What the developer wrote
Authored by Roman Zeyde
chore(core): prefix constants with `_`
It allows MicroPython to inline the constants and avoid allocations[^1].
[^1]: https://docs.micropython.org/en/latest/reference/speed_python.html#the-const-declaration
[no changelog]
What changed, and why it matters
This is a routine code cleanup change in the Trezor firmware's Ethereum transaction signing module. It renames several internal constants to start with an underscore and wraps them with MicroPython's `const()` helper so the interpreter can optimize them. The numeric values and program logic are unchanged. There is no security fix or vulnerability here.
No security action needed. Treat as a normal refactoring/performance change.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The commit modifies core/src/apps/ethereum/sign_tx.py to prefix module-level constants (MAX_CHAIN_ID, EIP_7702_TX_TYPE, MAX_DATA_STORED, DATA_CHUNK_SIZE) with an underscore and apply const() where missing. The diff shows only identifier renames and the addition of const(...); all arithmetic, comparisons, control flow, and return values remain identical. This is a MicroPython performance idiom to allow the compiler to inline integer constants and avoid dictionary lookups/allocations.
Changed components
core/src/apps/ethereum/sign_tx.pyInspect captured patch +12 / −12
diff --git a/core/src/apps/ethereum/sign_tx.py b/core/src/apps/ethereum/sign_tx.py
index 151cc76d..39811a78 100644
--- a/core/src/apps/ethereum/sign_tx.py
+++ b/core/src/apps/ethereum/sign_tx.py
@@ -34,11 +34,11 @@ if TYPE_CHECKING:
# Maximum chain_id which returns the full signature_v (which must fit into an uint32).
# chain_ids larger than this will only return one bit and the caller must recalculate
# the full value: v = 2 * chain_id + 35 + v_bit
-MAX_CHAIN_ID = (0xFFFF_FFFF - 36) // 2
+_MAX_CHAIN_ID = const(0xFFFF_FFFF - 36) // 2
# EIP-7702
-EIP_7702_TX_TYPE = const(4)
+_EIP_7702_TX_TYPE = const(4)
EIP_7702_KNOWN_ADDRESSES = {
unhexlify("000000009B1D0aF20D8C6d0A44e162d11F9b8f00"): "Uniswap",
unhexlify("69007702764179f14F51cdce752f4f775d74E139"): "alchemyplatform",
@@ -74,10 +74,10 @@ async def sign_tx(
address_bytes = bytes_from_address(msg.to)
- valid_tx_types = (1, 6, EIP_7702_TX_TYPE, None)
+ valid_tx_types = (1, 6, _EIP_7702_TX_TYPE, None)
if tx_type not in valid_tx_types:
raise DataError("tx_type out of bounds")
- if tx_type == EIP_7702_TX_TYPE:
+ if tx_type == _EIP_7702_TX_TYPE:
if safety_checks.is_strict():
raise DataError("EIP-7702 not allowed in strict checks")
if address_bytes not in EIP_7702_KNOWN_ADDRESSES:
@@ -162,8 +162,8 @@ async def sign_tx(
return result
-MAX_DATA_STORED = const(4096)
-DATA_CHUNK_SIZE = const(1024)
+_MAX_DATA_STORED = const(4096)
+_DATA_CHUNK_SIZE = const(1024)
async def request_initial_data(msg: MsgInSignTx, sha: HashWriter) -> AnyBytes:
@@ -172,7 +172,7 @@ async def request_initial_data(msg: MsgInSignTx, sha: HashWriter) -> AnyBytes:
data_length = msg.data_length
if data_length > len(msg.data_initial_chunk):
# pre-allocate memory
- initial_data = bytearray(min(data_length, MAX_DATA_STORED))
+ initial_data = bytearray(min(data_length, _MAX_DATA_STORED))
chunk = msg.data_initial_chunk
initial_data[0 : len(chunk)] = chunk
@@ -181,7 +181,7 @@ async def request_initial_data(msg: MsgInSignTx, sha: HashWriter) -> AnyBytes:
sha.extend(chunk)
data_left = data_length - initial_data_length
while (
- data_left > 0 and initial_data_length + DATA_CHUNK_SIZE <= MAX_DATA_STORED
+ data_left > 0 and initial_data_length + _DATA_CHUNK_SIZE <= _MAX_DATA_STORED
):
resp = await send_request_chunk(data_left)
chunk = resp.data_chunk
@@ -233,7 +233,7 @@ async def confirm_tx_data(
raise DataError("Payment Requests don't support staking")
return staking_approver
- if tx_type == EIP_7702_TX_TYPE:
+ if tx_type == _EIP_7702_TX_TYPE:
# we have already made sure that the address is a known address
# as part of the initial validation
await confirm_value(
@@ -299,7 +299,7 @@ async def confirm_tx_data(
maximum_fee,
fee_items,
token,
- is_send=(data_length == 0 and tx_type != EIP_7702_TX_TYPE),
+ is_send=(data_length == 0 and tx_type != _EIP_7702_TX_TYPE),
chunkify=bool(msg.chunkify),
)
else:
@@ -336,7 +336,7 @@ async def send_request_chunk(data_left: int) -> EthereumTxAck:
from trezor.wire.context import call
req = EthereumTxRequest()
- req.data_length = min(data_left, DATA_CHUNK_SIZE)
+ req.data_length = min(data_left, _DATA_CHUNK_SIZE)
return await call(req, EthereumTxAck)
@@ -352,7 +352,7 @@ def _sign_digest(
req = EthereumTxRequest()
req.signature_v = signature[0]
- if msg.chain_id > MAX_CHAIN_ID:
+ if msg.chain_id > _MAX_CHAIN_ID:
req.signature_v -= 27
else:
req.signature_v += 2 * msg.chain_id + 8
Why this scored 15/100
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