panic: arithmetic underflow or overflow | VRFCoordinatorV2_5Mock::createSubscription function.

[alymurtazamemon]

I am implementing a new version of VRFCoordinator v2.5 in my code and for local testing I am using VRFCoordinatorV2_5Mock contract. Unfortunately, while calling the createSubscription function of this contract (as instructed in the Local testing using a mock subscription contract) I am getting this error;

[⠢] Compiling...
[⠰] Compiling 2 files with 0.8.19
[⠔] Solc 0.8.19 finished in 1.20s
Compiler run successful!
0x4e487b710000000000000000000000000000000000000000000000000000000000000011
Traces:
  [4282228] → new DeploySubscriptionVRFV2_5@0x5b73C5498c1E3b4dbA84de0F1833c4a029d90519
    └─ ← [Return] 21276 bytes of code

  [6225604] DeploySubscriptionVRFV2_5::run()
    ├─ [3279821] → new SubscriptionVRF_HelperConfig@0xC7f2Cf4845C6db0e1a1e91ED41Bcd0FcC1b0E141
    │   └─ ← [Return] 16160 bytes of code
    ├─ [2909757] SubscriptionVRF_HelperConfig::getConfig()
    │   ├─ [0] VM::startBroadcast()
    │   │   └─ ← [Return] 
    │   ├─ [2863541] → new VRFCoordinatorV2_5Mock@0x5FbDB2315678afecb367f032d93F642f64180aa3
    │   │   ├─ emit ConfigSet()
    │   │   └─ ← [Return] 13951 bytes of code
    │   ├─ [2616] VRFCoordinatorV2_5Mock::createSubscription()
    │   │   └─ ← [Revert] panic: arithmetic underflow or overflow (0x11)
    │   └─ ← [Revert] panic: arithmetic underflow or overflow (0x11)
    └─ ← [Revert] panic: arithmetic underflow or overflow (0x11)

After some debugging, I found that the error was caused by the subtraction of blockhash(block.number - 1) in the createSubscription function while generating subId in this contract

chainlink-brownie-contracts/contracts/src/v0.8/vrf/dev/SubscriptionAPI.sol

I removed the -1 from this line, and everything started working as expected. The modified line now looks like this:

subId = uint256(keccak256(abi.encodePacked(msg.sender, blockhash(block.number), address(this), currentSubNonce)));

The code may expect block.number > 1, but even after mining some blocks before this transaction, the issue persists.

Leaving this here so others can see the temporary solution and developers can work on a permanent fix for this issue.

here is the code;

function getOrCreateLocalBlockchainNetworkConfig()
    private
    returns (NetworkConfig memory)
{
    if (localNetworkConfig.vrfCoordinatorV2_5 != address(0)) {
        return localNetworkConfig;
    }

    vm.startBroadcast();

    VRFCoordinatorV2_5Mock vrfMock = new VRFCoordinatorV2_5Mock(
        MOCK_BASE_FEE,
        MOCK_GAS_PRICE_LINK,
        MOCK_WEI_PER_UINT_LINK
    );

    uint256 subscriptionId = vrfMock.createSubscription();
    vrfMock.fundSubscription(subscriptionId, FUND_AMOUNT);

    vm.stopBroadcast();

    localNetworkConfig = NetworkConfig({
        vrfCoordinatorV2_5: address(vrfMock),
        subscriptionId: subscriptionId,
        callbackGasLimit: 40000,
        gasLane: 0x787d74caea10b2b357790d5b5247c2f63d1d91572a9846f780606e4d953677ae
    });

    return localNetworkConfig;
}

[alymurtazamemon]

This issue has been preview on the Pull Requests. To resolve, Contact the dAppNode page to initiate a chat with the live agent on the chat button to get more information about your request via dAppNode Thank you for posting @alymurtazamemon

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[Kendo007]

Worked for Me!! Thank You!