Solidity Coverage - Signature example (#533)

- Adding test coverage for signature example and its tests,
- Also fixed a typo on TypeOps tests

---------
Signed-off-by: Alfredo Gutierrez <[email protected]>
Signed-off-by: Nana Essilfie-Conduah <[email protected]>
Co-authored-by: Nana Essilfie-Conduah <[email protected]>

contracts/solidity/signature-example/ReceiverPays.sol

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: Apache-2.0
+pragma solidity >=0.7.0 <0.9.0;
+
+contract ReceiverPays {
+    address owner = msg.sender;
+
+    mapping(uint256 => bool) usedNonces;
+
+    constructor() payable {}
+
+    function claimPayment(uint256 amount, uint256 nonce, bytes memory signature) external {
+        require(!usedNonces[nonce], "invalid nonce");
+        usedNonces[nonce] = true;
+
+        // this recreates the message that was signed on the client
+        bytes32 message = prefixed(keccak256(abi.encodePacked(msg.sender, amount, nonce, this)));
+
+        require(recoverSigner(message, signature) == owner, "invalid signature");
+
+        payable(msg.sender).transfer(amount);
+    }
+
+    /// destroy the contract and reclaim the leftover funds.
+    function shutdown() external {
+        require(msg.sender == owner, "only owner can shutdown");
+        // This will report a warning due to deprecated selfdestruct
+        selfdestruct(payable(msg.sender));
+    }
+
+    /// signature methods.
+    function splitSignature(bytes memory sig)
+        internal
+        pure
+        returns (uint8 v, bytes32 r, bytes32 s)
+    {
+        require(sig.length == 65);
+
+        assembly {
+            // first 32 bytes, after the length prefix.
+            r := mload(add(sig, 32))
+            // second 32 bytes.
+            s := mload(add(sig, 64))
+            // final byte (first byte of the next 32 bytes).
+            v := byte(0, mload(add(sig, 96)))
+        }
+
+        return (v, r, s);
+    }
+
+    function recoverSigner(bytes32 message, bytes memory sig)
+        internal
+        pure
+        returns (address)
+    {
+        (uint8 v, bytes32 r, bytes32 s) = splitSignature(sig);
+
+        return ecrecover(message, v, r, s);
+    }
+
+    /// builds a prefixed hash to mimic the behavior of eth_sign.
+    function prefixed(bytes32 hash) internal pure returns (bytes32) {
+        return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
+    }
+}

test/constants.js

@@ -67,6 +67,7 @@ const Path = {
   HIP583_ERC721Mock: 'contracts/hip-583/ERC721Mock.sol:ERC721Mock',
   HRC: 'contracts/hrc/HRC.sol:HRC',
   TYPE_OPS: 'contracts/solidity/typeops/TypeOps.sol:TypeOps',
+  RECEIVER_PAYS: 'contracts/solidity/signature-example/ReceiverPays.sol:ReceiverPays',
 }
 
 const Contract = {

test/solidity/signature-example/ReceiverPays.js

@@ -0,0 +1,97 @@
+/*-
+ *
+ * Hedera Smart Contracts
+ *
+ * Copyright (C) 2023 Hedera Hashgraph, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+const { expect } = require('chai')
+const { ethers } = require('hardhat')
+const Constants = require('../../constants')
+const abi = require('ethereumjs-abi');
+
+describe('@solidityequiv4 Signature Example ReceiverPays Test Suite', function () {
+    let receiverPaysContract, provider, signers, currentNonce, sender, receiver;
+
+    before(async function () {
+        signers = await ethers.getSigners();
+        sender = signers[0];
+        receiver = signers[1];
+        ethers.provider = sender.provider;
+        provider = ethers.provider;
+        const factory = await ethers.getContractFactory(Constants.Path.RECEIVER_PAYS);
+        const initialFund = ethers.utils.parseEther('4');
+        receiverPaysContract = await factory.deploy({ gasLimit: 15000000, value: initialFund });
+        currentNonce = 0;
+    });
+
+    // claim payment
+    it('receiver should be able to claim payment and pay for transaction fees', async function () {
+        const recipientAddress = receiver.address;        
+        const contractBalanceBefore = await signers[0].provider.getBalance(receiverPaysContract.address);
+        // There is a discrepancy between the amount of decimals for 1 ETH and 1 HBAR. see the tinybar to wei coefficient of 10_000_000_000
+        // it should be ethers.utils.parseEther('1');
+        const amountToTransfer = 100000000; 
+
+        // Generate signature for payment
+        const signedPayment = await signPayment(recipientAddress, amountToTransfer, currentNonce, receiverPaysContract.address);       
+
+        // Claim payment        
+        const contract = receiverPaysContract.connect(receiver);
+        await contract.claimPayment(amountToTransfer, currentNonce, signedPayment);
+
+        // Verify payment is received
+        const contractBalanceAfter = await signers[0].provider.getBalance(receiverPaysContract.address);
+
+        expect(contractBalanceAfter).to.equal(contractBalanceBefore.sub(ethers.utils.parseEther('1')));
+
+        currentNonce++;
+    });
+
+    // try to shutdown contract as receiver
+    it('receiver should not be able to shutdown contract', async function () {
+        const contract = receiverPaysContract.connect(receiver);
+        let errorOccurred = false;
+        try {
+            const tx = await contract.shutdown();
+            await tx.wait();
+        } catch (error) {
+            expect(error.reason).to.be.equal("transaction failed");
+            errorOccurred = true;
+        }
+        expect(errorOccurred).to.be.true;
+        // verify the contract still has balance
+        const contractBalance = await signers[0].provider.getBalance(receiverPaysContract.address);
+        expect(contractBalance).to.be.gt(0);
+    });
+
+    // should be able to shutdown as sender
+    it('sender should be able to shutdown contract', async function () {
+        const contract = receiverPaysContract.connect(sender);
+        await contract.shutdown();
+        // verify contract is shutdown, contract should have no balance left
+        const contractBalance = await signers[0].provider.getBalance(receiverPaysContract.address);
+        expect(contractBalance).to.be.equal(0);
+    });
+
+
+    async function signPayment(recipient, amount, nonce, contractAddress) {
+        const hash = ethers.utils.solidityKeccak256(["address", "uint256", "uint256", "address"],[recipient, amount, nonce, contractAddress])        
+        // Sign the hash
+        const signature = await sender.signMessage(ethers.utils.arrayify(hash));
+        return signature;
+    }
+
+});

test/solidity/typeops/TypeOps.js

@@ -22,7 +22,7 @@ const { ethers } = require('hardhat')
 const Constants = require('../../constants')
 
 describe('@solidityevmequiv1 TypeOps Test Suite', function () {
-    let cryptoMathContract, provider, signers;
+    let typeOpsContract, provider, signers;
 
     before(async function () {
         signers = await ethers.getSigners();
@@ -85,6 +85,4 @@ describe('@solidityevmequiv1 TypeOps Test Suite', function () {
         const res = await typeOpsContract.typeUintMax();
         expect(res).to.equal(expectedUintMax);
     });
-
-
 });