zzykxx - The protocol can't receive rewards because of low gas limits on ETH transfers

[sherlock-admin]

zzykxx

high

The protocol can't receive rewards because of low gas limits on ETH transfers

Summary

The hardcoded gas limit of the Asset::transferETH() function, used to transfer ETH in the protocol, is too low and will result unwanted reverts.

Vulnerability Detail

ETH transfers in the protocol are always done via Asset::transferETH(), which performs a low-level call with an hardcoded gas limit of 10_000:

(bool success,) = recipient.call{value: amount, gas: 10_000}('');
if (!success) {revert ETH_TRANSFER_FAILED();}

The hardcoded 10_000 gas limit is not high enough for the protocol to be able receive and distribute rewards. Rewards are currently only available for native ETH, an are received by Rio via:

• Partial withdrawals
• ETH in excess of 32ETH on full withdrawals

The flow to receive rewards requires two steps:

1. An initial call to EigenPod::verifyAndProcessWithdrawals(), which queues a withdrawal to the Eigenpod owner: an RioLRTOperatorDelegator instance
2. A call to DelayedWithdrawalRouter::claimDelayedWithdrawals().

The call to DelayedWithdrawalRouter::claimDelayedWithdrawals() triggers the following flow:

1. ETH are transferred to the RioLRTOperatorDelegator instance, where the receive() function is triggered.
2. The receive() function of RioLRTOperatorDelegator transfers ETH via Asset::transferETH() to the RioLRTRewardDistributor, where another receive() function is triggered.
3. The receive() function of RioLRTRewardDistributor transfers ETH via Asset::transferETH() to the treasury, the operatorRewardPool and the RioLRTDepositPool.

The gas is limited at 10_000 in step 2 and is not enough to perform step 3, making it impossible for the protocol to receive rewards and leaving funds stuck.

POC

Add the following imports to RioLRTOperatorDelegator.t.sol:

import {IRioLRTOperatorRegistry} from 'contracts/interfaces/IRioLRTOperatorRegistry.sol';
import {RioLRTOperatorDelegator} from 'contracts/restaking/RioLRTOperatorDelegator.sol';
import {CredentialsProofs, BeaconWithdrawal} from 'test/utils/beacon-chain/MockBeaconChain.sol';

then copy-paste:

function test_outOfGasOnRewards() public {
    address alice = makeAddr("alice");
    uint256 initialBalance = 40e18;
    deal(alice, initialBalance);
    vm.prank(alice);
    reETH.token.approve(address(reETH.coordinator), type(uint256).max);

    //->Operator delegator and validators are added to the protocol
    uint8 operatorId = addOperatorDelegator(reETH.operatorRegistry, address(reETH.rewardDistributor));
    RioLRTOperatorDelegator operatorDelegator =
        RioLRTOperatorDelegator(payable(reETH.operatorRegistry.getOperatorDetails(operatorId).delegator));

    //-> Alice deposits ETH in the protocol
    vm.prank(alice);
    reETH.coordinator.depositETH{value: initialBalance}();

    //-> Rebalance is called and the ETH deposited in a validator
    vm.prank(EOA, EOA);
    reETH.coordinator.rebalance(ETH_ADDRESS);

    //-> Create a new validator with a 40ETH balance and verify his credentials.
    //-> This is to "simulate" rewards accumulation
    uint40[] memory validatorIndices = new uint40[](1);
    IRioLRTOperatorRegistry.OperatorPublicDetails memory details = reETH.operatorRegistry.getOperatorDetails(operatorId);
    bytes32 withdrawalCredentials = operatorDelegator.withdrawalCredentials();
    beaconChain.setNextTimestamp(block.timestamp);
    CredentialsProofs memory proofs;
    (validatorIndices[0], proofs) = beaconChain.newValidator({
        balanceWei: 40 ether,
        withdrawalCreds: abi.encodePacked(withdrawalCredentials)
    });

    //-> Verify withdrawal crendetials
    vm.prank(details.manager);
    reETH.operatorRegistry.verifyWithdrawalCredentials(
        operatorId,
        proofs.oracleTimestamp,
        proofs.stateRootProof,
        proofs.validatorIndices,
        proofs.validatorFieldsProofs,
        proofs.validatorFields
    );

    //-> Process a full withdrawal, 8ETH (40ETH - 32ETH) will be queued withdrawal as "rewards"
    verifyAndProcessWithdrawalsForValidatorIndexes(address(operatorDelegator), validatorIndices);

    //-> Call `claimDelayedWithdrawals` to claim the withdrawal
    delayedWithdrawalRouter.claimDelayedWithdrawals(address(operatorDelegator), 1); //❌ Reverts for out-of-gas
}

Impact

The protocol is unable to receive rewards and the funds will be stucked.

Code Snippet

Tool used

Manual Review

Recommendation

Remove the hardcoded 10_000 gas limit in Asset::transferETH(), at least on ETH transfers where the destination is a protocol controlled contract.

[sherlock-admin4]

The protocol team fixed this issue in the following PRs/commits: https://github.com/rio-org/rio-sherlock-audit/pull/4

[10xhash]

The protocol team fixed this issue in PR/commit rio-org/rio-sherlock-audit#4.

Fixed Removed the 10k gas limit

[sherlock-admin4]

The Lead Senior Watson signed off on the fix.