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slip39: Fix mnemonic padding check in MicroPython.

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This commit is contained in:
Andrew Kozlik 2019-04-12 15:52:28 +02:00
parent e9a02ebc76
commit db03e2e000
2 changed files with 7 additions and 11 deletions
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17
src/trezor/crypto/slip39.py
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@ -178,7 +178,7 @@ class ShamirMnemonic(object):
"""Converts a list of base 1024 indices in big endian order to an integer value."""
value = 0
for index in indices:
value = value * cls.RADIX + index
value = (value << cls.RADIX_BITS) + index
return value
@classmethod
@ -352,7 +352,8 @@ class ShamirMnemonic(object):
)
)
if (10 * (len(mnemonic_data) - self.METADATA_LENGTH_WORDS)) % 16 > 8:
padding_len = (10 * (len(mnemonic_data) - self.METADATA_LENGTH_WORDS)) % 16
if padding_len > 8:
raise MnemonicError("Invalid mnemonic length.")
if not self.rs1024_verify_checksum(mnemonic_data):
@ -379,15 +380,11 @@ class ShamirMnemonic(object):
self.ID_EXP_LENGTH_WORDS + 2 : -self.CHECKSUM_LENGTH_WORDS
]
# The length of the master secret in bytes is required to be even, so find the largest even
# integer, which is less than or equal to value_word_count * 10 / 8.
value_byte_count = 2 * math.floor(len(value_data) * 5 / 8)
value_byte_count = (10 * len(value_data) - padding_len) // 8
value_int = self._int_from_indices(value_data)
try:
value = value_int.to_bytes(value_byte_count, "big")
except OverflowError:
raise MnemonicError("Invalid mnemonic padding.") from None
if value_data[0] >= 1 << (10 - padding_len):
raise MnemonicError("Invalid mnemonic padding.")
value = value_int.to_bytes(value_byte_count, "big")
return (
identifier,

1
tests/test_trezor.crypto.slip39.py
View File

@ -10,7 +10,6 @@ class TestCryptoSlip39(unittest.TestCase):
def test_shamir(self):
shamir_mnemonic = slip39.ShamirMnemonic()
for mnemonics, secret in vectors:
print(mnemonics, secret)
if secret:
self.assertEqual(shamir_mnemonic.combine_mnemonics(mnemonics, b"TREZOR"), unhexlify(secret))
else: