#42895 [BC-Insight] Misuse of error

Submitted on Mar 28th 2025 at 13:56:45 UTC by @okmxuse for Attackathon | Movement Labs

• Report ID: #42895

• Report Type: Blockchain/DLT

• Report severity: Insight

• Target: https://github.com/immunefi-team/attackathon-movement/tree/main/protocol-units/execution/maptos/opt-executor

• Impacts:

Description

Description

The function submit_transaction is invoked during the transaction processing pipeline. Within this function, the following check is performed:

async fn submit_transaction(
    &mut self,
    transaction: SignedTransaction,
) -> Result<SubmissionStatus, Error> {
    // Check whether the account is whitelisted
    if !self.is_whitelisted(&transaction.sender())? {
        return Ok((MempoolStatus::new(MempoolStatusCode::TooManyTransactions), None));
    }

If transaction.sender is not whitelisted, the function returns an error. However, the error type used here is MempoolStatusCode::TooManyTransactions.

This error code, as its name suggests, is intended to indicate that an account has reached its maximum transaction capacity:

// Account reached max capacity per account
TooManyTransactions = 3,

This intended use is further reinforced by its correct application in transaction_store.rs::insert:

if txns.len() >= self.capacity_per_user {
    return MempoolStatus::new(MempoolStatusCode::TooManyTransactions).with_message(
        format!(
            "Mempool over capacity for account. Number of transactions from account: {} Capacity per account: {}",
            txns.len(),
            self.capacity_per_user,
        ),
    );
}

Here, the error is returned only when the number of transactions from an account exceeds the allowed limit.

Impact

The primary issue with the current implementation is the confusion it may cause for both protocol users and developers. Misusing TooManyTransactions in a whitelist check introduces ambiguity in error handling and makes debugging more difficult.

Recommendation

We recommend either:

• Introducing a new, more appropriate error code to indicate that a transaction sender is not whitelisted.

• Handling the whitelist rejection differently, ensuring error messages accurately reflect the underlying issue.

Proof of Concept

POC

• The submit_transaction function is called during transaction processing.

• If the sender is not whitelisted, the following check triggers an error:

if !self.is_whitelisted(&transaction.sender())? {
    return Ok((MempoolStatus::new(MempoolStatusCode::TooManyTransactions), None));
}

• However, MempoolStatusCode::TooManyTransactions is meant to indicate that the user has exceeded their transaction limit.

• In this case, the sender is simply not whitelisted, making the error misleading.

• This misrepresentation can cause confusion for both interacting protocols and users.