feat(auth): rate-limit /login+/setup, per-user session cap, periodic /me poll

src/web/middleware/rateLimit.test.ts

@@ -0,0 +1,41 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import express from "express";
+import request from "supertest";
+import { createRateLimit } from "./rateLimit.js";
+
+describe("createRateLimit", () => {
+  let app: express.Express;
+
+  beforeEach(() => {
+    app = express();
+    // capacity=3, refill=1/sec → first 3 succeed, then 429 until refill.
+    app.use(createRateLimit({ capacity: 3, refillPerSec: 1 }));
+    app.get("/", (_req, res) => res.json({ ok: true }));
+  });
+
+  it("allows up to capacity bursts then rejects with 429", async () => {
+    expect((await request(app).get("/")).status).toBe(200);
+    expect((await request(app).get("/")).status).toBe(200);
+    expect((await request(app).get("/")).status).toBe(200);
+    const denied = await request(app).get("/");
+    expect(denied.status).toBe(429);
+    expect(denied.body).toEqual({ error: "rate limit exceeded" });
+    expect(denied.headers["retry-after"]).toBeDefined();
+  });
+
+  it("uses per-key buckets when keyFn is provided", async () => {
+    const customApp = express();
+    customApp.use(
+      createRateLimit({
+        capacity: 1,
+        refillPerSec: 0.001,
+        keyFn: (req) => req.get("x-user") ?? "anon",
+      })
+    );
+    customApp.get("/", (_req, res) => res.json({ ok: true }));
+    expect((await request(customApp).get("/").set("X-User", "alice")).status).toBe(200);
+    expect((await request(customApp).get("/").set("X-User", "alice")).status).toBe(429);
+    // Different user, separate bucket → still has a token.
+    expect((await request(customApp).get("/").set("X-User", "bob")).status).toBe(200);
+  });
+});

src/web/middleware/rateLimit.ts

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+import type { Request, Response, NextFunction, RequestHandler } from "express";
+
+interface Bucket {
+  tokens: number;
+  lastRefillMs: number;
+}
+
+interface RateLimitOptions {
+  /** Bucket capacity (max burst). */
+  capacity: number;
+  /** Tokens refilled per second. */
+  refillPerSec: number;
+  /** Optional key function; defaults to req.ip. */
+  keyFn?: (req: Request) => string;
+}
+
+/**
+ * In-memory token-bucket rate limiter.
+ *
+ * Each unique key (default: req.ip) gets its own bucket. Refills continuously
+ * at `refillPerSec` up to `capacity`. Each request consumes 1 token; if no
+ * token is available, returns 429 with Retry-After.
+ *
+ * Buckets evict themselves after 10 minutes of inactivity to bound memory.
+ */
+export function createRateLimit(options: RateLimitOptions): RequestHandler {
+  const buckets = new Map<string, Bucket>();
+  const EVICT_AFTER_MS = 10 * 60 * 1000;
+  // Periodic eviction to bound memory under attack.
+  const evict = setInterval(() => {
+    const cutoff = Date.now() - EVICT_AFTER_MS;
+    for (const [k, b] of buckets) {
+      if (b.lastRefillMs < cutoff) buckets.delete(k);
+    }
+  }, 60_000);
+  // Unref the timer so it doesn't keep the process alive in tests.
+  if (typeof (evict as { unref?: () => void }).unref === "function") {
+    (evict as { unref: () => void }).unref();
+  }
+
+  const keyFn = options.keyFn ?? ((req) => req.ip ?? "unknown");
+
+  return function rateLimit(req: Request, res: Response, next: NextFunction): void {
+    const key = keyFn(req);
+    const now = Date.now();
+    let b = buckets.get(key);
+    if (!b) {
+      b = { tokens: options.capacity, lastRefillMs: now };
+      buckets.set(key, b);
+    }
+    const elapsedSec = (now - b.lastRefillMs) / 1000;
+    b.tokens = Math.min(options.capacity, b.tokens + elapsedSec * options.refillPerSec);
+    b.lastRefillMs = now;
+    if (b.tokens < 1) {
+      const waitSec = Math.ceil((1 - b.tokens) / options.refillPerSec);
+      res.setHeader("Retry-After", String(waitSec));
+      res.status(429).json({ error: "rate limit exceeded" });
+      return;
+    }
+    b.tokens -= 1;
+    next();
+  };
+}