Unlimited number of owners

.eslintrc

@@ -19,10 +19,10 @@
       "web3": false
     },
     "rules": {
-  
+
       // Strict mode
       "strict": [2, "global"],
-  
+
       // Code style
       "indent": [2, 4],
       "quotes": [2, "single"],
@@ -44,7 +44,7 @@
       "no-debugger": 0,
       "no-undef": 2,
       "object-curly-spacing": [2, "always"],
-      "max-len": [2, 120, 2],
+      "max-len": [2, 130, 2],
       "generator-star-spacing": ["error", "before"],
       "promise/avoid-new": 0,
       "promise/always-return": 0

contracts/Set.sol

@@ -0,0 +1,46 @@
+pragma solidity ^0.4.23;
+
+
+library Set {
+
+    struct Data {
+        bytes32[] items;
+        mapping(bytes32 => uint) lookup;
+    }
+
+    function length(Data storage s) internal view returns(uint) {
+        return s.items.length;
+    }
+
+    function at(Data storage s, uint index) internal view returns(bytes32) {
+        return s.items[index];
+    }
+
+    function contains(Data storage s, bytes32 item) internal view returns(bool) {
+        return s.lookup[item] != 0;
+    }
+
+    function add(Data storage s, bytes32 item) public returns(bool) {
+        if (s.lookup[item] > 0) {
+            return false;
+        }
+        s.lookup[item] = s.items.push(item);
+        return true;
+    }
+
+    function remove(Data storage s, bytes32 item) public returns(bool) {
+        uint index = s.lookup[item];
+        if (index == 0) {
+            return false;
+        }
+        if (index < s.items.length) {
+            bytes32 lastItem = s.items[s.items.length - 1];
+            s.items[index - 1] = lastItem;
+            s.lookup[lastItem] = index;
+        }
+        s.items.length -= 1;
+        delete s.lookup[item];
+        return true;
+    }
+
+}

migrations/2_deploy_contracts.js

@@ -1,5 +1,7 @@
 const Multiownable = artifacts.require('Multiownable');
+const Set = artifacts.require('Set');
 
-module.exports = function (deployer) {
+module.exports = async function (deployer) {
+    Multiownable.link('Set', (await Set.new()).address);
     deployer.deploy(Multiownable);
 };

test/MultiAttack.js

@@ -7,16 +7,22 @@ require('chai')
     .use(require('chai-bignumber')(web3.BigNumber))
     .should();
 
+const Set = artifacts.require('Set.sol');
 const MultiAttackable = artifacts.require('./impl/MultiAttackable.sol');
 const MultiAttacker = artifacts.require('./impl/MultiAttacker.sol');
 
 contract('MultiAttack', function ([_, wallet1, wallet2, wallet3, wallet4, wallet5]) {
+    before(async function () {
+        MultiAttackable.link('Set', (await Set.new()).address);
+    });
+
     it('should handle reentracy attack', async function () {
         const victim = await MultiAttackable.new();
         const hacker = await MultiAttacker.new();
 
         // Prepare victim wallet
-        await victim.transferOwnership([wallet1, wallet2]);
+        await victim.addOwners([wallet1, wallet2]);
+        await victim.resignOwnership({ from: _ });
         await web3.eth.sendTransaction({ from: _, to: victim.address, value: ether(3) });
 
         // Try reentrace attack