Merge pull request #18 from AugustoL/feat/dynamic-proxy

Dynamic Proxy

contracts/ERC827/ERC827.sol

@@ -3,7 +3,7 @@
 pragma solidity ^0.5.2;
 
 import "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";
-import "./ERC827Proxy.sol";
+import "../utils/Create2.sol";
 
 
 /**
@@ -15,13 +15,14 @@ import "./ERC827Proxy.sol";
  */
 contract ERC827 is ERC20 {
 
-  ERC827Proxy public proxy;
+  bytes public proxyBytecode;
+  mapping(address => uint256) public nonces;
 
   /**
    * @dev Constructor
    */
-  constructor() public {
-    proxy = new ERC827Proxy();
+  constructor(bytes memory _proxyBytecode) public {
+    proxyBytecode = _proxyBytecode;
   }
 
   /**
@@ -85,11 +86,14 @@ contract ERC827 is ERC20 {
    * @param _data ABI-encoded contract call to call `_to` address.
    */
   function _call(address _to, bytes memory _data) internal {
+    bytes32 salt = keccak256(abi.encodePacked(msg.sender, _to, nonces[msg.sender]));
+    address proxy = Create2.deploy(salt, proxyBytecode);
     // solium-disable-next-line security/no-call-value, no-unused-vars
     (bool success, bytes memory data) = address(proxy).call.value(msg.value)(
-      abi.encodeWithSelector(proxy.callContractFunctionSignature(), _to, _data)
+      abi.encodeWithSelector(bytes4(keccak256("callContract(address,bytes)")), _to, _data)
     );
     require(success, "Call to external contract failed");
+    nonces[msg.sender].add(1);
   }
 
 }

contracts/ERC827/ERC827Migratable.sol

@@ -24,7 +24,7 @@ contract ERC827Migratable is ERC827, Ownable {
    * be migrated.
    * @param _erc20Token The address of the erc20 token to be migrated
    */
-  constructor(address _erc20Token) public {
+  constructor(address _erc20Token, bytes memory proxyBytecode) ERC827(proxyBytecode) public {
     require(_erc20Token != address(0), "Incorrect ERC20 token address");
     erc20Token = IERC20(_erc20Token);
   }

contracts/ERC827/ERC827Proxy.sol

@@ -2,6 +2,8 @@
 
 pragma solidity ^0.5.2;
 
+import "./IERC827.sol";
+
 
 /**
  * @title ERC827Proxy
@@ -11,16 +13,13 @@ pragma solidity ^0.5.2;
  */
 contract ERC827Proxy {
 
-  address public token;
-  bytes4 public callContractFunctionSignature = bytes4(
-    keccak256("callContract(address,bytes)")
-  );
+  IERC827 public token;
 
   /**
    * @dev constructor
    */
   constructor() public {
-    token = address(msg.sender);
+    token = IERC827(msg.sender);
   }
 
   /**
@@ -36,8 +35,12 @@ contract ERC827Proxy {
       "Proxy only can execute calls from the token contract"
     );
     // solium-disable-next-line security/no-call-value, no-unused-vars
-    (bool success, bytes memory data) = _target .call.value(msg.value)(_data);
+    (bool success, bytes memory data) = _target.call.value(msg.value)(_data);
     require(success, "Proxy call failed");
+    require(token.balanceOf(address(this)) == 0, "Cant end proxy call with token balance in proxy");
+    require(address(this).balance == 0, "Cant end proxy call with eth balance in proxy");
+
+    selfdestruct(address(0));
     return true;
   }
 

contracts/mocks/ERC20TokenMock.sol → contracts/mocks/ERC20Mock.sol

@@ -5,7 +5,7 @@ import "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";
 
 
 // mock class using ERC20 Token
-contract ERC20TokenMock is ERC20 {
+contract ERC20Mock is ERC20 {
 
   constructor(address initialAccount, uint256 initialBalance) public {
     _mint(initialAccount, initialBalance);

contracts/mocks/ERC827Mock.sol

@@ -0,0 +1,14 @@
+pragma solidity ^0.5.0;
+
+
+import "../ERC827/ERC827.sol";
+
+
+// mock class using ERC827 Token
+contract ERC827Mock is ERC827 {
+
+  constructor(address initialAccount, uint256 initialBalance, bytes memory proxyBytecode) public ERC827(proxyBytecode) {
+    _mint(initialAccount, initialBalance);
+  }
+
+}

contracts/mocks/ERC827Receiver.sol

@@ -0,0 +1,47 @@
+pragma solidity ^0.5.0;
+
+import "../ERC827/ERC827.sol";
+import "../utils/Create2.sol";
+
+contract ERC827Receiver {
+
+  event Show(bytes32 b32, uint256 number, string text, uint256 value);
+  event TokensTransfered(address from, uint256 amount);
+
+  function showMessage(bytes32 message, uint256 number, string memory text)
+    public payable returns (bool)
+  {
+    emit Show(message, number, text, msg.value);
+    return true;
+  }
+
+  function fail() public {
+    revert("ERC827Receiver function failed");
+  }
+
+  function callContarct(address to, bytes memory data) public returns (bool) {
+    // solium-disable-next-line security/no-low-level-calls, no-unused-vars
+    (bool success, bytes memory _data) = to.call(data);
+    require(success, "ERC827Receiver callContarct function failed");
+    return true;
+  }
+
+  function receiveTokens(address sender, address token) public {
+    uint256 allowance = ERC827(token).allowance(sender, address(this));
+    ERC827(token).transferFrom(sender, address(this), allowance);
+    emit TokensTransfered(sender, allowance);
+  }
+
+  function receiveVerifiedTokens(address sender, ERC827 token) public {
+    address proxy = Create2.computeAddress(
+      address(token),
+      keccak256(abi.encodePacked(sender, address(this), token.nonces(sender))),
+      token.proxyBytecode()
+    );
+    require(msg.sender == proxy, "ERC827Receiver: Sender invalid");
+    uint256 allowance = ERC827(token).allowance(sender, address(this));
+    ERC827(token).transferFrom(sender, address(this), allowance);
+    emit TokensTransfered(sender, allowance);
+  }
+
+}

contracts/utils/Create2.sol

@@ -0,0 +1,63 @@
+pragma solidity ^0.5.0;
+
+/**
+ * @title Create2
+ *
+ * @dev Utility library that focus on the use of CREATE2 EVM opcode for
+ * contracts deployment. It also provides a function to precompute the address
+ * where the smart contracts with the specified salt and bytecode would be
+ * deployed.
+ */
+library Create2 {
+
+    // Event triggered when a contract is deployed
+    event Create2Deployed(address addr, bytes32 salt);
+
+    /**
+     * @dev Deploy contract with CREATE2
+     * @param salt The salt used to the contract address computation
+     * @param code The bytecode of of the contract to be deployed
+     */
+    function deploy(bytes32 salt, bytes memory code) internal returns (address) {
+        address addr = _deploy(salt, code);
+        emit Create2Deployed(addr, salt);
+        return addr;
+    }
+
+    /**
+     * @dev Function to compute the address of a contract created with CREATE2.
+     * @param deployer the address of the contract that will deploy the contract
+     * @param salt The salt used to the contract address computation
+     * @param code The bytecode of the contract to be deployed
+     * @return the computed address of the smart contract.
+     */
+    function computeAddress(
+        address deployer, bytes32 salt, bytes memory code
+    ) internal view returns (address) {
+        bytes32 codeHash = keccak256(code);
+        bytes32 _data = keccak256(
+            abi.encodePacked(bytes1(0xff), deployer, salt, codeHash)
+        );
+        return address(bytes20(_data << 96));
+    }
+
+    /**
+     * @dev Internal function to deploy contract with CREATE2
+     * @param _salt The salt used to the contract address computation
+     * @param _code The bytecode of the contract to be deployed
+     */
+    function _deploy(
+        bytes32 _salt, bytes memory _code
+    ) private returns(address) {
+        address _addr;
+        // solhint-disable-next-line no-inline-assembly
+        assembly {
+            _addr := create2(0, add(_code, 0x20), mload(_code), _salt)
+            if iszero(extcodesize(_addr)) {
+                revert(0, 0)
+            }
+        }
+        return _addr;
+    }
+
+}

test/ERC827/ERC20Migration.js

@@ -1,7 +1,8 @@
 
 import EVMRevert from '../helpers/EVMRevert';
-var ERC20TokenMock = artifacts.require('ERC20TokenMock');
-var ERC827Migratable = artifacts.require('ERC827Migratable');
+const ERC20Mock = artifacts.require('ERC20Mock');
+const ERC827Migratable = artifacts.require('ERC827Migratable');
+const ERC827Proxy = artifacts.require('ERC827Proxy');
 
 require('chai').use(require('chai-as-promised')).should();
 const assert = require('chai').assert;
@@ -10,8 +11,8 @@ contract('ERC827Migratable', function (accounts) {
   let erc20Token, erc827Token;
 
   beforeEach(async function () {
-    erc20Token = await ERC20TokenMock.new(accounts[1], 100);
-    erc827Token = await ERC827Migratable.new(erc20Token.address);
+    erc20Token = await ERC20Mock.new(accounts[1], 100);
+    erc827Token = await ERC827Migratable.new(erc20Token.address, ERC827Proxy.bytecode);
     await erc20Token.transfer(accounts[2], 10, { from: accounts[1] });
     await erc20Token.transfer(accounts[3], 20, { from: accounts[1] });
     await erc20Token.transfer(accounts[4], 30, { from: accounts[1] });