Gas Optimizations - Githubissues

code423n4 commented 1 year ago

[G-01] Splitting require() statements that use && saves gas

IMPACT

Require statements including conditions with the && operator can be broken down in multiple require statements to save gas.

POC

        require(version == 1 && _bytecodeHash[1] == bytes1(0), "zf"); // Incorrectly formatted bytecodeHash

MITIGATION

Breakdown each condition in a separate require

require(version == 1);
require(_bytecodeHash[1] == bytes1(0), "zf");)

[G-02] abi.encode() is less efficient than abi.encodePacked()

File: ethereum\contracts\bridge\L1ERC20Bridge.sol
82:        bytes memory create2Input = abi.encode(address(this), l2ProxyTokenBytecodeHash, _governor);

168:       data = abi.encode(data1, data2, data3);

File: ethereum\contracts\zksync\DiamondInit.sol
54:         s.storedBlockHashes[0] = keccak256(abi.encode(storedBlockZero));

File: ethereum\contracts\zksync\facets\DiamondCut.sol 27:      s.diamondCutStorage.proposedDiamondCutHash = keccak256(abi.encode(_facetCuts, _initAddress));

File:

381:        return abi.encode(_block.l2LogsTreeRoot, l2ToL1LogsHash, initialStorageChangesHash, repeatedStorageChangesHash);

https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/ethereum/contracts/bridge/L1ERC20Bridge.sol#L82 https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/ethereum/contracts/bridge/L1ERC20Bridge.sol#L168 https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/ethereum/contracts/zksync/DiamondInit.sol#L54 https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/ethereum/contracts/zksync/facets/DiamondCut.sol#L27 https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/ethereum/contracts/zksync/facets/Executor.sol#L381

[G-03] Expressions for constant values such as a call to keccak256(), should use immutable

Impact

Expressions for constant values such as a call to keccak256(), should use immutable rather than constant See https://github.com/ethereum/solidity/issues/9232 issue for a detail description of the issue Similar bug: https://github.com/code-423n4/2021-11-unlock-findings/issues/238

POC

File: ethereum\contracts\common\L2ContractHelper.sol

41:    bytes32 constant CREATE2_PREFIX = keccak256("zksyncCreate2");

https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/ethereum/contracts/common/L2ContractHelper.sol#L41 https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/zksync/contracts/L2ContractHelper.sol#L24

[G-04] calldata is more gas efficient than memory

When running a function we could pass the function parameters as calldata or memory for variables such as strings, structs,arrays etc. If we are not modifying the passed parameter we should pass it as calldata because calldata is more gas efficient than memory. Let's see an example:

POC

File: zksync\contracts\ExternalDecoder.sol

10:    function decodeString(bytes memory _input) external pure returns (string memory result) {
        (result) = abi.decode(_input, (string));
12:    }

https://github.com/code-423n4/2022-10-zksync/blob/456078b53a6d09636b84522ac8f3e8049e4e3af5/zksync/contracts/ExternalDecoder.sol#L10-L12