Gate both kiosks behind a device token, and make an unreachable setting a test failure

plugins/usb/api/routes.py

@@ -24,6 +24,8 @@ import logging
 import re
 from datetime import datetime, timedelta
 
+import hmac
+
 from flask import Blueprint, request, Response
 from flask_jwt_extended import jwt_required
 
@@ -741,6 +743,31 @@ def _kiosk_enabled():
     return _kiosk_setting('usb_kiosk_enabled', False)
 
 
+def _kiosk_open():
+    """True when the kiosk is on for this site AND the caller has its token.
+
+    The flag alone was the whole gate, and a flag is a decision, not a
+    credential: with the kiosk on, anyone who could reach the app could move a
+    device between checked-out and checked-in and have it recorded against a
+    badge they guessed. A badge is a short numeric SSO, so it is attribution,
+    never authorization - the same reasoning that closed the parts kiosk.
+
+    The token is per-DEVICE. A kiosk is a browser on a screen by the cabinet, so
+    a token served inside the page would be readable by anyone who could load
+    it. An admin opens the screen once as /usb-kiosk?token=..., the page keeps
+    it in that browser and sends it as X-Kiosk-Token.
+    """
+    if not _kiosk_enabled():
+        return False
+    expected = (Setting.get('usb_kiosk_token') or '').strip()
+    presented = (request.headers.get('X-Kiosk-Token') or '').strip()
+    if not expected or not presented:
+        return False
+    # compare_digest, not ==: == leaks the token's length and matching prefix
+    # through timing.
+    return hmac.compare_digest(presented, expected)
+
+
 def _kiosk_disabled_response():
     # 404, not 403: when the kiosk is off these routes should not read as
     # "there is a door here and you may not use it".
@@ -765,7 +792,7 @@ def kiosk_device(device_id):
     the person standing there cannot tell whether they are doing the right
     thing. No badge number, no history, no contact details.
     """
-    if not _kiosk_enabled():
+    if not _kiosk_open():
         return _kiosk_disabled_response()
     if _usb_selfhosted():
         return selfhosted.kiosk_device(device_id)
@@ -825,7 +852,7 @@ def kiosk_session():
     COUNT of everything else - names for those are a separate, deliberate step,
     so a passer-by does not read the whole cabinet's holders off a wall screen.
     """
-    if not _kiosk_enabled():
+    if not _kiosk_open():
         return _kiosk_disabled_response()
     data = request.get_json() or {}
     if _usb_selfhosted():
@@ -881,7 +908,7 @@ def kiosk_others():
     who is on leave - but the names that makes visible should not be the first
     thing on a shopfloor screen.
     """
-    if not _kiosk_enabled():
+    if not _kiosk_open():
         return _kiosk_disabled_response()
     if not _kiosk_setting('usb_kiosk_allow_return_for_others', True):
         return _kiosk_disabled_response()
@@ -925,7 +952,7 @@ def kiosk_others():
 @usb_bp.route('/kiosk/checkout', methods=['POST'])
 def kiosk_checkout():
     """Check a device out at the kiosk. Body: {device_id, badge}."""
-    if not _kiosk_enabled():
+    if not _kiosk_open():
         return _kiosk_disabled_response()
     data = request.get_json() or {}
     if _usb_selfhosted():
@@ -998,7 +1025,7 @@ def kiosk_checkin():
     handed the device back, which is the honest record and needs no change to a
     schema this app does not own.
     """
-    if not _kiosk_enabled():
+    if not _kiosk_open():
         return _kiosk_disabled_response()
     data = request.get_json() or {}
     if _usb_selfhosted():