chore: upgrade express-rate-limit 7.5.1 → 8.3.1 (IPv6 security fix)

- Fixes IPv6 rate limit bypass vulnerability (GHSA-46wh-pxpv-q5gq)
- IPv6 addresses now masked to /56 subnet by default
- Updated custom keyGenerators to use ipKeyGenerator() helper
- 5 new TDD tests for v8 features (ipKeyGenerator, IPv6 masking)
- 672 tests passing, 0 TS errors, 0 npm audit vulnerabilities

src/__tests__/rate-limit-v8.test.ts

@@ -0,0 +1,41 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+
+// Test express-rate-limit v8 upgrade compatibility
+describe("express-rate-limit v8 upgrade", () => {
+  it("should export rateLimit as default export", async () => {
+    const mod = await import("express-rate-limit");
+    expect(typeof mod.default).toBe("function");
+  });
+
+  it("should export ipKeyGenerator helper (v8 feature)", async () => {
+    const mod = await import("express-rate-limit");
+    // v8 exports ipKeyGenerator for IPv6 subnet masking
+    expect(typeof (mod as any).ipKeyGenerator).toBe("function");
+  });
+
+  it("ipKeyGenerator should return IPv4 addresses unchanged", async () => {
+    const { ipKeyGenerator } = await import("express-rate-limit") as any;
+    const result = ipKeyGenerator("192.168.1.1");
+    expect(result).toBe("192.168.1.1");
+  });
+
+  it("ipKeyGenerator should mask IPv6 addresses to /56 by default", async () => {
+    const { ipKeyGenerator } = await import("express-rate-limit") as any;
+    const ip1 = ipKeyGenerator("2001:db8:85a3:1234:1111:2222:3333:4444");
+    const ip2 = ipKeyGenerator("2001:db8:85a3:1256:aaaa:bbbb:cccc:dddd");
+    // Same /56 prefix → same result
+    expect(ip1).toBe(ip2);
+  });
+
+  it("rateLimit should accept standardHeaders: true", async () => {
+    const { default: rateLimit } = await import("express-rate-limit");
+    // Should not throw
+    const limiter = rateLimit({
+      windowMs: 60000,
+      max: 100,
+      standardHeaders: true,
+      legacyHeaders: false,
+    });
+    expect(typeof limiter).toBe("function");
+  });
+});

src/routes/billing.ts

@@ -1,5 +1,5 @@
 import { Router, Request, Response } from "express";
-import rateLimit from "express-rate-limit";
+import rateLimit, { ipKeyGenerator } from "express-rate-limit";
 import Stripe from "stripe";
 import { createProKey, downgradeByCustomer, updateEmailByCustomer, findKeyByCustomerId } from "../services/keys.js";
 import logger from "../services/logger.js";
@@ -76,7 +76,7 @@ async function isDocFastSubscription(subscriptionId: string): Promise<boolean> {
 const checkoutLimiter = rateLimit({
   windowMs: 60 * 60 * 1000, // 1 hour
   max: 3,
-  keyGenerator: (req: Request) => req.ip || req.socket.remoteAddress || "unknown",
+  keyGenerator: (req: Request) => ipKeyGenerator(req.ip || req.socket.remoteAddress || "unknown"),
   standardHeaders: true,
   legacyHeaders: false,
   message: { error: "Too many checkout requests. Please try again later." },

src/routes/demo.ts

@@ -1,5 +1,5 @@
 import { Router, Request, Response } from "express";
-import rateLimit from "express-rate-limit";
+import rateLimit, { ipKeyGenerator } from "express-rate-limit";
 import { renderPdf } from "../services/browser.js";
 import { markdownToHtml, wrapHtml } from "../services/markdown.js";
 import { handlePdfRoute, type SanitizedPdfOptions } from "../utils/pdf-handler.js";
@@ -56,7 +56,7 @@ const demoLimiter = rateLimit({
   message: { error: "Demo limit reached (5/hour). Get a Pro API key at https://docfast.dev for unlimited access." },
   standardHeaders: true,
   legacyHeaders: false,
-  keyGenerator: (req) => req.ip || req.socket.remoteAddress || "unknown",
+  keyGenerator: (req) => ipKeyGenerator(req.ip || req.socket.remoteAddress || "unknown"),
 });
 
 router.use(demoLimiter);

src/routes/email-change.ts

@@ -1,5 +1,5 @@
 import { Router, Request, Response } from "express";
-import rateLimit from "express-rate-limit";
+import rateLimit, { ipKeyGenerator } from "express-rate-limit";
 import { createPendingVerification, verifyCode } from "../services/verification.js";
 import { sendVerificationEmail } from "../services/email.js";
 import { queryWithRetry } from "../services/db.js";
@@ -13,7 +13,7 @@ const emailChangeLimiter = rateLimit({
   message: { error: "Too many email change attempts. Please try again in 1 hour." },
   standardHeaders: true,
   legacyHeaders: false,
-  keyGenerator: (req: Request) => req.body?.apiKey || req.ip || "unknown",
+  keyGenerator: (req: Request) => req.body?.apiKey || ipKeyGenerator(req.ip || "unknown"),
 });
 
 const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;