二层网络 Optimism 智能合约要点解析

/**
 * @title L1StandardBridge
 * @dev The L1 ETH and ERC20 Bridge is a contract which stores deposited L1 funds and standard
 * tokens that are in use on L2. It synchronizes a corresponding L2 Bridge, informing it of deposits
 * and listening to it for newly finalized withdrawals.
 *
 */
contract L1StandardBridge is IL1StandardBridge, CrossDomainEnabled {
    function depositETHTo(
        address _to,
        uint32 _l2Gas,
        bytes calldata _data
    ) external payable {
        _initiateETHDeposit(msg.sender, _to, _l2Gas, _data);
    }

    /**
     * @dev Performs the logic for deposits by storing the ETH and informing the L2 ETH Gateway of
     * the deposit.
     * @param _from Account to pull the deposit from on L1.
     * @param _to Account to give the deposit to on L2.
     * @param _l2Gas Gas limit required to complete the deposit on L2.
     * @param _data Optional data to forward to L2. This data is provided
     *        solely as a convenience for external contracts. Aside from enforcing a maximum
     *        length, these contracts provide no guarantees about its content.
     */
    function _initiateETHDeposit(
        address _from,
        address _to,
        uint32 _l2Gas,
        bytes memory _data
    ) internal {
        // Construct calldata for finalizeDeposit call
        bytes memory message = abi.encodeWithSelector(
            IL2ERC20Bridge.finalizeDeposit.selector,
            address(0),
            Lib_PredeployAddresses.OVM_ETH,
            _from,
            _to,
            msg.value,
            _data
        );
        // Send calldata into L2
        // slither-disable-next-line reentrancy-events
        sendCrossDomainMessage(l2TokenBridge, _l2Gas, message);
        // slither-disable-next-line reentrancy-events
        emit ETHDepositInitiated(_from, _to, msg.value, _data);
    }

    // ... other functions (OMITTED)
}

/**
 * @title L2StandardBridge
 * @dev The L2 Standard bridge is a contract which works together with the L1 Standard bridge to
 * enable ETH and ERC20 transitions between L1 and L2.
 * This contract acts as a minter for new tokens when it hears about deposits into the L1 Standard
 * bridge.
 * This contract also acts as a burner of the tokens intended for withdrawal, informing the L1
 * bridge to release L1 funds.
 */
contract L2StandardBridge is IL2ERC20Bridge, CrossDomainEnabled {
    function finalizeDeposit(
        address _l1Token,
        address _l2Token,
        address _from,
        address _to,
        uint256 _amount,
        bytes calldata _data
    ) external virtual onlyFromCrossDomainAccount(l1TokenBridge) {
        // Check the target token is compliant and
        // verify the deposited token on L1 matches the L2 deposited token representation here
        if (
            // slither-disable-next-line reentrancy-events
            ERC165Checker.supportsInterface(_l2Token, 0x1d1d8b63) &&
            _l1Token == IL2StandardERC20(_l2Token).l1Token()
        ) {
            // When a deposit is finalized, we credit the account on L2 with the same amount of
            // tokens.
            // slither-disable-next-line reentrancy-events
            IL2StandardERC20(_l2Token).mint(_to, _amount);
            // slither-disable-next-line reentrancy-events
            emit DepositFinalized(_l1Token, _l2Token, _from, _to, _amount, _data);
        } else {
            // ... handle error (OMITTED)
        }
    }

    // ... other functions (OMITTED)
}

/**
 * @title CanonicalTransactionChain
 * @dev The Canonical Transaction Chain (CTC) contract is an append-only log of transactions
 * which must be applied to the rollup state. It defines the ordering of rollup transactions by
 * writing them to the 'CTC:batches' instance of the Chain Storage Container.
 * The CTC also allows any account to 'enqueue' an L2 transaction, which will require that the
 * Sequencer will eventually append it to the rollup state.
 *
 */
contract CanonicalTransactionChain is ICanonicalTransactionChain, Lib_AddressResolver {
    uint40 private _nextQueueIndex; // index of the first queue element not yet included
    Lib_OVMCodec.QueueElement[] queueElements;

    /**
     * Adds a transaction to the queue.
     * @param _target Target L2 contract to send the transaction to.
     * @param _gasLimit Gas limit for the enqueued L2 transaction.
     * @param _data Transaction data.
     */
    function enqueue(
        address _target,
        uint256 _gasLimit,
        bytes memory _data
    ) external {
        // ...a bunch of unimportant stuff omitted

        bytes32 transactionHash = keccak256(abi.encode(sender, _target, _gasLimit, _data));

        queueElements.push(
            Lib_OVMCodec.QueueElement({
                transactionHash: transactionHash,
                timestamp: uint40(block.timestamp),
                blockNumber: uint40(block.number)
            })
        );
        uint256 queueIndex = queueElements.length - 1;
        emit TransactionEnqueued(sender, _target, _gasLimit, _data, queueIndex, block.timestamp);
    }
}

/**
 * @title CanonicalTransactionChain
 * @dev The Canonical Transaction Chain (CTC) contract is an append-only log of transactions
 * which must be applied to the rollup state. It defines the ordering of rollup transactions by
 * writing them to the 'CTC:batches' instance of the Chain Storage Container.
 * The CTC also allows any account to 'enqueue' an L2 transaction, which will require that the
 * Sequencer will eventually append it to the rollup state.
 *
 */
contract CanonicalTransactionChain is ICanonicalTransactionChain, Lib_AddressResolver {
    /**
     * Inserts a batch into the chain of batches.
     * @param _transactionRoot Root of the transaction tree for this batch.
     * @param _batchSize Number of elements in the batch.
     * @param _numQueuedTransactions Number of queue transactions in the batch.
     * @param _timestamp The latest batch timestamp.
     * @param _blockNumber The latest batch blockNumber.
     */
    function _appendBatch(
        bytes32 _transactionRoot,
        uint256 _batchSize,
        uint256 _numQueuedTransactions,
        uint40 _timestamp,
        uint40 _blockNumber
    ) internal {
        IChainStorageContainer batchesRef = batches();
        (uint40 totalElements, uint40 nextQueueIndex, , ) = _getBatchExtraData();

        Lib_OVMCodec.ChainBatchHeader memory header = Lib_OVMCodec.ChainBatchHeader({
            batchIndex: batchesRef.length(),
            batchRoot: _transactionRoot,
            batchSize: _batchSize,
            prevTotalElements: totalElements,
            extraData: hex""
        });

        emit TransactionBatchAppended(
            header.batchIndex,
            header.batchRoot,
            header.batchSize,
            header.prevTotalElements,
            header.extraData
        );

        bytes32 batchHeaderHash = Lib_OVMCodec.hashBatchHeader(header);
        bytes27 latestBatchContext = _makeBatchExtraData(
            totalElements + uint40(header.batchSize),
            nextQueueIndex + uint40(_numQueuedTransactions),
            _timestamp,
            _blockNumber
        );

        // slither-disable-next-line reentrancy-no-eth, reentrancy-events
        batchesRef.push(batchHeaderHash, latestBatchContext);
    }
}

contract OVM_FraudVerifier is Lib_AddressResolver, OVM_FraudContributor, iOVM_FraudVerifier {
    /**
     * Finalizes the fraud verification process.
     * @param _preStateRoot State root before the fraudulent transaction.
     * @param _preStateRootBatchHeader Batch header for the provided pre-state root.
     * @param _preStateRootProof Inclusion proof for the provided pre-state root.
     * @param _txHash The transaction for the state root
     * @param _postStateRoot State root after the fraudulent transaction.
     * @param _postStateRootBatchHeader Batch header for the provided post-state root.
     * @param _postStateRootProof Inclusion proof for the provided post-state root.
     */
    function finalizeFraudVerification(
        bytes32 _preStateRoot,
        Lib_OVMCodec.ChainBatchHeader memory _preStateRootBatchHeader,
        Lib_OVMCodec.ChainInclusionProof memory _preStateRootProof,
        bytes32 _txHash,
        bytes32 _postStateRoot,
        Lib_OVMCodec.ChainBatchHeader memory _postStateRootBatchHeader,
        Lib_OVMCodec.ChainInclusionProof memory _postStateRootProof
    )
        override
        public
        contributesToFraudProof(_preStateRoot, _txHash)
    {
        iOVM_StateTransitioner transitioner = getStateTransitioner(_preStateRoot, _txHash);

        // ... a bunch of require statements omitted

        // If the post state root did not match, then there was fraud and we should delete the batch
        require(
            _postStateRoot != transitioner.getPostStateRoot(),
            "State transition has not been proven fraudulent."
        );

        _cancelStateTransition(_postStateRootBatchHeader, _preStateRoot);

        // TEMPORARY: Remove the transitioner; for minnet.
        transitioners[keccak256(abi.encodePacked(_preStateRoot, _txHash))] = iOVM_StateTransitioner(0x0000000000000000000000000000000000000000);

        emit FraudProofFinalized(
            _preStateRoot,
            _preStateRootProof.index,
            _txHash,
            msg.sender
        );
    }

    /**
     * Removes a state transition from the state commitment chain.
     * @param _postStateRootBatchHeader Header for the post-state root.
     * @param _preStateRoot Pre-state root hash.
     */
    function _cancelStateTransition(
        Lib_OVMCodec.ChainBatchHeader memory _postStateRootBatchHeader,
        bytes32 _preStateRoot
    )
        internal
    {
        iOVM_StateCommitmentChain ovmStateCommitmentChain = iOVM_StateCommitmentChain(resolve("OVM_StateCommitmentChain"));
        iOVM_BondManager ovmBondManager = iOVM_BondManager(resolve("OVM_BondManager"));

        // Delete the state batch.
        ovmStateCommitmentChain.deleteStateBatch(
            _postStateRootBatchHeader
        );

        // Get the timestamp and publisher for that block.
        (uint256 timestamp, address publisher) = abi.decode(_postStateRootBatchHeader.extraData, (uint256, address));

        // Slash the bonds at the bond manager.
        ovmBondManager.finalize(
            _preStateRoot,
            publisher,
            timestamp
        );
    }
}