node_contextify.cc

// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

#include "node_internals.h"
#include "node_watchdog.h"
#include "base_object-inl.h"

namespace node {

using v8::Array;
using v8::ArrayBuffer;
using v8::Boolean;
using v8::Context;
using v8::EscapableHandleScope;
using v8::External;
using v8::Function;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::IndexedPropertyHandlerConfiguration;
using v8::Integer;
using v8::Just;
using v8::Local;
using v8::Maybe;
using v8::MaybeLocal;
using v8::Name;
using v8::NamedPropertyHandlerConfiguration;
using v8::Nothing;
using v8::Object;
using v8::ObjectTemplate;
using v8::Persistent;
using v8::PropertyAttribute;
using v8::PropertyCallbackInfo;
using v8::PropertyDescriptor;
using v8::Script;
using v8::ScriptCompiler;
using v8::ScriptOrigin;
using v8::String;
using v8::Symbol;
using v8::TryCatch;
using v8::Uint32;
using v8::Uint8Array;
using v8::UnboundScript;
using v8::Value;
using v8::WeakCallbackInfo;

// The vm module executes code in a sandboxed environment with a different
// global object than the rest of the code. This is achieved by applying
// every call that changes or queries a property on the global `this` in the
// sandboxed code, to the sandbox object.
//
// The implementation uses V8's interceptors for methods like `set`, `get`,
// `delete`, `defineProperty`, and for any query of the property attributes.
// Property handlers with interceptors are set on the object template for
// the sandboxed code. Handlers for both named properties and for indexed
// properties are used. Their functionality is almost identical, the indexed
// interceptors mostly just call the named interceptors.
//
// For every `get` of a global property in the sandboxed context, the
// interceptor callback checks the sandbox object for the property.
// If the property is defined on the sandbox, that result is returned to
// the original call instead of finishing the query on the global object.
//
// For every `set` of a global property, the interceptor callback defines or
// changes the property both on the sandbox and the global proxy.

namespace {

// Convert an int to a V8 Name (String or Symbol).
Local<Name> Uint32ToName(Local<Context> context, uint32_t index) {
  return Uint32::New(context->GetIsolate(), index)->ToString(context)
      .ToLocalChecked();
}

class ContextifyContext {
 protected:
  // V8 reserves the first field in context objects for the debugger. We use the
  // second field to hold a reference to the sandbox object.
  enum { kSandboxObjectIndex = 1 };

  Environment* const env_;
  Persistent<Context> context_;

 public:
  ContextifyContext(Environment* env, Local<Object> sandbox_obj) : env_(env) {
    Local<Context> v8_context = CreateV8Context(env, sandbox_obj);
    context_.Reset(env->isolate(), v8_context);

    // Allocation failure or maximum call stack size reached
    if (context_.IsEmpty())
      return;
    context_.SetWeak(this, WeakCallback, v8::WeakCallbackType::kParameter);
    context_.MarkIndependent();
  }


  ~ContextifyContext() {
    context_.Reset();
  }


  inline Environment* env() const {
    return env_;
  }


  inline Local<Context> context() const {
    return PersistentToLocal(env()->isolate(), context_);
  }


  inline Local<Object> global_proxy() const {
    return context()->Global();
  }


  inline Local<Object> sandbox() const {
    return Local<Object>::Cast(context()->GetEmbedderData(kSandboxObjectIndex));
  }

  // This is an object that just keeps an internal pointer to this
  // ContextifyContext.  It's passed to the NamedPropertyHandler.  If we
  // pass the main JavaScript context object we're embedded in, then the
  // NamedPropertyHandler will store a reference to it forever and keep it
  // from getting gc'd.
  Local<Value> CreateDataWrapper(Environment* env) {
    EscapableHandleScope scope(env->isolate());
    Local<Object> wrapper =
        env->script_data_constructor_function()
            ->NewInstance(env->context()).FromMaybe(Local<Object>());
    if (wrapper.IsEmpty())
      return scope.Escape(Local<Value>::New(env->isolate(), Local<Value>()));

    Wrap(wrapper, this);
    return scope.Escape(wrapper);
  }


  Local<Context> CreateV8Context(Environment* env, Local<Object> sandbox_obj) {
    EscapableHandleScope scope(env->isolate());
    Local<FunctionTemplate> function_template =
        FunctionTemplate::New(env->isolate());

    function_template->SetClassName(sandbox_obj->GetConstructorName());

    Local<ObjectTemplate> object_template =
        function_template->InstanceTemplate();

    NamedPropertyHandlerConfiguration config(PropertyGetterCallback,
                                             PropertySetterCallback,
                                             PropertyDescriptorCallback,
                                             PropertyDeleterCallback,
                                             PropertyEnumeratorCallback,
                                             PropertyDefinerCallback,
                                             CreateDataWrapper(env));

    IndexedPropertyHandlerConfiguration indexed_config(
        IndexedPropertyGetterCallback,
        IndexedPropertySetterCallback,
        IndexedPropertyDescriptorCallback,
        IndexedPropertyDeleterCallback,
        PropertyEnumeratorCallback,
        IndexedPropertyDefinerCallback,
        CreateDataWrapper(env));

    object_template->SetHandler(config);
    object_template->SetHandler(indexed_config);

    Local<Context> ctx = NewContext(env->isolate(), object_template);

    if (ctx.IsEmpty()) {
      env->ThrowError("Could not instantiate context");
      return Local<Context>();
    }

    ctx->SetSecurityToken(env->context()->GetSecurityToken());

    // We need to tie the lifetime of the sandbox object with the lifetime of
    // newly created context. We do this by making them hold references to each
    // other. The context can directly hold a reference to the sandbox as an
    // embedder data field. However, we cannot hold a reference to a v8::Context
    // directly in an Object, we instead hold onto the new context's global
    // object instead (which then has a reference to the context).
    ctx->SetEmbedderData(kSandboxObjectIndex, sandbox_obj);
    sandbox_obj->SetPrivate(env->context(),
                            env->contextify_global_private_symbol(),
                            ctx->Global());

    env->AssignToContext(ctx);

    return scope.Escape(ctx);
  }


  static void Init(Environment* env, Local<Object> target) {
    Local<FunctionTemplate> function_template =
        FunctionTemplate::New(env->isolate());
    function_template->InstanceTemplate()->SetInternalFieldCount(1);
    env->set_script_data_constructor_function(function_template->GetFunction());

    env->SetMethod(target, "makeContext", MakeContext);
    env->SetMethod(target, "isContext", IsContext);
  }


  static void MakeContext(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);

    if (!args[0]->IsObject()) {
      return env->ThrowTypeError("sandbox argument must be an object.");
    }
    Local<Object> sandbox = args[0].As<Object>();

    // Don't allow contextifying a sandbox multiple times.
    CHECK(
        !sandbox->HasPrivate(
            env->context(),
            env->contextify_context_private_symbol()).FromJust());

    TryCatch try_catch(env->isolate());
    ContextifyContext* context = new ContextifyContext(env, sandbox);

    if (try_catch.HasCaught()) {
      try_catch.ReThrow();
      return;
    }

    if (context->context().IsEmpty())
      return;

    sandbox->SetPrivate(
        env->context(),
        env->contextify_context_private_symbol(),
        External::New(env->isolate(), context));
  }


  static void IsContext(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);

    if (!args[0]->IsObject()) {
      env->ThrowTypeError("sandbox must be an object");
      return;
    }
    Local<Object> sandbox = args[0].As<Object>();

    Maybe<bool> result =
        sandbox->HasPrivate(env->context(),
                            env->contextify_context_private_symbol());
    args.GetReturnValue().Set(result.FromJust());
  }


  static void WeakCallback(const WeakCallbackInfo<ContextifyContext>& data) {
    ContextifyContext* context = data.GetParameter();
    delete context;
  }


  static ContextifyContext* ContextFromContextifiedSandbox(
      Environment* env,
      const Local<Object>& sandbox) {
    MaybeLocal<Value> maybe_value =
        sandbox->GetPrivate(env->context(),
                            env->contextify_context_private_symbol());
    Local<Value> context_external_v;
    if (maybe_value.ToLocal(&context_external_v) &&
        context_external_v->IsExternal()) {
      Local<External> context_external = context_external_v.As<External>();
      return static_cast<ContextifyContext*>(context_external->Value());
    }
    return nullptr;
  }


  static void PropertyGetterCallback(
      Local<Name> property,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    Local<Context> context = ctx->context();
    Local<Object> sandbox = ctx->sandbox();
    MaybeLocal<Value> maybe_rv =
        sandbox->GetRealNamedProperty(context, property);
    if (maybe_rv.IsEmpty()) {
      maybe_rv =
          ctx->global_proxy()->GetRealNamedProperty(context, property);
    }

    Local<Value> rv;
    if (maybe_rv.ToLocal(&rv)) {
      if (rv == sandbox)
        rv = ctx->global_proxy();

      args.GetReturnValue().Set(rv);
    }
  }


  static void PropertySetterCallback(
      Local<Name> property,
      Local<Value> value,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    auto attributes = PropertyAttribute::None;
    bool is_declared_on_global_proxy = ctx->global_proxy()
        ->GetRealNamedPropertyAttributes(ctx->context(), property)
        .To(&attributes);
    bool read_only =
        static_cast<int>(attributes) &
        static_cast<int>(PropertyAttribute::ReadOnly);

    bool is_declared_on_sandbox = ctx->sandbox()
        ->GetRealNamedPropertyAttributes(ctx->context(), property)
        .To(&attributes);
    read_only = read_only ||
        (static_cast<int>(attributes) &
        static_cast<int>(PropertyAttribute::ReadOnly));

    if (read_only)
      return;

    // true for x = 5
    // false for this.x = 5
    // false for Object.defineProperty(this, 'foo', ...)
    // false for vmResult.x = 5 where vmResult = vm.runInContext();
    bool is_contextual_store = ctx->global_proxy() != args.This();

    // Indicator to not return before setting (undeclared) function declarations
    // on the sandbox in strict mode, i.e. args.ShouldThrowOnError() = true.
    // True for 'function f() {}', 'this.f = function() {}',
    // 'var f = function()'.
    // In effect only for 'function f() {}' because
    // var f = function(), is_declared = true
    // this.f = function() {}, is_contextual_store = false.
    bool is_function = value->IsFunction();

    bool is_declared = is_declared_on_global_proxy || is_declared_on_sandbox;
    if (!is_declared && args.ShouldThrowOnError() && is_contextual_store &&
        !is_function)
      return;

    if (!is_declared_on_global_proxy && is_declared_on_sandbox  &&
        args.ShouldThrowOnError() && is_contextual_store && !is_function) {
      // The property exists on the sandbox but not on the global
      // proxy. Setting it would throw because we are in strict mode.
      // Don't attempt to set it by signaling that the call was
      // intercepted. Only change the value on the sandbox.
      args.GetReturnValue().Set(false);
    }

    ctx->sandbox()->Set(property, value);
  }


  static void PropertyDescriptorCallback(
      Local<Name> property,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    Local<Context> context = ctx->context();

    Local<Object> sandbox = ctx->sandbox();

    if (sandbox->HasOwnProperty(context, property).FromMaybe(false)) {
      args.GetReturnValue().Set(
          sandbox->GetOwnPropertyDescriptor(context, property)
              .ToLocalChecked());
    }
  }


  static void PropertyDefinerCallback(
      Local<Name> property,
      const PropertyDescriptor& desc,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    Local<Context> context = ctx->context();
    v8::Isolate* isolate = context->GetIsolate();

    auto attributes = PropertyAttribute::None;
    bool is_declared =
        ctx->global_proxy()->GetRealNamedPropertyAttributes(ctx->context(),
                                                            property)
            .To(&attributes);
    bool read_only =
        static_cast<int>(attributes) &
            static_cast<int>(PropertyAttribute::ReadOnly);

    // If the property is set on the global as read_only, don't change it on
    // the global or sandbox.
    if (is_declared && read_only)
      return;

    Local<Object> sandbox = ctx->sandbox();

    auto define_prop_on_sandbox =
        [&] (PropertyDescriptor* desc_for_sandbox) {
          if (desc.has_enumerable()) {
            desc_for_sandbox->set_enumerable(desc.enumerable());
          }
          if (desc.has_configurable()) {
            desc_for_sandbox->set_configurable(desc.configurable());
          }
          // Set the property on the sandbox.
          sandbox->DefineProperty(context, property, *desc_for_sandbox)
              .FromJust();
        };

    if (desc.has_get() || desc.has_set()) {
      PropertyDescriptor desc_for_sandbox(
          desc.has_get() ? desc.get() : v8::Undefined(isolate).As<Value>(),
          desc.has_set() ? desc.set() : v8::Undefined(isolate).As<Value>());

      define_prop_on_sandbox(&desc_for_sandbox);
    } else {
      Local<Value> value =
          desc.has_value() ? desc.value() : v8::Undefined(isolate).As<Value>();

      if (desc.has_writable()) {
        PropertyDescriptor desc_for_sandbox(value, desc.writable());
        define_prop_on_sandbox(&desc_for_sandbox);
      } else {
        PropertyDescriptor desc_for_sandbox(value);
        define_prop_on_sandbox(&desc_for_sandbox);
      }
    }
  }

  static void PropertyDeleterCallback(
      Local<Name> property,
      const PropertyCallbackInfo<Boolean>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    Maybe<bool> success = ctx->sandbox()->Delete(ctx->context(), property);

    if (success.FromMaybe(false))
      return;

    // Delete failed on the sandbox, intercept and do not delete on
    // the global object.
    args.GetReturnValue().Set(false);
  }


  static void PropertyEnumeratorCallback(
      const PropertyCallbackInfo<Array>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    args.GetReturnValue().Set(ctx->sandbox()->GetPropertyNames());
  }

  static void IndexedPropertyGetterCallback(
      uint32_t index,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    PropertyGetterCallback(Uint32ToName(ctx->context(), index), args);
  }


  static void IndexedPropertySetterCallback(
      uint32_t index,
      Local<Value> value,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    PropertySetterCallback(Uint32ToName(ctx->context(), index), value, args);
  }


  static void IndexedPropertyDescriptorCallback(
      uint32_t index,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    PropertyDescriptorCallback(Uint32ToName(ctx->context(), index), args);
  }


  static void IndexedPropertyDefinerCallback(
      uint32_t index,
      const PropertyDescriptor& desc,
      const PropertyCallbackInfo<Value>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    PropertyDefinerCallback(Uint32ToName(ctx->context(), index), desc, args);
  }

  static void IndexedPropertyDeleterCallback(
      uint32_t index,
      const PropertyCallbackInfo<Boolean>& args) {
    ContextifyContext* ctx;
    ASSIGN_OR_RETURN_UNWRAP(&ctx, args.Data().As<Object>());

    // Still initializing
    if (ctx->context_.IsEmpty())
      return;

    Maybe<bool> success = ctx->sandbox()->Delete(ctx->context(), index);

    if (success.FromMaybe(false))
      return;

    // Delete failed on the sandbox, intercept and do not delete on
    // the global object.
    args.GetReturnValue().Set(false);
  }
};

class ContextifyScript : public BaseObject {
 private:
  Persistent<UnboundScript> script_;

 public:
  static void Init(Environment* env, Local<Object> target) {
    HandleScope scope(env->isolate());
    Local<String> class_name =
        FIXED_ONE_BYTE_STRING(env->isolate(), "ContextifyScript");

    Local<FunctionTemplate> script_tmpl = env->NewFunctionTemplate(New);
    script_tmpl->InstanceTemplate()->SetInternalFieldCount(1);
    script_tmpl->SetClassName(class_name);
    env->SetProtoMethod(script_tmpl, "runInContext", RunInContext);
    env->SetProtoMethod(script_tmpl, "runInThisContext", RunInThisContext);

    target->Set(class_name, script_tmpl->GetFunction());
    env->set_script_context_constructor_template(script_tmpl);

    Local<Symbol> parsing_context_symbol =
        Symbol::New(env->isolate(),
                    FIXED_ONE_BYTE_STRING(env->isolate(),
                                          "script parsing context"));
    env->set_vm_parsing_context_symbol(parsing_context_symbol);
    target->Set(env->context(),
                FIXED_ONE_BYTE_STRING(env->isolate(), "kParsingContext"),
                parsing_context_symbol)
        .FromJust();
  }


  // args: code, [options]
  static void New(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);

    if (!args.IsConstructCall()) {
      return env->ThrowError("Must call vm.Script as a constructor.");
    }

    ContextifyScript* contextify_script =
        new ContextifyScript(env, args.This());

    TryCatch try_catch(env->isolate());
    Local<String> code = args[0]->ToString(env->isolate());

    Local<Value> options = args[1];
    MaybeLocal<String> filename = GetFilenameArg(env, options);
    MaybeLocal<Integer> lineOffset = GetLineOffsetArg(env, options);
    MaybeLocal<Integer> columnOffset = GetColumnOffsetArg(env, options);
    Maybe<bool> maybe_display_errors = GetDisplayErrorsArg(env, options);
    MaybeLocal<Uint8Array> cached_data_buf = GetCachedData(env, options);
    Maybe<bool> maybe_produce_cached_data = GetProduceCachedData(env, options);
    MaybeLocal<Context> maybe_context = GetContext(env, options);
    if (try_catch.HasCaught()) {
      try_catch.ReThrow();
      return;
    }

    bool display_errors = maybe_display_errors.ToChecked();
    bool produce_cached_data = maybe_produce_cached_data.ToChecked();

    ScriptCompiler::CachedData* cached_data = nullptr;
    Local<Uint8Array> ui8;
    if (cached_data_buf.ToLocal(&ui8)) {
      ArrayBuffer::Contents contents = ui8->Buffer()->GetContents();
      cached_data = new ScriptCompiler::CachedData(
          static_cast<uint8_t*>(contents.Data()) + ui8->ByteOffset(),
          ui8->ByteLength());
    }

    ScriptOrigin origin(filename.ToLocalChecked(), lineOffset.ToLocalChecked(),
                        columnOffset.ToLocalChecked());
    ScriptCompiler::Source source(code, origin, cached_data);
    ScriptCompiler::CompileOptions compile_options =
        ScriptCompiler::kNoCompileOptions;

    if (source.GetCachedData() != nullptr)
      compile_options = ScriptCompiler::kConsumeCodeCache;
    else if (produce_cached_data)
      compile_options = ScriptCompiler::kProduceCodeCache;

    Context::Scope scope(maybe_context.FromMaybe(env->context()));

    MaybeLocal<UnboundScript> v8_script = ScriptCompiler::CompileUnboundScript(
        env->isolate(),
        &source,
        compile_options);

    if (v8_script.IsEmpty()) {
      if (display_errors) {
        DecorateErrorStack(env, try_catch);
      }
      try_catch.ReThrow();
      return;
    }
    contextify_script->script_.Reset(env->isolate(),
                                     v8_script.ToLocalChecked());

    if (compile_options == ScriptCompiler::kConsumeCodeCache) {
      args.This()->Set(
          env->cached_data_rejected_string(),
          Boolean::New(env->isolate(), source.GetCachedData()->rejected));
    } else if (compile_options == ScriptCompiler::kProduceCodeCache) {
      const ScriptCompiler::CachedData* cached_data = source.GetCachedData();
      bool cached_data_produced = cached_data != nullptr;
      if (cached_data_produced) {
        MaybeLocal<Object> buf = Buffer::Copy(
            env,
            reinterpret_cast<const char*>(cached_data->data),
            cached_data->length);
        args.This()->Set(env->cached_data_string(), buf.ToLocalChecked());
      }
      args.This()->Set(
          env->cached_data_produced_string(),
          Boolean::New(env->isolate(), cached_data_produced));
    }
  }


  static bool InstanceOf(Environment* env, const Local<Value>& value) {
    return !value.IsEmpty() &&
           env->script_context_constructor_template()->HasInstance(value);
  }


  // args: [options]
  static void RunInThisContext(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);

    // Assemble arguments
    TryCatch try_catch(args.GetIsolate());
    Maybe<int64_t> maybe_timeout = GetTimeoutArg(env, args[0]);
    Maybe<bool> maybe_display_errors = GetDisplayErrorsArg(env, args[0]);
    Maybe<bool> maybe_break_on_sigint = GetBreakOnSigintArg(env, args[0]);
    if (try_catch.HasCaught()) {
      try_catch.ReThrow();
      return;
    }

    int64_t timeout = maybe_timeout.ToChecked();
    bool display_errors = maybe_display_errors.ToChecked();
    bool break_on_sigint = maybe_break_on_sigint.ToChecked();

    // Do the eval within this context
    EvalMachine(env, timeout, display_errors, break_on_sigint, args,
                &try_catch);
  }

  // args: sandbox, [options]
  static void RunInContext(const FunctionCallbackInfo<Value>& args) {
    Environment* env = Environment::GetCurrent(args);

    int64_t timeout;
    bool display_errors;
    bool break_on_sigint;

    // Assemble arguments
    if (!args[0]->IsObject()) {
      return env->ThrowTypeError(
          "contextifiedSandbox argument must be an object.");
    }

    Local<Object> sandbox = args[0].As<Object>();
    {
      TryCatch try_catch(env->isolate());
      Maybe<int64_t> maybe_timeout = GetTimeoutArg(env, args[1]);
      Maybe<bool> maybe_display_errors = GetDisplayErrorsArg(env, args[1]);
      Maybe<bool> maybe_break_on_sigint = GetBreakOnSigintArg(env, args[1]);
      if (try_catch.HasCaught()) {
        try_catch.ReThrow();
        return;
      }

      timeout = maybe_timeout.ToChecked();
      display_errors = maybe_display_errors.ToChecked();
      break_on_sigint = maybe_break_on_sigint.ToChecked();
    }

    // Get the context from the sandbox
    ContextifyContext* contextify_context =
        ContextifyContext::ContextFromContextifiedSandbox(env, sandbox);
    if (contextify_context == nullptr) {
      return env->ThrowTypeError(
          "sandbox argument must have been converted to a context.");
    }

    if (contextify_context->context().IsEmpty())
      return;

    {
      TryCatch try_catch(env->isolate());
      // Do the eval within the context
      Context::Scope context_scope(contextify_context->context());
      EvalMachine(contextify_context->env(),
                  timeout,
                  display_errors,
                  break_on_sigint,
                  args,
                  &try_catch);

      if (try_catch.HasCaught()) {
        try_catch.ReThrow();
        return;
      }
    }
  }

  static void DecorateErrorStack(Environment* env, const TryCatch& try_catch) {
    Local<Value> exception = try_catch.Exception();

    if (!exception->IsObject())
      return;

    Local<Object> err_obj = exception.As<Object>();

    if (IsExceptionDecorated(env, err_obj))
      return;

    AppendExceptionLine(env, exception, try_catch.Message(), CONTEXTIFY_ERROR);
    Local<Value> stack = err_obj->Get(env->stack_string());
    MaybeLocal<Value> maybe_value =
        err_obj->GetPrivate(
            env->context(),
            env->arrow_message_private_symbol());

    Local<Value> arrow;
    if (!(maybe_value.ToLocal(&arrow) && arrow->IsString())) {
      return;
    }

    if (stack.IsEmpty() || !stack->IsString()) {
      return;
    }

    Local<String> decorated_stack = String::Concat(
        String::Concat(arrow.As<String>(),
          FIXED_ONE_BYTE_STRING(env->isolate(), "\n")),
        stack.As<String>());
    err_obj->Set(env->stack_string(), decorated_stack);
    err_obj->SetPrivate(
        env->context(),
        env->decorated_private_symbol(),
        True(env->isolate()));
  }

  static Maybe<bool> GetBreakOnSigintArg(Environment* env,
                                         Local<Value> options) {
    if (options->IsUndefined() || options->IsString()) {
      return Just(false);
    }
    if (!options->IsObject()) {
      env->ThrowTypeError("options must be an object");
      return Nothing<bool>();
    }

    Local<String> key = FIXED_ONE_BYTE_STRING(env->isolate(), "breakOnSigint");
    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(), key);
    if (maybe_value.IsEmpty())
      return Nothing<bool>();

    Local<Value> value = maybe_value.ToLocalChecked();
    return Just(value->IsTrue());
  }

  static Maybe<int64_t> GetTimeoutArg(Environment* env, Local<Value> options) {
    if (options->IsUndefined() || options->IsString()) {
      return Just<int64_t>(-1);
    }
    if (!options->IsObject()) {
      env->ThrowTypeError("options must be an object");
      return Nothing<int64_t>();
    }

    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(), env->timeout_string());
    if (maybe_value.IsEmpty())
      return Nothing<int64_t>();

    Local<Value> value = maybe_value.ToLocalChecked();
    if (value->IsUndefined()) {
      return Just<int64_t>(-1);
    }

    Maybe<int64_t> timeout = value->IntegerValue(env->context());

    if (timeout.IsJust() && timeout.ToChecked() <= 0) {
      env->ThrowRangeError("timeout must be a positive number");
      return Nothing<int64_t>();
    }

    return timeout;
  }


  static Maybe<bool> GetDisplayErrorsArg(Environment* env,
                                         Local<Value> options) {
    if (options->IsUndefined() || options->IsString()) {
      return Just(true);
    }
    if (!options->IsObject()) {
      env->ThrowTypeError("options must be an object");
      return Nothing<bool>();
    }

    Local<String> key = FIXED_ONE_BYTE_STRING(env->isolate(), "displayErrors");
    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(), key);
    if (maybe_value.IsEmpty())
      return Nothing<bool>();

    Local<Value> value = maybe_value.ToLocalChecked();
    if (value->IsUndefined())
      return Just(true);

    return value->BooleanValue(env->context());
  }


  static MaybeLocal<String> GetFilenameArg(Environment* env,
                                           Local<Value> options) {
    Local<String> defaultFilename =
        FIXED_ONE_BYTE_STRING(env->isolate(), "evalmachine.<anonymous>");

    if (options->IsUndefined()) {
      return defaultFilename;
    }
    if (options->IsString()) {
      return options.As<String>();
    }
    if (!options->IsObject()) {
      env->ThrowTypeError("options must be an object");
      return Local<String>();
    }

    Local<String> key = FIXED_ONE_BYTE_STRING(env->isolate(), "filename");
    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(), key);
    if (maybe_value.IsEmpty())
      return MaybeLocal<String>();

    Local<Value> value = maybe_value.ToLocalChecked();
    if (value->IsUndefined())
      return defaultFilename;
    return value->ToString(env->context());
  }


  static MaybeLocal<Uint8Array> GetCachedData(Environment* env,
                                              Local<Value> options) {
    if (!options->IsObject()) {
      return MaybeLocal<Uint8Array>();
    }

    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(), env->cached_data_string());
    if (maybe_value.IsEmpty())
      return MaybeLocal<Uint8Array>();

    Local<Value> value = maybe_value.ToLocalChecked();
    if (value->IsUndefined()) {
      return MaybeLocal<Uint8Array>();
    }

    if (!value->IsUint8Array()) {
      env->ThrowTypeError("options.cachedData must be a Buffer instance");
      return MaybeLocal<Uint8Array>();
    }

    return value.As<Uint8Array>();
  }


  static Maybe<bool> GetProduceCachedData(Environment* env,
                                          Local<Value> options) {
    if (!options->IsObject()) {
      return Just(false);
    }

    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(),
                                  env->produce_cached_data_string());
    if (maybe_value.IsEmpty())
      return Nothing<bool>();

    Local<Value> value = maybe_value.ToLocalChecked();
    return Just(value->IsTrue());
  }


  static MaybeLocal<Integer> GetLineOffsetArg(Environment* env,
                                              Local<Value> options) {
    Local<Integer> defaultLineOffset = Integer::New(env->isolate(), 0);

    if (!options->IsObject()) {
      return defaultLineOffset;
    }

    Local<String> key = FIXED_ONE_BYTE_STRING(env->isolate(), "lineOffset");
    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(), key);
    if (maybe_value.IsEmpty())
      return MaybeLocal<Integer>();

    Local<Value> value = maybe_value.ToLocalChecked();
    if (value->IsUndefined())
      return defaultLineOffset;

    return value->ToInteger(env->context());
  }


  static MaybeLocal<Integer> GetColumnOffsetArg(Environment* env,
                                                Local<Value> options) {
    Local<Integer> defaultColumnOffset = Integer::New(env->isolate(), 0);

    if (!options->IsObject()) {
      return defaultColumnOffset;
    }

    Local<String> key = FIXED_ONE_BYTE_STRING(env->isolate(), "columnOffset");
    MaybeLocal<Value> maybe_value =
      options.As<Object>()->Get(env->context(), key);
    if (maybe_value.IsEmpty())
      return MaybeLocal<Integer>();

    Local<Value> value = maybe_value.ToLocalChecked();
    if (value->IsUndefined())
      return defaultColumnOffset;

    return value->ToInteger(env->context());
  }

  static MaybeLocal<Context> GetContext(Environment* env,
                                        Local<Value> options) {
    if (!options->IsObject())
      return MaybeLocal<Context>();

    MaybeLocal<Value> maybe_value =
        options.As<Object>()->Get(env->context(),
                                  env->vm_parsing_context_symbol());
    Local<Value> value;
    if (!maybe_value.ToLocal(&value))
      return MaybeLocal<Context>();

    if (!value->IsObject()) {
      if (!value->IsNullOrUndefined()) {
        env->ThrowTypeError(
            "contextifiedSandbox argument must be an object.");
      }
      return MaybeLocal<Context>();
    }

    ContextifyContext* sandbox =
        ContextifyContext::ContextFromContextifiedSandbox(
            env, value.As<Object>());
    if (!sandbox) {
      env->ThrowTypeError(
          "sandbox argument must have been converted to a context.");
      return MaybeLocal<Context>();
    }

    Local<Context> context = sandbox->context();
    if (context.IsEmpty())
      return MaybeLocal<Context>();
    return context;
  }


  static bool EvalMachine(Environment* env,
                          const int64_t timeout,
                          const bool display_errors,
                          const bool break_on_sigint,
                          const FunctionCallbackInfo<Value>& args,
                          TryCatch* try_catch) {
    if (!ContextifyScript::InstanceOf(env, args.Holder())) {
      env->ThrowTypeError(
          "Script methods can only be called on script instances.");
      return false;
    }

    ContextifyScript* wrapped_script;
    ASSIGN_OR_RETURN_UNWRAP(&wrapped_script, args.Holder(), false);
    Local<UnboundScript> unbound_script =
        PersistentToLocal(env->isolate(), wrapped_script->script_);
    Local<Script> script = unbound_script->BindToCurrentContext();

    Local<Value> result;
    bool timed_out = false;
    bool received_signal = false;
    if (break_on_sigint && timeout != -1) {
      Watchdog wd(env->isolate(), timeout, &timed_out);
      SigintWatchdog swd(env->isolate(), &received_signal);
      result = script->Run();
    } else if (break_on_sigint) {
      SigintWatchdog swd(env->isolate(), &received_signal);
      result = script->Run();
    } else if (timeout != -1) {
      Watchdog wd(env->isolate(), timeout, &timed_out);
      result = script->Run();
    } else {
      result = script->Run();
    }

    if (timed_out || received_signal) {
      // It is possible that execution was terminated by another timeout in
      // which this timeout is nested, so check whether one of the watchdogs
      // from this invocation is responsible for termination.
      if (timed_out) {
        env->ThrowError("Script execution timed out.");
      } else if (received_signal) {
        env->ThrowError("Script execution interrupted.");
      }
      env->isolate()->CancelTerminateExecution();
    }

    if (try_catch->HasCaught()) {
      if (!timed_out && !received_signal && display_errors) {
        // We should decorate non-termination exceptions
        DecorateErrorStack(env, *try_catch);
      }

      // If there was an exception thrown during script execution, re-throw it.
      // If one of the above checks threw, re-throw the exception instead of
      // letting try_catch catch it.
      // If execution has been terminated, but not by one of the watchdogs from
      // this invocation, this will re-throw a `null` value.
      try_catch->ReThrow();

      return false;
    }

    args.GetReturnValue().Set(result);
    return true;
  }


  ContextifyScript(Environment* env, Local<Object> object)
      : BaseObject(env, object) {
    MakeWeak<ContextifyScript>(this);
  }


  ~ContextifyScript() override {
    script_.Reset();
  }
};


void InitContextify(Local<Object> target,
                    Local<Value> unused,
                    Local<Context> context) {
  Environment* env = Environment::GetCurrent(context);
  ContextifyContext::Init(env, target);
  ContextifyScript::Init(env, target);
}

}  // anonymous namespace
}  // namespace node

NODE_BUILTIN_MODULE_CONTEXT_AWARE(contextify, node::InitContextify)