When signing a segwit transaction with non-segwit inputs, this line fails because tx_in.witness is not defined.
A simple fix is to initialize self.witness = b'' in the TxIn constructor. Then TxIn.witness is always defined, result += int_to_little_endian(len(tx_in.witness), 1) correctly writes b'\x00' representing empty witness for non-segwit inputs, and for item in tx_in.witness: is skipped because it has nothing to iterate over.
scgbckbone
commented
4 years ago
When signing a segwit transaction with non-segwit inputs, this line fails because
tx_in.witnessis not defined.A simple fix is to initialize
self.witness = b''in theTxInconstructor. ThenTxIn.witnessis always defined,result += int_to_little_endian(len(tx_in.witness), 1)correctly writesb'\x00'representing empty witness for non-segwit inputs, andfor item in tx_in.witness:is skipped because it has nothing to iterate over.