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Code Issues Releases Wiki Activity

wallet/signing: restrict segwit change output

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This commit is contained in:
Jan Pochyla 2017-11-29 13:14:22 +01:00
parent 8b85078730
commit 69d030a8fa
1 changed files with 11 additions and 2 deletions
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13
src/apps/wallet/sign_tx/signing.py
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@ -59,6 +59,7 @@ async def check_tx_fee(tx: SignTx, root):
tx_req.details = TxRequestDetailsType()
total_in = 0 # sum of input amounts
segwit_in = 0 # sum of segwit input amounts
total_out = 0 # sum of output amounts
change_out = 0 # change output amount
wallet_path = [] # common prefix of input paths
@ -82,6 +83,7 @@ async def check_tx_fee(tx: SignTx, root):
raise SigningError(FailureType.DataError,
'Segwit input without amount')
segwit[i] = True
segwit_in += txi.amount
total_in += txi.amount
elif txi.script_type == InputScriptType.SPENDADDRESS:
segwit[i] = False
@ -97,7 +99,7 @@ async def check_tx_fee(tx: SignTx, root):
txo_bin.amount = txo.amount
txo_bin.script_pubkey = output_derive_script(txo, coin, root)
weight.add_output(txo_bin.script_pubkey)
if output_is_change(txo, wallet_path):
if output_is_change(txo, wallet_path, segwit_in):
if change_out != 0:
raise SigningError(FailureType.ProcessError,
'Only one change output is valid')
@ -396,8 +398,15 @@ def get_address_for_change(o: TxOutputType, coin: CoinType, root):
return get_address(input_script_type, coin, node_derive(root, o.address_n))
def output_is_change(o: TxOutputType, wallet_path: list) -> bool:
def output_is_change(o: TxOutputType, wallet_path: list, segwit_in: int) -> bool:
address_n = o.address_n
is_segwit = (o.script_type == OutputScriptType.PAYTOWITNESS or
o.script_type == OutputScriptType.PAYTOP2SHWITNESS)
if is_segwit and o.amount > segwit_in:
# if the output is segwit, make sure it doesn't spend more than what the
# segwit inputs paid. this is to prevent user being tricked into
# creating ANYONECANSPEND outputs before full segwit activation.
return False
return (address_n is not None and wallet_path is not None
and wallet_path == address_n[:-_BIP32_WALLET_DEPTH]
and address_n[-2] == _BIP32_CHANGE_CHAIN