Lines of code

Vulnerability details

Impact

After shutdown, checkpoints are stopped, leading to possible theft of rewards.

Proof of Concept

ConvexStakingWrapper No more checkpoints after shutdown, i.e. no updates reward.reward_integral_for[user]

    function _beforeTokenTransfer(
        address _from,
        address _to,
        uint256
    ) internal override {
@>      _checkpoint([_from, _to]);
    }

    function _checkpoint(address[2] memory _accounts) internal nonReentrant {
        //if shutdown, no longer checkpoint in case there are problems
@>      if (isShutdown()) return;

        uint256 supply = _getTotalSupply();
        uint256[2] memory depositedBalance;
        depositedBalance[0] = _getDepositedBalance(_accounts[0]);
        depositedBalance[1] = _getDepositedBalance(_accounts[1]);

        IRewardStaking(convexPool).getReward(address(this), true);

        _claimExtras();

        uint256 rewardCount = rewards.length;
        for (uint256 i = 0; i < rewardCount; i++) {
            _calcRewardIntegral(i, _accounts, depositedBalance, supply, false);
        }
    }    

This would result in, after shutdown, being able to steal rewards by transferring tokens to new users

Example:
Suppose the current
reward.reward_integral = 1000

When a shutdown occurs

1. alice transfers 100 to the new user, bob.
   Since bob is the new user and _beforeTokenTransfer()->_checkpoint() is not actually executed
   Result.
   balanceOf[bob] = 100
   reward.reward_integral_for[bob] = 0

2. bob executes claimRewards() to steal the reward
   reward amount = balanceOf[bob] * (reward.reward_integral - reward.reward_integral_for[bob])
   = 100 * (1000-0)

3. bob transfers the balance to other new users, looping steps 1-2 and stealing all rewards

Tools Used

Recommended Mitigation Steps

Still execute _checkpoint

    function _checkpoint(address[2] memory _accounts) internal nonReentrant {
        //if shutdown, no longer checkpoint in case there are problems
 -      if (isShutdown()) return;

        uint256 supply = _getTotalSupply();
        uint256[2] memory depositedBalance;
        depositedBalance[0] = _getDepositedBalance(_accounts[0]);
        depositedBalance[1] = _getDepositedBalance(_accounts[1]);

        IRewardStaking(convexPool).getReward(address(this), true);

        _claimExtras();

        uint256 rewardCount = rewards.length;
        for (uint256 i = 0; i < rewardCount; i++) {
            _calcRewardIntegral(i, _accounts, depositedBalance, supply, false);
        }
    }    

Assessed type

Context

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