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Merge pull request #87 from OffchainLabs/bridged-usdc-gw
Bridged usdc custom gateway
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contracts/tokenbridge/arbitrum/gateway/L2USDCGateway.sol
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| // SPDX-License-Identifier: Apache-2.0 | ||
| pragma solidity ^0.8.4; | ||
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| import "./L2ArbitrumGateway.sol"; | ||
| import {IFiatToken, IFiatTokenProxy} from "../../ethereum/gateway/L1USDCGateway.sol"; | ||
| import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol"; | ||
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| /** | ||
| * @title Child chain custom gateway for USDC implementing Bridged USDC Standard. | ||
| * @notice Reference to the Circle's Bridged USDC Standard: | ||
| * https://github.com/circlefin/stablecoin-evm/blob/master/doc/bridged_USDC_standard.md | ||
| * | ||
| * @dev This contract can be used on new Orbit chains which want to provide USDC | ||
| * bridging solution and keep the possibility to upgrade to native USDC at | ||
| * some point later. This solution will NOT be used in existing Arbitrum chains. | ||
| * | ||
| * Parent chain custom gateway to be used along this child chain custom gateway is | ||
| * L1USDCGateway (when eth is used to pay fees) or L1OrbitUSDCGateway (when custom fee token is used). | ||
| * This custom gateway differs from standard gateway in the following ways: | ||
| * - it supports a single parent chain - child chain USDC token pair | ||
| * - it is ownable | ||
| * - withdrawals can be paused by the owner | ||
| * - owner can set an "transferrer" account which will be able to transfer USDC ownership | ||
| * - transferrer can transfer USDC owner and proxyAdmin | ||
| * | ||
| * NOTE: before withdrawing funds, make sure that recipient address is not blacklisted on the parent chain. | ||
| * Also, make sure that USDC token itself is not paused. Otherwise funds might get stuck. | ||
| */ | ||
| contract L2USDCGateway is L2ArbitrumGateway { | ||
| using SafeERC20 for IERC20; | ||
| using Address for address; | ||
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| address public l1USDC; | ||
| address public l2USDC; | ||
| address public owner; | ||
| address public usdcOwnershipTransferrer; | ||
| bool public withdrawalsPaused; | ||
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| event WithdrawalsPaused(); | ||
| event WithdrawalsUnpaused(); | ||
| event OwnerSet(address indexed owner); | ||
| event USDCOwnershipTransferrerSet(address indexed usdcOwnershipTransferrer); | ||
| event USDCOwnershipTransferred(address indexed newOwner, address indexed newProxyAdmin); | ||
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| error L2USDCGateway_WithdrawalsAlreadyPaused(); | ||
| error L2USDCGateway_WithdrawalsAlreadyUnpaused(); | ||
| error L2USDCGateway_WithdrawalsPaused(); | ||
| error L2USDCGateway_InvalidL1USDC(); | ||
| error L2USDCGateway_InvalidL2USDC(); | ||
| error L2USDCGateway_NotOwner(); | ||
| error L2USDCGateway_InvalidOwner(); | ||
| error L2USDCGateway_NotUSDCOwnershipTransferrer(); | ||
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| modifier onlyOwner() { | ||
| if (msg.sender != owner) { | ||
| revert L2USDCGateway_NotOwner(); | ||
| } | ||
| _; | ||
| } | ||
|
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| function initialize( | ||
| address _l1Counterpart, | ||
| address _router, | ||
| address _l1USDC, | ||
| address _l2USDC, | ||
| address _owner | ||
| ) public { | ||
| if (_l1USDC == address(0)) { | ||
| revert L2USDCGateway_InvalidL1USDC(); | ||
| } | ||
| if (_l2USDC == address(0)) { | ||
| revert L2USDCGateway_InvalidL2USDC(); | ||
| } | ||
| if (_owner == address(0)) { | ||
| revert L2USDCGateway_InvalidOwner(); | ||
| } | ||
| L2ArbitrumGateway._initialize(_l1Counterpart, _router); | ||
| l1USDC = _l1USDC; | ||
| l2USDC = _l2USDC; | ||
| owner = _owner; | ||
| } | ||
|
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| /** | ||
| * @notice Pause all withdrawals. This can only be called by the owner. | ||
| */ | ||
| function pauseWithdrawals() external onlyOwner { | ||
| if (withdrawalsPaused) { | ||
| revert L2USDCGateway_WithdrawalsAlreadyPaused(); | ||
| } | ||
| withdrawalsPaused = true; | ||
| emit WithdrawalsPaused(); | ||
| } | ||
|
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| /** | ||
| * @notice Unpause withdrawals. This can only be called by the owner. | ||
| */ | ||
| function unpauseWithdrawals() external onlyOwner { | ||
| if (!withdrawalsPaused) { | ||
| revert L2USDCGateway_WithdrawalsAlreadyUnpaused(); | ||
| } | ||
| withdrawalsPaused = false; | ||
| emit WithdrawalsUnpaused(); | ||
| } | ||
|
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| /** | ||
| * @notice Sets a new owner. | ||
| */ | ||
| function setOwner(address newOwner) external onlyOwner { | ||
| if (newOwner == address(0)) { | ||
| revert L2USDCGateway_InvalidOwner(); | ||
| } | ||
| owner = newOwner; | ||
| emit OwnerSet(newOwner); | ||
| } | ||
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| /** | ||
| * @notice Sets the account which is able to transfer USDC role away from the gateway to some other account. | ||
| */ | ||
| function setUsdcOwnershipTransferrer(address _usdcOwnershipTransferrer) external onlyOwner { | ||
| usdcOwnershipTransferrer = _usdcOwnershipTransferrer; | ||
| emit USDCOwnershipTransferrerSet(_usdcOwnershipTransferrer); | ||
| } | ||
|
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| /** | ||
| * @notice In accordance with bridged USDC standard, the ownership of the USDC token contract is transferred | ||
| * to the new owner, and the proxy admin is transferred to the caller (usdcOwnershipTransferrer). | ||
| * @dev For transfer to be successful, this gateway should be both the owner and the proxy admin of L2 USDC token. | ||
| */ | ||
| function transferUSDCRoles(address _owner) external { | ||
| if (msg.sender != usdcOwnershipTransferrer) { | ||
| revert L2USDCGateway_NotUSDCOwnershipTransferrer(); | ||
| } | ||
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| IFiatTokenProxy(l2USDC).changeAdmin(msg.sender); | ||
| IFiatToken(l2USDC).transferOwnership(_owner); | ||
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| emit USDCOwnershipTransferred(_owner, msg.sender); | ||
| } | ||
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| /** | ||
| * @notice Entrypoint for withdrawing USDC, can be used only if withdrawals are not paused. | ||
| */ | ||
| function outboundTransfer( | ||
| address _l1Token, | ||
| address _to, | ||
| uint256 _amount, | ||
| uint256, /* _maxGas */ | ||
| uint256, /* _gasPriceBid */ | ||
| bytes calldata _data | ||
| ) public payable override returns (bytes memory res) { | ||
| if (withdrawalsPaused) { | ||
| revert L2USDCGateway_WithdrawalsPaused(); | ||
| } | ||
| return super.outboundTransfer(_l1Token, _to, _amount, 0, 0, _data); | ||
| } | ||
|
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| /** | ||
| * @notice Only parent chain - child chain USDC token pair is supported | ||
| */ | ||
| function calculateL2TokenAddress(address l1ERC20) public view override returns (address) { | ||
| if (l1ERC20 != l1USDC) { | ||
| // invalid L1 usdc address | ||
| return address(0); | ||
| } | ||
| return l2USDC; | ||
| } | ||
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| function inboundEscrowTransfer(address _l2Address, address _dest, uint256 _amount) | ||
| internal | ||
| override | ||
| { | ||
| IFiatToken(_l2Address).mint(_dest, _amount); | ||
| } | ||
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| function outboundEscrowTransfer(address _l2Token, address _from, uint256 _amount) | ||
| internal | ||
| override | ||
| returns (uint256) | ||
| { | ||
| // fetch the USDC tokens from the user and then burn them | ||
| IERC20(_l2Token).safeTransferFrom(_from, address(this), _amount); | ||
| IFiatToken(_l2Token).burn(_amount); | ||
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| return _amount; | ||
| } | ||
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| /** | ||
| * @notice Withdraw back the USDC if child chain side is not set up properly | ||
| */ | ||
| function handleNoContract( | ||
| address l1ERC20, | ||
| address, /* expectedL2Address */ | ||
| address _from, | ||
| address, /* _to */ | ||
| uint256 _amount, | ||
| bytes memory /* deployData */ | ||
| ) internal override returns (bool shouldHalt) { | ||
| // it is assumed that the custom token is deployed to child chain before deposits are made | ||
| triggerWithdrawal(l1ERC20, address(this), _from, _amount, ""); | ||
| return true; | ||
| } | ||
|
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| /** | ||
| * @notice We need to override this function because base implementation assumes that L2 token implements | ||
| * `l1Address()` function from IArbToken interface. In the case of USDC gateway IArbToken logic is | ||
| * part of this contract, so we just check that addresses match the expected L1 and L2 USDC address. | ||
| */ | ||
| function _isValidTokenAddress(address _l1Address, address _expectedL2Address) | ||
| internal | ||
| view | ||
| override | ||
| returns (bool) | ||
| { | ||
| return _l1Address == l1USDC && _expectedL2Address == l2USDC; | ||
| } | ||
| } |
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