The Standard
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Submission Details
Severity: low
Valid

User can skip paying fees for minting and burning EUROs, when amount is low enough

dimulski

Summary

When a user creates a vault, where he can add collateral and in return mint EURO tokens to himself, he is expected to pay a fee on every call to mint() and burn(). However if the amount is very small a user can skip paying the fees. Because of the following line in the mint() function:

uint256 fee = _amount * ISmartVaultManagerV3(manager).mintFeeRate() / ISmartVaultManagerV3(manager).HUNDRED_PC();

And this line in the burn() function:

uint256 fee = _amount * ISmartVaultManagerV3(manager).burnFeeRate() / ISmartVaultManagerV3(manager).HUNDRED_PC();

For example if the mintFeeRate() is 500 which should represent 0.5% according to the devs and we try to mint 199 EUROs we won't pay any fee to the LiquidationPoolManager() contract, which is the contract where the fees have to be sent to. When we put numbers in the formula we get the following 199 * 500 / 100000 which is 0.

Vulnerability Details

Gist

After following the steps in the above provided gist, add the following test to the AuditorTestst.t.sol :

function test_NoFeesMint() public {
vm.startPrank(bob);
vm.deal(bob, 10 ether);
(address vault, uint256 tokenId) = vaultManagerV5Instance.mint();
SmartVaultV3 vaultInstance = SmartVaultV3(payable(vault));
address(vault).call{value: 5 ether}("");
/// @dev 500 is the mintFeeRate and burnFeeRate as set per standart team test files
/// @notice fee should be transfered to the liquidationPoolManager contract
console2.log("EUROs balance of liquidationPoolManager before minting: ", EURO.balanceOf(address(liquidationPoolManager)));
vaultInstance.mint(bob, 199);
console2.log("Bob's euros balance: ", EURO.balanceOf(bob));
console2.log("EUROs balance of liquidationPoolManager before minting: ", EURO.balanceOf(address(liquidationPoolManager)));
vm.stopPrank();
}
Logs:
EUROs balance of liquidationPoolManager before minting: 0
Bob's euros balance: 199
EUROs balance of liquidationPoolManager before minting: 0

Impact

Protocol looses some small fees.

Tools Used

Manual Review & Foundry

Recommendations

Add a minimum amount that can be minted for example 1e18 EUROs

Updates

Lead Judging Commences

hrishibhat Lead Judge over 1 year ago
Submission Judgement Published
Validated
Assigned finding tags:

fee-loss

hrishibhat Lead Judge over 1 year ago
Submission Judgement Published
Validated
Assigned finding tags:

mint-precision

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