NextGen - Kaysoft's results

Lines of code

https://github.com/code-423n4/2023-10-nextgen/blob/main/smart-contracts/AuctionDemo.sol#L57-L61 https://github.com/code-423n4/2023-10-nextgen/blob/main/hardhat/smart-contracts/AuctionDemo.sol#L57-L61

Vulnerability details

Impact

Current winner of the bid could lose the bid in the last possible moment. The goal of sniping is often to catch other participants off guard and secure the winning bid for the valuable NFTs.

Proof of Concept

Snipping refers to the practice of placing a bid at the last possible moment in an attempt to win an auction just before it closes. The participateToAuction(...) function does not have any snipping protection implemented.

function participateToAuction(uint256 _tokenid) public payable {
        require(msg.value > returnHighestBid(_tokenid) && block.timestamp <= minter.getAuctionEndTime(_tokenid) && minter.getAuctionStatus(_tokenid) == true);
        auctionInfoStru memory newBid = auctionInfoStru(msg.sender, msg.value, true);
        auctionInfoData[_tokenid].push(newBid);
    }

Tools Used

Vs code

Recommended Mitigation Steps

To implement sniping protection in an auction smart contract, developers may incorporate various features or strategies. Here are a few common approaches:

Extended Bidding Period:

One simple way to counter sniping is to extend the auction's closing time whenever a new bid is placed close to the original closing time. This gives other participants additional time to respond with higher bids.

Bid Increments:

Implementing bid increment rules ensures that the next bid must exceed the current highest bid by a predefined increment. This makes it more difficult for snipers to place bids at the last moment since they would need to exceed the current highest bid by a larger amount.

Reveal Periods:

Introduce a "reveal period" after the auction ends but before the final winner is determined. During this period, participants can reveal any secret bids they placed. This prevents snipers from waiting until the last moment to reveal high bids.

Randomized Ending Times:

Randomizing the ending time of the auction within a certain window can make it more challenging for snipers to predict the exact moment to place their bids.

Assessed type

Timing

Lines of code

https://github.com/code-423n4/2023-10-nextgen/blob/main/smart-contracts/AuctionDemo.sol#L104-L120

Vulnerability details

Impact

Loss of fund by the owner of the NFT that is auctioned.

Proof of Concept

From the code in the claimAuction(...) function on line 113, the Eth from the sales of the auctioned NFT is not transferred to the owner of the NFT but transferred to the owner of the smart contract.

 function claimAuction(uint256 _tokenid) public WinnerOrAdminRequired(_tokenid,this.claimAuction.selector){
        require(block.timestamp >= minter.getAuctionEndTime(_tokenid) && auctionClaim[_tokenid] == false && minter.getAuctionStatus(_tokenid) == true);
        auctionClaim[_tokenid] = true;
        uint256 highestBid = returnHighestBid(_tokenid);
        address ownerOfToken = IERC721(gencore).ownerOf(_tokenid);
        address highestBidder = returnHighestBidder(_tokenid);
        for (uint256 i=0; i< auctionInfoData[_tokenid].length; i ++) {
            if (auctionInfoData[_tokenid][i].bidder == highestBidder && auctionInfoData[_tokenid][i].bid == highestBid && auctionInfoData[_tokenid][i].status == true) {
                IERC721(gencore).safeTransferFrom(ownerOfToken, highestBidder, _tokenid);
                (bool success, ) = payable(owner()).call{value: highestBid}("");
                emit ClaimAuction(owner(), _tokenid, success, highestBid);
            } else if (auctionInfoData[_tokenid][i].status == true) {
                (bool success, ) = payable(auctionInfoData[_tokenid][i].bidder).call{value: auctionInfoData[_tokenid][i].bid}("");
                emit Refund(auctionInfoData[_tokenid][i].bidder, _tokenid, success, highestBid);
            } else {}
        }
    }

Tools Used

Vs code

Recommended Mitigation Steps

On line 113, change the owner() with ownerOfToken this way

 function claimAuction(uint256 _tokenid) public WinnerOrAdminRequired(_tokenid,this.claimAuction.selector){
        require(block.timestamp >= minter.getAuctionEndTime(_tokenid) && auctionClaim[_tokenid] == false && minter.getAuctionStatus(_tokenid) == true);
        auctionClaim[_tokenid] = true;
        uint256 highestBid = returnHighestBid(_tokenid);
        address ownerOfToken = IERC721(gencore).ownerOf(_tokenid);
        address highestBidder = returnHighestBidder(_tokenid);
        for (uint256 i=0; i< auctionInfoData[_tokenid].length; i ++) {
            if (auctionInfoData[_tokenid][i].bidder == highestBidder && auctionInfoData[_tokenid][i].bid == highestBid && auctionInfoData[_tokenid][i].status == true) {
                IERC721(gencore).safeTransferFrom(ownerOfToken, highestBidder, _tokenid);
--               (bool success, ) = payable(owner()).call{value: highestBid}("");
++               (bool success, ) = payable(ownerOfToken).call{value: highestBid}("");
                emit ClaimAuction(owner(), _tokenid, success, highestBid);
            } else if (auctionInfoData[_tokenid][i].status == true) {
                (bool success, ) = payable(auctionInfoData[_tokenid][i].bidder).call{value: auctionInfoData[_tokenid][i].bid}("");
                emit Refund(auctionInfoData[_tokenid][i].bidder, _tokenid, success, highestBid);
            } else {}
        }
    }

Assessed type

ETH-Transfer