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keystore: handle unusual derivation paths in PSBT

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If a tx contained a derivation path for a pubkey,
with a length=2 der suffix,
with the first element of the suffix not in (0, 1),
with a fingerprint that matches either our root or intermediate fp,
then processing that tx would raise and result in a crash reporter.

Traceback (most recent call last):
  File ".../electrum/electrum/gui/qt/main_window.py", line 2718, in do_process_from_text
    self.show_transaction(tx)
  File ".../electrum/electrum/gui/qt/main_window.py", line 1041, in show_transaction
    show_transaction(tx, parent=self, desc=tx_desc)
  File ".../electrum/electrum/gui/qt/transaction_dialog.py", line 84, in show_transaction
    d = TxDialog(tx, parent=parent, desc=desc, prompt_if_unsaved=prompt_if_unsaved)
  File ".../electrum/electrum/gui/qt/transaction_dialog.py", line 680, in __init__
    self.set_tx(tx)
  File ".../electrum/electrum/gui/qt/transaction_dialog.py", line 218, in set_tx
    tx.add_info_from_wallet(self.wallet)
  File ".../electrum/electrum/transaction.py", line 1944, in add_info_from_wallet
    wallet.add_input_info(txin, only_der_suffix=only_der_suffix)
  File ".../electrum/electrum/wallet.py", line 1573, in add_input_info
    is_mine = self._learn_derivation_path_for_address_from_txinout(txin, address)
  File ".../electrum/electrum/wallet.py", line 2609, in _learn_derivation_path_for_address_from_txinout
    pubkey, der_suffix = ks.find_my_pubkey_in_txinout(txinout, only_der_suffix=True)
  File ".../electrum/electrum/keystore.py", line 155, in find_my_pubkey_in_txinout
    path = self.get_pubkey_derivation(pubkey, txinout, only_der_suffix=only_der_suffix)
  File ".../electrum/electrum/keystore.py", line 391, in get_pubkey_derivation
    if not test_der_suffix_against_pubkey(der_suffix, pubkey):
  File ".../electrum/electrum/keystore.py", line 368, in test_der_suffix_against_pubkey
    if pubkey != self.derive_pubkey(*der_suffix):
  File ".../electrum/electrum/keystore.py", line 491, in derive_pubkey
    assert for_change in (0, 1)
AssertionError
This commit is contained in:
SomberNight
2020-12-09 09:38:40 +01:00
parent 0c3f360385
commit ac223073ba
2 changed files with 27 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
electrum/keystore.py
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@@ -52,6 +52,9 @@ if TYPE_CHECKING:
from .wallet_db import WalletDB
class CannotDerivePubkey(Exception): pass
class KeyStore(Logger, ABC):
type: str
@@ -356,16 +359,25 @@ class MasterPublicKeyMixin(ABC):
@abstractmethod
def derive_pubkey(self, for_change: int, n: int) -> bytes:
"""Returns pubkey at given path.
May raise CannotDerivePubkey.
"""
pass
def get_pubkey_derivation(self, pubkey: bytes,
txinout: Union['PartialTxInput', 'PartialTxOutput'],
*, only_der_suffix=True) \
-> Union[Sequence[int], str, None]:
def get_pubkey_derivation(
self,
pubkey: bytes,
txinout: Union['PartialTxInput', 'PartialTxOutput'],
*,
only_der_suffix=True,
) -> Union[Sequence[int], str, None]:
def test_der_suffix_against_pubkey(der_suffix: Sequence[int], pubkey: bytes) -> bool:
if len(der_suffix) != 2:
return False
if pubkey != self.derive_pubkey(*der_suffix):
try:
if pubkey != self.derive_pubkey(*der_suffix):
return False
except CannotDerivePubkey:
return False
return True
@@ -488,7 +500,8 @@ class Xpub(MasterPublicKeyMixin):
@lru_cache(maxsize=None)
def derive_pubkey(self, for_change: int, n: int) -> bytes:
for_change = int(for_change)
assert for_change in (0, 1)
if for_change not in (0, 1):
raise CannotDerivePubkey("forbidden path")
xpub = self.xpub_change if for_change else self.xpub_receive
if xpub is None:
rootnode = self.get_bip32_node_for_xpub()
@@ -658,7 +671,8 @@ class Old_KeyStore(MasterPublicKeyMixin, Deterministic_KeyStore):
@lru_cache(maxsize=None)
def derive_pubkey(self, for_change, n) -> bytes:
for_change = int(for_change)
assert for_change in (0, 1)
if for_change not in (0, 1):
raise CannotDerivePubkey("forbidden path")
return self.get_pubkey_from_mpk(self.mpk, for_change, n)
def _get_private_key_from_stretched_exponent(self, for_change, n, secexp):