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75 lines
2.8 KiB
Solidity
75 lines
2.8 KiB
Solidity
2 years ago
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// SPDX-License-Identifier: MIT
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// OpenZeppelin Contracts (last updated v4.8.0) (security/PullPayment.sol)
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pragma solidity ^0.8.0;
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import "../utils/escrow/Escrow.sol";
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/**
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* @dev Simple implementation of a
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* https://consensys.github.io/smart-contract-best-practices/development-recommendations/general/external-calls/#favor-pull-over-push-for-external-calls[pull-payment]
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* strategy, where the paying contract doesn't interact directly with the
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* receiver account, which must withdraw its payments itself.
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*
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* Pull-payments are often considered the best practice when it comes to sending
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* Ether, security-wise. It prevents recipients from blocking execution, and
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* eliminates reentrancy concerns.
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*
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* TIP: If you would like to learn more about reentrancy and alternative ways
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* to protect against it, check out our blog post
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* https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
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*
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* To use, derive from the `PullPayment` contract, and use {_asyncTransfer}
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* instead of Solidity's `transfer` function. Payees can query their due
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* payments with {payments}, and retrieve them with {withdrawPayments}.
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*/
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abstract contract PullPayment {
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Escrow private immutable _escrow;
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constructor() {
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_escrow = new Escrow();
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}
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/**
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* @dev Withdraw accumulated payments, forwarding all gas to the recipient.
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*
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* Note that _any_ account can call this function, not just the `payee`.
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* This means that contracts unaware of the `PullPayment` protocol can still
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* receive funds this way, by having a separate account call
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* {withdrawPayments}.
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*
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* WARNING: Forwarding all gas opens the door to reentrancy vulnerabilities.
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* Make sure you trust the recipient, or are either following the
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* checks-effects-interactions pattern or using {ReentrancyGuard}.
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*
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* @param payee Whose payments will be withdrawn.
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*
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* Causes the `escrow` to emit a {Withdrawn} event.
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*/
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function withdrawPayments(address payable payee) public virtual {
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_escrow.withdraw(payee);
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}
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/**
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* @dev Returns the payments owed to an address.
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* @param dest The creditor's address.
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*/
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function payments(address dest) public view returns (uint256) {
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return _escrow.depositsOf(dest);
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}
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/**
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* @dev Called by the payer to store the sent amount as credit to be pulled.
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* Funds sent in this way are stored in an intermediate {Escrow} contract, so
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* there is no danger of them being spent before withdrawal.
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*
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* @param dest The destination address of the funds.
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* @param amount The amount to transfer.
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*
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* Causes the `escrow` to emit a {Deposited} event.
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*/
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function _asyncTransfer(address dest, uint256 amount) internal virtual {
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_escrow.deposit{value: amount}(dest);
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}
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}
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