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trezor-firmware/tests/device_tests/bitcoin/test_signtx_prevhash.py

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from copy import copy
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from hashlib import sha256
from io import BytesIO
import pytest
from trezorlib import btc, messages, models, tools
from trezorlib.debuglink import TrezorClientDebugLink as Client
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from trezorlib.exceptions import TrezorFailure
from ...common import is_core
from ...input_flows import InputFlowConfirmAllWarnings
from .signtx import forge_prevtx
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# address at seed "all all all..." path m/44h/0h/0h/0/0
INPUT_ADDRESS = "1JAd7XCBzGudGpJQSDSfpmJhiygtLQWaGL"
PREV_HASH, PREV_TX = forge_prevtx([(INPUT_ADDRESS, 100_000_000)])
PREV_TXES = {PREV_HASH: PREV_TX}
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def write_prefixed_bytes(io, data) -> None:
assert len(data) < 253
io.write(len(data).to_bytes(1, "little"))
io.write(data)
def serialize_input(tx_input) -> bytes:
"""serialize for Bitcoin tx format"""
b = BytesIO()
if tx_input.prev_hash:
b.write(tx_input.prev_hash[::-1])
b.write(tx_input.prev_index.to_bytes(4, "little"))
write_prefixed_bytes(b, tx_input.script_sig)
b.write(tx_input.sequence.to_bytes(4, "little"))
return b.getvalue()
def serialize_bin_output(tx_output) -> bytes:
b = BytesIO()
b.write(tx_output.amount.to_bytes(8, "little"))
write_prefixed_bytes(b, tx_output.script_pubkey)
return b.getvalue()
def serialize_tx(tx) -> bytes:
b = BytesIO()
b.write(tx.version.to_bytes(4, "little"))
assert len(tx.inputs) < 253
b.write(len(tx.inputs).to_bytes(1, "little"))
for inp in tx.inputs:
b.write(serialize_input(inp))
assert len(tx.bin_outputs) < 253
b.write(len(tx.bin_outputs).to_bytes(1, "little"))
for outp in tx.bin_outputs:
b.write(serialize_bin_output(outp))
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lock_time = tx.lock_time or 0
b.write(lock_time.to_bytes(4, "little"))
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if tx.extra_data:
b.write(tx.extra_data)
return b.getvalue()
def hash_tx(data: bytes) -> bytes:
return sha256(sha256(data).digest()).digest()[::-1]
def _check_error_message(value: bytes, model: models.TrezorModel, message: str):
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# T1 has several possible errors
if model is models.T1B1 and len(value) > 32:
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assert message.endswith("bytes overflow")
else:
assert message.endswith("Provided prev_hash is invalid.")
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with_bad_prevhashes = pytest.mark.parametrize(
"prev_hash", (b"", b"x", b"hello world", b"x" * 33)
)
@with_bad_prevhashes
def test_invalid_prev_hash(client: Client, prev_hash):
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inp1 = messages.TxInputType(
address_n=tools.parse_path("m/44h/0h/0h/0/0"),
amount=123_456_789,
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prev_hash=prev_hash,
prev_index=0,
script_type=messages.InputScriptType.SPENDP2SHWITNESS,
)
out1 = messages.TxOutputType(
address="mhRx1CeVfaayqRwq5zgRQmD7W5aWBfD5mC",
amount=12_300_000,
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script_type=messages.OutputScriptType.PAYTOADDRESS,
)
with pytest.raises(TrezorFailure) as e:
btc.sign_tx(client, "Testnet", [inp1], [out1], prev_txes={})
_check_error_message(prev_hash, client.model, e.value.message)
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@with_bad_prevhashes
def test_invalid_prev_hash_attack(client: Client, prev_hash):
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# prepare input with a valid prev-hash
inp1 = messages.TxInputType(
address_n=tools.parse_path("m/44h/0h/0h/0/0"),
amount=100_000_000,
prev_hash=PREV_HASH,
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prev_index=0,
script_type=messages.InputScriptType.SPENDP2SHWITNESS,
)
out1 = messages.TxOutputType(
address="1MJ2tj2ThBE62zXbBYA5ZaN3fdve5CPAz1",
amount=100_000_000 - 10_000,
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script_type=messages.OutputScriptType.PAYTOADDRESS,
)
counter = 1
def attack_filter(msg):
nonlocal counter
if not msg.tx.inputs:
return msg
# on first attempt, send unmodified input
if counter > 0:
counter -= 1
return msg
# on second request, send modified input
msg.tx.inputs[0].prev_hash = prev_hash
return msg
with client, pytest.raises(TrezorFailure) as e:
client.set_filter(messages.TxAck, attack_filter)
if is_core(client):
IF = InputFlowConfirmAllWarnings(client)
client.set_input_flow(IF.get())
btc.sign_tx(client, "Bitcoin", [inp1], [out1], prev_txes=PREV_TXES)
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# check that injection was performed
assert counter == 0
_check_error_message(prev_hash, client.model, e.value.message)
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@with_bad_prevhashes
def test_invalid_prev_hash_in_prevtx(client: Client, prev_hash):
prev_tx = copy(PREV_TX)
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# smoke check: replace prev_hash with all zeros, reserialize and hash, try to sign
prev_tx.inputs[0].prev_hash = b"\x00" * 32
tx_hash = hash_tx(serialize_tx(prev_tx))
inp0 = messages.TxInputType(
address_n=tools.parse_path("m/44h/0h/0h/0/0"),
amount=100_000_000,
prev_hash=tx_hash,
prev_index=0,
)
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out1 = messages.TxOutputType(
address="1MJ2tj2ThBE62zXbBYA5ZaN3fdve5CPAz1",
amount=99_000_000,
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script_type=messages.OutputScriptType.PAYTOADDRESS,
)
btc.sign_tx(client, "Bitcoin", [inp0], [out1], prev_txes={tx_hash: prev_tx})
# attack: replace prev_hash with an invalid value
prev_tx.inputs[0].prev_hash = prev_hash
tx_hash = hash_tx(serialize_tx(prev_tx))
inp0.prev_hash = tx_hash
with client, pytest.raises(TrezorFailure) as e:
if client.model is not models.T1B1:
IF = InputFlowConfirmAllWarnings(client)
client.set_input_flow(IF.get())
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btc.sign_tx(client, "Bitcoin", [inp0], [out1], prev_txes={tx_hash: prev_tx})
_check_error_message(prev_hash, client.model, e.value.message)