pragma solidity ^0.6.2;
pragma experimental ABIEncoderV2;


contract ReentrancyGuard {
  bool private _notEntered;

  constructor() internal {
    // Storing an initial non-zero value makes deployment a bit more
    // expensive, but in exchange the refund on every call to nonReentrant
    // will be lower in amount. Since refunds are capped to a percetange of
    // the total transaction's gas, it is best to keep them low in cases
    // like this one, to increase the likelihood of the full refund coming
    // into effect.
    _notEntered = true;
  }

  /**
   * @dev Prevents a contract from calling itself, directly or indirectly.
   * Calling a `nonReentrant` function from another `nonReentrant`
   * function is not supported. It is possible to prevent this from happening
   * by making the `nonReentrant` function external, and make it call a
   * `private` function that does the actual work.
   */
  modifier nonReentrant() {
    // On the first call to nonReentrant, _notEntered will be true
    require(_notEntered, "ReentrancyGuard: reentrant call");

    // Any calls to nonReentrant after this point will fail
    _notEntered = false;

    _;

    // By storing the original value once again, a refund is triggered (see
    // https://eips.ethereum.org/EIPS/eip-2200)
    _notEntered = true;
  }
}


contract Context {
  // Empty internal constructor, to prevent people from mistakenly deploying
  // an instance of this contract, which should be used via inheritance.
  constructor() internal {}

  function _msgSender() internal virtual view returns (address payable) {
    return msg.sender;
  }

  function _msgData() internal virtual view returns (bytes memory) {
    this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
    return msg.data;
  }
}


contract Pausable is Context {
  /**
   * @dev Emitted when the pause is triggered by `account`.
   */
  event Paused(address account);

  /**
   * @dev Emitted when the pause is lifted by `account`.
   */
  event Unpaused(address account);

  bool private _paused;

  /**
   * @dev Initializes the contract in unpaused state.
   */
  constructor() internal {
    _paused = false;
  }

  /**
   * @dev Returns true if the contract is paused, and false otherwise.
   */
  function paused() public view returns (bool) {
    return _paused;
  }

  /**
   * @dev Modifier to make a function callable only when the contract is not paused.
   */
  modifier whenNotPaused() {
    require(!_paused, "Pausable: paused");
    _;
  }

  /**
   * @dev Modifier to make a function callable only when the contract is paused.
   */
  modifier whenPaused() {
    require(_paused, "Pausable: not paused");
    _;
  }

  /**
   * @dev Triggers stopped state.
   */
  function _pause() internal virtual whenNotPaused {
    _paused = true;
    emit Paused(_msgSender());
  }

  /**
   * @dev Returns to normal state.
   */
  function _unpause() internal virtual whenPaused {
    _paused = false;
    emit Unpaused(_msgSender());
  }
}


contract Ownable is Context {
  address private _owner;

  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  /**
   * @dev Initializes the contract setting the deployer as the initial owner.
   */
  constructor() internal {
    address msgSender = _msgSender();
    _owner = msgSender;
    emit OwnershipTransferred(address(0), msgSender);
  }

  /**
   * @dev Returns the address of the current owner.
   */
  function owner() public view returns (address) {
    return _owner;
  }

  /**
   * @dev Throws if called by any account other than the owner.
   */
  modifier onlyOwner() {
    require(_owner == _msgSender(), "Ownable: caller is not the owner");
    _;
  }

  /**
   * @dev Leaves the contract without owner. It will not be possible to call
   * `onlyOwner` functions anymore. Can only be called by the current owner.
   *
   * NOTE: Renouncing ownership will leave the contract without an owner,
   * thereby removing any functionality that is only available to the owner.
   */
  function renounceOwnership() public virtual onlyOwner {
    emit OwnershipTransferred(_owner, address(0));
    _owner = address(0);
  }

  /**
   * @dev Transfers ownership of the contract to a new account (`newOwner`).
   * Can only be called by the current owner.
   */
  function transferOwnership(address newOwner) public virtual onlyOwner {
    require(newOwner != address(0), "Ownable: new owner is the zero address");
    emit OwnershipTransferred(_owner, newOwner);
    _owner = newOwner;
  }
}


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);
}


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");
  }
}


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) {
    // Solidity only automatically asserts when dividing by 0
    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;
  }
}


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)
    );
  }

  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.

    // A Solidity high level call has three parts:
    //  1. The target address is checked to verify it contains contract code
    //  2. The call itself is made, and success asserted
    //  3. The return value is decoded, which in turn checks the size of the returned data.
    // solhint-disable-next-line max-line-length
    require(address(token).isContract(), "SafeERC20: call to non-contract");

    // solhint-disable-next-line avoid-low-level-calls
    (bool success, bytes memory returndata) = address(token).call(data);
    require(success, "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");
    }
  }
}


contract BulkCheckout is Ownable, Pausable, ReentrancyGuard {
  using Address for address payable;
  using SafeMath for uint256;
  /**
   * @notice Placeholder token address for ETH donations. This address is used in various other
   * projects as a stand-in for ETH
   */
  address constant ETH_TOKEN_PLACHOLDER = 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE;

  /**
   * @notice Required parameters for each donation
   */
  struct Donation {
    address token; // address of the token to donate
    uint256 amount; // amount of tokens to donate
    address payable dest; // grant address
  }

  /**
   * @dev Emitted on each donation
   */
  event DonationSent(
    address indexed token,
    uint256 indexed amount,
    address dest,
    address indexed donor
  );

  /**
   * @dev Emitted when a token or ETH is withdrawn from the contract
   */
  event TokenWithdrawn(address indexed token, uint256 indexed amount, address indexed dest);

  /**
   * @notice Bulk gitcoin grant donations
   * @dev We assume all token approvals were already executed
   * @param _donations Array of donation structs
   */
  function donate(Donation[] calldata _donations) external payable nonReentrant whenNotPaused {
    // We track total ETH donations to ensure msg.value is exactly correct
    uint256 _ethDonationTotal = 0;

    for (uint256 i = 0; i < _donations.length; i++) {
      emit DonationSent(_donations[i].token, _donations[i].amount, _donations[i].dest, msg.sender);
      if (_donations[i].token != ETH_TOKEN_PLACHOLDER) {
        // Token donation
        // This method throws on failure, so there is no return value to check
        SafeERC20.safeTransferFrom(
          IERC20(_donations[i].token),
          msg.sender,
          _donations[i].dest,
          _donations[i].amount
        );
      } else {
        // ETH donation
        // See comments in Address.sol for why we use sendValue over transer
        _donations[i].dest.sendValue(_donations[i].amount);
        _ethDonationTotal = _ethDonationTotal.add(_donations[i].amount);
      }
    }

    // Revert if the wrong amount of ETH was sent
    require(msg.value == _ethDonationTotal, "BulkCheckout: Too much ETH sent");
  }

  /**
   * @notice Transfers all tokens of the input adress to the recipient. This is
   * useful tokens are accidentally sent to this contrasct
   * @param _tokenAddress address of token to send
   * @param _dest destination address to send tokens to
   */
  function withdrawToken(address _tokenAddress, address _dest) external onlyOwner {
    uint256 _balance = IERC20(_tokenAddress).balanceOf(address(this));
    emit TokenWithdrawn(_tokenAddress, _balance, _dest);
    SafeERC20.safeTransfer(IERC20(_tokenAddress), _dest, _balance);
  }

  /**
   * @notice Transfers all Ether to the specified address
   * @param _dest destination address to send ETH to
   */
  function withdrawEther(address payable _dest) external onlyOwner {
    uint256 _balance = address(this).balance;
    emit TokenWithdrawn(ETH_TOKEN_PLACHOLDER, _balance, _dest);
    _dest.sendValue(_balance);
  }

  /**
   * @notice Pause contract
   */
  function pause() external onlyOwner whenNotPaused {
    _pause();
  }

  /**
   * @notice Unpause contract
   */
  function unpause() external onlyOwner whenPaused {
    _unpause();
  }
}

pragma solidity ^0.5.3;

/// @title Proxy - Generic proxy contract allows to execute all transactions applying the code of a master contract.
/// @author Stefan George - <[email protected]>
/// @author Richard Meissner - <[email protected]>
contract Proxy {

    // masterCopy always needs to be first declared variable, to ensure that it is at the same location in the contracts to which calls are delegated.
    // To reduce deployment costs this variable is internal and needs to be retrieved via `getStorageAt`
    address internal masterCopy;

    /// @dev Constructor function sets address of master copy contract.
    /// @param _masterCopy Master copy address.
    constructor(address _masterCopy)
        public
    {
        require(_masterCopy != address(0), "Invalid master copy address provided");
        masterCopy = _masterCopy;
    }

    /// @dev Fallback function forwards all transactions and returns all received return data.
    function ()
        external
        payable
    {
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            let masterCopy := and(sload(0), 0xffffffffffffffffffffffffffffffffffffffff)
            // 0xa619486e == keccak("masterCopy()"). The value is right padded to 32-bytes with 0s
            if eq(calldataload(0), 0xa619486e00000000000000000000000000000000000000000000000000000000) {
                mstore(0, masterCopy)
                return(0, 0x20)
            }
            calldatacopy(0, 0, calldatasize())
            let success := delegatecall(gas, masterCopy, 0, calldatasize(), 0, 0)
            returndatacopy(0, 0, returndatasize())
            if eq(success, 0) { revert(0, returndatasize()) }
            return(0, returndatasize())
        }
    }
}

pragma solidity >=0.5.0 <0.7.0;

/// @title SelfAuthorized - authorizes current contract to perform actions
/// @author Richard Meissner - <[email protected]>
contract SelfAuthorized {
    modifier authorized() {
        require(msg.sender == address(this), "Method can only be called from this contract");
        _;
    }
}



/// @title MasterCopy - Base for master copy contracts (should always be first super contract)
///         This contract is tightly coupled to our proxy contract (see `proxies/Proxy.sol`)
/// @author Richard Meissner - <[email protected]>
contract MasterCopy is SelfAuthorized {

    event ChangedMasterCopy(address masterCopy);

    // masterCopy always needs to be first declared variable, to ensure that it is at the same location as in the Proxy contract.
    // It should also always be ensured that the address is stored alone (uses a full word)
    address private masterCopy;

    /// @dev Allows to upgrade the contract. This can only be done via a Safe transaction.
    /// @param _masterCopy New contract address.
    function changeMasterCopy(address _masterCopy)
        public
        authorized
    {
        // Master copy address cannot be null.
        require(_masterCopy != address(0), "Invalid master copy address provided");
        masterCopy = _masterCopy;
        emit ChangedMasterCopy(_masterCopy);
    }
}


/// @title Module - Base class for modules.
/// @author Stefan George - <[email protected]>
/// @author Richard Meissner - <[email protected]>
contract Module is MasterCopy {

    ModuleManager public manager;

    modifier authorized() {
        require(msg.sender == address(manager), "Method can only be called from manager");
        _;
    }

    function setManager()
        internal
    {
        // manager can only be 0 at initalization of contract.
        // Check ensures that setup function can only be called once.
        require(address(manager) == address(0), "Manager has already been set");
        manager = ModuleManager(msg.sender);
    }
}





/// @title Enum - Collection of enums
/// @author Richard Meissner - <[email protected]>
contract Enum {
    enum Operation {
        Call,
        DelegateCall
    }
}





/// @title Executor - A contract that can execute transactions
/// @author Richard Meissner - <[email protected]>
contract Executor {

    function execute(address to, uint256 value, bytes memory data, Enum.Operation operation, uint256 txGas)
        internal
        returns (bool success)
    {
        if (operation == Enum.Operation.Call)
            success = executeCall(to, value, data, txGas);
        else if (operation == Enum.Operation.DelegateCall)
            success = executeDelegateCall(to, data, txGas);
        else
            success = false;
    }

    function executeCall(address to, uint256 value, bytes memory data, uint256 txGas)
        internal
        returns (bool success)
    {
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            success := call(txGas, to, value, add(data, 0x20), mload(data), 0, 0)
        }
    }

    function executeDelegateCall(address to, bytes memory data, uint256 txGas)
        internal
        returns (bool success)
    {
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            success := delegatecall(txGas, to, add(data, 0x20), mload(data), 0, 0)
        }
    }
}



/// @title SecuredTokenTransfer - Secure token transfer
/// @author Richard Meissner - <[email protected]>
contract SecuredTokenTransfer {

    /// @dev Transfers a token and returns if it was a success
    /// @param token Token that should be transferred
    /// @param receiver Receiver to whom the token should be transferred
    /// @param amount The amount of tokens that should be transferred
    function transferToken (
        address token,
        address receiver,
        uint256 amount
    )
        internal
        returns (bool transferred)
    {
        bytes memory data = abi.encodeWithSignature("transfer(address,uint256)", receiver, amount);
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            let success := call(sub(gas, 10000), token, 0, add(data, 0x20), mload(data), 0, 0)
            let ptr := mload(0x40)
            mstore(0x40, add(ptr, returndatasize()))
            returndatacopy(ptr, 0, returndatasize())
            switch returndatasize()
            case 0 { transferred := success }
            case 0x20 { transferred := iszero(or(iszero(success), iszero(mload(ptr)))) }
            default { transferred := 0 }
        }
    }
}










/// @title Module Manager - A contract that manages modules that can execute transactions via this contract
/// @author Stefan George - <[email protected]>
/// @author Richard Meissner - <[email protected]>
contract ModuleManager is SelfAuthorized, Executor {

    event EnabledModule(Module module);
    event DisabledModule(Module module);
    event ExecutionFromModuleSuccess(address indexed module);
    event ExecutionFromModuleFailure(address indexed module);

    address internal constant SENTINEL_MODULES = address(0x1);

    mapping (address => address) internal modules;

    function setupModules(address to, bytes memory data)
        internal
    {
        require(modules[SENTINEL_MODULES] == address(0), "Modules have already been initialized");
        modules[SENTINEL_MODULES] = SENTINEL_MODULES;
        if (to != address(0))
            // Setup has to complete successfully or transaction fails.
            require(executeDelegateCall(to, data, gasleft()), "Could not finish initialization");
    }

    /// @dev Allows to add a module to the whitelist.
    ///      This can only be done via a Safe transaction.
    /// @param module Module to be whitelisted.
    function enableModule(Module module)
        public
        authorized
    {
        // Module address cannot be null or sentinel.
        require(address(module) != address(0) && address(module) != SENTINEL_MODULES, "Invalid module address provided");
        // Module cannot be added twice.
        require(modules[address(module)] == address(0), "Module has already been added");
        modules[address(module)] = modules[SENTINEL_MODULES];
        modules[SENTINEL_MODULES] = address(module);
        emit EnabledModule(module);
    }

    /// @dev Allows to remove a module from the whitelist.
    ///      This can only be done via a Safe transaction.
    /// @param prevModule Module that pointed to the module to be removed in the linked list
    /// @param module Module to be removed.
    function disableModule(Module prevModule, Module module)
        public
        authorized
    {
        // Validate module address and check that it corresponds to module index.
        require(address(module) != address(0) && address(module) != SENTINEL_MODULES, "Invalid module address provided");
        require(modules[address(prevModule)] == address(module), "Invalid prevModule, module pair provided");
        modules[address(prevModule)] = modules[address(module)];
        modules[address(module)] = address(0);
        emit DisabledModule(module);
    }

    /// @dev Allows a Module to execute a Safe transaction without any further confirmations.
    /// @param to Destination address of module transaction.
    /// @param value Ether value of module transaction.
    /// @param data Data payload of module transaction.
    /// @param operation Operation type of module transaction.
    function execTransactionFromModule(address to, uint256 value, bytes memory data, Enum.Operation operation)
        public
        returns (bool success)
    {
        // Only whitelisted modules are allowed.
        require(msg.sender != SENTINEL_MODULES && modules[msg.sender] != address(0), "Method can only be called from an enabled module");
        // Execute transaction without further confirmations.
        success = execute(to, value, data, operation, gasleft());
        if (success) emit ExecutionFromModuleSuccess(msg.sender);
        else emit ExecutionFromModuleFailure(msg.sender);
    }

    /// @dev Allows a Module to execute a Safe transaction without any further confirmations and return data
    /// @param to Destination address of module transaction.
    /// @param value Ether value of module transaction.
    /// @param data Data payload of module transaction.
    /// @param operation Operation type of module transaction.
    function execTransactionFromModuleReturnData(address to, uint256 value, bytes memory data, Enum.Operation operation)
        public
        returns (bool success, bytes memory returnData)
    {
        success = execTransactionFromModule(to, value, data, operation);
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            // Load free memory location
            let ptr := mload(0x40)
            // We allocate memory for the return data by setting the free memory location to
            // current free memory location + data size + 32 bytes for data size value
            mstore(0x40, add(ptr, add(returndatasize(), 0x20)))
            // Store the size
            mstore(ptr, returndatasize())
            // Store the data
            returndatacopy(add(ptr, 0x20), 0, returndatasize())
            // Point the return data to the correct memory location
            returnData := ptr
        }
    }

    /// @dev Returns array of first 10 modules.
    /// @return Array of modules.
    function getModules()
        public
        view
        returns (address[] memory)
    {
        (address[] memory array,) = getModulesPaginated(SENTINEL_MODULES, 10);
        return array;
    }

    /// @dev Returns array of modules.
    /// @param start Start of the page.
    /// @param pageSize Maximum number of modules that should be returned.
    /// @return Array of modules.
    function getModulesPaginated(address start, uint256 pageSize)
        public
        view
        returns (address[] memory array, address next)
    {
        // Init array with max page size
        array = new address[](pageSize);

        // Populate return array
        uint256 moduleCount = 0;
        address currentModule = modules[start];
        while(currentModule != address(0x0) && currentModule != SENTINEL_MODULES && moduleCount < pageSize) {
            array[moduleCount] = currentModule;
            currentModule = modules[currentModule];
            moduleCount++;
        }
        next = currentModule;
        // Set correct size of returned array
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            mstore(array, moduleCount)
        }
    }
}




/// @title OwnerManager - Manages a set of owners and a threshold to perform actions.
/// @author Stefan George - <[email protected]>
/// @author Richard Meissner - <[email protected]>
contract OwnerManager is SelfAuthorized {

    event AddedOwner(address owner);
    event RemovedOwner(address owner);
    event ChangedThreshold(uint256 threshold);

    address internal constant SENTINEL_OWNERS = address(0x1);

    mapping(address => address) internal owners;
    uint256 ownerCount;
    uint256 internal threshold;

    /// @dev Setup function sets initial storage of contract.
    /// @param _owners List of Safe owners.
    /// @param _threshold Number of required confirmations for a Safe transaction.
    function setupOwners(address[] memory _owners, uint256 _threshold)
        internal
    {
        // Threshold can only be 0 at initialization.
        // Check ensures that setup function can only be called once.
        require(threshold == 0, "Owners have already been setup");
        // Validate that threshold is smaller than number of added owners.
        require(_threshold <= _owners.length, "Threshold cannot exceed owner count");
        // There has to be at least one Safe owner.
        require(_threshold >= 1, "Threshold needs to be greater than 0");
        // Initializing Safe owners.
        address currentOwner = SENTINEL_OWNERS;
        for (uint256 i = 0; i < _owners.length; i++) {
            // Owner address cannot be null.
            address owner = _owners[i];
            require(owner != address(0) && owner != SENTINEL_OWNERS, "Invalid owner address provided");
            // No duplicate owners allowed.
            require(owners[owner] == address(0), "Duplicate owner address provided");
            owners[currentOwner] = owner;
            currentOwner = owner;
        }
        owners[currentOwner] = SENTINEL_OWNERS;
        ownerCount = _owners.length;
        threshold = _threshold;
    }

    /// @dev Allows to add a new owner to the Safe and update the threshold at the same time.
    ///      This can only be done via a Safe transaction.
    /// @param owner New owner address.
    /// @param _threshold New threshold.
    function addOwnerWithThreshold(address owner, uint256 _threshold)
        public
        authorized
    {
        // Owner address cannot be null.
        require(owner != address(0) && owner != SENTINEL_OWNERS, "Invalid owner address provided");
        // No duplicate owners allowed.
        require(owners[owner] == address(0), "Address is already an owner");
        owners[owner] = owners[SENTINEL_OWNERS];
        owners[SENTINEL_OWNERS] = owner;
        ownerCount++;
        emit AddedOwner(owner);
        // Change threshold if threshold was changed.
        if (threshold != _threshold)
            changeThreshold(_threshold);
    }

    /// @dev Allows to remove an owner from the Safe and update the threshold at the same time.
    ///      This can only be done via a Safe transaction.
    /// @param prevOwner Owner that pointed to the owner to be removed in the linked list
    /// @param owner Owner address to be removed.
    /// @param _threshold New threshold.
    function removeOwner(address prevOwner, address owner, uint256 _threshold)
        public
        authorized
    {
        // Only allow to remove an owner, if threshold can still be reached.
        require(ownerCount - 1 >= _threshold, "New owner count needs to be larger than new threshold");
        // Validate owner address and check that it corresponds to owner index.
        require(owner != address(0) && owner != SENTINEL_OWNERS, "Invalid owner address provided");
        require(owners[prevOwner] == owner, "Invalid prevOwner, owner pair provided");
        owners[prevOwner] = owners[owner];
        owners[owner] = address(0);
        ownerCount--;
        emit RemovedOwner(owner);
        // Change threshold if threshold was changed.
        if (threshold != _threshold)
            changeThreshold(_threshold);
    }

    /// @dev Allows to swap/replace an owner from the Safe with another address.
    ///      This can only be done via a Safe transaction.
    /// @param prevOwner Owner that pointed to the owner to be replaced in the linked list
    /// @param oldOwner Owner address to be replaced.
    /// @param newOwner New owner address.
    function swapOwner(address prevOwner, address oldOwner, address newOwner)
        public
        authorized
    {
        // Owner address cannot be null.
        require(newOwner != address(0) && newOwner != SENTINEL_OWNERS, "Invalid owner address provided");
        // No duplicate owners allowed.
        require(owners[newOwner] == address(0), "Address is already an owner");
        // Validate oldOwner address and check that it corresponds to owner index.
        require(oldOwner != address(0) && oldOwner != SENTINEL_OWNERS, "Invalid owner address provided");
        require(owners[prevOwner] == oldOwner, "Invalid prevOwner, owner pair provided");
        owners[newOwner] = owners[oldOwner];
        owners[prevOwner] = newOwner;
        owners[oldOwner] = address(0);
        emit RemovedOwner(oldOwner);
        emit AddedOwner(newOwner);
    }

    /// @dev Allows to update the number of required confirmations by Safe owners.
    ///      This can only be done via a Safe transaction.
    /// @param _threshold New threshold.
    function changeThreshold(uint256 _threshold)
        public
        authorized
    {
        // Validate that threshold is smaller than number of owners.
        require(_threshold <= ownerCount, "Threshold cannot exceed owner count");
        // There has to be at least one Safe owner.
        require(_threshold >= 1, "Threshold needs to be greater than 0");
        threshold = _threshold;
        emit ChangedThreshold(threshold);
    }

    function getThreshold()
        public
        view
        returns (uint256)
    {
        return threshold;
    }

    function isOwner(address owner)
        public
        view
        returns (bool)
    {
        return owner != SENTINEL_OWNERS && owners[owner] != address(0);
    }

    /// @dev Returns array of owners.
    /// @return Array of Safe owners.
    function getOwners()
        public
        view
        returns (address[] memory)
    {
        address[] memory array = new address[](ownerCount);

        // populate return array
        uint256 index = 0;
        address currentOwner = owners[SENTINEL_OWNERS];
        while(currentOwner != SENTINEL_OWNERS) {
            array[index] = currentOwner;
            currentOwner = owners[currentOwner];
            index ++;
        }
        return array;
    }
}





/// @title Fallback Manager - A contract that manages fallback calls made to this contract
/// @author Richard Meissner - <[email protected]>
contract FallbackManager is SelfAuthorized {

    // keccak256("fallback_manager.handler.address")
    bytes32 internal constant FALLBACK_HANDLER_STORAGE_SLOT = 0x6c9a6c4a39284e37ed1cf53d337577d14212a4870fb976a4366c693b939918d5;

    function internalSetFallbackHandler(address handler) internal {
        bytes32 slot = FALLBACK_HANDLER_STORAGE_SLOT;
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            sstore(slot, handler)
        }
    }

    /// @dev Allows to add a contract to handle fallback calls.
    ///      Only fallback calls without value and with data will be forwarded.
    ///      This can only be done via a Safe transaction.
    /// @param handler contract to handle fallbacks calls.
    function setFallbackHandler(address handler)
        public
        authorized
    {
        internalSetFallbackHandler(handler);
    }

    function ()
        external
        payable
    {
        // Only calls without value and with data will be forwarded
        if (msg.value > 0 || msg.data.length == 0) {
            return;
        }
        bytes32 slot = FALLBACK_HANDLER_STORAGE_SLOT;
        address handler;
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            handler := sload(slot)
        }

        if (handler != address(0)) {
            // solium-disable-next-line security/no-inline-assembly
            assembly {
                calldatacopy(0, 0, calldatasize())
                let success := call(gas, handler, 0, 0, calldatasize(), 0, 0)
                returndatacopy(0, 0, returndatasize())
                if eq(success, 0) { revert(0, returndatasize()) }
                return(0, returndatasize())
            }
        }
    }
}







/// @title SignatureDecoder - Decodes signatures that a encoded as bytes
/// @author Ricardo Guilherme Schmidt (Status Research & Development GmbH)
/// @author Richard Meissner - <[email protected]>
contract SignatureDecoder {
    
    /// @dev Recovers address who signed the message
    /// @param messageHash operation ethereum signed message hash
    /// @param messageSignature message `txHash` signature
    /// @param pos which signature to read
    function recoverKey (
        bytes32 messageHash,
        bytes memory messageSignature,
        uint256 pos
    )
        internal
        pure
        returns (address)
    {
        uint8 v;
        bytes32 r;
        bytes32 s;
        (v, r, s) = signatureSplit(messageSignature, pos);
        return ecrecover(messageHash, v, r, s);
    }

    /// @dev divides bytes signature into `uint8 v, bytes32 r, bytes32 s`.
    /// @notice Make sure to peform a bounds check for @param pos, to avoid out of bounds access on @param signatures
    /// @param pos which signature to read. A prior bounds check of this parameter should be performed, to avoid out of bounds access
    /// @param signatures concatenated rsv signatures
    function signatureSplit(bytes memory signatures, uint256 pos)
        internal
        pure
        returns (uint8 v, bytes32 r, bytes32 s)
    {
        // The signature format is a compact form of:
        //   {bytes32 r}{bytes32 s}{uint8 v}
        // Compact means, uint8 is not padded to 32 bytes.
        // solium-disable-next-line security/no-inline-assembly
        assembly {
            let signaturePos := mul(0x41, pos)
            r := mload(add(signatures, add(signaturePos, 0x20)))
            s := mload(add(signatures, add(signaturePos, 0x40)))
            // Here we are loading the last 32 bytes, including 31 bytes
            // of 's'. There is no 'mload8' to do this.
            //
            // 'byte' is not working due to the Solidity parser, so lets
            // use the second best option, 'and'
            v := and(mload(add(signatures, add(signaturePos, 0x41))), 0xff)
        }
    }
}




contract ISignatureValidatorConstants {
    // bytes4(keccak256("isValidSignature(bytes,bytes)")
    bytes4 constant internal EIP1271_MAGIC_VALUE = 0x20c13b0b;
}

contract ISignatureValidator is ISignatureValidatorConstants {

    /**
    * @dev Should return whether the signature provided is valid for the provided data
    * @param _data Arbitrary length data signed on the behalf of address(this)
    * @param _signature Signature byte array associated with _data
    *
    * MUST return the bytes4 magic value 0x20c13b0b when function passes.
    * MUST NOT modify state (using STATICCALL for solc < 0.5, view modifier for solc > 0.5)
    * MUST allow external calls
    */
    function isValidSignature(
        bytes memory _data,
        bytes memory _signature)
        public
        view
        returns (bytes4);
}


/**
 * @title SafeMath
 * @dev Math operations with safety checks that revert on error
 * TODO: remove once open zeppelin update to solc 0.5.0
 */
library SafeMath {

  /**
  * @dev Multiplies two numbers, reverts on 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-solidity/pull/522
    if (a == 0) {
      return 0;
    }

    uint256 c = a * b;
    require(c / a == b);

    return c;
  }

  /**
  * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
  */
  function div(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b > 0); // Solidity only automatically asserts when dividing by 0
    uint256 c = a / b;
    // assert(a == b * c + a % b); // There is no case in which this doesn't hold

    return c;
  }

  /**
  * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
  */
  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b <= a);
    uint256 c = a - b;

    return c;
  }

  /**
  * @dev Adds two numbers, reverts on overflow.
  */
  function add(uint256 a, uint256 b) internal pure returns (uint256) {
    uint256 c = a + b;
    require(c >= a);

    return c;
  }

  /**
  * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
  * reverts when dividing by zero.
  */
  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
    require(b != 0);
    return a % b;
  }
}

/// @title Gnosis Safe - A multisignature wallet with support for confirmations using signed messages based on ERC191.
/// @author Stefan George - <[email protected]>
/// @author Richard Meissner - <[email protected]>
/// @author Ricardo Guilherme Schmidt - (Status Research & Development GmbH) - Gas Token Payment
contract GnosisSafe
    is MasterCopy, ModuleManager, OwnerManager, SignatureDecoder, SecuredTokenTransfer, ISignatureValidatorConstants, FallbackManager {

    using SafeMath for uint256;

    string public constant NAME = "Gnosis Safe";
    string public constant VERSION = "1.1.1";

    //keccak256(
    //    "EIP712Domain(address verifyingContract)"
    //);
    bytes32 private constant DOMAIN_SEPARATOR_TYPEHASH = 0x035aff83d86937d35b32e04f0ddc6ff469290eef2f1b692d8a815c89404d4749;

    //keccak256(
    //    "SafeTx(address to,uint256 value,bytes data,uint8 operation,uint256 safeTxGas,uint256 baseGas,uint256 gasPrice,address gasToken,address refundReceiver,uint256 nonce)"
    //);
    bytes32 private constant SAFE_TX_TYPEHASH = 0xbb8310d486368db6bd6f849402fdd73ad53d316b5a4b2644ad6efe0f941286d8;

    //keccak256(
    //    "SafeMessage(bytes message)"
    //);
    bytes32 private constant SAFE_MSG_TYPEHASH = 0x60b3cbf8b4a223d68d641b3b6ddf9a298e7f33710cf3d3a9d1146b5a6150fbca;

    event ApproveHash(
        bytes32 indexed approvedHash,
        address indexed owner
    );
    event SignMsg(
        bytes32 indexed msgHash
    );
    event ExecutionFailure(
        bytes32 txHash, uint256 payment
    );
    event ExecutionSuccess(
        bytes32 txHash, uint256 payment
    );

    uint256 public nonce;
    bytes32 public domainSeparator;
    // Mapping to keep track of all message hashes that have been approve by ALL REQUIRED owners
    mapping(bytes32 => uint256) public signedMessages;
    // Mapping to keep track of all hashes (message or transaction) that have been approve by ANY owners
    mapping(address => mapping(bytes32 => uint256)) public approvedHashes;

    // This constructor ensures that this contract can only be used as a master copy for Proxy contracts
    constructor() public {
        // By setting the threshold it is not possible to call setup anymore,
        // so we create a Safe with 0 owners and threshold 1.
        // This is an unusable Safe, perfect for the mastercopy
        threshold = 1;
    }

    /// @dev Setup function sets initial storage of contract.
    /// @param _owners List of Safe owners.
    /// @param _threshold Number of required confirmations for a Safe transaction.
    /// @param to Contract address for optional delegate call.
    /// @param data Data payload for optional delegate call.
    /// @param fallbackHandler Handler for fallback calls to this contract
    /// @param paymentToken Token that should be used for the payment (0 is ETH)
    /// @param payment Value that should be paid
    /// @param paymentReceiver Adddress that should receive the payment (or 0 if tx.origin)
    function setup(
        address[] calldata _owners,
        uint256 _threshold,
        address to,
        bytes calldata data,
        address fallbackHandler,
        address paymentToken,
        uint256 payment,
        address payable paymentReceiver
    )
        external
    {
        require(domainSeparator == 0, "Domain Separator already set!");
        domainSeparator = keccak256(abi.encode(DOMAIN_SEPARATOR_TYPEHASH, this));
        setupOwners(_owners, _threshold);
        if (fallbackHandler != address(0)) internalSetFallbackHandler(fallbackHandler);
        // As setupOwners can only be called if the contract has not been initialized we don't need a check for setupModules
        setupModules(to, data);

        if (payment > 0) {
            // To avoid running into issues with EIP-170 we reuse the handlePayment function (to avoid adjusting code of that has been verified we do not adjust the method itself)
            // baseGas = 0, gasPrice = 1 and gas = payment => amount = (payment + 0) * 1 = payment
            handlePayment(payment, 0, 1, paymentToken, paymentReceiver);
        }
    }

    /// @dev Allows to execute a Safe transaction confirmed by required number of owners and then pays the account that submitted the transaction.
    ///      Note: The fees are always transfered, even if the user transaction fails.
    /// @param to Destination address of Safe transaction.
    /// @param value Ether value of Safe transaction.
    /// @param data Data payload of Safe transaction.
    /// @param operation Operation type of Safe transaction.
    /// @param safeTxGas Gas that should be used for the Safe transaction.
    /// @param baseGas Gas costs for that are indipendent of the transaction execution(e.g. base transaction fee, signature check, payment of the refund)
    /// @param gasPrice Gas price that should be used for the payment calculation.
    /// @param gasToken Token address (or 0 if ETH) that is used for the payment.
    /// @param refundReceiver Address of receiver of gas payment (or 0 if tx.origin).
    /// @param signatures Packed signature data ({bytes32 r}{bytes32 s}{uint8 v})
    function execTransaction(
        address to,
        uint256 value,
        bytes calldata data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address payable refundReceiver,
        bytes calldata signatures
    )
        external
        returns (bool success)
    {
        bytes32 txHash;
        // Use scope here to limit variable lifetime and prevent `stack too deep` errors
        {
            bytes memory txHashData = encodeTransactionData(
                to, value, data, operation, // Transaction info
                safeTxGas, baseGas, gasPrice, gasToken, refundReceiver, // Payment info
                nonce
            );
            // Increase nonce and execute transaction.
            nonce++;
            txHash = keccak256(txHashData);
            checkSignatures(txHash, txHashData, signatures, true);
        }
        require(gasleft() >= safeTxGas, "Not enough gas to execute safe transaction");
        // Use scope here to limit variable lifetime and prevent `stack too deep` errors
        {
            uint256 gasUsed = gasleft();
            // If no safeTxGas has been set and the gasPrice is 0 we assume that all available gas can be used
            success = execute(to, value, data, operation, safeTxGas == 0 && gasPrice == 0 ? gasleft() : safeTxGas);
            gasUsed = gasUsed.sub(gasleft());
            // We transfer the calculated tx costs to the tx.origin to avoid sending it to intermediate contracts that have made calls
            uint256 payment = 0;
            if (gasPrice > 0) {
                payment = handlePayment(gasUsed, baseGas, gasPrice, gasToken, refundReceiver);
            }
            if (success) emit ExecutionSuccess(txHash, payment);
            else emit ExecutionFailure(txHash, payment);
        }
    }

    function handlePayment(
        uint256 gasUsed,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address payable refundReceiver
    )
        private
        returns (uint256 payment)
    {
        // solium-disable-next-line security/no-tx-origin
        address payable receiver = refundReceiver == address(0) ? tx.origin : refundReceiver;
        if (gasToken == address(0)) {
            // For ETH we will only adjust the gas price to not be higher than the actual used gas price
            payment = gasUsed.add(baseGas).mul(gasPrice < tx.gasprice ? gasPrice : tx.gasprice);
            // solium-disable-next-line security/no-send
            require(receiver.send(payment), "Could not pay gas costs with ether");
        } else {
            payment = gasUsed.add(baseGas).mul(gasPrice);
            require(transferToken(gasToken, receiver, payment), "Could not pay gas costs with token");
        }
    }

    /**
    * @dev Checks whether the signature provided is valid for the provided data, hash. Will revert otherwise.
    * @param dataHash Hash of the data (could be either a message hash or transaction hash)
    * @param data That should be signed (this is passed to an external validator contract)
    * @param signatures Signature data that should be verified. Can be ECDSA signature, contract signature (EIP-1271) or approved hash.
    * @param consumeHash Indicates that in case of an approved hash the storage can be freed to save gas
    */
    function checkSignatures(bytes32 dataHash, bytes memory data, bytes memory signatures, bool consumeHash)
        internal
    {
        // Load threshold to avoid multiple storage loads
        uint256 _threshold = threshold;
        // Check that a threshold is set
        require(_threshold > 0, "Threshold needs to be defined!");
        // Check that the provided signature data is not too short
        require(signatures.length >= _threshold.mul(65), "Signatures data too short");
        // There cannot be an owner with address 0.
        address lastOwner = address(0);
        address currentOwner;
        uint8 v;
        bytes32 r;
        bytes32 s;
        uint256 i;
        for (i = 0; i < _threshold; i++) {
            (v, r, s) = signatureSplit(signatures, i);
            // If v is 0 then it is a contract signature
            if (v == 0) {
                // When handling contract signatures the address of the contract is encoded into r
                currentOwner = address(uint256(r));

                // Check that signature data pointer (s) is not pointing inside the static part of the signatures bytes
                // This check is not completely accurate, since it is possible that more signatures than the threshold are send.
                // Here we only check that the pointer is not pointing inside the part that is being processed
                require(uint256(s) >= _threshold.mul(65), "Invalid contract signature location: inside static part");

                // Check that signature data pointer (s) is in bounds (points to the length of data -> 32 bytes)
                require(uint256(s).add(32) <= signatures.length, "Invalid contract signature location: length not present");

                // Check if the contract signature is in bounds: start of data is s + 32 and end is start + signature length
                uint256 contractSignatureLen;
                // solium-disable-next-line security/no-inline-assembly
                assembly {
                    contractSignatureLen := mload(add(add(signatures, s), 0x20))
                }
                require(uint256(s).add(32).add(contractSignatureLen) <= signatures.length, "Invalid contract signature location: data not complete");

                // Check signature
                bytes memory contractSignature;
                // solium-disable-next-line security/no-inline-assembly
                assembly {
                    // The signature data for contract signatures is appended to the concatenated signatures and the offset is stored in s
                    contractSignature := add(add(signatures, s), 0x20)
                }
                require(ISignatureValidator(currentOwner).isValidSignature(data, contractSignature) == EIP1271_MAGIC_VALUE, "Invalid contract signature provided");
            // If v is 1 then it is an approved hash
            } else if (v == 1) {
                // When handling approved hashes the address of the approver is encoded into r
                currentOwner = address(uint256(r));
                // Hashes are automatically approved by the sender of the message or when they have been pre-approved via a separate transaction
                require(msg.sender == currentOwner || approvedHashes[currentOwner][dataHash] != 0, "Hash has not been approved");
                // Hash has been marked for consumption. If this hash was pre-approved free storage
                if (consumeHash && msg.sender != currentOwner) {
                    approvedHashes[currentOwner][dataHash] = 0;
                }
            } else if (v > 30) {
                // To support eth_sign and similar we adjust v and hash the messageHash with the Ethereum message prefix before applying ecrecover
                currentOwner = ecrecover(keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", dataHash)), v - 4, r, s);
            } else {
                // Use ecrecover with the messageHash for EOA signatures
                currentOwner = ecrecover(dataHash, v, r, s);
            }
            require (
                currentOwner > lastOwner && owners[currentOwner] != address(0) && currentOwner != SENTINEL_OWNERS,
                "Invalid owner provided"
            );
            lastOwner = currentOwner;
        }
    }

    /// @dev Allows to estimate a Safe transaction.
    ///      This method is only meant for estimation purpose, therefore two different protection mechanism against execution in a transaction have been made:
    ///      1.) The method can only be called from the safe itself
    ///      2.) The response is returned with a revert
    ///      When estimating set `from` to the address of the safe.
    ///      Since the `estimateGas` function includes refunds, call this method to get an estimated of the costs that are deducted from the safe with `execTransaction`
    /// @param to Destination address of Safe transaction.
    /// @param value Ether value of Safe transaction.
    /// @param data Data payload of Safe transaction.
    /// @param operation Operation type of Safe transaction.
    /// @return Estimate without refunds and overhead fees (base transaction and payload data gas costs).
    function requiredTxGas(address to, uint256 value, bytes calldata data, Enum.Operation operation)
        external
        authorized
        returns (uint256)
    {
        uint256 startGas = gasleft();
        // We don't provide an error message here, as we use it to return the estimate
        // solium-disable-next-line error-reason
        require(execute(to, value, data, operation, gasleft()));
        uint256 requiredGas = startGas - gasleft();
        // Convert response to string and return via error message
        revert(string(abi.encodePacked(requiredGas)));
    }

    /**
    * @dev Marks a hash as approved. This can be used to validate a hash that is used by a signature.
    * @param hashToApprove The hash that should be marked as approved for signatures that are verified by this contract.
    */
    function approveHash(bytes32 hashToApprove)
        external
    {
        require(owners[msg.sender] != address(0), "Only owners can approve a hash");
        approvedHashes[msg.sender][hashToApprove] = 1;
        emit ApproveHash(hashToApprove, msg.sender);
    }

    /**
    * @dev Marks a message as signed
    * @param _data Arbitrary length data that should be marked as signed on the behalf of address(this)
    */
    function signMessage(bytes calldata _data)
        external
        authorized
    {
        bytes32 msgHash = getMessageHash(_data);
        signedMessages[msgHash] = 1;
        emit SignMsg(msgHash);
    }

    /**
    * Implementation of ISignatureValidator (see `interfaces/ISignatureValidator.sol`)
    * @dev Should return whether the signature provided is valid for the provided data.
    *       The save does not implement the interface since `checkSignatures` is not a view method.
    *       The method will not perform any state changes (see parameters of `checkSignatures`)
    * @param _data Arbitrary length data signed on the behalf of address(this)
    * @param _signature Signature byte array associated with _data
    * @return a bool upon valid or invalid signature with corresponding _data
    */
    function isValidSignature(bytes calldata _data, bytes calldata _signature)
        external
        returns (bytes4)
    {
        bytes32 messageHash = getMessageHash(_data);
        if (_signature.length == 0) {
            require(signedMessages[messageHash] != 0, "Hash not approved");
        } else {
            // consumeHash needs to be false, as the state should not be changed
            checkSignatures(messageHash, _data, _signature, false);
        }
        return EIP1271_MAGIC_VALUE;
    }

    /// @dev Returns hash of a message that can be signed by owners.
    /// @param message Message that should be hashed
    /// @return Message hash.
    function getMessageHash(
        bytes memory message
    )
        public
        view
        returns (bytes32)
    {
        bytes32 safeMessageHash = keccak256(
            abi.encode(SAFE_MSG_TYPEHASH, keccak256(message))
        );
        return keccak256(
            abi.encodePacked(byte(0x19), byte(0x01), domainSeparator, safeMessageHash)
        );
    }

    /// @dev Returns the bytes that are hashed to be signed by owners.
    /// @param to Destination address.
    /// @param value Ether value.
    /// @param data Data payload.
    /// @param operation Operation type.
    /// @param safeTxGas Fas that should be used for the safe transaction.
    /// @param baseGas Gas costs for data used to trigger the safe transaction.
    /// @param gasPrice Maximum gas price that should be used for this transaction.
    /// @param gasToken Token address (or 0 if ETH) that is used for the payment.
    /// @param refundReceiver Address of receiver of gas payment (or 0 if tx.origin).
    /// @param _nonce Transaction nonce.
    /// @return Transaction hash bytes.
    function encodeTransactionData(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address refundReceiver,
        uint256 _nonce
    )
        public
        view
        returns (bytes memory)
    {
        bytes32 safeTxHash = keccak256(
            abi.encode(SAFE_TX_TYPEHASH, to, value, keccak256(data), operation, safeTxGas, baseGas, gasPrice, gasToken, refundReceiver, _nonce)
        );
        return abi.encodePacked(byte(0x19), byte(0x01), domainSeparator, safeTxHash);
    }

    /// @dev Returns hash to be signed by owners.
    /// @param to Destination address.
    /// @param value Ether value.
    /// @param data Data payload.
    /// @param operation Operation type.
    /// @param safeTxGas Fas that should be used for the safe transaction.
    /// @param baseGas Gas costs for data used to trigger the safe transaction.
    /// @param gasPrice Maximum gas price that should be used for this transaction.
    /// @param gasToken Token address (or 0 if ETH) that is used for the payment.
    /// @param refundReceiver Address of receiver of gas payment (or 0 if tx.origin).
    /// @param _nonce Transaction nonce.
    /// @return Transaction hash.
    function getTransactionHash(
        address to,
        uint256 value,
        bytes memory data,
        Enum.Operation operation,
        uint256 safeTxGas,
        uint256 baseGas,
        uint256 gasPrice,
        address gasToken,
        address refundReceiver,
        uint256 _nonce
    )
        public
        view
        returns (bytes32)
    {
        return keccak256(encodeTransactionData(to, value, data, operation, safeTxGas, baseGas, gasPrice, gasToken, refundReceiver, _nonce));
    }
}