path: root/chrome/nacl/nacl_ipc_adapter.cc

// Copyright (c) 2012 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 "chrome/nacl/nacl_ipc_adapter.h"

#include <limits.h>
#include <string.h>

#include "base/basictypes.h"
#include "base/bind.h"
#include "base/location.h"
#include "base/memory/scoped_ptr.h"
#include "build/build_config.h"

namespace {

enum BufferSizeStatus {
  // The buffer contains a full message with no extra bytes.
  MESSAGE_IS_COMPLETE,

  // The message doesn't fit and the buffer contains only some of it.
  MESSAGE_IS_TRUNCATED,

  // The buffer contains a full message + extra data.
  MESSAGE_HAS_EXTRA_DATA
};

BufferSizeStatus GetBufferStatus(const char* data, size_t len) {
  if (len < sizeof(NaClIPCAdapter::NaClMessageHeader))
    return MESSAGE_IS_TRUNCATED;

  const NaClIPCAdapter::NaClMessageHeader* header =
      reinterpret_cast<const NaClIPCAdapter::NaClMessageHeader*>(data);
  uint32 message_size =
      sizeof(NaClIPCAdapter::NaClMessageHeader) + header->payload_size;

  if (len == message_size)
    return MESSAGE_IS_COMPLETE;
  if (len > message_size)
    return MESSAGE_HAS_EXTRA_DATA;
  return MESSAGE_IS_TRUNCATED;
}

}  // namespace

class NaClIPCAdapter::RewrittenMessage
    : public base::RefCounted<RewrittenMessage> {
 public:
  RewrittenMessage();

  bool is_consumed() const { return data_read_cursor_ == data_len_; }

  void SetData(const NaClIPCAdapter::NaClMessageHeader& header,
               const void* payload, size_t payload_length);

  int Read(char* dest_buffer, int dest_buffer_size);

 private:
  friend class base::RefCounted<RewrittenMessage>;
  ~RewrittenMessage() {}

  scoped_array<char> data_;
  int data_len_;

  // Offset into data where the next read will happen. This will be equal to
  // data_len_ when all data has been consumed.
  int data_read_cursor_;
};

NaClIPCAdapter::RewrittenMessage::RewrittenMessage()
    : data_len_(0),
      data_read_cursor_(0) {
}

void NaClIPCAdapter::RewrittenMessage::SetData(
    const NaClIPCAdapter::NaClMessageHeader& header,
    const void* payload,
    size_t payload_length) {
  DCHECK(!data_.get() && data_len_ == 0);
  int header_len = sizeof(NaClIPCAdapter::NaClMessageHeader);
  data_len_ = header_len + static_cast<int>(payload_length);
  data_.reset(new char[data_len_]);

  memcpy(data_.get(), &header, sizeof(NaClIPCAdapter::NaClMessageHeader));
  memcpy(&data_[header_len], payload, payload_length);
}

int NaClIPCAdapter::RewrittenMessage::Read(char* dest_buffer,
                                           int dest_buffer_size) {
  int bytes_to_write = std::min(dest_buffer_size,
                                data_len_ - data_read_cursor_);
  if (bytes_to_write == 0)
    return 0;

  memcpy(dest_buffer, &data_[data_read_cursor_], bytes_to_write);
  data_read_cursor_ += bytes_to_write;
  return bytes_to_write;
}

NaClIPCAdapter::LockedData::LockedData() : channel_closed_(false) {
}

NaClIPCAdapter::LockedData::~LockedData() {
}

NaClIPCAdapter::IOThreadData::IOThreadData() {
}

NaClIPCAdapter::IOThreadData::~IOThreadData() {
}

NaClIPCAdapter::NaClIPCAdapter(const IPC::ChannelHandle& handle,
                               base::TaskRunner* runner)
    : lock_(),
      cond_var_(&lock_),
      task_runner_(runner),
      locked_data_() {
  io_thread_data_.channel_.reset(
      new IPC::Channel(handle, IPC::Channel::MODE_SERVER, this));
}

NaClIPCAdapter::NaClIPCAdapter(scoped_ptr<IPC::Channel> channel,
                               base::TaskRunner* runner)
    : lock_(),
      cond_var_(&lock_),
      task_runner_(runner),
      locked_data_() {
  io_thread_data_.channel_ = channel.Pass();
}

// Note that this message is controlled by the untrusted code. So we should be
// skeptical of anything it contains and quick to give up if anything is fishy.
int NaClIPCAdapter::Send(const char* input_data, size_t input_data_len) {
  base::AutoLock lock(lock_);

  if (input_data_len > IPC::Channel::kMaximumMessageSize) {
    ClearToBeSent();
    return -1;
  }

  // current_message[_len] refers to the total input data received so far.
  const char* current_message;
  size_t current_message_len;
  bool did_append_input_data;
  if (locked_data_.to_be_sent_.empty()) {
    // No accumulated data, we can avoid a copy by referring to the input
    // buffer (the entire message fitting in one call is the common case).
    current_message = input_data;
    current_message_len = input_data_len;
    did_append_input_data = false;
  } else {
    // We've already accumulated some data, accumulate this new data and
    // point to the beginning of the buffer.

    // Make sure our accumulated message size doesn't overflow our max. Since
    // we know that data_len < max size (checked above) and our current
    // accumulated value is also < max size, we just need to make sure that
    // 2x max size can never overflow.
    COMPILE_ASSERT(IPC::Channel::kMaximumMessageSize < (UINT_MAX / 2),
                   MaximumMessageSizeWillOverflow);
    size_t new_size = locked_data_.to_be_sent_.size() + input_data_len;
    if (new_size > IPC::Channel::kMaximumMessageSize) {
      ClearToBeSent();
      return -1;
    }

    locked_data_.to_be_sent_.append(input_data, input_data_len);
    current_message = &locked_data_.to_be_sent_[0];
    current_message_len = locked_data_.to_be_sent_.size();
    did_append_input_data = true;
  }

  // Check the total data we've accumulated so far to see if it contains a full
  // message.
  switch (GetBufferStatus(current_message, current_message_len)) {
    case MESSAGE_IS_COMPLETE: {
      // Got a complete message, can send it out. This will be the common case.
      bool success = SendCompleteMessage(current_message, current_message_len);
      ClearToBeSent();
      return success ? static_cast<int>(input_data_len) : -1;
    }
    case MESSAGE_IS_TRUNCATED:
      // For truncated messages, just accumulate the new data (if we didn't
      // already do so above) and go back to waiting for more.
      if (!did_append_input_data)
        locked_data_.to_be_sent_.append(input_data, input_data_len);
      return static_cast<int>(input_data_len);
    case MESSAGE_HAS_EXTRA_DATA:
    default:
      // When the plugin gives us too much data, it's an error.
      ClearToBeSent();
      return -1;
  }
}

int NaClIPCAdapter::BlockingReceive(char* output_buffer,
                                    int output_buffer_size) {
  int retval = 0;
  {
    base::AutoLock lock(lock_);
    while (locked_data_.to_be_received_.empty() &&
           !locked_data_.channel_closed_)
      cond_var_.Wait();
    if (locked_data_.channel_closed_) {
      retval = -1;
    } else {
      retval = LockedReceive(output_buffer, output_buffer_size);
      DCHECK(retval > 0);
    }
  }
  cond_var_.Signal();
  return retval;
}

void NaClIPCAdapter::CloseChannel() {
  {
    base::AutoLock lock(lock_);
    locked_data_.channel_closed_ = true;
  }
  cond_var_.Signal();

  task_runner_->PostTask(FROM_HERE,
      base::Bind(&NaClIPCAdapter::CloseChannelOnIOThread, this));
}

bool NaClIPCAdapter::OnMessageReceived(const IPC::Message& message) {
  {
    base::AutoLock lock(lock_);

    // There is some padding in this structure (the "padding" member is 16
    // bits but this then gets padded to 32 bits). We want to be sure not to
    // leak data to the untrusted plugin, so zero everything out first.
    NaClMessageHeader header;
    memset(&header, 0, sizeof(NaClMessageHeader));

    header.payload_size = static_cast<uint32>(message.payload_size());
    header.routing = message.routing_id();
    header.type = message.type();
    header.flags = message.flags();
    header.num_fds = 0;  // TODO(brettw) hook this up.

    scoped_refptr<RewrittenMessage> dest(new RewrittenMessage);
    dest->SetData(header, message.payload(), message.payload_size());
    locked_data_.to_be_received_.push(dest);
  }
  cond_var_.Signal();
  return true;
}

void NaClIPCAdapter::OnChannelConnected(int32 peer_pid) {
}

void NaClIPCAdapter::OnChannelError() {
  CloseChannel();
}

NaClIPCAdapter::~NaClIPCAdapter() {
}

int NaClIPCAdapter::LockedReceive(char* output_buffer, int output_buffer_size) {
  lock_.AssertAcquired();

  if (locked_data_.to_be_received_.empty())
    return 0;
  scoped_refptr<RewrittenMessage> current =
      locked_data_.to_be_received_.front();

  int retval = current->Read(output_buffer, output_buffer_size);

  // When a message is entirely consumed, remove if from the waiting queue.
  if (current->is_consumed())
    locked_data_.to_be_received_.pop();
  return retval;
}

bool NaClIPCAdapter::SendCompleteMessage(const char* buffer,
                                         size_t buffer_len) {
  // The message will have already been validated, so we know it's large enough
  // for our header.
  const NaClMessageHeader* header =
      reinterpret_cast<const NaClMessageHeader*>(buffer);

  // Length of the message not including the body. The data passed to us by the
  // plugin should match that in the message header. This should have already
  // been validated by GetBufferStatus.
  int body_len = static_cast<int>(buffer_len - sizeof(NaClMessageHeader));
  DCHECK(body_len == static_cast<int>(header->payload_size));

  // We actually discard the flags and only copy the ones we care about. This
  // is just because message doesn't have a constructor that takes raw flags.
  scoped_ptr<IPC::Message> msg(
      new IPC::Message(header->routing, header->type,
                       IPC::Message::PRIORITY_NORMAL));
  if (header->flags & IPC::Message::SYNC_BIT)
    msg->set_sync();
  if (header->flags & IPC::Message::REPLY_BIT)
    msg->set_reply();
  if (header->flags & IPC::Message::REPLY_ERROR_BIT)
    msg->set_reply_error();
  if (header->flags & IPC::Message::UNBLOCK_BIT)
    msg->set_unblock(true);

  msg->WriteBytes(&buffer[sizeof(NaClMessageHeader)], body_len);

  // Technically we didn't have to do any of the previous work in the lock. But
  // sometimes our buffer will point to the to_be_sent_ string which is
  // protected by the lock, and it's messier to factor Send() such that it can
  // unlock for us. Holding the lock for the message construction, which is
  // just some memcpys, shouldn't be a big deal.
  lock_.AssertAcquired();
  if (locked_data_.channel_closed_)
    return false;  // TODO(brettw) clean up handles here when we add support!

  // Actual send must be done on the I/O thread.
  task_runner_->PostTask(FROM_HERE,
      base::Bind(&NaClIPCAdapter::SendMessageOnIOThread, this,
                 base::Passed(&msg)));
  return true;
}

void NaClIPCAdapter::ClearToBeSent() {
  lock_.AssertAcquired();

  // Don't let the string keep its buffer behind our back.
  std::string empty;
  locked_data_.to_be_sent_.swap(empty);
}

void NaClIPCAdapter::CloseChannelOnIOThread() {
  io_thread_data_.channel_->Close();
}

void NaClIPCAdapter::SendMessageOnIOThread(scoped_ptr<IPC::Message> message) {
  io_thread_data_.channel_->Send(message.release());
}