tornado-nova/contracts/bridge/BridgeHelper.sol

/**
 *Submitted for verification at BscScan.com on 2021-03-09
 */

pragma solidity 0.7.6;

/**
 * @dev Wrappers over Solidity's arithmetic operations with added overflow
 * checks.
 *
 * Arithmetic operations in Solidity wrap on overflow. This can easily result
 * in bugs, because programmers usually assume that an overflow raises an
 * error, which is the standard behavior in high level programming languages.
 * `SafeMath` restores this intuition by reverting the transaction when an
 * operation overflows.
 *
 * Using this library instead of the unchecked operations eliminates an entire
 * class of bugs, so it's recommended to use it always.
 */
library SafeMath {
  /**
   * @dev Returns the addition of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `+` operator.
   *
   * Requirements:
   *
   * - Addition cannot overflow.
   */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a, "SafeMath: addition overflow");

    return c;
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   *
   * - Subtraction cannot overflow.
   */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    return sub(a, b, "SafeMath: subtraction overflow");
  }

  /**
   * @dev Returns the subtraction of two unsigned integers, reverting with custom message on
   * overflow (when the result is negative).
   *
   * Counterpart to Solidity's `-` operator.
   *
   * Requirements:
   *
   * - Subtraction cannot overflow.
   */
  function sub(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    require(b <= a, errorMessage);
    uint256 c = a - b;

    return c;
  }

  /**
   * @dev Returns the multiplication of two unsigned integers, reverting on
   * overflow.
   *
   * Counterpart to Solidity's `*` operator.
   *
   * Requirements:
   *
   * - Multiplication cannot overflow.
   */
  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
    // benefit is lost if 'b' is also tested.
    // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b, "SafeMath: multiplication overflow");

    return c;
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   *
   * - The divisor cannot be zero.
   */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    return div(a, b, "SafeMath: division by zero");
  }

  /**
   * @dev Returns the integer division of two unsigned integers. Reverts with custom message on
   * division by zero. The result is rounded towards zero.
   *
   * Counterpart to Solidity's `/` operator. Note: this function uses a
   * `revert` opcode (which leaves remaining gas untouched) while Solidity
   * uses an invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   *
   * - The divisor cannot be zero.
   */
  function div(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    require(b > 0, errorMessage);
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold

    return c;
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * Reverts when dividing by zero.
   *
   * Counterpart to Solidity's `%` operator. This function uses a `revert`
   * opcode (which leaves remaining gas untouched) while Solidity uses an
   * invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   *
   * - The divisor cannot be zero.
   */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    return mod(a, b, "SafeMath: modulo by zero");
  }

  /**
   * @dev Returns the remainder of dividing two unsigned integers. (unsigned integer modulo),
   * Reverts with custom message when dividing by zero.
   *
   * Counterpart to Solidity's `%` operator. This function uses a `revert`
   * opcode (which leaves remaining gas untouched) while Solidity uses an
   * invalid opcode to revert (consuming all remaining gas).
   *
   * Requirements:
   *
   * - The divisor cannot be zero.
   */
  function mod(
    uint256 a,
    uint256 b,
    string memory errorMessage
  ) internal pure returns (uint256) {
    require(b != 0, errorMessage);
    return a % b;
  }
}

interface IOmnibridge {
  function relayTokens(
    address _token,
    address _receiver,
    uint256 _value
  ) external;

  /**
   * @dev Initiate the bridge operation for some amount of tokens from msg.sender.
   * The user should first call Approve method of the ERC677 token.
   * @param token bridged token contract address.
   * @param _receiver address that will receive the native tokens on the other network.
   * @param _value amount of tokens to be transferred to the other network.
   * @param _data additional transfer data to be used on the other side.
   */
  function relayTokensAndCall(
    address token,
    address _receiver,
    uint256 _value,
    bytes memory _data
  ) external;
}

interface IWETH {
  function deposit() external payable;

  function withdraw(uint256 _value) external;

  function approve(address _to, uint256 _value) external;
}

contract Sacrifice {
  constructor(address payable _recipient) payable {
    selfdestruct(_recipient);
  }
}

/**
 * @title AddressHelper
 * @dev Helper methods for Address type.
 */
library AddressHelper {
  /**
   * @dev Try to send native tokens to the address. If it fails, it will force the transfer by creating a selfdestruct contract
   * @param _receiver address that will receive the native tokens
   * @param _value the amount of native tokens to send
   */
  function safeSendValue(address payable _receiver, uint256 _value) internal {
    if (!(_receiver).send(_value)) {
      new Sacrifice{ value: _value }(_receiver);
    }
  }
}

/**
 * @dev Collection of functions related to the address type
 */
library Address {
  /**
   * @dev Returns true if `account` is a contract.
   *
   * [IMPORTANT]
   * ====
   * It is unsafe to assume that an address for which this function returns
   * false is an externally-owned account (EOA) and not a contract.
   *
   * Among others, `isContract` will return false for the following
   * types of addresses:
   *
   *  - an externally-owned account
   *  - a contract in construction
   *  - an address where a contract will be created
   *  - an address where a contract lived, but was destroyed
   * ====
   */
  function isContract(address account) internal view returns (bool) {
    // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
    // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
    // for accounts without code, i.e. `keccak256('')`
    bytes32 codehash;
    bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
    // solhint-disable-next-line no-inline-assembly
    assembly {
      codehash := extcodehash(account)
    }
    return (codehash != accountHash && codehash != 0x0);
  }

  /**
   * @dev Replacement for Solidity's `transfer`: sends `amount` wei to
   * `recipient`, forwarding all available gas and reverting on errors.
   *
   * https://eips.ethereum.org/EIPS/eip-1884[EIP1884] increases the gas cost
   * of certain opcodes, possibly making contracts go over the 2300 gas limit
   * imposed by `transfer`, making them unable to receive funds via
   * `transfer`. {sendValue} removes this limitation.
   *
   * https://diligence.consensys.net/posts/2019/09/stop-using-soliditys-transfer-now/[Learn more].
   *
   * IMPORTANT: because control is transferred to `recipient`, care must be
   * taken to not create reentrancy vulnerabilities. Consider using
   * {ReentrancyGuard} or the
   * https://solidity.readthedocs.io/en/v0.5.11/security-considerations.html#use-the-checks-effects-interactions-pattern[checks-effects-interactions pattern].
   */
  function sendValue(address payable recipient, uint256 amount) internal {
    require(address(this).balance >= amount, "Address: insufficient balance");

    // solhint-disable-next-line avoid-low-level-calls, avoid-call-value
    (bool success, ) = recipient.call{ value: amount }("");
    require(success, "Address: unable to send value, recipient may have reverted");
  }

  /**
   * @dev Performs a Solidity function call using a low level `call`. A
   * plain`call` is an unsafe replacement for a function call: use this
   * function instead.
   *
   * If `target` reverts with a revert reason, it is bubbled up by this
   * function (like regular Solidity function calls).
   *
   * Returns the raw returned data. To convert to the expected return value,
   * use https://solidity.readthedocs.io/en/latest/units-and-global-variables.html?highlight=abi.decode#abi-encoding-and-decoding-functions[`abi.decode`].
   *
   * Requirements:
   *
   * - `target` must be a contract.
   * - calling `target` with `data` must not revert.
   *
   * _Available since v3.1._
   */
  function functionCall(address target, bytes memory data) internal returns (bytes memory) {
    return functionCall(target, data, "Address: low-level call failed");
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
   * `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCall(
    address target,
    bytes memory data,
    string memory errorMessage
  ) internal returns (bytes memory) {
    return _functionCallWithValue(target, data, 0, errorMessage);
  }

  /**
   * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`],
   * but also transferring `value` wei to `target`.
   *
   * Requirements:
   *
   * - the calling contract must have an ETH balance of at least `value`.
   * - the called Solidity function must be `payable`.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(
    address target,
    bytes memory data,
    uint256 value
  ) internal returns (bytes memory) {
    return functionCallWithValue(target, data, value, "Address: low-level call with value failed");
  }

  /**
   * @dev Same as {xref-Address-functionCallWithValue-address-bytes-uint256-}[`functionCallWithValue`], but
   * with `errorMessage` as a fallback revert reason when `target` reverts.
   *
   * _Available since v3.1._
   */
  function functionCallWithValue(
    address target,
    bytes memory data,
    uint256 value,
    string memory errorMessage
  ) internal returns (bytes memory) {
    require(address(this).balance >= value, "Address: insufficient balance for call");
    return _functionCallWithValue(target, data, value, errorMessage);
  }

  function _functionCallWithValue(
    address target,
    bytes memory data,
    uint256 weiValue,
    string memory errorMessage
  ) private returns (bytes memory) {
    require(isContract(target), "Address: call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
    if (success) {
      return returndata;
    } else {
      // Look for revert reason and bubble it up if present
      if (returndata.length > 0) {
        // The easiest way to bubble the revert reason is using memory via assembly

        // solhint-disable-next-line no-inline-assembly
        assembly {
          let returndata_size := mload(returndata)
          revert(add(32, returndata), returndata_size)
        }
      } else {
        revert(errorMessage);
      }
    }
  }
}

/**
 * @dev Interface of the ERC20 standard as defined in the EIP.
 */
interface IERC20 {
  /**
   * @dev Returns the amount of tokens in existence.
   */
  function totalSupply() external view returns (uint256);

  /**
   * @dev Returns the amount of tokens owned by `account`.
   */
  function balanceOf(address account) external view returns (uint256);

  /**
   * @dev Moves `amount` tokens from the caller's account to `recipient`.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transfer(address recipient, uint256 amount) external returns (bool);

  /**
   * @dev Returns the remaining number of tokens that `spender` will be
   * allowed to spend on behalf of `owner` through {transferFrom}. This is
   * zero by default.
   *
   * This value changes when {approve} or {transferFrom} are called.
   */
  function allowance(address owner, address spender) external view returns (uint256);

  /**
   * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * IMPORTANT: Beware that changing an allowance with this method brings the risk
   * that someone may use both the old and the new allowance by unfortunate
   * transaction ordering. One possible solution to mitigate this race
   * condition is to first reduce the spender's allowance to 0 and set the
   * desired value afterwards:
   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
   *
   * Emits an {Approval} event.
   */
  function approve(address spender, uint256 amount) external returns (bool);

  /**
   * @dev Moves `amount` tokens from `sender` to `recipient` using the
   * allowance mechanism. `amount` is then deducted from the caller's
   * allowance.
   *
   * Returns a boolean value indicating whether the operation succeeded.
   *
   * Emits a {Transfer} event.
   */
  function transferFrom(
    address sender,
    address recipient,
    uint256 amount
  ) external returns (bool);

  /**
   * @dev Emitted when `value` tokens are moved from one account (`from`) to
   * another (`to`).
   *
   * Note that `value` may be zero.
   */
  event Transfer(address indexed from, address indexed to, uint256 value);

  /**
   * @dev Emitted when the allowance of a `spender` for an `owner` is set by
   * a call to {approve}. `value` is the new allowance.
   */
  event Approval(address indexed owner, address indexed spender, uint256 value);
}

/**
 * @title SafeERC20
 * @dev Wrappers around ERC20 operations that throw on failure (when the token
 * contract returns false). Tokens that return no value (and instead revert or
 * throw on failure) are also supported, non-reverting calls are assumed to be
 * successful.
 * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
 * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
 */
library SafeERC20 {
  using SafeMath for uint256;
  using Address for address;

  function safeTransfer(
    IERC20 token,
    address to,
    uint256 value
  ) internal {
    _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
  }

  function safeTransferFrom(
    IERC20 token,
    address from,
    address to,
    uint256 value
  ) internal {
    _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
  }

  /**
   * @dev Deprecated. This function has issues similar to the ones found in
   * {IERC20-approve}, and its usage is discouraged.
   *
   * Whenever possible, use {safeIncreaseAllowance} and
   * {safeDecreaseAllowance} instead.
   */
  function safeApprove(
    IERC20 token,
    address spender,
    uint256 value
  ) internal {
    // safeApprove should only be called when setting an initial allowance,
    // or when resetting it to zero. To increase and decrease it, use
    // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
    // solhint-disable-next-line max-line-length
    require(
      (value == 0) || (token.allowance(address(this), spender) == 0),
      "SafeERC20: approve from non-zero to non-zero allowance"
    );
    _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
  }

  function safeIncreaseAllowance(
    IERC20 token,
    address spender,
    uint256 value
  ) internal {
    uint256 newAllowance = token.allowance(address(this), spender).add(value);
    _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
  }

  function safeDecreaseAllowance(
    IERC20 token,
    address spender,
    uint256 value
  ) internal {
    uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
    _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
  }

  /**
   * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
   * on the return value: the return value is optional (but if data is returned, it must not be false).
   * @param token The token targeted by the call.
   * @param data The call data (encoded using abi.encode or one of its variants).
   */
  function _callOptionalReturn(IERC20 token, bytes memory data) private {
    // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
    // we're implementing it ourselves. We use {Address.functionCall} to perform this call, which verifies that
    // the target address contains contract code and also asserts for success in the low-level call.

    bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
    if (returndata.length > 0) {
      // Return data is optional
      // solhint-disable-next-line max-line-length
      require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
    }
  }
}

/**
 * @title OwnableModule
 * @dev Common functionality for multi-token extension non-upgradeable module.
 */
contract OwnableModule {
  address public owner;

  /**
   * @dev Initializes this contract.
   * @param _owner address of the owner that is allowed to perform additional actions on the particular module.
   */
  constructor(address _owner) {
    owner = _owner;
  }

  /**
   * @dev Throws if sender is not the owner of this contract.
   */
  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  /**
   * @dev Changes the owner of this contract.
   * @param _newOwner address of the new owner.
   */
  function transferOwnership(address _newOwner) external onlyOwner {
    owner = _newOwner;
  }
}

/**
 * @title Claimable
 * @dev Implementation of the claiming utils that can be useful for withdrawing accidentally sent tokens that are not used in bridge operations.
 */
contract Claimable {
  using SafeERC20 for IERC20;

  /**
   * Throws if a given address is equal to address(0)
   */
  modifier validAddress(address _to) {
    require(_to != address(0));
    _;
  }

  /**
   * @dev Withdraws the erc20 tokens or native coins from this contract.
   * Caller should additionally check that the claimed token is not a part of bridge operations (i.e. that token != erc20token()).
   * @param _token address of the claimed token or address(0) for native coins.
   * @param _to address of the tokens/coins receiver.
   */
  function claimValues(address _token, address _to) internal validAddress(_to) {
    if (_token == address(0)) {
      claimNativeCoins(_to);
    } else {
      claimErc20Tokens(_token, _to);
    }
  }

  /**
   * @dev Internal function for withdrawing all native coins from the contract.
   * @param _to address of the coins receiver.
   */
  function claimNativeCoins(address _to) internal {
    uint256 value = address(this).balance;
    AddressHelper.safeSendValue(payable(_to), value);
  }

  /**
   * @dev Internal function for withdrawing all tokens of ssome particular ERC20 contract from this contract.
   * @param _token address of the claimed ERC20 token.
   * @param _to address of the tokens receiver.
   */
  function claimErc20Tokens(address _token, address _to) internal {
    IERC20 token = IERC20(_token);
    uint256 balance = token.balanceOf(address(this));
    token.safeTransfer(_to, balance);
  }
}

/**
 * @title WETHOmnibridgeRouter
 * @dev Omnibridge extension for processing native and wrapped native assets.
 * Intended to work with WETH/WBNB/WXDAI tokens, see:
 *   https://etherscan.io/address/0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2
 *   https://bscscan.com/address/0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c
 *   https://blockscout.com/poa/xdai/address/0xe91D153E0b41518A2Ce8Dd3D7944Fa863463a97d
 */
contract WETHOmnibridgeRouter is OwnableModule, Claimable {
  IOmnibridge public immutable bridge;
  IWETH public immutable WETH;

  /**
   * @dev Initializes this contract.
   * @param _bridge address of the HomeOmnibridge/ForeignOmnibridge contract.
   * @param _weth address of the WETH token used for wrapping/unwrapping native coins (e.g. WETH/WBNB/WXDAI).
   * @param _owner address of the contract owner.
   */
  constructor(
    IOmnibridge _bridge,
    IWETH _weth,
    address _owner
  ) OwnableModule(_owner) {
    bridge = _bridge;
    WETH = _weth;
    _weth.approve(address(_bridge), uint256(-1));
  }

  /**
   * @dev Wraps native assets and relays wrapped ERC20 tokens to the other chain.
   * Call msg.sender will receive assets on the other side of the bridge.
   */
  function wrapAndRelayTokens() external payable {
    wrapAndRelayTokens(msg.sender);
  }

  /**
   * @dev Wraps native assets and relays wrapped ERC20 tokens to the other chain.
   * @param _receiver bridged assets receiver on the other side of the bridge.
   */
  function wrapAndRelayTokens(address _receiver) public payable {
    WETH.deposit{ value: msg.value }();
    bridge.relayTokens(address(WETH), _receiver, msg.value);
  }

  /**
   * @dev Wraps native assets and relays wrapped ERC20 tokens to the other chain.
   * It also calls receiver on other side with the _data provided.
   * @param _receiver bridged assets receiver on the other side of the bridge.
   * @param _data data for the call of receiver on other side.
   */
  function wrapAndRelayTokens(address _receiver, bytes memory _data) public payable {
    WETH.deposit{ value: msg.value }();
    bridge.relayTokensAndCall(address(WETH), _receiver, msg.value, _data);
  }

  /**
   * @dev Bridged callback function used for unwrapping received tokens.
   * Can only be called by the associated Omnibridge contract.
   * @param _token bridged token contract address, should be WETH.
   * @param _value amount of bridged/received tokens.
   * @param _data extra data passed alongside with relayTokensAndCall on the other side of the bridge.
   * Should contain coins receiver address.
   */
  function onTokenBridged(
    address _token,
    uint256 _value,
    bytes calldata _data
  ) external {
    require(_token == address(WETH));
    require(msg.sender == address(bridge));
    require(_data.length == 20);

    WETH.withdraw(_value);

    address payable receiver;
    assembly {
      receiver := calldataload(120)
    }
    AddressHelper.safeSendValue(receiver, _value);
  }

  /**
   * @dev Claims stuck coins/tokens.
   * Only contract owner can call this method.
   * @param _token address of claimed token contract, address(0) for native coins.
   * @param _to address of tokens receiver
   */
  function claimTokens(address _token, address _to) external onlyOwner {
    claimValues(_token, _to);
  }

  /**
   * @dev Ether receive function.
   * Should be only called from the WETH contract when withdrawing native coins. Will revert otherwise.
   */
  receive() external payable {
    require(msg.sender == address(WETH));
  }
}