Popcorn contest - codetilda's results

[L-01] Missing ReEntrancy Guard to claimRewards function in MultiRewardStaking.sol

Violation of the CEI(Checks/Effects/Iteraction) pattern without ReEntrancy guard may result in an unsafe external call (ReEntrancy Attack).

Instance:

MultiRewardStaking.sol#L170

function claimRewards(address user, IERC20[] memory _rewardTokens) external accrueRewards(msg.sender, user) {
  for (uint8 i; i < _rewardTokens.length; i++) {
  
  @audit CHECKS
  uint256 rewardAmount = accruedRewards[user][_rewardTokens[i]];

  if (rewardAmount == 0) revert ZeroRewards(_rewardTokens[i]);
      
  EscrowInfo memory escrowInfo = escrowInfos[_rewardTokens[i]];
  
  @audit ITERACTION
  if (escrowInfo.escrowPercentage > 0) {
    _lockToken(user, _rewardTokens[i], rewardAmount, escrowInfo);
    emit RewardsClaimed(user, _rewardTokens[i], rewardAmount, true);
  } else {
    _rewardTokens[i].transfer(user, rewardAmount);
    emit RewardsClaimed(user, _rewardTokens[i], rewardAmount, false);
  }

  @audit EFFECTS
  accruedRewards[user][_rewardTokens[i]] = 0;
  }
}

Recommended Mitigation Steps

Move line of code accruedRewards[user][_rewardTokens[i]] = 0; to the top before actual "Iteraction" part of function to achieve CEI pattern

function claimRewards(address user, IERC20[] memory _rewardTokens) external accrueRewards(msg.sender, user) {
  for (uint8 i; i < _rewardTokens.length; i++) {
  
  @audit CHECKS
  uint256 rewardAmount = accruedRewards[user][_rewardTokens[i]];

  if (rewardAmount == 0) revert ZeroRewards(_rewardTokens[i]);
      
  EscrowInfo memory escrowInfo = escrowInfos[_rewardTokens[i]];
  
  + @audit EFFECTS
  + accruedRewards[user][_rewardTokens[i]] = 0;
  
  @audit ITERACTION
  if (escrowInfo.escrowPercentage > 0) {
    _lockToken(user, _rewardTokens[i], rewardAmount, escrowInfo);
    emit RewardsClaimed(user, _rewardTokens[i], rewardAmount, true);
  } else {
    _rewardTokens[i].transfer(user, rewardAmount);
    emit RewardsClaimed(user, _rewardTokens[i], rewardAmount, false);
  }

  - @audit EFFECTS
  - accruedRewards[user][_rewardTokens[i]] = 0;

  }
}