Cryo Explorer Ethereum Mainnet

// SPDX-License-Identifier: Apache-2.0
pragma solidity ^0.8.3;

interface IERC20 {
    function symbol() external view returns (string memory);

    function balanceOf(address account) external view returns (uint256);

    // Note this is non standard but nearly all ERC20 have exposed decimal functions
    function decimals() external view returns (uint8);

    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

// SPDX-License-Identifier: Apache-2.0
// Copied from https://github.com/element-fi/elf-contracts/blob/a6cb960896301b7562ced70a8b221f3cc964ea0a/contracts/libraries/ERC20Permit.sol

pragma solidity ^0.8.3;

import "../interfaces/IERC20Permit.sol";

// This default erc20 library is designed for max efficiency and security.
// WARNING: By default it does not include totalSupply which breaks the ERC20 standard
//          to use a fully standard compliant ERC20 use 'ERC20PermitWithSupply"
abstract contract ERC20Permit is IERC20Permit {
    // --- ERC20 Data ---
    // The name of the erc20 token
    string public name;
    // The symbol of the erc20 token
    string public override symbol;
    // The decimals of the erc20 token, should default to 18 for new tokens
    uint8 public override decimals;

    // A mapping which tracks user token balances
    mapping(address => uint256) public override balanceOf;
    // A mapping which tracks which addresses a user allows to move their tokens
    mapping(address => mapping(address => uint256)) public override allowance;
    // A mapping which tracks the permit signature nonces for users
    mapping(address => uint256) public override nonces;

    // --- EIP712 niceties ---
    // solhint-disable-next-line var-name-mixedcase
    bytes32 public override DOMAIN_SEPARATOR;
    // bytes32 public constant PERMIT_TYPEHASH = keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
    bytes32 public constant PERMIT_TYPEHASH =
        0x6e71edae12b1b97f4d1f60370fef10105fa2faae0126114a169c64845d6126c9;

    /// @notice Initializes the erc20 contract
    /// @param name_ the value 'name' will be set to
    /// @param symbol_ the value 'symbol' will be set to
    /// @dev decimals default to 18 and must be reset by an inheriting contract for
    ///      non standard decimal values
    constructor(string memory name_, string memory symbol_) {
        // Set the state variables
        name = name_;
        symbol = symbol_;
        decimals = 18;

        // By setting these addresses to 0 attempting to execute a transfer to
        // either of them will revert. This is a gas efficient way to prevent
        // a common user mistake where they transfer to the token address.
        // These values are not considered 'real' tokens and so are not included
        // in 'total supply' which only contains minted tokens.
        balanceOf[address(0)] = type(uint256).max;
        balanceOf[address(this)] = type(uint256).max;

        // Optional extra state manipulation
        _extraConstruction();

        // Computes the EIP 712 domain separator which prevents user signed messages for
        // this contract to be replayed in other contracts.
        // https://eips.ethereum.org/EIPS/eip-712
        DOMAIN_SEPARATOR = keccak256(
            abi.encode(
                keccak256(
                    "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
                ),
                keccak256(bytes(name)),
                keccak256(bytes("1")),
                block.chainid,
                address(this)
            )
        );
    }

    /// @notice An optional override function to execute and change state before immutable assignment
    function _extraConstruction() internal virtual {}

    // --- Token ---
    /// @notice Allows a token owner to send tokens to another address
    /// @param recipient The address which will be credited with the tokens
    /// @param amount The amount user token to send
    /// @return returns true on success, reverts on failure so cannot return false.
    /// @dev transfers to this contract address or 0 will fail
    function transfer(address recipient, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        // We forward this call to 'transferFrom'
        return transferFrom(msg.sender, recipient, amount);
    }

    /// @notice Transfers an amount of erc20 from a spender to a receipt
    /// @param spender The source of the ERC20 tokens
    /// @param recipient The destination of the ERC20 tokens
    /// @param amount the number of tokens to send
    /// @return returns true on success and reverts on failure
    /// @dev will fail transfers which send funds to this contract or 0
    function transferFrom(
        address spender,
        address recipient,
        uint256 amount
    ) public virtual override returns (bool) {
        // Load balance and allowance
        uint256 balance = balanceOf[spender];
        require(balance >= amount, "ERC20: insufficient-balance");
        // We potentially have to change allowances
        if (spender != msg.sender) {
            // Loading the allowance in the if block prevents vanilla transfers
            // from paying for the sload.
            uint256 allowed = allowance[spender][msg.sender];
            // If the allowance is max we do not reduce it
            // Note - This means that max allowances will be more gas efficient
            // by not requiring a sstore on 'transferFrom'
            if (allowed != type(uint256).max) {
                require(allowed >= amount, "ERC20: insufficient-allowance");
                allowance[spender][msg.sender] = allowed - amount;
            }
        }
        // Update the balances
        balanceOf[spender] = balance - amount;
        // Note - In the constructor we initialize the 'balanceOf' of address 0 and
        //        the token address to uint256.max and so in 8.0 transfers to those
        //        addresses revert on this step.
        balanceOf[recipient] = balanceOf[recipient] + amount;
        // Emit the needed event
        emit Transfer(spender, recipient, amount);
        // Return that this call succeeded
        return true;
    }

    /// @notice This internal minting function allows inheriting contracts
    ///         to mint tokens in the way they wish.
    /// @param account the address which will receive the token.
    /// @param amount the amount of token which they will receive
    /// @dev This function is virtual so that it can be overridden, if you
    ///      are reviewing this contract for security you should ensure to
    ///      check for overrides
    function _mint(address account, uint256 amount) internal virtual {
        // Add tokens to the account
        balanceOf[account] = balanceOf[account] + amount;
        // Emit an event to track the minting
        emit Transfer(address(0), account, amount);
    }

    /// @notice This internal burning function allows inheriting contracts to
    ///         burn tokens in the way they see fit.
    /// @param account the account to remove tokens from
    /// @param amount  the amount of tokens to remove
    /// @dev This function is virtual so that it can be overridden, if you
    ///      are reviewing this contract for security you should ensure to
    ///      check for overrides
    function _burn(address account, uint256 amount) internal virtual {
        // Reduce the balance of the account
        balanceOf[account] = balanceOf[account] - amount;
        // Emit an event tracking transfers
        emit Transfer(account, address(0), amount);
    }

    /// @notice This function allows a user to approve an account which can transfer
    ///         tokens on their behalf.
    /// @param account The account which will be approve to transfer tokens
    /// @param amount The approval amount, if set to uint256.max the allowance does not go down on transfers.
    /// @return returns true for compatibility with the ERC20 standard
    function approve(address account, uint256 amount)
        public
        virtual
        override
        returns (bool)
    {
        // Set the senders allowance for account to amount
        allowance[msg.sender][account] = amount;
        // Emit an event to track approvals
        emit Approval(msg.sender, account, amount);
        return true;
    }

    /// @notice This function allows a caller who is not the owner of an account to execute the functionality of 'approve' with the owners signature.
    /// @param owner the owner of the account which is having the new approval set
    /// @param spender the address which will be allowed to spend owner's tokens
    /// @param value the new allowance value
    /// @param deadline the timestamp which the signature must be submitted by to be valid
    /// @param v Extra ECDSA data which allows public key recovery from signature assumed to be 27 or 28
    /// @param r The r component of the ECDSA signature
    /// @param s The s component of the ECDSA signature
    /// @dev The signature for this function follows EIP 712 standard and should be generated with the
    ///      eth_signTypedData JSON RPC call instead of the eth_sign JSON RPC call. If using out of date
    ///      parity signing libraries the v component may need to be adjusted. Also it is very rare but possible
    ///      for v to be other values, those values are not supported.
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external override {
        // The EIP 712 digest for this function
        bytes32 digest =
            keccak256(
                abi.encodePacked(
                    "\x19\x01",
                    DOMAIN_SEPARATOR,
                    keccak256(
                        abi.encode(
                            PERMIT_TYPEHASH,
                            owner,
                            spender,
                            value,
                            nonces[owner],
                            deadline
                        )
                    )
                )
            );
        // Require that the owner is not zero
        require(owner != address(0), "ERC20: invalid-address-0");
        // Require that we have a valid signature from the owner
        require(owner == ecrecover(digest, v, r, s), "ERC20: invalid-permit");
        // Require that the signature is not expired
        require(
            deadline == 0 || block.timestamp <= deadline,
            "ERC20: permit-expired"
        );
        // Format the signature to the default format
        require(
            uint256(s) <=
                0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0,
            "ERC20: invalid signature 's' value"
        );
        // Increment the signature nonce to prevent replay
        nonces[owner]++;
        // Set the allowance to the new value
        allowance[owner][spender] = value;
        // Emit an approval event to be able to track this happening
        emit Approval(owner, spender, value);
    }

    /// @notice Internal function which allows inheriting contract to set custom decimals
    /// @param decimals_ the new decimal value
    function _setupDecimals(uint8 decimals_) internal {
        // Set the decimals
        decimals = decimals_;
    }
}

// SPDX-License-Identifier: Apache-2.0
pragma solidity >=0.7.0;

contract Authorizable {
    // This contract allows a flexible authorization scheme

    // The owner who can change authorization status
    address public owner;
    // A mapping from an address to its authorization status
    mapping(address => bool) public authorized;

    /// @dev We set the deployer to the owner
    constructor() {
        owner = msg.sender;
    }

    /// @dev This modifier checks if the msg.sender is the owner
    modifier onlyOwner() {
        require(msg.sender == owner, "Sender not owner");
        _;
    }

    /// @dev This modifier checks if an address is authorized
    modifier onlyAuthorized() {
        require(isAuthorized(msg.sender), "Sender not Authorized");
        _;
    }

    /// @dev Returns true if an address is authorized
    /// @param who the address to check
    /// @return true if authorized false if not
    function isAuthorized(address who) public view returns (bool) {
        return authorized[who];
    }

    /// @dev Privileged function authorize an address
    /// @param who the address to authorize
    function authorize(address who) external onlyOwner() {
        _authorize(who);
    }

    /// @dev Privileged function to de authorize an address
    /// @param who The address to remove authorization from
    function deauthorize(address who) external onlyOwner() {
        authorized[who] = false;
    }

    /// @dev Function to change owner
    /// @param who The new owner address
    function setOwner(address who) public onlyOwner() {
        owner = who;
    }

    /// @dev Inheritable function which authorizes someone
    /// @param who the address to authorize
    function _authorize(address who) internal {
        authorized[who] = true;
    }
}

// Forked from openzepplin
// SPDX-License-Identifier: MIT

pragma solidity ^0.8.3;

import "./IERC20.sol";

/**
 * @dev Interface of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
 * https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
 *
 * Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
 * presenting a message signed by the account. By not relying on `{IERC20-approve}`, the token holder account doesn't
 * need to send a transaction, and thus is not required to hold Ether at all.
 */
interface IERC20Permit is IERC20 {
    /**
     * @dev Sets `value` as the allowance of `spender` over `owner`'s tokens,
     * given `owner`'s signed approval.
     *
     * IMPORTANT: The same issues {IERC20-approve} has related to transaction
     * ordering also apply here.
     *
     * Emits an {Approval} event.
     *
     * Requirements:
     *
     * - `spender` cannot be the zero address.
     * - `deadline` must be a timestamp in the future.
     * - `v`, `r` and `s` must be a valid `secp256k1` signature from `owner`
     * over the EIP712-formatted function arguments.
     * - the signature must use ``owner``'s current nonce (see {nonces}).
     *
     * For more information on the signature format, see the
     * https://eips.ethereum.org/EIPS/eip-2612#specification[relevant EIP
     * section].
     */
    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) external;

    /**
     * @dev Returns the current nonce for `owner`. This value must be
     * included whenever a signature is generated for {permit}.
     *
     * Every successful call to {permit} increases ``owner``'s nonce by one. This
     * prevents a signature from being used multiple times.
     */
    function nonces(address owner) external view returns (uint256);

    /**
     * @dev Returns the domain separator used in the encoding of the signature for `permit`, as defined by {EIP712}.
     */
    // solhint-disable-next-line func-name-mixedcase
    function DOMAIN_SEPARATOR() external view returns (bytes32);
}

// SPDX-License-Identifier: Apache-2.0
// Largely based on https://github.com/element-fi/elf-contracts/blob/a6cb960896301b7562ced70a8b221f3cc964ea0a/contracts/libraries/ERC20PermitWithSupply.sol

pragma solidity ^0.8.3;

import "./ERC20Permit.sol";
import "./Authorizable.sol";

// This contract adds total supply and minting to the generic erc20
contract ERC20PermitWithMint is ERC20Permit, Authorizable {
    /// @notice Initializes the erc20 contract
    /// @param name_ the value 'name' will be set to
    /// @param symbol_ the value 'symbol' will be set to
    /// @param owner_ address which has the power to mint
    constructor(
        string memory name_,
        string memory symbol_,
        address owner_
    ) ERC20Permit(name_, symbol_) {
        setOwner(owner_);
    }

    // The stored totalSupply, it equals all tokens minted - all tokens burned
    uint256 public totalSupply;

    /// @notice Allows the governance to mint
    /// @param account the account to addd tokens to
    /// @param amount the amount of tokens to add
    function mint(address account, uint256 amount) external onlyOwner {
        _mint(account, amount);
    }

    /// @notice This function overrides the ERC20Permit Library's _mint and causes it
    ///          to track total supply.
    /// @param account the account to addd tokens to
    /// @param amount the amount of tokens to add
    function _mint(address account, uint256 amount) internal override {
        // Increase account balance
        balanceOf[account] = balanceOf[account] + amount;
        // Increase total supply
        totalSupply += amount;
        // Emit a transfer from zero to emulate a mint
        emit Transfer(address(0), account, amount);
    }

    /// @notice Allows the governance to burn
    /// @param account the account to burn from
    /// @param amount the amount of token to burn
    function burn(address account, uint256 amount) external onlyOwner {
        _burn(account, amount);
    }

    /// @notice This function overrides the ERC20Permit Library's _burn to decrement total supply
    /// @param account the account to burn from
    /// @param amount the amount of token to burn
    function _burn(address account, uint256 amount) internal override {
        // Decrease user balance
        uint256 currentBalance = balanceOf[account];
        // This logic prevents a reversion if the _burn is frontrun
        if (currentBalance < amount) {
            balanceOf[account] = 0;
        } else {
            balanceOf[account] = currentBalance - amount;
        }
        // Decrease total supply
        totalSupply -= amount;
        // Emit an event tracking the burn
        emit Transfer(account, address(0), amount);
    }
}