PER Integration Into IonicLiquidator

.vscode/settings.json

@@ -7,5 +7,8 @@
     "editor.defaultFormatter": "esbenp.prettier-vscode"
   },
   "solidity.packageDefaultDependenciesContractsDirectory": "contracts",
-  "solidity.packageDefaultDependenciesDirectory": "lib"
+  "solidity.packageDefaultDependenciesDirectory": "lib",
+  "[solidity]": {
+    "editor.defaultFormatter": "esbenp.prettier-vscode"
+  }
 }

contracts/IonicLiquidator.sol

@@ -19,13 +19,16 @@ import "./external/uniswap/UniswapV2Library.sol";
 
 import { ICErc20 } from "./compound/CTokenInterfaces.sol";
 
+import "@pythnetwork/express-relay-sdk-solidity/IExpressRelay.sol";
+import "@pythnetwork/express-relay-sdk-solidity/IExpressRelayFeeReceiver.sol";
+
 /**
  * @title IonicLiquidator
  * @author David Lucid <[email protected]> (https://github.com/davidlucid)
  * @notice IonicLiquidator safely liquidates unhealthy borrowers (with flashloan support).
  * @dev Do not transfer NATIVE or tokens directly to this address. Only send NATIVE here when using a method, and only approve tokens for transfer to here when using a method. Direct NATIVE transfers will be rejected and direct token transfers will be lost.
  */
-contract IonicLiquidator is OwnableUpgradeable, ILiquidator, IUniswapV2Callee {
+contract IonicLiquidator is OwnableUpgradeable, ILiquidator, IUniswapV2Callee, IExpressRelayFeeReceiver {
   using AddressUpgradeable for address payable;
   using SafeERC20Upgradeable for IERC20Upgradeable;
 
@@ -64,6 +67,23 @@ contract IonicLiquidator is OwnableUpgradeable, ILiquidator, IUniswapV2Callee {
    */
   uint8 public flashSwapFee;
 
+  /**
+   * @dev Addres of Pyth Express Relay for preventing value leakage in liquidations.
+   */
+  IExpressRelay private expressRelay;
+
+  modifier onlyPERPermissioned(
+    address borrower,
+    ICErc20 cErc20,
+    ICErc20 cTokenCollateral
+  ) {
+    require(
+      expressRelay.isPermissioned(address(this), abi.encode(borrower, cErc20, cTokenCollateral)),
+      "invalid liquidation"
+    );
+    _;
+  }
+
   function initialize(
     address _wtoken,
     address _uniswapV2router,
@@ -119,7 +139,7 @@ contract IonicLiquidator is OwnableUpgradeable, ILiquidator, IUniswapV2Callee {
     ICErc20 cErc20,
     ICErc20 cTokenCollateral,
     uint256 minOutputAmount
-  ) external returns (uint256) {
+  ) external onlyPERPermissioned(borrower, cErc20, cTokenCollateral) returns (uint256) {
     // Transfer tokens in, approve to cErc20, and liquidate borrow
     require(repayAmount > 0, "Repay amount (transaction value) must be greater than 0.");
     IERC20Upgradeable underlying = IERC20Upgradeable(cErc20.underlying());
@@ -150,6 +170,7 @@ contract IonicLiquidator is OwnableUpgradeable, ILiquidator, IUniswapV2Callee {
    */
   function safeLiquidateToTokensWithFlashLoan(LiquidateToTokensWithFlashSwapVars calldata vars)
     external
+    onlyPERPermissioned(vars.borrower, vars.cErc20, vars.cTokenCollateral)
     returns (uint256)
   {
     // Input validation
@@ -199,6 +220,12 @@ contract IonicLiquidator is OwnableUpgradeable, ILiquidator, IUniswapV2Callee {
     require(payable(msg.sender).isContract(), "Sender is not a contract.");
   }
 
+  /**
+   * @notice receiveAuctionProceedings function - receives native token from the express relay
+   * You can use permission key to distribute the received funds to users who got liquidated, LPs, etc...
+   */
+  function receiveAuctionProceedings(bytes calldata permissionKey) external payable {}
+
   /**
    * @dev Callback function for Uniswap flashloans.
    */
@@ -419,6 +446,10 @@ contract IonicLiquidator is OwnableUpgradeable, ILiquidator, IUniswapV2Callee {
     }
   }
 
+  function setExpressRelay(IExpressRelay _expressRelay) external onlyOwner {
+    expressRelay = _expressRelay;
+  }
+
   /**
    * @dev Redeem "special" collateral tokens (before swapping the output for borrowed tokens to be repaid via Uniswap).
    * Public visibility because we have to call this function externally if called from a payable IonicLiquidator function (for some reason delegatecall fails when called with msg.value > 0).

package.json

@@ -18,5 +18,8 @@
   "devDependencies": {
     "prettier": "^2.6.2",
     "prettier-plugin-solidity": "^1.0.0-beta.19"
+  },
+  "dependencies": {
+    "@pythnetwork/express-relay-sdk-solidity": "^0.2.0"
   }
 }

remappings.txt

@@ -1,4 +1,5 @@
 flywheel/=lib/flywheel-v2/src/
 solidity-bytes-utils/=lib/solidity-bytes-utils/
 @openzeppelin=lib/openzeppelin-contracts/
-@pythnetwork/pyth-sdk-solidity/=lib/pyth-sdk-solidity/
+@pythnetwork/pyth-sdk-solidity/=lib/pyth-sdk-solidity/
+@pythnetwork/express-relay-sdk-solidity/=node_modules/@pythnetwork/express-relay-sdk-solidity