src: add internalBindings for binding isolation

This commit adds a method to internal/process that allows access to
bindings that are not intended to be used by user code. It has a
separate cache object and modlist in order to avoid collisions.

You can use NODE_MODULE_CONTEXT_AWARE_INTERNAL to register a C++
module as an internal.

PR-URL: https://github.com/nodejs/node/pull/15759
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>

6 files changed, 117 insertions, 46 deletions

diff --git a/src/env-inl.h b/src/env-inl.h
index 0297e66977..c8f8b21e03 100644
--- a/src/env-inl.h
+++ b/src/env-inl.h
@@ -303,7 +303,17 @@ inline Environment::Environment(IsolateData* isolate_data,
   v8::HandleScope handle_scope(isolate());
   v8::Context::Scope context_scope(context);
   set_as_external(v8::External::New(isolate(), this));
-  set_binding_cache_object(v8::Object::New(isolate()));
+
+  v8::Local<v8::Primitive> null = v8::Null(isolate());
+  v8::Local<v8::Object> binding_cache_object = v8::Object::New(isolate());
+  CHECK(binding_cache_object->SetPrototype(context, null).FromJust());
+  set_binding_cache_object(binding_cache_object);
+
+  v8::Local<v8::Object> internal_binding_cache_object =
+      v8::Object::New(isolate());
+  CHECK(internal_binding_cache_object->SetPrototype(context, null).FromJust());
+  set_internal_binding_cache_object(internal_binding_cache_object);
+
   set_module_load_list_array(v8::Array::New(isolate()));
 
   AssignToContext(context);
diff --git a/src/env.h b/src/env.h
index 567d87a313..18f1de17cc 100644
--- a/src/env.h
+++ b/src/env.h
@@ -302,6 +302,7 @@ class ModuleWrap;
   V(async_hooks_after_function, v8::Function)                                 \
   V(async_hooks_promise_resolve_function, v8::Function)                       \
   V(binding_cache_object, v8::Object)                                         \
+  V(internal_binding_cache_object, v8::Object)                                \
   V(buffer_prototype_object, v8::Object)                                      \
   V(context, v8::Context)                                                     \
   V(domain_array, v8::Array)                                                  \
diff --git a/src/module_wrap.cc b/src/module_wrap.cc
index cbee6faff3..829248b681 100644
--- a/src/module_wrap.cc
+++ b/src/module_wrap.cc
@@ -7,6 +7,7 @@
 #include "node_url.h"
 #include "util.h"
 #include "util-inl.h"
+#include "node_internals.h"
 
 namespace node {
 namespace loader {
@@ -523,5 +524,5 @@ void ModuleWrap::Initialize(Local<Object> target,
 }  // namespace loader
 }  // namespace node
 
-NODE_MODULE_CONTEXT_AWARE_BUILTIN(module_wrap,
-                                  node::loader::ModuleWrap::Initialize)
+NODE_MODULE_CONTEXT_AWARE_INTERNAL(module_wrap,
+                                   node::loader::ModuleWrap::Initialize)
diff --git a/src/node.cc b/src/node.cc
index a73d8b5807..1bc75abef3 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -183,6 +183,7 @@ static bool v8_is_profiling = false;
 static bool node_is_initialized = false;
 static node_module* modpending;
 static node_module* modlist_builtin;
+static node_module* modlist_internal;
 static node_module* modlist_linked;
 static node_module* modlist_addon;
 static bool trace_enabled = false;
@@ -2574,6 +2575,9 @@ extern "C" void node_module_register(void* m) {
   if (mp->nm_flags & NM_F_BUILTIN) {
     mp->nm_link = modlist_builtin;
     modlist_builtin = mp;
+  } else if (mp->nm_flags & NM_F_INTERNAL) {
+    mp->nm_link = modlist_internal;
+    modlist_internal = mp;
   } else if (!node_is_initialized) {
     // "Linked" modules are included as part of the node project.
     // Like builtins they are registered *before* node::Init runs.
@@ -2585,28 +2589,28 @@ extern "C" void node_module_register(void* m) {
   }
 }
 
-struct node_module* get_builtin_module(const char* name) {
+inline struct node_module* FindModule(struct node_module* list,
+                                      const char* name,
+                                      int flag) {
   struct node_module* mp;
 
-  for (mp = modlist_builtin; mp != nullptr; mp = mp->nm_link) {
+  for (mp = list; mp != nullptr; mp = mp->nm_link) {
     if (strcmp(mp->nm_modname, name) == 0)
       break;
   }
 
-  CHECK(mp == nullptr || (mp->nm_flags & NM_F_BUILTIN) != 0);
-  return (mp);
+  CHECK(mp == nullptr || (mp->nm_flags & flag) != 0);
+  return mp;
 }
 
-struct node_module* get_linked_module(const char* name) {
-  struct node_module* mp;
-
-  for (mp = modlist_linked; mp != nullptr; mp = mp->nm_link) {
-    if (strcmp(mp->nm_modname, name) == 0)
-      break;
-  }
-
-  CHECK(mp == nullptr || (mp->nm_flags & NM_F_LINKED) != 0);
-  return mp;
+node_module* get_builtin_module(const char* name) {
+  return FindModule(modlist_builtin, name, NM_F_BUILTIN);
+}
+node_module* get_internal_module(const char* name) {
+  return FindModule(modlist_internal, name, NM_F_INTERNAL);
+}
+node_module* get_linked_module(const char* name) {
+  return FindModule(modlist_linked, name, NM_F_LINKED);
 }
 
 struct DLib {
@@ -2880,24 +2884,60 @@ void ProcessEmitWarning(Environment* env, const char* fmt, ...) {
   f.As<v8::Function>()->Call(process, 1, &arg);
 }
 
+static bool PullFromCache(Environment* env,
+                          const FunctionCallbackInfo<Value>& args,
+                          Local<String> module,
+                          Local<Object> cache) {
+  Local<Context> context = env->context();
+  Local<Value> exports_v;
+  Local<Object> exports;
+  if (cache->Get(context, module).ToLocal(&exports_v) &&
+      exports_v->IsObject() &&
+      exports_v->ToObject(context).ToLocal(&exports)) {
+    args.GetReturnValue().Set(exports);
+    return true;
+  }
+  return false;
+}
+
+static Local<Object> InitModule(Environment* env,
+                                 node_module* mod,
+                                 Local<String> module) {
+  Local<Object> exports = Object::New(env->isolate());
+  // Internal bindings don't have a "module" object, only exports.
+  CHECK_EQ(mod->nm_register_func, nullptr);
+  CHECK_NE(mod->nm_context_register_func, nullptr);
+  Local<Value> unused = Undefined(env->isolate());
+  mod->nm_context_register_func(exports,
+                                unused,
+                                env->context(),
+                                mod->nm_priv);
+  return exports;
+}
+
+static void ThrowIfNoSuchModule(Environment* env, const char* module_v) {
+  char errmsg[1024];
+  snprintf(errmsg,
+           sizeof(errmsg),
+           "No such module: %s",
+           module_v);
+  env->ThrowError(errmsg);
+}
 
 static void Binding(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
 
-  Local<String> module = args[0]->ToString(env->isolate());
-  node::Utf8Value module_v(env->isolate(), module);
+  Local<String> module;
+  if (!args[0]->ToString(env->context()).ToLocal(&module)) return;
 
   Local<Object> cache = env->binding_cache_object();
-  Local<Object> exports;
 
-  if (cache->Has(env->context(), module).FromJust()) {
-    exports = cache->Get(module)->ToObject(env->isolate());
-    args.GetReturnValue().Set(exports);
+  if (PullFromCache(env, args, module, cache))
     return;
-  }
 
   // Append a string to process.moduleLoadList
   char buf[1024];
+  node::Utf8Value module_v(env->isolate(), module);
   snprintf(buf, sizeof(buf), "Binding %s", *module_v);
 
   Local<Array> modules = env->module_load_list_array();
@@ -2905,33 +2945,49 @@ static void Binding(const FunctionCallbackInfo<Value>& args) {
   modules->Set(l, OneByteString(env->isolate(), buf));
 
   node_module* mod = get_builtin_module(*module_v);
+  Local<Object> exports;
   if (mod != nullptr) {
-    exports = Object::New(env->isolate());
-    // Internal bindings don't have a "module" object, only exports.
-    CHECK_EQ(mod->nm_register_func, nullptr);
-    CHECK_NE(mod->nm_context_register_func, nullptr);
-    Local<Value> unused = Undefined(env->isolate());
-    mod->nm_context_register_func(exports, unused,
-      env->context(), mod->nm_priv);
-    cache->Set(module, exports);
+    exports = InitModule(env, mod, module);
   } else if (!strcmp(*module_v, "constants")) {
     exports = Object::New(env->isolate());
     CHECK(exports->SetPrototype(env->context(),
                                 Null(env->isolate())).FromJust());
     DefineConstants(env->isolate(), exports);
-    cache->Set(module, exports);
   } else if (!strcmp(*module_v, "natives")) {
     exports = Object::New(env->isolate());
     DefineJavaScript(env, exports);
-    cache->Set(module, exports);
   } else {
-    char errmsg[1024];
-    snprintf(errmsg,
-             sizeof(errmsg),
-             "No such module: %s",
-             *module_v);
-    return env->ThrowError(errmsg);
+    return ThrowIfNoSuchModule(env, *module_v);
   }
+  cache->Set(module, exports);
+
+  args.GetReturnValue().Set(exports);
+}
+
+static void InternalBinding(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+
+  Local<String> module;
+  if (!args[0]->ToString(env->context()).ToLocal(&module)) return;
+
+  Local<Object> cache = env->internal_binding_cache_object();
+
+  if (PullFromCache(env, args, module, cache))
+    return;
+
+  // Append a string to process.moduleLoadList
+  char buf[1024];
+  node::Utf8Value module_v(env->isolate(), module);
+  snprintf(buf, sizeof(buf), "Internal Binding %s", *module_v);
+
+  Local<Array> modules = env->module_load_list_array();
+  uint32_t l = modules->Length();
+  modules->Set(l, OneByteString(env->isolate(), buf));
+
+  node_module* mod = get_internal_module(*module_v);
+  if (mod == nullptr) return ThrowIfNoSuchModule(env, *module_v);
+  Local<Object> exports = InitModule(env, mod, module);
+  cache->Set(module, exports);
 
   args.GetReturnValue().Set(exports);
 }
@@ -2939,7 +2995,8 @@ static void Binding(const FunctionCallbackInfo<Value>& args) {
 static void LinkedBinding(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args.GetIsolate());
 
-  Local<String> module_name = args[0]->ToString(env->isolate());
+  Local<String> module_name;
+  if (!args[0]->ToString(env->context()).ToLocal(&module_name)) return;
 
   Local<Object> cache = env->binding_cache_object();
   Local<Value> exports_v = cache->Get(module_name);
@@ -3674,6 +3731,7 @@ void SetupProcessObject(Environment* env,
 
   env->SetMethod(process, "binding", Binding);
   env->SetMethod(process, "_linkedBinding", LinkedBinding);
+  env->SetMethod(process, "_internalBinding", InternalBinding);
 
   env->SetMethod(process, "_setupProcessObject", SetupProcessObject);
   env->SetMethod(process, "_setupNextTick", SetupNextTick);
diff --git a/src/node.h b/src/node.h
index 287823b17b..aa8738a567 100644
--- a/src/node.h
+++ b/src/node.h
@@ -421,8 +421,9 @@ typedef void (*addon_context_register_func)(
     v8::Local<v8::Context> context,
     void* priv);
 
-#define NM_F_BUILTIN 0x01
-#define NM_F_LINKED  0x02
+#define NM_F_BUILTIN   0x01
+#define NM_F_LINKED    0x02
+#define NM_F_INTERNAL  0x04
 
 struct node_module {
   int nm_version;
@@ -436,9 +437,6 @@ struct node_module {
   struct node_module* nm_link;
 };
 
-node_module* get_builtin_module(const char *name);
-node_module* get_linked_module(const char *name);
-
 extern "C" NODE_EXTERN void node_module_register(void* mod);
 
 #ifdef _WIN32
diff --git a/src/node_internals.h b/src/node_internals.h
index 7c4f7a6a7f..54f20c39d3 100644
--- a/src/node_internals.h
+++ b/src/node_internals.h
@@ -324,6 +324,9 @@ class InternalCallbackScope {
   bool closed_ = false;
 };
 
+#define NODE_MODULE_CONTEXT_AWARE_INTERNAL(modname, regfunc)          \
+  NODE_MODULE_CONTEXT_AWARE_X(modname, regfunc, NULL, NM_F_INTERNAL)  \
+
 }  // namespace node