TestServe(t *testing.T) {
+	indexHTML := `<html>Hello, world!</html>`
+	indexGz := compress(indexHTML)
+
+	handler := func(w http.ResponseWriter, r *http.Request) {
+		Serve(w, r, Asset{
+			ContentGz: indexGz,
+			Filename:  r.URL.Path[1:],
+			Modified:  time.Unix(0, 0),
+		})
+	}
+
+	for _, acceptGzip := range []bool{true, false} {
+		r := httptest.NewRequest("GET", "http://localhost/index.html", nil)
+		if acceptGzip {
+			r.Header.Set("accept-encoding", "gzip, deflate")
+		}
+
+		w := httptest.NewRecorder()
+		handler(w, r)
+		res := w.Result()
+
+		if res.StatusCode != http.StatusOK {
+			t.Fatalf("wanted OK, got status %d", res.StatusCode)
+		}
+		if ctype := res.Header.Get("Content-Type"); ctype != "text/html; charset=utf-8" {
+			t.Errorf("unexpected Content-Type %q", ctype)
+		}
+		// ETags must be quoted ASCII strings:
+		// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag
+		if etag := res.Header.Get("ETag"); etag != `"0"` {
+			t.Errorf("unexpected ETag %q", etag)
+		}
+
+		body, _ := ioutil.ReadAll(res.Body)
+		if acceptGzip {
+			body = decompress(body)
+		}
+		if string(body) != indexHTML {
+			t.Fatalf("unexpected content %q", body)
+		}
+	}
+
+	r := httptest.NewRequest("GET", "http://localhost/index.html", nil)
+	r.Header.Set("if-none-match", `"0"`)
+	w := httptest.NewRecorder()
+	handler(w, r)
+	res := w.Result()
+
+	if res.StatusCode != http.StatusNotModified {
+		t.Fatalf("wanted NotModified, got status %d", res.StatusCode)
+	}
+
+	r = httptest.NewRequest("GET", "http://localhost/index.html", nil)
+	r.Header.Set("if-modified-since", time.Now().Format(http.TimeFormat))
+	w = httptest.NewRecorder()
+	handler(w, r)
+	res = w.Result()
+
+	if res.StatusCode != http.StatusNotModified {
+		t.Fatalf("wanted NotModified, got status %d", res.StatusCode)
+	}
+}