core: use cache for Monero live refresh confirmation

core/src/apps/monero/__init__.py

@@ -4,7 +4,6 @@ from trezor.messages import MessageType
 from apps.common import HARDENED
 
 CURVE = "ed25519"
-_LIVE_REFRESH_TOKEN = None  # live-refresh permission token
 
 
 def boot() -> None:
@@ -20,11 +19,3 @@ def boot() -> None:
 
     if __debug__ and hasattr(MessageType, "DebugMoneroDiagRequest"):
         wire.add(MessageType.DebugMoneroDiagRequest, __name__, "diag")
-
-
-def live_refresh_token(token: bytes = None) -> None:
-    global _LIVE_REFRESH_TOKEN
-    if token is None:
-        return _LIVE_REFRESH_TOKEN
-    else:
-        _LIVE_REFRESH_TOKEN = token

core/src/apps/monero/live_refresh.py

@@ -10,7 +10,7 @@ from trezor.messages.MoneroLiveRefreshStepAck import MoneroLiveRefreshStepAck
 from trezor.messages.MoneroLiveRefreshStepRequest import MoneroLiveRefreshStepRequest
 
 from apps.common import paths
-from apps.monero import CURVE, live_refresh_token, misc
+from apps.monero import CURVE, misc
 from apps.monero.layout import confirms
 from apps.monero.xmr import crypto, key_image, monero
 from apps.monero.xmr.crypto import chacha_poly
@@ -49,10 +49,9 @@ async def _init_step(
         ctx, misc.validate_full_path, keychain, msg.address_n, CURVE
     )
 
-    fingerprint = storage.cache.get_session_id()[:4]
-    if live_refresh_token() != fingerprint:
+    if not storage.cache.get(storage.cache.APP_MONERO_LIVE_REFRESH):
         await confirms.require_confirm_live_refresh(ctx)
-        live_refresh_token(fingerprint)
+        storage.cache.set(storage.cache.APP_MONERO_LIVE_REFRESH, True)
 
     s.creds = misc.get_creds(keychain, msg.address_n, msg.network_type)
 

core/src/storage/cache.py

@@ -6,6 +6,7 @@ if False:
 APP_COMMON_SEED = 0
 APP_COMMON_SEED_WITHOUT_PASSPHRASE = 1
 APP_CARDANO_ROOT = 2
+APP_MONERO_LIVE_REFRESH = 3
 
 _cache_session_id = None  # type: Optional[bytes]
 _cache = {}
@@ -22,7 +23,6 @@ def get_session_id() -> bytes:
 
 
 def set(key: int, value: Any) -> None:
-    global _cache
     _cache[key] = value
 
 
@@ -32,6 +32,5 @@ def get(key: int) -> Any:
 
 def clear() -> None:
     global _cache_session_id
-    global _cache
     _cache_session_id = None
     _cache.clear()