Since Wildcredit's ERC20 implementation uses the Solidity 0.8 compiler, all math operations are checked against over/underflow by default. However, some of these checks are unnecessary due to pre-checks. Wildcredit can selectively disable these over/underflow checks using the unchecked{} construct.
Proof of Concept
There are 3 lines where use of checked math is unnecessary:
The sum of all balances in the ERC20 will never exceed type(uint256).max, as totalSupply is safely incremented in _mint when creating new tokens. If _mint was ever called with a value that would increase the sum of all balances beyond type(uint256).max, totalSupply would overflow and Solidity's checked math would cause a revert.
Hence, the balanceOf[_recipient] += _amount; can be wrapped in unchecked to prevent an unnecessary overflow check on the recipient's balance, as it cannot ever overflow.
Handle
t11s
Vulnerability details
Impact
Since Wildcredit's ERC20 implementation uses the Solidity 0.8 compiler, all math operations are checked against over/underflow by default. However, some of these checks are unnecessary due to pre-checks. Wildcredit can selectively disable these over/underflow checks using the unchecked{} construct.
Proof of Concept
There are 3 lines where use of checked math is unnecessary:
The sum of all balances in the ERC20 will never exceed type(uint256).max, as totalSupply is safely incremented in _mint when creating new tokens. If _mint was ever called with a value that would increase the sum of all balances beyond type(uint256).max,
totalSupplywould overflow and Solidity's checked math would cause a revert.Hence, the
balanceOf[_recipient] += _amount;can be wrapped in unchecked to prevent an unnecessary overflow check on the recipient's balance, as it cannot ever overflow.Same as #1.
totalSupplywould overflow and revert first if the recipient would receive too many tokens.Inverse of #2. A user's balance can never exceed
totalSupply, hence decrementing of thetotalSupplywill never cause an underflow.Recommended Mitigation Steps
Wrap the 3 lines mentioned above in
unchecked {}