OpenSea Seaport contest - rfa's results

Title: Set amount to 1, to minimize error https://github.com/code-423n4/2022-05-opensea-seaport/blob/main/contracts/lib/Executor.sol#L81

we can set this value constantly as 1, there is no need that this value should be dynamically set, since the _transferERC721() will check if the amount value is 1, and we can remove this check to make it cheaper overall

GAS 1. Title: Passing standardTransfer[i] directly to _transfer() https://github.com/code-423n4/2022-05-opensea-seaport/blob/main/contracts/conduit/Conduit.sol#L68-L71 https://github.com/code-423n4/2022-05-opensea-seaport/blob/main/contracts/conduit/Conduit.sol#L132-L135

Instead of storing standardTransfer[i] value into standardTransfer var. Passing it directly can save gas per loop

    function executeWithBatch1155(
        ConduitTransfer[] calldata standardTransfers,
        ConduitBatch1155Transfer[] calldata batchTransfers
    ) external override returns (bytes4 magicValue) {
        // Ensure that the caller has an open channel.
        if (!_channels[msg.sender]) {
            revert ChannelClosed();
        }

        // Retrieve the total number of transfers and place on the stack.
        uint256 totalStandardTransfers = standardTransfers.length;

        // Iterate over each standard transfer.
        for (uint256 i = 0; i < totalStandardTransfers; ) {

            // Perform the transfer.
            _transfer(standardTransfers[i]); // @audit-info: Pass the value directly here<-------------

            // Skip overflow check as for loop is indexed starting at zero.
            unchecked {
                ++i;
            }
        }

Title: Using assembly for checking open channel, can save some gas

Occurrences: https://github.com/code-423n4/2022-05-opensea-seaport/blob/main/contracts/conduit/Conduit.sol#L58 https://github.com/code-423n4/2022-05-opensea-seaport/blob/main/contracts/conduit/Conduit.sol#L96 https://github.com/code-423n4/2022-05-opensea-seaport/blob/main/contracts/conduit/Conduit.sol#L122

by replacing these check with assembly can save some gas

contract testing20 {

    uint public counter = 10;

    mapping(address => bool) public channels ; 

    function setChanel()public {
        channels[msg.sender] = true;
    }

    modifier checkChannel { 
        assembly {
            mstore(0, caller())
            mstore(32, channels.slot)
            if iszero(sload(keccak256(0, 64))) {revert(0, 0)}// sload directly from storage location
        }
        _;
    }

    function exec()public checkChannel{

        counter++;
    }
    function exec2()public checkChannel{

        counter++;
    }
    function exec3()public checkChannel{

        counter++;
    }
    // 28629 gas without modifier, 313165 gas deploy, 28551 gas optimization ON
    // 28572 gas OPTIMIZOOORRRRR,  274920 gas deploy, 28545 gas optimization ON, 28539 gas using iszero