path: root/ipc/chromium/src/base/pickle.cc

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/pickle.h"

#include "mozilla/Alignment.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/EndianUtils.h"
#include "mozilla/Telemetry.h"
#include "mozilla/ipc/ProtocolUtils.h"

#include <stdlib.h>

#include <limits>
#include <string>
#include <algorithm>
#include <type_traits>

#include "nsDebug.h"

//------------------------------------------------------------------------------

static_assert(MOZ_ALIGNOF(Pickle::memberAlignmentType) >= MOZ_ALIGNOF(uint32_t),
              "Insufficient alignment");

static const uint32_t kHeaderSegmentCapacity = 64;

static const uint32_t kDefaultSegmentCapacity = 4096;

static const char kBytePaddingMarker = char(0xbf);

namespace {

// We want to copy data to our payload as efficiently as possible.
// memcpy fits the bill for copying, but not all compilers or
// architectures support inlining memcpy from void*, which has unknown
// static alignment.  However, we know that all the members of our
// payload will be aligned on memberAlignmentType boundaries.  We
// therefore use that knowledge to construct a copier that will copy
// efficiently (via standard C++ assignment mechanisms) if the datatype
// needs that alignment or less, and memcpy otherwise.  (The compiler
// may still inline memcpy, of course.)

template <typename T, size_t size, bool hasSufficientAlignment>
struct Copier {
  static void Copy(T* dest, const char* iter) { memcpy(dest, iter, sizeof(T)); }
};

// Copying 64-bit quantities happens often enough and can easily be made
// worthwhile on 32-bit platforms, so handle it specially.  Only do it
// if 64-bit types aren't sufficiently aligned; the alignment
// requirements for them vary between 32-bit platforms.
#ifndef HAVE_64BIT_BUILD
template <typename T>
struct Copier<T, sizeof(uint64_t), false> {
  static void Copy(T* dest, const char* iter) {
#  if MOZ_LITTLE_ENDIAN
    static const int loIndex = 0, hiIndex = 1;
#  else
    static const int loIndex = 1, hiIndex = 0;
#  endif
    static_assert(MOZ_ALIGNOF(uint32_t*) == MOZ_ALIGNOF(void*),
                  "Pointers have different alignments");
    const uint32_t* src = reinterpret_cast<const uint32_t*>(iter);
    uint32_t* uint32dest = reinterpret_cast<uint32_t*>(dest);
    uint32dest[loIndex] = src[loIndex];
    uint32dest[hiIndex] = src[hiIndex];
  }
};
#endif

template <typename T, size_t size>
struct Copier<T, size, true> {
  static void Copy(T* dest, const char* iter) {
    // The pointer ought to be properly aligned.
    DCHECK_EQ((((uintptr_t)iter) & (MOZ_ALIGNOF(T) - 1)), 0);
    *dest = *reinterpret_cast<const T*>(iter);
  }
};

}  // anonymous namespace

PickleIterator::PickleIterator(const Pickle& pickle)
    : iter_(pickle.buffers_.Iter()) {
  iter_.Advance(pickle.buffers_, pickle.header_size_);
}

template <typename T>
void PickleIterator::CopyInto(T* dest) {
  static_assert(std::is_trivially_copyable<T>::value,
                "Copied type must be a POD type");
  Copier<T, sizeof(T),
         (MOZ_ALIGNOF(T) <=
          sizeof(Pickle::memberAlignmentType))>::Copy(dest, iter_.Data());
}

bool Pickle::IteratorHasRoomFor(const PickleIterator& iter,
                                uint32_t len) const {
  // Make sure we don't get into trouble where AlignInt(len) == 0.
  MOZ_RELEASE_ASSERT(len < 64);

  return iter.iter_.HasRoomFor(AlignInt(len));
}

bool Pickle::HasBytesAvailable(const PickleIterator* iter, uint32_t len) const {
  return iter->iter_.HasBytesAvailable(buffers_, len);
}

void Pickle::UpdateIter(PickleIterator* iter, uint32_t bytes) const {
  // Make sure we don't get into trouble where AlignInt(bytes) == 0.
  MOZ_RELEASE_ASSERT(bytes < 64);

  iter->iter_.Advance(buffers_, AlignInt(bytes));
}

// Payload is sizeof(Pickle::memberAlignmentType) aligned.

Pickle::Pickle(uint32_t header_size, size_t segment_capacity)
    : buffers_(AlignInt(header_size),
               segment_capacity ? segment_capacity : kHeaderSegmentCapacity,
               segment_capacity ? segment_capacity : kDefaultSegmentCapacity),
      header_(nullptr),
      header_size_(AlignInt(header_size)) {
  DCHECK(static_cast<memberAlignmentType>(header_size) >= sizeof(Header));
  DCHECK(header_size_ <= kHeaderSegmentCapacity);
  header_ = reinterpret_cast<Header*>(buffers_.Start());
  header_->payload_size = 0;
}

Pickle::Pickle(uint32_t header_size, const char* data, uint32_t length)
    : buffers_(length, AlignCapacity(length), kDefaultSegmentCapacity),
      header_(nullptr),
      header_size_(AlignInt(header_size)) {
  DCHECK(static_cast<memberAlignmentType>(header_size) >= sizeof(Header));
  DCHECK(header_size <= kHeaderSegmentCapacity);
  MOZ_RELEASE_ASSERT(header_size <= length);

  header_ = reinterpret_cast<Header*>(buffers_.Start());
  memcpy(header_, data, length);
}

Pickle::Pickle(Pickle&& other)
    : buffers_(std::move(other.buffers_)),
      header_(other.header_),
      header_size_(other.header_size_) {
  other.header_ = nullptr;
}

Pickle::~Pickle() {}

Pickle& Pickle::operator=(Pickle&& other) {
  BufferList tmp = std::move(other.buffers_);
  other.buffers_ = std::move(buffers_);
  buffers_ = std::move(tmp);

  // std::swap(buffers_, other.buffers_);
  std::swap(header_, other.header_);
  std::swap(header_size_, other.header_size_);
  return *this;
}

void Pickle::CopyFrom(const Pickle& other) {
  MOZ_ALWAYS_TRUE(buffers_.CopyFrom(other.buffers_));
  MOZ_ASSERT(other.header_ ==
             reinterpret_cast<const Header*>(other.buffers_.Start()));

  header_ = reinterpret_cast<Header*>(buffers_.Start());
  header_size_ = other.header_size_;
}

bool Pickle::ReadBool(PickleIterator* iter, bool* result) const {
  int tmp;
  if (!ReadScalar(iter, &tmp)) return false;

  DCHECK(0 == tmp || 1 == tmp);
  *result = tmp ? true : false;

  return true;
}

bool Pickle::ReadInt16(PickleIterator* iter, int16_t* result) const {
  return ReadScalar(iter, result);
}

bool Pickle::ReadUInt16(PickleIterator* iter, uint16_t* result) const {
  return ReadScalar(iter, result);
}

bool Pickle::ReadInt(PickleIterator* iter, int* result) const {
  return ReadScalar(iter, result);
}

// Always written as a 64-bit value since the size for this type can
// differ between architectures.
bool Pickle::ReadLong(PickleIterator* iter, long* result) const {
  int64_t big_result;
  if (!ReadScalar(iter, &big_result)) return false;

  DCHECK(big_result <= LONG_MAX && big_result >= LONG_MIN);
  *result = static_cast<long>(big_result);

  return true;
}

// Always written as a 64-bit value since the size for this type can
// differ between architectures.
bool Pickle::ReadULong(PickleIterator* iter, unsigned long* result) const {
  uint64_t big_result;
  if (!ReadScalar(iter, &big_result)) return false;
  DCHECK(big_result <= ULONG_MAX);
  *result = static_cast<unsigned long>(big_result);

  return true;
}

bool Pickle::ReadLength(PickleIterator* iter, int* result) const {
  if (!ReadScalar(iter, result)) return false;
  return ((*result) >= 0);
}

bool Pickle::ReadInt32(PickleIterator* iter, int32_t* result) const {
  return ReadScalar(iter, result);
}

bool Pickle::ReadUInt32(PickleIterator* iter, uint32_t* result) const {
  return ReadScalar(iter, result);
}

bool Pickle::ReadInt64(PickleIterator* iter, int64_t* result) const {
  return ReadScalar(iter, result);
}

bool Pickle::ReadUInt64(PickleIterator* iter, uint64_t* result) const {
  return ReadScalar(iter, result);
}

bool Pickle::ReadDouble(PickleIterator* iter, double* result) const {
  return ReadScalar(iter, result);
}

// Always written as a 64-bit value since the size for this type can
// differ between architectures.
bool Pickle::ReadIntPtr(PickleIterator* iter, intptr_t* result) const {
  DCHECK(iter);

  int64_t big_result;
  if (!ReadScalar(iter, &big_result)) return false;

  DCHECK(big_result <= std::numeric_limits<intptr_t>::max() &&
         big_result >= std::numeric_limits<intptr_t>::min());
  *result = static_cast<intptr_t>(big_result);

  return true;
}

bool Pickle::ReadUnsignedChar(PickleIterator* iter,
                              unsigned char* result) const {
  return ReadScalar(iter, result);
}

bool Pickle::ReadString(PickleIterator* iter, std::string* result) const {
  DCHECK(iter);

  int len;
  if (!ReadLength(iter, &len)) return false;

  auto chars = mozilla::MakeUnique<char[]>(len);
  if (!ReadBytesInto(iter, chars.get(), len)) {
    return false;
  }
  result->assign(chars.get(), len);

  return true;
}

bool Pickle::ReadWString(PickleIterator* iter, std::wstring* result) const {
  DCHECK(iter);

  int len;
  if (!ReadLength(iter, &len)) return false;
  // Avoid integer multiplication overflow.
  if (len > INT_MAX / static_cast<int>(sizeof(wchar_t))) return false;

  auto chars = mozilla::MakeUnique<wchar_t[]>(len);
  if (!ReadBytesInto(iter, chars.get(), len * sizeof(wchar_t))) {
    return false;
  }
  result->assign(chars.get(), len);

  return true;
}

bool Pickle::ReadBytesInto(PickleIterator* iter, void* data,
                           uint32_t length) const {
  if (AlignInt(length) < length) {
    return false;
  }

  if (!buffers_.ReadBytes(iter->iter_, reinterpret_cast<char*>(data), length)) {
    return false;
  }

  return iter->iter_.AdvanceAcrossSegments(buffers_, AlignInt(length) - length);
}

bool Pickle::IgnoreBytes(PickleIterator* iter, uint32_t length) const {
  if (AlignInt(length) < length) {
    return false;
  }

  return iter->iter_.AdvanceAcrossSegments(buffers_, AlignInt(length));
}

#ifdef MOZ_PICKLE_SENTINEL_CHECKING
MOZ_NEVER_INLINE
bool Pickle::ReadSentinel(PickleIterator* iter, uint32_t sentinel) const {
  uint32_t found;
  if (!ReadScalar(iter, &found)) {
    return false;
  }
  return found == sentinel;
}

bool Pickle::IgnoreSentinel(PickleIterator* iter) const {
  uint32_t found;
  return ReadUInt32(iter, &found);
}

bool Pickle::WriteSentinel(uint32_t sentinel) { return WriteUInt32(sentinel); }
#endif

void Pickle::EndRead(PickleIterator& iter, uint32_t ipcMsgType) const {
  // FIXME: Deal with the footer somehow...
  // DCHECK(iter.iter_.Done());
}

void Pickle::Truncate(PickleIterator* iter) {
  size_t dropped = buffers_.Truncate(iter->iter_);
  header_->payload_size -= dropped;
}

static const char kBytePaddingData[4] = {
    kBytePaddingMarker,
    kBytePaddingMarker,
    kBytePaddingMarker,
    kBytePaddingMarker,
};

static void WritePadding(Pickle::BufferList& buffers, uint32_t padding) {
  MOZ_RELEASE_ASSERT(padding <= 4);
  if (padding) {
    MOZ_ALWAYS_TRUE(buffers.WriteBytes(kBytePaddingData, padding));
  }
}

void Pickle::BeginWrite(uint32_t length) {
  // write at an alignment-aligned offset from the beginning of the header
  uint32_t offset = AlignInt(header_->payload_size);
  uint32_t padding = (header_size_ + offset) % sizeof(memberAlignmentType);
  uint32_t new_size = offset + padding + AlignInt(length);
  MOZ_RELEASE_ASSERT(new_size >= header_->payload_size);

  DCHECK(intptr_t(header_) % sizeof(memberAlignmentType) == 0);

#ifdef HAVE_64BIT_BUILD
  DCHECK_LE(length, std::numeric_limits<uint32_t>::max());
#endif

  WritePadding(buffers_, padding);

  DCHECK((header_size_ + header_->payload_size + padding) %
             sizeof(memberAlignmentType) ==
         0);

  header_->payload_size = new_size;
}

void Pickle::EndWrite(uint32_t length) {
  uint32_t padding = AlignInt(length) - length;
  WritePadding(buffers_, padding);
}

bool Pickle::WriteBool(bool value) { return WriteInt(value ? 1 : 0); }

bool Pickle::WriteInt16(int16_t value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteUInt16(uint16_t value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteInt(int value) { return WriteBytes(&value, sizeof(value)); }

bool Pickle::WriteLong(long value) {
  // Always written as a 64-bit value since the size for this type can
  // differ between architectures.
  return WriteInt64(int64_t(value));
}

bool Pickle::WriteULong(unsigned long value) {
  // Always written as a 64-bit value since the size for this type can
  // differ between architectures.
  return WriteUInt64(uint64_t(value));
}

bool Pickle::WriteInt32(int32_t value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteUInt32(uint32_t value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteInt64(int64_t value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteUInt64(uint64_t value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteDouble(double value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteIntPtr(intptr_t value) {
  // Always written as a 64-bit value since the size for this type can
  // differ between architectures.
  return WriteInt64(int64_t(value));
}

bool Pickle::WriteUnsignedChar(unsigned char value) {
  return WriteBytes(&value, sizeof(value));
}

bool Pickle::WriteBytesZeroCopy(void* data, uint32_t data_len,
                                uint32_t capacity) {
  BeginWrite(data_len);

  uint32_t new_capacity = AlignInt(capacity);
#ifndef MOZ_MEMORY
  if (new_capacity > capacity) {
    // If the buffer we were given is not large enough to contain padding
    // after the data, reallocate it to make it so. When using jemalloc,
    // we're guaranteed the buffer size is going to be at least 4-bytes
    // aligned, so we skip realloc altogether. Even with other allocators,
    // the realloc is likely not necessary, but we don't take chances.
    // At least with ASan, it does matter to realloc to inform ASan we're
    // going to use more data from the buffer (and let it actually realloc
    // if it needs to).
    data = realloc(data, new_capacity);
  }
#endif

  // Shouldn't fail, because we're using InfallibleAllocPolicy.
  MOZ_ALWAYS_TRUE(buffers_.WriteBytesZeroCopy(reinterpret_cast<char*>(data),
                                              data_len, new_capacity));

  EndWrite(data_len);
  return true;
}

bool Pickle::WriteBytes(const void* data, uint32_t data_len) {
  BeginWrite(data_len);

  MOZ_ALWAYS_TRUE(
      buffers_.WriteBytes(reinterpret_cast<const char*>(data), data_len));

  EndWrite(data_len);
  return true;
}

bool Pickle::WriteString(const std::string& value) {
  if (!WriteInt(static_cast<int>(value.size()))) return false;

  return WriteBytes(value.data(), static_cast<int>(value.size()));
}

bool Pickle::WriteWString(const std::wstring& value) {
  if (!WriteInt(static_cast<int>(value.size()))) return false;

  return WriteBytes(value.data(),
                    static_cast<int>(value.size() * sizeof(wchar_t)));
}

bool Pickle::WriteData(const char* data, uint32_t length) {
  return WriteInt(length) && WriteBytes(data, length);
}

void Pickle::InputBytes(const char* data, uint32_t length) {
  MOZ_ALWAYS_TRUE(buffers_.WriteBytes(data, length));
}

int32_t* Pickle::GetInt32PtrForTest(uint32_t offset) {
  size_t pos = buffers_.Size() - offset;
  BufferList::IterImpl iter(buffers_);
  MOZ_RELEASE_ASSERT(iter.AdvanceAcrossSegments(buffers_, pos));
  return reinterpret_cast<int32_t*>(iter.Data());
}

// static
uint32_t Pickle::MessageSize(uint32_t header_size, const char* start,
                             const char* end) {
  DCHECK(header_size == AlignInt(header_size));
  DCHECK(header_size <=
         static_cast<memberAlignmentType>(kHeaderSegmentCapacity));

  if (end < start) return 0;
  size_t length = static_cast<size_t>(end - start);
  if (length < sizeof(Header)) return 0;

  const Header* hdr = reinterpret_cast<const Header*>(start);
  if (length < header_size) return 0;

  mozilla::CheckedInt<uint32_t> sum(header_size);
  sum += hdr->payload_size;

  if (!sum.isValid()) return 0;

  return sum.value();
}