Пример #1
0
    def test_version_bytes(self):
        xprv_headers_b58 = {
            'standard': 'tprv',
            'p2wpkh-p2sh': 'uprv',
            'p2wsh-p2sh': 'Uprv',
            'p2wpkh': 'vprv',
            'p2wsh': 'Vprv',
        }
        xpub_headers_b58 = {
            'standard': 'tpub',
            'p2wpkh-p2sh': 'upub',
            'p2wsh-p2sh': 'Upub',
            'p2wpkh': 'vpub',
            'p2wsh': 'Vpub',
        }
        for xtype, xkey_header_bytes in constants.net.XPRV_HEADERS.items():
            xkey_header_bytes = bfh("%08x" % xkey_header_bytes)
            xkey_bytes = xkey_header_bytes + bytes([0] * 74)
            xkey_b58 = EncodeBase58Check(xkey_bytes)
            self.assertTrue(xkey_b58.startswith(xprv_headers_b58[xtype]))

            xkey_bytes = xkey_header_bytes + bytes([255] * 74)
            xkey_b58 = EncodeBase58Check(xkey_bytes)
            self.assertTrue(xkey_b58.startswith(xprv_headers_b58[xtype]))

        for xtype, xkey_header_bytes in constants.net.XPUB_HEADERS.items():
            xkey_header_bytes = bfh("%08x" % xkey_header_bytes)
            xkey_bytes = xkey_header_bytes + bytes([0] * 74)
            xkey_b58 = EncodeBase58Check(xkey_bytes)
            self.assertTrue(xkey_b58.startswith(xpub_headers_b58[xtype]))

            xkey_bytes = xkey_header_bytes + bytes([255] * 74)
            xkey_b58 = EncodeBase58Check(xkey_bytes)
            self.assertTrue(xkey_b58.startswith(xpub_headers_b58[xtype]))
Пример #2
0
    def do_send(self, tx):
        def on_success(result):
            window.show_message(
                _("Your transaction was sent to the cosigning pool.") + '\n' +
                _("Open your cosigner wallet to retrieve it."))

        def on_failure(exc_info):
            e = exc_info[1]
            try:
                traceback.print_exception(*exc_info)
            except OSError:
                pass
            window.show_error(
                _("Failed to send transaction to cosigning pool") + ':\n' +
                str(e))

        for window, xpub, K, _hash in self.cosigner_list:
            if not self.cosigner_can_sign(tx, xpub):
                continue
            # construct message
            raw_tx_bytes = bfh(str(tx))
            public_key = ecc.ECPubkey(K)
            message = public_key.encrypt_message(raw_tx_bytes).decode('ascii')
            # send message
            task = lambda: server.put(_hash, message)
            msg = _('Sending transaction to cosigning pool...')
            WaitingDialog(window, msg, task, on_success, on_failure)
Пример #3
0
 def f(x_pubkey):
     if is_xpubkey(x_pubkey):
         xpub, s = parse_xpubkey(x_pubkey)
     else:
         xpub = xpub_from_pubkey(0, bfh(x_pubkey))
         s = []
     return self._make_node_path(xpub, s)
Пример #4
0
def xfp_from_xpub(xpub):
    # sometime we need to BIP32 fingerprint value: 4 bytes of ripemd(sha256(pubkey))
    # UNTESTED
    kk = bfh(Xpub.get_pubkey_from_xpub(xpub, []))
    assert len(kk) == 33
    xfp, = unpack('<I', hash_160(kk)[0:4])
    return xfp
Пример #5
0
 def f(x_pubkey):
     if is_xpubkey(x_pubkey):
         xpub, s = parse_xpubkey(x_pubkey)
     else:
         xpub = xpub_from_pubkey(0, bfh(x_pubkey))
         s = []
     node = self.ckd_public.deserialize(xpub)
     return self.types.HDNodePathType(node=node,
                                      address_n=s)
Пример #6
0
def trezor_validate_op_return_output_and_get_data(output: TxOutput) -> bytes:
    if output.type != TYPE_SCRIPT:
        raise Exception("Unexpected output type: {}".format(output.type))
    script = bfh(output.address)
    if not (script[0] == opcodes.OP_RETURN and
            script[1] == len(script) - 2 and script[1] <= 75):
        raise Exception(_("Only OP_RETURN scripts, with one constant push, are supported."))
    if output.value != 0:
        raise Exception(_("Amount for OP_RETURN output must be zero."))
    return script[2:]
Пример #7
0
        def write_kv(ktype, val, key=b''):
            # serialize helper: write w/ size and key byte
            out_fd.write(my_var_int(1 + len(key)))
            out_fd.write(bytes([ktype]) + key)

            if isinstance(val, str):
                val = bfh(val)

            out_fd.write(my_var_int(len(val)))
            out_fd.write(val)
Пример #8
0
 def show_qr(self):
     text = bfh(str(self.tx))
     text = base_encode(text, base=43)
     try:
         self.main_window.show_qrcode(text, 'Transaction', parent=self)
     except qrcode.exceptions.DataOverflowError:
         self.show_error(
             _('Failed to display QR code.') + '\n' +
             _('Transaction is too large in size.'))
     except Exception as e:
         self.show_error(_('Failed to display QR code.') + '\n' + str(e))
Пример #9
0
 def electrum_tx_to_txtype(self, tx):
     t = self.types.TransactionType()
     d = deserialize(tx.raw)
     t.version = d['version']
     t.lock_time = d['lockTime']
     inputs = self.tx_inputs(tx)
     t.inputs.extend(inputs)
     for vout in d['outputs']:
         o = t.bin_outputs.add()
         o.amount = vout['value']
         o.script_pubkey = bfh(vout['scriptPubKey'])
     return t
Пример #10
0
 def test_push_script(self):
     # https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki#push-operators
     self.assertEqual(push_script(''), bh2u(bytes([opcodes.OP_0])))
     self.assertEqual(push_script('07'), bh2u(bytes([opcodes.OP_7])))
     self.assertEqual(push_script('10'), bh2u(bytes([opcodes.OP_16])))
     self.assertEqual(push_script('81'), bh2u(bytes([opcodes.OP_1NEGATE])))
     self.assertEqual(push_script('11'), '0111')
     self.assertEqual(push_script(75 * '42'), '4b' + 75 * '42')
     self.assertEqual(
         push_script(76 * '42'),
         bh2u(bytes([opcodes.OP_PUSHDATA1]) + bfh('4c' + 76 * '42')))
     self.assertEqual(
         push_script(100 * '42'),
         bh2u(bytes([opcodes.OP_PUSHDATA1]) + bfh('64' + 100 * '42')))
     self.assertEqual(
         push_script(255 * '42'),
         bh2u(bytes([opcodes.OP_PUSHDATA1]) + bfh('ff' + 255 * '42')))
     self.assertEqual(
         push_script(256 * '42'),
         bh2u(bytes([opcodes.OP_PUSHDATA2]) + bfh('0001' + 256 * '42')))
     self.assertEqual(
         push_script(520 * '42'),
         bh2u(bytes([opcodes.OP_PUSHDATA2]) + bfh('0802' + 520 * '42')))
Пример #11
0
 def electrum_tx_to_txtype(self, tx):
     t = self.types.TransactionType()
     if tx is None:
         # probably for segwit input and we don't need this prev txn
         return t
     d = deserialize(tx.raw)
     t.version = d['version']
     t.lock_time = d['lockTime']
     inputs = self.tx_inputs(tx)
     t._extend_inputs(inputs)
     for vout in d['outputs']:
         o = t._add_bin_outputs()
         o.amount = vout['value']
         o.script_pubkey = bfh(vout['scriptPubKey'])
     return t
Пример #12
0
    def _do_test_bip32(self, seed, sequence):
        xprv, xpub = bip32_root(bfh(seed), 'standard')
        self.assertEqual("m/", sequence[0:2])
        path = 'm'
        sequence = sequence[2:]
        for n in sequence.split('/'):
            child_path = path + '/' + n
            if n[-1] != "'":
                xpub2 = bip32_public_derivation(xpub, path, child_path)
            xprv, xpub = bip32_private_derivation(xprv, path, child_path)
            if n[-1] != "'":
                self.assertEqual(xpub, xpub2)
            path = child_path

        return xpub, xprv
Пример #13
0
    def test_sign_transaction(self):
        eckey1 = ecc.ECPrivkey(
            bfh('7e1255fddb52db1729fc3ceb21a46f95b8d9fe94cc83425e936a6c5223bb679d'
                ))
        sig1 = eckey1.sign_transaction(
            bfh('5a548b12369a53faaa7e51b5081829474ebdd9c924b3a8230b69aa0be254cd94'
                ))
        self.assertEqual(
            bfh('3045022100902a288b98392254cd23c0e9a49ac6d7920f171b8249a48e484b998f1874a2010220723d844826828f092cf400cb210c4fa0b8cd1b9d1a7f21590e78e022ff6476b9'
                ), sig1)

        eckey2 = ecc.ECPrivkey(
            bfh('c7ce8c1462c311eec24dff9e2532ac6241e50ae57e7d1833af21942136972f23'
                ))
        sig2 = eckey2.sign_transaction(
            bfh('642a2e66332f507c92bda910158dfe46fc10afbf72218764899d3af99a043fac'
                ))
        self.assertEqual(
            bfh('30440220618513f4cfc87dde798ce5febae7634c23e7b9254a1eabf486be820f6a7c2c4702204fef459393a2b931f949e63ced06888f35e286e446dc46feb24b5b5f81c6ed52'
                ), sig2)
Пример #14
0
 def test_add_number_to_script(self):
     # https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki#numbers
     self.assertEqual(add_number_to_script(0), bytes([opcodes.OP_0]))
     self.assertEqual(add_number_to_script(7), bytes([opcodes.OP_7]))
     self.assertEqual(add_number_to_script(16), bytes([opcodes.OP_16]))
     self.assertEqual(add_number_to_script(-1), bytes([opcodes.OP_1NEGATE]))
     self.assertEqual(add_number_to_script(-127), bfh('01ff'))
     self.assertEqual(add_number_to_script(-2), bfh('0182'))
     self.assertEqual(add_number_to_script(17), bfh('0111'))
     self.assertEqual(add_number_to_script(127), bfh('017f'))
     self.assertEqual(add_number_to_script(-32767), bfh('02ffff'))
     self.assertEqual(add_number_to_script(-128), bfh('028080'))
     self.assertEqual(add_number_to_script(128), bfh('028000'))
     self.assertEqual(add_number_to_script(32767), bfh('02ff7f'))
     self.assertEqual(add_number_to_script(-8388607), bfh('03ffffff'))
     self.assertEqual(add_number_to_script(-32768), bfh('03008080'))
     self.assertEqual(add_number_to_script(32768), bfh('03008000'))
     self.assertEqual(add_number_to_script(8388607), bfh('03ffff7f'))
     self.assertEqual(add_number_to_script(-2147483647), bfh('04ffffffff'))
     self.assertEqual(add_number_to_script(-8388608), bfh('0400008080'))
     self.assertEqual(add_number_to_script(8388608), bfh('0400008000'))
     self.assertEqual(add_number_to_script(2147483647), bfh('04ffffff7f'))
Пример #15
0
    def tx_inputs(self, tx, for_sig=False):
        inputs = []
        for txin in tx.inputs():
            txinputtype = self.types.TxInputType()
            if txin['type'] == 'coinbase':
                prev_hash = b"\x00" * 32
                prev_index = 0xffffffff  # signed int -1
            else:
                if for_sig:
                    x_pubkeys = txin['x_pubkeys']
                    if len(x_pubkeys) == 1:
                        x_pubkey = x_pubkeys[0]
                        xpub, s = parse_xpubkey(x_pubkey)
                        xpub_n = self.client_class.expand_path(
                            self.xpub_path[xpub])
                        txinputtype._extend_address_n(xpub_n + s)
                        txinputtype.script_type = self.get_safet_input_script_type(
                            txin['type'])
                    else:

                        def f(x_pubkey):
                            if is_xpubkey(x_pubkey):
                                xpub, s = parse_xpubkey(x_pubkey)
                            else:
                                xpub = xpub_from_pubkey(0, bfh(x_pubkey))
                                s = []
                            return self._make_node_path(xpub, s)

                        pubkeys = list(map(f, x_pubkeys))
                        multisig = self.types.MultisigRedeemScriptType(
                            pubkeys=pubkeys,
                            signatures=list(
                                map(lambda x: bfh(x)[:-1] if x else b'',
                                    txin.get('signatures'))),
                            m=txin.get('num_sig'),
                        )
                        script_type = self.get_safet_input_script_type(
                            txin['type'])
                        txinputtype = self.types.TxInputType(
                            script_type=script_type, multisig=multisig)
                        # find which key is mine
                        for x_pubkey in x_pubkeys:
                            if is_xpubkey(x_pubkey):
                                xpub, s = parse_xpubkey(x_pubkey)
                                if xpub in self.xpub_path:
                                    xpub_n = self.client_class.expand_path(
                                        self.xpub_path[xpub])
                                    txinputtype._extend_address_n(xpub_n + s)
                                    break

                prev_hash = unhexlify(txin['prevout_hash'])
                prev_index = txin['prevout_n']

            if 'value' in txin:
                txinputtype.amount = txin['value']
            txinputtype.prev_hash = prev_hash
            txinputtype.prev_index = prev_index

            if txin.get('scriptSig') is not None:
                script_sig = bfh(txin['scriptSig'])
                txinputtype.script_sig = script_sig

            txinputtype.sequence = txin.get('sequence', 0xffffffff - 1)

            inputs.append(txinputtype)

        return inputs
Пример #16
0
    def sign_transaction(self, tx, password):
        if tx.is_complete():
            return
        client = self.get_client()
        inputs = []
        inputsPaths = []
        pubKeys = []
        chipInputs = []
        redeemScripts = []
        signatures = []
        preparedTrustedInputs = []
        changePath = ""
        output = None
        p2shTransaction = False
        segwitTransaction = False
        pin = ""
        self.get_client(
        )  # prompt for the PIN before displaying the dialog if necessary

        # Fetch inputs of the transaction to sign
        derivations = self.get_tx_derivations(tx)
        for txin in tx.inputs():
            if txin['type'] == 'coinbase':
                self.give_error(
                    "Coinbase not supported")  # should never happen

            if txin['type'] in ['p2sh']:
                p2shTransaction = True

            if txin['type'] in ['p2wpkh-p2sh', 'p2wsh-p2sh']:
                if not self.get_client_electrum().supports_segwit():
                    self.give_error(MSG_NEEDS_FW_UPDATE_SEGWIT)
                segwitTransaction = True

            if txin['type'] in ['p2wpkh', 'p2wsh']:
                if not self.get_client_electrum().supports_native_segwit():
                    self.give_error(MSG_NEEDS_FW_UPDATE_SEGWIT)
                segwitTransaction = True

            pubkeys, x_pubkeys = tx.get_sorted_pubkeys(txin)
            for i, x_pubkey in enumerate(x_pubkeys):
                if x_pubkey in derivations:
                    signingPos = i
                    s = derivations.get(x_pubkey)
                    hwAddress = "%s/%d/%d" % (self.get_derivation()[2:], s[0],
                                              s[1])
                    break
            else:
                self.give_error("No matching x_key for sign_transaction"
                                )  # should never happen

            redeemScript = Transaction.get_preimage_script(txin)
            txin_prev_tx = txin.get('prev_tx')
            if txin_prev_tx is None and not Transaction.is_segwit_input(txin):
                raise Exception(
                    _('Offline signing with {} is not supported for legacy inputs.'
                      ).format(self.device))
            txin_prev_tx_raw = txin_prev_tx.raw if txin_prev_tx else None
            inputs.append([
                txin_prev_tx_raw, txin['prevout_n'], redeemScript,
                txin['prevout_hash'], signingPos,
                txin.get('sequence', 0xffffffff - 1),
                txin.get('value')
            ])
            inputsPaths.append(hwAddress)
            pubKeys.append(pubkeys)

        # Sanity check
        if p2shTransaction:
            for txin in tx.inputs():
                if txin['type'] != 'p2sh':
                    self.give_error(
                        "P2SH / regular input mixed in same transaction not supported"
                    )  # should never happen

        txOutput = var_int(len(tx.outputs()))
        for txout in tx.outputs():
            output_type, addr, amount = txout
            txOutput += int_to_hex(amount, 8)
            script = tx.pay_script(output_type, addr)
            txOutput += var_int(len(script) // 2)
            txOutput += script
        txOutput = bfh(txOutput)

        # Recognize outputs
        # - only one output and one change is authorized (for hw.1 and nano)
        # - at most one output can bypass confirmation (~change) (for all)
        if not p2shTransaction:
            if not self.get_client_electrum().supports_multi_output():
                if len(tx.outputs()) > 2:
                    self.give_error(
                        "Transaction with more than 2 outputs not supported")
            has_change = False
            any_output_on_change_branch = is_any_tx_output_on_change_branch(tx)
            for o in tx.outputs():
                assert o.type == TYPE_ADDRESS
                info = tx.output_info.get(o.address)
                if (info is not None) and len(tx.outputs()) > 1 \
                        and not has_change:
                    index = info.address_index
                    on_change_branch = index[0] == 1
                    # prioritise hiding outputs on the 'change' branch from user
                    # because no more than one change address allowed
                    if on_change_branch == any_output_on_change_branch:
                        changePath = self.get_derivation(
                        )[2:] + "/%d/%d" % index
                        has_change = True
                    else:
                        output = o.address
                else:
                    output = o.address

        self.handler.show_message(
            _("Confirm Transaction on your Ledger device..."))
        try:
            # Get trusted inputs from the original transactions
            for utxo in inputs:
                sequence = int_to_hex(utxo[5], 4)
                if segwitTransaction:
                    tmp = bfh(utxo[3])[::-1]
                    tmp += bfh(int_to_hex(utxo[1], 4))
                    tmp += bfh(int_to_hex(utxo[6], 8))  # txin['value']
                    chipInputs.append({
                        'value': tmp,
                        'witness': True,
                        'sequence': sequence
                    })
                    redeemScripts.append(bfh(utxo[2]))
                elif not p2shTransaction:
                    txtmp = bitcoinTransaction(bfh(utxo[0]))
                    trustedInput = self.get_client().getTrustedInput(
                        txtmp, utxo[1])
                    trustedInput['sequence'] = sequence
                    chipInputs.append(trustedInput)
                    redeemScripts.append(txtmp.outputs[utxo[1]].script)
                else:
                    tmp = bfh(utxo[3])[::-1]
                    tmp += bfh(int_to_hex(utxo[1], 4))
                    chipInputs.append({'value': tmp, 'sequence': sequence})
                    redeemScripts.append(bfh(utxo[2]))

            # Sign all inputs
            firstTransaction = True
            inputIndex = 0
            rawTx = tx.serialize_to_network()
            self.get_client().enableAlternate2fa(False)
            if segwitTransaction:
                self.get_client().startUntrustedTransaction(
                    True, inputIndex, chipInputs, redeemScripts[inputIndex])
                if changePath:
                    # we don't set meaningful outputAddress, amount and fees
                    # as we only care about the alternateEncoding==True branch
                    outputData = self.get_client().finalizeInput(
                        b'', 0, 0, changePath, bfh(rawTx))
                else:
                    outputData = self.get_client().finalizeInputFull(txOutput)
                outputData['outputData'] = txOutput
                transactionOutput = outputData['outputData']
                if outputData['confirmationNeeded']:
                    outputData['address'] = output
                    self.handler.finished()
                    pin = self.handler.get_auth(
                        outputData
                    )  # does the authenticate dialog and returns pin
                    if not pin:
                        raise UserWarning()
                    if pin != 'paired':
                        self.handler.show_message(
                            _("Confirmed. Signing Transaction..."))
                while inputIndex < len(inputs):
                    singleInput = [chipInputs[inputIndex]]
                    self.get_client().startUntrustedTransaction(
                        False, 0, singleInput, redeemScripts[inputIndex])
                    inputSignature = self.get_client().untrustedHashSign(
                        inputsPaths[inputIndex], pin, lockTime=tx.locktime)
                    inputSignature[0] = 0x30  # force for 1.4.9+
                    signatures.append(inputSignature)
                    inputIndex = inputIndex + 1
            else:
                while inputIndex < len(inputs):
                    self.get_client().startUntrustedTransaction(
                        firstTransaction, inputIndex, chipInputs,
                        redeemScripts[inputIndex])
                    if changePath:
                        # we don't set meaningful outputAddress, amount and fees
                        # as we only care about the alternateEncoding==True branch
                        outputData = self.get_client().finalizeInput(
                            b'', 0, 0, changePath, bfh(rawTx))
                    else:
                        outputData = self.get_client().finalizeInputFull(
                            txOutput)
                    outputData['outputData'] = txOutput
                    if firstTransaction:
                        transactionOutput = outputData['outputData']
                    if outputData['confirmationNeeded']:
                        outputData['address'] = output
                        self.handler.finished()
                        pin = self.handler.get_auth(
                            outputData
                        )  # does the authenticate dialog and returns pin
                        if not pin:
                            raise UserWarning()
                        if pin != 'paired':
                            self.handler.show_message(
                                _("Confirmed. Signing Transaction..."))
                    else:
                        # Sign input with the provided PIN
                        inputSignature = self.get_client().untrustedHashSign(
                            inputsPaths[inputIndex], pin, lockTime=tx.locktime)
                        inputSignature[0] = 0x30  # force for 1.4.9+
                        signatures.append(inputSignature)
                        inputIndex = inputIndex + 1
                    if pin != 'paired':
                        firstTransaction = False
        except UserWarning:
            self.handler.show_error(_('Cancelled by user'))
            return
        except BTChipException as e:
            if e.sw == 0x6985:  # cancelled by user
                return
            elif e.sw == 0x6982:
                raise  # pin lock. decorator will catch it
            else:
                traceback.print_exc(file=sys.stderr)
                self.give_error(e, True)
        except BaseException as e:
            traceback.print_exc(file=sys.stdout)
            self.give_error(e, True)
        finally:
            self.handler.finished()

        for i, txin in enumerate(tx.inputs()):
            signingPos = inputs[i][4]
            tx.add_signature_to_txin(i, signingPos, bh2u(signatures[i]))
        tx.raw = tx.serialize()
Пример #17
0
    def build_psbt(self, tx, wallet=None, xfp=None):
        # Render a PSBT file, for upload to Coldcard.
        #
        if xfp is None:
            # need fingerprint of MASTER xpub, not the derived key
            xfp = self.ckcc_xfp

        inputs = tx.inputs()

        if 'prev_tx' not in inputs[0]:
            # fetch info about inputs, if needed?
            # - needed during export PSBT flow, not normal online signing
            assert wallet, 'need wallet reference'
            wallet.add_hw_info(tx)

        # wallet.add_hw_info installs this attr
        assert hasattr(tx, 'output_info'), 'need data about outputs'

        # Build map of pubkey needed as derivation from master, in PSBT binary format
        # 1) binary version of the common subpath for all keys
        #       m/ => fingerprint LE32
        #       a/b/c => ints
        base_path = pack('<I', xfp)
        for x in self.get_derivation()[2:].split('/'):
            if x.endswith("'"):
                x = int(x[:-1]) | 0x80000000
            else:
                x = int(x)
            base_path += pack('<I', x)

        # 2) all used keys in transaction
        subkeys = {}
        derivations = self.get_tx_derivations(tx)
        for xpubkey in derivations:
            pubkey = xpubkey_to_pubkey(xpubkey)

            # assuming depth two, non-harded: change + index
            aa, bb = derivations[xpubkey]
            assert 0 <= aa < 0x80000000
            assert 0 <= bb < 0x80000000

            subkeys[bfh(pubkey)] = base_path + pack('<II', aa, bb)

        for txin in inputs:
            if txin['type'] == 'coinbase':
                self.give_error("Coinbase not supported")  # but why not?

            if txin['type'] in ['p2sh']:
                self.give_error('Not ready for multisig transactions yet')

            #if txin['type'] in ['p2wpkh-p2sh', 'p2wsh-p2sh']:
            #if txin['type'] in ['p2wpkh', 'p2wsh']:

        # Construct PSBT from start to finish.
        out_fd = io.BytesIO()
        out_fd.write(b'psbt\xff')

        def write_kv(ktype, val, key=b''):
            # serialize helper: write w/ size and key byte
            out_fd.write(my_var_int(1 + len(key)))
            out_fd.write(bytes([ktype]) + key)

            if isinstance(val, str):
                val = bfh(val)

            out_fd.write(my_var_int(len(val)))
            out_fd.write(val)

        # global section: just the unsigned txn
        class CustomTXSerialization(Transaction):
            @classmethod
            def input_script(cls, txin, estimate_size=False):
                return ''

        unsigned = bfh(
            CustomTXSerialization(
                tx.serialize()).serialize_to_network(witness=False))
        write_kv(PSBT_GLOBAL_UNSIGNED_TX, unsigned)

        # end globals section
        out_fd.write(b'\x00')

        # inputs section
        for txin in inputs:
            utxo = txin['prev_tx'].outputs()[txin['prevout_n']]
            spendable = txin['prev_tx'].serialize_output(utxo)
            write_kv(PSBT_IN_WITNESS_UTXO, spendable)

            pubkeys, x_pubkeys = tx.get_sorted_pubkeys(txin)

            pubkeys = [bfh(k) for k in pubkeys]

            for k in pubkeys:
                write_kv(PSBT_IN_BIP32_DERIVATION, subkeys[k], k)

            out_fd.write(b'\x00')

        # outputs section
        for o in tx.outputs():
            # can be empty, but must be present, and helpful to show change inputs
            # wallet.add_hw_info() adds some data about change outputs into tx.output_info
            if o.address in tx.output_info:
                # this address "is_mine" but might not be change (I like to sent to myself)
                output_info = tx.output_info.get(o.address)
                index, xpubs = output_info.address_index, output_info.sorted_xpubs

                if index[0] == 1 and len(index) == 2:
                    # it is a change output (based on our standard derivation path)
                    assert len(xpubs) == 1  # not expecting multisig
                    xpubkey = xpubs[0]

                    # document its bip32 derivation in output section
                    aa, bb = index
                    assert 0 <= aa < 0x80000000
                    assert 0 <= bb < 0x80000000

                    deriv = base_path + pack('<II', aa, bb)
                    pubkey = self.get_pubkey_from_xpub(xpubkey, index)

                    write_kv(PSBT_OUT_BIP32_DERIVATION, deriv, bfh(pubkey))

            out_fd.write(b'\x00')

        return out_fd.getvalue()