Submission Details
Severity:
Unnecessary code in `deposit` function
Summary
poolTokenReserves is not used but it is calculated in the function.
Vulnerability Details
poolTokenReserves is not used in the function and getPoolTokensToDepositBasedOnWeth gets poolTokenReserves again.
function deposit(
uint256 wethToDeposit,
uint256 minimumLiquidityTokensToMint,
uint256 maximumPoolTokensToDeposit,
uint64 deadline
)
external
revertIfZero(wethToDeposit)
returns (uint256 liquidityTokensToMint)
{
if (wethToDeposit < MINIMUM_WETH_LIQUIDITY) {
revert TSwapPool__WethDepositAmountTooLow(
MINIMUM_WETH_LIQUIDITY,
wethToDeposit
);
}
if (totalLiquidityTokenSupply() > 0) {
uint256 wethReserves = i_wethToken.balanceOf(address(this));
uint256 poolTokenReserves = i_poolToken.balanceOf(address(this));
// Our invariant says weth, poolTokens, and liquidity tokens must always have the same ratio after the
// initial deposit
// poolTokens / constant(k) = weth
// weth / constant(k) = liquidityTokens
// aka...
// weth / poolTokens = constant(k)
// To make sure this holds, we can make sure the new balance will match the old balance
// (wethReserves + wethToDeposit) / (poolTokenReserves + poolTokensToDeposit) = constant(k)
// (wethReserves + wethToDeposit) / (poolTokenReserves + poolTokensToDeposit) =
// (wethReserves / poolTokenReserves)
//
// So we can do some elementary math now to figure out poolTokensToDeposit...
// (wethReserves + wethToDeposit) / poolTokensToDeposit = wethReserves
// (wethReserves + wethToDeposit) = wethReserves * poolTokensToDeposit
// (wethReserves + wethToDeposit) / wethReserves = poolTokensToDeposit
uint256 poolTokensToDeposit = getPoolTokensToDepositBasedOnWeth(
wethToDeposit
);
if (maximumPoolTokensToDeposit < poolTokensToDeposit) {
revert TSwapPool__MaxPoolTokenDepositTooHigh(
maximumPoolTokensToDeposit,
poolTokensToDeposit
);
}
// We do the same thing for liquidity tokens. Similar math.
liquidityTokensToMint =
(wethToDeposit * totalLiquidityTokenSupply()) /
wethReserves;
if (liquidityTokensToMint < minimumLiquidityTokensToMint) {
revert TSwapPool__MinLiquidityTokensToMintTooLow(
minimumLiquidityTokensToMint,
liquidityTokensToMint
);
}
_addLiquidityMintAndTransfer(
wethToDeposit,
poolTokensToDeposit,
liquidityTokensToMint
);
} else {
// This will be the "initial" funding of the protocol. We are starting from blank here!
// We just have them send the tokens in, and we mint liquidity tokens based on the weth
_addLiquidityMintAndTransfer(
wethToDeposit,
maximumPoolTokensToDeposit,
wethToDeposit
);
liquidityTokensToMint = wethToDeposit;
}
}
Impact
Users end up making unnecessary calculations and end up consuming gas.
Tools Used
Manual review
Recommendations
Please remove unnecessary code in the function
-- uint256 poolTokenReserves = i_poolToken.balanceOf(address(this));
Rewards breakdown
nSLOC
276This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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