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Validate contract signatures against the verifying Safe's EIP-1271 convention #2726

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Validate contract signatures against the verifying Safe's EIP-1271 convention #2726

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a4a7e52
Validate contract signatures against the verifying Safe's EIP-1271 co…
Uxio0 Sep 2, 2026
f85e4eb
Require the magic value the verifying Safe expects for each entrypoint
Uxio0 Sep 2, 2026
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165 changes: 121 additions & 44 deletions safe_eth/safe/safe_signature.py
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
from eth_account.messages import defunct_hash_message
from eth_typing import BlockIdentifier, ChecksumAddress, HexAddress, HexStr
from hexbytes import HexBytes
from packaging.version import InvalidVersion, Version
from typing_extensions import Self
from web3 import AsyncWeb3, Web3
from web3.contract import Contract
Expand Down Expand Up @@ -337,10 +338,14 @@ def is_valid(
self,
ethereum_client: Optional[EthereumClient] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
"""
:param ethereum_client: Required for Contract Signature and Approved Hash check
:param safe_address: Required for Approved Hash check
:param safe_version: Version of the Safe that will verify this signature. Required for
a correct Contract Signature check, as the version decides which EIP-1271 entrypoint
is called on-chain. Ignored by every other signature type.
:return: `True` if signature is valid, `False` otherwise
"""
raise NotImplementedError
Expand All @@ -352,10 +357,48 @@ async def is_valid(
self,
web3: Optional[AsyncWeb3] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
"""
:param web3: Required for Contract Signature and Approved Hash check
:param safe_address: Required for Approved Hash check
:param safe_version: Version of the Safe that will verify this signature. Required for
a correct Contract Signature check, as the version decides which EIP-1271 entrypoint
is called on-chain. Ignored by every other signature type.
:return: `True` if signature is valid, `False` otherwise
"""
raise NotImplementedError


# From this version a Safe verifies contract signatures through
# `isValidSignature(bytes32,bytes)`; below it, through the legacy
# `isValidSignature(bytes,bytes)`.
EIP1271_BYTES32_MIN_VERSION = Version("1.5.0")


def uses_bytes32_eip1271(safe_version: str) -> bool:
"""Whether a Safe of `safe_version` verifies contract signatures with the hash.

The single home for the rule: `checkContractSignature` on a Safe >= 1.5.0 calls
`isValidSignature(bytes32,bytes)` with `dataHash`, while `checkNSignatures` below that
calls the legacy `isValidSignature(bytes,bytes)` with the whole preimage. Callers that
report a rejection need the same answer to name the entrypoint, so they should ask here
rather than compare against `EIP1271_BYTES32_MIN_VERSION` themselves.

:param safe_version: Version of the Safe that verifies the signature.
:return: `True` from 1.5.0 on, `False` below.
:raises CannotCheckEIP1271ContractSignature: If `safe_version` cannot be compared. Raised
instead of `packaging`'s `InvalidVersion` so callers handle one Safe-domain error and
do not each reimplement the translation. `VERSION()` is an arbitrary on-chain string.
"""
try:
return Version(safe_version) >= EIP1271_BYTES32_MIN_VERSION
except InvalidVersion as exc:
raise CannotCheckEIP1271ContractSignature(
f"Cannot tell which EIP-1271 entrypoint Safe version {safe_version!r} uses"
) from exc


class SafeSignatureContractMixin(SafeSignatureBase):
EIP1271_MAGIC_VALUE = HexBytes(0x20C13B0B)
EIP1271_MAGIC_VALUE_UPDATED = HexBytes(0x1626BA7E)
Expand Down Expand Up @@ -614,40 +657,53 @@ def is_valid(
self,
ethereum_client: Optional[EthereumClient] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
"""
Validate the signature using the appropriate EIP-1271 path.
First tries the updated method (bytes32,bytes).
Falls back to the legacy method (bytes,bytes).
Validate the signature through the EIP-1271 entrypoint the verifying Safe uses.

:param ethereum_client: EthereumClient instance
:param safe_address: Optional Safe EthereumAddress instance.
:param safe_version: Version of the Safe that will verify this signature. Only the
entrypoint that version calls on-chain is checked. Defaults to `None`, which checks
both and so can return `True` for a signature that reverts `GS024` on that Safe;
pass a version whenever it is known.
:raises CannotCheckEIP1271ContractSignature: If `safe_version` cannot be compared.
"""
if ethereum_client is None:
raise ValueError(
"ethereum_client is required to validate contract signature"
)

for fallback_handler_getter, function_signature, data in (
(
get_compatibility_fallback_handler_contract,
"isValidSignature(bytes32,bytes)",
bytes(self.safe_hash),
),
(
get_compatibility_fallback_handler_V1_4_1_contract,
"isValidSignature(bytes,bytes)",
bytes(self.safe_hash_preimage),
),
# Only one entrypoint is ever called on-chain and the verifying Safe's version
# decides which: `checkContractSignature` on a Safe >= 1.5.0 hands `dataHash` to the
# signer, while `checkNSignatures` below that hands over the whole preimage. `None`
# means the caller does not know, so both are tried.
if safe_version is None:
try_bytes32 = try_legacy = True
else:
try_bytes32 = uses_bytes32_eip1271(safe_version)
try_legacy = not try_bytes32

if try_bytes32 and self._check_eip1271(
ethereum_client,
get_compatibility_fallback_handler_contract,
"isValidSignature(bytes32,bytes)",
bytes(self.safe_hash),
bytes(self.contract_signature),
):
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Uxio0 marked this conversation as resolved.
if self._check_eip1271(
ethereum_client,
fallback_handler_getter,
function_signature,
data,
bytes(self.contract_signature),
):
return True
return True

# Dropped from the 1.5.0 `CompatibilityFallbackHandler`, so a 1.5.0 signer does not
# declare this overload at all and can never answer here
if try_legacy and self._check_eip1271(
ethereum_client,
get_compatibility_fallback_handler_V1_4_1_contract,
"isValidSignature(bytes,bytes)",
bytes(self.safe_hash_preimage),
bytes(self.contract_signature),
):
return True

return False

Expand All @@ -657,6 +713,7 @@ def is_valid(
self,
ethereum_client: Optional[EthereumClient] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
if ethereum_client is None:
raise ValueError("ethereum_client is required to validate approved hash")
Expand Down Expand Up @@ -689,6 +746,7 @@ def is_valid(
self,
ethereum_client: Optional[EthereumClient] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
return True

Expand All @@ -698,6 +756,7 @@ def is_valid(
self,
ethereum_client: Optional[EthereumClient] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
return True

Expand All @@ -707,6 +766,7 @@ def is_valid(
self,
ethereum_client: Optional[EthereumClient] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
return self._is_valid()

Expand Down Expand Up @@ -757,38 +817,51 @@ async def is_valid(
self,
web3: Optional[AsyncWeb3] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
"""
Validate the signature using the appropriate EIP-1271 path.
First tries the updated method (bytes32,bytes).
Falls back to the legacy method (bytes,bytes).
Validate the signature through the EIP-1271 entrypoint the verifying Safe uses.

:param web3: Optional EthereumClient instance.
:param safe_address: Optional Safe EthereumAddress instance.
:param safe_version: Version of the Safe that will verify this signature. Only the
entrypoint that version calls on-chain is checked. Defaults to `None`, which checks
both and so can return `True` for a signature that reverts `GS024` on that Safe;
pass a version whenever it is known.
:raises CannotCheckEIP1271ContractSignature: If `safe_version` cannot be compared.
"""
if web3 is None:
raise ValueError("web3 is required to validate contract signature")

for fallback_handler_getter, function_signature, data in (
(
get_compatibility_fallback_handler_contract,
"isValidSignature(bytes32,bytes)",
bytes(self.safe_hash),
),
(
get_compatibility_fallback_handler_V1_4_1_contract,
"isValidSignature(bytes,bytes)",
bytes(self.safe_hash_preimage),
),
# Only one entrypoint is ever called on-chain and the verifying Safe's version
# decides which: `checkContractSignature` on a Safe >= 1.5.0 hands `dataHash` to the
# signer, while `checkNSignatures` below that hands over the whole preimage. `None`
# means the caller does not know, so both are tried.
if safe_version is None:
try_bytes32 = try_legacy = True
else:
try_bytes32 = uses_bytes32_eip1271(safe_version)
try_legacy = not try_bytes32

if try_bytes32 and await self._check_eip1271(
web3,
get_compatibility_fallback_handler_contract,
"isValidSignature(bytes32,bytes)",
bytes(self.safe_hash),
bytes(self.contract_signature),
):
if await self._check_eip1271(
web3,
fallback_handler_getter,
function_signature,
data,
bytes(self.contract_signature),
):
return True
return True

# Dropped from the 1.5.0 `CompatibilityFallbackHandler`, so a 1.5.0 signer does not
# declare this overload at all and can never answer here
if try_legacy and await self._check_eip1271(
web3,
get_compatibility_fallback_handler_V1_4_1_contract,
"isValidSignature(bytes,bytes)",
bytes(self.safe_hash_preimage),
bytes(self.contract_signature),
):
return True

return False

Expand All @@ -800,6 +873,7 @@ async def is_valid(
self,
web3: Optional[AsyncWeb3] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
if web3 is None:
raise ValueError("web3 is required to validate approved hash")
Expand Down Expand Up @@ -830,6 +904,7 @@ async def is_valid(
self,
web3: Optional[AsyncWeb3] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
return True

Expand All @@ -839,6 +914,7 @@ async def is_valid(
self,
web3: Optional[AsyncWeb3] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
return True

Expand All @@ -848,6 +924,7 @@ async def is_valid(
self,
web3: Optional[AsyncWeb3] = None,
safe_address: Optional[str] = None,
safe_version: Optional[str] = None,
) -> bool:
return self._is_valid()

Expand Down
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