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Code Issues Releases Wiki Activity

fix(core): Fix TxWeightCalculator.

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- Refactor TxWeightCalculator to count inputs and outputs itself.
- Fix witness data weight by adding the weight of the witness stack item count
  for each input in segwit transactions and removing the weight of the
  nonsensical extra inputs count.
- Get multisig pubkey count from multisig.nodes or multisig.pubkeys like in
  multisig_get_pubkeys().
- Fix size of multisig script length encoding in segwit (varint vs. OP_PUSH).
- Improve comments.
This commit is contained in:
Andrew Kozlik 2021-10-31 09:29:54 +01:00 committed by Andrew Kozlik
parent a5bd1643fc
commit 9b579094c0
3 changed files with 41 additions and 40 deletions
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6
core/src/apps/bitcoin/sign_tx/approvers.py
View File

@ -27,7 +27,7 @@ if False:
class Approver:
def __init__(self, tx: SignTx, coin: CoinInfo) -> None:
self.coin = coin
self.weight = tx_weight.TxWeightCalculator(tx.inputs_count, tx.outputs_count)
self.weight = tx_weight.TxWeightCalculator()
# amounts in the current transaction
self.total_in = 0 # sum of input amounts
@ -267,9 +267,7 @@ class CoinJoinApprover(Approver):
raise wire.DataError("Coin name does not match authorization.")
# Upper bound on the user's contribution to the weight of the transaction.
self.our_weight = tx_weight.TxWeightCalculator(
tx.inputs_count, tx.outputs_count
)
self.our_weight = tx_weight.TxWeightCalculator()
# base for coordinator fee to be multiplied by fee_per_anonymity
self.coordinator_fee_base = 0

65
core/src/apps/bitcoin/sign_tx/tx_weight.py
View File

@ -27,7 +27,7 @@ _TXSIZE_INPUT = const(40)
_TXSIZE_OUTPUT = const(8)
# size of a pubkey
_TXSIZE_PUBKEY = const(33)
# size of a DER signature (3 type bytes, 3 len bytes, 33 R, 32 S, 1 sighash
# maximum size of a DER signature (3 type bytes, 3 len bytes, 33 R, 32 S, 1 sighash)
_TXSIZE_SIGNATURE = const(72)
# size of a multiscript without pubkey (1 M, 1 N, 1 checksig)
_TXSIZE_MULTISIGSCRIPT = const(3)
@ -38,32 +38,26 @@ _TXSIZE_WITNESSSCRIPT = const(34)
class TxWeightCalculator:
def __init__(self, inputs_count: int, outputs_count: int):
self.inputs_count = inputs_count
self.counter = 4 * (
_TXSIZE_HEADER
+ _TXSIZE_FOOTER
+ self.ser_length_size(inputs_count)
+ self.ser_length_size(outputs_count)
)
self.segwit = False
def add_witness_header(self) -> None:
if not self.segwit:
self.counter += _TXSIZE_SEGWIT_OVERHEAD
self.counter += self.ser_length_size(self.inputs_count)
self.segwit = True
def __init__(self) -> None:
self.inputs_count = 0
self.outputs_count = 0
self.counter = 4 * (_TXSIZE_HEADER + _TXSIZE_FOOTER)
self.segwit_inputs_count = 0
def add_input(self, i: TxInput) -> None:
self.inputs_count += 1
if i.multisig:
multisig_script_size = _TXSIZE_MULTISIGSCRIPT + len(i.multisig.pubkeys) * (
1 + _TXSIZE_PUBKEY
)
n = len(i.multisig.nodes) if i.multisig.nodes else len(i.multisig.pubkeys)
multisig_script_size = _TXSIZE_MULTISIGSCRIPT + n * (1 + _TXSIZE_PUBKEY)
if i.script_type in common.SEGWIT_INPUT_SCRIPT_TYPES:
multisig_script_size += self.varint_size(multisig_script_size)
else:
multisig_script_size += self.op_push_size(multisig_script_size)
input_script_size = (
1
+ i.multisig.m * (1 + _TXSIZE_SIGNATURE) # the OP_FALSE bug in multisig
+ self.op_push_size(multisig_script_size)
1 # the OP_FALSE bug in multisig
+ i.multisig.m * (1 + _TXSIZE_SIGNATURE)
+ multisig_script_size
)
else:
@ -72,29 +66,38 @@ class TxWeightCalculator:
self.counter += 4 * _TXSIZE_INPUT
if i.script_type in common.NONSEGWIT_INPUT_SCRIPT_TYPES:
input_script_size += self.ser_length_size(input_script_size)
input_script_size += self.varint_size(input_script_size)
self.counter += 4 * input_script_size
elif i.script_type in common.SEGWIT_INPUT_SCRIPT_TYPES:
self.add_witness_header()
self.segwit_inputs_count += 1
if i.script_type == InputScriptType.SPENDP2SHWITNESS:
# add script_sig size
if i.multisig:
self.counter += 4 * (2 + _TXSIZE_WITNESSSCRIPT)
else:
self.counter += 4 * (2 + _TXSIZE_WITNESSPKHASH)
else:
self.counter += 4 # empty
self.counter += input_script_size # discounted witness
self.counter += 4 # empty script_sig (1 byte)
self.counter += 1 + input_script_size # discounted witness
def add_output(self, script: bytes) -> None:
size = len(script) + self.ser_length_size(len(script))
self.counter += 4 * (_TXSIZE_OUTPUT + size)
self.outputs_count += 1
script_size = self.varint_size(len(script)) + len(script)
self.counter += 4 * (_TXSIZE_OUTPUT + script_size)
def get_total(self) -> int:
return self.counter
total = self.counter
total += 4 * self.varint_size(self.inputs_count)
total += 4 * self.varint_size(self.outputs_count)
if self.segwit_inputs_count:
total += _TXSIZE_SEGWIT_OVERHEAD
# add one byte of witness stack item count per non-segwit input
total += self.inputs_count - self.segwit_inputs_count
return total
@staticmethod
def ser_length_size(length: int) -> int:
def varint_size(length: int) -> int:
if length < 253:
return 1
if length < 0x1_0000:

10
core/tests/test_apps.bitcoin.txweight.py
View File

@ -32,7 +32,7 @@ class TestCalculateTxWeight(unittest.TestCase):
address_n=[],
multisig=None)
calculator = TxWeightCalculator(1, 1)
calculator = TxWeightCalculator()
calculator.add_input(inp1)
calculator.add_output(output_derive_script(out1.address, coin))
@ -71,14 +71,14 @@ class TestCalculateTxWeight(unittest.TestCase):
multisig=None,
)
calculator = TxWeightCalculator(1, 2)
calculator = TxWeightCalculator()
calculator.add_input(inp1)
calculator.add_output(output_derive_script(out1.address, coin))
calculator.add_output(output_derive_script(out2.address, coin))
self.assertEqual(calculator.get_total(), 670)
# non-segwit: header, inputs, outputs, locktime 4*(4+65+67+4) = 560
# segwit: segwit header, witness count, 2x witness 1*(2+1+107) = 110
# segwit: segwit header, witness stack item count, witness 1*(2+1+107) = 110
# total 670
def test_native_p2wpkh_txweight(self):
@ -111,14 +111,14 @@ class TestCalculateTxWeight(unittest.TestCase):
multisig=None,
)
calculator = TxWeightCalculator(1, 2)
calculator = TxWeightCalculator()
calculator.add_input(inp1)
calculator.add_output(output_derive_script(out1.address, coin))
calculator.add_output(output_derive_script(out2.address, coin))
self.assertEqual(calculator.get_total(), 566)
# non-segwit: header, inputs, outputs, locktime 4*(4+42+64+4) = 456
# segwit: segwit header, witness count, 2x witness 1*(2+1+107) = 110
# segwit: segwit header, witness stack item count, witness 1*(2+1+107) = 110
# total 566