// Vulnerability label: DC1
pragma solidity 0.5.15;


// YAM v3 Token Proxy

/**
 * @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;
    }
}


// Storage for a YAM token
contract YAMTokenStorage {

    using SafeMath for uint256;

    /**
     * @dev Guard variable for re-entrancy checks. Not currently used
     */
    bool internal _notEntered;

    /**
     * @notice EIP-20 token name for this token
     */
    string public name;

    /**
     * @notice EIP-20 token symbol for this token
     */
    string public symbol;

    /**
     * @notice EIP-20 token decimals for this token
     */
    uint8 public decimals;

    /**
     * @notice Governor for this contract
     */
    address public gov;

    /**
     * @notice Pending governance for this contract
     */
    address public pendingGov;

    /**
     * @notice Approved rebaser for this contract
     */
    address public rebaser;

    /**
     * @notice Approved migrator for this contract
     */
    address public migrator;

    /**
     * @notice Incentivizer address of YAM protocol
     */
    address public incentivizer;

    /**
     * @notice Total supply of YAMs
     */
    uint256 public totalSupply;

    /**
     * @notice Internal decimals used to handle scaling factor
     */
    uint256 public constant internalDecimals = 10**24;

    /**
     * @notice Used for percentage maths
     */
    uint256 public constant BASE = 10**18;

    /**
     * @notice Scaling factor that adjusts everyone's balances
     */
    uint256 public yamsScalingFactor;

    mapping (address => uint256) internal _yamBalances;

    mapping (address => mapping (address => uint256)) internal _allowedFragments;

    uint256 public initSupply;


    // keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH = 0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;
    bytes32 public DOMAIN_SEPARATOR;
}

/* Copyright 2020 Compound Labs, Inc.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */


contract YAMGovernanceStorage {
    /// @notice A record of each accounts delegate
    mapping (address => address) internal _delegates;

    /// @notice A checkpoint for marking number of votes from a given block
    struct Checkpoint {
        uint32 fromBlock;
        uint256 votes;
    }

    /// @notice A record of votes checkpoints for each account, by index
    mapping (address => mapping (uint32 => Checkpoint)) public checkpoints;

    /// @notice The number of checkpoints for each account
    mapping (address => uint32) public numCheckpoints;

    /// @notice The EIP-712 typehash for the contract's domain
    bytes32 public constant DOMAIN_TYPEHASH = keccak256("EIP712Domain(string name,uint256 chainId,address verifyingContract)");

    /// @notice The EIP-712 typehash for the delegation struct used by the contract
    bytes32 public constant DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");

    /// @notice A record of states for signing / validating signatures
    mapping (address => uint) public nonces;
}


contract YAMTokenInterface is YAMTokenStorage, YAMGovernanceStorage {

    /// @notice An event thats emitted when an account changes its delegate
    event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);

    /// @notice An event thats emitted when a delegate account's vote balance changes
    event DelegateVotesChanged(address indexed delegate, uint previousBalance, uint newBalance);

    /**
     * @notice Event emitted when tokens are rebased
     */
    event Rebase(uint256 epoch, uint256 prevYamsScalingFactor, uint256 newYamsScalingFactor);

    /*** Gov Events ***/

    /**
     * @notice Event emitted when pendingGov is changed
     */
    event NewPendingGov(address oldPendingGov, address newPendingGov);

    /**
     * @notice Event emitted when gov is changed
     */
    event NewGov(address oldGov, address newGov);

    /**
     * @notice Sets the rebaser contract
     */
    event NewRebaser(address oldRebaser, address newRebaser);

    /**
     * @notice Sets the migrator contract
     */
    event NewMigrator(address oldMigrator, address newMigrator);

    /**
     * @notice Sets the incentivizer contract
     */
    event NewIncentivizer(address oldIncentivizer, address newIncentivizer);

    /* - ERC20 Events - */

    /**
     * @notice EIP20 Transfer event
     */
    event Transfer(address indexed from, address indexed to, uint amount);

    /**
     * @notice EIP20 Approval event
     */
    event Approval(address indexed owner, address indexed spender, uint amount);

    /* - Extra Events - */
    /**
     * @notice Tokens minted event
     */
    event Mint(address to, uint256 amount);

    // Public functions
    function transfer(address to, uint256 value) external returns(bool);
    function transferFrom(address from, address to, uint256 value) external returns(bool);
    function balanceOf(address who) external view returns(uint256);
    function balanceOfUnderlying(address who) external view returns(uint256);
    function allowance(address owner_, address spender) external view returns(uint256);
    function approve(address spender, uint256 value) external returns (bool);
    function increaseAllowance(address spender, uint256 addedValue) external returns (bool);
    function decreaseAllowance(address spender, uint256 subtractedValue) external returns (bool);
    function maxScalingFactor() external view returns (uint256);
    function yamToFragment(uint256 yam) external view returns (uint256);
    function fragmentToYam(uint256 value) external view returns (uint256);

    /* - Governance Functions - */
    function getPriorVotes(address account, uint blockNumber) external view returns (uint256);
    function delegateBySig(address delegatee, uint nonce, uint expiry, uint8 v, bytes32 r, bytes32 s) external;
    function delegate(address delegatee) external;
    function delegates(address delegator) external view returns (address);
    function getCurrentVotes(address account) external view returns (uint256);

    /* - Permissioned/Governance functions - */
    function mint(address to, uint256 amount) external returns (bool);
    function rebase(uint256 epoch, uint256 indexDelta, bool positive) external returns (uint256);
    function _setRebaser(address rebaser_) external;
    function _setIncentivizer(address incentivizer_) external;
    function _setPendingGov(address pendingGov_) external;
    function _acceptGov() external;
}

contract YAMDelegationStorage {
    /**
     * @notice Implementation address for this contract
     */
    address public implementation;
}

contract YAMDelegatorInterface is YAMDelegationStorage {
    /**
     * @notice Emitted when implementation is changed
     */
    event NewImplementation(address oldImplementation, address newImplementation);

    /**
     * @notice Called by the gov to update the implementation of the delegator
     * @param implementation_ The address of the new implementation for delegation
     * @param allowResign Flag to indicate whether to call _resignImplementation on the old implementation
     * @param becomeImplementationData The encoded bytes data to be passed to _becomeImplementation
     */
    function _setImplementation(address implementation_, bool allowResign, bytes memory becomeImplementationData) public;
}


contract YAMDelegator is YAMTokenInterface, YAMDelegatorInterface {
    /**
     * @notice Construct a new YAM
     * @param name_ ERC-20 name of this token
     * @param symbol_ ERC-20 symbol of this token
     * @param decimals_ ERC-20 decimal precision of this token
     * @param initTotalSupply_ Initial token amount
     * @param implementation_ The address of the implementation the contract delegates to
     * @param becomeImplementationData The encoded args for becomeImplementation
     */
    constructor(
        string memory name_,
        string memory symbol_,
        uint8 decimals_,
        uint256 initTotalSupply_,
        address implementation_,
        bytes memory becomeImplementationData
    )
        public
    {


        // Creator of the contract is gov during initialization
        gov = msg.sender;

        // First delegate gets to initialize the delegator (i.e. storage contract)
        delegateTo(
            implementation_,
            abi.encodeWithSignature(
                "initialize(string,string,uint8,address,uint256)",
                name_,
                symbol_,
                decimals_,
                msg.sender,
                initTotalSupply_
            )
        );

        // New implementations always get set via the settor (post-initialize)
        _setImplementation(implementation_, false, becomeImplementationData);

    }

    /**
     * @notice Called by the gov to update the implementation of the delegator
     * @param implementation_ The address of the new implementation for delegation
     * @param allowResign Flag to indicate whether to call _resignImplementation on the old implementation
     * @param becomeImplementationData The encoded bytes data to be passed to _becomeImplementation
     */
    function _setImplementation(address implementation_, bool allowResign, bytes memory becomeImplementationData) public {
        require(msg.sender == gov, "YAMDelegator::_setImplementation: Caller must be gov");

        if (allowResign) {
            delegateToImplementation(abi.encodeWithSignature("_resignImplementation()"));
        }

        address oldImplementation = implementation;
        implementation = implementation_;

        delegateToImplementation(abi.encodeWithSignature("_becomeImplementation(bytes)", becomeImplementationData));

        emit NewImplementation(oldImplementation, implementation);
    }

    /**
     * @notice Sender supplies assets into the market and receives cTokens in exchange
     * @dev Accrues interest whether or not the operation succeeds, unless reverted
     * @param mintAmount The amount of the underlying asset to supply
     * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
     */
    function mint(address to, uint256 mintAmount)
        external
        returns (bool)
    {
        to; mintAmount; // Shh
        delegateAndReturn();
    }

    /**
     * @notice Transfer `amount` tokens from `msg.sender` to `dst`
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transfer(address dst, uint256 amount)
        external
        returns (bool)
    {
        dst; amount; // Shh
        delegateAndReturn();
    }

    /**
     * @notice Transfer `amount` tokens from `src` to `dst`
     * @param src The address of the source account
     * @param dst The address of the destination account
     * @param amount The number of tokens to transfer
     * @return Whether or not the transfer succeeded
     */
    function transferFrom(
        address src,
        address dst,
        uint256 amount
    )
        external
        returns (bool)
    {
        src; dst; amount; // Shh
        delegateAndReturn();
    }

    /**
     * @notice Approve `spender` to transfer up to `amount` from `src`
     * @dev This will overwrite the approval amount for `spender`
     *  and is subject to issues noted [here](https://eips.ethereum.org/EIPS/eip-20#approve)
     * @param spender The address of the account which may transfer tokens
     * @param amount The number of tokens that are approved (-1 means infinite)
     * @return Whether or not the approval succeeded
     */
    function approve(
        address spender,
        uint256 amount
    )
        external
        returns (bool)
    {
        spender; amount; // Shh
        delegateAndReturn();
    }

    /**
     * @dev Increase the amount of tokens that an owner has allowed to a spender.
     * This method should be used instead of approve() to avoid the double approval vulnerability
     * described above.
     * @param spender The address which will spend the funds.
     * @param addedValue The amount of tokens to increase the allowance by.
     */
    function increaseAllowance(
        address spender,
        uint256 addedValue
    )
        external
        returns (bool)
    {
        spender; addedValue; // Shh
        delegateAndReturn();
    }



    function maxScalingFactor()
        external
        view
        returns (uint256)
    {
        delegateToViewAndReturn();
    }

    function rebase(
        uint256 epoch,
        uint256 indexDelta,
        bool positive
    )
        external
        returns (uint256)
    {
        epoch; indexDelta; positive;
        delegateAndReturn();
    }

    /**
     * @dev Decrease the amount of tokens that an owner has allowed to a spender.
     *
     * @param spender The address which will spend the funds.
     * @param subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseAllowance(
        address spender,
        uint256 subtractedValue
    )
        external
        returns (bool)
    {
        spender; subtractedValue; // Shh
        delegateAndReturn();
    }


    // --- Approve by signature ---
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    )
        external
    {
        owner; spender; value; deadline; v; r; s; // Shh
        delegateAndReturn();
    }

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param owner The address of the account which owns the tokens to be spent
     * @param spender The address of the account which may transfer tokens
     * @return The number of tokens allowed to be spent (-1 means infinite)
     */
    function allowance(
        address owner,
        address spender
    )
        external
        view
        returns (uint256)
    {
        owner; spender; // Shh
        delegateToViewAndReturn();
    }


    /**
     * @notice Rescues tokens and sends them to the `to` address
     * @param token The address of the token
     * @param to The address for which the tokens should be send
     * @return Success
     */
    function rescueTokens(
        address token,
        address to,
        uint256 amount
    )
        external
        returns (bool)
    {
        token; to; amount; // Shh
        delegateAndReturn();
    }

    /**
     * @notice Get the current allowance from `owner` for `spender`
     * @param delegator The address of the account which has designated a delegate
     * @return Address of delegatee
     */
    function delegates(
        address delegator
    )
        external
        view
        returns (address)
    {
        delegator; // Shh
        delegateToViewAndReturn();
    }

    /**
     * @notice Get the token balance of the `owner`
     * @param owner The address of the account to query
     * @return The number of tokens owned by `owner`
     */
    function balanceOf(address owner)
        external
        view
        returns (uint256)
    {
        owner; // Shh
        delegateToViewAndReturn();
    }

    /**
     * @notice Currently unused. For future compatability
     * @param owner The address of the account to query
     * @return The number of underlying tokens owned by `owner`
     */
    function balanceOfUnderlying(address owner)
        external
        view
        returns (uint256)
    {
        owner; // Shh
        delegateToViewAndReturn();
    }

    /*** Gov Functions ***/

    /**
      * @notice Begins transfer of gov rights. The newPendingGov must call `_acceptGov` to finalize the transfer.
      * @dev Gov function to begin change of gov. The newPendingGov must call `_acceptGov` to finalize the transfer.
      * @param newPendingGov New pending gov.
      */
    function _setPendingGov(address newPendingGov)
        external
    {
        newPendingGov; // Shh
        delegateAndReturn();
    }

    function _setRebaser(address rebaser_)
        external
    {
        rebaser_; // Shh
        delegateAndReturn();
    }

    function _setIncentivizer(address incentivizer_)
        external
    {
        incentivizer_; // Shh
        delegateAndReturn();
    }

    function _setMigrator(address migrator_)
        external
    {
        migrator_; // Shh
        delegateAndReturn();
    }

    /**
      * @notice Accepts transfer of gov rights. msg.sender must be pendingGov
      * @dev Gov function for pending gov to accept role and update gov
      * @return uint 0=success, otherwise a failure (see ErrorReporter.sol for details)
      */
    function _acceptGov()
        external
    {
        delegateAndReturn();
    }


    function getPriorVotes(address account, uint blockNumber)
        external
        view
        returns (uint256)
    {
        account; blockNumber;
        delegateToViewAndReturn();
    }

    function delegateBySig(
        address delegatee,
        uint nonce,
        uint expiry,
        uint8 v,
        bytes32 r,
        bytes32 s
    )
        external
    {
        delegatee; nonce; expiry; v; r; s;
        delegateAndReturn();
    }

    function delegate(address delegatee)
        external
    {
        delegatee;
        delegateAndReturn();
    }

    function getCurrentVotes(address account)
        external
        view
        returns (uint256)
    {
        account;
        delegateToViewAndReturn();
    }


    function yamToFragment(uint256 yam)
        external
        view
        returns (uint256)
    {
        yam;
        delegateToViewAndReturn();
    }

    function fragmentToYam(uint256 value)
        external
        view
        returns (uint256)
    {
        value;
        delegateToViewAndReturn();
    }

    /**
     * @notice Internal method to delegate execution to another contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     * @param callee The contract to delegatecall
     * @param data The raw data to delegatecall
     * @return The returned bytes from the delegatecall
     */
    function delegateTo(address callee, bytes memory data) internal returns (bytes memory) {
        (bool success, bytes memory returnData) = callee.delegatecall(data);
        assembly {
            if eq(success, 0) {
                revert(add(returnData, 0x20), returndatasize)
            }
        }
        return returnData;
    }

    /**
     * @notice Delegates execution to the implementation contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     * @param data The raw data to delegatecall
     * @return The returned bytes from the delegatecall
     */
    function delegateToImplementation(bytes memory data) public returns (bytes memory) {
        return delegateTo(implementation, data);
    }

    /**
     * @notice Delegates execution to an implementation contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     *  There are an additional 2 prefix uints from the wrapper returndata, which we ignore since we make an extra hop.
     * @param data The raw data to delegatecall
     * @return The returned bytes from the delegatecall
     */
    function delegateToViewImplementation(bytes memory data) public view returns (bytes memory) {
        (bool success, bytes memory returnData) = address(this).staticcall(abi.encodeWithSignature("delegateToImplementation(bytes)", data));
        assembly {
            if eq(success, 0) {
                revert(add(returnData, 0x20), returndatasize)
            }
        }
        return abi.decode(returnData, (bytes));
    }

    function delegateToViewAndReturn() private view returns (bytes memory) {
        (bool success, ) = address(this).staticcall(abi.encodeWithSignature("delegateToImplementation(bytes)", msg.data));

        assembly {
            let free_mem_ptr := mload(0x40)
            returndatacopy(free_mem_ptr, 0, returndatasize)

            switch success
            case 0 { revert(free_mem_ptr, returndatasize) }
            default { return(add(free_mem_ptr, 0x40), sub(returndatasize, 0x40)) }
        }
    }

    function delegateAndReturn() private returns (bytes memory) {
        (bool success, ) = implementation.delegatecall(msg.data);

        assembly {
            let free_mem_ptr := mload(0x40)
            returndatacopy(free_mem_ptr, 0, returndatasize)

            switch success
            case 0 { revert(free_mem_ptr, returndatasize) }
            default { return(free_mem_ptr, returndatasize) }
        }
    }

    /**
     * @notice Delegates execution to an implementation contract
     * @dev It returns to the external caller whatever the implementation returns or forwards reverts
     */
    function() external payable {
        require(msg.value == 0,"YAMDelegator:fallback: cannot send value to fallback");

        // delegate all other functions to current implementation
        delegateAndReturn();
    }
}