Frankencoin - J4de's results

Lines of code

https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Position.sol#L249-L255

Vulnerability details

Impact

If the collateral is a multi-address ERC20 token, the withdraw function can be used to bypass the checkCollateral check.

Proof of Concept

Tools Used

Manual audit

Recommended Mitigation Steps

There is no business dealing with other ERC20 tokens in the Position.sol contract. It is recommended that there is no need to provide token withdraw at a specified address.

Lines of code

https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Equity.sol#L309-L316

Vulnerability details

Impact

In the loop body, addressesToWipe[0] is processed every time, which causes the first address to be processed in each value of RestructureCapTable, which does not conform to the original intention of the RestructureCapTable function.

Proof of Concept

Tools Used

Manual audit

Recommended Mitigation Steps

    function restructureCapTable(address[] calldata helpers, address[] calldata addressesToWipe) public {
        require(zchf.equity() < MINIMUM_EQUITY);
        checkQualified(msg.sender, helpers);
        for (uint256 i = 0; i<addressesToWipe.length; i++){
-           address current = addressesToWipe[0];
+           address current = addressesToWipe[i];
            _burn(current, balanceOf(current));
        }
    }

Lines of code

https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/MintingHub.sol#L208-L214

Vulnerability details

Impact

File: MintingHub.sol
208         if (challenge.position.tryAvertChallenge(challenge.size, _bidAmountZCHF)) {
209             // bid was high enough, let bidder buy collateral from challenger
210             zchf.transferFrom(msg.sender, challenge.challenger, _bidAmountZCHF);
211             challenge.position.collateral().transfer(msg.sender, challenge.size);
212             emit ChallengeAverted(address(challenge.position), _challengeNumber);
213             delete challenges[_challengeNumber];
214         } else {

During the challenge, if the bid is high enough to satisfy tryAvertChallenge, the challenge can be ended immediately, and the bidder and challenger exchange tokens.

File: Position.sol
304     function tryAvertChallenge(uint256 _collateralAmount, uint256 _bidAmountZCHF) external onlyHub returns (bool) {
305         if (block.timestamp >= expiration){
306             return false; // position expired, let every challenge succeed
307         } else if (_bidAmountZCHF * ONE_DEC18 >= price * _collateralAmount){
308             // challenge averted, bid is high enough
309             challengedAmount -= _collateralAmount;
310             // Don't allow minter to close the position immediately so challenge can be repeated before
311             // the owner has a chance to mint more on an undercollateralized position
312             restrictMinting(1 days);
313             return true;
314         } else {
315             return false;
316         }
317     }

After satisfying tryAvertChallenge, position will enter a 1-day cooldown period.

The attacker can act as a challenger and bidder to make the position enter a 1-day cooldown at 0 cost.

Proof of Concept

Tools Used

Manual audit

Recommended Mitigation Steps

It is recommended to charge a certain fee for challengers who fail the challenge.

Lines of code

https://github.com/code-423n4/2023-04-frankencoin/blob/main/contracts/Frankencoin.sol#L1

Vulnerability details

Impact

The power of minter in Frankencoin is very large, and minter may be a third-party component. If minter gets out of control, it may cause Frankencoin to crash. But the current situation is that as long as minter is added, even if it loses control later, Frankencoin shareholders cannot delete or restrict it.

Proof of Concept

Tools Used

Manual audit

Recommended Mitigation Steps

It is recommended that shareholders vote (requires a large number of votes) to delete minter.