use regex + static method to centralize hashedfavicon URL behavior

lib/server.js

@@ -1,4 +1,5 @@
 const http = require('http')
+const format = require('util').format
 
 const WebSocket = require('ws')
 const finalHttpHandler = require('finalhandler')
@@ -6,14 +7,18 @@ const serveStatic = require('serve-static')
 
 const logger = require('./logger')
 
-const HASHED_FAVICON_URL = '/hashedfavicon_'
-const HASHED_FAVICON_EXTENSION = '.png'
+const HASHED_FAVICON_URL_REGEX = /hashedfavicon_([a-z0-9]{32}).png/g
 
 function getRemoteAddr (req) {
   return req.headers['cf-connecting-ip'] || req.headers['x-forwarded-for'] || req.connection.remoteAddress
 }
 
 class Server {
+  static getHashedFaviconUrl (hash) {
+    // Format must be compatible with HASHED_FAVICON_URL_REGEX
+    return format('/hashedfavicon_%s.png', hash)
+  }
+
   constructor (app) {
     this._app = app
 
@@ -28,24 +33,26 @@ class Server {
     this._http = http.createServer((req, res) => {
       logger.log('info', '%s requested: %s', getRemoteAddr(req), req.url)
 
-      if (req.url.startsWith(HASHED_FAVICON_URL) && req.url.endsWith(HASHED_FAVICON_EXTENSION)) {
-        this.handleFaviconRequest(req, res)
-      } else {
+      // Test the URL against a regex for hashed favicon URLs
+      // Require only 1 match ([0]) and test its first captured group ([1])
+      // Any invalid value or hit miss will pass into static handlers below
+      const faviconHash = [...req.url.matchAll(HASHED_FAVICON_URL_REGEX)]
+
+      if (faviconHash.length === 1 && this.handleFaviconRequest(res, faviconHash[0][1])) {
+        return
+      }
+
       // Attempt to handle req using distServeStatic, otherwise fail over to faviconServeStatic
       // If faviconServeStatic fails, pass to finalHttpHandler to terminate
       distServeStatic(req, res, () => {
         faviconsServeStatic(req, res, finalHttpHandler(req, res))
       })
-      }
     })
   }
 
-  handleFaviconRequest = (req, res) => {
-    let hash = req.url.substring(HASHED_FAVICON_URL.length)
-    hash = hash.substring(0, hash.length - HASHED_FAVICON_EXTENSION.length)
-
+  handleFaviconRequest = (res, faviconHash) => {
     for (const serverRegistration of this._app.serverRegistrations) {
-      if (serverRegistration.faviconHash && serverRegistration.faviconHash === hash) {
+      if (serverRegistration.faviconHash && serverRegistration.faviconHash === faviconHash) {
         const buf = Buffer.from(serverRegistration.lastFavicon.split(',')[1], 'base64')
 
         res.writeHead(200, {
@@ -54,13 +61,11 @@ class Server {
           'Cache-Control': 'max-age=604800' // Cache hashed favicon for 7 days
         }).end(buf)
 
-        return
+        return true
       }
     }
 
-    // Terminate request, no match
-    res.writeHead(404)
-    res.end()
+    return false
   }
 
   createWebSocketServer () {

lib/servers.js

@@ -1,13 +1,11 @@
 const crypto = require('crypto')
 
 const TimeTracker = require('./time')
+const Server = require('./server')
 
 const config = require('../config')
 const minecraftVersions = require('../minecraft_versions')
 
-const HASHED_FAVICON_URL = '/hashedfavicon_'
-const HASHED_FAVICON_EXTENSION = '.png'
-
 class ServerRegistration {
   serverId
   lastFavicon
@@ -233,16 +231,18 @@ class ServerRegistration {
       if (!this._faviconHasher) {
         this._faviconHasher = crypto.createHash('md5')
       }
+
       this.faviconHash = this._faviconHasher.update(favicon).digest('hex').toString()
 
       return true
     }
+
     return false
   }
 
   getFaviconUrl () {
     if (this.faviconHash) {
-      return HASHED_FAVICON_URL + this.faviconHash + HASHED_FAVICON_EXTENSION
+      return Server.getHashedFaviconUrl(this.faviconHash)
     } else if (this.data.favicon) {
       return this.data.favicon
     }