Bridge.sol

// contracts/Bridge.sol
// SPDX-License-Identifier: Apache 2

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";

import "../libraries/external/BytesLib.sol";

import "./BridgeGetters.sol";
import "./BridgeSetters.sol";
import "./BridgeStructs.sol";
import "./BridgeGovernance.sol";

import "./token/Token.sol";
import "./token/TokenImplementation.sol";

contract Bridge is BridgeGovernance {
    using BytesLib for bytes;

    // Produce a AssetMeta message for a given token
    function attestToken(address tokenAddress, uint32 nonce) public payable returns (uint64 sequence){
        // decimals, symbol & token are not part of the core ERC20 token standard, so we need to support contracts that dont implement them
        (,bytes memory queriedDecimals) = tokenAddress.staticcall(abi.encodeWithSignature("decimals()"));
        (,bytes memory queriedSymbol) = tokenAddress.staticcall(abi.encodeWithSignature("symbol()"));
        (,bytes memory queriedName) = tokenAddress.staticcall(abi.encodeWithSignature("name()"));

        uint8 decimals = abi.decode(queriedDecimals, (uint8));

        string memory symbolString = abi.decode(queriedSymbol, (string));
        string memory nameString = abi.decode(queriedName, (string));

        bytes32 symbol;
        bytes32 name;
        assembly {
        // first 32 bytes hold string length
            symbol := mload(add(symbolString, 32))
            name := mload(add(nameString, 32))
        }

        BridgeStructs.AssetMeta memory meta = BridgeStructs.AssetMeta({
        payloadID : 2,
        // Address of the token. Left-zero-padded if shorter than 32 bytes
        tokenAddress : bytes32(uint256(uint160(tokenAddress))),
        // Chain ID of the token
        tokenChain : chainId(),
        // Number of decimals of the token (big-endian uint8)
        decimals : decimals,
        // Symbol of the token (UTF-8)
        symbol : symbol,
        // Name of the token (UTF-8)
        name : name
        });

        bytes memory encoded = encodeAssetMeta(meta);

        sequence = wormhole().publishMessage{
        value : msg.value
        }(nonce, encoded, 15);
    }

    function wrapAndTransferETH(uint16 recipientChain, bytes32 recipient, uint256 arbiterFee, uint32 nonce) public payable returns (uint64 sequence) {
        uint wormholeFee = wormhole().messageFee();

        require(wormholeFee < msg.value, "value is smaller than wormhole fee");

        uint amount = msg.value - wormholeFee;

        require(arbiterFee <= amount, "fee is bigger than amount minus wormhole fee");

        uint normalizedAmount = amount / (10 ** 10);
        uint normalizedArbiterFee = arbiterFee / (10 ** 10);

        // refund dust
        uint dust = amount - (normalizedAmount * (10 ** 10));
        if (dust > 0) {
            payable(msg.sender).transfer(dust);
        }

        // deposit into WETH
        WETH().deposit{
        value : amount - dust
        }();

        // track and check outstanding token amounts
        bridgeOut(address(WETH()), normalizedAmount);

        sequence = logTransfer(chainId(), bytes32(uint256(uint160(address(WETH())))), normalizedAmount, recipientChain, recipient, normalizedArbiterFee, wormholeFee, nonce);
    }

    // Initiate a Transfer
    function transferTokens(address token, uint256 amount, uint16 recipientChain, bytes32 recipient, uint256 arbiterFee, uint32 nonce) public payable returns (uint64 sequence) {
        // determine token parameters
        uint16 tokenChain;
        bytes32 tokenAddress;
        if (isWrappedAsset(token)) {
            tokenChain = TokenImplementation(token).chainId();
            tokenAddress = TokenImplementation(token).nativeContract();
        } else {
            tokenChain = chainId();
            tokenAddress = bytes32(uint256(uint160(token)));
        }

        // query tokens decimals
        (,bytes memory queriedDecimals) = token.staticcall(abi.encodeWithSignature("decimals()"));
        uint8 decimals = abi.decode(queriedDecimals, (uint8));

        // adjust decimals
        uint256 normalizedAmount = amount;
        uint256 normalizedArbiterFee = arbiterFee;
        if (decimals > 8) {
            uint multiplier = 10 ** (decimals - 8);

            normalizedAmount /= multiplier;
            normalizedArbiterFee /= multiplier;

            // don't deposit dust that can not be bridged due to the decimal shift
            amount = normalizedAmount * multiplier;
        }

        if (tokenChain == chainId()) {
            SafeERC20.safeTransferFrom(IERC20(token), msg.sender, address(this), amount);

            // track and check outstanding token amounts
            bridgeOut(token, normalizedAmount);
        } else {
            SafeERC20.safeTransferFrom(IERC20(token), msg.sender, address(this), amount);

            TokenImplementation(token).burn(address(this), amount);
        }

        sequence = logTransfer(tokenChain, tokenAddress, normalizedAmount, recipientChain, recipient, normalizedArbiterFee, msg.value, nonce);
    }

    function logTransfer(uint16 tokenChain, bytes32 tokenAddress, uint256 amount, uint16 recipientChain, bytes32 recipient, uint256 fee, uint256 callValue, uint32 nonce) internal returns (uint64 sequence) {
        require(fee <= amount, "fee exceeds amount");

        BridgeStructs.Transfer memory transfer = BridgeStructs.Transfer({
        payloadID : 1,
        amount : amount,
        tokenAddress : tokenAddress,
        tokenChain : tokenChain,
        to : recipient,
        toChain : recipientChain,
        fee : fee
        });

        bytes memory encoded = encodeTransfer(transfer);

        sequence = wormhole().publishMessage{
        value : callValue
        }(nonce, encoded, 15);
    }

    function updateWrapped(bytes memory encodedVm) external returns (address token) {
        (IWormhole.VM memory vm, bool valid, string memory reason) = wormhole().parseAndVerifyVM(encodedVm);

        require(valid, reason);
        require(verifyBridgeVM(vm), "invalid emitter");

        BridgeStructs.AssetMeta memory meta = parseAssetMeta(vm.payload);
        return _updateWrapped(meta, vm.sequence);
    }

    function _updateWrapped(BridgeStructs.AssetMeta memory meta, uint64 sequence) internal returns (address token) {
        address wrapped = wrappedAsset(meta.tokenChain, meta.tokenAddress);
        require(wrapped != address(0), "wrapped asset does not exists");

        // Update metadata
        TokenImplementation(wrapped).updateDetails(bytes32ToString(meta.name), bytes32ToString(meta.symbol), sequence);

        return wrapped;
    }

    function createWrapped(bytes memory encodedVm) external returns (address token) {
        (IWormhole.VM memory vm, bool valid, string memory reason) = wormhole().parseAndVerifyVM(encodedVm);

        require(valid, reason);
        require(verifyBridgeVM(vm), "invalid emitter");

        BridgeStructs.AssetMeta memory meta = parseAssetMeta(vm.payload);
        return _createWrapped(meta, vm.sequence);
    }

    // Creates a wrapped asset using AssetMeta
    function _createWrapped(BridgeStructs.AssetMeta memory meta, uint64 sequence) internal returns (address token) {
        require(meta.tokenChain != chainId(), "can only wrap tokens from foreign chains");
        require(wrappedAsset(meta.tokenChain, meta.tokenAddress) == address(0), "wrapped asset already exists");

        // initialize the TokenImplementation
        bytes memory initialisationArgs = abi.encodeWithSelector(
            TokenImplementation.initialize.selector,
            bytes32ToString(meta.name),
            bytes32ToString(meta.symbol),
            meta.decimals,
            sequence,

            address(this),

            meta.tokenChain,
            meta.tokenAddress
        );

        // initialize the BeaconProxy
        bytes memory constructorArgs = abi.encode(address(this), initialisationArgs);

        // deployment code
        bytes memory bytecode = abi.encodePacked(type(BridgeToken).creationCode, constructorArgs);

        bytes32 salt = keccak256(abi.encodePacked(meta.tokenChain, meta.tokenAddress));

        assembly {
            token := create2(0, add(bytecode, 0x20), mload(bytecode), salt)

            if iszero(extcodesize(token)) {
                revert(0, 0)
            }
        }

        setWrappedAsset(meta.tokenChain, meta.tokenAddress, token);
    }

    function completeTransfer(bytes memory encodedVm) public {
        _completeTransfer(encodedVm, false);
    }

    function completeTransferAndUnwrapETH(bytes memory encodedVm) public {
        _completeTransfer(encodedVm, true);
    }

    // Execute a Transfer message
    function _completeTransfer(bytes memory encodedVm, bool unwrapWETH) internal {
        (IWormhole.VM memory vm, bool valid, string memory reason) = wormhole().parseAndVerifyVM(encodedVm);

        require(valid, reason);
        require(verifyBridgeVM(vm), "invalid emitter");

        BridgeStructs.Transfer memory transfer = parseTransfer(vm.payload);

        require(!isTransferCompleted(vm.hash), "transfer already completed");
        setTransferCompleted(vm.hash);

        require(transfer.toChain == chainId(), "invalid target chain");

        IERC20 transferToken;
        if (transfer.tokenChain == chainId()) {
            transferToken = IERC20(address(uint160(uint256(transfer.tokenAddress))));

            // track outstanding token amounts
            bridgedIn(address(transferToken), transfer.amount);
        } else {
            address wrapped = wrappedAsset(transfer.tokenChain, transfer.tokenAddress);
            require(wrapped != address(0), "no wrapper for this token created yet");

            transferToken = IERC20(wrapped);
        }

        require(unwrapWETH == false || address(transferToken) == address(WETH()), "invalid token, can only unwrap WETH");

        // query decimals
        (,bytes memory queriedDecimals) = address(transferToken).staticcall(abi.encodeWithSignature("decimals()"));
        uint8 decimals = abi.decode(queriedDecimals, (uint8));

        // adjust decimals
        uint256 nativeAmount = transfer.amount;
        uint256 nativeFee = transfer.fee;
        if (decimals > 8) {
            uint multiplier = 10 ** (decimals - 8);
            nativeAmount *= multiplier;
            nativeFee *= multiplier;
        }

        // transfer fee to arbiter
        if (nativeFee > 0) {
            require(nativeFee <= nativeAmount, "fee higher than transferred amount");

            if (unwrapWETH) {
                WETH().withdraw(nativeFee);

                payable(msg.sender).transfer(nativeFee);
            } else {
                if (transfer.tokenChain != chainId()) {
                    // mint wrapped asset
                    TokenImplementation(address(transferToken)).mint(msg.sender, nativeFee);
                } else {
                    SafeERC20.safeTransfer(transferToken, msg.sender, nativeFee);
                }
            }
        }

        // transfer bridged amount to recipient
        uint transferAmount = nativeAmount - nativeFee;
        address transferRecipient = address(uint160(uint256(transfer.to)));

        if (unwrapWETH) {
            WETH().withdraw(transferAmount);

            payable(transferRecipient).transfer(transferAmount);
        } else {
            if (transfer.tokenChain != chainId()) {
                // mint wrapped asset
                TokenImplementation(address(transferToken)).mint(transferRecipient, transferAmount);
            } else {
                SafeERC20.safeTransfer(transferToken, transferRecipient, transferAmount);
            }
        }
    }

    function bridgeOut(address token, uint normalizedAmount) internal {
        uint outstanding = outstandingBridged(token);
        require(outstanding + normalizedAmount <= type(uint64).max, "transfer exceeds max outstanding bridged token amount");
        setOutstandingBridged(token, outstanding + normalizedAmount);
    }

    function bridgedIn(address token, uint normalizedAmount) internal {
        setOutstandingBridged(token, outstandingBridged(token) - normalizedAmount);
    }

    function verifyBridgeVM(IWormhole.VM memory vm) internal view returns (bool){
        if (bridgeContracts(vm.emitterChainId) == vm.emitterAddress) {
            return true;
        }

        return false;
    }

    function encodeAssetMeta(BridgeStructs.AssetMeta memory meta) public pure returns (bytes memory encoded) {
        encoded = abi.encodePacked(
            meta.payloadID,
            meta.tokenAddress,
            meta.tokenChain,
            meta.decimals,
            meta.symbol,
            meta.name
        );
    }

    function encodeTransfer(BridgeStructs.Transfer memory transfer) public pure returns (bytes memory encoded) {
        encoded = abi.encodePacked(
            transfer.payloadID,
            transfer.amount,
            transfer.tokenAddress,
            transfer.tokenChain,
            transfer.to,
            transfer.toChain,
            transfer.fee
        );
    }

    function parseAssetMeta(bytes memory encoded) public pure returns (BridgeStructs.AssetMeta memory meta) {
        uint index = 0;

        meta.payloadID = encoded.toUint8(index);
        index += 1;

        require(meta.payloadID == 2, "invalid AssetMeta");

        meta.tokenAddress = encoded.toBytes32(index);
        index += 32;

        meta.tokenChain = encoded.toUint16(index);
        index += 2;

        meta.decimals = encoded.toUint8(index);
        index += 1;

        meta.symbol = encoded.toBytes32(index);
        index += 32;

        meta.name = encoded.toBytes32(index);
        index += 32;

        require(encoded.length == index, "invalid AssetMeta");
    }

    function parseTransfer(bytes memory encoded) public pure returns (BridgeStructs.Transfer memory transfer) {
        uint index = 0;

        transfer.payloadID = encoded.toUint8(index);
        index += 1;

        require(transfer.payloadID == 1, "invalid Transfer");

        transfer.amount = encoded.toUint256(index);
        index += 32;

        transfer.tokenAddress = encoded.toBytes32(index);
        index += 32;

        transfer.tokenChain = encoded.toUint16(index);
        index += 2;

        transfer.to = encoded.toBytes32(index);
        index += 32;

        transfer.toChain = encoded.toUint16(index);
        index += 2;

        transfer.fee = encoded.toUint256(index);
        index += 32;

        require(encoded.length == index, "invalid Transfer");
    }

    function bytes32ToString(bytes32 input) internal pure returns (string memory) {
        uint256 i;
        while (i < 32 && input[i] != 0) {
            i++;
        }
        bytes memory array = new bytes(i);
        for (uint c = 0; c < i; c++) {
            array[c] = input[c];
        }
        return string(array);
    }

    // we need to accept ETH sends to unwrap WETH
    receive() external payable {}
}