Yieldy contest - saian's results

add unchecked to save gas

Expression that cant overflow/underflow can be placed in a unchecked block which will avoid the default overflow/underflow checks introduced in 0.8 and save gas

Proof of concept

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Yieldy.sol#L190

    require(creditAmount <= creditBalances[msg.sender], "Not enough funds");

    creditBalances[msg.sender] = creditBalances[msg.sender] - creditAmount;

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Yieldy.sol#L212

    require(_allowances[_from][msg.sender] >= _value, "Allowance too low");

    uint256 newValue = _allowances[_from][msg.sender] - _value;

Cache storage variabes and save gas

Storage variables can be cached in a local variables and reused instead of reading from storage to save gas

Proof of concept

CURVE_POOL in setToAndFromCurve()

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Staking.sol#L634

replace curvePoolTo, curvePoolFrom with from, to

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Staking.sol#L649

    curvePoolFrom = from;
    curvePoolTo = to;
    
    emit LogSetCurvePool(CURVE_POOL, curvePoolTo, curvePoolFrom);

decimal can be replaced with function parameter _decimal

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Yieldy.sol#L44

    decimal = _decimal;
    WAD = 10**decimal; 

_totalSupply can be replaced with currentTotalSupply

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Yieldy.sol#L82

        uint256 currentTotalSupply = _totalSupply;
        require(_totalSupply > 0, "Can't rebase if not circulating"); 

_totalSupply in

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Yieldy.sol#L129

contract[i] in

        if (
            contracts[i] != address(0) &&
            IStaking(contracts[i]).canBatchTransactions()
        ) {
            IStaking(contracts[i]).sendWithdrawalRequests();
        }

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/BatchRequests.sol#L38

contracts[i] in

        bool canBatch = IStaking(contracts[i]).canBatchTransactions();
        batch[i] = Batch(contracts[i], canBatch);

contracts[_index] in

        return (
            contracts[_index],
            IStaking(contracts[_index]).canBatchTransactions()
        );

Avoid initialising variables with default values

When variables are created it contains default values, explicitly initialising with default values(0, address(0), false) is not necessary

Proof of concept

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Staking.sol#L636

    int128 from = 0;
    int128 to = 0;

Code can be simplified

Proof of concept

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/Staking.sol#L632

    address address0 = ICurvePool(CURVE_POOL).coins(0);
    address address1 = ICurvePool(CURVE_POOL).coins(1);
    int128 from = 0;
    int128 to = 0;

    if (TOKE_POOL == address0 && STAKING_TOKEN == address1) {
        to = 1;
    } else if (TOKE_POOL == address1 && STAKING_TOKEN == address0) {
        from = 1;
    }
    require(from == 1 || to == 1, "Invalid Curve Pool");

    curvePoolFrom = from;
    curvePoolTo = to;

    address address0 = ICurvePool(CURVE_POOL).coins(0);
    address address1 = ICurvePool(CURVE_POOL).coins(1);

    if (TOKE_POOL == address0 && STAKING_TOKEN == address1) {
        curvePoolTo = 1;
    } else if (TOKE_POOL == address1 && STAKING_TOKEN == address0) {
        curvePoolFrom = 1;
    } else {
        revert("Invalid Curve Pool");
    }

exit out of loop after delete

exit out of the loop after deleting address instead of iterating over the entire array

Proof of concept

https://github.com/code-423n4/2022-06-yieldy/blob/524f3b83522125fb7d4677fa7a7e5ba5a2c0fe67/src/contracts/BatchRequests.sol#L93

    for (uint256 i; i < contractsLength; ) {
        if (contracts[i] == _address) {
            delete contracts[i];    
        }                          
        unchecked {
            ++i;
        }
    }

Mitigation

Add return statement after delete statement, or swap last index with target index and pop the last element to avoid iterating over long array