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Code Issues Releases Wiki Activity

feat(core): Allow decreasing output amount in RBF transactions.

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This commit is contained in:
Andrew Kozlik 2021-02-23 20:14:45 +01:00 committed by Andrew Kozlik
parent 5593862dc1
commit b10acbe153
6 changed files with 157 additions and 27 deletions
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2
core/CHANGELOG.md
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@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
- Decred staking. [#1249]
### Changed
- Allow decreasing the output value in RBF transactions. [#1491]
### Deprecated
@ -376,3 +377,4 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
[#1415]: https://github.com/trezor/trezor-firmware/pull/1415
[#1467]: https://github.com/trezor/trezor-firmware/issues/1467
[#1518]: https://github.com/trezor/trezor-firmware/pull/1518
[#1491]: https://github.com/trezor/trezor-firmware/issues/1491

100
core/src/apps/bitcoin/sign_tx/approvers.py
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@ -44,6 +44,12 @@ class Approver:
self.amount_unit = tx.amount_unit
def is_payjoin(self) -> bool:
# A PayJoin is a replacement transaction which manipulates the external inputs of the
# original transaction. A replacement transaction is not allowed to remove any inputs from
# the original, so the condition below is equivalent to external_in > orig_external_in.
return self.external_in != self.orig_external_in
async def add_internal_input(self, txi: TxInput) -> None:
self.weight.add_input(txi)
self.total_in += txi.amount
@ -79,6 +85,11 @@ class Approver:
def add_orig_external_output(self, txo: TxOutput) -> None:
self.orig_total_out += txo.amount
async def approve_orig_txids(
self, tx_info: TxInfo, orig_txs: List[OriginalTxInfo]
) -> None:
raise NotImplementedError
async def approve_tx(self, tx_info: TxInfo, orig_txs: List[OriginalTxInfo]) -> None:
raise NotImplementedError
@ -109,11 +120,28 @@ class BasicApprover(Approver):
) -> None:
await super().add_external_output(txo, script_pubkey, orig_txo)
# Replacement transactions must not decrease the value of any external outputs.
if orig_txo and txo.amount < orig_txo.amount:
raise wire.ProcessError(
"Reducing original output amounts is not supported."
)
if orig_txo:
if txo.amount < orig_txo.amount:
# Replacement transactions may need to decrease the value of external outputs to
# bump the fee. This is needed if the original transaction transfers the entire
# account balance ("Send Max").
if self.is_payjoin():
# In case of PayJoin the above could be used to increase other external
# outputs, which would create too much UI complexity.
raise wire.ProcessError(
"Reducing original output amounts is not supported."
)
await helpers.confirm_modify_output(
txo, orig_txo, self.coin, self.amount_unit
)
elif txo.amount > orig_txo.amount:
# PayJoin transactions may increase the value of external outputs without
# confirmation, because approve_tx() together with the branch above ensures that
# the increase is paid by external inputs.
if not self.is_payjoin():
raise wire.ProcessError(
"Increasing original output amounts is not supported."
)
if self.orig_total_in:
# Skip output confirmation for replacement transactions,
@ -125,6 +153,26 @@ class BasicApprover(Approver):
else:
await helpers.confirm_output(txo, self.coin, self.amount_unit)
async def approve_orig_txids(
self, tx_info: TxInfo, orig_txs: List[OriginalTxInfo]
) -> None:
if not orig_txs:
return
if self.is_payjoin():
description = "PayJoin"
elif tx_info.rbf_disabled() and any(
not orig.rbf_disabled() for orig in orig_txs
):
description = "Finalize transaction"
elif len(orig_txs) > 1:
description = "Meld transactions"
else:
description = "Update transaction"
for orig in orig_txs:
await helpers.confirm_replacement(description, orig.orig_hash)
async def approve_tx(self, tx_info: TxInfo, orig_txs: List[OriginalTxInfo]) -> None:
fee = self.total_in - self.total_out
@ -175,30 +223,25 @@ class BasicApprover(Approver):
"Original transactions must have same effective nLockTime as replacement transaction."
)
if self.external_in > self.orig_external_in:
description = "PayJoin"
elif tx_info.rbf_disabled() and any(
not orig.rbf_disabled() for orig in orig_txs
):
description = "Finalize transaction"
elif len(orig_txs) > 1:
description = "Transaction meld"
else:
description = "Fee modification"
for orig in orig_txs:
await helpers.confirm_replacement(description, orig.orig_hash)
# Always ask the user to confirm when they are paying more towards the fee.
# If they are not spending more, then ask for confirmation only if it's not
# a PayJoin. In complex scenarios where the user is not spending more and
# there are new external inputs the scenario can be open to multiple
# interpretations and the dialog would likely cause more confusion than
# what it's worth, see PR #1292.
if spending > orig_spending or self.external_in == self.orig_external_in:
if not self.is_payjoin():
# Not a PayJoin: Show the actual fee difference, since any difference in the fee is
# coming entirely from the user's own funds and from decreases of external outputs.
# We consider the decreases as belonging to the user.
await helpers.confirm_modify_fee(
fee - orig_fee, fee, self.coin, self.amount_unit
)
elif spending > orig_spending:
# PayJoin and user is spending more: Show the increase in the user's contribution
# to the fee, ignoring any contribution from external inputs. Decreasing of
# external outputs is not allowed in PayJoin, so there is no need to handle those.
await helpers.confirm_modify_fee(
spending - orig_spending, fee, self.coin, self.amount_unit
)
else:
# PayJoin and user is not spending more: When new external inputs are involved and
# the user is paying less, the scenario can be open to multiple interpretations and
# the dialog would likely cause more confusion than what it's worth, see PR #1292.
pass
else:
# Standard transaction.
if tx_info.tx.lock_time > 0:
@ -263,6 +306,11 @@ class CoinJoinApprover(Approver):
await super().add_external_output(txo, script_pubkey, orig_txo)
self._add_output(txo, script_pubkey)
async def approve_orig_txids(
self, tx_info: TxInfo, orig_txs: List[OriginalTxInfo]
) -> None:
pass
async def approve_tx(self, tx_info: TxInfo, orig_txs: List[OriginalTxInfo]) -> None:
# The mining fee of the transaction as a whole.
mining_fee = self.total_in - self.total_out

3
core/src/apps/bitcoin/sign_tx/bitcoin.py
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@ -44,6 +44,9 @@ class Bitcoin:
# Add inputs to hash143 and h_tx_check and compute the sum of input amounts.
await self.step1_process_inputs()
# Approve the original TXIDs in case of a replacement transaction.
await self.approver.approve_orig_txids(self.tx_info, self.orig_txs)
# Add outputs to hash143 and h_tx_check, approve outputs and compute
# sum of output amounts.
await self.step2_approve_outputs()

25
core/src/apps/bitcoin/sign_tx/helpers.py
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@ -85,6 +85,27 @@ class UiConfirmReplacement(UiConfirm):
__eq__ = utils.obj_eq
class UiConfirmModifyOutput(UiConfirm):
def __init__(
self,
txo: TxOutput,
orig_txo: TxOutput,
coin: CoinInfo,
amount_unit: EnumTypeAmountUnit,
):
self.txo = txo
self.orig_txo = orig_txo
self.coin = coin
self.amount_unit = amount_unit
def confirm_dialog(self, ctx: wire.Context) -> Awaitable[Any]:
return layout.confirm_modify_output(
ctx, self.txo, self.orig_txo, self.coin, self.amount_unit
)
__eq__ = utils.obj_eq
class UiConfirmModifyFee(UiConfirm):
def __init__(
self,
@ -199,6 +220,10 @@ def confirm_replacement(description: str, txid: bytes) -> Awaitable[Any]: # typ
return (yield UiConfirmReplacement(description, txid))
def confirm_modify_output(txo: TxOutput, orig_txo: TxOutput, coin: CoinInfo, amount_unit: EnumTypeAmountUnit) -> Awaitable[Any]: # type: ignore
return (yield UiConfirmModifyOutput(txo, orig_txo, coin, amount_unit))
def confirm_modify_fee(user_fee_change: int, total_fee_new: int, coin: CoinInfo, amount_unit: EnumTypeAmountUnit) -> Awaitable[Any]: # type: ignore
return (yield UiConfirmModifyFee(user_fee_change, total_fee_new, coin, amount_unit))

21
core/src/apps/bitcoin/sign_tx/layout.py
View File

@ -96,6 +96,27 @@ async def confirm_replacement(ctx: wire.Context, description: str, txid: bytes)
)
async def confirm_modify_output(
ctx: wire.Context,
txo: TxOutput,
orig_txo: TxOutput,
coin: CoinInfo,
amount_unit: EnumTypeAmountUnit,
) -> None:
assert txo.address is not None
address_short = addresses.address_short(coin, txo.address)
amount_change = txo.amount - orig_txo.amount
await require(
layouts.confirm_modify_output(
ctx,
address_short,
amount_change,
format_coin_amount(abs(amount_change), coin, amount_unit),
format_coin_amount(txo.amount, coin, amount_unit),
)
)
async def confirm_modify_fee(
ctx: wire.Context,
user_fee_change: int,

33
core/src/trezor/ui/layouts/tt.py
View File

@ -50,6 +50,7 @@ __all__ = (
"confirm_joint_total",
"confirm_metadata",
"confirm_replacement",
"confirm_modify_output",
"confirm_modify_fee",
)
@ -407,13 +408,43 @@ def confirm_replacement(
return interact(ctx, Confirm(text), "confirm_replacement", ButtonRequestType.SignTx)
def confirm_modify_output(
ctx: wire.GenericContext,
address: str,
sign: int,
amount_change: str,
amount_new: str,
) -> LayoutType:
page1 = Text("Modify amount", ui.ICON_SEND, ui.GREEN)
page1.normal("Address:")
page1.br_half()
page1.mono(*_split_address(address))
page2 = Text("Modify amount", ui.ICON_SEND, ui.GREEN)
if sign < 0:
page2.normal("Decrease amount by:")
else:
page2.normal("Increase amount by:")
page2.bold(amount_change)
page2.br_half()
page2.normal("New amount:")
page2.bold(amount_new)
return interact(
ctx,
Paginated([page1, Confirm(page2)]),
"modify_output",
ButtonRequestType.ConfirmOutput,
)
def confirm_modify_fee(
ctx: wire.GenericContext,
sign: int,
user_fee_change: str,
total_fee_new: str,
) -> LayoutType:
text = Text("Fee modification", ui.ICON_SEND, ui.GREEN)
text = Text("Modify fee", ui.ICON_SEND, ui.GREEN)
if sign == 0:
text.normal("Your fee did not change.")
else: