Cached safety checking alternative

contracts/optimistic-ethereum/OVM/execution/OVM_ExecutionManager.sol

@@ -3,20 +3,23 @@
 pragma solidity >0.5.0 <0.8.0;
 pragma experimental ABIEncoderV2;
 
+
 /* Library Imports */
 import { Lib_OVMCodec } from "../../libraries/codec/Lib_OVMCodec.sol";
 import { Lib_AddressResolver } from "../../libraries/resolver/Lib_AddressResolver.sol";
 import { Lib_EthUtils } from "../../libraries/utils/Lib_EthUtils.sol";
 
-/* Interface Imports */
+/* Inherited Interface Imports */
 import { iOVM_ExecutionManager } from "../../iOVM/execution/iOVM_ExecutionManager.sol";
+
+/* External Interface Imports */
 import { iOVM_StateManager } from "../../iOVM/execution/iOVM_StateManager.sol";
+import { iOVM_SafetyCache } from "../../iOVM/execution/iOVM_SafetyCache.sol";
 import { iOVM_SafetyChecker } from "../../iOVM/execution/iOVM_SafetyChecker.sol";
 
 /* Contract Imports */
 import { OVM_ECDSAContractAccount } from "../accounts/OVM_ECDSAContractAccount.sol";
 import { OVM_ProxyEOA } from "../accounts/OVM_ProxyEOA.sol";
-import { OVM_DeployerWhitelist } from "../precompiles/OVM_DeployerWhitelist.sol";
 
 /**
  * @title OVM_ExecutionManager
@@ -39,7 +42,7 @@ contract OVM_ExecutionManager is iOVM_ExecutionManager, Lib_AddressResolver {
      * External Contract References *
      ********************************/
 
-    iOVM_SafetyChecker internal ovmSafetyChecker;
+    iOVM_SafetyCache internal ovmSafetyCache;
     iOVM_StateManager internal ovmStateManager;
 
 
@@ -81,7 +84,7 @@ contract OVM_ExecutionManager is iOVM_ExecutionManager, Lib_AddressResolver {
     )
         Lib_AddressResolver(_libAddressManager)
     {
-        ovmSafetyChecker = iOVM_SafetyChecker(resolve("OVM_SafetyChecker"));
+        ovmSafetyCache = iOVM_SafetyCache(resolve("OVM_SafetyCache"));
         gasMeterConfig = _gasMeterConfig;
         globalContext = _globalContext;
         _resetContext();
@@ -808,8 +811,15 @@ contract OVM_ExecutionManager is iOVM_ExecutionManager, Lib_AddressResolver {
             _revertWithFlag(RevertFlag.CREATE_COLLISION);
         }
 
-        // Check the creation bytecode against the OVM_SafetyChecker.
-        if (ovmSafetyChecker.isBytecodeSafe(_bytecode) == false) {
+        bytes32 codehash = keccak256(abi.encode(_bytecode));
+        // check if codehash is registered as safe in the cache
+        bool safe = ovmSafetyCache.isRegisteredSafeBytecode(codehash);
+        if (safe == false) {
+            // If not safe, try to register it.
+            safe = ovmSafetyCache.checkAndRegisterSafeBytecode(_bytecode);
+        }
+        // Check status of safe one more time.
+        if (safe == false) {
             _revertWithFlag(RevertFlag.UNSAFE_BYTECODE);
         }
 
@@ -840,7 +850,16 @@ contract OVM_ExecutionManager is iOVM_ExecutionManager, Lib_AddressResolver {
         // Again simply checking that the deployed code is safe too. Contracts can generate
         // arbitrary deployment code, so there's no easy way to analyze this beforehand.
         bytes memory deployedCode = Lib_EthUtils.getCode(ethAddress);
-        if (ovmSafetyChecker.isBytecodeSafe(deployedCode) == false) {
+
+        bytes32 deployedCodehash = keccak256(abi.encode(deployedCode));
+        // check if codehash is registered as safe in the cache
+        bool deployedSafe = ovmSafetyCache.isRegisteredSafeBytecode(deployedCodehash);
+        if (deployedSafe == false) {
+            // If not safe, try to register it.
+            deployedSafe = ovmSafetyCache.checkAndRegisterSafeBytecode(deployedCode);
+        }
+        // Check status of safe one more time.
+        if (deployedSafe == false) {
             _revertWithFlag(RevertFlag.UNSAFE_BYTECODE);
         }
 
@@ -870,7 +889,7 @@ contract OVM_ExecutionManager is iOVM_ExecutionManager, Lib_AddressResolver {
     }
 
     /********************************************
-     * Public Functions: Deployment Witelisting *
+     * Internal Functions: Deployment Witelisting *
      ********************************************/
 
     /**
@@ -1095,23 +1114,6 @@ contract OVM_ExecutionManager is iOVM_ExecutionManager, Lib_AddressResolver {
      * Internal Functions: State Manipulation *
      ******************************************/
 
-    /**
-     * Checks whether an account exists within the OVM_StateManager.
-     * @param _address Address of the account to check.
-     * @return _exists Whether or not the account exists.
-     */
-    function _hasAccount(
-        address _address
-    )
-        internal
-        returns (
-            bool _exists
-        )
-    {
-        _checkAccountLoad(_address);
-        return ovmStateManager.hasAccount(_address);
-    }
-
     /**
      * Checks whether a known empty account exists within the OVM_StateManager.
      * @param _address Address of the account to check.

contracts/optimistic-ethereum/OVM/execution/OVM_SafetyCache.sol

@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >0.5.0 <0.8.0;
+
+/* Library Imports */
+import { Lib_AddressResolver } from "../../libraries/resolver/Lib_AddressResolver.sol";
+
+/* External Interface Imports */ 
+import { iOVM_SafetyCache } from "../../iOVM/execution/iOVM_SafetyCache.sol";
+
+/* Inherited Interface Imports */
+import { iOVM_SafetyChecker } from "../../iOVM/execution/iOVM_SafetyChecker.sol";
+
+/**
+ * @title OVM_SafetyCache
+ * @dev This contract implements a simple registry for caching the hash of any bytecode strings which have
+ * already been confirmed safe by the Safety Checker. 
+ *
+ * Compiler used: solc
+ * Runtime target: EVM
+ */
+contract OVM_SafetyCache is iOVM_SafetyCache, Lib_AddressResolver {
+
+
+    /*******************************************
+     * Contract Variables: Contract References *
+     ******************************************/
+
+    iOVM_SafetyChecker internal ovmSafetyChecker;
+
+
+    /****************************************
+     * Contract Variables: Internal Storage *
+     ****************************************/
+
+    mapping(bytes32 => bool) internal isSafeCodehash;
+
+
+    /***************
+     * Constructor *
+     ***************/
+
+    /**
+     * @param _libAddressManager Address of the Address Manager.
+     */
+    constructor(
+        address _libAddressManager
+    )
+        Lib_AddressResolver(_libAddressManager)
+    {
+        ovmSafetyChecker = iOVM_SafetyChecker(resolve("OVM_SafetyChecker"));
+    }
+
+
+    /**********************
+     * External Functions *
+     *********************/
+
+
+    /** Checks the registry to see if the verified bytecode is registered as safe. If not, calls to the 
+    * SafetyChecker to see. 
+    * @param _code A bytes32 hash of the code
+    * @return `true` if the bytecode is safe, `false` otherwise.
+    */
+    function checkAndRegisterSafeBytecode(
+        bytes memory _code
+    ) 
+        override
+        external
+        returns (
+            bool
+    ) {
+        bytes32 codehash = keccak256(abi.encode(_code));
+        if(isSafeCodehash[codehash] == true) {
+            return true;
+        }
+
+        bool safe = ovmSafetyChecker.isBytecodeSafe(_code);
+        if(safe) {
+            isSafeCodehash[codehash] = true;
+        }
+        return safe;
+    }
+
+    /** Used to check if bytecode has already been recorded as safe.
+    * @param _codehash A bytes32 hash of the code
+    */
+    function isRegisteredSafeBytecode(
+        bytes32 _codehash
+    ) 
+        override
+        external
+        view
+        returns (
+            bool
+        )
+    {
+        return isSafeCodehash[_codehash] == true;
+    }
+}

contracts/optimistic-ethereum/OVM/execution/OVM_SafetyChecker.sol

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 pragma solidity >0.5.0 <0.8.0;
 
-/* Interface Imports */
+/* Inherited Interface Imports */
 import { iOVM_SafetyChecker } from "../../iOVM/execution/iOVM_SafetyChecker.sol";
 
 /**

contracts/optimistic-ethereum/iOVM/execution/iOVM_SafetyCache.sol

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >0.5.0 <0.8.0;
+
+/**
+ * @title iOVM_SafetyCache
+ */
+interface iOVM_SafetyCache {
+
+    /*********************
+    * External Functions *
+    **********************/
+    function checkAndRegisterSafeBytecode(bytes memory _code) external returns (bool);
+
+    function isRegisteredSafeBytecode(bytes32 _codehash) external view returns (bool);
+
+}

contracts/optimistic-ethereum/iOVM/execution/iOVM_SafetyChecker.sol

@@ -10,5 +10,5 @@ interface iOVM_SafetyChecker {
      * Public Functions *
      ********************/
 
-    function isBytecodeSafe(bytes calldata _bytecode) external pure returns (bool);
+    function isBytecodeSafe(bytes calldata _bytecode) external returns (bool);
 }