The PWNSignatureChecker library implements the isValidSignatureNow view function. This library is a modification of the Open-Zeppelin library extended by support for compact signatures.
2. Important links
3. Contract details
PWNSignatureChecker.sol is written in Solidity version 0.8.16
isValidSignatureNow
Overview
This function takes three arguments supplied by the caller:
addresssigner - Address that should be a hash signer or a signature validator, in case of a contract account.
bytes32hash - Hash of a signed message that should be validated.
Implementation
function isValidSignatureNow(
address signer,
bytes32 hash,
bytes memory signature
) internal view returns (bool) {
// Check that signature is valid for contract account
if (signer.code.length > 0) {
(bool success, bytes memory result) = signer.staticcall(
abi.encodeWithSelector(IERC1271.isValidSignature.selector, hash, signature)
);
return
success &&
result.length == 32 &&
abi.decode(result, (bytes32)) == bytes32(IERC1271.isValidSignature.selector);
}
// Check that signature is valid for EOA
else {
bytes32 r;
bytes32 s;
uint8 v;
// Standard signature data (65 bytes)
if (signature.length == 65) {
assembly {
r := mload(add(signature, 0x20))
s := mload(add(signature, 0x40))
v := byte(0, mload(add(signature, 0x60)))
}
}
// Compact signature data (64 bytes) - see EIP-2098
else if (signature.length == 64) {
bytes32 vs;
assembly {
r := mload(add(signature, 0x20))
vs := mload(add(signature, 0x40))
}
s = vs & bytes32(0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
v = uint8((uint256(vs) >> 255) + 27);
} else {
revert InvalidSignatureLength({ length: signature.length });
}
return signer == ECDSA.recover(hash, v, r, s);
}
}
InvalidSignatureLength event is emitted when signature length is not 64 nor 65 bytes.
This event has one parameter:
uint256length
InvalidSignature
InvalidSignatureLength event is emitted when the signature is invalid.
This event has one parameter:
addresssigner
bytes32digest - hash to distinguish different proposals
This function will try to recover a signer of a given signature and check if is the same as the given signer address. For a contract account signer address, the function will check signature validity by calling isValidSignature function defined by .
bytes memorysignature - Signature of a signed hash. Can be empty for a contract account signature validation. The signature can be standard (65 bytes) or compact (64 bytes) defined by .
