ఆప్టిమిజం స్టాండర్డ్ బ్రిడ్జ్ కాంట్రాక్ట్ విశ్లేషణ

/**
 * @title IL1ERC20Bridge
 */
interface IL1ERC20Bridge {
    /**********
     * Events *
     **********/

    event ERC20DepositInitiated(

    /********************
     * Public Functions *
     ********************/

    /**
     * @dev get the address of the corresponding L2 bridge contract.
     * @return Address of the corresponding L2 bridge contract.
     */
    function l2TokenBridge() external returns (address);

    /**
     * @dev deposit an amount of the ERC20 to the caller's balance on L2.
     * @param _l1Token Address of the L1 ERC20 we are depositing
     * @param _l2Token Address of the L1 respective L2 ERC20
     * @param _amount Amount of the ERC20 to deposit
     * @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 depositERC20(
        address _l1Token,
        address _l2Token,
        uint256 _amount,
        uint32 _l2Gas,
        bytes calldata _data
    ) external;

    /**
     * @dev deposit an amount of ERC20 to a recipient's balance on L2.
     * @param _l1Token Address of the L1 ERC20 we are depositing
     * @param _l2Token Address of the L1 respective L2 ERC20
     * @param _to L2 address to credit the withdrawal to.
     * @param _amount Amount of the ERC20 to deposit.
     * @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 depositERC20To(
        address _l1Token,
        address _l2Token,
        address _to,
        uint256 _amount,
        uint32 _l2Gas,
        bytes calldata _data
    ) external;

    /*************************
     * Cross-chain Functions *
     *************************/

    /**
     * @dev Complete a withdrawal from L2 to L1, and credit funds to the recipient's balance of the
     * L1 ERC20 token.
     * This call will fail if the initialized withdrawal from L2 has not been finalized.
     *
     * @param _l1Token Address of L1 token to finalizeWithdrawal for.
     * @param _l2Token Address of L2 token where withdrawal was initiated.
     * @param _from L2 address initiating the transfer.
     * @param _to L1 address to credit the withdrawal to.
     * @param _amount Amount of the ERC20 to deposit.
     * @param _data Data provided by the sender on 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 finalizeERC20Withdrawal(
        address _l1Token,
        address _l2Token,
        address _from,
        address _to,
        uint256 _amount,
        bytes calldata _data
    ) external;
}

// SPDX-License-Identifier: MIT
pragma solidity >0.5.0 <0.9.0;

import "./IL1ERC20Bridge.sol";

/**
 * @title IL1StandardBridge
 */
interface IL1StandardBridge is IL1ERC20Bridge {
    /**********
     * Events *
     **********/
    event ETHDepositInitiated(
        address indexed _from,
        address indexed _to,
        uint256 _amount,
        bytes _data
    );

    event ETHWithdrawalFinalized(
        .
        .
        .
    );

    /********************
     * Public Functions *
     ********************/

    /**
     * @dev Deposit an amount of the ETH to the caller's balance on L2.
            .
            .
            .
     */
    function depositETH(uint32 _l2Gas, bytes calldata _data) external payable;

    /**
     * @dev Deposit an amount of ETH to a recipient's balance on L2.
            .
            .
            .
     */
    function depositETHTo(
        address _to,
        uint32 _l2Gas,
        bytes calldata _data
    ) external payable;

    /*************************
     * Cross-chain Functions *
     *************************/

    /**
     * @dev Complete a withdrawal from L2 to L1, and credit funds to the recipient's balance of the
     * L1 ETH token. Since only the xDomainMessenger can call this function, it will never be called
     * before the withdrawal is finalized.
                .
                .
                .
     */
    function finalizeETHWithdrawal(
        address _from,
        address _to,
        uint256 _amount,
        bytes calldata _data
    ) external;
}

/**
 * @title CrossDomainEnabled
 * @dev Helper contract for contracts performing cross-domain communications
 *
 * Compiler used: defined by inheriting contract
 */
contract CrossDomainEnabled {
    /*************
     * Variables *
     *************/

    // Messenger contract used to send and receive messages from the other domain.
    address public messenger;

    /***************
     * Constructor *
     ***************/

    /**
     * @param _messenger Address of the CrossDomainMessenger on the current layer.
     */
    constructor(address _messenger) {
        messenger = _messenger;
    }

    /**********************
     * Function Modifiers *
     **********************/

    /**
     * Enforces that the modified function is only callable by a specific cross-domain account.
     * @param _sourceDomainAccount The only account on the originating domain which is
     *  authenticated to call this function.
     */
    modifier onlyFromCrossDomainAccount(address _sourceDomainAccount) {

        _;
    }

    /**********************
     * Internal Functions *
     **********************/

    /**
     * Gets the messenger, usually from storage. This function is exposed in case a child contract
     * needs to override.
     * @return The address of the cross-domain messenger contract which should be used.
     */
    function getCrossDomainMessenger() internal virtual returns (ICrossDomainMessenger) {
        return ICrossDomainMessenger(messenger);
    }

    /**
     * Sends a message to an account on another domain
     * @param _crossDomainTarget The intended recipient on the destination domain
     * @param _message The data to send to the target (usually calldata to a function with
     *  `onlyFromCrossDomainAccount()`)
     * @param _gasLimit The gasLimit for the receipt of the message on the target domain.
     */
    function sendCrossDomainMessage(
        address _crossDomainTarget,
        uint32 _gasLimit,
        bytes memory _message

/**
 * @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 {
    using SafeERC20 for IERC20;

    /******************
     * Initialization *
     ******************/

    /**
     * @param _l1messenger L1 Messenger address being used for cross-chain communications.
     * @param _l2TokenBridge L2 standard bridge address.
     */
    // slither-disable-next-line external-function

    /**************
     * Depositing *
     **************/

    /** @dev Modifier requiring sender to be EOA.  This check could be bypassed by a malicious
     *  contract via initcode, but it takes care of the user error we want to avoid.
     */
    modifier onlyEOA() {
        // Used to stop deposits from contracts (avoid accidentally lost tokens)
        require(!Address.isContract(msg.sender), "Account not EOA");
        _;
    }

    /**
     * @dev This function can be called with no data
     * to deposit an amount of ETH to the caller's balance on L2.
     * Since the receive function doesn't take data, a conservative
     * default amount is forwarded to L2.
     */
    receive() external payable onlyEOA {
        _initiateETHDeposit(msg.sender, msg.sender, 200_000, bytes(""));
    }

    /**
     * @inheritdoc IL1StandardBridge
     */
    function depositETH(uint32 _l2Gas, bytes calldata _data) external payable onlyEOA {
        _initiateETHDeposit(msg.sender, msg.sender, _l2Gas, _data);
    }

    /**
     * @inheritdoc IL1StandardBridge
     */
    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(

    /**
     * @inheritdoc IL1ERC20Bridge
     */
    function depositERC20(
		.
		.
		.
    ) external virtual onlyEOA {
        _initiateERC20Deposit(_l1Token, _l2Token, msg.sender, msg.sender, _amount, _l2Gas, _data);
    }

    /**
     * @inheritdoc IL1ERC20Bridge
     */
    function depositERC20To(
		.
		.
		.
    ) external virtual {
        _initiateERC20Deposit(_l1Token, _l2Token, msg.sender, _to, _amount, _l2Gas, _data);
    }

    /**
     * @dev Performs the logic for deposits by informing the L2 Deposited Token
     * contract of the deposit and calling a handler to lock the L1 funds. (e.g., transferFrom)
     *
     * @param _l1Token Address of the L1 ERC20 we are depositing
     * @param _l2Token Address of the L1 respective L2 ERC20
     * @param _from Account to pull the deposit from on L1
     * @param _to Account to give the deposit to on L2
     * @param _amount Amount of the ERC20 to deposit.
     * @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 _initiateERC20Deposit(
        address _l1Token,
        address _l2Token,
        address _from,
        address _to,
        uint256 _amount,
        uint32 _l2Gas,
        bytes calldata _data
    ) internal {

        // Construct calldata for _l2Token.finalizeDeposit(_to, _amount)
        bytes memory message = abi.encodeWithSelector(
            IL2ERC20Bridge.finalizeDeposit.selector,
            _l1Token,
            _l2Token,
            _from,
            _to,
            _amount,
            _data
        );

        // Send calldata into L2
        // slither-disable-next-line reentrancy-events, reentrancy-benign
        sendCrossDomainMessage(l2TokenBridge, _l2Gas, message);

        // slither-disable-next-line reentrancy-benign
        deposits[_l1Token][_l2Token] = deposits[_l1Token][_l2Token] + _amount;

        // slither-disable-next-line reentrancy-events
        emit ERC20DepositInitiated(_l1Token, _l2Token, _from, _to, _amount, _data);
    }

    /*************************
     * Cross-chain Functions *
     *************************/

    /**
     * @inheritdoc IL1StandardBridge
     */
    function finalizeETHWithdrawal(
        address _from,
        address _to,
        uint256 _amount,
        bytes calldata _data

    }

    /**
     * @inheritdoc IL1ERC20Bridge
     */
    function finalizeERC20Withdrawal(
        address _l1Token,
        address _l2Token,
        address _from,
        address _to,
        uint256 _amount,
        bytes calldata _data
    ) external onlyFromCrossDomainAccount(l2TokenBridge) {

        // When a withdrawal is finalized on L1, the L1 Bridge transfers the funds to the withdrawer
        // slither-disable-next-line reentrancy-events
        IERC20(_l1Token).safeTransfer(_to, _amount);

        // slither-disable-next-line reentrancy-events
        emit ERC20WithdrawalFinalized(_l1Token, _l2Token, _from, _to, _amount, _data);
    }


    /*****************************
     * Temporary - Migrating ETH *
     *****************************/

    /**
     * @dev Adds ETH balance to the account. This is meant to allow for ETH
     * to be migrated from an old gateway to a new gateway.
     * NOTE: This is left for one upgrade only so we are able to receive the migrated ETH from the
     * old contract
     */
    function donateETH() external payable {}
}

    /**
     * @param _l2Bridge Address of the L2 standard bridge.
     * @param _l1Token Address of the corresponding L1 token.
     * @param _name ERC20 name.
     * @param _symbol ERC20 symbol.
     */
    constructor(
        address _l2Bridge,
        address _l1Token,
        string memory _name,
        string memory _symbol
    ) ERC20(_name, _symbol) {
        l1Token = _l1Token;
        l2Bridge = _l2Bridge;
    }

    modifier onlyL2Bridge() {
        require(msg.sender == l2Bridge, "Only L2 Bridge can mint and burn");
        _;
    }


    // slither-disable-next-line external-function
    function supportsInterface(bytes4 _interfaceId) public pure returns (bool) {
        bytes4 firstSupportedInterface = bytes4(keccak256("supportsInterface(bytes4)")); // ERC165
        bytes4 secondSupportedInterface = IL2StandardERC20.l1Token.selector ^
            IL2StandardERC20.mint.selector ^
            IL2StandardERC20.burn.selector;
        return _interfaceId == firstSupportedInterface || _interfaceId == secondSupportedInterface;
    }

    // slither-disable-next-line external-function
    function mint(address _to, uint256 _amount) public virtual onlyL2Bridge {
        _mint(_to, _amount);

        emit Mint(_to, _amount);
    }

    // slither-disable-next-line external-function
    function burn(address _from, uint256 _amount) public virtual onlyL2Bridge {
        _burn(_from, _amount);

        emit Burn(_from, _amount);
    }
}

/* Library Imports */
import { ERC165Checker } from "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";
import { CrossDomainEnabled } from "../../libraries/bridge/CrossDomainEnabled.sol";
import { Lib_PredeployAddresses } from "../../libraries/constants/Lib_PredeployAddresses.sol";

/* Contract Imports */
import { IL2StandardERC20 } from "../../standards/IL2StandardERC20.sol";

/**
 * @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 {
    /********************************
     * External Contract References *
     ********************************/

    address public l1TokenBridge;

    /***************
     * Constructor *
     ***************/

    /**
     * @param _l2CrossDomainMessenger Cross-domain messenger used by this contract.
     * @param _l1TokenBridge Address of the L1 bridge deployed to the main chain.
     */
    constructor(address _l2CrossDomainMessenger, address _l1TokenBridge)
        CrossDomainEnabled(_l2CrossDomainMessenger)
    {
        l1TokenBridge = _l1TokenBridge;
    }

    /***************
     * Withdrawing *
     ***************/

    /**
     * @inheritdoc IL2ERC20Bridge
     */
    function withdraw(
        address _l2Token,
        uint256 _amount,
        uint32 _l1Gas,
        bytes calldata _data
    ) external virtual {
        _initiateWithdrawal(_l2Token, msg.sender, msg.sender, _amount, _l1Gas, _data);
    }

    /**
     * @inheritdoc IL2ERC20Bridge
     */
    function withdrawTo(
        address _l2Token,
        address _to,
        uint256 _amount,
        uint32 _l1Gas,
        bytes calldata _data
    ) external virtual {
        _initiateWithdrawal(_l2Token, msg.sender, _to, _amount, _l1Gas, _data);
    }

    /**
     * @dev Performs the logic for withdrawals by burning the token and informing
     *      the L1 token Gateway of the withdrawal.
     * @param _l2Token Address of L2 token where withdrawal is initiated.
     * @param _from Account to pull the withdrawal from on L2.
     * @param _to Account to give the withdrawal to on L1.
     * @param _amount Amount of the token to withdraw.
     * @param _l1Gas Unused, but included for potential forward compatibility considerations.
     * @param _data Optional data to forward to L1. 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 _initiateWithdrawal(
        address _l2Token,
        address _from,
        address _to,
        uint256 _amount,
        uint32 _l1Gas,
        bytes calldata _data
    ) internal {
        // When a withdrawal is initiated, we burn the withdrawer's funds to prevent subsequent L2
        // usage
        // slither-disable-next-line reentrancy-events
        IL2StandardERC20(_l2Token).burn(msg.sender, _amount);

            message = abi.encodeWithSelector(
                IL1StandardBridge.finalizeETHWithdrawal.selector,
                _from,
                _to,
                _amount,
                _data
            );
        } else {
            message = abi.encodeWithSelector(
                IL1ERC20Bridge.finalizeERC20Withdrawal.selector,
                l1Token,
                _l2Token,
                _from,
                _to,
                _amount,
                _data
            );
        }

        // Send message up to L1 bridge
        // slither-disable-next-line reentrancy-events
        sendCrossDomainMessage(l1TokenBridge, _l1Gas, message);

        // slither-disable-next-line reentrancy-events
        emit WithdrawalInitiated(l1Token, _l2Token, msg.sender, _to, _amount, _data);
    }

    /************************************
     * Cross-chain Function: Depositing *
     ************************************/

    /**
     * @inheritdoc IL2ERC20Bridge
     */
    function finalizeDeposit(
        address _l1Token,
        address _l2Token,
        address _from,
        address _to,
        uint256 _amount,
        bytes calldata _data

        } else {
            // Either the L2 token which is being deposited-into disagrees about the correct address
            // of its L1 token, or does not support the correct interface.
            // This should only happen if there is a  malicious L2 token, or if a user somehow
            // specified the wrong L2 token address to deposit into.
            // In either case, we stop the process here and construct a withdrawal
            // message so that users can get their funds out in some cases.
            // There is no way to prevent malicious token contracts altogether, but this does limit
            // user error and mitigate some forms of malicious contract behavior.

            bytes memory message = abi.encodeWithSelector(
                IL1ERC20Bridge.finalizeERC20Withdrawal.selector,
                _l1Token,
                _l2Token,
                _to, // switched the _to and _from here to bounce back the deposit to the sender
                _from,
                _amount,
                _data
            );

            // Send message up to L1 bridge
            // slither-disable-next-line reentrancy-events
            sendCrossDomainMessage(l1TokenBridge, 0, message);
            // slither-disable-next-line reentrancy-events
            emit DepositFailed(_l1Token, _l2Token, _from, _to, _amount, _data);
        }
    }
}