path: root/content/browser/mach_broker_mac.mm

// Copyright (c) 2011 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 "content/browser/mach_broker_mac.h"

#include <bsm/libbsm.h>
#include <servers/bootstrap.h>

#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/command_line.h"
#include "base/logging.h"
#include "base/mac/foundation_util.h"
#include "base/mac/scoped_mach_port.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/strings/sys_string_conversions.h"
#include "base/threading/platform_thread.h"
#include "content/browser/renderer_host/render_process_host_impl.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/child_process_data.h"
#include "content/public/browser/notification_service.h"
#include "content/public/browser/notification_types.h"
#include "content/public/common/content_switches.h"

namespace content {

namespace {

// Prints a string representation of a Mach error code.
std::string MachErrorCode(kern_return_t err) {
  return base::StringPrintf("0x%x %s", err, mach_error_string(err));
}

// Mach message structure used in the child as a sending message.
struct MachBroker_ChildSendMsg {
  mach_msg_header_t header;
  mach_msg_body_t body;
  mach_msg_port_descriptor_t child_task_port;
};

// Complement to the ChildSendMsg, this is used in the parent for receiving
// a message. Contains a message trailer with audit information.
struct MachBroker_ParentRecvMsg : public MachBroker_ChildSendMsg {
  mach_msg_audit_trailer_t trailer;
};

}  // namespace

class MachListenerThreadDelegate : public base::PlatformThread::Delegate {
 public:
  explicit MachListenerThreadDelegate(MachBroker* broker)
      : broker_(broker),
        server_port_(MACH_PORT_NULL) {
    DCHECK(broker_);
  }

  bool Init() {
    DCHECK(server_port_ == MACH_PORT_NULL);

    mach_port_t port;
    kern_return_t kr = mach_port_allocate(mach_task_self(),
                                          MACH_PORT_RIGHT_RECEIVE,
                                          &port);
    if (kr != KERN_SUCCESS) {
      LOG(ERROR) << "Failed to allocate MachBroker server port: "
                 << MachErrorCode(kr);
      return false;
    }

    // Allocate a send right for the server port.
    kr = mach_port_insert_right(
        mach_task_self(), port, port, MACH_MSG_TYPE_MAKE_SEND);
    if (kr != KERN_SUCCESS) {
      LOG(ERROR) << "Failed to insert send right for MachBroker server port: "
                 << MachErrorCode(kr);
      return false;
    }

    server_port_.reset(port);

    // Register the port with the bootstrap server. Because bootstrap_register
    // is deprecated, this has to be wraped in an ObjC interface.
    NSPort* ns_port = [NSMachPort portWithMachPort:port
                                           options:NSMachPortDeallocateNone];
    NSString* name = base::SysUTF8ToNSString(broker_->GetMachPortName());
    return [[NSMachBootstrapServer sharedInstance] registerPort:ns_port
                                                           name:name];
  }

  // Implement |PlatformThread::Delegate|.
  virtual void ThreadMain() OVERRIDE {
    MachBroker_ParentRecvMsg msg;
    bzero(&msg, sizeof(msg));
    msg.header.msgh_size = sizeof(msg);
    msg.header.msgh_local_port = server_port_.get();

    kern_return_t kr;
    do {
      // Use the kernel audit information to make sure this message is from
      // a task that this process spawned. The kernel audit token contains the
      // unspoofable pid of the task that sent the message.
      mach_msg_option_t options = MACH_RCV_MSG |
          MACH_RCV_TRAILER_TYPE(MACH_RCV_TRAILER_AUDIT) |
          MACH_RCV_TRAILER_ELEMENTS(MACH_RCV_TRAILER_AUDIT);

      kr = mach_msg(&msg.header, options, 0, sizeof(msg), server_port_,
          MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
      if (kr == KERN_SUCCESS) {
        // TODO(rsesek): In the 10.7 SDK, there's audit_token_to_pid().
        pid_t child_pid;
        audit_token_to_au32(msg.trailer.msgh_audit,
            NULL, NULL, NULL, NULL, NULL, &child_pid, NULL, NULL);

        mach_port_t child_task_port = msg.child_task_port.name;

        // Take the lock and update the broker information.
        base::AutoLock lock(broker_->GetLock());
        broker_->FinalizePid(child_pid, child_task_port);
      }
    } while (kr == KERN_SUCCESS);

    LOG(ERROR) << "MachBroker thread exiting; mach_msg() likely failed: "
               << MachErrorCode(kr);
  }

 private:
  // The MachBroker to use when new child task rights are received.  Can be
  // NULL.
  MachBroker* broker_;  // weak

  base::mac::ScopedMachPort server_port_;

  DISALLOW_COPY_AND_ASSIGN(MachListenerThreadDelegate);
};

bool MachBroker::ChildSendTaskPortToParent() {
  // Look up the named MachBroker port that's been registered with the
  // bootstrap server.
  mach_port_t bootstrap_port;
  kern_return_t kr = task_get_bootstrap_port(mach_task_self(), &bootstrap_port);
  if (kr != KERN_SUCCESS) {
    LOG(ERROR) << "Failed to look up bootstrap port: " << MachErrorCode(kr);
    return false;
  }

  mach_port_t parent_port;
  kr = bootstrap_look_up(bootstrap_port,
      const_cast<char*>(GetMachPortName().c_str()), &parent_port);
  if (kr != KERN_SUCCESS) {
    LOG(ERROR) << "Failed to look up named parent port: " << MachErrorCode(kr);
    return false;
  }

  // Create the check in message. This will copy a send right on this process'
  // (the child's) task port and send it to the parent.
  MachBroker_ChildSendMsg msg;
  bzero(&msg, sizeof(msg));
  msg.header.msgh_bits = MACH_MSGH_BITS_REMOTE(MACH_MSG_TYPE_COPY_SEND) |
                         MACH_MSGH_BITS_COMPLEX;
  msg.header.msgh_remote_port = parent_port;
  msg.header.msgh_size = sizeof(msg);
  msg.body.msgh_descriptor_count = 1;
  msg.child_task_port.name = mach_task_self();
  msg.child_task_port.disposition = MACH_MSG_TYPE_PORT_SEND;
  msg.child_task_port.type = MACH_MSG_PORT_DESCRIPTOR;

  kr = mach_msg(&msg.header, MACH_SEND_MSG | MACH_SEND_TIMEOUT, sizeof(msg),
      0, MACH_PORT_NULL, 100 /*milliseconds*/, MACH_PORT_NULL);
  if (kr != KERN_SUCCESS) {
    LOG(ERROR) << "Failed to send task port to parent: " << MachErrorCode(kr);
    return false;
  }

  return true;
}

MachBroker* MachBroker::GetInstance() {
  return Singleton<MachBroker, LeakySingletonTraits<MachBroker> >::get();
}

base::Lock& MachBroker::GetLock() {
  return lock_;
}

void MachBroker::EnsureRunning() {
  lock_.AssertAcquired();

  if (!listener_thread_started_) {
    listener_thread_started_ = true;

    BrowserThread::PostTask(
        BrowserThread::UI, FROM_HERE,
        base::Bind(&MachBroker::RegisterNotifications, base::Unretained(this)));

    // Intentional leak.  This thread is never joined or reaped.
    MachListenerThreadDelegate* thread = new MachListenerThreadDelegate(this);
    if (thread->Init()) {
      base::PlatformThread::CreateNonJoinable(0, thread);
    } else {
      LOG(ERROR) << "Failed to initialize the MachListenerThreadDelegate";
    }
  }
}

void MachBroker::AddPlaceholderForPid(base::ProcessHandle pid) {
  lock_.AssertAcquired();

  DCHECK_EQ(0u, mach_map_.count(pid));
  mach_map_[pid] = MACH_PORT_NULL;
}

mach_port_t MachBroker::TaskForPid(base::ProcessHandle pid) const {
  base::AutoLock lock(lock_);
  MachBroker::MachMap::const_iterator it = mach_map_.find(pid);
  if (it == mach_map_.end())
    return MACH_PORT_NULL;
  return it->second;
}

void MachBroker::BrowserChildProcessHostDisconnected(
    const ChildProcessData& data) {
  InvalidatePid(data.handle);
}

void MachBroker::BrowserChildProcessCrashed(const ChildProcessData& data) {
  InvalidatePid(data.handle);
}

void MachBroker::Observe(int type,
                         const NotificationSource& source,
                         const NotificationDetails& details) {
  // TODO(rohitrao): These notifications do not always carry the proper PIDs,
  // especially when the renderer is already gone or has crashed.  Find a better
  // way to listen for child process deaths.  http://crbug.com/55734
  base::ProcessHandle handle = 0;
  switch (type) {
    case NOTIFICATION_RENDERER_PROCESS_CLOSED:
      handle = Details<RenderProcessHost::RendererClosedDetails>(
          details)->handle;
      break;
    case NOTIFICATION_RENDERER_PROCESS_TERMINATED:
      handle = Source<RenderProcessHost>(source)->GetHandle();
      break;
    default:
      NOTREACHED() << "Unexpected notification";
      break;
  }
  InvalidatePid(handle);
}

MachBroker::MachBroker() : listener_thread_started_(false) {
}

MachBroker::~MachBroker() {}

void MachBroker::FinalizePid(base::ProcessHandle pid,
                             mach_port_t task_port) {
  lock_.AssertAcquired();

  MachMap::iterator it = mach_map_.find(pid);
  if (it == mach_map_.end()) {
    // Do nothing for unknown pids.
    LOG(ERROR) << "Unknown process " << pid << " is sending Mach IPC messages!";
    return;
  }

  DCHECK(it->second == MACH_PORT_NULL);
  if (it->second == MACH_PORT_NULL)
    it->second = task_port;
}

void MachBroker::InvalidatePid(base::ProcessHandle pid) {
  base::AutoLock lock(lock_);
  MachBroker::MachMap::iterator it = mach_map_.find(pid);
  if (it == mach_map_.end())
    return;

  kern_return_t kr = mach_port_deallocate(mach_task_self(),
                                          it->second);
  LOG_IF(WARNING, kr != KERN_SUCCESS)
     << "Failed to mach_port_deallocate mach task " << it->second
     << ", error " << MachErrorCode(kr);
  mach_map_.erase(it);
}

// static
std::string MachBroker::GetMachPortName() {
  const CommandLine* command_line = CommandLine::ForCurrentProcess();
  const bool is_child = command_line->HasSwitch(switches::kProcessType);

  // In non-browser (child) processes, use the parent's pid.
  const pid_t pid = is_child ? getppid() : getpid();
  return base::StringPrintf("%s.rohitfork.%d", base::mac::BaseBundleID(), pid);
}

void MachBroker::RegisterNotifications() {
  registrar_.Add(this, NOTIFICATION_RENDERER_PROCESS_CLOSED,
                 NotificationService::AllBrowserContextsAndSources());
  registrar_.Add(this, NOTIFICATION_RENDERER_PROCESS_TERMINATED,
                 NotificationService::AllBrowserContextsAndSources());

  // No corresponding StopObservingBrowserChildProcesses,
  // we leak this singleton.
  BrowserChildProcessObserver::Add(this);
}

}  // namespace content