Some tokens do not implement the ERC20 standard properly but are still accepted by most code that accepts ERC20 tokens. For example Tether (USDT)'s transfer() and transferFrom() functions do not return booleans as the specification requires, and instead have no return value. When these sorts of tokens are cast to IERC20, their function signatures do not match and therefore the calls made, revert.
lacoop6tu
commented
2 years ago
Lines of code
https://github.com/code-423n4/2022-08-fiatdao/blob/fece3bdb79ccacb501099c24b60312cd0b2e4bb2/contracts/VotingEscrow.sol#L426 https://github.com/code-423n4/2022-08-fiatdao/blob/fece3bdb79ccacb501099c24b60312cd0b2e4bb2/contracts/VotingEscrow.sol#L486 https://github.com/code-423n4/2022-08-fiatdao/blob/fece3bdb79ccacb501099c24b60312cd0b2e4bb2/contracts/VotingEscrow.sol#L546 https://github.com/code-423n4/2022-08-fiatdao/blob/fece3bdb79ccacb501099c24b60312cd0b2e4bb2/contracts/VotingEscrow.sol#L657 https://github.com/code-423n4/2022-08-fiatdao/blob/fece3bdb79ccacb501099c24b60312cd0b2e4bb2/contracts/VotingEscrow.sol#L676
Vulnerability details
Impact
Some tokens do not implement the ERC20 standard properly but are still accepted by most code that accepts ERC20 tokens. For example Tether (USDT)'s transfer() and transferFrom() functions do not return booleans as the specification requires, and instead have no return value. When these sorts of tokens are cast to IERC20, their function signatures do not match and therefore the calls made, revert.
Proof of Concept
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/4a9cc8b4918ef3736229a5cc5a310bdc17bf759f/contracts/token/ERC20/utils/SafeERC20.sol
Recommended Mitigation Steps
it’s highly advised to use OpenZeppelin’s SafeERC20's safeTransfer()/safeTransferFrom() instead.