Submission Details
Severity:
`TSwapPool::swapExactInput` Returns an incorrect value everytime
Summary
The swapExactInput function is expected to return the actual amount of tokens bought by the caller. However, it does not use the declared output variable and a value is never assigned.
Vulnerability Details
The return value will always be 0, returning incorrect information to the caller.
Impact
This test shows that the swapExactInput function always returns 0
function testSwapExactInputReturn() public {
vm.startPrank(liquidityProvider);
weth.approve(address(pool), 100e18);
poolToken.approve(address(pool), 100e18);
pool.deposit(100e18, 100e18, 100e18, uint64(block.timestamp));
vm.stopPrank();
vm.startPrank(user);
uint256 expected = 9e18;
poolToken.approve(address(pool), 10e18);
uint256 swapExactInputReturnValue =
pool.swapExactInput(poolToken, 10e18, weth, expected, uint64(block.timestamp));
vm.stopPrank();
assertEq(swapExactInputReturnValue, 0);
}
Tools Used
--Foundry
Recommendations
It is recommended to assign and correctly return the output 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(inputAmount, inputReserves, outputReserves);
+ output = getOutputAmountBasedOnInput(inputAmount, inputReserves, outputReserves);
- if (output < minOutputAmount) {
- revert TSwapPool__OutputTooLow(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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