ReturnFungAndSemiFungFractionsOmnichainFacet Manual Review Findings

RFS-01M: Inexistent Handling of Refund

Type	Severity	Location
Logical Fault		ReturnFungAndSemiFungFractionsOmnichainFacet.sol:L28-L34

Description:

The ReturnFungAndSemiFungFractionsOmnichainFacet::handlePostPurchasePhase function will perform a cross-chain transaction using the Evergon Labs ODC implementation, however, any refund that will potentially be acquired if a surplus of msg.value is sent to the call is not handled as the refund address will be set to the ReturnFungAndSemiFungFractionsOmnichainFacet address itself (i.e. the Diamond).

Impact:

Any failed LayerZero transaction refund will be lost in the FractionalisationDiamond as it is not adequately handled.

Example:

Copy
19function handlePostPurchasePhase(
20    uint256 campaignId,
21    uint256 amountOfFractions,
22    uint32 chainId,
23    address msg_sender,
24    bytes calldata
25) external payable onlyInternalDelegateCall {
26    OmnichainAddress omnichainAccount = OmnichainAddresses.encode(chainId, msg_sender);
27
28    ISemiFungibleAndFungibleFractionTransferFacet(address(this)).transferFractions{value: msg.value}(
29        campaignId,
30        address(this),
31        omnichainAccount,
32        0, // In the first fractions mint, always id 0 is used (if semi-fungible)
33        amountOfFractions
34    );
35
36    emit PostPurchasePhaseHandled(campaignId, amountOfFractions, msg_sender);
37}

Recommendation:

We advise refunds to be adequately handled, potentially by keeping track of the LayerZero request ID and evaluating whether it has resulted in a refund through the OmnichainProxy. To note, any alleviation of this exhibit would require a significant refactor of the ODC codebase to better integrate with external implementations such as the tokenizer system.

Alleviation (71cda4ccfdcfa25fb96a4565f1f8143b350dd246):

The ODC implementation of the Evergon Labs team was refactored to support an explicitly defined refund address that is in turn propagated from the Erc1155FractionFacet::transferFractions function, ensuring that a failed transaction will properly refund the failed cross-chain transfer to the appropriate address.