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

Incorrect Mint Amount in the `RToken.mint()` Function

kupiasec

Summary

The RToken.mint() function mints an amount using amountToMint instead of amountScaled. Here, amountToMint represents the quantity of reserve tokens, and minting RToken at this value implies an exchange rate of 1:1. This is incorrect.

Vulnerability Details

The RToken.mint() function mints an amount using amountToMint.

Since amountToMint represents the amount of reserve tokens, minting RToken at this value means that the exchange rate is 1:1, which is incorrect.

Instead, the mint amount should be amountScaled, which is the adjusted value according to the exchange rate index.

As a result, the depositor receives more RTokens than they should.

function mint(
address caller,
address onBehalfOf,
uint256 amountToMint,
uint256 index
) external override onlyReservePool returns (bool, uint256, uint256, uint256) {
if (amountToMint == 0) {
return (false, 0, 0, 0);
}
uint256 amountScaled = amountToMint.rayDiv(index);
if (amountScaled == 0) revert InvalidAmount();
​
uint256 scaledBalance = balanceOf(onBehalfOf);
bool isFirstMint = scaledBalance == 0;
​
uint256 balanceIncrease = 0;
if (_userState[onBehalfOf].index != 0 && _userState[onBehalfOf].index < index) {
balanceIncrease = scaledBalance.rayMul(index) - scaledBalance.rayMul(_userState[onBehalfOf].index);
}
​
_userState[onBehalfOf].index = index.toUint128();
​
136 _mint(onBehalfOf, amountToMint.toUint128());
​
emit Mint(caller, onBehalfOf, amountToMint, index);
​
return (isFirstMint, amountToMint, totalSupply(), amountScaled);
}

Impact

Depositors will receive more RTokens than they should.

Tools Used

Manual review

Recommendations

The mint amount should be amountScaled instead of amountToMint.

function mint(
address caller,
address onBehalfOf,
uint256 amountToMint,
uint256 index
) external override onlyReservePool returns (bool, uint256, uint256, uint256) {
if (amountToMint == 0) {
return (false, 0, 0, 0);
}
uint256 amountScaled = amountToMint.rayDiv(index);
if (amountScaled == 0) revert InvalidAmount();
​
uint256 scaledBalance = balanceOf(onBehalfOf);
bool isFirstMint = scaledBalance == 0;
​
uint256 balanceIncrease = 0;
if (_userState[onBehalfOf].index != 0 && _userState[onBehalfOf].index < index) {
balanceIncrease = scaledBalance.rayMul(index) - scaledBalance.rayMul(_userState[onBehalfOf].index);
}
​
_userState[onBehalfOf].index = index.toUint128();
​
- _mint(onBehalfOf, amountToMint.toUint128());
+ _mint(onBehalfOf, amountScaled.toUint128());
​
emit Mint(caller, onBehalfOf, amountToMint, index);
​
return (isFirstMint, amountToMint, totalSupply(), amountScaled);
}
Updates

Lead Judging Commences

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

RToken::mint should mint the amountScaled not the amountToMint

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

RToken::mint should mint the amountScaled not the amountToMint

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