AaronFiore/electrum
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channel backups: add MAC

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This commit is contained in:
ThomasV
2020-06-16 11:52:08 +02:00
parent 6922d81a1e
commit f9788a5d90
2 changed files with 16 additions and 9 deletions
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16
electrum/crypto.py
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@@ -229,21 +229,29 @@ def pw_decode_bytes(data: str, password: Union[bytes, str], *, version:int) -> b
return pw_decode_raw(data_bytes, password, version=version) return pw_decode_raw(data_bytes, password, version=version)
def pw_encode_b64_with_version(data: bytes, password: Union[bytes, str]) -> str: def pw_encode_with_version_and_mac(data: bytes, password: Union[bytes, str]) -> str:
"""plaintext bytes -> base64 ciphertext""" """plaintext bytes -> base64 ciphertext"""
# https://crypto.stackexchange.com/questions/202/should-we-mac-then-encrypt-or-encrypt-then-mac
# Encrypt-and-MAC. The MAC will be used to detect invalid passwords
version = PW_HASH_VERSION_LATEST version = PW_HASH_VERSION_LATEST
mac = sha256(data)[0:4]
ciphertext = pw_encode_raw(data, password, version=version) ciphertext = pw_encode_raw(data, password, version=version)
ciphertext_b64 = base64.b64encode(bytes([version]) + ciphertext) ciphertext_b64 = base64.b64encode(bytes([version]) + ciphertext + mac)
return ciphertext_b64.decode('utf8') return ciphertext_b64.decode('utf8')
def pw_decode_b64_with_version(data: str, password: Union[bytes, str]) -> bytes: def pw_decode_with_version_and_mac(data: str, password: Union[bytes, str]) -> bytes:
"""base64 ciphertext -> plaintext bytes""" """base64 ciphertext -> plaintext bytes"""
data_bytes = bytes(base64.b64decode(data)) data_bytes = bytes(base64.b64decode(data))
version = int(data_bytes[0]) version = int(data_bytes[0])
encrypted = data_bytes[1:-4]
mac = data_bytes[-4:]
if version not in KNOWN_PW_HASH_VERSIONS: if version not in KNOWN_PW_HASH_VERSIONS:
raise UnexpectedPasswordHashVersion(version) raise UnexpectedPasswordHashVersion(version)
return pw_decode_raw(data_bytes[1:], password, version=version) decrypted = pw_decode_raw(encrypted, password, version=version)
if sha256(decrypted)[0:4] != mac:
raise InvalidPassword()
return decrypted
def pw_encode(data: str, password: Union[bytes, str, None], *, version: int) -> str: def pw_encode(data: str, password: Union[bytes, str, None], *, version: int) -> str:

9
electrum/lnworker.py
View File

@@ -66,8 +66,7 @@ from .lnrouter import (RouteEdge, LNPaymentRoute, LNPaymentPath, is_route_sane_t
from .address_synchronizer import TX_HEIGHT_LOCAL from .address_synchronizer import TX_HEIGHT_LOCAL
from . import lnsweep from . import lnsweep
from .lnwatcher import LNWalletWatcher from .lnwatcher import LNWalletWatcher
from .crypto import pw_encode_bytes, pw_decode_bytes, PW_HASH_VERSION_LATEST from .crypto import pw_encode_with_version_and_mac, pw_decode_with_version_and_mac
from .crypto import pw_encode_b64_with_version, pw_decode_b64_with_version
from .lnutil import ChannelBackupStorage from .lnutil import ChannelBackupStorage
from .lnchannel import ChannelBackup from .lnchannel import ChannelBackup
from .channel_db import UpdateStatus from .channel_db import UpdateStatus
@@ -1397,8 +1396,8 @@ class LNWallet(LNWorker):
xpub = self.wallet.get_fingerprint() xpub = self.wallet.get_fingerprint()
backup_bytes = self.create_channel_backup(channel_id).to_bytes() backup_bytes = self.create_channel_backup(channel_id).to_bytes()
assert backup_bytes == ChannelBackupStorage.from_bytes(backup_bytes).to_bytes(), "roundtrip failed" assert backup_bytes == ChannelBackupStorage.from_bytes(backup_bytes).to_bytes(), "roundtrip failed"
encrypted = pw_encode_b64_with_version(backup_bytes, xpub) encrypted = pw_encode_with_version_and_mac(backup_bytes, xpub)
assert backup_bytes == pw_decode_b64_with_version(encrypted, xpub), "encrypt failed" assert backup_bytes == pw_decode_with_version_and_mac(encrypted, xpub), "encrypt failed"
return 'channel_backup:' + encrypted return 'channel_backup:' + encrypted
@@ -1454,7 +1453,7 @@ class LNBackups(Logger):
assert data.startswith('channel_backup:') assert data.startswith('channel_backup:')
encrypted = data[15:] encrypted = data[15:]
xpub = self.wallet.get_fingerprint() xpub = self.wallet.get_fingerprint()
decrypted = pw_decode_b64_with_version(encrypted, xpub) decrypted = pw_decode_with_version_and_mac(encrypted, xpub)
cb_storage = ChannelBackupStorage.from_bytes(decrypted) cb_storage = ChannelBackupStorage.from_bytes(decrypted)
channel_id = cb_storage.channel_id().hex() channel_id = cb_storage.channel_id().hex()
d = self.db.get_dict("channel_backups") d = self.db.get_dict("channel_backups")