operator role

contracts/MerkleTreeWithHistory.sol

@@ -1,3 +1,14 @@
+// https://tornado.cash
+/*
+* d888888P                                           dP              a88888b.                   dP
+*    88                                              88             d8'   `88                   88
+*    88    .d8888b. 88d888b. 88d888b. .d8888b. .d888b88 .d8888b.    88        .d8888b. .d8888b. 88d888b.
+*    88    88'  `88 88'  `88 88'  `88 88'  `88 88'  `88 88'  `88    88        88'  `88 Y8ooooo. 88'  `88
+*    88    88.  .88 88       88    88 88.  .88 88.  .88 88.  .88 dP Y8.   .88 88.  .88       88 88    88
+*    dP    `88888P' dP       dP    dP `88888P8 `88888P8 `88888P' 88  Y88888P' `88888P8 `88888P' dP    dP
+* ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
+*/
+
 pragma solidity ^0.5.8;
 
 library MiMC {

contracts/Mixer.sol

@@ -1,3 +1,14 @@
+// https://tornado.cash
+/*
+* d888888P                                           dP              a88888b.                   dP
+*    88                                              88             d8'   `88                   88
+*    88    .d8888b. 88d888b. 88d888b. .d8888b. .d888b88 .d8888b.    88        .d8888b. .d8888b. 88d888b.
+*    88    88'  `88 88'  `88 88'  `88 88'  `88 88'  `88 88'  `88    88        88'  `88 Y8ooooo. 88'  `88
+*    88    88.  .88 88       88    88 88.  .88 88.  .88 88.  .88 dP Y8.   .88 88.  .88       88 88    88
+*    dP    `88888P' dP       dP    dP `88888P8 `88888P8 `88888P' 88  Y88888P' `88888P8 `88888P' dP    dP
+* ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
+*/
+
 pragma solidity ^0.5.8;
 
 import "./MerkleTreeWithHistory.sol";
@@ -9,7 +20,9 @@ contract IVerifier {
 contract Mixer is MerkleTreeWithHistory {
   uint256 public transferValue;
   bool public isDepositsEnabled = true;
-  address public pauseAccount;
+  // operator can disable new deposits in case of emergency
+  // it also receives a relayer fee
+  address payable public operator;
   mapping(uint256 => bool) public nullifierHashes;
   // we store all commitments just to prevent accidental deposits with the same commitment
   mapping(uint256 => bool) public commitments;
@@ -28,11 +41,11 @@ contract Mixer is MerkleTreeWithHistory {
     uint256 _transferValue,
     uint8 _merkleTreeHeight,
     uint256 _emptyElement,
-    address _pauseAccount
+    address payable _operator
   ) MerkleTreeWithHistory(_merkleTreeHeight, _emptyElement) public {
     verifier = IVerifier(_verifier);
     transferValue = _transferValue;
-    pauseAccount = _pauseAccount;
+    operator = _operator;
   }
 
   /**
@@ -62,27 +75,27 @@ contract Mixer is MerkleTreeWithHistory {
     address payable receiver = address(input[2]);
     uint256 fee = input[3];
 
-    require(fee < transferValue, "Fee exceeds transfer value");
     require(!nullifierHashes[nullifierHash], "The note has been already spent");
+    require(fee < transferValue, "Fee exceeds transfer value");
     require(isKnownRoot(root), "Cannot find your merkle root"); // Make sure to use a recent one
     require(verifier.verifyProof(a, b, c, input), "Invalid withdraw proof");
 
     nullifierHashes[nullifierHash] = true;
     receiver.transfer(transferValue - fee);
     if (fee > 0) {
-      msg.sender.transfer(fee);
+      operator.transfer(fee);
     }
     emit Withdraw(receiver, nullifierHash, fee);
   }
 
   function toggleDeposits() external {
-    require(msg.sender == pauseAccount, "unauthorized");
+    require(msg.sender == operator, "unauthorized");
     isDepositsEnabled = !isDepositsEnabled;
   }
 
-  function setPauseAccount(address _newAccount) external {
+  function changeOperator(address payable _newAccount) external {
-    require(msg.sender == pauseAccount, "unauthorized");
+    require(msg.sender == operator, "unauthorized");
-    pauseAccount = _newAccount;
+    operator = _newAccount;
   }
 
   function isSpent(uint256 nullifier) public view returns(bool) {

test/Mixer.test.js

@@ -60,6 +60,7 @@ function snarkVerify(proof) {
 contract('Mixer', accounts => {
   let mixer
   const sender = accounts[0]
+  const operator = accounts[0]
   const levels = MERKLE_TREE_HEIGHT || 16
   const zeroValue = EMPTY_ELEMENT || 1337
   const value = AMOUNT || '1000000000000000000' // 1 ether
@@ -211,6 +212,7 @@ contract('Mixer', accounts => {
 
       const balanceMixerBefore = await web3.eth.getBalance(mixer.address)
       const balanceRelayerBefore = await web3.eth.getBalance(relayer)
+      const balanceOperatorBefore = await web3.eth.getBalance(operator)
       const balanceRecieverBefore = await web3.eth.getBalance(toHex(receiver.toString()))
       let isSpent = await mixer.isSpent(input.nullifierHash.toString(16).padStart(66, '0x00000'))
       isSpent.should.be.equal(false)
@@ -222,10 +224,12 @@ contract('Mixer', accounts => {
 
       const balanceMixerAfter = await web3.eth.getBalance(mixer.address)
       const balanceRelayerAfter = await web3.eth.getBalance(relayer)
+      const balanceOperatorAfter = await web3.eth.getBalance(operator)
       const balanceRecieverAfter = await web3.eth.getBalance(toHex(receiver.toString()))
       const feeBN = toBN(fee.toString())
       balanceMixerAfter.should.be.eq.BN(toBN(balanceMixerBefore).sub(toBN(value)))
-      balanceRelayerAfter.should.be.eq.BN(toBN(balanceRelayerBefore).add(feeBN))
+      balanceRelayerAfter.should.be.eq.BN(toBN(balanceRelayerBefore))
+      balanceOperatorAfter.should.be.eq.BN(toBN(balanceOperatorBefore).add(feeBN))
       balanceRecieverAfter.should.be.eq.BN(toBN(balanceRecieverBefore).add(toBN(value)).sub(feeBN))
 
 
@@ -386,6 +390,29 @@ contract('Mixer', accounts => {
     })
   })
 
+  describe('#changeOperator', () => {
+    it('should work', async () => {
+      let operator = await mixer.operator()
+      operator.should.be.equal(sender)
+
+      const newOperator = accounts[7]
+      await mixer.changeOperator(newOperator).should.be.fulfilled
+
+      operator = await mixer.operator()
+      operator.should.be.equal(newOperator)
+    })
+
+    it('cannot change from different address', async () => {
+      let operator = await mixer.operator()
+      operator.should.be.equal(sender)
+
+      const newOperator = accounts[7]
+      const error = await mixer.changeOperator(newOperator, { from:  accounts[7] }).should.be.rejected
+      error.reason.should.be.equal('unauthorized')
+
+    })
+  })
+
   afterEach(async () => {
     await revertSnapshot(snapshotId.result)
     // eslint-disable-next-line require-atomic-updates

truffle-config.js

@@ -55,7 +55,7 @@ module.exports = {
       provider: () => new HDWalletProvider(process.env.PRIVATE_KEY, 'https://mainnet.infura.io/v3/c7463beadf2144e68646ff049917b716'),
       network_id: 1,
       gas: 5000000,
-      gasPrice: utils.toWei('2', 'gwei'),
+      gasPrice: utils.toWei('3.1', 'gwei'),
       // confirmations: 0,
       // timeoutBlocks: 200,
       skipDryRun: true