Use a Set for the extension whitelist.

Author: rgrove

conf/index.js

@@ -30,45 +30,45 @@ module.exports = {
   //
   // Requests to the cdnDomain will bypass this whitelist and proxy all file
   // types. Please keep this list alphabetized.
-  extensionWhitelist: {
-    '.appcache'  : true,
-    '.coffee'    : true,
-    '.css'       : true,
-    '.csv'       : true,
-    '.eot'       : true,
-    '.geojson'   : true,
-    '.handlebars': true,
-    '.hbs'       : true,
-    '.htm'       : true,
-    '.html'      : true,
-    '.js'        : true,
-    '.json'      : true,
-    '.jsonld'    : true,
-    '.kml'       : true,
-    '.md'        : true,
-    '.n3'        : true,
-    '.nt'        : true,
-    '.otf'       : true,
-    '.owl'       : true,
-    '.pdf'       : true,
-    '.rdf'       : true,
-    '.rss'       : true,
-    '.svg'       : true,
-    '.swf'       : true,
-    '.ttc'       : true,
-    '.ttf'       : true,
-    '.ttl'       : true,
-    '.vtt'       : true,
-    '.woff'      : true,
-    '.woff2'     : true,
-    '.xht'       : true,
-    '.xhtml'     : true,
-    '.xml'       : true,
-    '.xsl'       : true,
-    '.xslt'      : true,
-    '.yaml'      : true,
-    '.yml'       : true
-  },
+  extensionWhitelist: new Set([
+    '.appcache',
+    '.coffee',
+    '.css',
+    '.csv',
+    '.eot',
+    '.geojson',
+    '.handlebars',
+    '.hbs',
+    '.htm',
+    '.html',
+    '.js',
+    '.json',
+    '.jsonld',
+    '.kml',
+    '.md',
+    '.n3',
+    '.nt',
+    '.otf',
+    '.owl',
+    '.pdf',
+    '.rdf',
+    '.rss',
+    '.svg',
+    '.swf',
+    '.ttc',
+    '.ttf',
+    '.ttl',
+    '.vtt',
+    '.woff',
+    '.woff2',
+    '.xht',
+    '.xhtml',
+    '.xml',
+    '.xsl',
+    '.xslt',
+    '.yaml',
+    '.yml',
+  ]),
 
   // Whether we're running in a production environment (true) or
   // development/test (false).

lib/middleware/file-redirect.js

@@ -3,19 +3,19 @@
 const config = require('../../conf');
 const path   = require('path');
 
+const { extensionWhitelist } = config;
+
 // Redirects requests for non-whitelisted file extensions directly to GitHub,
 // since there's no value in proxying them.
 module.exports = rootUrl => {
   return (req, res, next) => {
-    if (req.isCDN) {
+    if (req.isCDN || req.path.endsWith('/')) {
       return void next();
     }
 
-    if (config.extensionWhitelist[path.extname(req.path).toLowerCase()]) {
-      return void next();
-    }
+    let extension = path.extname(req.path).toLowerCase();
 
-    if (/\/$/.test(req.path)) {
+    if (extensionWhitelist.has(extension)) {
       return void next();
     }