LI.FI contest - minhquanym's results

Lines of code

https://github.com/code-423n4/2022-03-lifinance/blob/699c2305fcfb6fe8862b75b26d1d8a2f46a551e6/src/Libraries/LibAsset.sol#L67-L68

Vulnerability details

Impact

• In function approveERC20 of LibAsset, line 67 safeApprove to 0 before safeApprove to MAX_INT in line 68. This is because we can only approve their allowance to zero or from zero in SafeERC20.
• In SafeERC20, it is used to prevent front-run by approved addresses and usually users have to do 2 TXs.
• But when we do both in 1 TX, it does not add any layer of security and just wasting gas. Such behavior creates a false sense of security.

Proof of concept

• https://github.com/code-423n4/2022-03-lifinance/blob/699c2305fcfb6fe8862b75b26d1d8a2f46a551e6/src/Libraries/LibAsset.sol#L67-L68

Recommended Mitigation Steps

• Simply call IERC20(assetId).approve(spender, MAX_INT);