Moonwell

Overview

In preparation for the upcoming upgrade of the WELL token to the xERC20 standard, which will enable the token to be natively used on the Base network for voting and staking, the Wormhole Bridge Adapter on Moonbeam needs to be upgraded. While the upgraded WELL token is not yet in use, it is governed by the Moonwell governor, so this upgrade must be performed through governance.

This upgraded Wormhole Bridge Adapter will support a more user-friendly experience by automatically unwrapping the xERC20 version of WELL back to the original Moonbeam native WELL token on transfer, which will reduce the number of steps required to transfer tokens between Moonbeam and Base.

Security

This change has been audited by Halborn Security as part of the xERC20 upgrade, and no security issues were found. The audit report can be found here.

In order to ensure no storage slot collisions, the slither tool was used to view the storage offset changes in the new logic contract. No storage slot collisions were found, and a single variable lockbox was added to the WormholeUnwrapperAdapter contract, which inherits the WormholeBridgeAdapter.

Wormhole Adapter Unwrapper

slither src/xWELL/WormholeUnwrapperAdapter.sol --print variable-order --solc-remaps '@openzeppelin-contracts/=lib/openzeppelin-contracts/OpenZeppelin Defender/=lib/openzeppelin-contracts/ @openzeppelin-contracts-upgradeable/=lib/openzeppelin-contracts-upgradeable/ @protocol=src/ @proposals=src/proposals/'

WormholeUnwrapperAdapter:
+---------------------------------------+---------------------------------------------+------+--------+
|                  Name                 |                     Type                    | Slot | Offset |
+---------------------------------------+---------------------------------------------+------+--------+
|       Initializable._initialized      |                    uint8                    |  0   |   0    |
|      Initializable._initializing      |                     bool                    |  0   |   1    |
|        ContextUpgradeable.__gap       |                 uint256[50]                 |  1   |   0    |
|       OwnableUpgradeable._owner       |                   address                   |  51  |   0    |
|        OwnableUpgradeable.__gap       |                 uint256[49]                 |  52  |   0    |
| Ownable2StepUpgradeable._pendingOwner |                   address                   | 101  |   0    |
|     Ownable2StepUpgradeable.__gap     |                 uint256[49]                 | 102  |   0    |
|       xERC20BridgeAdapter.xERC20      |                   IXERC20                   | 151  |   0    |
|  WormholeTrustedSender.trustedSenders | mapping(uint16 => EnumerableSet.Bytes32Set) | 152  |   0    |
|     WormholeBridgeAdapter.gasLimit    |                    uint96                   | 153  |   0    |
| WormholeBridgeAdapter.wormholeRelayer |               IWormholeRelayer              | 153  |   12   |
| WormholeBridgeAdapter.processedNonces |           mapping(bytes32 => bool)          | 154  |   0    |
|  WormholeBridgeAdapter.targetAddress  |          mapping(uint16 => address)         | 155  |   0    |
|    WormholeUnwrapperAdapter.lockbox   |                   address                   | 156  |   0    |
+---------------------------------------+---------------------------------------------+------+--------+

Original Wormhole Bridge Adapter

slither src/xWELL/WormholeBridgeAdapter.sol  --print variable-order  --solc-remaps '@openzeppelin-contracts/=lib/openzeppelin-contracts/ @OpenZeppelin Defender/=lib/openzeppelin-contracts/ @openzeppelin-contracts-upgradeable/=lib/openzeppelin-contracts-upgradeable/ @protocol=src/ @proposals=src/proposals/'

WormholeBridgeAdapter:
+---------------------------------------+---------------------------------------------+------+--------+
|                  Name                 |                     Type                    | Slot | Offset |
+---------------------------------------+---------------------------------------------+------+--------+
|       Initializable._initialized      |                    uint8                    |  0   |   0    |
|      Initializable._initializing      |                     bool                    |  0   |   1    |
|        ContextUpgradeable.__gap       |                 uint256[50]                 |  1   |   0    |
|       OwnableUpgradeable._owner       |                   address                   |  51  |   0    |
|        OwnableUpgradeable.__gap       |                 uint256[49]                 |  52  |   0    |
| Ownable2StepUpgradeable._pendingOwner |                   address                   | 101  |   0    |
|     Ownable2StepUpgradeable.__gap     |                 uint256[49]                 | 102  |   0    |
|       xERC20BridgeAdapter.xERC20      |                   IXERC20                   | 151  |   0    |
|  WormholeTrustedSender.trustedSenders | mapping(uint16 => EnumerableSet.Bytes32Set) | 152  |   0    |
|     WormholeBridgeAdapter.gasLimit    |                    uint96                   | 153  |   0    |
| WormholeBridgeAdapter.wormholeRelayer |               IWormholeRelayer              | 153  |   12   |
| WormholeBridgeAdapter.processedNonces |           mapping(bytes32 => bool)          | 154  |   0    |
|  WormholeBridgeAdapter.targetAddress  |          mapping(uint16 => address)         | 155  |   0    |
+---------------------------------------+---------------------------------------------+------+--------+

Gas Costs

In order to ensure that the gas costs of the new logic contract are not significantly higher than the old logic contract, integration and unit tests were run to ensure the 300k gas limit was not breached, which would require changes on the base chain to the amount of gas needed.

On an unwrap transaction, the gas cost 167148 to mint new tokens on moonbeam on a chainforked integration test, so the gas costs are within the 300k limit.