✍️ Add PoR feature control functions to TokenControllerV3 (#1205)

* Add Proof of Reserve feature control functions to TokenControllerV3

* Reorder elements of IPoRToken interface

* Make TrueUSDWithPoR implement ITrueCurrency interface

* Remove unusable refundGasWithHook function

* Add missing licence declarations

* Emit events at the end of the function for consistency

* Always emit ProofOfReserveDisabled when proofOfReserveEnabled is set to false

* Emit an event when Proof Of Reserve enabler is set

* Revert line reorder in two setters

* Remove placeholder test

* Add previousEnabler param to ProofOfReserveEnablerSet event

Author: Michał Sieczkowski

packages/contracts-por/contracts/TokenControllerV3.sol

@@ -1,10 +1,12 @@
+// SPDX-License-Identifier: MIT
 pragma solidity 0.6.10;
 
 import {SafeMath} from "@openzeppelin/contracts/math/SafeMath.sol";
 import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
 import {IRegistry} from "./interface/IRegistry.sol";
 import {IOwnedUpgradeabilityProxy} from "./interface/IOwnedUpgradeabilityProxy.sol";
 import {ITrueCurrency} from "./interface/ITrueCurrency.sol";
+import {IPoRToken} from "./interface/IPoRToken.sol";
 
 /**
  * @dev Contract that can be called with a gas refund
@@ -78,11 +80,13 @@ contract TokenControllerV3 {
     address public fastPause; // deprecated
     address public trueRewardManager; // deprecated
 
+    address public proofOfReserveEnabler;
+
     // Registry attributes for admin keys
     bytes32 public constant IS_MINT_PAUSER = "isTUSDMintPausers";
     bytes32 public constant IS_MINT_RATIFIER = "isTUSDMintRatifier";
     bytes32 public constant IS_REDEMPTION_ADMIN = "isTUSDRedemptionAdmin";
-    bytes32 public constant IS_GAS_REFUNDER = "isGasRefunder";
+    // bytes32 public constant IS_GAS_REFUNDER = "isGasRefunder"; // deprecated
     bytes32 public constant IS_REGISTRY_ADMIN = "isRegistryAdmin";
 
     // paused version of TrueCurrency in Production
@@ -114,11 +118,6 @@ contract TokenControllerV3 {
         _;
     }
 
-    modifier onlyGasRefunder() {
-        require(registry.hasAttribute(msg.sender, IS_GAS_REFUNDER) || msg.sender == owner, "must be gas refunder or owner");
-        _;
-    }
-
     modifier onlyRegistryAdmin() {
         require(registry.hasAttribute(msg.sender, IS_REGISTRY_ADMIN) || msg.sender == owner, "must be registry admin or owner");
         _;
@@ -153,6 +152,8 @@ contract TokenControllerV3 {
 
     /// @dev Emitted when mint key was replaced
     event TransferMintKey(address indexed previousMintKey, address indexed newMintKey);
+    /// @dev Emitted when Proof Of Reserve enabler was set
+    event ProofOfReserveEnablerSet(address previousEnabler, address newEnabler);
     /// @dev Emitted when mint was ratified
     event MintRatified(uint256 indexed opIndex, address indexed ratifier);
     /// @dev Emitted when mint is revoked
@@ -199,6 +200,14 @@ contract TokenControllerV3 {
         _;
     }
 
+    /**
+     * @dev Modifier throws if called by any account other than proofOfReserveEnabler or owner.
+     */
+    modifier onlyProofOfReserveEnablerOrOwner() {
+        require(msg.sender == proofOfReserveEnabler || msg.sender == owner, "only proofOfReserveEnabler or owner");
+        _;
+    }
+
     /**
      * @dev Allows the current owner to set the pendingOwner address.
      * @param newOwner The address to transfer ownership to.
@@ -451,7 +460,7 @@ contract TokenControllerV3 {
 
     /*
     ========================================
-    Key management
+    Key and role management
     ========================================
     */
 
@@ -465,6 +474,11 @@ contract TokenControllerV3 {
         mintKey = _newMintKey;
     }
 
+    function setProofOfReserveEnabler(address enabler) external onlyOwner {
+        emit ProofOfReserveEnablerSet(proofOfReserveEnabler, enabler);
+        proofOfReserveEnabler = enabler;
+    }
+
     /*
     ========================================
     Mint Pausing
@@ -616,19 +630,37 @@ contract TokenControllerV3 {
         token.setCanBurn(burner, canBurn);
     }
 
+    /*
+    ========================================
+    Proof of Reserve, administrative
+    ========================================
+    */
+
+    /**
+     * Set new chainReserveFeed address
+     */
+    function setChainReserveFeed(address newFeed) external onlyOwner {
+        IPoRToken(address(token)).setChainReserveFeed(newFeed);
+    }
+
+    /**
+     * Set new chainReserveHeartbeat
+     */
+    function setChainReserveHeartbeat(uint256 newHeartbeat) external onlyProofOfReserveEnablerOrOwner {
+        IPoRToken(address(token)).setChainReserveHeartbeat(newHeartbeat);
+    }
+
+    /**
+     * Disable Proof of Reserve check
+     */
+    function disableProofOfReserve() external onlyProofOfReserveEnablerOrOwner {
+        IPoRToken(address(token)).disableProofOfReserve();
+    }
+
     /**
-     * Call hook in `hookContract` with gas refund
+     * Enable Proof of Reserve check
      */
-    function refundGasWithHook(IHook hookContract) external onlyGasRefunder {
-        // calculate start gas amount
-        uint256 startGas = gasleft();
-        // call hook
-        hookContract.hook();
-        // calculate gas used
-        uint256 gasUsed = startGas.sub(gasleft());
-        // 1 refund = 15,000 gas. EVM refunds maximum half of used gas, so divide by 2.
-        // Add 20% to compensate inter contract communication
-        // (x + 20%) / 2 / 15000 = x / 25000
-        token.refundGas(gasUsed.div(25000));
+    function enableProofOfReserve() external onlyProofOfReserveEnablerOrOwner {
+        IPoRToken(address(token)).enableProofOfReserve();
     }
 }

packages/contracts-por/contracts/TrueCurrency.sol

@@ -68,7 +68,7 @@ abstract contract TrueCurrency is BurnableTokenWithBounds {
      * - `account` cannot be blacklisted.
      * - `account` cannot be a redemption address.
      */
-    function mint(address account, uint256 amount) external onlyOwner {
+    function mint(address account, uint256 amount) override external onlyOwner {
         require(!isBlacklisted[account], "TrueCurrency: account is blacklisted");
         require(!isRedemptionAddress(account), "TrueCurrency: account is a redemption address");
         _mint(account, amount);
@@ -99,7 +99,7 @@ abstract contract TrueCurrency is BurnableTokenWithBounds {
      *
      * - `msg.sender` should be owner.
      */
-    function setCanBurn(address account, bool _canBurn) external onlyOwner {
+    function setCanBurn(address account, bool _canBurn) override external onlyOwner {
         canBurn[account] = _canBurn;
     }
 

packages/contracts-por/contracts/TrueCurrencyWithPoR.sol

@@ -59,8 +59,9 @@ abstract contract TrueCurrencyWithPoR is TrueCurrency, IPoRToken {
     function setChainReserveFeed(address newFeed) external override onlyOwner {
         emit NewChainReserveFeed(chainReserveFeed, newFeed);
         chainReserveFeed = newFeed;
-        if (newFeed == address(0) && proofOfReserveEnabled) {
+        if (newFeed == address(0)) {
             proofOfReserveEnabled = false;
+            emit ProofOfReserveDisabled();
         }
     }
 
@@ -79,8 +80,8 @@ abstract contract TrueCurrencyWithPoR is TrueCurrency, IPoRToken {
      * @dev Admin function to disable Proof of Reserve
      */
     function disableProofOfReserve() external override onlyOwner {
-        emit ProofOfReserveDisabled();
         proofOfReserveEnabled = false;
+        emit ProofOfReserveDisabled();
     }
 
     /**
@@ -89,7 +90,7 @@ abstract contract TrueCurrencyWithPoR is TrueCurrency, IPoRToken {
      */
     function enableProofOfReserve() external override onlyOwner {
         require(chainReserveFeed != address(0), "TrueCurrency: chainReserveFeed not set");
-        emit ProofOfReserveEnabled();
         proofOfReserveEnabled = true;
+        emit ProofOfReserveEnabled();
     }
 }

packages/contracts-por/contracts/common/BurnableTokenWithBounds.sol

@@ -52,7 +52,7 @@ abstract contract BurnableTokenWithBounds is ReclaimerToken {
      * @param _min minimum amount that can be burned at once
      * @param _max maximum amount that can be burned at once
      */
-    function setBurnBounds(uint256 _min, uint256 _max) external onlyOwner {
+    function setBurnBounds(uint256 _min, uint256 _max) override external onlyOwner {
         require(_min <= _max, "BurnableTokenWithBounds: min > max");
         burnMin = _min;
         burnMax = _max;

packages/contracts-por/contracts/common/ReclaimerToken.sol

@@ -2,20 +2,20 @@
 pragma solidity 0.6.10;
 
 import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
-
+import {ITrueCurrency} from "../interface/ITrueCurrency.sol";
 import {ERC20} from "./ERC20.sol";
 
 /**
  * @title ReclaimerToken
  * @dev ERC20 token which allows owner to reclaim ERC20 tokens
  * or ether sent to this contract
  */
-abstract contract ReclaimerToken is ERC20 {
+abstract contract ReclaimerToken is ERC20, ITrueCurrency {
     /**
      * @dev send all eth balance in the contract to another address
      * @param _to address to send eth balance to
      */
-    function reclaimEther(address payable _to) external onlyOwner {
+    function reclaimEther(address payable _to) override external onlyOwner {
         _to.transfer(address(this).balance);
     }
 
@@ -25,7 +25,7 @@ abstract contract ReclaimerToken is ERC20 {
      * @param token token to reclaim
      * @param _to address to send eth balance to
      */
-    function reclaimToken(IERC20 token, address _to) external onlyOwner {
+    function reclaimToken(IERC20 token, address _to) override external onlyOwner {
         uint256 balance = token.balanceOf(address(this));
         token.transfer(_to, balance);
     }

packages/contracts-por/contracts/interface/IOwnedUpgradeabilityProxy.sol

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 pragma solidity 0.6.10;
 
 interface IOwnedUpgradeabilityProxy {

packages/contracts-por/contracts/interface/IPoRToken.sol

@@ -2,6 +2,18 @@
 pragma solidity 0.6.10;
 
 interface IPoRToken {
+    /*** Admin Functions ***/
+
+    function setChainReserveFeed(address newFeed) external;
+
+    function setChainReserveHeartbeat(uint256 newHeartbeat) external;
+
+    function enableProofOfReserve() external;
+
+    function disableProofOfReserve() external;
+
+    /*** Events ***/
+
     /**
      * @notice Event emitted when the feed is updated
      */
@@ -21,14 +33,4 @@ interface IPoRToken {
      * @notice Event emitted when Proof of Reserve is disabled
      */
     event ProofOfReserveDisabled();
-
-    /*** Admin Functions ***/
-
-    function setChainReserveFeed(address newFeed) external;
-
-    function setChainReserveHeartbeat(uint256 newHeartbeat) external;
-
-    function enableProofOfReserve() external;
-
-    function disableProofOfReserve() external;
 }

packages/contracts-por/contracts/interface/IRegistry.sol

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 pragma solidity 0.6.10;
 
 interface IRegistry {

packages/contracts-por/contracts/interface/ITrueCurrency.sol

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 pragma solidity 0.6.10;
 
 import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
@@ -9,8 +10,6 @@ interface ITrueCurrency {
 
     function setBurnBounds(uint256 _min, uint256 _max) external;
 
-    function refundGas(uint256 amount) external;
-
     function reclaimEther(address payable _to) external;
 
     function reclaimToken(IERC20 token, address _to) external;