Zellic - Audit Reports

Fee bypass for small amounts

Note that there is a fee bypass in sendOFT that LayerZero Labs is aware of:

!;; The rounding on the fee and amount calculation favors the sender,
!;; In theory small enough transfers will not incur any fees
(int, int) _getAmountAndFee(cell $storage, int totalAmount) impure inline {
    int feeBps = $storage.UsdtOFT::getFeeBps();
    ;; totalAmount is always at most 128-bits, feeBps is at most 10000 == 13 bits
    ;; so this multiplication can never overflow signed 257-bit
    int fee = ((totalAmount * feeBps) / BPS_DENOMINATOR);
    int amount = totalAmount - fee;
    return (amount, fee);
}

However, given the BPS_DENOMINATOR of 10000, exploiting this bug to completely bypass fees does not make sense in practice; the maximum transferrable amount while bypassing fees is ceil(BPS_DENOMINATOR / feeBps) - 1, which is a very small amount compared to the fees.