Dopex - ciphermarco's results

Lines of code

https://github.com/code-423n4/2023-08-dopex/blob/main/contracts/reLP/ReLPContract.sol#L286-L295

Vulnerability details

Impact

This code contains a potentially dangerous bug that uses zero values for amountAmin and amountBmin in the contracts/reLP/ReLPContract.sol contract's addLiquidity function call, which can expose the transaction to front-running attacks and unpredictable outcomes, including impermanent loss.

Proof of Concept

The vulnerable code snippet is as follows:

(, , uint256 lp) = IUniswapV2Router(addresses.ammRouter).addLiquidity(
  addresses.tokenA,
  addresses.tokenB,
  tokenAAmountOut,
  amountB / 2,
  0, // @audit 0 value for amountAmin
  0, // @audit 0 value for amountBmin
  address(this),
  block.timestamp + 10 // @audit this means any deadline
);

It's worth noting that block.timestamp + 10 is functionally equivalent to block.timestamp, which is equivalent to having no deadline at all. However, the critical issue arises from setting amountAmin and amountBmin values to zero, which, when combined with a block.timestamp deadline, allows for infinite slippage.

To exploit this vulnerability, an attacker could monitor pending transactions, observe this transaction, and submit a new adversarial transaction, causing the original transaction to receive fewer tokens than expected or acceptable.

Tools Used

Manual: code editor.

Recommended Mitigation Steps

To mitigate the risks associated with this vulnerability, it is strongly recommended to specify meaningful non-zero values for amountAmin and amountBmin in the addLiquidity function call. These values should be calculated based on the acceptable slippage and market conditions to protect against front-running attacks and reduce the potential for impermanent loss.

Here's an example of how to set non-zero values for amountAmin and amountBmin:

uint256 minTokenA = calculateMinAmount(); // Calculate a reasonable minimum amount.
uint256 minTokenB = calculateMinAmount(); // Calculate a reasonable minimum amount.

(, , uint256 lp) = IUniswapV2Router(addresses.ammRouter).addLiquidity(
  addresses.tokenA,
  addresses.tokenB,
  tokenAAmountOut,
  amountB / 2,
  minTokenA,
  minTokenB,
  address(this),
  block.timestamp + 10
);

By implementing these mitigation steps, the code will be more resistant to front-running attacks and will provide a more predictable outcome for liquidity provision.

Assessed type

MEV