Have Worker rate limit ws messages (#3449)

## Description:

Prevent client from spamming ws messages before joining a game server.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/server/Worker.ts

@@ -3,6 +3,7 @@ import express, { NextFunction, Request, Response } from "express";
 import rateLimit from "express-rate-limit";
 import http from "http";
 import ipAnonymize from "ip-anonymize";
+import { RateLimiter } from "limiter";
 import path from "path";
 import { fileURLToPath } from "url";
 import { WebSocket, WebSocketServer } from "ws";
@@ -289,6 +290,11 @@ export async function startWorker() {
         : // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
           forwarded || req.socket.remoteAddress || "unknown";
 
+      if (!getWsIpLimiter(ip).tryRemoveTokens(1)) {
+        ws.close(1008, "Rate limit exceeded");
+        return;
+      }
+
       try {
         // Parse and handle client messages
         const parsed = ClientMessageSchema.safeParse(
@@ -609,3 +615,21 @@ function generateGameIdForWorker(): GameID | null {
   log.warn(`Failed to generate game ID for worker ${workerId}`);
   return null;
 }
+
+// Per-IP rate limiter for pre-join WebSocket messages.
+// Prevents unauthenticated connections from spamming messages
+// (e.g. pings) before joining a game.
+const wsIpLimiters = new Map<string, RateLimiter>();
+function getWsIpLimiter(ip: string): RateLimiter {
+  let limiter = wsIpLimiters.get(ip);
+  if (!limiter) {
+    limiter = new RateLimiter({
+      tokensPerInterval: 5,
+      interval: "second",
+    });
+    wsIpLimiters.set(ip, limiter);
+  }
+  return limiter;
+}
+// Clean up stale IP limiters every 10 minutes
+setInterval(() => wsIpLimiters.clear(), 10 * 60 * 1000);