Submission Details
Severity:
Zero Fees For Low-Value Sales Due To Integer Division
Vulnerability Details
In TokenDivider.sol, the fee calculation uses integer division which rounds down to 0 for small prices:
uint256 fee = order.price / 100; // fee = 0 if price < 100 wei
uint256 sellerFee = fee / 2; // sellerFee = 0 if price <= 200 wei
For example:
If price = 99 wei: fee = 99/100 = 0 wei
If price = 199 wei: fee = 1 wei, but sellerFee = 1/2 = 0 wei
Impact
Protocol loses revenue on small trades
Recommendations
Use basis points (BPS) and multiply before division to avoid rounding to zero:
// Fee is 1% (100 BPS)
uint256 constant FEE_BPS = 100;
uint256 constant BPS_DENOMINATOR = 10000;
function buyOrder(uint256 orderIndex, address seller) external payable {
// ...existing code...
uint256 fee = (order.price * FEE_BPS) / BPS_DENOMINATOR;
uint256 sellerFee = fee / 2;
// ...existing code...
}
This ensures precise fee calculation even for small amounts.
Rewards breakdown
nSLOC
181This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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