Kill switch: Polish and integrate MVP version

contracts/acl/ACLSyntaxSugar.sol

@@ -18,14 +18,42 @@ contract ACLSyntaxSugar {
         return arr(uint256(_a), uint256(_b));
     }
 
+    function arr(bytes32 _a, address _b) internal pure returns (uint256[] r) {
+        return arr(uint256(_a), uint256(_b));
+    }
+
+    function arr(bytes32 _a, address _b, address _c) internal pure returns (uint256[] r) {
+        return arr(uint256(_a), uint256(_b), uint256(_c));
+    }
+
+    function arr(bytes32 _a, uint256 _b) internal pure returns (uint256[] r) {
+        return arr(uint256(_a), _b);
+    }
+
+    function arr(bytes32 _a, uint256 _b, uint256 _c) internal pure returns (uint256[] r) {
+        return arr(uint256(_a), _b, _c);
+    }
+
     function arr(address _a) internal pure returns (uint256[] r) {
         return arr(uint256(_a));
     }
 
+    function arr(address _a, bool _b) internal pure returns (uint256[] r) {
+        return arr(uint256(_a), _toUint(_b));
+    }
+
+    function arr(address _a, bool _b, bool _c) internal pure returns (uint256[] r) {
+        return arr(uint256(_a), _toUint(_b), _toUint(_c));
+    }
+
     function arr(address _a, address _b) internal pure returns (uint256[] r) {
         return arr(uint256(_a), uint256(_b));
     }
 
+    function arr(address _a, uint256 _b) internal pure returns (uint256[] r) {
+        return arr(uint256(_a), _b);
+    }
+
     function arr(address _a, uint256 _b, uint256 _c) internal pure returns (uint256[] r) {
         return arr(uint256(_a), _b, _c);
     }
@@ -34,10 +62,6 @@ contract ACLSyntaxSugar {
         return arr(uint256(_a), _b, _c, _d);
     }
 
-    function arr(address _a, uint256 _b) internal pure returns (uint256[] r) {
-        return arr(uint256(_a), uint256(_b));
-    }
-
     function arr(address _a, address _b, uint256 _c, uint256 _d, uint256 _e) internal pure returns (uint256[] r) {
         return arr(uint256(_a), uint256(_b), _c, _d, _e);
     }
@@ -84,6 +108,10 @@ contract ACLSyntaxSugar {
         r[3] = _d;
         r[4] = _e;
     }
+
+    function _toUint(bool _a) private pure returns (uint256) {
+        return _a ? uint256(1) : uint256(0);
+    }
 }
 
 

contracts/apps/AragonApp.sol

@@ -40,12 +40,8 @@ contract AragonApp is AppStorage, Autopetrified, VaultRecoverable, ReentrancyGua
     *         Always returns false if the app hasn't been initialized yet.
     */
     function canPerform(address _sender, bytes32 _role, uint256[] _params) public view returns (bool) {
-        if (!hasInitialized()) {
-            return false;
-        }
-
         IKernel linkedKernel = kernel();
-        if (address(linkedKernel) == address(0)) {
+        if (address(linkedKernel) == address(0) || !isCallEnabled()) {
             return false;
         }
 
@@ -57,6 +53,47 @@ contract AragonApp is AppStorage, Autopetrified, VaultRecoverable, ReentrancyGua
         );
     }
 
+    /**
+    * @dev Check whether a call to the current app can be executed or not based on the kill-switch settings
+    * @return Boolean indicating whether the call could be executed or not
+    */
+    function isCallEnabled() public view returns (bool) {
+        if (!hasInitialized()) {
+            return false;
+        }
+
+        IKernel _kernel = kernel();
+        bytes4 selector = _kernel.isAppDisabled.selector;
+        bytes memory isAppDisabledCalldata = abi.encodeWithSelector(selector, appId(), address(this));
+        bool success;
+        assembly {
+            success := staticcall(gas, _kernel, add(isAppDisabledCalldata, 0x20), mload(isAppDisabledCalldata), 0, 0)
+        }
+
+        // If the call to `kernel.isAppDisabled()` reverts (using an old or non-existent Kernel) we consider that
+        // there is no kill switch. Therefore, the the call can be executed.
+        if (!success) {
+            return true;
+        }
+
+        // If it does not revert, check if the returned value is 32-bytes length, otherwise return false
+        uint256 _outputLength;
+        assembly { _outputLength := returndatasize }
+        if (_outputLength != 32) {
+            return false;
+        }
+
+        // Forward returned value
+        bool _shouldDenyCall;
+        assembly {
+            let ptr := mload(0x40)        // get next free memory pointer
+            mstore(0x40, add(ptr, 0x20))  // set next free memory pointer
+            returndatacopy(ptr, 0, 0x20)  // copy call return value
+            _shouldDenyCall := mload(ptr) // read data
+        }
+        return !_shouldDenyCall;
+    }
+
     /**
     * @dev Get the recovery vault for the app
     * @return Recovery vault address for the app

contracts/factory/DAOFactory.sol

@@ -1,33 +1,48 @@
 pragma solidity 0.4.24;
 
+import "../acl/IACL.sol";
+import "../acl/ACL.sol";
 import "../kernel/IKernel.sol";
 import "../kernel/Kernel.sol";
 import "../kernel/KernelProxy.sol";
-
-import "../acl/IACL.sol";
-import "../acl/ACL.sol";
-
+import "../kill-switch/KillSwitch.sol";
+import "../kill-switch/IssuesRegistry.sol";
 import "./EVMScriptRegistryFactory.sol";
 
 
 contract DAOFactory {
+    string private constant ERROR_MISSING_BASE_KILL_SWITCH = "DF_MISSING_BASE_KILL_SWITCH";
+
     IKernel public baseKernel;
     IACL public baseACL;
+    KillSwitch public baseKillSwitch;
     EVMScriptRegistryFactory public regFactory;
 
     event DeployDAO(address dao);
-    event DeployEVMScriptRegistry(address reg);
+    event DeployKillSwitch(address killSwitch);
+    event DeployEVMScriptRegistry(address registry);
 
     /**
-    * @notice Create a new DAOFactory, creating DAOs with Kernels proxied to `_baseKernel`, ACLs proxied to `_baseACL`, and new EVMScriptRegistries created from `_regFactory`.
+    * @notice Create a new DAOFactory, creating DAOs with Kernels proxied to `_baseKernel`, ACLs proxied to `_baseACL`, and new EVMScriptRegistries created from `_scriptsRegistryFactory`.
     * @param _baseKernel Base Kernel
     * @param _baseACL Base ACL
-    * @param _regFactory EVMScriptRegistry factory
+    * @param _baseKillSwitch Base KillSwitch
+    * @param _scriptsRegistryFactory EVMScriptRegistry factory
     */
-    constructor(IKernel _baseKernel, IACL _baseACL, EVMScriptRegistryFactory _regFactory) public {
+    constructor(
+        IKernel _baseKernel,
+        IACL _baseACL,
+        KillSwitch _baseKillSwitch,
+        EVMScriptRegistryFactory _scriptsRegistryFactory
+    )
+        public
+    {
         // No need to init as it cannot be killed by devops199
-        if (address(_regFactory) != address(0)) {
-            regFactory = _regFactory;
+        if (address(_scriptsRegistryFactory) != address(0)) {
+            regFactory = _scriptsRegistryFactory;
+        }
+        if (address(_baseKillSwitch) != address(0)) {
+            baseKillSwitch = _baseKillSwitch;
         }
 
         baseKernel = _baseKernel;
@@ -40,38 +55,106 @@ contract DAOFactory {
     * @return Newly created DAO
     */
     function newDAO(address _root) public returns (Kernel) {
-        Kernel dao = Kernel(new KernelProxy(baseKernel));
-
         if (address(regFactory) == address(0)) {
-            dao.initialize(baseACL, _root);
-        } else {
-            dao.initialize(baseACL, this);
+            return _createDAO(_root);
+        }
 
-            ACL acl = ACL(dao.acl());
-            bytes32 permRole = acl.CREATE_PERMISSIONS_ROLE();
-            bytes32 appManagerRole = dao.APP_MANAGER_ROLE();
+        Kernel dao = _createDAO(address(this));
+        ACL acl = ACL(dao.acl());
 
-            acl.grantPermission(regFactory, acl, permRole);
+        // load roles
+        bytes32 appManagerRole = dao.APP_MANAGER_ROLE();
+        bytes32 createPermissionsRole = acl.CREATE_PERMISSIONS_ROLE();
 
-            acl.createPermission(regFactory, dao, appManagerRole, this);
+        // grant app manager permissions to factory and deploy EVM scripts registry
+        acl.createPermission(regFactory, dao, appManagerRole, address(this));
+        _createEVMScriptRegistry(dao, acl, createPermissionsRole);
 
-            EVMScriptRegistry reg = regFactory.newEVMScriptRegistry(dao);
-            emit DeployEVMScriptRegistry(address(reg));
+        // roll back app manager permissions
+        acl.revokePermission(regFactory, dao, appManagerRole);
+        acl.removePermissionManager(dao, appManagerRole);
 
-            // Clean up permissions
-            // First, completely reset the APP_MANAGER_ROLE
-            acl.revokePermission(regFactory, dao, appManagerRole);
-            acl.removePermissionManager(dao, appManagerRole);
+        // transfer create permissions roles to root address
+        acl.revokePermission(address(this), acl, createPermissionsRole);
+        acl.grantPermission(_root, acl, createPermissionsRole);
+        acl.setPermissionManager(_root, acl, createPermissionsRole);
+
+        return dao;
+    }
+
+    /**
+    * @notice Create a new DAO with `_root` set as the initial admin and `_issuesRegistry` as the source of truth for kill-switch purposes
+    * @param _root Address that will be granted control to setup DAO permissions
+    * @param _issuesRegistry Address of the registry of issues that will be used to detect critical situations by the kill switch
+    * @return Newly created DAO
+    */
+    function newDAOWithKillSwitch(address _root, IssuesRegistry _issuesRegistry) public returns (Kernel) {
+        require(address(baseKillSwitch) != address(0), ERROR_MISSING_BASE_KILL_SWITCH);
 
-            // Then, make root the only holder and manager of CREATE_PERMISSIONS_ROLE
-            acl.revokePermission(regFactory, acl, permRole);
-            acl.revokePermission(this, acl, permRole);
-            acl.grantPermission(_root, acl, permRole);
-            acl.setPermissionManager(_root, acl, permRole);
+        Kernel dao = _createDAO(address(this));
+        ACL acl = ACL(dao.acl());
+
+        // load roles
+        bytes32 appManagerRole = dao.APP_MANAGER_ROLE();
+        bytes32 createPermissionsRole = acl.CREATE_PERMISSIONS_ROLE();
+
+        // grant app manager permissions to this and deploy kill switch
+        acl.createPermission(address(this), dao, appManagerRole, address(this));
+        _createKillSwitch(dao, acl, _issuesRegistry);
+
+        // deploy EVM scripts registry if required
+        if (address(regFactory) != address(0)) {
+            acl.grantPermission(regFactory, dao, appManagerRole);
+            _createEVMScriptRegistry(dao, acl, createPermissionsRole);
+            acl.revokePermission(regFactory, dao, appManagerRole);
         }
 
-        emit DeployDAO(address(dao));
+        // roll back app manager permissions
+        acl.revokePermission(address(this), dao, appManagerRole);
+        acl.removePermissionManager(dao, appManagerRole);
+
+        // transfer create permissions roles to root address
+        acl.revokePermission(address(this), acl, createPermissionsRole);
+        acl.grantPermission(_root, acl, createPermissionsRole);
+        acl.setPermissionManager(_root, acl, createPermissionsRole);
 
         return dao;
     }
+
+    function _createDAO(address _permissionsCreator) internal returns (Kernel) {
+        Kernel dao = Kernel(new KernelProxy(baseKernel));
+        dao.initialize(baseACL, _permissionsCreator);
+        emit DeployDAO(address(dao));
+        return dao;
+    }
+
+    function _createEVMScriptRegistry(Kernel _dao, ACL _acl, bytes32 _createPermissionsRole) internal {
+        _acl.grantPermission(regFactory, _acl, _createPermissionsRole);
+        EVMScriptRegistry scriptsRegistry = regFactory.newEVMScriptRegistry(_dao);
+        emit DeployEVMScriptRegistry(address(scriptsRegistry));
+        _acl.revokePermission(regFactory, _acl, _createPermissionsRole);
+    }
+
+    function _createKillSwitch(Kernel _dao, ACL _acl, IssuesRegistry _issuesRegistry) internal {
+        bytes32 killSwitchAppID = _dao.DEFAULT_KILL_SWITCH_APP_ID();
+        bytes memory initializeData = abi.encodeWithSelector(baseKillSwitch.initialize.selector, _issuesRegistry);
+        KillSwitch killSwitch = KillSwitch(_dao.newAppInstance(killSwitchAppID, baseKillSwitch, initializeData, true));
+        _allowKillSwitchCoreInstances(_dao, _acl, killSwitch);
+        emit DeployKillSwitch(address(killSwitch));
+    }
+
+    function _allowKillSwitchCoreInstances(Kernel _dao, ACL _acl, KillSwitch _killSwitch) internal {
+        // create change whitelisted instances role for this
+        bytes32 changeWhitelistedInstancesRole = _killSwitch.CHANGE_WHITELISTED_INSTANCES_ROLE();
+        _acl.createPermission(address(this), _killSwitch, changeWhitelistedInstancesRole, address(this));
+
+        // whitelist core instances: kill switch, acl and kernel
+        _killSwitch.setWhitelistedInstance(address(_dao), true);
+        _killSwitch.setWhitelistedInstance(address(_acl), true);
+        _killSwitch.setWhitelistedInstance(address(_killSwitch), true);
+
+        // revoke and remove change whitelisted instances role from this
+        _acl.revokePermission(address(this), _killSwitch, changeWhitelistedInstancesRole);
+        _acl.removePermissionManager(_killSwitch, changeWhitelistedInstancesRole);
+    }
 }

contracts/kernel/IKernel.sol

@@ -20,4 +20,5 @@ contract IKernel is IKernelEvents, IVaultRecoverable {
 
     function setApp(bytes32 namespace, bytes32 appId, address app) public;
     function getApp(bytes32 namespace, bytes32 appId) public view returns (address);
+    function isAppDisabled(bytes32 appId, address _instance) public view returns (bool);
 }

contracts/kernel/Kernel.sol

@@ -10,6 +10,7 @@ import "../common/IsContract.sol";
 import "../common/Petrifiable.sol";
 import "../common/VaultRecoverable.sol";
 import "../factory/AppProxyFactory.sol";
+import "../kill-switch/IKillSwitch.sol";
 import "../lib/misc/ERCProxy.sol";
 
 
@@ -20,9 +21,9 @@ contract Kernel is IKernel, KernelStorage, KernelAppIds, KernelNamespaceConstant
     */
     bytes32 public constant APP_MANAGER_ROLE = 0xb6d92708f3d4817afc106147d969e229ced5c46e65e0a5002a0d391287762bd0;
 
+    string private constant ERROR_AUTH_FAILED = "KERNEL_AUTH_FAILED";
     string private constant ERROR_APP_NOT_CONTRACT = "KERNEL_APP_NOT_CONTRACT";
     string private constant ERROR_INVALID_APP_CHANGE = "KERNEL_INVALID_APP_CHANGE";
-    string private constant ERROR_AUTH_FAILED = "KERNEL_AUTH_FAILED";
 
     /**
     * @dev Constructor that allows the deployer to choose if the base instance should be petrified immediately.
@@ -162,13 +163,30 @@ contract Kernel is IKernel, KernelStorage, KernelAppIds, KernelNamespaceConstant
         recoveryVaultAppId = _recoveryVaultAppId;
     }
 
+    /**
+    * @dev Tells whether a call to an instance of an app should be denied or not based on the kill-switch settings.
+    *      Initialization check is implicitly provided by the KillSwitch's existence, as apps can only be installed after initialization.
+    * @param _appId Identifier for app to be checked
+    * @return True if the given call should be denied, false otherwise
+    */
+    function isAppDisabled(bytes32 _appId, address _instance) public view returns (bool) {
+        IKillSwitch _killSwitch = killSwitch();
+        if (address(_killSwitch) == address(0)) {
+            return false;
+        }
+
+        address _baseApp = getApp(KERNEL_APP_BASES_NAMESPACE, _appId);
+        return _killSwitch.shouldDenyCallingApp(_appId, _baseApp, _instance);
+    }
+
     // External access to default app id and namespace constants to mimic default getters for constants
     /* solium-disable function-order, mixedcase */
     function CORE_NAMESPACE() external pure returns (bytes32) { return KERNEL_CORE_NAMESPACE; }
     function APP_BASES_NAMESPACE() external pure returns (bytes32) { return KERNEL_APP_BASES_NAMESPACE; }
     function APP_ADDR_NAMESPACE() external pure returns (bytes32) { return KERNEL_APP_ADDR_NAMESPACE; }
     function KERNEL_APP_ID() external pure returns (bytes32) { return KERNEL_CORE_APP_ID; }
     function DEFAULT_ACL_APP_ID() external pure returns (bytes32) { return KERNEL_DEFAULT_ACL_APP_ID; }
+    function DEFAULT_KILL_SWITCH_APP_ID() external pure returns (bytes32) { return KERNEL_DEFAULT_KILL_SWITCH_APP_ID; }
     /* solium-enable function-order, mixedcase */
 
     /**
@@ -190,13 +208,21 @@ contract Kernel is IKernel, KernelStorage, KernelAppIds, KernelNamespaceConstant
     }
 
     /**
-    * @dev Get the installed ACL app
+    * @dev Get the default ACL app
     * @return ACL app
     */
     function acl() public view returns (IACL) {
         return IACL(getApp(KERNEL_APP_ADDR_NAMESPACE, KERNEL_DEFAULT_ACL_APP_ID));
     }
 
+    /**
+    * @dev Get the default KillSwitch app
+    * @return KillSwitch app
+    */
+    function killSwitch() public view returns (IKillSwitch) {
+        return IKillSwitch(getApp(KERNEL_APP_ADDR_NAMESPACE, KERNEL_DEFAULT_KILL_SWITCH_APP_ID));
+    }
+
     /**
     * @dev Function called by apps to check ACL on kernel or to check permission status
     * @param _who Sender of the original call