Core Contracts
Regnum Aurum Acquisition Corp
HardhatReal World AssetsNFT
77,280 USDC
View results
Previous Next
Submission Details
Severity: high
Valid

Transfer amount is scaled twice in RToken.sol

0xsandy

Summary

Transfer amount is scaled twice in RToken.sol

Vulnerability Details

In the RToken.sol contract, transfer() and transferFrom() functions are overwritten as:

function transfer(address recipient, uint256 amount) public override(ERC20, IERC20) returns (bool) {
uint256 scaledAmount = amount.rayDiv(ILendingPool(_reservePool).getNormalizedIncome());
return super.transfer(recipient, scaledAmount);
}
​
function transferFrom(address sender, address recipient, uint256 amount) public override(ERC20, IERC20) returns (bool) {
uint256 scaledAmount = amount.rayDiv(_liquidityIndex);
return super.transferFrom(sender, recipient, scaledAmount);
}

here, amount is scaled beforehand.

But, _update() is also overwritten:

function _update(address from, address to, uint256 amount) internal override {
// Scale amount by normalized income for all operations (mint, burn, transfer)
uint256 scaledAmount = amount.rayDiv(ILendingPool(_reservePool).getNormalizedIncome());
super._update(from, to, scaledAmount);
}

And it scales the amount again for transfer() functions.

As we know, _update is called in transfer() functions again for ERC20 tokens. Thus, amount will be scaled twice with index.

Impact

Due to scaling twice, while transferring RTokens, the receiver will receive more or less than expected. i.e more if index < 1 and less if index > 1.

In the withdraw() function of StabilitiyPool.sol:

function withdraw(uint256 deCRVUSDAmount) external nonReentrant whenNotPaused validAmount(deCRVUSDAmount) {
_update();
if (deToken.balanceOf(msg.sender) < deCRVUSDAmount) revert InsufficientBalance();
​
uint256 rcrvUSDAmount = calculateRcrvUSDAmount(deCRVUSDAmount);
uint256 raacRewards = calculateRaacRewards(msg.sender);
if (userDeposits[msg.sender] < rcrvUSDAmount) revert InsufficientBalance();
userDeposits[msg.sender] -= rcrvUSDAmount;
​
if (userDeposits[msg.sender] == 0) {
delete userDeposits[msg.sender];
}
​
deToken.burn(msg.sender, deCRVUSDAmount);
rToken.safeTransfer(msg.sender, rcrvUSDAmount);
if (raacRewards > 0) {
raacToken.safeTransfer(msg.sender, raacRewards);
}
​
emit Withdraw(msg.sender, rcrvUSDAmount, deCRVUSDAmount, raacRewards);
}

msg.sender is transferred RTokens and if index is >1, the msg.sender withdrawing tokens will receive less than expected. Thus, loss of funds for the user.

And if index is <1, loss of funds for the protocol. Thus, the high severity.

Tools Used

Manual Analysis

Recommendations

Modify the _update() function as:

function _update(address from, address to, uint256 amount) internal override {
if (from == address(0) || to == address(0)) {
uint256 scaledAmount = amount.rayDiv(ILendingPool(_reservePool).getNormalizedIncome());
super._update(from, to, scaledAmount);
return;
}
}

This will exclude the transfer functions.

Updates

Lead Judging Commences

inallhonesty Lead Judge 4 months ago
Submission Judgement Published
Validated
Assigned finding tags:

RToken::transfer and transferFrom double-scale amounts by dividing in both external functions and _update, causing users to transfer significantly less than intended

inallhonesty Lead Judge 4 months ago
Submission Judgement Published
Validated
Assigned finding tags:

RToken::transfer and transferFrom double-scale amounts by dividing in both external functions and _update, causing users to transfer significantly less than intended

Support

FAQs

Can't find an answer? Chat with us on Discord, Twitter or Linkedin.