AbraNFT contest - kenta's results

2022-04-abranft

1 missing validation for array length. The inputs in cook are all arrays, However, these arrays’ length is not checked at the beginning of the function.

https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L637-L639 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L670-L672

Add the validation before for loop.

require(actions.length == values.length && values.length == datas.length, “error message”);

2 delete unused import statement

https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L26 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L26

Delete the above lines.

3 implement IERC721Receiver-onERC721Received and use safeTransferFrom. The following line use transferFrom for transferring the token. With the implementation of IERC721Receiver-onERC721Received you can use safeTransferFrom.

https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L238 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L218

Implement onERC721Received in the contract

2022-04-abranft gas optimization

1 use != 0 instead of > 0.

https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L739

if(_share != 0) {}

2 use unchecked and prefix in for loop

https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L494 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L527

for (uint256 k = 2; k <= COMPOUND_INTEREST_TERMS;) { // some executions unchecked { ++k; } }

3 use initial value, prefix and unchecked in loop

https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L641 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L674

for (uint256 i; i < actions.length;) { // some executions unchecked { ++i; } }

4 use calldata instead of memory.

https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L612 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPairWithOracle.sol#L638 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L579 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L592 https://github.com/code-423n4/2022-04-abranft/blob/main/contracts/NFTPair.sol#L605