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96 lines
3.2 KiB
Solidity
96 lines
3.2 KiB
Solidity
// SPDX-License-Identifier: MIT
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// OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/extensions/ERC20Permit.sol)
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pragma solidity ^0.8.0;
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import "./IERC20Permit.sol";
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import "../ERC20.sol";
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import "../../../utils/cryptography/ECDSA.sol";
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import "../../../utils/cryptography/EIP712.sol";
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import "../../../utils/Counters.sol";
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/**
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* @dev Implementation of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
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* https://eips.ethereum.org/EIPS/eip-2612[EIP-2612].
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*
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* Adds the {permit} method, which can be used to change an account's ERC20 allowance (see {IERC20-allowance}) by
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* presenting a message signed by the account. By not relying on `{IERC20-approve}`, the token holder account doesn't
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* need to send a transaction, and thus is not required to hold Ether at all.
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*
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* _Available since v3.4._
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*/
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abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
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using Counters for Counters.Counter;
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mapping(address => Counters.Counter) private _nonces;
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// solhint-disable-next-line var-name-mixedcase
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bytes32 private constant _PERMIT_TYPEHASH =
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keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
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/**
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* @dev In previous versions `_PERMIT_TYPEHASH` was declared as `immutable`.
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* However, to ensure consistency with the upgradeable transpiler, we will continue
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* to reserve a slot.
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* @custom:oz-renamed-from _PERMIT_TYPEHASH
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*/
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// solhint-disable-next-line var-name-mixedcase
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bytes32 private _PERMIT_TYPEHASH_DEPRECATED_SLOT;
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/**
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* @dev Initializes the {EIP712} domain separator using the `name` parameter, and setting `version` to `"1"`.
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*
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* It's a good idea to use the same `name` that is defined as the ERC20 token name.
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*/
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constructor(string memory name) EIP712(name, "1") {}
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/**
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* @dev See {IERC20Permit-permit}.
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*/
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function permit(
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address owner,
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address spender,
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uint256 value,
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uint256 deadline,
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uint8 v,
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bytes32 r,
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bytes32 s
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) public virtual override {
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require(block.timestamp <= deadline, "ERC20Permit: expired deadline");
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bytes32 structHash = keccak256(abi.encode(_PERMIT_TYPEHASH, owner, spender, value, _useNonce(owner), deadline));
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bytes32 hash = _hashTypedDataV4(structHash);
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address signer = ECDSA.recover(hash, v, r, s);
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require(signer == owner, "ERC20Permit: invalid signature");
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_approve(owner, spender, value);
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}
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/**
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* @dev See {IERC20Permit-nonces}.
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*/
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function nonces(address owner) public view virtual override returns (uint256) {
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return _nonces[owner].current();
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}
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/**
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* @dev See {IERC20Permit-DOMAIN_SEPARATOR}.
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*/
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// solhint-disable-next-line func-name-mixedcase
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function DOMAIN_SEPARATOR() external view override returns (bytes32) {
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return _domainSeparatorV4();
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}
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/**
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* @dev "Consume a nonce": return the current value and increment.
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*
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* _Available since v4.1._
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*/
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function _useNonce(address owner) internal virtual returns (uint256 current) {
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Counters.Counter storage nonce = _nonces[owner];
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current = nonce.current();
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nonce.increment();
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}
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}
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