Submission Details
Severity:
Unused named return parameter in `TSwapPool:swapExactInput`, the named return parameter is `output` but is not used anywhere in the code, so this function will always return zero (0)
Summary
The TSwapPool:swapExactInput has a named return, but that named return is not used anywhere in the function body, hence the function is always going to return zero (0).
Vulnerability Details
The user will always see zero (0) returning from TSwapPool:swapExactInput leading to confusion at best, and panic at worst.
Tools Used
Foundry
Proof of Concept
modifier addLiquidity {
vm.startPrank(liquidityProvider);
weth.approve(address(pool), 100e18);
poolToken.approve(address(pool), 100e18);
pool.deposit(100e18, 100e18, 100e18, uint64(block.timestamp));
_;
}
function testSwapExactInput(uint32 fuzzInput) addLiquidity public {
// We don't test if the input is 0
if (fuzzInput == 0) { return; }
IERC20 inputToken = poolToken;
uint256 inputAmount = uint256(fuzzInput);
IERC20 outputToken = weth;
uint256 minOutputAmount = 0;
uint64 deadline = uint64(block.timestamp + 15 minutes);
vm.startPrank(user);
inputToken.approve(address(pool), inputAmount);
uint256 output = pool.swapExactInput(inputToken, inputAmount, outputToken, minOutputAmount, deadline);
assertEq(output, 0);
}
Recommended Mitigation
Is to simply is the named return variable.
function swapExactInput(
IERC20 inputToken,
uint256 inputAmount,
IERC20 outputToken,
uint256 minOutputAmount,
uint64 deadline
)
public
revertIfZero(inputAmount)
revertIfDeadlinePassed(deadline)
returns (uint256 output)
{
uint256 inputReserves = inputToken.balanceOf(address(this));
uint256 outputReserves = outputToken.balanceOf(address(this));
- uint256 outputAmount = getOutputAmountBasedOnInput(
+ output = getOutputAmountBasedOnInput(
inputAmount,
inputReserves,
outputReserves
);
- if (outputAmount < minOutputAmount) {
+ if (output < minOutputAmount) {
revert TSwapPool__OutputTooLow(outputAmount, minOutputAmount);
}
- _swap(inputToken, inputAmount, outputToken, outputAmount);
+ _swap(inputToken, inputAmount, outputToken, output);
}
Updates
Appeal created
inallhonesty about 1 year ago
Submission Judgement Published Assigned finding tags:
Default value returned by TSwapPool::swapExactInput results in incorrect return value given
Rewards breakdown
nSLOC
276This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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