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refactor(core): Use a list of presigned inputs in Bitcoin signing.

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Co-authored-by: Ondřej Vejpustek <ondrej.vejpustek@satoshilabs.com>
pull/2552/merge
Andrew Kozlik 2 years ago committed by Andrew Kozlik
parent 5dddb06e2b
commit ee8c596b1a
3 changed files with 43 additions and 37 deletions
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65
core/src/apps/bitcoin/sign_tx/bitcoin.py
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@ -69,8 +69,8 @@ class Bitcoin:
progress.init_signing(
len(self.external),
len(self.segwit),
len(self.presigned),
self.taproot_only,
self.has_presigned,
self.serialize,
self.coin,
self.tx_info.tx,
@ -118,12 +118,12 @@ class Bitcoin:
# set of indices of inputs which are external
self.external: set[int] = set()
# set of indices of inputs which are presigned
self.presigned: set[int] = set()
# indicates whether all internal inputs are Taproot
self.taproot_only = True
# indicates whether any external inputs are presigned
self.has_presigned = False
# transaction and signature serialization
_SERIALIZED_TX_BUFFER[:] = bytes()
self.serialized_tx = _SERIALIZED_TX_BUFFER
@ -139,10 +139,10 @@ class Bitcoin:
# stable device tests.
self.orig_txs: list[OriginalTxInfo] = []
# The digests of the external inputs streamed for approval in Step 1. These are used
# to ensure that the inputs streamed for verification in Step 3 are the same as
# The digest of the presigned external inputs streamed for approval in Step 1. This is
# used to ensure that the inputs streamed for verification in Step 3 are the same as
# those in Step 1.
self.h_external_inputs: bytes | None = None
self.h_presigned_inputs: bytes | None = None
# The index of the payment request being processed.
self.payment_req_index: int | None = None
@ -154,7 +154,7 @@ class Bitcoin:
return BitcoinSigHasher()
async def step1_process_inputs(self) -> None:
h_external_inputs_check = HashWriter(sha256())
h_presigned_inputs_check = HashWriter(sha256())
for i in range(self.tx_info.tx.inputs_count):
# STAGE_REQUEST_1_INPUT in legacy
@ -173,7 +173,9 @@ class Bitcoin:
if input_is_external(txi):
self.external.add(i)
writers.write_tx_input_check(h_external_inputs_check, txi)
if txi.witness or txi.script_sig:
self.presigned.add(i)
writers.write_tx_input_check(h_presigned_inputs_check, txi)
await self.process_external_input(txi, script_pubkey)
else:
await self.process_internal_input(txi)
@ -182,7 +184,7 @@ class Bitcoin:
await self.process_original_input(txi, script_pubkey)
self.tx_info.h_inputs_check = self.tx_info.get_tx_check_digest()
self.h_external_inputs = h_external_inputs_check.get_digest()
self.h_presigned_inputs = h_presigned_inputs_check.get_digest()
# Finalize original inputs.
for orig in self.orig_txs:
@ -214,25 +216,23 @@ class Bitcoin:
async def step3_verify_inputs(self) -> None:
# should come out the same as h_inputs_check, checked before continuing
h_check = HashWriter(sha256())
expected_digest = None
if self.taproot_only:
# All internal inputs are Taproot. We only need to verify presigned external inputs.
# We can trust the amounts and scriptPubKeys, because if an invalid value is provided
# then all issued signatures will be invalid.
if self.has_presigned:
expected_digest = self.h_external_inputs
for i in range(self.tx_info.tx.inputs_count):
if i in self.external:
progress.advance()
txi = await helpers.request_tx_input(self.tx_req, i, self.coin)
writers.write_tx_input_check(h_check, txi)
if txi.witness or txi.script_sig:
# txi.script_pubkey checked in sanitize_tx_input
assert txi.script_pubkey is not None
await self.verify_presigned_external_input(
i, txi, txi.script_pubkey
)
expected_digest = self.h_presigned_inputs
for i in range(self.tx_info.tx.inputs_count):
if i in self.presigned:
progress.advance()
txi = await helpers.request_tx_input(self.tx_req, i, self.coin)
writers.write_tx_input_check(h_check, txi)
# txi.script_pubkey checked in sanitize_tx_input
assert txi.script_pubkey is not None
await self.verify_presigned_external_input(
i, txi, txi.script_pubkey
)
else:
# There are internal non-Taproot inputs. We need to verify all inputs, because we can't
# trust any amounts or scriptPubKeys. If we did, then an attacker who provides invalid
@ -256,11 +256,11 @@ class Bitcoin:
if script_pubkey != self.input_derive_script(txi):
raise wire.DataError("Input does not match scriptPubKey")
if i in self.external and (txi.witness or txi.script_sig):
if i in self.presigned:
await self.verify_presigned_external_input(i, txi, script_pubkey)
# check that the inputs were the same as those streamed for approval
if expected_digest and h_check.get_digest() != expected_digest:
if h_check.get_digest() != expected_digest:
raise wire.ProcessError("Transaction has changed during signing")
# verify the signature of one SIGHASH_ALL input in each original transaction
@ -301,9 +301,14 @@ class Bitcoin:
if i in self.segwit:
if i in self.external:
if self.serialize:
progress.advance()
txi = await helpers.request_tx_input(self.tx_req, i, self.coin)
self.serialized_tx.extend(txi.witness or b"\0")
if i in self.presigned:
progress.advance()
txi = await helpers.request_tx_input(
self.tx_req, i, self.coin
)
self.serialized_tx.extend(txi.witness or b"\0")
else:
self.serialized_tx.append(0)
else:
progress.advance()
await self.sign_segwit_input(i)
@ -327,8 +332,6 @@ class Bitcoin:
async def process_external_input(self, txi: TxInput, script_pubkey: bytes) -> None:
self.approver.add_external_input(txi)
if txi.witness or txi.script_sig:
self.has_presigned = True
if txi.ownership_proof:
if not verify_nonownership(

13
core/src/apps/bitcoin/sign_tx/progress.py
Unescape View File

@ -40,8 +40,8 @@ class Progress:
self,
external: int,
segwit: int,
presigned: int,
taproot_only: bool,
has_presigned: bool,
serialize: bool,
coin: CoinInfo,
tx: SignTx,
@ -56,8 +56,7 @@ class Progress:
# Step 3 - verify inputs
if taproot_only or (coin.overwintered and tx.version == 5):
if has_presigned:
self.steps += external
self.steps += presigned
else:
self.steps = tx.inputs_count * _PREV_TX_MULTIPLIER
@ -82,8 +81,14 @@ class Progress:
# Steps 4 and 6 - serialize and sign inputs
if serialize:
self.steps += tx.inputs_count + segwit
# Step 4 - serialize all inputs.
self.steps += tx.inputs_count
# Step 6 - serialize witnesses for all segwit inputs except for the
# external ones that are not presigned.
self.steps += segwit - (external - presigned)
else:
# Add the number of inputs to be signed.
self.steps += tx.inputs_count - external
# Step 5 - serialize outputs

2
tests/device_tests/bitcoin/test_signtx_external.py
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@ -624,7 +624,6 @@ def test_p2wpkh_with_proof(client: Client):
request_input(1),
request_output(0),
request_output(1),
request_input(0),
request_input(1),
request_finished(),
]
@ -702,7 +701,6 @@ def test_p2tr_with_proof(client: Client):
request_input(0),
request_input(1),
request_output(0),
request_input(0),
request_input(1),
request_finished(),
]

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