Summary

The payForTransaction function's lack of error handling and fallback mechanisms for payment failures could lead to failed transactions, incomplete execution of operations, and potential locking of funds. Implementing proper error handling and fallback mechanisms will ensure that the contract can handle payment failures gracefully and continue its operations without disruptions.

Vulnerability Details

The payForTransaction function assumes the _transaction.payToTheBootloader() will succeed without additional validation or fallback mechanisms if it fails.

Impact

The payForTransaction function in the MondrianWallet2 contract assumes that the _transaction.payToTheBootloader() call will succeed. If this assumption fails, the contract does not have any fallback mechanism to handle the failure, which could lead to various issues such as:

• Transactions that rely on the bootloader payment will fail if the payment fails, potentially causing a denial of service

• Critical operations may not be completed if the payment fails, leading to inconsistencies or partial state changes.

• If the payment fails and there is no fallback, funds intended for the transaction could be locked within the contract without being utilized.

Tools Used

Manual review

Recommendations

• Add proper error handling and fallback mechanisms to ensure that payments are handled correctly. For example currently this is the function

  function payForTransaction(bytes32, /*_txHash*/ bytes32, /*_suggestedSignedHash*/ Transaction memory _transaction)

  external

  payable

  {

  bool success = _transaction.payToTheBootloader();

  if (!success) {

  revert MondrianWallet2__FailedToPay();

  }

  }

  
  This is now updated with fallback mechanism

  function payForTransaction(bytes32, /*_txHash*/ bytes32, /*_suggestedSignedHash*/ Transaction memory _transaction)

  external

  payable

  {

  // Attempt to pay the bootloader

  bool success = _transaction.payToTheBootloader();

  if (!success) {

  // Handle payment failure

  handlePaymentFailure(_transaction);

  }

  }

  ​

  function handlePaymentFailure(Transaction memory _transaction) internal {

  // Fallback mechanism to handle payment failure

  // For example, you can retry the payment or log the failure for further inspection

  ​

  // Attempt to retry payment

  bool retrySuccess = _transaction.payToTheBootloader();

  if (!retrySuccess) {

  // Log the payment failure

  emit PaymentFailed(_transaction.to, _transaction.value, _transaction.data);

  // Optionally, you can refund the sender or take other necessary actions

  revert MondrianWallet2__FailedToPay();

  }

  }

  ​

  // Event to log payment failures

  event PaymentFailed(address to, uint256 value, bytes data);

• The contract should implement a retry mechanism to handle temporary issues that might cause the payment to fail. This can help ensure that transient issues do not cause permanent failures.

• Adding event logs for payment failures can help in tracking and debugging issues. It provides a way to monitor the contract's behavior and identify patterns in failures.

• Consider implementing additional fallback actions in case of persistent failures. For example, refunding the sender, notifying external monitoring systems, or taking other corrective actions.