apps/homescreen: handle Initialize.skip_passphrase

TODO: tests

src/apps/common/cache.py

@@ -1,46 +1,57 @@
 from trezor.crypto import hashlib, hmac, random
 from apps.common import storage
 
-memory = {}
-_seed = None
-_passphrase = None
+_cached_seed = None
+_cached_passphrase = None
 
 
-def get_state(state: bytes=None, passphrase: str=None):
-
-    if state is None:
+def get_state(prev_state: bytes = None, passphrase: str = None) -> bytes:
+    if prev_state is None:
         salt = random.bytes(32)  # generate a random salt if no state provided
     else:
-        salt = state[:32]        # use salt from provided state
-
+        salt = prev_state[:32]  # use salt from provided state
+        if len(salt) != 32:
+            return None  # invalid state
     if passphrase is None:
-        global _passphrase
-        if _passphrase is None:
-            return None
-        passphrase = _passphrase    # use cached passphrase
+        if _cached_passphrase is None:
+            return None  # we don't have any passphrase to compute the state
+        else:
+            passphrase = _cached_passphrase  # use cached passphrase
+    return _compute_state(salt, passphrase)
 
+
+def _compute_state(salt: bytes, passphrase: str) -> bytes:
     # state = HMAC(passphrase, salt || device_id)
-    msg = salt + storage.get_device_id().encode()
-    state = hmac.new(passphrase.encode(), msg, hashlib.sha256).digest()
-
+    message = salt + storage.get_device_id().encode()
+    state = hmac.new(passphrase.encode(), message, hashlib.sha256).digest()
     return salt + state
 
 
 def get_seed():
-    global _seed
-    return _seed
+    return _cached_seed
 
 
-def set_seed(seed, passphrase):
-    global _seed, _passphrase
-    _seed, _passphrase = seed, passphrase
+def get_passphrase():
+    return _cached_passphrase
 
 
 def has_passphrase():
-    global _passphrase
-    return _passphrase is not None
+    return _cached_passphrase is not None
 
 
-def clear():
-    global _seed, _passphrase
-    _seed, _passphrase = None, None
+def set_seed(seed):
+    global _cached_seed
+    _cached_seed = seed
+
+
+def set_passphrase(passphrase):
+    global _cached_passphrase
+    _cached_passphrase = passphrase
+
+
+def clear(skip_passphrase: bool = False):
+    set_seed(None)
+    if skip_passphrase:
+        set_passphrase('')
+    else:
+        set_passphrase(None)

src/apps/common/seed.py

@@ -6,27 +6,29 @@ from apps.common.request_passphrase import protect_by_passphrase
 _DEFAULT_CURVE = 'secp256k1'
 
 
-async def derive_node(ctx: wire.Context, path=(), curve_name=_DEFAULT_CURVE):
-    seed = await _get_seed(ctx)
+async def derive_node(ctx: wire.Context, path: list, curve_name=_DEFAULT_CURVE):
+    seed = await _get_cached_seed(ctx)
     node = bip32.from_seed(seed, curve_name)
     if path:
         node.derive_path(path)
     return node
 
 
-async def _get_seed(ctx: wire.Context) -> bytes:
+async def _get_cached_seed(ctx: wire.Context) -> bytes:
+    if not storage.is_initialized():
+        raise wire.ProcessError('Device is not initialized')
     if cache.get_seed() is None:
-        seed, passphrase = await _compute_seed(ctx)
-        cache.set_seed(seed, passphrase)
+        passphrase = await _get_cached_passphrase(ctx)
+        seed = bip39.seed(storage.get_mnemonic(), passphrase)
+        cache.set_seed(seed)
     return cache.get_seed()
 
 
-async def _compute_seed(ctx: wire.Context) -> (bytes, str):
-    if not storage.is_initialized():
-        raise wire.ProcessError('Device is not initialized')
-
-    passphrase = await protect_by_passphrase(ctx)
-    return bip39.seed(storage.get_mnemonic(), passphrase), passphrase
+async def _get_cached_passphrase(ctx: wire.Context) -> str:
+    if cache.get_passphrase() is None:
+        passphrase = await protect_by_passphrase(ctx)
+        cache.set_passphrase(passphrase)
+    return cache.get_passphrase()
 
 
 def derive_node_without_passphrase(path, curve_name=_DEFAULT_CURVE):

src/apps/homescreen/__init__.py

@@ -1,5 +1,4 @@
-from trezor import config
-from trezor.utils import symbol, model
+from trezor import config, utils
 from trezor.wire import register, protobuf_workflow
 from trezor.messages import wire_types
 from trezor.messages.Features import Features
@@ -9,58 +8,60 @@ from trezor.messages.Success import Success
 from apps.common import storage, cache
 
 
-async def respond_Features(ctx, msg):
-
-    if isinstance(msg, Initialize):
-        if msg.state is None or bytes(msg.state) != cache.get_state(state=bytes(msg.state)):
-            cache.clear()
-
+def get_features():
     f = Features()
     f.vendor = 'trezor.io'
-    f.major_version = symbol('VERSION_MAJOR')
-    f.minor_version = symbol('VERSION_MINOR')
-    f.patch_version = symbol('VERSION_PATCH')
-    f.device_id = storage.get_device_id()
-    f.pin_protection = config.has_pin()
-    f.passphrase_protection = storage.has_passphrase()
     f.language = 'english'
+    f.major_version = utils.symbol('VERSION_MAJOR')
+    f.minor_version = utils.symbol('VERSION_MINOR')
+    f.patch_version = utils.symbol('VERSION_PATCH')
+    f.revision = utils.symbol('GITREV')
+    f.model = utils.model()
+    if f.model == 'EMU':
+        f.model = 'T'  # emulator currently emulates model T
+    f.device_id = storage.get_device_id()
     f.label = storage.get_label()
     f.initialized = storage.is_initialized()
-    f.revision = symbol('GITREV')
+    f.pin_protection = config.has_pin()
     f.pin_cached = config.has_pin()
+    f.passphrase_protection = storage.has_passphrase()
     f.passphrase_cached = cache.has_passphrase()
     f.needs_backup = storage.needs_backup()
-    f.flags = storage.get_flags()
-    if model() in ['T', 'EMU']:  # emulator currently emulates model T
-        f.model = 'T'
     f.unfinished_backup = storage.unfinished_backup()
-
+    f.flags = storage.get_flags()
     return f
 
 
-async def respond_ClearSession(ctx, msg):
+async def handle_Initialize(ctx, msg):
+    if msg.state is None or msg.state != cache.get_state(bytes(msg.state)):
+        cache.clear(msg.skip_passphrase)
+    return get_features()
+
+
+async def handle_GetFeatures(ctx, msg):
+    return get_features()
+
+
+async def handle_ClearSession(ctx, msg):
     cache.clear()
     return Success(message='Session cleared')
 
 
-async def respond_Pong(ctx, msg):
-
+async def handle_Ping(ctx, msg):
     if msg.button_protection:
         from apps.common.confirm import require_confirm
         from trezor.messages.ButtonRequestType import ProtectCall
         from trezor.ui.text import Text
         from trezor import ui
         await require_confirm(ctx, Text('Confirm', ui.ICON_DEFAULT), ProtectCall)
-
     if msg.passphrase_protection:
         from apps.common.request_passphrase import protect_by_passphrase
         await protect_by_passphrase(ctx)
-
     return Success(message=msg.message)
 
 
 def boot():
-    register(wire_types.Initialize, protobuf_workflow, respond_Features)
-    register(wire_types.GetFeatures, protobuf_workflow, respond_Features)
-    register(wire_types.ClearSession, protobuf_workflow, respond_ClearSession)
-    register(wire_types.Ping, protobuf_workflow, respond_Pong)
+    register(wire_types.Initialize, protobuf_workflow, handle_Initialize)
+    register(wire_types.GetFeatures, protobuf_workflow, handle_GetFeatures)
+    register(wire_types.ClearSession, protobuf_workflow, handle_ClearSession)
+    register(wire_types.Ping, protobuf_workflow, handle_Ping)