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L2WormholeGateway

IWormholeTokenBridge

Wormhole Token Bridge interface. Contains only selected functions used by L2WormholeGateway.

completeTransferWithPayload

function completeTransferWithPayload(bytes encodedVm) external returns (bytes)

parseTransferWithPayload

function parseTransferWithPayload(bytes encoded) external pure returns (struct IWormholeTokenBridge.TransferWithPayload transfer)

transferTokens

function transferTokens(address token, uint256 amount, uint16 recipientChain, bytes32 recipient, uint256 arbiterFee, uint32 nonce) external payable returns (uint64 sequence)

transferTokensWithPayload

function transferTokensWithPayload(address token, uint256 amount, uint16 recipientChain, bytes32 recipient, uint32 nonce, bytes payload) external payable returns (uint64 sequence)

TransferWithPayload

struct TransferWithPayload {
  uint8 payloadID;
  uint256 amount;
  bytes32 tokenAddress;
  uint16 tokenChain;
  bytes32 to;
  uint16 toChain;
  bytes32 fromAddress;
  bytes payload;
}

L2WormholeGateway

Selected cross-ecosystem bridges are given the minting authority for tBTC token on L2 and sidechains. This contract gives a minting authority to the Wormhole Bridge.

The process of bridging from L1 to L2 (or sidechain) looks as follows:

  1. There is a tBTC holder on L1. The holder goes to the Wormhole Portal and selects the chain they want to bridge to.

  2. The holder submits one transaction to L1 locking their tBTC tokens in the bridge’s smart contract. After the transaction is mined, they wait about 15 minutes for the Ethereum block finality.

  3. The holder submits one transaction to L2 that is minting tokens. After that transaction is mined, they have their tBTC on L2.

The process of bridging from L2 (or sidechain) to L1 looks as follows:

  1. There is a tBTC holder on L2. That holder goes to the Wormhole Portal and selects one of the L2 chains they want to bridge from.

  2. The holder submits one transaction to L2 that is burning the token. After the transaction is mined, they wait about 15 minutes for the L2 block finality.

  3. The holder submits one transaction to L1 unlocking their tBTC tokens from the bridge’s smart contract. After that transaction is mined, they have their tBTC on L1.

This smart contract is integrated with step 3 of L1->L2 bridging and step 1 of L2->L1 or L2->L2 bridging. When the user redeems token on L2, this contract receives the Wormhole tBTC representation and mints the canonical tBTC in an equal amount. When user sends their token from L1, this contract burns the canonical tBTC and sends Wormhole tBTC representation through the bridge in an equal amount.

This contract is supposed to be deployed behind a transparent upgradeable proxy.

bridge

contract IWormholeTokenBridge bridge

Reference to the Wormhole Token Bridge contract.

bridgeToken

contract IERC20Upgradeable bridgeToken

Wormhole tBTC token representation.

tbtc

contract L2TBTC tbtc

Canonical tBTC token.

gateways

mapping(uint16 => bytes32) gateways

Maps Wormhole chain ID to the Wormhole tBTC gateway address on that chain. For example, this chain's ID should be mapped to this contract's address. If there is no Wormhole tBTC gateway address on the given chain, there is no entry in this mapping. The mapping holds addresses in a Wormhole-specific format, where Ethereum address is left-padded with zeros.

mintingLimit

uint256 mintingLimit

Minting limit for this gateway. Useful for early days of testing the system. The gateway can not mint more canonical tBTC than this limit.

mintedAmount

uint256 mintedAmount

The amount of tBTC minted by this contract. tBTC burned by this contract decreases this amount.

WormholeTbtcReceived

event WormholeTbtcReceived(address receiver, uint256 amount)

WormholeTbtcSent

event WormholeTbtcSent(uint256 amount, uint16 recipientChain, bytes32 gateway, bytes32 recipient, uint256 arbiterFee, uint32 nonce)

WormholeTbtcDeposited

event WormholeTbtcDeposited(address depositor, uint256 amount)

GatewayAddressUpdated

event GatewayAddressUpdated(uint16 chainId, bytes32 gateway)

MintingLimitUpdated

event MintingLimitUpdated(uint256 mintingLimit)

initialize

function initialize(contract IWormholeTokenBridge _bridge, contract IERC20Upgradeable _bridgeToken, contract L2TBTC _tbtc) external

sendTbtc

function sendTbtc(uint256 amount, uint16 recipientChain, bytes32 recipient, uint256 arbiterFee, uint32 nonce) external payable returns (uint64)

This function is called when the user sends their token from L2. The contract burns the canonical tBTC from the user and sends wormhole tBTC representation over the bridge. Keep in mind that when multiple bridges receive a minting authority on the canonical tBTC, this function may not be able to send all amounts of tBTC through the Wormhole bridge. The capability of Wormhole Bridge to send tBTC from the chain is limited to the amount of tBTC bridged through Wormhole to that chain.

Requirements:

  • The sender must have at least amount of the canonical tBTC and it has to be approved for L2WormholeGateway.

  • The L2WormholeGateway must have at least amount of the wormhole tBTC.

  • The recipient must not be 0x0.

  • The amount to transfer must not be 0,

  • The amount to transfer must be >= 10^10 (1e18 precision). Depending if Wormhole tBTC gateway is registered on the target chain, this function uses transfer or transfer with payload over the Wormhole bridge.

Parameters

Name
Type
Description

amount

uint256

The amount of tBTC to be sent.

recipientChain

uint16

The Wormhole recipient chain ID.

recipient

bytes32

The address of the recipient in the Wormhole format.

arbiterFee

uint256

The Wormhole arbiter fee. Ignored if sending tBTC to chain with Wormhole tBTC gateway.

nonce

uint32

The Wormhole nonce used to batch messages together.

Return Values

Name
Type
Description

[0]

uint64

The Wormhole sequence number.

receiveTbtc

function receiveTbtc(bytes encodedVm) external

This function is called when the user redeems their token on L2. The contract receives Wormhole tBTC representation and mints the canonical tBTC for the user. If the tBTC minting limit has been reached by this contract, instead of minting tBTC the receiver address receives Wormhole tBTC representation.

Requirements:

  • The receiver of Wormhole tBTC should be the L2WormholeGateway contract.

  • The receiver of the canonical tBTC should be abi-encoded in the payload.

  • The receiver of the canonical tBTC must not be the zero address. The Wormhole Token Bridge contract has protection against redeeming the same VAA again. When a Token Bridge VAA is redeemed, its message body hash is stored in a map. This map is used to check whether the hash has already been set in this map. For this reason, this function does not have to be nonReentrant.

Parameters

Name
Type
Description

encodedVm

bytes

A byte array containing a Wormhole VAA signed by the guardians.

depositWormholeTbtc

function depositWormholeTbtc(uint256 amount) external

Allows to deposit Wormhole tBTC token in exchange for canonical tBTC. Useful in a situation when user received wormhole tBTC instead of canonical tBTC. One example of such situation is when the minting limit was exceeded but the user minted anyway.

Requirements:

  • The sender must have at least amount of the Wormhole tBTC and it has to be approved for L2WormholeGateway.

  • The minting limit must allow for minting the given amount.

Parameters

Name
Type
Description

amount

uint256

The amount of Wormhole tBTC to deposit.

updateGatewayAddress

function updateGatewayAddress(uint16 chainId, bytes32 gateway) external

Lets the governance to update the tBTC gateway address on the chain with the given Wormhole ID.

Use toWormholeAddress function to convert between Ethereum and Wormhole address formats.

Parameters

Name
Type
Description

chainId

uint16

Wormhole ID of the chain.

gateway

bytes32

Address of tBTC gateway on the given chain in a Wormhole format.

updateMintingLimit

function updateMintingLimit(uint256 _mintingLimit) external

Lets the governance to update the tBTC minting limit for this contract.

Parameters

Name
Type
Description

_mintingLimit

uint256

The new minting limit.

toWormholeAddress

function toWormholeAddress(address _address) external pure returns (bytes32)

Converts Ethereum address into Wormhole format.

Parameters

Name
Type
Description

_address

address

The address to convert.

fromWormholeAddress

function fromWormholeAddress(bytes32 _address) public pure returns (address)

Converts Wormhole address into Ethereum format.

Parameters

Name
Type
Description

_address

bytes32

The address to convert.

normalize

function normalize(uint256 amount) internal pure returns (uint256)

Eliminates the dust that cannot be bridged with Wormhole due to the decimal shift in the Wormhole Bridge contract. See https://github.com/wormhole-foundation/wormhole/blob/96682bdbeb7c87bfa110eade0554b3d8cbf788d2/ethereum/contracts/bridge/Bridge.sol#L276-L288

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