FEI and TRIBE Redemption contest - rbserver's results

[L-01] FUNCTIONALITY OF RariMerkleRedeemer.claimAndRedeem RELATED TO AMOUNT INPUTS IS MORE LIMITED THAN RariMerkleRedeemer.signAndClaimAndRedeem

When calling the following RariMerkleRedeemer.signAndClaimAndRedeem function, different amount inputs can be used for calling _multiClaim and _multiRedeem. However, when calling the claimAndRedeem function below, only one amounts input is used for calling both _multiClaim and _multiRedeem. Users, who have signed already, are not able to call claimAndRedeem if they want to call _multiClaim and _multiRedeem with different amount inputs and are forced to call _multiClaim and _multiRedeem separately in two different transactions, which costs more gas. To improve the usability of the claimAndRedeem function, it can be updated to include two different amount inputs that are used for calling _multiClaim and _multiRedeem respectively, which is similar to the signAndClaimAndRedeem function.

https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/fuse/RariMerkleRedeemer.sol#L108-L118

    function signAndClaimAndRedeem(
        bytes calldata signature,
        address[] calldata cTokens,
        uint256[] calldata amountsToClaim,
        uint256[] calldata amountsToRedeem,
        bytes32[][] calldata merkleProofs
    ) external override hasNotSigned nonReentrant {
        _sign(signature);
        _multiClaim(cTokens, amountsToClaim, merkleProofs);
        _multiRedeem(cTokens, amountsToRedeem);
    }

https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/fuse/RariMerkleRedeemer.sol#L99-L106

    function claimAndRedeem(
        address[] calldata cTokens,
        uint256[] calldata amounts,
        bytes32[][] calldata merkleProofs
    ) external hasSigned nonReentrant {
        _multiClaim(cTokens, amounts, merkleProofs);
        _multiRedeem(cTokens, amounts);
    }

[L-02] DECIMALS OF tokensReceived AND redeemedToken CAN BE CHECKED

As mentioned by the comment below, the previewRedeem function "assumes all of tokensReceived and redeemedToken have the same number of decimals". To ensure this, a require statement can be added in the TribeRedeemer contract's constructor to verify that the decimals of tokensReceived and redeemedToken are all equal before completing the construction of the contract.

https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/redeem/TribeRedeemer.sol#L44-L61

    function previewRedeem(uint256 amountIn)
        public
        view
        returns (address[] memory tokens, uint256[] memory amountsOut)
    {
        tokens = tokensReceivedOnRedeem();
        amountsOut = new uint256[](tokens.length);

        uint256 base = redeemBase;
        for (uint256 i = 0; i < tokensReceived.length; i++) {
            uint256 balance = IERC20(tokensReceived[i]).balanceOf(address(this));
            require(balance != 0, "ZERO_BALANCE");
            // @dev, this assumes all of `tokensReceived` and `redeemedToken`
            // have the same number of decimals
            uint256 redeemedAmount = (amountIn * balance) / base;
            amountsOut[i] = redeemedAmount;
        }
    }

[L-03] MESSAGE CAN BE UPDATED TO BE MORE SPECIFIC

The following MESSAGE is currently a sample generic message. Because MESSAGE is used for being signed by users, it can be updated to be more specific for improving user experience and avoiding confusion, especially if MESSAGE needs to be displayed by the frontend.

https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/fuse/MultiMerkleRedeemer.sol#L52-L53

    /// @notice The message to be signed by any users claiming on cTokens
    string public constant MESSAGE = "Sample message, please update.";

[L-04] _redeemBase CAN BE CHECKED AGAINST 0 IN TribeRedeemer contract's constructor

As the TribeRedeemer contract's constructor shows below, redeemBase is possible to be set to 0. However, calling the following previewRedeem function will revert if redeemBase is 0 due to the division by 0. To prevent this from happening, a require statement can be added in the contract's constructor to verify that _redeemBase is not 0 before executing redeemBase = _redeemBase.

https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/redeem/TribeRedeemer.sol#L27-L35

    constructor(
        address _redeemedToken,
        address[] memory _tokensReceived,
        uint256 _redeemBase
    ) {
        redeemedToken = _redeemedToken;
        tokensReceived = _tokensReceived;
        redeemBase = _redeemBase;
    }

https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/redeem/TribeRedeemer.sol#L44-L61

    function previewRedeem(uint256 amountIn)
        public
        view
        returns (address[] memory tokens, uint256[] memory amountsOut)
    {
        tokens = tokensReceivedOnRedeem();
        amountsOut = new uint256[](tokens.length);

        uint256 base = redeemBase;
        for (uint256 i = 0; i < tokensReceived.length; i++) {
            uint256 balance = IERC20(tokensReceived[i]).balanceOf(address(this));
            require(balance != 0, "ZERO_BALANCE");
            // @dev, this assumes all of `tokensReceived` and `redeemedToken`
            // have the same number of decimals
            uint256 redeemedAmount = (amountIn * balance) / base;
            amountsOut[i] = redeemedAmount;
        }
    }

[L-05] MISSING ZERO-ADDRESS CHECK FOR CRITICAL ADDRESSES

To prevent unintended behaviors, the critical address inputs should be checked against address(0).

Please consider checking the addresses of cTokens in the following constructor. https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/fuse/RariMerkleRedeemer.sol#L35-L44

    constructor(
        address token,
        address[] memory cTokens,
        uint256[] memory rates,
        bytes32[] memory roots
    ) {
        _configureExchangeRates(cTokens, rates);
        _configureMerkleRoots(cTokens, roots);
        _configureBaseToken(token);
    }

Please consider checking _core in the following constructor. https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/fuse/MerkleRedeemerDripper.sol#L10-L16

    constructor(
        address _core,
        address _target,
        uint256 _dripPeriod,
        uint256 _amountToDrip,
        address _token
    ) ERC20Dripper(_core, _target, _dripPeriod, _amountToDrip, _token) {}

Please consider chekcing _redeemedToken and addresses of _tokensReceived in the following constructor. https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/redeem/TribeRedeemer.sol#L27-L35

    constructor(
        address _redeemedToken,
        address[] memory _tokensReceived,
        uint256 _redeemBase
    ) {
        redeemedToken = _redeemedToken;
        tokensReceived = _tokensReceived;
        redeemBase = _redeemBase;
    }

[N-01] TYPO IN COMMENT

The phrase in the comment for the following _claim function should be "in the" instead of "int he". https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/shutdown/fuse/RariMerkleRedeemer.sol#L164-L169

    /// Should set the user's claim amount int he claims mapping for the provided cToken
    function _claim(
        address _cToken,
        uint256 _amount,
        bytes32[] calldata _merkleProof
    ) internal virtual {

[N-02] MISSING INDEXED EVENT FIELDS

Querying events can be optimized with index. Please consider adding index to fields of the following events.

https://github.com/code-423n4/2022-09-tribe/blob/main/contracts/peg/SimpleFeiDaiPSM.sol#L26-L29

    /// @notice event emitted upon a redemption
    event Redeem(address to, uint256 amountFeiIn, uint256 amountAssetOut);
    /// @notice event emitted when fei gets minted
    event Mint(address to, uint256 amountIn, uint256 amountFeiOut);

[N-03] NEWER VERSION OF SOLIDITY CAN BE USED

The protocol can benefit from more fixes and gas-efficient features by using a newer version of Solidity. Changes for newer Solidity versions can be found in https://blog.soliditylang.org/category/releases/. Please consider updating the versions for the following files.

contracts\shutdown\fuse\MerkleRedeemerDripper.sol
  2: pragma solidity =0.8.10;

contracts\shutdown\fuse\RariMerkleRedeemer.sol
  2: pragma solidity =0.8.10;