Add mint & burn to L2 ETH (#178)

* Initial attempt at adding mint to ETH

* Fix lint error

* fix modifier
Co-authored-by: Ben Jones <ben@pseudonym.party>

packages/contracts/contracts/optimistic-ethereum/OVM/precompiles/OVM_ETH.sol

@@ -2,14 +2,18 @@
 // +build ovm
 pragma solidity >0.5.0 <0.8.0;
 
+/* Library Imports */
+import { Lib_AddressResolver } from "../../libraries/resolver/Lib_AddressResolver.sol";
+
 /* Interface Imports */
 import { iOVM_ERC20 } from "../../iOVM/precompiles/iOVM_ERC20.sol";
+import { iOVM_BaseCrossDomainMessenger } from "../../iOVM/bridge/iOVM_BaseCrossDomainMessenger.sol";
 
 /**
  * @title OVM_ETH
  * @dev L2 CONTRACT (COMPILED)
  */
-contract OVM_ETH is iOVM_ERC20 {
+contract OVM_ETH is iOVM_ERC20, Lib_AddressResolver {
 
     uint256 constant private MAX_UINT256 = 2**256 - 1;
     mapping (address => uint256) public balances;
@@ -26,11 +30,15 @@ contract OVM_ETH is iOVM_ERC20 {
     uint256 public override totalSupply;
 
     constructor(
+        address _libAddressManager,
         uint256 _initialAmount,
         string memory _tokenName,
         uint8 _decimalUnits,
         string memory _tokenSymbol
-    ) public {
+    )
+        public
+        Lib_AddressResolver(_libAddressManager)
+    {
         balances[msg.sender] = _initialAmount;               // Give the creator all initial tokens
         totalSupply = _initialAmount;                        // Update total supply
         name = _tokenName;                                   // Set the name for display purposes
@@ -38,6 +46,13 @@ contract OVM_ETH is iOVM_ERC20 {
         symbol = _tokenSymbol;                               // Set the symbol for display purposes
     }
 
+    modifier onlyOVMETHBridge() {
+        address bridgeOnL2 = resolve("OVM_L2ETHBridge");
+        require(bridgeOnL2 != address(0), "OVM_L2ETHBridge is not yet initialized.");
+        require(msg.sender == bridgeOnL2, "Only callable by OVM ETH Deposit/Withdrawal contract");
+        _;
+    }
+
     function transfer(address _to, uint256 _value) external override returns (bool success) {
         require(balances[msg.sender] >= _value);
         balances[msg.sender] -= _value;
@@ -71,4 +86,23 @@ contract OVM_ETH is iOVM_ERC20 {
     function allowance(address _owner, address _spender) external view override returns (uint256 remaining) {
         return allowed[_owner][_spender];
     }
-}
+
\ No newline at end of file
+    function mint(address _account, uint256 _amount) external onlyOVMETHBridge returns (bool success) {
+        uint256 newTotalSupply = totalSupply + _amount;
+        require(newTotalSupply >= totalSupply, "SafeMath: addition overflow");
+        totalSupply = newTotalSupply;
+        balances[_account] += _amount;
+
+        emit Mint(_account, _amount);
+        return true;
+    }
+
+    function burn(address _account, uint256 _amount) external onlyOVMETHBridge returns (bool success) {
+        require(balances[_account] >= _amount, "Unable to burn due to insufficient balance");
+        balances[_account] -= _amount;
+        totalSupply -= _amount;
+
+        emit Burn(_account, _amount);
+        return true;
+    }
+}

packages/contracts/contracts/optimistic-ethereum/iOVM/precompiles/iOVM_ERC20.sol

@@ -49,4 +49,6 @@ interface iOVM_ERC20 {
     // solhint-disable-next-line no-simple-event-func-name
     event Transfer(address indexed _from, address indexed _to, uint256 _value);
     event Approval(address indexed _owner, address indexed _spender, uint256 _value);
-}
+    event Mint(address indexed _account, uint256 _amount);
\ No newline at end of file
+    event Burn(address indexed _account, uint256 _amount);
+}

packages/contracts/src/contract-deployment/config.ts

@@ -210,7 +210,13 @@ export const makeContractDeployConfig = async (
     },
     OVM_ETH: {
       factory: getContractFactory('OVM_ETH'),
-      params: [config.ethConfig.initialAmount, 'Ether', 18, 'ETH'],
+      params: [
+        AddressManager.address,
+        config.ethConfig.initialAmount,
+        'Ether',
+        18,
+        'ETH',
+      ],
     },
     'OVM_ChainStorageContainer:CTC:batches': {
       factory: getContractFactory('OVM_ChainStorageContainer'),