NextGen - cu5t0mpeo's results

Lines of code

https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/hardhat/smart-contracts/AuctionDemo.sol#L57-L61 https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/hardhat/smart-contracts/AuctionDemo.sol#L124-L130 https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/hardhat/smart-contracts/AuctionDemo.sol#L134-L143

Vulnerability details

Impact

An attacker can create a higher-priced Bid by constructing a malicious auction order to restrict others from auctioning the NFT, and at the end of the final auction, purchase the target token at an extremely low price.

Proof of Concept

The conditions for the participateToAuction function to create an order are:

1. The amount sent by the user is greater than the maximum value
2. The current time is the auction time
3. The auction order is valid

    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);
    }

There is no penalty for users canceling orders.

    // cancel a single Bid

    function cancelBid(uint256 _tokenid, uint256 index) public {
        require(block.timestamp <= minter.getAuctionEndTime(_tokenid), "Auction ended");
        require(auctionInfoData[_tokenid][index].bidder == msg.sender && auctionInfoData[_tokenid][index].status == true);
        auctionInfoData[_tokenid][index].status = false;
        (bool success, ) = payable(auctionInfoData[_tokenid][index].bidder).call{value: auctionInfoData[_tokenid][index].bid}("");
        emit CancelBid(msg.sender, _tokenid, index, success, auctionInfoData[_tokenid][index].bid);
    }

This will result in the user being able to directly create two orders, one with a very low price and one with a very high price. At the last point of the auction, the order will be canceled, resulting in the target nft being successfully auctioned at an extremely low price.

Tools Used

Manual Review

Recommended Mitigation Steps

1.Each person can only quote once, and the next quote should be changed on the original basis.

2.If an order is canceled during the auction time period, a partial fee will be charged.

Assessed type

Other

Lines of code

https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/hardhat/smart-contracts/AuctionDemo.sol#L104-L120

Vulnerability details

Impact

Due to incorrect claimAuction check conditions, the user's amount will be stolen.

Proof of Concept

The claimAuction function should be a function that can only be called after the auction ends. The method for checking the end of the auction is block.timestamp >= minter.getAuctionEndTime(_tokenid). This check condition is the same as the two functions cancelBid and cancelAllBids the inspection is the same.

    // claim Token After Auction

    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 {}
        }
    }

    // cancel a single Bid

    function cancelBid(uint256 _tokenid, uint256 index) public {
>@      require(block.timestamp <= minter.getAuctionEndTime(_tokenid), "Auction ended");//
        require(auctionInfoData[_tokenid][index].bidder == msg.sender && auctionInfoData[_tokenid][index].status == true);
        auctionInfoData[_tokenid][index].status = false;
        (bool success, ) = payable(auctionInfoData[_tokenid][index].bidder).call{value: auctionInfoData[_tokenid][index].bid}("");
        emit CancelBid(msg.sender, _tokenid, index, success, auctionInfoData[_tokenid][index].bid);
    }

And claimAuction will not change any state variables after claiming the reward, so it has no impact on the two functions cancelBid and cancelAllBids.

Finally, the attacker can first call claimAuction when the block.timestamp time is equal to minter.getAuctionEndTime(_tokenid), and then call cancelBid or cancelAllBids after claiming the remaining nft quantity and other orders to achieve theft other users’ funds.

Tools Used

Manual Review

Recommended Mitigation Steps

change require(block.timestamp >= minter.getAuctionEndTime(_tokenid) && auctionClaim[_tokenid] == false && minter.getAuctionStatus(_tokenid) == true); to require(block.timestamp > minter.getAuctionEndTime(_tokenid) && auctionClaim[_tokenid] == false && minter.getAuctionStatus(_tokenid) == true);

Assessed type

Timing

Lines of code

https://github.com/code-423n4/2023-10-nextgen/blob/8b518196629faa37eae39736837b24926fd3c07c/hardhat/smart-contracts/AuctionDemo.sol#L110-L119

Vulnerability details

Impact

User funds will be permanently stuck in the contract.

Proof of Concept

In the for loop, since all auction orders will be traversed, when the auction winner is a smart contract and onERC721Received is not implemented, this will cause the NFT to be unable to be transmitted normally and revert will be sent, and ultimately the funds will not be available receive normally.

    // claim Token After Auction

    function claimAuction(uint256 _tokenid) public WinnerOrAdminRequired(_tokenid,this.claimAuction.selector){ 
        ...
        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

Manual Review

Recommended Mitigation Steps

You can try to wrap it with try-catch or process the received nft separately.

Assessed type

DoS