Bids can be created while paused

[code423n4]

Lines of code

https://github.com/code-423n4/2022-09-nouns-builder/blob/7e9fddbbacdd7d7812e912a369cfd862ee67dc03/src/auction/Auction.sol#L88-L92

Vulnerability details

createBid() allows for bid creation while the Auction is paused. As the latter happens on a system error (mint failure), this can allow an attacker to interacts with the malfunctioning system.

This at least can lead to misallocation of user's funds, i.e. freezing the bid while there is no chance to get the token as mint doesn't work.

Proof of Concept

createBid() allows for funds deposit while the Auction is in malfunction state:

https://github.com/code-423n4/2022-09-nouns-builder/blob/7e9fddbbacdd7d7812e912a369cfd862ee67dc03/src/auction/Auction.sol#L88-L92

    /// @notice Creates a bid for the current token
    /// @param _tokenId The ERC-721 token id
    function createBid(uint256 _tokenId) external payable nonReentrant {
        // Get a copy of the current auction
        Auction memory _auction = auction;

Recommended Mitigation Steps

https://github.com/code-423n4/2022-09-nouns-builder/blob/7e9fddbbacdd7d7812e912a369cfd862ee67dc03/src/auction/Auction.sol#L88-L92

    /// @notice Creates a bid for the current token
    /// @param _tokenId The ERC-721 token id
-   function createBid(uint256 _tokenId) external payable nonReentrant {
+   function createBid(uint256 _tokenId) external payable whenNotPaused nonReentrant {
        // Get a copy of the current auction
        Auction memory _auction = auction;

[GalloDaSballo]

See #274