S-15c · Enforce MFA on the medewerker (Keycloak) realm (#158)

Closes #132.

Staff logins (behandel + beheer portals) now need a second factor; the citizen realms are unchanged.

**How:** every seeded medewerker carries a TOTP credential, which activates Keycloak's stock *conditional OTP* step in both the browser flow and the direct grant — no custom browser-flow JSON in the export. `CONFIGURE_TOTP` is a default required action so a medewerker added later must enrol first. ADR-0031 records the choice and, explicitly, that the shared fixture secret is a demo posture only.

**Tests (red first, 30c5279):**
- `check_realms.py` asserts the medewerker password-only grant is **refused**, then that password + TOTP succeeds and still carries the `behandelaar` role. It failed with `[MFA NOT ENFORCED]` against the old export.
- The three medewerker e2e logins move to `loginMedewerker()` (`tests/e2e/medewerker-login.ts`), which submits Keycloak's OTP prompt. Both TOTP implementations (Python `hmac`, Node `crypto`) are ~6 lines of RFC 6238 — no new dependency.

Verified locally against Keycloak 26.1: password-only → `invalid_grant`, password + code → 200, and the browser flow's `#otp` prompt accepts a computed code and issues an auth code.

## Definition of Done
- [x] Failing test/verify committed first; implementation makes it pass.
- [x] Conventional Commits referencing the issue (`refs #132`).
- [ ] CI green (verify-stack compose smoke + relevant checks).
- [x] `docker compose up` reaches green health within 3 minutes (Keycloak change is import-time only).
- [x] Docs touched (runbook, synthetic-data, demo-script) + ADR-0031 + demo note.
- [x] Closed by the merging PR (`closes #132`).

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #158

tests/e2e/catalogus.spec.ts

@@ -1,4 +1,5 @@
 import { expect, test } from '@playwright/test';
+import { loginMedewerker } from './medewerker-login';
 
 // S-15a walking skeleton: a beheerder logs in to the beheer portal (medewerker realm) and sees the
 // read-only ZTC catalogus. The verify stack seeds and publishes the BIG-REGISTRATIE zaaktype (the
@@ -7,10 +8,9 @@ import { expect, test } from '@playwright/test';
 test('a beheerder sees the published zaaktypen in the catalogus', async ({ page }) => {
   await page.goto('http://beheer/');
 
-  // The beheer portal redirects to the Keycloak medewerker realm login (same realm as behandel).
-  await page.locator('#username').fill('bram-beheerder');
-  await page.locator('#password').fill('test123');
-  await page.locator('#kc-login').click();
+  // The beheer portal redirects to the Keycloak medewerker realm login (same realm as behandel),
+  // which enforces MFA: password, then a TOTP code.
+  await loginMedewerker(page, 'bram-beheerder');
 
   await expect(page.getByRole('heading', { name: /Catalogus/i })).toBeVisible();
 

tests/e2e/default-fill.spec.ts

@@ -1,4 +1,5 @@
 import { expect, test } from '@playwright/test';
+import { loginMedewerker } from './medewerker-login';
 
 // S-15b: a beheerder edits the ACL default-fill in the beheer portal and gets a saved confirmation.
 // Runs against the shared verify stack; it edits + saves (the ACL store is in-memory, ADR-0026) and
@@ -6,10 +7,8 @@ import { expect, test } from '@playwright/test';
 test('a beheerder edits and saves the default-fill', async ({ page }) => {
   await page.goto('http://beheer/');
 
-  // Keycloak medewerker-realm login (same realm as behandel).
-  await page.locator('#username').fill('bram-beheerder');
-  await page.locator('#password').fill('test123');
-  await page.locator('#kc-login').click();
+  // Keycloak medewerker-realm login (same realm as behandel) — password + enforced TOTP.
+  await loginMedewerker(page, 'bram-beheerder');
 
   await expect(page.getByRole('heading', { name: /Catalogus/i })).toBeVisible();
 

tests/e2e/medewerker-login.spec.ts

@@ -0,0 +1,14 @@
+import { expect, test } from '@playwright/test';
+import { OTP_PERIOD_MS, nextUnusedCounter } from './medewerker-login';
+
+// Pure check of the TOTP counter guard in loginMedewerker — no browser, no stack. Keycloak refuses
+// a code it has already accepted (its otpPolicyCodeReusable defaults to false), so two logins as
+// the same medewerker inside one 30-second window must not spend the same counter twice (#132).
+test('a login never spends a TOTP counter this medewerker already used', () => {
+  const now = 3 * OTP_PERIOD_MS + 1_000; // 1 second into counter 3
+
+  expect(nextUnusedCounter(now, -1)).toBe(3); // nothing spent yet → the current counter
+  expect(nextUnusedCounter(now, 3)).toBe(4); // the current counter is spent → the next one
+  expect(nextUnusedCounter(now, 4)).toBe(5); // two logins already in this window → the one after
+  expect(nextUnusedCounter(now + OTP_PERIOD_MS, 3)).toBe(4); // window moved on → current again
+});

tests/e2e/medewerker-login.ts

@@ -0,0 +1,57 @@
+import { createHmac } from 'node:crypto';
+import { readFileSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import type { Page } from '@playwright/test';
+
+// The medewerker realm enforces MFA (S-15c), so a staff login is two steps: password, then a TOTP
+// code. The realm export seeds every medewerker with this fixture secret — Keycloak HMACs the raw
+// secret bytes — so the e2e can compute a valid code instead of enrolling an authenticator.
+const OTP_SECRET = 'BIGMEDEWERKEROTPSEED';
+
+export const OTP_PERIOD_MS = 30_000;
+
+// RFC 6238 TOTP: HMAC-SHA1 over the 30-second counter, dynamically truncated to 6 digits.
+export function totp(secret = OTP_SECRET, at = Date.now()): string {
+  const counter = Buffer.alloc(8);
+  counter.writeBigUInt64BE(BigInt(Math.floor(at / OTP_PERIOD_MS)));
+  const mac = createHmac('sha1', secret).update(counter).digest();
+  const offset = mac[mac.length - 1] & 0x0f;
+  return String((mac.readUInt32BE(offset) & 0x7fffffff) % 1_000_000).padStart(6, '0');
+}
+
+// Keycloak refuses a TOTP code it has already accepted (its otpPolicyCodeReusable defaults to
+// false), so two logins as the same medewerker inside one 30-second window would both submit the
+// same code and the second is rejected. Spend the first counter this medewerker has left.
+export function nextUnusedCounter(now: number, spent: number): number {
+  return Math.max(Math.floor(now / OTP_PERIOD_MS), spent + 1);
+}
+
+// The spent counter lives on disk rather than in module state: Playwright starts a fresh worker
+// process for a retry, which would otherwise forget it and resubmit the rejected code.
+function spendCounter(username: string): number {
+  const file = join(tmpdir(), `otp-counter-${username}`);
+  let spent = -1;
+  try {
+    spent = Number(readFileSync(file, 'utf8')) || -1;
+  } catch {
+    // first login as this medewerker in this run
+  }
+  const counter = nextUnusedCounter(Date.now(), spent);
+  writeFileSync(file, String(counter));
+  return counter;
+}
+
+export async function loginMedewerker(page: Page, username: string): Promise<void> {
+  await page.locator('#username').fill(username);
+  await page.locator('#password').fill('test123');
+  await page.locator('#kc-login').click();
+
+  // Keycloak's conditional-OTP step. Wait out the rest of the window if the counter we may spend is
+  // still in the future; its lookAheadWindow would accept the code a moment early, but only by one
+  // counter — waiting keeps a third login in the same window valid too.
+  const counter = spendCounter(username);
+  await page.waitForTimeout(Math.max(0, counter * OTP_PERIOD_MS - Date.now()));
+  await page.locator('#otp').fill(totp(OTP_SECRET, counter * OTP_PERIOD_MS));
+  await page.locator('#kc-login').click();
+}

tests/e2e/registration.spec.ts

@@ -1,4 +1,5 @@
 import { expect, request, test } from '@playwright/test';
+import { loginMedewerker } from './medewerker-login';
 
 // Walking-skeleton happy path (S-08d + S-09 + S-09b + S-12 + S-10a + S-19b-2): a zorgprofessional
 // logs in via mock DigiD and submits through the self-service portal → BFF → domain; the entry
@@ -76,9 +77,8 @@ test('DigiD submit → public INGEDIEND → documenten → behandelaar goedkeurt
   // — the S-12 flow that replaces the temporary admin endpoint. The staff tab switches to the
   // medewerker realm (a different Keycloak realm than the citizen's digid session).
   await staff.goto('http://behandel/');
-  await staff.locator('#username').fill('merel-behandelaar');
-  await staff.locator('#password').fill('test123');
-  await staff.locator('#kc-login').click();
+  // That realm enforces MFA (S-15c), so the behandelaar logs in with password + TOTP.
+  await loginMedewerker(staff, 'merel-behandelaar');
 
   await expect(staff.getByRole('heading', { name: /Werkbak/i })).toBeVisible();