Core Contracts
Regnum Aurum Acquisition Corp
HardhatReal World AssetsNFT
77,280 USDC
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Submission Details
Severity: medium
Valid

`contractBalance` Miscalculation in the `RToken.calculateDustAmount()` Function

kupiasec

Summary

The contractBalance should represent the balance of underlying assets held by the RToken contract. However, it is incorrectly divided by the index, leading to an inaccurate calculation of the excess amount and resulting in locked underlying assets.

Vulnerability Details

The RToken.calculateDustAmount() function miscalculates the contractBalance.

Since contractBalance refers to the actual underlying assets held by the RToken contract. However, it is unjustifiably divided by the liquidity index of the LendingPool.

Consequently, the calculated excess amount is lower than it should be, causing some underlying assets to be locked.

function calculateDustAmount() public view returns (uint256) {
// Calculate the actual balance of the underlying asset held by this contract
319 uint256 contractBalance = IERC20(_assetAddress).balanceOf(address(this)).rayDiv(ILendingPool(_reservePool).getNormalizedIncome());
​
// Calculate the total real obligations to the token holders
uint256 currentTotalSupply = totalSupply();
​
// Calculate the total real balance equivalent to the total supply
uint256 totalRealBalance = currentTotalSupply.rayMul(ILendingPool(_reservePool).getNormalizedIncome());
// All balance, that is not tied to rToken are dust (can be donated or is the rest of exponential vs linear)
return contractBalance <= totalRealBalance ? 0 : contractBalance - totalRealBalance;
}

Impact

Some underlying assets may be locked.

Tools Used

Manual review

Recommendations

Do not divide by the liquidity index.

function calculateDustAmount() public view returns (uint256) {
// Calculate the actual balance of the underlying asset held by this contract
- uint256 contractBalance = IERC20(_assetAddress).balanceOf(address(this)).rayDiv(ILendingPool(_reservePool).getNormalizedIncome());
+ uint256 contractBalance = IERC20(_assetAddress).balanceOf(address(this));
​
// Calculate the total real obligations to the token holders
uint256 currentTotalSupply = totalSupply();
​
// Calculate the total real balance equivalent to the total supply
uint256 totalRealBalance = currentTotalSupply.rayMul(ILendingPool(_reservePool).getNormalizedIncome());
// All balance, that is not tied to rToken are dust (can be donated or is the rest of exponential vs linear)
return contractBalance <= totalRealBalance ? 0 : contractBalance - totalRealBalance;
}
Updates

Lead Judging Commences

inallhonesty Lead Judge 7 months ago
Submission Judgement Published
Validated
Assigned finding tags:

RToken::calculateDustAmount incorrectly applies liquidity index, severely under-reporting dust amounts and permanently trapping crvUSD in contract

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