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Submission Details
Severity: low
Invalid

Potential division by zero in `LibFertilizer::addUnderlying` function

bube

Summary

The LibFertilizer::addUnderlying function is vulnerable to a division by zero error. This occurs when the remainingRecapitalization function returns zero, indicating that no additional capital is needed.

Vulnerability Details

The LibFertilizer::addUnderlying function calculates the percentToFill:

​
function addUnderlying(uint256 tokenAmountIn, uint256 usdAmount, uint256 minAmountOut) internal {
AppStorage storage s = LibAppStorage.diamondStorage();
// Calculate how many new Deposited Beans will be minted
@> uint256 percentToFill = usdAmount.mul(C.precision()).div(remainingRecapitalization());
...
}
​

But when calculating this variable there is a possibility for division by zero error. This is due to the remainingRecapitalization function:

​
function remainingRecapitalization()
internal
view
returns (uint256 remaining)
{
AppStorage storage s = LibAppStorage.diamondStorage();
uint256 totalDollars = C
.dollarPerUnripeLP()
@> .mul(C.unripeLP().totalSupply())
.div(DECIMALS);
totalDollars = totalDollars / 1e6 * 1e6; // round down to nearest USDC
@> if (s.recapitalized >= totalDollars) return 0;
return totalDollars.sub(s.recapitalized);
}
​

The LibFertilizer::remainingRecapitalization function can return 0 if s.recapitalized >= totalDollars.
Also, if C.unripeLP().totalSupply() is 0, then the totalDollars will be also 0. The totalDollars is uint256. So the line totalDollars.sub(s.recapitalized) will have an underflow issue.

Impact

If LibFertilizer::remainingRecapitalization() function returns zero, the division operation in the LibFertilizer::addUnderlying function will cause a revert, halting the execution of the addUnderlying function and any transaction that invokes it.

Also, if the totalSupply in the LibFertilizer::remainingRecapitalization() is 0, the totalDollars will be 0 and the function will have an underflow issue.

Tools Used

Manual Review

Recommendations

Implement a check before the division in the LibFertilizer::addUnderlying function to ensure that the returned value of remainingRecapitalization is greater than zero:

​
function addUnderlying(uint256 tokenAmountIn, uint256 usdAmount, uint256 minAmountOut) internal {
AppStorage storage s = LibAppStorage.diamondStorage();
// Calculate how many new Deposited Beans will be minted
+ if (remainingRecapitalization() > 0) {
uint256 percentToFill = usdAmount.mul(C.precision()).div(remainingRecapitalization());
+ }
...
}
​

Also, ensure that the totalSupply in LibFertilizer::remainingRecapitalization is not 0 and this line return totalDollars.sub(s.recapitalized); will not cause an underflow issue.

Updates

Lead Judging Commences

giovannidisiena Lead Judge about 1 year ago
Submission Judgement Published
Invalidated
Reason: Design choice
Assigned finding tags:

Informational/Invalid

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