Anyone Can Arbitrarily Mint Fungible Tokens In VaderPoolV2.mintFungible()

[code423n4]

Handle

leastwood

Vulnerability details

Impact

The mintFungible() function is callable by any user that wishes to mint liquidity pool fungible tokens. The protocol expects a user to first approve the contract as a spender before calling mintFungible(). However, any arbitrary user could monitor the blockchain for contract approvals that match VaderPoolV2.sol and effectively frontrun their call to mintFungible() by setting the to argument to their own address. As a result, the nativeDeposit and foreignDeposit amounts are transferred from the victim, and LP tokens are minted and finally transferred to the malicious user who is represented by the to address.

Proof of Concept

https://github.com/code-423n4/2021-11-vader/blob/main/contracts/dex-v2/pool/VaderPoolV2.sol#L284-L335

Tools Used

Manual code review.
Discussions with dev.

Recommended Mitigation Steps

Consider removing the from argument in mintFungible() and update the safeTransferFrom() calls to instead transfer from msg.sender.

[SamSteinGG]

The pool contracts, similarly to Uniswap V2, are never meant to be interacted with directly.

[alcueca]

You need to enforce that somehow.

[SamSteinGG]

Upon second consideration, the functions relating to the minting of synths and wrapped tokens should have had the onlyRouter modifier and thus are indeed vulnerable. Issue accepted.