vm: add code generation options

Adds options to a VM Context to disable code generation from strings
(such as eval or new Function) and WASM code generation
(WebAssembly.compile).

PR-URL: #19016
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

Author: devsnek

doc/api/vm.md

@@ -495,6 +495,14 @@ added: v0.3.1
     value of the [`url.origin`][] property of a [`URL`][] object. Most notably,
     this string should omit the trailing slash, as that denotes a path.
     **Default:** `''`.
+  * `contextCodeGeneration` {Object}
+    * `strings` {boolean} If set to false any calls to `eval` or function
+      constructors (`Function`, `GeneratorFunction`, etc) will throw an
+      `EvalError`.
+      **Default**: `true`.
+    * `wasm` {boolean} If set to false any attempt to compile a WebAssembly
+      module will throw a `WebAssembly.CompileError`.
+      **Default**: `true`.
 
 First contextifies the given `sandbox`, runs the compiled code contained by
 the `vm.Script` object within the created sandbox, and returns the result.
@@ -578,6 +586,14 @@ added: v0.3.1
     the [`url.origin`][] property of a [`URL`][] object. Most notably, this
     string should omit the trailing slash, as that denotes a path.
     **Default:** `''`.
+  * `codeGeneration` {Object}
+    * `strings` {boolean} If set to false any calls to `eval` or function
+      constructors (`Function`, `GeneratorFunction`, etc) will throw an
+      `EvalError`.
+      **Default**: `true`.
+    * `wasm` {boolean} If set to false any attempt to compile a WebAssembly
+      module will throw a `WebAssembly.CompileError`.
+      **Default**: `true`.
 
 If given a `sandbox` object, the `vm.createContext()` method will [prepare
 that sandbox][contextified] so that it can be used in calls to

lib/vm.js

@@ -84,14 +84,36 @@ function validateString(prop, propName) {
     throw new ERR_INVALID_ARG_TYPE(propName, 'string', prop);
 }
 
+function validateBool(prop, propName) {
+  if (prop !== undefined && typeof prop !== 'boolean')
+    throw new ERR_INVALID_ARG_TYPE(propName, 'boolean', prop);
+}
+
+function validateObject(prop, propName) {
+  if (prop !== undefined && (typeof prop !== 'object' || prop === null))
+    throw new ERR_INVALID_ARG_TYPE(propName, 'Object', prop);
+}
+
 function getContextOptions(options) {
   if (options) {
+    validateObject(options.contextCodeGeneration,
+                   'options.contextCodeGeneration');
     const contextOptions = {
       name: options.contextName,
-      origin: options.contextOrigin
+      origin: options.contextOrigin,
+      codeGeneration: typeof options.contextCodeGeneration === 'object' ? {
+        strings: options.contextCodeGeneration.strings,
+        wasm: options.contextCodeGeneration.wasm,
+      } : undefined,
     };
     validateString(contextOptions.name, 'options.contextName');
     validateString(contextOptions.origin, 'options.contextOrigin');
+    if (contextOptions.codeGeneration) {
+      validateBool(contextOptions.codeGeneration.strings,
+                   'options.contextCodeGeneration.strings');
+      validateBool(contextOptions.codeGeneration.wasm,
+                   'options.contextCodeGeneration.wasm');
+    }
     return contextOptions;
   }
   return {};
@@ -109,10 +131,21 @@ function createContext(sandbox, options) {
     if (typeof options !== 'object' || options === null) {
       throw new ERR_INVALID_ARG_TYPE('options', 'object', options);
     }
+    validateObject(options.codeGeneration, 'options.codeGeneration');
     options = {
       name: options.name,
-      origin: options.origin
+      origin: options.origin,
+      codeGeneration: typeof options.codeGeneration === 'object' ? {
+        strings: options.codeGeneration.strings,
+        wasm: options.codeGeneration.wasm,
+      } : undefined,
     };
+    if (options.codeGeneration !== undefined) {
+      validateBool(options.codeGeneration.strings,
+                   'options.codeGeneration.strings');
+      validateBool(options.codeGeneration.wasm,
+                   'options.codeGeneration.wasm');
+    }
     if (options.name === undefined) {
       options.name = `VM Context ${defaultContextNameIndex++}`;
     } else if (typeof options.name !== 'string') {

src/node.cc

@@ -28,6 +28,7 @@
 #include "node_revert.h"
 #include "node_debug_options.h"
 #include "node_perf.h"
+#include "node_context_data.h"
 
 #if defined HAVE_PERFCTR
 #include "node_counters.h"
@@ -4432,6 +4433,8 @@ Local<Context> NewContext(Isolate* isolate,
   HandleScope handle_scope(isolate);
   auto intl_key = FIXED_ONE_BYTE_STRING(isolate, "Intl");
   auto break_iter_key = FIXED_ONE_BYTE_STRING(isolate, "v8BreakIterator");
+  context->SetEmbedderData(
+      ContextEmbedderIndex::kAllowWasmCodeGeneration, True(isolate));
   Local<Value> intl_v;
   if (context->Global()->Get(context, intl_key).ToLocal(&intl_v) &&
       intl_v->IsObject()) {
@@ -4509,6 +4512,13 @@ inline int Start(Isolate* isolate, IsolateData* isolate_data,
   return exit_code;
 }
 
+bool AllowWasmCodeGenerationCallback(
+    Local<Context> context, Local<String>) {
+  Local<Value> wasm_code_gen =
+    context->GetEmbedderData(ContextEmbedderIndex::kAllowWasmCodeGeneration);
+  return wasm_code_gen->IsUndefined() || wasm_code_gen->IsTrue();
+}
+
 inline int Start(uv_loop_t* event_loop,
                  int argc, const char* const* argv,
                  int exec_argc, const char* const* exec_argv) {
@@ -4527,6 +4537,7 @@ inline int Start(uv_loop_t* event_loop,
   isolate->SetAbortOnUncaughtExceptionCallback(ShouldAbortOnUncaughtException);
   isolate->SetMicrotasksPolicy(v8::MicrotasksPolicy::kExplicit);
   isolate->SetFatalErrorHandler(OnFatalError);
+  isolate->SetAllowWasmCodeGenerationCallback(AllowWasmCodeGenerationCallback);
 
   {
     Mutex::ScopedLock scoped_lock(node_isolate_mutex);

src/node_context_data.h

@@ -15,9 +15,14 @@ namespace node {
 #define NODE_CONTEXT_SANDBOX_OBJECT_INDEX 33
 #endif
 
+#ifndef NODE_CONTEXT_ALLOW_WASM_CODE_GENERATION_INDEX
+#define NODE_CONTEXT_ALLOW_WASM_CODE_GENERATION_INDEX 34
+#endif
+
 enum ContextEmbedderIndex {
   kEnvironment = NODE_CONTEXT_EMBEDDER_DATA_INDEX,
   kSandboxObject = NODE_CONTEXT_SANDBOX_OBJECT_INDEX,
+  kAllowWasmCodeGeneration = NODE_CONTEXT_ALLOW_WASM_CODE_GENERATION_INDEX,
 };
 
 }  // namespace node

src/node_contextify.cc

@@ -185,6 +185,30 @@ Local<Context> ContextifyContext::CreateV8Context(
   CHECK(name->IsString());
   Utf8Value name_val(env->isolate(), name);
 
+  Local<Value> codegen = options_obj->Get(env->context(),
+      FIXED_ONE_BYTE_STRING(env->isolate(), "codeGeneration"))
+          .ToLocalChecked();
+
+  if (!codegen->IsUndefined()) {
+    CHECK(codegen->IsObject());
+    Local<Object> codegen_obj = codegen.As<Object>();
+
+    Local<Value> allow_code_gen_from_strings =
+      codegen_obj->Get(env->context(),
+          FIXED_ONE_BYTE_STRING(env->isolate(), "strings"))
+      .ToLocalChecked();
+    ctx->AllowCodeGenerationFromStrings(
+        allow_code_gen_from_strings->IsUndefined() ||
+            allow_code_gen_from_strings->IsTrue());
+
+    Local<Value> allow_wasm_code_gen = codegen_obj->Get(env->context(),
+        FIXED_ONE_BYTE_STRING(env->isolate(), "wasm"))
+      .ToLocalChecked();
+    ctx->SetEmbedderData(ContextEmbedderIndex::kAllowWasmCodeGeneration,
+        Boolean::New(env->isolate(), allow_wasm_code_gen->IsUndefined() ||
+            allow_wasm_code_gen->IsTrue()));
+  }
+
   ContextInfo info(*name_val);
 
   Local<Value> origin =

src/node_contextify.h

@@ -24,6 +24,9 @@ class ContextifyContext {
       v8::Local<v8::Object> sandbox_obj, v8::Local<v8::Object> options_obj);
   static void Init(Environment* env, v8::Local<v8::Object> target);
 
+  static bool AllowWasmCodeGeneration(
+      v8::Local<v8::Context> context, v8::Local<v8::String>);
+
   static ContextifyContext* ContextFromContextifiedSandbox(
       Environment* env,
       const v8::Local<v8::Object>& sandbox);

test/parallel/test-vm-codegen.js

@@ -0,0 +1,110 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+
+const { createContext, runInContext, runInNewContext } = require('vm');
+
+const WASM_BYTES = Buffer.from(
+  [0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00]);
+
+
+function expectsError(fn, type) {
+  try {
+    fn();
+    assert.fail('expected fn to error');
+  } catch (err) {
+    if (typeof type === 'string')
+      assert.strictEqual(err.name, type);
+    else
+      assert(err instanceof type);
+  }
+}
+
+{
+  const ctx = createContext({ WASM_BYTES });
+  const test = 'eval(""); new WebAssembly.Module(WASM_BYTES);';
+  runInContext(test, ctx);
+
+  runInNewContext(test, { WASM_BYTES }, {
+    contextCodeGeneration: undefined,
+  });
+}
+
+{
+  const ctx = createContext({}, {
+    codeGeneration: {
+      strings: false,
+    },
+  });
+
+  const EvalError = runInContext('EvalError', ctx);
+  expectsError(() => {
+    runInContext('eval("x")', ctx);
+  }, EvalError);
+}
+
+{
+  const ctx = createContext({ WASM_BYTES }, {
+    codeGeneration: {
+      wasm: false,
+    },
+  });
+
+  const CompileError = runInContext('WebAssembly.CompileError', ctx);
+  expectsError(() => {
+    runInContext('new WebAssembly.Module(WASM_BYTES)', ctx);
+  }, CompileError);
+}
+
+expectsError(() => {
+  runInNewContext('eval("x")', {}, {
+    contextCodeGeneration: {
+      strings: false,
+    },
+  });
+}, 'EvalError');
+
+expectsError(() => {
+  runInNewContext('new WebAssembly.Module(WASM_BYTES)', { WASM_BYTES }, {
+    contextCodeGeneration: {
+      wasm: false,
+    },
+  });
+}, 'CompileError');
+
+common.expectsError(() => {
+  createContext({}, {
+    codeGeneration: {
+      strings: 0,
+    },
+  });
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+});
+
+common.expectsError(() => {
+  runInNewContext('eval("x")', {}, {
+    contextCodeGeneration: {
+      wasm: 1,
+    },
+  });
+}, {
+  code: 'ERR_INVALID_ARG_TYPE'
+});
+
+common.expectsError(() => {
+  createContext({}, {
+    codeGeneration: 1,
+  });
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+});
+
+common.expectsError(() => {
+  createContext({}, {
+    codeGeneration: null,
+  });
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+});