Lido withdraw strategy (#2080)

* Added LidoWithdrawalStrategy

* Added deployment of Lido withdrawal strategy

* Completed Lido Withdrawal Strategy fork tests

* Updated Natspec

* Renamed fraxEth to stEth in LidoWithdrawalStrategy

* Moved _abstractSetPToken to bottom of the LidoWithdrawalStrategy
made _abstractSetPToken pure

* renamed numWithdrawals to withdrawalLength

* outstandingWithdrawals now accounts for stETH dust left behind

* don't format Defender Action code in dist folder

Author: naddison36

contracts/contracts/proxies/Proxies.sol

@@ -227,3 +227,10 @@ contract NativeStakingFeeAccumulatorProxy is
 {
 
 }
+
+/**
+ * @notice LidoWithdrawalStrategyProxy delegates calls to a LidoWithdrawalStrategy implementation
+ */
+contract LidoWithdrawalStrategyProxy is InitializeGovernedUpgradeabilityProxy {
+
+}

contracts/contracts/strategies/LidoWithdrawalStrategy.sol

@@ -0,0 +1,314 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import { IERC20, InitializableAbstractStrategy } from "../utils/InitializableAbstractStrategy.sol";
+import { IWETH9 } from "../interfaces/IWETH9.sol";
+import { IVault } from "../interfaces/IVault.sol";
+
+interface IStETHWithdrawal {
+    event WithdrawalRequested(
+        uint256 indexed requestId,
+        address indexed requestor,
+        address indexed owner,
+        uint256 amountOfStETH,
+        uint256 amountOfShares
+    );
+    event WithdrawalsFinalized(
+        uint256 indexed from,
+        uint256 indexed to,
+        uint256 amountOfETHLocked,
+        uint256 sharesToBurn,
+        uint256 timestamp
+    );
+    event WithdrawalClaimed(
+        uint256 indexed requestId,
+        address indexed owner,
+        address indexed receiver,
+        uint256 amountOfETH
+    );
+
+    struct WithdrawalRequestStatus {
+        /// @notice stETH token amount that was locked on withdrawal queue for this request
+        uint256 amountOfStETH;
+        /// @notice amount of stETH shares locked on withdrawal queue for this request
+        uint256 amountOfShares;
+        /// @notice address that can claim or transfer this request
+        address owner;
+        /// @notice timestamp of when the request was created, in seconds
+        uint256 timestamp;
+        /// @notice true, if request is finalized
+        bool isFinalized;
+        /// @notice true, if request is claimed. Request is claimable if (isFinalized && !isClaimed)
+        bool isClaimed;
+    }
+
+    function requestWithdrawals(uint256[] calldata _amounts, address _owner)
+        external
+        returns (uint256[] memory requestIds);
+
+    function getLastCheckpointIndex() external view returns (uint256);
+
+    function findCheckpointHints(
+        uint256[] calldata _requestIds,
+        uint256 _firstIndex,
+        uint256 _lastIndex
+    ) external view returns (uint256[] memory hintIds);
+
+    function claimWithdrawals(
+        uint256[] calldata _requestIds,
+        uint256[] calldata _hints
+    ) external;
+
+    function getWithdrawalStatus(uint256[] calldata _requestIds)
+        external
+        view
+        returns (WithdrawalRequestStatus[] memory statuses);
+
+    function getWithdrawalRequests(address _owner)
+        external
+        view
+        returns (uint256[] memory requestsIds);
+
+    function finalize(
+        uint256 _lastRequestIdToBeFinalized,
+        uint256 _maxShareRate
+    ) external payable;
+}
+
+/**
+ * @title Lido Withdrawal Strategy
+ * @notice This strategy withdraws ETH from stETH via the Lido Withdrawal Queue contract
+ * @author Origin Protocol Inc
+ */
+contract LidoWithdrawalStrategy is InitializableAbstractStrategy {
+    /// @notice Address of the WETH token
+    IWETH9 private constant weth =
+        IWETH9(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
+    /// @notice Address of the stETH token
+    IERC20 private constant stETH =
+        IERC20(0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84);
+    /// @notice Address of the Lido Withdrawal Queue contract
+    IStETHWithdrawal private constant withdrawalQueue =
+        IStETHWithdrawal(0x889edC2eDab5f40e902b864aD4d7AdE8E412F9B1);
+    /// @notice Maximum amount of stETH that can be withdrawn in a single request
+    uint256 public constant MaxWithdrawalAmount = 1000 ether;
+    /// @notice Total amount of stETH that has been requested to be withdrawn for ETH
+    uint256 public outstandingWithdrawals;
+
+    event WithdrawalRequests(uint256[] requestIds, uint256[] amounts);
+    event WithdrawalClaims(uint256[] requestIds, uint256 amount);
+
+    constructor(BaseStrategyConfig memory _stratConfig)
+        InitializableAbstractStrategy(_stratConfig)
+    {
+        require(MaxWithdrawalAmount < type(uint120).max);
+    }
+
+    /**
+     * @notice initialize function, to set up initial internal state
+     * @param _rewardTokenAddresses Address of reward token for platform
+     * @param _assets Addresses of initial supported assets
+     * @param _pTokens Platform Token corresponding addresses
+     */
+    function initialize(
+        address[] memory _rewardTokenAddresses,
+        address[] memory _assets,
+        address[] memory _pTokens
+    ) external onlyGovernor initializer {
+        InitializableAbstractStrategy._initialize(
+            _rewardTokenAddresses,
+            _assets,
+            _pTokens
+        );
+        safeApproveAllTokens();
+    }
+
+    /**
+     * @notice deposit() function not used for this strategy. Use depositAll() instead.
+     */
+    function deposit(address, uint256) public override onlyVault nonReentrant {
+        // This method no longer used by the VaultAdmin, and we don't want it
+        // to be used by VaultCore.
+        require(false, "use depositAll() instead");
+    }
+
+    /**
+     * @notice Takes all given stETH and creates Lido withdrawal request
+     */
+    function depositAll() external override onlyVault nonReentrant {
+        uint256 stETHStart = stETH.balanceOf(address(this));
+        require(stETHStart > 0, "No stETH to withdraw");
+
+        uint256 withdrawalLength = (stETHStart / MaxWithdrawalAmount) + 1;
+        uint256[] memory amounts = new uint256[](withdrawalLength);
+
+        uint256 stETHRemaining = stETHStart;
+        uint256 i = 0;
+        while (stETHRemaining > MaxWithdrawalAmount) {
+            amounts[i++] = MaxWithdrawalAmount;
+            stETHRemaining -= MaxWithdrawalAmount;
+        }
+        amounts[i] = stETHRemaining;
+
+        uint256[] memory requestIds = withdrawalQueue.requestWithdrawals(
+            amounts,
+            address(this)
+        );
+
+        emit WithdrawalRequests(requestIds, amounts);
+
+        // Is there any stETH left except 1 wei from each request?
+        // This is because stETH does not transfer all the transfer amount.
+        uint256 stEthDust = stETH.balanceOf(address(this));
+        require(
+            stEthDust <= withdrawalLength,
+            "Not all stEth in withdraw queue"
+        );
+        outstandingWithdrawals += stETHStart - stEthDust;
+
+        // This strategy claims to support WETH, so it is possible for
+        // the vault to transfer WETH to it. This returns any deposited WETH
+        // to the vault so that it is not lost for balance tracking purposes.
+        uint256 wethBalance = weth.balanceOf(address(this));
+        if (wethBalance > 0) {
+            // slither-disable-next-line unchecked-transfer
+            weth.transfer(vaultAddress, wethBalance);
+        }
+
+        emit Deposit(address(stETH), address(withdrawalQueue), stETHStart);
+    }
+
+    /**
+     * @notice Withdraw an asset from the underlying platform
+     * @param _recipient Address to receive withdrawn assets
+     * @param _asset Address of the asset to withdraw
+     * @param _amount Amount of assets to withdraw
+     */
+    function withdraw(
+        // solhint-disable-next-line no-unused-vars
+        address _recipient,
+        // solhint-disable-next-line no-unused-vars
+        address _asset,
+        // solhint-disable-next-line no-unused-vars
+        uint256 _amount
+    ) external override onlyVault nonReentrant {
+        // Does nothing - all withdrawals need to be called manually using the
+        // Strategist calling claimWithdrawals
+        revert("use claimWithdrawals()");
+    }
+
+    /**
+     * @notice Claim previously requested withdrawals that have now finalized.
+     * Called by the Strategist.
+     * @param _requestIds Array of withdrawal request identifiers
+     * @param expectedAmount Total amount of ETH expect to be withdrawn
+     */
+    function claimWithdrawals(
+        uint256[] memory _requestIds,
+        uint256 expectedAmount
+    ) external nonReentrant {
+        require(
+            msg.sender == IVault(vaultAddress).strategistAddr(),
+            "Caller is not the Strategist"
+        );
+        uint256 startingBalance = payable(address(this)).balance;
+        uint256 lastIndex = withdrawalQueue.getLastCheckpointIndex();
+        uint256[] memory hintIds = withdrawalQueue.findCheckpointHints(
+            _requestIds,
+            1,
+            lastIndex
+        );
+        withdrawalQueue.claimWithdrawals(_requestIds, hintIds);
+
+        uint256 currentBalance = payable(address(this)).balance;
+        uint256 withdrawalAmount = currentBalance - startingBalance;
+        // Withdrawal amount should be within 2 wei of expected amount
+        require(
+            withdrawalAmount + 2 >= expectedAmount &&
+                withdrawalAmount <= expectedAmount,
+            "Withdrawal amount not expected"
+        );
+
+        emit WithdrawalClaims(_requestIds, withdrawalAmount);
+
+        outstandingWithdrawals -= withdrawalAmount;
+        weth.deposit{ value: currentBalance }();
+        // slither-disable-next-line unchecked-transfer
+        weth.transfer(vaultAddress, currentBalance);
+        emit Withdrawal(
+            address(weth),
+            address(withdrawalQueue),
+            currentBalance
+        );
+    }
+
+    /**
+     * @notice Withdraw all assets from this strategy, and transfer to the Vault.
+     * In correct operation, this strategy should never hold any assets.
+     */
+    function withdrawAll() external override onlyVaultOrGovernor nonReentrant {
+        if (payable(address(this)).balance > 0) {
+            weth.deposit{ value: payable(address(this)).balance }();
+        }
+        uint256 wethBalance = weth.balanceOf(address(this));
+        if (wethBalance > 0) {
+            // slither-disable-next-line unchecked-transfer
+            weth.transfer(vaultAddress, wethBalance);
+            emit Withdrawal(address(weth), address(0), wethBalance);
+        }
+        uint256 stEthBalance = stETH.balanceOf(address(this));
+        if (stEthBalance > 0) {
+            // slither-disable-next-line unchecked-transfer
+            stETH.transfer(vaultAddress, stEthBalance);
+            emit Withdrawal(address(stETH), address(0), stEthBalance);
+        }
+    }
+
+    /**
+     * @notice Returns the amount of queued stETH that will be returned as WETH.
+     * We return this as a WETH asset, since that is what it will eventually be returned as.
+     * We only return the outstandingWithdrawals, because the contract itself should never hold any funds.
+     * @param _asset      Address of the asset
+     * @return balance    Total value of the asset in the platform
+     */
+    function checkBalance(address _asset)
+        external
+        view
+        override
+        returns (uint256 balance)
+    {
+        if (_asset == address(weth)) {
+            return outstandingWithdrawals;
+        } else if (_asset == address(stETH)) {
+            return 0;
+        } else {
+            revert("Unexpected asset address");
+        }
+    }
+
+    /**
+     * @notice Approve the spending of all assets by their corresponding cToken,
+     *      if for some reason is it necessary.
+     */
+    function safeApproveAllTokens() public override {
+        // slither-disable-next-line unused-return
+        stETH.approve(address(withdrawalQueue), type(uint256).max);
+    }
+
+    /**
+     * @notice Check if an asset is supported.
+     * @param _asset    Address of the asset
+     * @return bool     Whether asset is supported
+     */
+    function supportsAsset(address _asset) public pure override returns (bool) {
+        // stETH can be deposited by the vault and balances are reported in WETH
+        return _asset == address(stETH) || _asset == address(weth);
+    }
+
+    /// @notice Needed to receive ETH when withdrawal requests are claimed
+    receive() external payable {}
+
+    function _abstractSetPToken(address, address) internal pure override {
+        revert("No pTokens are used");
+    }
+}