common: introduce mnemonic module

To provide another layer between seed and mnemonic. First step to
introduce SLIP-39

src/apps/cardano/seed.py

@@ -2,7 +2,7 @@ from trezor import wire
 from trezor.crypto import bip32
 
 from apps.cardano import SEED_NAMESPACE
-from apps.common import cache, storage
+from apps.common import cache, mnemonic, storage
 from apps.common.request_passphrase import protect_by_passphrase
 
 
@@ -33,7 +33,7 @@ async def get_keychain(ctx: wire.Context) -> Keychain:
     if passphrase is None:
         passphrase = await protect_by_passphrase(ctx)
         cache.set_passphrase(passphrase)
-    root = bip32.from_mnemonic_cardano(storage.get_mnemonic(), passphrase)
+    root = bip32.from_mnemonic_cardano(mnemonic.restore(), passphrase)
 
     # derive the namespaced root node
     for i in SEED_NAMESPACE[0]:

src/apps/common/mnemonic.py

@@ -0,0 +1,46 @@
+from trezor import ui
+from trezor.crypto import bip39
+
+from apps.common import storage
+
+TYPE_BIP39 = 0
+
+
+def get() -> (bytes, int):
+    mnemonic_secret = storage.get_mnemonic_secret()
+    mnemonic_type = storage.get_mnemonic_type()
+    return mnemonic_secret, mnemonic_type
+
+
+def get_seed(passphrase: str = ""):
+    secret, mnemonic_type = get()
+    _start_progress()
+    if mnemonic_type == TYPE_BIP39:
+        return bip39.seed(secret.decode(), passphrase, _render_progress)
+
+
+def process(mnemonics: list, mnemonic_type: int):
+    if mnemonic_type == TYPE_BIP39:
+        return mnemonics[0].encode()
+    else:
+        raise RuntimeError("Unknown mnemonic type")
+
+
+def restore() -> str:
+    secret, mnemonic_type = get()
+    if mnemonic_type == TYPE_BIP39:
+        return secret.decode()
+
+
+def _start_progress():
+    ui.backlight_slide_sync(ui.BACKLIGHT_DIM)
+    ui.display.clear()
+    ui.header("Please wait")
+    ui.display.refresh()
+    ui.backlight_slide_sync(ui.BACKLIGHT_NORMAL)
+
+
+def _render_progress(progress: int, total: int):
+    p = int(1000 * progress / total)
+    ui.display.loader(p, 18, ui.WHITE, ui.BG)
+    ui.display.refresh()

src/apps/common/seed.py

@@ -1,7 +1,7 @@
 from trezor import ui, wire
-from trezor.crypto import bip32, bip39
+from trezor.crypto import bip32
 
-from apps.common import cache, storage
+from apps.common import cache, mnemonic, storage
 from apps.common.request_passphrase import protect_by_passphrase
 
 allow = list
@@ -66,32 +66,17 @@ async def _compute_seed(ctx: wire.Context) -> bytes:
     if passphrase is None:
         passphrase = await protect_by_passphrase(ctx)
         cache.set_passphrase(passphrase)
-    _start_bip39_progress()
-    seed = bip39.seed(storage.get_mnemonic(), passphrase, _render_bip39_progress)
+    seed = mnemonic.get_seed(passphrase)
     cache.set_seed(seed)
     return seed
 
 
-def _start_bip39_progress():
-    ui.backlight_slide_sync(ui.BACKLIGHT_DIM)
-    ui.display.clear()
-    ui.header("Please wait")
-    ui.display.refresh()
-    ui.backlight_slide_sync(ui.BACKLIGHT_NORMAL)
-
-
-def _render_bip39_progress(progress: int, total: int):
-    p = int(1000 * progress / total)
-    ui.display.loader(p, 18, ui.WHITE, ui.BG)
-    ui.display.refresh()
-
-
 def derive_node_without_passphrase(
     path: list, curve_name: str = "secp256k1"
 ) -> bip32.HDNode:
     if not storage.is_initialized():
         raise Exception("Device is not initialized")
-    seed = bip39.seed(storage.get_mnemonic(), "")
+    seed = mnemonic.get_seed()
     node = bip32.from_seed(seed, curve_name)
     node.derive_path(path)
     return node

src/apps/common/storage.py

@@ -18,7 +18,7 @@ _COUNTER_TAIL_LEN = 8
 _APP                = const(0x01)  # app namespace
 _DEVICE_ID          = const(0x00)  # bytes
 _VERSION            = const(0x01)  # int
-_MNEMONIC           = const(0x02)  # str
+_MNEMONIC_SECRET    = const(0x02)  # bytes
 _LANGUAGE           = const(0x03)  # str
 _LABEL              = const(0x04)  # str
 _USE_PASSPHRASE     = const(0x05)  # bool (0x01 or empty)
@@ -30,6 +30,7 @@ _PASSPHRASE_SOURCE  = const(0x0A)  # int
 _UNFINISHED_BACKUP  = const(0x0B)  # bool (0x01 or empty)
 _AUTOLOCK_DELAY_MS  = const(0x0C)  # int
 _NO_BACKUP          = const(0x0D)  # bool (0x01 or empty)
+_MNEMONIC_TYPE      = const(0x0E)  # int
 # fmt: on
 
 
@@ -44,6 +45,17 @@ def _get_bool(app: int, key: int, public: bool = False) -> bool:
     return config.get(app, key, public) == _TRUE_BYTE
 
 
+def _set_uint8(app: int, key: int, val: int):
+    config.set(app, key, val.to_bytes(1, "big"))
+
+
+def _get_uint8(app: int, key: int) -> int:
+    val = config.get(app, key)
+    if not val:
+        return None
+    return int.from_bytes(val, "big")
+
+
 def _new_device_id() -> str:
     return hexlify(random.bytes(12)).decode().upper()
 
@@ -67,11 +79,15 @@ def get_label() -> str:
     return label.decode()
 
 
-def get_mnemonic() -> str:
-    mnemonic = config.get(_APP, _MNEMONIC)
+def get_mnemonic_secret() -> bytes:
+    mnemonic = config.get(_APP, _MNEMONIC_SECRET)
     if mnemonic is None:
         return None
-    return mnemonic.decode()
+    return mnemonic
+
+
+def get_mnemonic_type() -> int:
+    return _get_uint8(_APP, _MNEMONIC_TYPE)
 
 
 def has_passphrase() -> bool:
@@ -82,8 +98,11 @@ def get_homescreen() -> bytes:
     return config.get(_APP, _HOMESCREEN, True)  # public
 
 
-def load_mnemonic(mnemonic: str, needs_backup: bool, no_backup: bool) -> None:
-    config.set(_APP, _MNEMONIC, mnemonic.encode())
+def store_mnemonic(
+    secret: bytes, mnemonic_type: int, needs_backup: bool, no_backup: bool
+) -> None:
+    config.set(_APP, _MNEMONIC_SECRET, secret)
+    _set_uint8(_APP, _MNEMONIC_TYPE, mnemonic_type)
     config.set(_APP, _VERSION, _STORAGE_VERSION)
     _set_bool(_APP, _NO_BACKUP, no_backup)
     if not no_backup:

src/apps/debug/__init__.py

@@ -9,7 +9,7 @@ if __debug__:
     from trezor.messages.DebugLinkState import DebugLinkState
     from trezor.ui import confirm, swipe
     from trezor.wire import register, protobuf_workflow
-    from apps.common import storage
+    from apps.common import storage, mnemonic
 
     reset_internal_entropy = None
     reset_current_words = None
@@ -29,7 +29,7 @@ if __debug__:
 
     async def dispatch_DebugLinkGetState(ctx, msg):
         m = DebugLinkState()
-        m.mnemonic = storage.get_mnemonic()
+        m.mnemonic_secret, m.mnemonic_type = mnemonic.get()
         m.passphrase_protection = storage.has_passphrase()
         m.reset_word_pos = reset_word_index
         m.reset_entropy = reset_internal_entropy

src/apps/management/backup_device.py

@@ -1,7 +1,7 @@
 from trezor import wire
 from trezor.messages.Success import Success
 
-from apps.common import storage
+from apps.common import mnemonic, storage
 from apps.management.reset_device import (
     check_mnemonic,
     show_mnemonic,
@@ -16,7 +16,7 @@ async def backup_device(ctx, msg):
     if not storage.needs_backup():
         raise wire.ProcessError("Seed already backed up")
 
-    mnemonic = storage.get_mnemonic()
+    words = mnemonic.restore()
 
     # warn user about mnemonic safety
     await show_warning(ctx)
@@ -26,8 +26,8 @@ async def backup_device(ctx, msg):
 
     while True:
         # show mnemonic and require confirmation of a random word
-        await show_mnemonic(ctx, mnemonic)
-        if await check_mnemonic(ctx, mnemonic):
+        await show_mnemonic(ctx, words)
+        if await check_mnemonic(ctx, words):
             break
         await show_wrong_entry(ctx)
 

src/apps/management/load_device.py

@@ -4,7 +4,7 @@ from trezor.messages.Success import Success
 from trezor.pin import pin_to_int
 from trezor.ui.text import Text
 
-from apps.common import storage
+from apps.common import mnemonic, storage
 from apps.common.confirm import require_confirm
 
 
@@ -24,7 +24,13 @@ async def load_device(ctx, msg):
     text.normal("Continue only if you", "know what you are doing!")
     await require_confirm(ctx, text)
 
-    storage.load_mnemonic(mnemonic=msg.mnemonic, needs_backup=True, no_backup=False)
+    secret = mnemonic.process([msg.mnemonic], mnemonic.TYPE_BIP39)
+    storage.store_mnemonic(
+        secret=secret,
+        mnemonic_type=mnemonic.TYPE_BIP39,
+        needs_backup=True,
+        no_backup=False,
+    )
     storage.load_settings(use_passphrase=msg.passphrase_protection, label=msg.label)
     if msg.pin:
         config.change_pin(pin_to_int(""), pin_to_int(msg.pin))

src/apps/management/recovery_device.py

@@ -15,7 +15,7 @@ from trezor.ui.text import Text
 from trezor.ui.word_select import WordSelector
 from trezor.utils import consteq, format_ordinal
 
-from apps.common import storage
+from apps.common import mnemonic, storage
 from apps.common.confirm import require_confirm
 from apps.management.change_pin import request_pin_ack, request_pin_confirm
 
@@ -47,11 +47,11 @@ async def recovery_device(ctx, msg):
     wordcount = await request_wordcount(ctx)
 
     # ask for mnemonic words one by one
-    mnemonic = await request_mnemonic(ctx, wordcount)
+    words = await request_mnemonic(ctx, wordcount)
 
     # check mnemonic validity
     if msg.enforce_wordlist or msg.dry_run:
-        if not bip39.check(mnemonic):
+        if not bip39.check(words):
             raise wire.ProcessError("Mnemonic is not valid")
 
     # ask for pin repeatedly
@@ -60,10 +60,13 @@ async def recovery_device(ctx, msg):
     else:
         newpin = ""
 
+    secret = mnemonic.process([words], mnemonic.TYPE_BIP39)
+
     # dry run
     if msg.dry_run:
-        digest_input = sha256(mnemonic).digest()
-        digest_stored = sha256(storage.get_mnemonic()).digest()
+        digest_input = sha256(secret).digest()
+        stored, _ = mnemonic.get()
+        digest_stored = sha256(stored).digest()
         if consteq(digest_stored, digest_input):
             return Success(
                 message="The seed is valid and matches the one in the device"
@@ -78,7 +81,12 @@ async def recovery_device(ctx, msg):
         config.change_pin(pin_to_int(""), pin_to_int(newpin))
     storage.set_u2f_counter(msg.u2f_counter)
     storage.load_settings(label=msg.label, use_passphrase=msg.passphrase_protection)
-    storage.load_mnemonic(mnemonic=mnemonic, needs_backup=False, no_backup=False)
+    storage.store_mnemonic(
+        secret=secret,
+        mnemonic_type=mnemonic.TYPE_BIP39,
+        needs_backup=False,
+        no_backup=False,
+    )
 
     return Success(message="Device recovered")
 

src/apps/management/reset_device.py

@@ -14,7 +14,7 @@ from trezor.ui.scroll import Scrollpage, animate_swipe, paginate
 from trezor.ui.text import Text
 from trezor.utils import chunks, format_ordinal
 
-from apps.common import storage
+from apps.common import mnemonic, storage
 from apps.common.confirm import require_confirm
 from apps.management.change_pin import request_pin_confirm
 
@@ -59,7 +59,7 @@ async def reset_device(ctx, msg):
 
     # request external entropy and compute mnemonic
     ent_ack = await ctx.call(EntropyRequest(), MessageType.EntropyAck)
-    mnemonic = generate_mnemonic(msg.strength, internal_ent, ent_ack.entropy)
+    words = generate_mnemonic(msg.strength, internal_ent, ent_ack.entropy)
 
     if not msg.skip_backup and not msg.no_backup:
         # require confirmation of the mnemonic safety
@@ -67,8 +67,8 @@ async def reset_device(ctx, msg):
 
         # show mnemonic and require confirmation of a random word
         while True:
-            await show_mnemonic(ctx, mnemonic)
-            if await check_mnemonic(ctx, mnemonic):
+            await show_mnemonic(ctx, words)
+            if await check_mnemonic(ctx, words):
                 break
             await show_wrong_entry(ctx)
 
@@ -77,10 +77,14 @@ async def reset_device(ctx, msg):
         if not config.change_pin(pin_to_int(""), pin_to_int(newpin)):
             raise wire.ProcessError("Could not change PIN")
 
+    secret = mnemonic.process([words], mnemonic.TYPE_BIP39)
     # write settings and mnemonic into storage
     storage.load_settings(label=msg.label, use_passphrase=msg.passphrase_protection)
-    storage.load_mnemonic(
-        mnemonic=mnemonic, needs_backup=msg.skip_backup, no_backup=msg.no_backup
+    storage.store_mnemonic(
+        secret=secret,
+        mnemonic_type=mnemonic.TYPE_BIP39,
+        needs_backup=msg.skip_backup,
+        no_backup=msg.no_backup,
     )
 
     # show success message.  if we skipped backup, it's possible that homescreen
@@ -98,8 +102,7 @@ def generate_mnemonic(strength: int, int_entropy: bytes, ext_entropy: bytes) ->
     ehash.update(int_entropy)
     ehash.update(ext_entropy)
     entropy = ehash.digest()
-    mnemonic = bip39.from_data(entropy[: strength // 8])
-    return mnemonic
+    return bip39.from_data(entropy[: strength // 8])
 
 
 async def show_warning(ctx):