Initial implementation of an IPC adapter to expose Chrome IPC to Native Client.

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 {
+
+// The NaCl message header type is always like Posix. So when we're compiling
+// on Posix platforms, we can check that our header is correct.
+#if defined(OS_POSIX)
+COMPILE_ASSERT(sizeof(NaClIPCAdapter::NaClMessageHeader) ==
+               sizeof(IPC::Message::Header),
+               PosixHeaderSizesDontMatch);
+#endif
+
+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.
+  BUFFER_UNDERFLOW
+};
+
+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 BUFFER_UNDERFLOW;
+  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:
+  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::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();
+}
+
+NaClIPCAdapter::~NaClIPCAdapter() {
+}
+
+// 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;
+  }
+
+  const char* current_message = input_data;
+  size_t current_message_len = input_data_len;
+  if (!locked_data_.to_be_sent_.empty()) {
+    // We've already accumulated some data.
+
+    // 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();
+  }
+
+  // Nothing accumulated, so see if the input data contains a full message.

[bbudge, 2012/03/26 22:52:30]

Something seems wrong here. The above 'if' block will drop down here after
adding the data.

[brettw, 2012/03/27 17:40:27]

The comment was misleading but I think the code was correct. I moved things
around a bit and fixed the comments, hopefully it's more clear now.

+  // This will be the common case.
+  switch (GetBufferStatus(current_message, current_message_len)) {
+    case MESSAGE_IS_COMPLETE: {
+      // Got a complete message, can send it out.
+      bool success = SendCompleteMessage(current_message, current_message_len);
+      ClearToBeSent();
+      return success ? input_data_len : -1;
+    }
+    case MESSAGE_IS_TRUNCATED:
+      // For truncated messages, just accumulate the new data and go back to
+      // waiting for more.
+      locked_data_.to_be_sent_.append(input_data, input_data_len);

[bbudge, 2012/03/26 22:52:30]

Seems like data could get added twice.

[brettw, 2012/03/27 17:40:27]

Whoops! Nice catch. I modified the test to send in 3 chunks to catch this.

+      return input_data_len;
+    case BUFFER_UNDERFLOW:
+    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 memory to the untrusted plugin, so zero everything out first.

[bbudge, 2012/03/26 22:52:30]

Maybe memory -> data so it doesn't sound like a memory leak?

+    NaClMessageHeader header;
+    memset(&header, 0, sizeof(NaClMessageHeader));
+
+    header.payload_size = 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();
+}
+
+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 = 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 out buffer will point to the to_be_sent_ string which is

[bbudge, 2012/03/26 22:52:30]

s/out/our

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