server: use custom error page

server/pages.go

@@ -31,7 +31,8 @@ type Page interface {
 func writePage(p Page, w http.ResponseWriter) {
 	t, err := template.ParseFS(staticFS, "static/templates/" + p.SourceFile())
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
+		http.Error(w, "Internal server error: " + err.Error(),
+			http.StatusInternalServerError)
 		return
 	}
 
@@ -41,6 +42,21 @@ func writePage(p Page, w http.ResponseWriter) {
 	}
 }
 
+type ErrorPage struct {
+	Status string
+	Reason string
+}
+
+func MakeErrorPage(status, reason string) (p ErrorPage) {
+	p.Status = status
+	p.Reason = reason
+	return
+}
+
+func (p ErrorPage) SourceFile() string { return "error.html" }
+func (p ErrorPage) Title() string { return "" }
+func (p ErrorPage) Body() template.HTML { return template.HTML("") }
+
 type IndexPage struct {
 	Showcase string
 }

server/server.go

@@ -28,6 +28,16 @@ var artistPages map[string]map[string]ArtistPage
 // mapping of artist names to album names to pages
 var albumPages map[string]map[string]AlbumPage
 
+func httpErrorReason(w http.ResponseWriter, error int, reason string) {
+	errorName := fmt.Sprintf("%d %s", error, http.StatusText(error))
+	w.WriteHeader(error)
+	writePage(MakeErrorPage(errorName, reason), w)
+}
+
+func httpError(w http.ResponseWriter, error int) {
+	httpErrorReason(w, error, "")
+}
+
 func doIndexPage(w http.ResponseWriter, req *http.Request) {
 	writePage(indexPage, w)
 }
@@ -64,13 +74,13 @@ func detectTextType(fileName string) string {
 
 func serveStaticFiles(w http.ResponseWriter, req *http.Request) {
 	if strings.HasPrefix(req.RequestURI, "/static/templates/") {
-		http.Error(w, "forbidden", http.StatusForbidden)
+		httpError(w, http.StatusForbidden)
 		return
 	}
 
 	contents, err := staticFS.ReadFile(req.RequestURI[1:])
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusNotFound)
+		httpError(w, http.StatusNotFound)
 		return
 	}
 
@@ -86,30 +96,31 @@ func serveStaticFiles(w http.ResponseWriter, req *http.Request) {
 func serveMediaDirectory(w http.ResponseWriter, req *http.Request) {
 	path, err := url.QueryUnescape("/" + strings.SplitN(req.RequestURI[1:], "/", 2)[1])
 	if err != nil {
-		http.Error(w, "bad request", http.StatusBadRequest)
+		httpError(w, http.StatusBadRequest)
 		return
 	}
 
 	filePath := musicindex.MediaDirectory() + path
 
-	if strings.Contains(path, "/..") || strings.Contains(path, "/.") {
+	if strings.Contains(path, "/../") || strings.Contains(path, "/./") {
-		http.Error(w, "forbidden", http.StatusForbidden)
+		httpError(w, http.StatusForbidden)
 		return
 	}
 
 	stat, err := os.Stat(filePath)
 	if err != nil {
-		http.Error(w, "not found", http.StatusNotFound)
+		httpError(w, http.StatusNotFound)
 		return
 	}
 	if stat.IsDir() {
-		http.Error(w, "is a directory; maybe you are looking for " + path, http.StatusForbidden)
+		httpErrorReason(w, http.StatusForbidden,
+			"is a directory; maybe you are looking for " + path)
 		return
 	}
 
 	f, err := os.Open(filePath)
 	if err != nil {
-		http.Error(w, "not found", http.StatusNotFound)
+		httpError(w, http.StatusNotFound)
 		return
 	}
 	defer f.Close()
@@ -120,14 +131,14 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 	// test artist
 	rx, err := regexp.Compile("^/([^/?]+)/?(\\?.*)?$")
 	if err != nil {
-		http.Error(w, "internal server error", http.StatusInternalServerError)
+		httpError(w, http.StatusInternalServerError)
 		return
 	}
 
 	if (rx.MatchString(req.RequestURI)) {
 		artist, err := url.QueryUnescape(rx.FindStringSubmatch(req.RequestURI)[1])
 		if err != nil {
-			http.Error(w, "bad request", http.StatusBadRequest)
+			httpError(w, http.StatusBadRequest)
 			return
 		}
 		if musicindex.ArtistExists(artist) {
@@ -142,14 +153,14 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 		}
 
 		// artist not found
-		http.Error(w, "not found", http.StatusNotFound)
+		httpError(w, http.StatusNotFound)
 		return
 	}
 
 	// test album tarball
 	rx, err = regexp.Compile("^/([^/?]+)/([^/?]+)\\.tar\\.gz$")
 	if err != nil {
-		http.Error(w, "internal server error", http.StatusInternalServerError)
+		httpError(w, http.StatusInternalServerError)
 		return
 	}
 
@@ -157,12 +168,12 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 		captures := rx.FindStringSubmatch(req.RequestURI)
 		artist, err := url.QueryUnescape(captures[1])
 		if err != nil {
-			http.Error(w, "bad request", http.StatusBadRequest)
+			httpError(w, http.StatusBadRequest)
 			return
 		}
 		albumName, err := url.QueryUnescape(captures[2])
 		if err != nil {
-			http.Error(w, "bad request", http.StatusBadRequest)
+			httpError(w, http.StatusBadRequest)
 			return
 		}
 
@@ -171,8 +182,7 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 			if ok {
 				f, err := os.Open(album.Tarball)
 				if err != nil {
-					http.Error(w, "internal server error: " + err.Error(),
+					httpErrorReason(w, http.StatusInternalServerError, err.Error())
-						http.StatusInternalServerError)
 					return
 				}
 				defer f.Close()
@@ -187,14 +197,14 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 		}
 
 		// artist or album not found
-		http.Error(w, "not found", http.StatusNotFound)
+		httpError(w, http.StatusNotFound)
 		return
 	}
 
 	// test album
 	rx, err = regexp.Compile("^/([^/?]+)/([^/?]+)/?(\\?.*)?$")
 	if err != nil {
-		http.Error(w, "internal server error", http.StatusInternalServerError)
+		httpErrorReason(w, http.StatusInternalServerError, err.Error())
 		return
 	}
 
@@ -202,12 +212,12 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 		captures := rx.FindStringSubmatch(req.RequestURI)
 		artist, err := url.QueryUnescape(captures[1])
 		if err != nil {
-			http.Error(w, "bad request", http.StatusBadRequest)
+			httpError(w, http.StatusBadRequest)
 			return
 		}
 		albumName, err := url.QueryUnescape(captures[2])
 		if err != nil {
-			http.Error(w, "bad request", http.StatusBadRequest)
+			httpError(w, http.StatusBadRequest)
 			return
 		}
 
@@ -220,12 +230,12 @@ func handleArtistAlbumPage(w http.ResponseWriter, req *http.Request) {
 		}
 
 		// artist or album not found
-		http.Error(w, "not found", http.StatusNotFound)
+		httpError(w, http.StatusNotFound)
 		return
 	}
 
 	// illegal URI format
-	http.Error(w, "not found", http.StatusNotFound)
+	httpError(w, http.StatusNotFound)
 }
 
 func RunOn(address string) {