attachment_broker_privileged_mac.cc

// Copyright 2015 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 "ipc/attachment_broker_privileged_mac.h"

#include "base/mac/scoped_mach_port.h"
#include "base/memory/shared_memory.h"
#include "base/process/port_provider_mac.h"
#include "base/process/process.h"
#include "base/synchronization/lock.h"
#include "ipc/attachment_broker_messages.h"
#include "ipc/brokerable_attachment.h"
#include "ipc/ipc_channel.h"
#include "ipc/mach_port_attachment_mac.h"

namespace {

// Struct for sending a complex Mach message.
struct MachSendComplexMessage {
  mach_msg_header_t header;
  mach_msg_body_t body;
  mach_msg_port_descriptor_t data;
};

// Sends a Mach port to |endpoint|. Assumes that |endpoint| is a send once
// right. Takes ownership of |endpoint|.
kern_return_t SendMachPort(mach_port_t endpoint,
                           mach_port_t port_to_send,
                           int disposition) {
  MachSendComplexMessage send_msg;
  send_msg.header.msgh_bits =
      MACH_MSGH_BITS(MACH_MSG_TYPE_MOVE_SEND_ONCE, 0) | MACH_MSGH_BITS_COMPLEX;
  send_msg.header.msgh_size = sizeof(send_msg);
  send_msg.header.msgh_remote_port = endpoint;
  send_msg.header.msgh_local_port = MACH_PORT_NULL;
  send_msg.header.msgh_reserved = 0;
  send_msg.header.msgh_id = 0;
  send_msg.body.msgh_descriptor_count = 1;
  send_msg.data.name = port_to_send;
  send_msg.data.disposition = disposition;
  send_msg.data.type = MACH_MSG_PORT_DESCRIPTOR;

  kern_return_t kr =
      mach_msg(&send_msg.header, MACH_SEND_MSG | MACH_SEND_TIMEOUT,
               send_msg.header.msgh_size,
               0,                // receive limit
               MACH_PORT_NULL,   // receive name
               0,                // timeout
               MACH_PORT_NULL);  // notification port

  if (kr != KERN_SUCCESS)
    mach_port_deallocate(mach_task_self(), endpoint);

  return kr;
}

}  // namespace

namespace IPC {

AttachmentBrokerPrivilegedMac::AttachmentBrokerPrivilegedMac(
    base::PortProvider* port_provider)
    : port_provider_(port_provider) {
  port_provider_->AddObserver(this);
}

AttachmentBrokerPrivilegedMac::~AttachmentBrokerPrivilegedMac() {
  port_provider_->RemoveObserver(this);
  {
    base::AutoLock l(precursors_lock_);
    for (auto it : precursors_)
      delete it.second;
  }
  {
    base::AutoLock l(extractors_lock_);
    for (auto it : extractors_)
      delete it.second;
  }
}

bool AttachmentBrokerPrivilegedMac::SendAttachmentToProcess(
    const scoped_refptr<IPC::BrokerableAttachment>& attachment,
    base::ProcessId destination_process) {
  switch (attachment->GetBrokerableType()) {
    case BrokerableAttachment::MACH_PORT: {
      internal::MachPortAttachmentMac* mach_port_attachment =
          static_cast<internal::MachPortAttachmentMac*>(attachment.get());
      MachPortWireFormat wire_format =
          mach_port_attachment->GetWireFormat(destination_process);
      AddPrecursor(wire_format.destination_process,
                   base::mac::ScopedMachSendRight(wire_format.mach_port),
                   wire_format.attachment_id);
      mach_port_attachment->reset_mach_port_ownership();
      SendPrecursorsForProcess(wire_format.destination_process);
      return true;
    }
    default:
      NOTREACHED();
      return false;
  }
  return false;
}

void AttachmentBrokerPrivilegedMac::DeregisterCommunicationChannel(
    Endpoint* endpoint) {
  AttachmentBrokerPrivileged::DeregisterCommunicationChannel(endpoint);

  if (!endpoint)
    return;

  base::ProcessId pid = endpoint->GetPeerPID();
  if (pid == base::kNullProcessId)
    return;

  {
    base::AutoLock l(precursors_lock_);
    auto it = precursors_.find(pid);
    if (it != precursors_.end()) {
      delete it->second;
      precursors_.erase(pid);
    }
  }

  {
    base::AutoLock l(extractors_lock_);
    auto it = extractors_.find(pid);
    if (it != extractors_.end()) {
      delete it->second;
      extractors_.erase(pid);
    }
  }
}

bool AttachmentBrokerPrivilegedMac::OnMessageReceived(const Message& msg) {
  bool handled = true;
  switch (msg.type()) {
    IPC_MESSAGE_HANDLER_GENERIC(AttachmentBrokerMsg_DuplicateMachPort,
                                OnDuplicateMachPort(msg))
    IPC_MESSAGE_UNHANDLED(handled = false)
  }
  return handled;
}

void AttachmentBrokerPrivilegedMac::OnReceivedTaskPort(
    base::ProcessHandle process) {
  SendPrecursorsForProcess(process);
}

AttachmentBrokerPrivilegedMac::AttachmentPrecursor::AttachmentPrecursor(
    const base::ProcessId& pid,
    base::mac::ScopedMachSendRight port,
    const BrokerableAttachment::AttachmentId& id)
    : pid_(pid), port_(port.release()), id_(id) {}

AttachmentBrokerPrivilegedMac::AttachmentPrecursor::~AttachmentPrecursor() {}

base::mac::ScopedMachSendRight
AttachmentBrokerPrivilegedMac::AttachmentPrecursor::TakePort() {
  return base::mac::ScopedMachSendRight(port_.release());
}

AttachmentBrokerPrivilegedMac::AttachmentExtractor::AttachmentExtractor(
    const base::ProcessId& source_pid,
    const base::ProcessId& dest_pid,
    mach_port_name_t port,
    const BrokerableAttachment::AttachmentId& id)
    : source_pid_(source_pid),
      dest_pid_(dest_pid),
      port_to_extract_(port),
      id_(id) {}

AttachmentBrokerPrivilegedMac::AttachmentExtractor::~AttachmentExtractor() {}

void AttachmentBrokerPrivilegedMac::OnDuplicateMachPort(
    const IPC::Message& message) {
  DCHECK_NE(0, message.get_sender_pid());
  AttachmentBrokerMsg_DuplicateMachPort::Param param;
  if (!AttachmentBrokerMsg_DuplicateMachPort::Read(&message, &param)) {
    LogError(ERROR_PARSE_DUPLICATE_MACH_PORT_MESSAGE);
    return;
  }
  IPC::internal::MachPortAttachmentMac::WireFormat wire_format =
      base::get<0>(param);

  if (wire_format.destination_process == base::kNullProcessId) {
    LogError(NO_DESTINATION);
    return;
  }

  AddExtractor(message.get_sender_pid(), wire_format.destination_process,
               wire_format.mach_port, wire_format.attachment_id);
  ProcessExtractorsForProcess(message.get_sender_pid());
}

void AttachmentBrokerPrivilegedMac::RoutePrecursorToSelf(
    AttachmentPrecursor* precursor) {
  DCHECK_EQ(base::Process::Current().Pid(), precursor->pid());

  // Intentionally leak the port, since the attachment takes ownership.
  internal::MachPortAttachmentMac::WireFormat wire_format(
      precursor->TakePort().release(), precursor->pid(), precursor->id());
  scoped_refptr<BrokerableAttachment> attachment(
      new internal::MachPortAttachmentMac(wire_format));
  HandleReceivedAttachment(attachment);
}

bool AttachmentBrokerPrivilegedMac::RouteWireFormatToAnother(
    const MachPortWireFormat& wire_format) {
  DCHECK_NE(wire_format.destination_process, base::Process::Current().Pid());

  // Another process is the destination.
  base::ProcessId dest = wire_format.destination_process;
  base::AutoLock auto_lock(*get_lock());
  Sender* sender = GetSenderWithProcessId(dest);
  if (!sender) {
    // Assuming that this message was not sent from a malicious process, the
    // channel endpoint that would have received this message will block
    // forever.
    LOG(ERROR) << "Failed to deliver brokerable attachment to process with id: "
               << dest;
    LogError(DESTINATION_NOT_FOUND);
    return false;
  }

  LogError(DESTINATION_FOUND);
  sender->Send(new AttachmentBrokerMsg_MachPortHasBeenDuplicated(wire_format));
  return true;
}

mach_port_name_t AttachmentBrokerPrivilegedMac::CreateIntermediateMachPort(
    mach_port_t task_port,
    base::mac::ScopedMachSendRight port_to_insert) {
  DCHECK_NE(mach_task_self(), task_port);
  DCHECK_NE(static_cast<mach_port_name_t>(MACH_PORT_NULL), task_port);

  // Make a port with receive rights in the destination task.
  mach_port_name_t endpoint;
  kern_return_t kr =
      mach_port_allocate(task_port, MACH_PORT_RIGHT_RECEIVE, &endpoint);
  if (kr != KERN_SUCCESS) {
    LogError(ERROR_MAKE_RECEIVE_PORT);
    return MACH_PORT_NULL;
  }

  // Change its message queue limit so that it accepts one message.
  mach_port_limits limits = {};
  limits.mpl_qlimit = 1;
  kr = mach_port_set_attributes(task_port, endpoint, MACH_PORT_LIMITS_INFO,
                                reinterpret_cast<mach_port_info_t>(&limits),
                                MACH_PORT_LIMITS_INFO_COUNT);
  if (kr != KERN_SUCCESS) {
    LogError(ERROR_SET_ATTRIBUTES);
    mach_port_deallocate(task_port, endpoint);
    return MACH_PORT_NULL;
  }

  // Get a send right.
  mach_port_t send_once_right;
  mach_msg_type_name_t send_right_type;
  kr =
      mach_port_extract_right(task_port, endpoint, MACH_MSG_TYPE_MAKE_SEND_ONCE,
                              &send_once_right, &send_right_type);
  if (kr != KERN_SUCCESS) {
    LogError(ERROR_EXTRACT_DEST_RIGHT);
    mach_port_deallocate(task_port, endpoint);
    return MACH_PORT_NULL;
  }
  DCHECK_EQ(static_cast<mach_msg_type_name_t>(MACH_MSG_TYPE_PORT_SEND_ONCE),
            send_right_type);

  // This call takes ownership of |send_once_right|.
  kr = SendMachPort(
      send_once_right, port_to_insert.get(), MACH_MSG_TYPE_COPY_SEND);
  if (kr != KERN_SUCCESS) {
    LogError(ERROR_SEND_MACH_PORT);
    mach_port_deallocate(task_port, endpoint);
    return MACH_PORT_NULL;
  }

  // Endpoint is intentionally leaked into the destination task. An IPC must be
  // sent to the destination task so that it can clean up this port.
  return endpoint;
}

base::mac::ScopedMachSendRight AttachmentBrokerPrivilegedMac::ExtractNamedRight(
    mach_port_t task_port,
    mach_port_name_t named_right) {
  mach_port_t extracted_right = MACH_PORT_NULL;
  mach_msg_type_name_t extracted_right_type;
  kern_return_t kr =
      mach_port_extract_right(task_port, named_right, MACH_MSG_TYPE_MOVE_SEND,
                              &extracted_right, &extracted_right_type);
  if (kr != KERN_SUCCESS) {
    LogError(ERROR_EXTRACT_SOURCE_RIGHT);
    return base::mac::ScopedMachSendRight(MACH_PORT_NULL);
  }

  DCHECK_EQ(static_cast<mach_msg_type_name_t>(MACH_MSG_TYPE_PORT_SEND),
            extracted_right_type);

  return base::mac::ScopedMachSendRight(extracted_right);
}

AttachmentBrokerPrivilegedMac::MachPortWireFormat
AttachmentBrokerPrivilegedMac::CopyWireFormat(
    const MachPortWireFormat& wire_format,
    uint32_t mach_port) {
  return MachPortWireFormat(mach_port, wire_format.destination_process,
                            wire_format.attachment_id);
}

void AttachmentBrokerPrivilegedMac::SendPrecursorsForProcess(
    base::ProcessId pid) {
  base::AutoLock l(precursors_lock_);
  auto it = precursors_.find(pid);
  if (it == precursors_.end())
    return;

  // Whether this process is the destination process.
  bool to_self = pid == base::GetCurrentProcId();

  if (!to_self) {
    base::AutoLock auto_lock(*get_lock());
    if (!GetSenderWithProcessId(pid)) {
      // If there is no sender, then the destination process is no longer
      // running, or never existed to begin with.
      LogError(DESTINATION_NOT_FOUND);
      delete it->second;
      precursors_.erase(it);
      return;
    }
  }

  mach_port_t task_port = port_provider_->TaskForPid(pid);

  // It's possible that the destination process has not yet provided the
  // privileged process with its task port.
  if (!to_self && task_port == MACH_PORT_NULL)
    return;

  while (!it->second->empty()) {
    auto precursor_it = it->second->begin();
    if (to_self) {
      RoutePrecursorToSelf(*precursor_it);
    } else {
      if (!SendPrecursor(*precursor_it, task_port))
        break;
    }
    it->second->erase(precursor_it);
  }

  delete it->second;
  precursors_.erase(it);
}

bool AttachmentBrokerPrivilegedMac::SendPrecursor(
    AttachmentPrecursor* precursor,
    mach_port_t task_port) {
  DCHECK(task_port);
  internal::MachPortAttachmentMac::WireFormat wire_format(
      MACH_PORT_NULL, precursor->pid(), precursor->id());
  base::mac::ScopedMachSendRight port_to_insert = precursor->TakePort();
  mach_port_name_t intermediate_port = MACH_PORT_NULL;
  if (port_to_insert.get() != MACH_PORT_NULL) {
    intermediate_port = CreateIntermediateMachPort(
        task_port, base::mac::ScopedMachSendRight(port_to_insert.release()));
  }
  return RouteWireFormatToAnother(
      CopyWireFormat(wire_format, intermediate_port));
}

void AttachmentBrokerPrivilegedMac::AddPrecursor(
    base::ProcessId pid,
    base::mac::ScopedMachSendRight port,
    const BrokerableAttachment::AttachmentId& id) {
  base::AutoLock l(precursors_lock_);
  auto it = precursors_.find(pid);
  if (it == precursors_.end())
    precursors_[pid] = new ScopedVector<AttachmentPrecursor>;

  precursors_[pid]->push_back(new AttachmentPrecursor(
      pid, base::mac::ScopedMachSendRight(port.release()), id));
}

void AttachmentBrokerPrivilegedMac::ProcessExtractorsForProcess(
    base::ProcessId pid) {
  base::AutoLock l(extractors_lock_);
  auto it = extractors_.find(pid);
  if (it == extractors_.end())
    return;

  {
    base::AutoLock auto_lock(*get_lock());
    if (!GetSenderWithProcessId(pid)) {
      // If there is no sender, then the source process is no longer running.
      LogError(ERROR_SOURCE_NOT_FOUND);
      delete it->second;
      extractors_.erase(it);
      return;
    }
  }

  mach_port_t task_port = port_provider_->TaskForPid(pid);

  // It's possible that the source process has not yet provided the privileged
  // process with its task port.
  if (task_port == MACH_PORT_NULL)
    return;

  while (!it->second->empty()) {
    auto extractor_it = it->second->begin();
    ProcessExtractor(*extractor_it, task_port);
    it->second->erase(extractor_it);
  }

  delete it->second;
  extractors_.erase(it);
}

void AttachmentBrokerPrivilegedMac::ProcessExtractor(
    AttachmentExtractor* extractor,
    mach_port_t task_port) {
  DCHECK(task_port);
  base::mac::ScopedMachSendRight send_right =
      ExtractNamedRight(task_port, extractor->port());
  AddPrecursor(extractor->dest_pid(),
               base::mac::ScopedMachSendRight(send_right.release()),
               extractor->id());
  SendPrecursorsForProcess(extractor->dest_pid());
}

void AttachmentBrokerPrivilegedMac::AddExtractor(
    base::ProcessId source_pid,
    base::ProcessId dest_pid,
    mach_port_name_t port,
    const BrokerableAttachment::AttachmentId& id) {
  base::AutoLock l(extractors_lock_);
  DCHECK_NE(base::GetCurrentProcId(), source_pid);

  auto it = extractors_.find(source_pid);
  if (it == extractors_.end())
    extractors_[source_pid] = new ScopedVector<AttachmentExtractor>;

  extractors_[source_pid]->push_back(
      new AttachmentExtractor(source_pid, dest_pid, port, id));
}

}  // namespace IPC