Assets are not converted to shares when calculating fees

[code423n4]

Lines of code

https://github.com/GenerationSoftware/pt-v5-vault/blob/b1deb5d494c25f885c34c83f014c8a855c5e2749/src/Vault.sol#L572-L576

Vulnerability details

Impact

Unable to calculate cost correctly

Proof of Concept

The call path to get the balance

_liquidatableBalanceOf->availableYieldBalance

analyze

Through availableYieldBalance, we know that what is returned is assert not shares
Through mintYieldFee, _increaseYieldFeeBalance we know that _yieldFeeTotalSupply is shares，and the parameter that _increaseYieldFeeBalance needs to pass is shares

So the assert is missing here and converted to shares

Tools Used

manual review

Recommended Mitigation Steps

Convert assert to shares by _convertToShares

if (_yieldFeePercentage != 0) {
  _increaseYieldFeeBalance(
    _convertToShares(
      (_amountOut * FEE_PRECISION) / (FEE_PRECISION - _yieldFeePercentage) - _amountOut, 
      Math.Rounding.Down
   )
  );
}

Assessed type

Error

[c4-judge]

Picodes marked the issue as duplicate of #427

[c4-judge]

Picodes marked the issue as satisfactory

[c4-judge]

Picodes marked the issue as partial-50

[Picodes]

Partial credit due to the report's low quality