fix(middleware): escape static directory listing links

middleware/static.go

@@ -80,6 +80,7 @@ type StaticConfig struct {
 	EnablePathUnescaping bool
 
 	// DirectoryListTemplate is template to list directory contents
+	// File entries expose Name, URL, Dir and Size; URL is the escaped relative link.
 	// Optional. Default to `directoryListHTMLTemplate` constant below.
 	DirectoryListTemplate string
 }
@@ -144,9 +145,9 @@ const directoryListHTMLTemplate = `
 		<li>
 		{{ if .Dir }}
 			{{ $name := print .Name "/" }}
-			<a class="dir" href="{{ $name }}">{{ $name }}</a>
+			<a class="dir" href="{{ .URL }}">{{ $name }}</a>
 			{{ else }}
-			<a class="file" href="{{ .Name }}">{{ .Name }}</a>
+			<a class="file" href="{{ .URL }}">{{ .Name }}</a>
 			<span>{{ .Size }}</span>
 		{{ end }}
 		</li>
@@ -371,11 +372,16 @@ func listDir(t *template.Template, pathInFs string, filesystem fs.FS, res http.R
 			size = info.Size()
 		}
 
+		link := &url.URL{Path: f.Name()}
+		if f.IsDir() {
+			link.Path += "/"
+		}
 		data.Files = append(data.Files, struct {
 			Name string
+			URL  string
 			Dir  bool
 			Size string
-		}{f.Name(), f.IsDir(), format(size)})
+		}{f.Name(), link.String(), f.IsDir(), format(size)})
 	}
 
 	return t.Execute(res, data)

middleware/static_test.go

@@ -4,6 +4,7 @@
 package middleware
 
 import (
+	"html"
 	"io/fs"
 	"net/http"
 	"net/http/httptest"
@@ -108,6 +109,54 @@ func TestStaticHTML5PreservesMatchedHandlerNotFound(t *testing.T) {
 	}
 }
 
+func TestStaticBrowseEscapesNames(t *testing.T) {
+	for _, tc := range []struct {
+		name string
+		dir  bool
+	}{
+		{name: "plain.txt"},
+		{name: "hash#file.txt"},
+		{name: "query?.txt"},
+		{name: "percent%.txt"},
+		{name: "with space.txt"},
+		{name: "colon:name.txt"},
+		{name: "amp&file.txt"},
+		{name: "hash#dir", dir: true},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			fileName := tc.name
+			if tc.dir {
+				fileName += "/index.html"
+			}
+			e := echo.New()
+			e.Use(StaticWithConfig(StaticConfig{
+				Filesystem: fstest.MapFS{fileName: {Data: []byte("file contents")}},
+				Browse:     true,
+			}))
+
+			req := httptest.NewRequest(http.MethodGet, "http://example.com/", nil)
+			rec := httptest.NewRecorder()
+			e.ServeHTTP(rec, req)
+			require.Equal(t, http.StatusOK, rec.Code)
+
+			_, rest, found := strings.Cut(rec.Body.String(), `href="`)
+			require.True(t, found)
+			href, _, found := strings.Cut(rest, `"`)
+			require.True(t, found)
+			target, err := req.URL.Parse(html.UnescapeString(href))
+			require.NoError(t, err)
+			// Browsers do not send URL fragments to the server.
+			target.Fragment = ""
+			target.RawFragment = ""
+
+			rec = httptest.NewRecorder()
+			e.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, target.String(), nil))
+			assert.Equal(t, http.StatusOK, rec.Code)
+			assert.Equal(t, "file contents", rec.Body.String())
+		})
+	}
+}
+
 func TestStatic(t *testing.T) {
 	var testCases = []struct {
 		name                 string