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73 lines
2.5 KiB
Solidity

// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.7.0) (crosschain/polygon/CrossChainEnabledPolygonChild.sol)
pragma solidity ^0.8.4;
import "../CrossChainEnabled.sol";
import "../../security/ReentrancyGuard.sol";
import "../../utils/Address.sol";
import "../../vendor/polygon/IFxMessageProcessor.sol";
address constant DEFAULT_SENDER = 0x000000000000000000000000000000000000dEaD;
/**
* @dev https://polygon.technology/[Polygon] specialization or the
* {CrossChainEnabled} abstraction the child side (polygon/mumbai).
*
* This version should only be deployed on child chain to process cross-chain
* messages originating from the parent chain.
*
* The fxChild contract is provided and maintained by the polygon team. You can
* find the address of this contract polygon and mumbai in
* https://docs.polygon.technology/docs/develop/l1-l2-communication/fx-portal/#contract-addresses[Polygon's Fx-Portal documentation].
*
* _Available since v4.6._
*/
abstract contract CrossChainEnabledPolygonChild is IFxMessageProcessor, CrossChainEnabled, ReentrancyGuard {
/// @custom:oz-upgrades-unsafe-allow state-variable-immutable
address private immutable _fxChild;
address private _sender = DEFAULT_SENDER;
/// @custom:oz-upgrades-unsafe-allow constructor
constructor(address fxChild) {
_fxChild = fxChild;
}
/**
* @dev see {CrossChainEnabled-_isCrossChain}
*/
function _isCrossChain() internal view virtual override returns (bool) {
return msg.sender == _fxChild;
}
/**
* @dev see {CrossChainEnabled-_crossChainSender}
*/
function _crossChainSender() internal view virtual override onlyCrossChain returns (address) {
return _sender;
}
/**
* @dev External entry point to receive and relay messages originating
* from the fxChild.
*
* Non-reentrancy is crucial to avoid a cross-chain call being able
* to impersonate anyone by just looping through this with user-defined
* arguments.
*
* Note: if _fxChild calls any other function that does a delegate-call,
* then security could be compromised.
*/
function processMessageFromRoot(
uint256 /* stateId */,
address rootMessageSender,
bytes calldata data
) external override nonReentrant {
if (!_isCrossChain()) revert NotCrossChainCall();
_sender = rootMessageSender;
Address.functionDelegateCall(address(this), data, "cross-chain execution failed");
_sender = DEFAULT_SENDER;
}
}