feat: add contract verifier (#285)

contracts/SpokePoolVerifier.sol

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-3.0-only
+pragma solidity ^0.8.0;
+
+import "@openzeppelin/contracts/utils/Address.sol";
+import "./interfaces/SpokePoolInterface.sol";
+
+/**
+ * @notice SpokePoolVerifier is a contract that verifies that the SpokePool exists on this chain before sending ETH to it.
+ */
+contract SpokePoolVerifier {
+    using Address for address;
+
+    function deposit(
+        SpokePoolInterface spokePool,
+        address recipient,
+        address originToken,
+        uint256 amount,
+        uint256 destinationChainId,
+        int64 relayerFeePct,
+        uint32 quoteTimestamp,
+        bytes memory message,
+        uint256 maxCount
+    ) external payable {
+        require(msg.value == amount, "msg.value != amount");
+        require(address(spokePool).isContract(), "spokePool is not a contract");
+        spokePool.deposit{ value: msg.value }(
+            recipient,
+            originToken,
+            amount,
+            destinationChainId,
+            relayerFeePct,
+            quoteTimestamp,
+            message,
+            maxCount
+        );
+    }
+}

deploy/023_deploy_spoke_pool_verifier.ts

@@ -0,0 +1,19 @@
+import { DeployFunction } from "hardhat-deploy/types";
+import { HardhatRuntimeEnvironment } from "hardhat/types";
+
+const func: DeployFunction = async function (hre: HardhatRuntimeEnvironment) {
+  const { deployments, getNamedAccounts } = hre;
+  const { deploy } = deployments;
+
+  const { deployer } = await getNamedAccounts();
+
+  await deploy("SpokePoolVerifier", {
+    from: deployer,
+    log: true,
+    skipIfAlreadyDeployed: true,
+    deterministicDeployment: "0x1234", // Salt for the create2 call.
+  });
+};
+
+module.exports = func;
+func.tags = ["SpokePoolVerifier", "polygon", "mainnet", "optimism", "arbitrum", "zksync"];