Yearn.Global Token & Chef Contracts - Audit Report

Summary

Hulk Token Audit Report Yearn.Global A Multi Chain DeFi Platform!

Swap, Farm, Earn from staking multiple blockchains tokens with our Pools, which are tailored to give high returns. ERC20 & TRC20 Tokens support available at the time of Launch. More blockchains to be added soon.

Audit completed October 28th, 2020.

Features of the contracts:
  • Rewards are calculated every block by the Chef contract.
  • Once the rewards period ends, no further YG shall be minted. The total supply is expected to be 50,000 YG.
  • Ownership - Some functions are protected and can only be called by the contract owner or developer. The owner can transfer ownership to any address.
  • Utilization of SafeMath to prevent overflows.
Audit Findings Summary
  • Overall, no serious issues were identified.
  • The token's supply is to be limited to 50,000 YG. To achieve this, ownerhsip of the token must be transfered to the Chef contract and the Chef contract's rewards must equal 25,000 YG. Transactions to verify transfer of ownership and reward rates pending.

We ran over 400,000 transactions interacting with this contract on a test blockchain to determine these results.
Date: October 28th, 2020
Vulnerability Category Notes Result
Arbitrary Storage Write N/A PASS
Arbitrary Jump N/A PASS
Delegate Call to Untrusted Contract N/A PASS
Dependence on Predictable Variables N/A PASS
Deprecated Opcodes N/A PASS
Ether Thief N/A PASS
Exceptions N/A PASS
External Calls N/A PASS
Integer Over/Underflow N/A PASS
Multiple Sends N/A PASS
Suicide N/A PASS
State Change External Calls N/A Pass
Unchecked Retval N/A PASS
User Supplied Assertion N/A PASS
Critical Solidity Compiler N/A PASS
Overall Contract Safety   PASS

TRC20 Token Graph

Multi-file Token


 ($) = payable function
 # = non-constant function
 
 Int = Internal
 Ext = External
 Pub = Public
 
 +  Context 
    - [Int] _msgSender
    - [Int] _msgData

 + [Int] IERC20 
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] transfer #
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transferFrom #

 + [Lib] SafeMath 
    - [Int] add
    - [Int] sub
    - [Int] sub
    - [Int] mul
    - [Int] div
    - [Int] div
    - [Int] mod
    - [Int] mod

 + [Lib] Address 
    - [Int] isContract
    - [Int] sendValue #
    - [Int] functionCall #
    - [Int] functionCall #
    - [Int] functionCallWithValue #
    - [Int] functionCallWithValue #
    - [Prv] _functionCallWithValue #

 + [Lib] SafeERC20 
    - [Int] safeTransfer #
    - [Int] safeTransferFrom #
    - [Int] safeApprove #
    - [Int] safeIncreaseAllowance #
    - [Int] safeDecreaseAllowance #
    - [Prv] _callOptionalReturn #

 +  Ownable (Context)
    - [Int]  #
    - [Pub] owner
    - [Pub] renounceOwnership #
       - modifiers: onlyOwner
    - [Pub] transferOwnership #
       - modifiers: onlyOwner

 +  ERC20 (Context, IERC20)
    - [Pub]  #
    - [Pub] name
    - [Pub] symbol
    - [Pub] decimals
    - [Pub] totalSupply
    - [Pub] balanceOf
    - [Pub] transfer #
    - [Pub] allowance
    - [Pub] approve #
    - [Pub] transferFrom #
    - [Pub] increaseAllowance #
    - [Pub] decreaseAllowance #
    - [Int] _transfer #
    - [Int] _mint #
    - [Int] _burn #
    - [Int] _approve #
    - [Int] _setupDecimals #
    - [Int] _beforeTokenTransfer #

 +  YEARNGLOBAL (ERC20, Ownable)
    - [Pub] mint #
       - modifiers: onlyOwner

 +  YGChef (Ownable)
    - [Pub]  #
    - [Ext] poolLength
    - [Pub] add #
       - modifiers: onlyOwner
    - [Pub] set #
       - modifiers: onlyOwner
    - [Pub] getMultiplier
    - [Pub] getRewardPerBlock
    - [Ext] pendingYG
    - [Pub] massUpdatePools #
    - [Pub] updatePool #
    - [Pub] deposit #
    - [Pub] withdraw #
    - [Pub] emergencyWithdraw #
    - [Int] safeYGTransfer #
    - [Pub] dev #
							

Click here to download the source code as a .sol file.


pragma solidity ^0.6.12;

// SPDX-License-Identifier: MIT

/*

 * @dev Provides information about the current execution context, including the

 * sender of the transaction and its data. While these are generally available

 * via msg.sender and msg.data, they should not be accessed in such a direct

 * manner, since when dealing with GSN meta-transactions the account sending and

 * paying for execution may not be the actual sender (as far as an application

 * is concerned).

 *

 * This contract is only required for intermediate, library-like contracts.

 */

abstract contract Context {

    function _msgSender() internal view virtual returns (address payable) {

        return msg.sender;

    }



    function _msgData() internal view virtual returns (bytes memory) {

        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691

        return msg.data;

    }

}



/**

 * @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);

}



/**

 * @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;

    }

}





/**

 * @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);

            }

        }

    }

}



/**

 * @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");

        }

    }

}







/**

 * @dev Contract module which provides a basic access control mechanism, where

 * there is an account (an owner) that can be granted exclusive access to

 * specific functions.

 *

 * By default, the owner account will be the one that deploys the contract. This

 * can later be changed with {transferOwnership}.

 *

 * This module is used through inheritance. It will make available the modifier

 * `onlyOwner`, which can be applied to your functions to restrict their use to

 * the owner.

 */

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;

    }

}





/**

 * @dev Implementation of the {IERC20} interface.

 *

 * This implementation is agnostic to the way tokens are created. This means

 * that a supply mechanism has to be added in a derived contract using {_mint}.

 * For a generic mechanism see {ERC20PresetMinterPauser}.

 *

 * TIP: For a detailed writeup see our guide

 * https://forum.zeppelin.solutions/t/how-to-implement-erc20-supply-mechanisms/226[How

 * to implement supply mechanisms].

 *

 * We have followed general OpenZeppelin guidelines: functions revert instead

 * of returning `false` on failure. This behavior is nonetheless conventional

 * and does not conflict with the expectations of ERC20 applications.

 *

 * Additionally, an {Approval} event is emitted on calls to {transferFrom}.

 * This allows applications to reconstruct the allowance for all accounts just

 * by listening to said events. Other implementations of the EIP may not emit

 * these events, as it isn't required by the specification.

 *

 * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}

 * functions have been added to mitigate the well-known issues around setting

 * allowances. See {IERC20-approve}.

 */

contract ERC20 is Context, IERC20 {

    using SafeMath for uint256;

    using Address for address;



    mapping (address => uint256) private _balances;



    mapping (address => mapping (address => uint256)) private _allowances;



    uint256 private _totalSupply;



    string private _name;

    string private _symbol;

    uint8 private _decimals;



    /**

     * @dev Sets the values for {name} and {symbol}, initializes {decimals} with

     * a default value of 18.

     *

     * To select a different value for {decimals}, use {_setupDecimals}.

     *

     * All three of these values are immutable: they can only be set once during

     * construction.

     */

    constructor (string memory name, string memory symbol) public {

        _name = name;

        _symbol = symbol;

        _decimals = 18;

    }



    /**

     * @dev Returns the name of the token.

     */

    function name() public view returns (string memory) {

        return _name;

    }



    /**

     * @dev Returns the symbol of the token, usually a shorter version of the

     * name.

     */

    function symbol() public view returns (string memory) {

        return _symbol;

    }



    /**

     * @dev Returns the number of decimals used to get its user representation.

     * For example, if `decimals` equals `2`, a balance of `505` tokens should

     * be displayed to a user as `5,05` (`505 / 10 ** 2`).

     *

     * Tokens usually opt for a value of 18, imitating the relationship between

     * Ether and Wei. This is the value {ERC20} uses, unless {_setupDecimals} is

     * called.

     *

     * NOTE: This information is only used for _display_ purposes: it in

     * no way affects any of the arithmetic of the contract, including

     * {IERC20-balanceOf} and {IERC20-transfer}.

     */

    function decimals() public view returns (uint8) {

        return _decimals;

    }



    /**

     * @dev See {IERC20-totalSupply}.

     */

    function totalSupply() public view override returns (uint256) {

        return _totalSupply;

    }



    /**

     * @dev See {IERC20-balanceOf}.

     */

    function balanceOf(address account) public view override returns (uint256) {

        return _balances[account];

    }



    /**

     * @dev See {IERC20-transfer}.

     *

     * Requirements:

     *

     * - `recipient` cannot be the zero address.

     * - the caller must have a balance of at least `amount`.

     */

    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {

        _transfer(_msgSender(), recipient, amount);

        return true;

    }



    /**

     * @dev See {IERC20-allowance}.

     */

    function allowance(address owner, address spender) public view virtual override returns (uint256) {

        return _allowances[owner][spender];

    }



    /**

     * @dev See {IERC20-approve}.

     *

     * Requirements:

     *

     * - `spender` cannot be the zero address.

     */

    function approve(address spender, uint256 amount) public virtual override returns (bool) {

        _approve(_msgSender(), spender, amount);

        return true;

    }



    /**

     * @dev See {IERC20-transferFrom}.

     *

     * Emits an {Approval} event indicating the updated allowance. This is not

     * required by the EIP. See the note at the beginning of {ERC20};

     *

     * Requirements:

     * - `sender` and `recipient` cannot be the zero address.

     * - `sender` must have a balance of at least `amount`.

     * - the caller must have allowance for ``sender``'s tokens of at least

     * `amount`.

     */

    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {

        _transfer(sender, recipient, amount);

        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));

        return true;

    }



    /**

     * @dev Atomically increases the allowance granted to `spender` by the caller.

     *

     * This is an alternative to {approve} that can be used as a mitigation for

     * problems described in {IERC20-approve}.

     *

     * Emits an {Approval} event indicating the updated allowance.

     *

     * Requirements:

     *

     * - `spender` cannot be the zero address.

     */

    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {

        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));

        return true;

    }



    /**

     * @dev Atomically decreases the allowance granted to `spender` by the caller.

     *

     * This is an alternative to {approve} that can be used as a mitigation for

     * problems described in {IERC20-approve}.

     *

     * Emits an {Approval} event indicating the updated allowance.

     *

     * Requirements:

     *

     * - `spender` cannot be the zero address.

     * - `spender` must have allowance for the caller of at least

     * `subtractedValue`.

     */

    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {

        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));

        return true;

    }



    /**

     * @dev Moves tokens `amount` from `sender` to `recipient`.

     *

     * This is internal function is equivalent to {transfer}, and can be used to

     * e.g. implement automatic token fees, slashing mechanisms, etc.

     *

     * Emits a {Transfer} event.

     *

     * Requirements:

     *

     * - `sender` cannot be the zero address.

     * - `recipient` cannot be the zero address.

     * - `sender` must have a balance of at least `amount`.

     */

    function _transfer(address sender, address recipient, uint256 amount) internal virtual {

        require(sender != address(0), "ERC20: transfer from the zero address");

        require(recipient != address(0), "ERC20: transfer to the zero address");



        _beforeTokenTransfer(sender, recipient, amount);



        _balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");

        _balances[recipient] = _balances[recipient].add(amount);

        emit Transfer(sender, recipient, amount);

    }



    /** @dev Creates `amount` tokens and assigns them to `account`, increasing

     * the total supply.

     *

     * Emits a {Transfer} event with `from` set to the zero address.

     *

     * Requirements

     *

     * - `to` cannot be the zero address.

     */

    function _mint(address account, uint256 amount) internal virtual {

        require(account != address(0), "ERC20: mint to the zero address");



        _beforeTokenTransfer(address(0), account, amount);



        _totalSupply = _totalSupply.add(amount);

        _balances[account] = _balances[account].add(amount);

        emit Transfer(address(0), account, amount);

    }



    /**

     * @dev Destroys `amount` tokens from `account`, reducing the

     * total supply.

     *

     * Emits a {Transfer} event with `to` set to the zero address.

     *

     * Requirements

     *

     * - `account` cannot be the zero address.

     * - `account` must have at least `amount` tokens.

     */

    function _burn(address account, uint256 amount) internal virtual {

        require(account != address(0), "ERC20: burn from the zero address");



        _beforeTokenTransfer(account, address(0), amount);



        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");

        _totalSupply = _totalSupply.sub(amount);

        emit Transfer(account, address(0), amount);

    }



    /**

     * @dev Sets `amount` as the allowance of `spender` over the `owner`s tokens.

     *

     * This is internal function is equivalent to `approve`, and can be used to

     * e.g. set automatic allowances for certain subsystems, etc.

     *

     * Emits an {Approval} event.

     *

     * Requirements:

     *

     * - `owner` cannot be the zero address.

     * - `spender` cannot be the zero address.

     */

    function _approve(address owner, address spender, uint256 amount) internal virtual {

        require(owner != address(0), "ERC20: approve from the zero address");

        require(spender != address(0), "ERC20: approve to the zero address");



        _allowances[owner][spender] = amount;

        emit Approval(owner, spender, amount);

    }



    /**

     * @dev Sets {decimals} to a value other than the default one of 18.

     *

     * WARNING: This function should only be called from the constructor. Most

     * applications that interact with token contracts will not expect

     * {decimals} to ever change, and may work incorrectly if it does.

     */

    function _setupDecimals(uint8 decimals_) internal {

        _decimals = decimals_;

    }



    /**

     * @dev Hook that is called before any transfer of tokens. This includes

     * minting and burning.

     *

     * Calling conditions:

     *

     * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens

     * will be to transferred to `to`.

     * - when `from` is zero, `amount` tokens will be minted for `to`.

     * - when `to` is zero, `amount` of ``from``'s tokens will be burned.

     * - `from` and `to` are never both zero.

     *

     * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].

     */

    function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual { }

}



// YEARNGLOBAL with Governance.

contract YEARNGLOBAL is ERC20("YEARN GLOBAL", "YG"), Ownable {

    /// @notice Creates `_amount` token to `_to`. Must only be called by the owner (MasterChef).

    function mint(address _to, uint256 _amount) public onlyOwner {

        _mint(_to, _amount);

    }

}



contract YGChef is Ownable {

    using SafeMath for uint256;

    using SafeERC20 for IERC20;



    // Info of each user.

    struct UserInfo {

        uint256 amount;     // How many LP tokens the user has provided.

        uint256 rewardDebt; // Reward debt. See explanation below.

        //

        // We do some fancy math here. Basically, any point in time, the amount of YGs

        // entitled to a user but is pending to be distributed is:

        //

        //   pending reward = (user.amount * pool.accYGPerShare) - user.rewardDebt

        //

        // Whenever a user deposits or withdraws LP tokens to a pool. Here's what happens:

        //   1. The pool's `accYGPerShare` (and `lastRewardBlock`) gets updated.

        //   2. User receives the pending reward sent to his/her address.

        //   3. User's `amount` gets updated.

        //   4. User's `rewardDebt` gets updated.

    }



    // Info of each pool.

    struct PoolInfo {

        IERC20 lpToken;           // Address of LP token contract.

        uint256 allocPoint;       // How many allocation points assigned to this pool. YGs to distribute per block.

        uint256 lastRewardBlock;  // Last block number that YGs distribution occurs.

        uint256 accYGPerShare; // Accumulated YGs per share, times 1e12. See below.

    }



    // The YG TOKEN!

    YEARNGLOBAL public YG;

    // Dev address.

    address public devaddr;

    // Block number when bonus YG period ends.

    uint256 public bonusEndBlock;

    // YG tokens created per block.

    uint256 public YGPerBlock;

    // Bonus muliplier for early YG makers.

    uint256 public constant BONUS_MULTIPLIER = 1; // no bonus



    // No of blocks in a day  - 7000

    uint256 public constant perDayBlocks = 7000; // no bonus



    // Info of each pool.

    PoolInfo[] public poolInfo;

    // Info of each user that stakes LP tokens.

    mapping (uint256 => mapping (address => UserInfo)) public userInfo;

    // Total allocation poitns. Must be the sum of all allocation points in all pools.

    uint256 public totalAllocPoint = 0;

    // The block number when YG mining starts.

    uint256 public startBlock;



    event Deposit(address indexed user, uint256 indexed pid, uint256 amount);

    event Withdraw(address indexed user, uint256 indexed pid, uint256 amount);

    event EmergencyWithdraw(address indexed user, uint256 indexed pid, uint256 amount);



    constructor(

        YEARNGLOBAL _YG,

        address _devaddr,

        uint256 _YGPerBlock,

        uint256 _startBlock,

        uint256 _bonusEndBlock

    ) public {

        YG = _YG;

        devaddr = _devaddr;

        YGPerBlock = _YGPerBlock;

        bonusEndBlock = _bonusEndBlock;

        startBlock = _startBlock;

    }



    function poolLength() external view returns (uint256) {

        return poolInfo.length;

    }



    // Add a new lp to the pool. Can only be called by the owner.

    // XXX DO NOT add the same LP token more than once. Rewards will be messed up if you do.

    function add(uint256 _allocPoint, IERC20 _lpToken, bool _withUpdate) public onlyOwner {

        if (_withUpdate) {

            massUpdatePools();

        }

        uint256 lastRewardBlock = block.number > startBlock ? block.number : startBlock;

        totalAllocPoint = totalAllocPoint.add(_allocPoint);

        poolInfo.push(PoolInfo({

            lpToken: _lpToken,

            allocPoint: _allocPoint,

            lastRewardBlock: lastRewardBlock,

            accYGPerShare: 0

        }));

    }



    // Update the given pool's YG allocation point. Can only be called by the owner.

    function set(uint256 _pid, uint256 _allocPoint, bool _withUpdate) public onlyOwner {

        if (_withUpdate) {

            massUpdatePools();

        }

        totalAllocPoint = totalAllocPoint.sub(poolInfo[_pid].allocPoint).add(_allocPoint);

        poolInfo[_pid].allocPoint = _allocPoint;

    }







    // Return reward multiplier over the given _from to _to block.

    function getMultiplier(uint256 _from, uint256 _to) public view returns (uint256) {

        if (_to <= bonusEndBlock) {

            return _to.sub(_from).mul(BONUS_MULTIPLIER);

        } else if (_from >= bonusEndBlock) {

            return _to.sub(_from);

        } else {

            return bonusEndBlock.sub(_from).mul(BONUS_MULTIPLIER).add(

                _to.sub(bonusEndBlock)

            );

        }

    }

    

     // reward prediction at specific block

    function getRewardPerBlock(uint blockNumber) public view returns (uint256) {

        if (blockNumber >= startBlock){



            uint256 blockDaysPassed = (blockNumber.sub(startBlock)).div(perDayBlocks);



            if(blockDaysPassed <= 0){

                 return YGPerBlock;

            }



        }

    }



    // View function to see pending YGs on frontend.

    function pendingYG(uint256 _pid, address _user) external view returns (uint256) {

        PoolInfo storage pool = poolInfo[_pid];

        UserInfo storage user = userInfo[_pid][_user];

        uint256 accYGPerShare = pool.accYGPerShare;

        uint256 lpSupply = pool.lpToken.balanceOf(address(this));

        if (block.number > pool.lastRewardBlock && lpSupply != 0) {

            uint256 multiplier = getMultiplier(pool.lastRewardBlock, block.number);

            uint256 rewardThisBlock = getRewardPerBlock(block.number);

            uint256 YGReward = multiplier.mul(rewardThisBlock).mul(pool.allocPoint).div(totalAllocPoint);

            accYGPerShare = accYGPerShare.add(YGReward.mul(1e12).div(lpSupply));

        }

        return user.amount.mul(accYGPerShare).div(1e12).sub(user.rewardDebt);

    }



    // Update reward vairables for all pools. Be careful of gas spending!

    function massUpdatePools() public {

        uint256 length = poolInfo.length;

        for (uint256 pid = 0; pid < length; ++pid) {

            updatePool(pid);

        }

    }





    // Update reward variables of the given pool to be up-to-date.

    function updatePool(uint256 _pid) public {

        PoolInfo storage pool = poolInfo[_pid];

        if (block.number <= pool.lastRewardBlock) {

            return;

        }

        uint256 lpSupply = pool.lpToken.balanceOf(address(this));

        if (lpSupply == 0) {

            pool.lastRewardBlock = block.number;

            return;

        }

        uint256 multiplier = getMultiplier(pool.lastRewardBlock, block.number);

        uint256 rewardThisBlock = getRewardPerBlock(block.number);

        uint256 YGReward = multiplier.mul(rewardThisBlock).mul(pool.allocPoint).div(totalAllocPoint);

        YG.mint(devaddr, YGReward.div(24)); // 4%

        YG.mint(address(this), YGReward);

        pool.accYGPerShare = pool.accYGPerShare.add(YGReward.mul(1e12).div(lpSupply));

        pool.lastRewardBlock = block.number;

    }



    // Deposit LP tokens to MasterChef for YG allocation.

    function deposit(uint256 _pid, uint256 _amount) public {

        PoolInfo storage pool = poolInfo[_pid];

        UserInfo storage user = userInfo[_pid][msg.sender];

        updatePool(_pid);

        if (user.amount > 0) {

            uint256 pending = user.amount.mul(pool.accYGPerShare).div(1e12).sub(user.rewardDebt);

            safeYGTransfer(msg.sender, pending);

        }

        pool.lpToken.safeTransferFrom(address(msg.sender), address(this), _amount);

        user.amount = user.amount.add(_amount);

        user.rewardDebt = user.amount.mul(pool.accYGPerShare).div(1e12);

        emit Deposit(msg.sender, _pid, _amount);

    }



    // Withdraw LP tokens from MasterChef.

    function withdraw(uint256 _pid, uint256 _amount) public {

        PoolInfo storage pool = poolInfo[_pid];

        UserInfo storage user = userInfo[_pid][msg.sender];

        require(user.amount >= _amount, "withdraw: not good");

        updatePool(_pid);

        uint256 pending = user.amount.mul(pool.accYGPerShare).div(1e12).sub(user.rewardDebt);

        safeYGTransfer(msg.sender, pending);

        user.amount = user.amount.sub(_amount);

        user.rewardDebt = user.amount.mul(pool.accYGPerShare).div(1e12);

        pool.lpToken.safeTransfer(address(msg.sender), _amount);

        emit Withdraw(msg.sender, _pid, _amount);

    }



    // Withdraw without caring about rewards. EMERGENCY ONLY.

    function emergencyWithdraw(uint256 _pid) public {

        PoolInfo storage pool = poolInfo[_pid];

        UserInfo storage user = userInfo[_pid][msg.sender];

        pool.lpToken.safeTransfer(address(msg.sender), user.amount);

        emit EmergencyWithdraw(msg.sender, _pid, user.amount);

        user.amount = 0;

        user.rewardDebt = 0;

    }



    // Safe YG transfer function, just in case if rounding error causes pool to not have enough YGs.

    function safeYGTransfer(address _to, uint256 _amount) internal {

        uint256 YGBal = YG.balanceOf(address(this));

        if (_amount > YGBal) {

            YG.transfer(_to, YGBal);

        } else {

            YG.transfer(_to, _amount);

        }

    }



    // Update dev address by the previous dev.

    function dev(address _devaddr) public {

        require(msg.sender == devaddr, "dev: wut?");

        devaddr = _devaddr;

    }

}