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Fix double spend via delegatecall #177

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Fix double spend via delegatecall #177

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6 changes: 4 additions & 2 deletions src/EIP712.sol
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Expand Up @@ -2,27 +2,29 @@
pragma solidity 0.8.17;

/// @notice EIP712 helpers for permit2
/// @dev Maintains cross-chain replay protection in the event of a fork
/// @dev Maintains cross-chain replay protection in the event of a fork and properly handles delegated calls
/// @dev Reference: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/cryptography/EIP712.sol
contract EIP712 {
// Cache the domain separator as an immutable value, but also store the chain id that it
// corresponds to, in order to invalidate the cached domain separator if the chain id changes.
bytes32 private immutable _CACHED_DOMAIN_SEPARATOR;
uint256 private immutable _CACHED_CHAIN_ID;
address private immutable _CACHED_THIS;

bytes32 private constant _HASHED_NAME = keccak256("Permit2");
bytes32 private constant _TYPE_HASH =
keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");

constructor() {
_CACHED_THIS = address(this);
_CACHED_CHAIN_ID = block.chainid;
_CACHED_DOMAIN_SEPARATOR = _buildDomainSeparator(_TYPE_HASH, _HASHED_NAME);
}

/// @notice Returns the domain separator for the current chain.
/// @dev Uses cached version if chainid and address are unchanged from construction.
function DOMAIN_SEPARATOR() public view returns (bytes32) {
return block.chainid == _CACHED_CHAIN_ID
return block.chainid == _CACHED_CHAIN_ID && address(this) == _CACHED_THIS
? _CACHED_DOMAIN_SEPARATOR
: _buildDomainSeparator(_TYPE_HASH, _HASHED_NAME);
}
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