Lines of code

Vulnerability details

Impact

As specified in Convex BaseRewardPool.sol and VirtualRewardPool.sol, the function signature of earned is earned(address). However, balanceOfJPEG did not pass any arguments to earned, which would cause balanceOfJPEG to always revert.

This bug will propagate through Controller and YVault until finally reaching the source of the call in YVaultLPFarming ._computeUpdate, and render the entire farming contract unuseable.

Proof of Concept

Both BaseRewardPool.earned and VirtualBalanceRewardPool.earned takes an address as argument

    function earned(address account) public view returns (uint256) {
        return
            balanceOf(account)
                .mul(rewardPerToken().sub(userRewardPerTokenPaid[account]))
                .div(1e18)
                .add(rewards[account]);
    }

    function earned(address account) public view returns (uint256) {
        return
            balanceOf(account)
                .mul(rewardPerToken().sub(userRewardPerTokenPaid[account]))
                .div(1e18)
                .add(rewards[account]);
    }

But balanceOfJPEG does not pass any address to extraReward.earned, causing the entire function to revert when called

    function balanceOfJPEG() external view returns (uint256) {
        uint256 availableBalance = jpeg.balanceOf(address(this));

        IBaseRewardPool baseRewardPool = convexConfig.baseRewardPool;
        uint256 length = baseRewardPool.extraRewardsLength();
        for (uint256 i = 0; i < length; i++) {
            IBaseRewardPool extraReward = IBaseRewardPool(baseRewardPool.extraRewards(i));
            if (address(jpeg) == extraReward.rewardToken()) {
                availableBalance += extraReward.earned();
                //we found jpeg, no need to continue the loop
                break;
            }
        }

        return availableBalance;
    }

Tools Used

vim, ganache-cli

Recommended Mitigation Steps

Pass address(this) as argument of earned.

Notice how we modify the fetching of reward. This is reported in a separate bug report, but for completeness, the entire fix is shown in both report entries.

    function balanceOfJPEG() external view returns (uint256) {
        uint256 availableBalance = jpeg.balanceOf(address(this));

        IBaseRewardPool baseRewardPool = convexConfig.baseRewardPool;
        availableBalance += baseRewardPool.earned(address(this));
        uint256 length = baseRewardPool.extraRewardsLength();
        for (uint256 i = 0; i < length; i++) {
            IBaseRewardPool extraReward = IBaseRewardPool(baseRewardPool.extraRewards(i));
            if (address(jpeg) == extraReward.rewardToken()) {
                availableBalance += extraReward.earned(address(this));
            }
        }

        return availableBalance;
    }

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