gecko-dev/dom/base/StructuredCloneBlob.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/dom/StructuredCloneBlob.h"

#include <cstddef>
#include <cstdint>
#include <new>
#include <utility>
#include "js/StructuredClone.h"
#include "js/Value.h"
#include "js/Wrapper.h"
#include "jsapi.h"
#include "mozilla/Assertions.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/Maybe.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/dom/BindingDeclarations.h"
#include "mozilla/dom/BlobImpl.h"
#include "mozilla/dom/StructuredCloneHolderBinding.h"
#include "mozilla/dom/StructuredCloneTags.h"
#include "xpcpublic.h"

namespace mozilla::dom {

StructuredCloneBlob::StructuredCloneBlob() {
  mHolder.emplace(Holder::CloningSupported, Holder::TransferringNotSupported,
                  Holder::StructuredCloneScope::DifferentProcess);
}

StructuredCloneBlob::~StructuredCloneBlob() {
  UnregisterWeakMemoryReporter(this);
}

/* static */
already_AddRefed<StructuredCloneBlob> StructuredCloneBlob::Constructor(
    GlobalObject& aGlobal, JS::Handle<JS::Value> aValue,
    JS::Handle<JSObject*> aTargetGlobal, ErrorResult& aRv) {
  JSContext* cx = aGlobal.Context();

  RefPtr<StructuredCloneBlob> holder = StructuredCloneBlob::Create();

  Maybe<JSAutoRealm> ar;
  JS::Rooted<JS::Value> value(cx, aValue);

  if (aTargetGlobal) {
    // OK to unwrap if our caller (represented by cx's Realm) can do it.
    JS::Rooted<JSObject*> targetGlobal(
        cx, js::CheckedUnwrapDynamic(aTargetGlobal, cx));
    if (!targetGlobal) {
      js::ReportAccessDenied(cx);
      aRv.NoteJSContextException(cx);
      return nullptr;
    }

    ar.emplace(cx, targetGlobal);

    if (!JS_WrapValue(cx, &value)) {
      aRv.NoteJSContextException(cx);
      return nullptr;
    }
  } else if (value.isObject()) {
    // OK to unwrap if our caller (represented by cx's Realm) can do it.
    JS::Rooted<JSObject*> obj(cx,
                              js::CheckedUnwrapDynamic(&value.toObject(), cx));
    if (!obj) {
      js::ReportAccessDenied(cx);
      aRv.NoteJSContextException(cx);
      return nullptr;
    }

    ar.emplace(cx, obj);
    value = JS::ObjectValue(*obj);
  }

  holder->mHolder->Write(cx, value, aRv);
  if (aRv.Failed()) {
    return nullptr;
  }

  return holder.forget();
}

void StructuredCloneBlob::Deserialize(JSContext* aCx,
                                      JS::Handle<JSObject*> aTargetScope,
                                      bool aKeepData,
                                      JS::MutableHandle<JS::Value> aResult,
                                      ErrorResult& aRv) {
  // OK to unwrap if our caller (represented by aCx's Realm) can do it.
  JS::Rooted<JSObject*> scope(aCx, js::CheckedUnwrapDynamic(aTargetScope, aCx));
  if (!scope) {
    js::ReportAccessDenied(aCx);
    aRv.NoteJSContextException(aCx);
    return;
  }

  if (!mHolder.isSome()) {
    aRv.Throw(NS_ERROR_NOT_INITIALIZED);
    return;
  }

  {
    JSAutoRealm ar(aCx, scope);

    mHolder->Read(xpc::NativeGlobal(scope), aCx, aResult, aRv);
    if (aRv.Failed()) {
      return;
    }
  }

  if (!aKeepData) {
    mHolder.reset();
  }

  if (!JS_WrapValue(aCx, aResult)) {
    aResult.set(JS::UndefinedValue());
    aRv.NoteJSContextException(aCx);
  }
}

/* static */
JSObject* StructuredCloneBlob::ReadStructuredClone(
    JSContext* aCx, JSStructuredCloneReader* aReader,
    StructuredCloneHolder* aHolder) {
  JS::Rooted<JSObject*> obj(aCx);
  {
    RefPtr<StructuredCloneBlob> holder = StructuredCloneBlob::Create();

    if (!holder->mHolder->ReadStructuredCloneInternal(aCx, aReader, aHolder) ||
        !holder->WrapObject(aCx, nullptr, &obj)) {
      return nullptr;
    }
  }
  return obj.get();
}

bool StructuredCloneBlob::Holder::ReadStructuredCloneInternal(
    JSContext* aCx, JSStructuredCloneReader* aReader,
    StructuredCloneHolder* aHolder) {
  uint32_t length;
  uint32_t version;
  if (!JS_ReadUint32Pair(aReader, &length, &version)) {
    return false;
  }
  if (length % 8 != 0) {
    return false;
  }

  uint32_t blobOffset;
  uint32_t blobCount;
  if (!JS_ReadUint32Pair(aReader, &blobOffset, &blobCount)) {
    return false;
  }
  if (blobCount) {
#ifdef FUZZING
    if (blobOffset >= aHolder->BlobImpls().Length()) {
      return false;
    }
#endif
    BlobImpls().AppendElements(&aHolder->BlobImpls()[blobOffset], blobCount);
  }

  JSStructuredCloneData data(mStructuredCloneScope);
  while (length) {
    size_t size;
    char* buffer = data.AllocateBytes(length, &size);
    if (!buffer || !JS_ReadBytes(aReader, buffer, size)) {
      return false;
    }
    length -= size;
  }

  mBuffer = MakeUnique<JSAutoStructuredCloneBuffer>(
      mStructuredCloneScope, &StructuredCloneHolder::sCallbacks, this);
  mBuffer->adopt(std::move(data), version, &StructuredCloneHolder::sCallbacks);

  return true;
}

bool StructuredCloneBlob::WriteStructuredClone(JSContext* aCx,
                                               JSStructuredCloneWriter* aWriter,
                                               StructuredCloneHolder* aHolder) {
  if (mHolder.isNothing()) {
    return false;
  }
  return mHolder->WriteStructuredClone(aCx, aWriter, aHolder);
}

bool StructuredCloneBlob::Holder::WriteStructuredClone(
    JSContext* aCx, JSStructuredCloneWriter* aWriter,
    StructuredCloneHolder* aHolder) {
  auto& data = mBuffer->data();
  if (!JS_WriteUint32Pair(aWriter, SCTAG_DOM_STRUCTURED_CLONE_HOLDER, 0) ||
      !JS_WriteUint32Pair(aWriter, data.Size(), JS_STRUCTURED_CLONE_VERSION) ||
      !JS_WriteUint32Pair(aWriter, aHolder->BlobImpls().Length(),
                          BlobImpls().Length())) {
    return false;
  }

  aHolder->BlobImpls().AppendElements(BlobImpls());

  return data.ForEachDataChunk([&](const char* aData, size_t aSize) {
    return JS_WriteBytes(aWriter, aData, aSize);
  });
}

bool StructuredCloneBlob::WrapObject(JSContext* aCx,
                                     JS::Handle<JSObject*> aGivenProto,
                                     JS::MutableHandle<JSObject*> aResult) {
  return StructuredCloneHolder_Binding::Wrap(aCx, this, aGivenProto, aResult);
}

NS_IMETHODIMP
StructuredCloneBlob::CollectReports(nsIHandleReportCallback* aHandleReport,
                                    nsISupports* aData, bool aAnonymize) {
  size_t size = MallocSizeOf(this);
  if (mHolder.isSome()) {
    size += mHolder->SizeOfExcludingThis(MallocSizeOf);
  }

  MOZ_COLLECT_REPORT("explicit/dom/structured-clone-holder", KIND_HEAP,
                     UNITS_BYTES, size,
                     "Memory used by StructuredCloneHolder DOM objects.");

  return NS_OK;
}

NS_IMPL_ISUPPORTS(StructuredCloneBlob, nsIMemoryReporter)

}  // namespace mozilla::dom