Submission Details
Severity:
Potential for precision loss in `getCalculatedFee`
Summary
Potential for precision loss in getCalculatedFee
Vulnerability Details
We calculate the valueOfBorrowedToken and fee as shown in the code excerpt below.
uint256 valueOfBorrowedToken = (amount * getPriceInWeth(address(token))) / s_feePrecision;
//slither-disable-next-line divide-before-multiply
fee = (valueOfBorrowedToken * s_flashLoanFee) / s_feePrecision;
We can see that, valueOfBorrowedToken is later on multiplied by s_flashLoanFee even though the value of valueOfBorrowedToken was derived by the division with s_feePrecision on the first line in the above excerpt. Therein lies the potential for some precision loss.
Impact
There's some precision loss during the determination of fee.
Tools Used
Manual review
Recommendations
`ThunderLoan::getCalculatedFee` and `ThunderLoanUpgraded::getCalculatedFee`
function getCalculatedFee(IERC20 token, uint256 amount) public view returns (uint256 fee) {
- //slither-disable-next-line divide-before-multiply
- uint256 valueOfBorrowedToken = (amount * getPriceInWeth(address(token))) / s_feePrecision;
//slither-disable-next-line divide-before-multiply
- fee = (valueOfBorrowedToken * s_flashLoanFee) / s_feePrecision;
+ fee = (amount * getPriceInWeth(address(token)) * s_flashLoanFee) / (s_feePrecision * s_feePrecision);
}
Updates
Lead Judging Commences
0xnevi almost 2 years ago
Submission Judgement Published Assigned finding tags:
precision loss valueOfBorrowedToken
Rewards breakdown
nSLOC
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100 EXP
20 EXP
2 EXP
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