Submission Details
Severity:
t-swap does not support token with fee on transfer
Summary
T-Swap does not support tokens with fee-on-transfer
Vulnerability Details
In T-swap, when we transfer tokens to our contract, we don't check the actual received token amount. This will work well in most cases except the tokens with fee on transfer.
If we transfer tokens with fee on transfer, we will get less tokens than we think. This will break our invariant.
function _addLiquidityMintAndTransfer(
uint256 wethToDeposit,
uint256 poolTokensToDeposit,
uint256 liquidityTokensToMint
) private {
_mint(msg.sender, liquidityTokensToMint);
emit LiquidityAdded(msg.sender, poolTokensToDeposit, wethToDeposit);
// Interactions
// @audit fee on transfer Token
i_wethToken.safeTransferFrom(msg.sender, address(this), wethToDeposit);
i_poolToken.safeTransferFrom(
msg.sender,
address(this),
poolTokensToDeposit
);
}
Impact
Our invariant will be broken. Our constant k will decrease when we deposit.
Tools Used
Manual
Recommendations
Refer to the uniswap v2, check the actual received amount
Rewards breakdown
nSLOC
276This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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