auth: security audit fixes, rate limits on every route

Two separate reviews of the SSO branch and all 207 API routes (spec 12 §8.6). Every route was
guarded as meant. Fixed, each with a test:
- login: a directory 503 counts as a failed sign-in; a locked directory account is a refused
  password, not "unavailable"
- open redirect after OpenID sign-in (a tab in next)
- directory email matching only for non-admins without their own password; others connect on
  My settings (POST /api/me/identities/ldap); only admins disconnect a directory account
- OpenID session check reads the refreshed ID token's claims too
- connect is POST /api/auth/oidc/connect (CSRF header)
- stored bind password, client secret and SMTP password tied to their server
- 409 role_managed when a provider sets the role; empty Contrack PATCH is a 400
- @fastify/rate-limit on every route (RATE_LIMIT_PER_MINUTE), 10/min on Test buttons; a
  password asked again shares the login limiter
Live tests pass against lldap 0.6.3, Samba 4 AD and Keycloak 26.8.1.

apps/api/test/rate-limit.test.ts

@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// 08 §2.4: every route is rate limited per client IP, Test buttons more, and a signed-in
+// person's password asked again counts like a sign-in.
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { resetLoginLimiter } from '../src/auth/login-limiter.ts';
+import { hasTestDb } from './db.ts';
+import { ADMIN, H, createTestApp } from './app.ts';
+
+describe.skipIf(!hasTestDb)('rate limits (08 §2.4)', () => {
+  let t: Awaited<ReturnType<typeof createTestApp>>;
+  let admin: string;
+  beforeAll(async () => {
+    t = await createTestApp(undefined, { RATE_LIMIT_PER_MINUTE: '30' });
+    await t.clearMustChange(ADMIN.email);
+    admin = await t.login(ADMIN.email, ADMIN.password);
+  });
+  afterAll(() => t?.close());
+
+  it('Test buttons: 10 a minute', async () => {
+    const codes: number[] = [];
+    for (let i = 0; i < 11; i++)
+      codes.push(
+        (
+          await t.app.inject({
+            method: 'POST',
+            url: '/api/settings/smtp/test',
+            headers: { ...H, cookie: admin },
+            payload: {},
+          })
+        ).statusCode,
+      );
+    expect(codes.slice(0, 10)).not.toContain(429);
+    expect(codes[10]).toBe(429);
+  });
+
+  it('a password asked again counts like a sign-in: guessing it is stopped', async () => {
+    resetLoginLimiter();
+    const codes: number[] = [];
+    for (let i = 0; i < 6; i++)
+      codes.push(
+        (
+          await t.app.inject({
+            method: 'POST',
+            url: '/api/auth/change-password',
+            headers: { ...H, cookie: admin },
+            payload: { currentPassword: `guess-${i}-wrong`, newPassword: 'another-password-1' },
+          })
+        ).statusCode,
+      );
+    expect(codes.slice(0, 5)).toEqual([400, 400, 400, 400, 400]);
+    expect(codes[5]).toBe(429);
+    resetLoginLimiter();
+  });
+
+  it('/prov keeps its own limits (07 §2), outside the global one', async () => {
+    const prov = await t.app.inject({ url: '/prov/001565000000.cfg' });
+    expect(prov.headers['x-ratelimit-limit']).toBeUndefined();
+    const api = await t.app.inject({ url: '/api/auth/methods' });
+    expect(api.headers['x-ratelimit-limit']).toBe('30');
+  });
+
+  it('every other route: the global limit per IP, as a 429 rate_limited', async () => {
+    let r;
+    for (let i = 0; i < 40; i++) {
+      r = await t.app.inject({ url: '/api/auth/methods' });
+      if (r.statusCode === 429) break;
+    }
+    expect(r!.statusCode).toBe(429);
+    expect(r!.json().error.code).toBe('rate_limited');
+  });
+});