PYUSDImplementation.sol

pragma solidity ^0.4.24;
pragma experimental "v0.5.0";


import "./zeppelin/SafeMath.sol";


/**
 * @title PYUSDImplementation
 * @dev this contract is a Pausable ERC20 token with Burn and Mint
 * controlled by a central SupplyController. By implementing PYUSDImplementation
 * this contract also includes external methods for setting
 * a new implementation contract for the Proxy.
 * NOTE: The storage defined here will actually be held in the Proxy
 * contract and all calls to this contract should be made through
 * the proxy, including admin actions done as owner or supplyController.
 * Any call to transfer against this contract should fail
 * with insufficient funds since no tokens will be issued there.
 */
contract PYUSDImplementation {

    /**
     * MATH
     */

    using SafeMath for uint256;

    /**
     * DATA
     */

    // INITIALIZATION DATA
    bool private initialized;

    // ERC20 BASIC DATA
    mapping(address => uint256) internal balances;
    uint256 internal totalSupply_;
    string public constant name = "PayPal USD"; // solium-disable-line
    string public constant symbol = "PYUSD"; // solium-disable-line uppercase
    uint8 public constant decimals = 6; // solium-disable-line uppercase

    // ERC20 DATA
    mapping(address => mapping(address => uint256)) internal allowed;

    // OWNER DATA PART 1
    address public owner;

    // PAUSABILITY DATA
    bool public paused;

    // ASSET PROTECTION DATA
    address public assetProtectionRole;
    mapping(address => bool) internal frozen;

    // SUPPLY CONTROL DATA
    address public supplyController;

    // OWNER DATA PART 2
    address public proposedOwner;

    // DELEGATED TRANSFER DATA
    address public betaDelegateWhitelister;
    mapping(address => bool) internal betaDelegateWhitelist;
    mapping(address => uint256) internal nextSeqs;
    // EIP191 header for EIP712 prefix
    string constant internal EIP191_HEADER = "\x19\x01";
    // Hash of the EIP712 Domain Separator Schema
    bytes32 constant internal EIP712_DOMAIN_SEPARATOR_SCHEMA_HASH = keccak256(
        "EIP712Domain(string name,address verifyingContract)"
    );
    bytes32 constant internal EIP712_DELEGATED_TRANSFER_SCHEMA_HASH = keccak256(
        "BetaDelegatedTransfer(address to,uint256 value,uint256 fee,uint256 seq,uint256 deadline)"
    );
    // Hash of the EIP712 Domain Separator data
    // solhint-disable-next-line var-name-mixedcase
    bytes32 public EIP712_DOMAIN_HASH;

    /**
     * EVENTS
     */

    // ERC20 BASIC EVENTS
    event Transfer(address indexed from, address indexed to, uint256 value);

    // ERC20 EVENTS
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );

    // OWNABLE EVENTS
    event OwnershipTransferProposed(
        address indexed currentOwner,
        address indexed proposedOwner
    );
    event OwnershipTransferDisregarded(
        address indexed oldProposedOwner
    );
    event OwnershipTransferred(
        address indexed oldOwner,
        address indexed newOwner
    );

    // PAUSABLE EVENTS
    event Pause();
    event Unpause();

    // ASSET PROTECTION EVENTS
    event AddressFrozen(address indexed addr);
    event AddressUnfrozen(address indexed addr);
    event FrozenAddressWiped(address indexed addr);
    event AssetProtectionRoleSet (
        address indexed oldAssetProtectionRole,
        address indexed newAssetProtectionRole
    );

    // SUPPLY CONTROL EVENTS
    event SupplyIncreased(address indexed to, uint256 value);
    event SupplyDecreased(address indexed from, uint256 value);
    event SupplyControllerSet(
        address indexed oldSupplyController,
        address indexed newSupplyController
    );

    // DELEGATED TRANSFER EVENTS
    event BetaDelegatedTransfer(
        address indexed from, address indexed to, uint256 value, uint256 seq, uint256 fee
    );
    event BetaDelegateWhitelisterSet(
        address indexed oldWhitelister,
        address indexed newWhitelister
    );
    event BetaDelegateWhitelisted(address indexed newDelegate);
    event BetaDelegateUnwhitelisted(address indexed oldDelegate);

    /**
     * FUNCTIONALITY
     */

    // INITIALIZATION FUNCTIONALITY

    /**
     * @dev sets 0 initials tokens, the owner, and the supplyController.
     * this serves as the constructor for the proxy but compiles to the
     * memory model of the Implementation contract.
     */
    function initialize() public {
        require(!initialized, "MANDATORY VERIFICATION REQUIRED: The proxy has already been initialized, verify the owner and supply controller addresses.");
        owner = msg.sender;
        assetProtectionRole = address(0);
        totalSupply_ = 0;
        supplyController = msg.sender;
        initializeDomainSeparator();
        initialized = true;
    }

    /**
     * The constructor is used here to ensure that the implementation
     * contract is initialized. An uncontrolled implementation
     * contract might lead to misleading state
     * for users who accidentally interact with it.
     */
    constructor() public {
        initialize();
        pause();
    }

    /**
     * @dev To be called when upgrading the contract using upgradeAndCall to add delegated transfers
     */
    function initializeDomainSeparator() private {
        // hash the name context with the contract address
        EIP712_DOMAIN_HASH = keccak256(abi.encodePacked(// solium-disable-line
                EIP712_DOMAIN_SEPARATOR_SCHEMA_HASH,
                keccak256(bytes(name)),
                bytes32(address(this))
            ));
    }

    // ERC20 BASIC FUNCTIONALITY

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }

    /**
    * @dev Transfer token to a specified address from msg.sender
    * Note: the use of Safemath ensures that _value is nonnegative.
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) {
        require(_to != address(0), "cannot transfer to address zero");
        require(!frozen[_to] && !frozen[msg.sender], "address frozen");
        require(_value <= balances[msg.sender], "insufficient funds");

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _addr The address to query the the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address _addr) public view returns (uint256) {
        return balances[_addr];
    }

    // ERC20 FUNCTIONALITY

    /**
     * @dev Transfer tokens from one address to another
     * @param _from address The address which you want to send tokens from
     * @param _to address The address which you want to transfer to
     * @param _value uint256 the amount of tokens to be transferred
     */
    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    whenNotPaused
    returns (bool)
    {
        require(_to != address(0), "cannot transfer to address zero");
        require(!frozen[_to] && !frozen[_from] && !frozen[msg.sender], "address frozen");
        require(_value <= balances[_from], "insufficient funds");
        require(_value <= allowed[_from][msg.sender], "insufficient allowance");

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * 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
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     */
    function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) {
        require(!frozen[_spender] && !frozen[msg.sender], "address frozen");
        allowed[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    /**
     * @dev Increase the amount of tokens that an owner allowed to a spender.
     *
     * To increment allowed value is better to use this function to avoid 2 calls (and wait until the first transaction
     * is mined) instead of approve.
     * @param _spender The address which will spend the funds.
     * @param _addedValue The amount of tokens to increase the allowance by.
     */
    function increaseApproval(address _spender, uint _addedValue) public whenNotPaused returns (bool) {
        require(!frozen[_spender] && !frozen[msg.sender], "address frozen");
        allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_addedValue);
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner allowed to a spender.
     *
     * To decrement allowed value is better to use this function to avoid 2 calls (and wait until the first transaction
     * is mined) instead of approve.
     * @param _spender The address which will spend the funds.
     * @param _subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseApproval(address _spender, uint _subtractedValue) public whenNotPaused returns (bool) {
        require(!frozen[_spender] && !frozen[msg.sender], "address frozen");
        uint oldValue = allowed[msg.sender][_spender];
        if (_subtractedValue > oldValue) {
            allowed[msg.sender][_spender] = 0;
        } else {
            allowed[msg.sender][_spender] = oldValue.sub(_subtractedValue);
        }
        emit Approval(msg.sender, _spender, allowed[msg.sender][_spender]);
        return true;
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param _owner address The address which owns the funds.
     * @param _spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(
        address _owner,
        address _spender
    )
    public
    view
    returns (uint256)
    {
        return allowed[_owner][_spender];
    }

    // OWNER FUNCTIONALITY

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner, "onlyOwner");
        _;
    }

    /**
         * @dev Allows the current owner to begin transferring control of the contract to a proposedOwner
         * @param _proposedOwner The address to transfer ownership to.
         */
    function proposeOwner(address _proposedOwner) public onlyOwner {
        require(_proposedOwner != address(0), "cannot transfer ownership to address zero");
        require(msg.sender != _proposedOwner, "caller already is owner");
        proposedOwner = _proposedOwner;
        emit OwnershipTransferProposed(owner, proposedOwner);
    }
    /**
     * @dev Allows the current owner or proposed owner to cancel transferring control of the contract to a proposedOwner
     */
    function disregardProposeOwner() public {
        require(msg.sender == proposedOwner || msg.sender == owner, "only proposedOwner or owner");
        require(proposedOwner != address(0), "can only disregard a proposed owner that was previously set");
        address _oldProposedOwner = proposedOwner;
        proposedOwner = address(0);
        emit OwnershipTransferDisregarded(_oldProposedOwner);
    }
    /**
     * @dev Allows the proposed owner to complete transferring control of the contract to the proposedOwner.
     */
    function claimOwnership() public {
        require(msg.sender == proposedOwner, "onlyProposedOwner");
        address _oldOwner = owner;
        owner = proposedOwner;
        proposedOwner = address(0);
        emit OwnershipTransferred(_oldOwner, owner);
    }

    /**
     * @dev Reclaim all PYUSD at the contract address.
     * This sends the PYUSD tokens that this contract add holding to the owner.
     * Note: this is not affected by freeze constraints.
     */
    function reclaimPYUSD() external onlyOwner {
        uint256 _balance = balances[this];
        balances[this] = 0;
        balances[owner] = balances[owner].add(_balance);
        emit Transfer(this, owner, _balance);
    }

    // PAUSABILITY FUNCTIONALITY

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

    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() public onlyOwner {
        require(!paused, "already paused");
        paused = true;
        emit Pause();
    }

    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() public onlyOwner {
        require(paused, "already unpaused");
        paused = false;
        emit Unpause();
    }

    // ASSET PROTECTION FUNCTIONALITY

    /**
     * @dev Sets a new asset protection role address.
     * @param _newAssetProtectionRole The new address allowed to freeze/unfreeze addresses and seize their tokens.
     */
    function setAssetProtectionRole(address _newAssetProtectionRole) public {
        require(msg.sender == assetProtectionRole || msg.sender == owner, "only assetProtectionRole or Owner");
        require(assetProtectionRole != _newAssetProtectionRole, "new address is same as a current one");
        emit AssetProtectionRoleSet(assetProtectionRole, _newAssetProtectionRole);
        assetProtectionRole = _newAssetProtectionRole;
    }

    modifier onlyAssetProtectionRole() {
        require(msg.sender == assetProtectionRole, "onlyAssetProtectionRole");
        _;
    }

    /**
     * @dev Freezes an address balance from being transferred.
     * @param _addr The new address to freeze.
     */
    function freeze(address _addr) public onlyAssetProtectionRole {
        require(!frozen[_addr], "address already frozen");
        frozen[_addr] = true;
        emit AddressFrozen(_addr);
    }

    /**
     * @dev Unfreezes an address balance allowing transfer.
     * @param _addr The new address to unfreeze.
     */
    function unfreeze(address _addr) public onlyAssetProtectionRole {
        require(frozen[_addr], "address already unfrozen");
        frozen[_addr] = false;
        emit AddressUnfrozen(_addr);
    }

    /**
     * @dev Wipes the balance of a frozen address, and burns the tokens.
     * @param _addr The new frozen address to wipe.
     */
    function wipeFrozenAddress(address _addr) public onlyAssetProtectionRole {
        require(frozen[_addr], "address is not frozen");
        uint256 _balance = balances[_addr];
        balances[_addr] = 0;
        totalSupply_ = totalSupply_.sub(_balance);
        emit FrozenAddressWiped(_addr);
        emit SupplyDecreased(_addr, _balance);
        emit Transfer(_addr, address(0), _balance);
    }

    /**
    * @dev Gets whether the address is currently frozen.
    * @param _addr The address to check if frozen.
    * @return A bool representing whether the given address is frozen.
    */
    function isFrozen(address _addr) public view returns (bool) {
        return frozen[_addr];
    }

    // SUPPLY CONTROL FUNCTIONALITY

    /**
     * @dev Sets a new supply controller address.
     * @param _newSupplyController The address allowed to burn/mint tokens to control supply.
     */
    function setSupplyController(address _newSupplyController) public {
        require(msg.sender == supplyController || msg.sender == owner, "only SupplyController or Owner");
        require(_newSupplyController != address(0), "cannot set supply controller to address zero");
        require(supplyController != _newSupplyController, "new address is same as a current one");
        emit SupplyControllerSet(supplyController, _newSupplyController);
        supplyController = _newSupplyController;
    }

    modifier onlySupplyController() {
        require(msg.sender == supplyController, "onlySupplyController");
        _;
    }

    /**
     * @dev Increases the total supply by minting the specified number of tokens to the supply controller account.
     * @param _value The number of tokens to add.
     * @return A boolean that indicates if the operation was successful.
     */
    function increaseSupply(uint256 _value) public onlySupplyController returns (bool success) {
        totalSupply_ = totalSupply_.add(_value);
        balances[supplyController] = balances[supplyController].add(_value);
        emit SupplyIncreased(supplyController, _value);
        emit Transfer(address(0), supplyController, _value);
        return true;
    }

    /**
     * @dev Decreases the total supply by burning the specified number of tokens from the supply controller account.
     * @param _value The number of tokens to remove.
     * @return A boolean that indicates if the operation was successful.
     */
    function decreaseSupply(uint256 _value) public onlySupplyController returns (bool success) {
        require(_value <= balances[supplyController], "not enough supply");
        balances[supplyController] = balances[supplyController].sub(_value);
        totalSupply_ = totalSupply_.sub(_value);
        emit SupplyDecreased(supplyController, _value);
        emit Transfer(supplyController, address(0), _value);
        return true;
    }

    // DELEGATED TRANSFER FUNCTIONALITY

    /**
     * @dev returns the next seq for a target address.
     * The transactor must submit nextSeqOf(transactor) in the next transaction for it to be valid.
     * Note: that the seq context is specific to this smart contract.
     * @param target The target address.
     * @return the seq.
     */
    //
    function nextSeqOf(address target) public view returns (uint256) {
        return nextSeqs[target];
    }

    /**
     * @dev Performs a transfer on behalf of the from address, identified by its signature on the delegatedTransfer msg.
     * Splits a signature byte array into r,s,v for convenience.
     * @param sig the signature of the delgatedTransfer msg.
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     * @param fee an optional ERC20 fee paid to the executor of betaDelegatedTransfer by the from address.
     * @param seq a sequencing number included by the from address specific to this contract to protect from replays.
     * @param deadline a block number after which the pre-signed transaction has expired.
     * @return A boolean that indicates if the operation was successful.
     */
    function betaDelegatedTransfer(
        bytes sig, address to, uint256 value, uint256 fee, uint256 seq, uint256 deadline
    ) public returns (bool) {
        require(sig.length == 65, "signature should have length 65");
        bytes32 r;
        bytes32 s;
        uint8 v;
        assembly {
            r := mload(add(sig, 32))
            s := mload(add(sig, 64))
            v := byte(0, mload(add(sig, 96)))
        }
        _betaDelegatedTransfer(r, s, v, to, value, fee, seq, deadline);
        return true;
    }

    /**
     * @dev Performs a transfer on behalf of the from address, identified by its signature on the betaDelegatedTransfer msg.
     * Note: both the delegate and transactor sign in the fees. The transactor, however,
     * has no control over the gas price, and therefore no control over the transaction time.
     * Beta prefix chosen to avoid a name clash with an emerging standard in ERC865 or elsewhere.
     * Internal to the contract - see betaDelegatedTransfer and betaDelegatedTransferBatch.
     * @param r the r signature of the delgatedTransfer msg.
     * @param s the s signature of the delgatedTransfer msg.
     * @param v the v signature of the delgatedTransfer msg.
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     * @param fee an optional ERC20 fee paid to the delegate of betaDelegatedTransfer by the from address.
     * @param seq a sequencing number included by the from address specific to this contract to protect from replays.
     * @param deadline a block number after which the pre-signed transaction has expired.
     * @return A boolean that indicates if the operation was successful.
     */
    function _betaDelegatedTransfer(
        bytes32 r, bytes32 s, uint8 v, address to, uint256 value, uint256 fee, uint256 seq, uint256 deadline
    ) internal whenNotPaused returns (bool) {
        require(betaDelegateWhitelist[msg.sender], "Beta feature only accepts whitelisted delegates");
        require(value > 0 || fee > 0, "cannot transfer zero tokens with zero fee");
        require(block.number <= deadline, "transaction expired");
        // prevent sig malleability from ecrecover()
        require(uint256(s) <= 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, "signature incorrect");
        require(v == 27 || v == 28, "signature incorrect");

        // EIP712 scheme: https://github.com/ethereum/EIPs/blob/master/EIPS/eip-712.md
        bytes32 delegatedTransferHash = keccak256(abi.encodePacked(// solium-disable-line
                EIP712_DELEGATED_TRANSFER_SCHEMA_HASH, bytes32(to), value, fee, seq, deadline
            ));
        bytes32 hash = keccak256(abi.encodePacked(EIP191_HEADER, EIP712_DOMAIN_HASH, delegatedTransferHash));
        address _from = ecrecover(hash, v, r, s);

        require(_from != address(0), "error determining from address from signature");
        require(to != address(0), "canno use address zero");
        require(!frozen[to] && !frozen[_from] && !frozen[msg.sender], "address frozen");
        require(value.add(fee) <= balances[_from], "insufficient fund");
        require(nextSeqs[_from] == seq, "incorrect seq");

        nextSeqs[_from] = nextSeqs[_from].add(1);
        balances[_from] = balances[_from].sub(value.add(fee));
        if (fee != 0) {
            balances[msg.sender] = balances[msg.sender].add(fee);
            emit Transfer(_from, msg.sender, fee);
        }
        balances[to] = balances[to].add(value);
        emit Transfer(_from, to, value);

        emit BetaDelegatedTransfer(_from, to, value, seq, fee);
        return true;
    }

    /**
     * @dev Performs an atomic batch of transfers on behalf of the from addresses, identified by their signatures.
     * Lack of nested array support in arguments requires all arguments to be passed as equal size arrays where
     * delegated transfer number i is the combination of all arguments at index i
     * @param r the r signatures of the delgatedTransfer msg.
     * @param s the s signatures of the delgatedTransfer msg.
     * @param v the v signatures of the delgatedTransfer msg.
     * @param to The addresses to transfer to.
     * @param value The amounts to be transferred.
     * @param fee optional ERC20 fees paid to the delegate of betaDelegatedTransfer by the from address.
     * @param seq sequencing numbers included by the from address specific to this contract to protect from replays.
     * @param deadline block numbers after which the pre-signed transactions have expired.
     * @return A boolean that indicates if the operation was successful.
     */
    function betaDelegatedTransferBatch(
        bytes32[] r, bytes32[] s, uint8[] v, address[] to, uint256[] value, uint256[] fee, uint256[] seq, uint256[] deadline
    ) public returns (bool) {
        require(r.length == s.length && r.length == v.length && r.length == to.length && r.length == value.length, "length mismatch");
        require(r.length == fee.length && r.length == seq.length && r.length == deadline.length, "length mismatch");

        for (uint i = 0; i < r.length; i++) {
            _betaDelegatedTransfer(r[i], s[i], v[i], to[i], value[i], fee[i], seq[i], deadline[i]);
        }
        return true;
    }

    /**
    * @dev Gets whether the address is currently whitelisted for betaDelegateTransfer.
    * @param _addr The address to check if whitelisted.
    * @return A bool representing whether the given address is whitelisted.
    */
    function isWhitelistedBetaDelegate(address _addr) public view returns (bool) {
        return betaDelegateWhitelist[_addr];
    }

    /**
     * @dev Sets a new betaDelegate whitelister.
     * @param _newWhitelister The address allowed to whitelist betaDelegates.
     */
    function setBetaDelegateWhitelister(address _newWhitelister) public {
        require(msg.sender == betaDelegateWhitelister || msg.sender == owner, "only Whitelister or Owner");
        require(betaDelegateWhitelister != _newWhitelister, "new address is same as a current one");
        betaDelegateWhitelister = _newWhitelister;
        emit BetaDelegateWhitelisterSet(betaDelegateWhitelister, _newWhitelister);
    }

    modifier onlyBetaDelegateWhitelister() {
        require(msg.sender == betaDelegateWhitelister, "onlyBetaDelegateWhitelister");
        _;
    }

    /**
     * @dev Whitelists an address to allow calling BetaDelegatedTransfer.
     * @param _addr The new address to whitelist.
     */
    function whitelistBetaDelegate(address _addr) public onlyBetaDelegateWhitelister {
        require(!betaDelegateWhitelist[_addr], "delegate already whitelisted");
        betaDelegateWhitelist[_addr] = true;
        emit BetaDelegateWhitelisted(_addr);
    }

    /**
     * @dev Unwhitelists an address to disallow calling BetaDelegatedTransfer.
     * @param _addr The new address to whitelist.
     */
    function unwhitelistBetaDelegate(address _addr) public onlyBetaDelegateWhitelister {
        require(betaDelegateWhitelist[_addr], "delegate not whitelisted");
        betaDelegateWhitelist[_addr] = false;
        emit BetaDelegateUnwhitelisted(_addr);
    }
}