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

src/data/sessions.test.ts

@@ -2,7 +2,7 @@ import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
 import { createHash } from "node:crypto";
 import { createDatabase, type BotDatabase } from "./database.js";
 import { createUserStore, type UserStore } from "./users.js";
-import { createSessionStore, type SessionStore, SESSION_TTL_MS, SESSION_TOUCH_INTERVAL_MS } from "./sessions.js";
+import { createSessionStore, type SessionStore, SESSION_TTL_MS, SESSION_TOUCH_INTERVAL_MS, MAX_SESSIONS_PER_USER } from "./sessions.js";
 
 function sha256(token: string) {
   return createHash("sha256").update(token).digest("hex");
@@ -101,4 +101,19 @@ describe("SessionStore", () => {
     const remaining = (botDb.db.prepare("SELECT COUNT(*) AS n FROM sessions").get() as { n: number }).n;
     expect(remaining).toBe(1);
   });
+
+  it("createSession caps concurrent sessions per user at MAX_SESSIONS_PER_USER, evicting oldest", async () => {
+    // Create MAX + 2 sessions for the same user.
+    const tokens: string[] = [];
+    for (let i = 0; i < MAX_SESSIONS_PER_USER + 2; i++) {
+      tokens.push(sessions.createSession(userId).token);
+      await new Promise((r) => setTimeout(r, 2)); // stagger createdAt
+    }
+    const count = (botDb.db.prepare("SELECT COUNT(*) AS n FROM sessions").get() as { n: number }).n;
+    expect(count).toBe(MAX_SESSIONS_PER_USER);
+    // The first two should have been evicted, the last MAX remain
+    expect(sessions.validateAndTouch(tokens[0])).toBeNull();
+    expect(sessions.validateAndTouch(tokens[1])).toBeNull();
+    expect(sessions.validateAndTouch(tokens[tokens.length - 1])).not.toBeNull();
+  });
 });

src/data/sessions.ts

@@ -3,6 +3,7 @@ import type Database from "better-sqlite3";
 
 export const SESSION_TTL_MS = 7 * 24 * 60 * 60 * 1000; // 7 days
 export const SESSION_TOUCH_INTERVAL_MS = 60 * 60 * 1000; // 1 hour
+export const MAX_SESSIONS_PER_USER = 10;
 
 export interface SessionValidation {
   userId: string;
@@ -40,9 +41,18 @@ export function createSessionStore(db: Database.Database): SessionStore {
     "DELETE FROM sessions WHERE userId = ? AND id != ?"
   );
   const cleanupStmt = db.prepare("DELETE FROM sessions WHERE expiresAt < ?");
+  const countForUserStmt = db.prepare("SELECT COUNT(*) AS n FROM sessions WHERE userId = ?");
+  const deleteOldestForUserStmt = db.prepare(
+    "DELETE FROM sessions WHERE id IN (SELECT id FROM sessions WHERE userId = ? ORDER BY createdAt ASC LIMIT ?)"
+  );
 
   return {
     createSession(userId) {
+      // Cap concurrent sessions per user — oldest gets evicted on overflow.
+      const existing = (countForUserStmt.get(userId) as { n: number }).n;
+      if (existing >= MAX_SESSIONS_PER_USER) {
+        deleteOldestForUserStmt.run(userId, existing - MAX_SESSIONS_PER_USER + 1);
+      }
       const token = randomBytes(32).toString("base64url");
       const id = hashToken(token);
       const now = Date.now();

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

@@ -0,0 +1,63 @@
+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();
+  };
+}

src/web/server.ts

@@ -24,6 +24,7 @@ import { createSessionStore } from "../data/sessions.js";
 import { createRequireAuth } from "./middleware/requireAuth.js";
 import { requireAdmin } from "./middleware/requireAdmin.js";
 import { csrfOriginCheck } from "./middleware/csrf.js";
+import { createRateLimit } from "./middleware/rateLimit.js";
 import { validateSessionFromHeaders } from "./auth/validateSession.js";
 
 const SESSION_CLEANUP_INTERVAL_MS = 60 * 60 * 1000; // 1 hour
@@ -74,6 +75,14 @@ export function createWebServer(options: WebServerOptions): WebServer {
     res.json({ publicUrl: raw ? raw.replace(/\/+$/, "") : null });
   });
 
+  // Anti-DoS: throttle expensive (bcrypt) auth endpoints.
+  // 5 req per minute per IP for /login (capacity 5, refill 5/60 = ~0.083/sec).
+  // 3 req per minute per IP for /setup (more limited; first-run is rare).
+  const loginLimit = createRateLimit({ capacity: 5, refillPerSec: 5 / 60 });
+  const setupLimit = createRateLimit({ capacity: 3, refillPerSec: 3 / 60 });
+  app.use("/api/session/login", loginLimit);
+  app.use("/api/session/setup", setupLimit);
+
   app.use("/api/session", createSessionRouter(users, sessions, audit, logger));
 
   // ─── Gates for everything else under /api ───────────────────────────────

web/src/composables/useSession.ts

@@ -10,6 +10,26 @@ const currentUser = ref<User | null>(null);
 const needsSetup = ref<boolean | null>(null); // null = unknown / not fetched yet
 const ready = ref(false);
 
+let pollTimer: ReturnType<typeof setInterval> | null = null;
+const POLL_INTERVAL_MS = 60_000;
+
+function ensurePollStarted() {
+  if (pollTimer !== null) return;
+  pollTimer = setInterval(() => {
+    if (currentUser.value !== null) {
+      // Best-effort refresh; ignore errors (network blips etc.)
+      refreshMe().catch(() => {});
+    }
+  }, POLL_INTERVAL_MS);
+}
+
+function stopPoll() {
+  if (pollTimer !== null) {
+    clearInterval(pollTimer);
+    pollTimer = null;
+  }
+}
+
 async function refreshNeedsSetup(): Promise<void> {
   const res = await fetch("/api/session/needs-setup", { credentials: "same-origin" });
   if (res.ok) {
@@ -35,6 +55,7 @@ async function refresh(): Promise<void> {
     await refreshMe();
   }
   ready.value = true;
+  ensurePollStarted();
 }
 
 async function login(username: string, password: string): Promise<void> {
@@ -67,6 +88,7 @@ async function setup(username: string, password: string): Promise<void> {
 }
 
 async function logout(): Promise<void> {
+  stopPoll();
   await fetch("/api/session/logout", { method: "POST", credentials: "same-origin" });
   currentUser.value = null;
 }