Lybra Finance - jnrlouis's results

Lines of code

https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/token/EUSD.sol#L411-L428

Vulnerability details

Impact

Wrong assumption on the mint function assumes that if sharesAmount == 0, totalSupply == 0.

        if (sharesAmount == 0) {
            //EUSD totalSupply is 0: assume that shares correspond to EUSD 1-to-1
            sharesAmount = _mintAmount;
        }

https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/token/EUSD.sol#L415-L418

Meanwhile this is NOT the case.

Proof of Concept

If you look at the mint function,

    function mint(address _recipient, uint256 _mintAmount) external onlyMintVault MintPaused returns (uint256 newTotalShares) {
        require(_recipient != address(0), "MINT_TO_THE_ZERO_ADDRESS");


        uint256 sharesAmount = getSharesByMintedEUSD(_mintAmount);
        if (sharesAmount == 0) {
            //EUSD totalSupply is 0: assume that shares correspond to EUSD 1-to-1
            sharesAmount = _mintAmount;
        }


        newTotalShares = _totalShares.add(sharesAmount);
        _totalShares = newTotalShares;


        shares[_recipient] = shares[_recipient].add(sharesAmount);


        _totalSupply += _mintAmount;


        emit Transfer(address(0), _recipient, _mintAmount);
    }

https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/token/EUSD.sol#L411-L428

The sharesAmount is gotten from the getSharesByMintedEUSD function.

    function getSharesByMintedEUSD(uint256 _EUSDAmount) public view returns (uint256) {
        uint256 totalMintedEUSD = _totalSupply;
        if (totalMintedEUSD == 0) {
            return 0;
        } else {
            return _EUSDAmount.mul(_totalShares).div(totalMintedEUSD);
        }
    }

https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/token/EUSD.sol#L299-L306

Assuming _totalSupply = 1000; _totalShares = 800; calling the mint function with _mintAmount = 1; would give sharesAmount = 0; As 1 * 800/100 = 0.8 = 0 (Rounded down to 0).

In this case, a non-zero _totalSupply would still give a sharesAmount of 0.

Tools Used

Manual Review

Recommended Mitigation Steps

Assessed type

Other

Lines of code

https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/LybraRETHVault.sol#L9-L11 https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/LybraRETHVault.sol#L46-L48 https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/base/LybraPeUSDVaultBase.sol#L58-L70 https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/base/LybraPeUSDVaultBase.sol#L96-L100 https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/base/LybraPeUSDVaultBase.sol#L125-L128 https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/base/LybraPeUSDVaultBase.sol#L157-L168 https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/base/LybraPeUSDVaultBase.sol#L212-L220 https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/base/LybraPeUSDVaultBase.sol#L269-L270

Vulnerability details

Impact

Most of the critical functions would be broken in the RETH vault due to an error with a function name in the interface.

Proof of Concept

The error is from:

interface IRETH {
    function getExchangeRatio() external view returns (uint256);
}

https://github.com/code-423n4/2023-06-lybra/blob/5d70170f2c68dbd3f7b8c0c8fd6b0b2218784ea6/contracts/lybra/pools/LybraRETHVault.sol#L9-L11

The main issue is the function name in the interface declaration getExchangeRatio(). Looking at the RocketTokenRETH contract on etherscan: https://etherscan.io/address/0xae78736cd615f374d3085123a210448e74fc6393#code, the correct function name should be getExchangeRate() as getExchangeRatio() doesn't exist. This can be further seen in the RocketTokenRETHInterface.sol.

This would mean most of the critical functions would be broken as getAssetPrice() uses this broken function here - This would in turn affect functions like depositAssetToMint(), mint(), liquidation(), rigidRedemption() and withdraw().

Tools Used

Manual review

Recommended Mitigation Steps

Correct the spelling error in the interface to:

function getExchangeRate() external view returns (uint256);

Assessed type

Error