Submission Details
Severity:
In RToken Contract, the mint and burn functions return incorrect values.
01. Relevant GitHub Links
02. Summary
The mint and burn functions of RToken Contract are returning incorrect values.
03. Vulnerability Details
The code below is the RToken::mint function.
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());
emit Mint(caller, onBehalfOf, amountToMint, index);
@> return (isFirstMint, amountToMint, totalSupply(), amountScaled);
}
The description of the return value says that the second argument should be the amount of scaled tokens and the fourth argument should be the amount of underlying tokens minted, but it actually returns the opposite.
* @return A tuple containing:
* - bool: True if this is the first mint for the recipient, false otherwise
* - uint256: The amount of scaled tokens minted
* - uint256: The new total supply after minting
* - uint256: The amount of underlying tokens minted
*/
A similar problem occurs with the RToken::burn function.
function burn(
address from,
address receiverOfUnderlying,
uint256 amount,
uint256 index
) external override onlyReservePool returns (uint256, uint256, uint256) {
if (amount == 0) {
return (0, totalSupply(), 0);
}
uint256 userBalance = balanceOf(from);
_userState[from].index = index.toUint128();
if(amount > userBalance){
amount = userBalance;
}
uint256 amountScaled = amount.rayMul(index);
_userState[from].index = index.toUint128();
_burn(from, amount.toUint128());
if (receiverOfUnderlying != address(this)) {
IERC20(_assetAddress).safeTransfer(receiverOfUnderlying, amount);
}
emit Burn(from, receiverOfUnderlying, amount, index);
@> return (amount, totalSupply(), amount);
}
The description of the return value says that the first argument should be the amount of scaled tokens burned and the third argument should be the amount of underlying asset transferred, but in reality, they are both returning the same amount.
* @return A tuple containing:
* - uint256: The amount of scaled tokens burned
* - uint256: The new total supply after burning
* - uint256: The amount of underlying asset transferred
*/
04. Impact
Incorrectly returned values can cause unexpected problems when used in other contracts.
05. Tools Used
Manual Code Review and Foundry
06. Recommended Mitigation
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);
}
...
- return (isFirstMint, amountToMint, totalSupply(), amountScaled);
+ return (isFirstMint, amountScaled, totalSupply(), amountToMint);
}
function burn(
address from,
address receiverOfUnderlying,
uint256 amount,
uint256 index
) external override onlyReservePool returns (uint256, uint256, uint256) {
if (amount == 0) {
return (0, totalSupply(), 0);
}
uint256 userBalance = balanceOf(from);
_userState[from].index = index.toUint128();
if(amount > userBalance){
amount = userBalance;
}
uint256 amountScaled = amount.rayMul(index);
_userState[from].index = index.toUint128();
_burn(from, amount.toUint128());
if (receiverOfUnderlying != address(this)) {
IERC20(_assetAddress).safeTransfer(receiverOfUnderlying, amount);
}
emit Burn(from, receiverOfUnderlying, amount, index);
- return (amount, totalSupply(), amount);
+ return (amountScaled, totalSupply(), amount);
}
Updates
Lead Judging Commences
inallhonesty 4 months ago
Submission Judgement Published Assigned finding tags:
RToken::burn returns incorrect underlying asset amount (amount instead of amountScaled), leading to wrong interest rate calculations
inallhonesty 4 months ago
Submission Judgement Published Assigned finding tags:
RToken::burn returns incorrect underlying asset amount (amount instead of amountScaled), leading to wrong interest rate calculations
Prize pool breakdown
Total prize
77,280 USDC
nSLOC
3,86420 USDC / LOC
74,000
3,280
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