mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-12-24 07:18:09 +00:00
259 lines
9.0 KiB
Python
259 lines
9.0 KiB
Python
import hashlib
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import sys
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from . import consts, crypto, helpers, prng
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from .norcow import Norcow
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from .pin_log import PinLog
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class Storage:
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def __init__(self):
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self.initialized = False
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self.unlocked = False
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self.dek = None
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self.sak = None
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self.nc = Norcow()
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self.pin_log = PinLog(self.nc)
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def init(self, hardware_salt: bytes = b""):
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"""
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Initializes storage. Normally we would check if EDEK is already present,
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but we simplify things in the python version and suppose we are starting
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a new storage each time.
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"""
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self.nc.init()
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self.initialized = True
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self.hw_salt_hash = hashlib.sha256(hardware_salt).digest()
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edek_esak_pvc = self.nc.get(consts.EDEK_ESEK_PVC_KEY)
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if not edek_esak_pvc:
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self._init_pin()
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def _init_pin(self):
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"""
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Initalizes PIN counters, generates random
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Data Encryption Key and Storage Authentication Key
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"""
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self.dek = prng.random_buffer(consts.DEK_SIZE)
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self.sak = prng.random_buffer(consts.SAK_SIZE)
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self.nc.set(consts.SAT_KEY, crypto.init_hmacs(self.sak))
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self._set_encrypt(consts.VERSION_KEY, consts.NORCOW_VERSION)
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self.nc.set(consts.UNAUTH_VERSION_KEY, consts.NORCOW_VERSION)
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self.nc.set(consts.STORAGE_UPGRADED_KEY, consts.FALSE_WORD)
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self.pin_log.init()
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self._set_wipe_code(consts.WIPE_CODE_EMPTY)
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self._set_pin(consts.PIN_EMPTY)
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self.unlocked = False
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def _set_pin(self, pin: str):
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random_salt = prng.random_buffer(consts.PIN_SALT_SIZE)
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salt = self.hw_salt_hash + random_salt
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kek, keiv = crypto.derive_kek_keiv(salt, pin)
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# Encrypted Data Encryption Key and Encrypted Storage Authentication Key
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edek_esak, tag = crypto.chacha_poly_encrypt(kek, keiv, self.dek + self.sak)
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# Pin Verification Code
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pvc = tag[: consts.PVC_SIZE]
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self.nc.set(consts.EDEK_ESEK_PVC_KEY, random_salt + edek_esak + pvc)
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if pin == consts.PIN_EMPTY:
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self._set_bool(consts.PIN_NOT_SET_KEY, True)
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else:
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self._set_bool(consts.PIN_NOT_SET_KEY, False)
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def _set_wipe_code(self, wipe_code: str):
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if wipe_code == consts.PIN_EMPTY:
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wipe_code = consts.WIPE_CODE_EMPTY
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wipe_code_bytes = wipe_code.encode()
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salt = prng.random_buffer(consts.WIPE_CODE_SALT_SIZE)
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tag = crypto._hmac(salt, wipe_code_bytes)[: consts.WIPE_CODE_TAG_SIZE]
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self.nc.set(consts.WIPE_CODE_DATA_KEY, wipe_code_bytes + salt + tag)
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def wipe(self):
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self.nc.wipe()
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self._init_pin()
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def check_pin(self, pin: str) -> bool:
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self.pin_log.write_attempt()
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data = self.nc.get(consts.EDEK_ESEK_PVC_KEY)
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salt = self.hw_salt_hash + data[: consts.PIN_SALT_SIZE]
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edek_esak = data[consts.PIN_SALT_SIZE : -consts.PVC_SIZE]
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pvc = data[-consts.PVC_SIZE :]
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try:
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dek, sak = crypto.decrypt_edek_esak(pin, salt, edek_esak, pvc)
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self.pin_log.write_success()
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self.dek = dek
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self.sak = sak
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return True
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except crypto.InvalidPinError:
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fails = self.pin_log.get_failures_count()
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if fails >= consts.PIN_MAX_TRIES:
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self.wipe()
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return False
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def lock(self) -> None:
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self.unlocked = False
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def unlock(self, pin: str) -> bool:
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if not self.initialized or not self.check_pin(pin):
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return False
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version = self._decrypt(consts.VERSION_KEY)
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if version != consts.NORCOW_VERSION:
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return False
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self.unlocked = True
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return True
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def has_pin(self) -> bool:
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val = self.nc.get(consts.PIN_NOT_SET_KEY)
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return val != consts.TRUE_BYTE
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def get_pin_rem(self) -> int:
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return consts.PIN_MAX_TRIES - self.pin_log.get_failures_count()
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def change_pin(self, oldpin: str, newpin: str) -> bool:
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if not self.initialized or not self.unlocked:
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return False
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if not self.check_pin(oldpin):
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return False
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self._set_pin(newpin)
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return True
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def get(self, key: int) -> bytes:
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app = key >> 8
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if not self.initialized or consts.is_app_private(app):
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raise RuntimeError("Storage not initialized or app is private")
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if not self.unlocked and not consts.is_app_public(app):
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# public fields can be read from an unlocked device
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raise RuntimeError("Storage locked")
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if consts.is_app_public(app):
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value = self.nc.get(key)
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else:
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value = self._get_encrypted(key)
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if value is False:
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raise RuntimeError("Failed to find key in storage.")
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return value
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def set(self, key: int, val: bytes) -> bool:
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app = key >> 8
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self._check_lock(app)
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if consts.is_app_public(app):
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return self.nc.set(key, val)
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return self._set_encrypt(key, val)
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def set_counter(self, key: int, val: int):
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app = key >> 8
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if not consts.is_app_public(app):
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raise RuntimeError("Counter can be set only for public items")
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if val > consts.UINT32_MAX:
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raise RuntimeError("Failed to set value in storage.")
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counter = val.to_bytes(4, sys.byteorder) + bytearray(
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b"\xFF" * consts.COUNTER_TAIL_SIZE
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)
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self.set(key, counter)
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def next_counter(self, key: int) -> int:
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app = key >> 8
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self._check_lock(app)
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current = self.nc.get(key)
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if current is False:
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self.set_counter(key, 0)
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return 0
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base = int.from_bytes(current[:4], sys.byteorder)
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tail = helpers.to_int_by_words(current[4:])
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tail_count = f"{tail:064b}".count("0")
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increased_count = base + tail_count + 1
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if increased_count > consts.UINT32_MAX:
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raise RuntimeError("Failed to set value in storage.")
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if tail_count == consts.COUNTER_MAX_TAIL:
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self.set_counter(key, increased_count)
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return increased_count
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self.set(
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key,
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current[:4]
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+ helpers.to_bytes_by_words(tail >> 1, consts.COUNTER_TAIL_SIZE),
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)
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return increased_count
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def delete(self, key: int) -> bool:
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app = key >> 8
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self._check_lock(app)
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ret = self.nc.delete(key)
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if consts.is_app_protected(app):
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sat = self._calculate_authentication_tag()
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self.nc.set(consts.SAT_KEY, sat)
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return ret
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def _check_lock(self, app: int):
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if not self.initialized or consts.is_app_private(app):
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raise RuntimeError("Storage not initialized or app is private")
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if not self.unlocked and not consts.is_app_lock_writable(app):
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raise RuntimeError("Storage locked and app is not public-writable")
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def _get_encrypted(self, key: int) -> bytes:
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if not consts.is_app_protected(key):
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raise RuntimeError("Only protected values are encrypted")
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sat = self.nc.get(consts.SAT_KEY)
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if not sat:
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raise RuntimeError("SAT not found")
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if sat != self._calculate_authentication_tag():
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raise RuntimeError("Storage authentication tag mismatch")
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return self._decrypt(key)
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def _decrypt(self, key: int) -> bytes:
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data = self.nc.get(key)
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iv = data[: consts.CHACHA_IV_SIZE]
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# cipher text with MAC
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tag = data[
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consts.CHACHA_IV_SIZE : consts.CHACHA_IV_SIZE + consts.POLY1305_MAC_SIZE
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]
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ciphertext = data[consts.CHACHA_IV_SIZE + consts.POLY1305_MAC_SIZE :]
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return crypto.chacha_poly_decrypt(
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self.dek, key, iv, ciphertext + tag, key.to_bytes(2, sys.byteorder)
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)
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def _set_encrypt(self, key: int, val: bytes):
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# In C, data are preallocated beforehand for encrypted values,
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# to match the behaviour we do the same.
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preallocate = b"\xFF" * (
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consts.CHACHA_IV_SIZE + len(val) + consts.POLY1305_MAC_SIZE
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)
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self.nc.set(key, preallocate)
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if consts.is_app_protected(key >> 8):
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sat = self._calculate_authentication_tag()
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self.nc.set(consts.SAT_KEY, sat)
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iv = prng.random_buffer(consts.CHACHA_IV_SIZE)
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cipher_text, tag = crypto.chacha_poly_encrypt(
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self.dek, iv, val, key.to_bytes(2, sys.byteorder)
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)
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return self.nc.replace(key, iv + tag + cipher_text)
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def _calculate_authentication_tag(self) -> bytes:
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keys = []
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for key in self.nc._get_all_keys():
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if consts.is_app_protected(key >> 8):
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keys.append(key.to_bytes(2, sys.byteorder))
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if not keys:
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return crypto.init_hmacs(self.sak)
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return crypto.calculate_hmacs(self.sak, keys)
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def _set_bool(self, key: int, val: bool) -> bool:
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if val:
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return self.nc.set(key, consts.TRUE_BYTE)
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# False is stored as an empty value
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return self.nc.set(key, consts.FALSE_BYTE)
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def _dump(self) -> bytes:
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return self.nc._dump()
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