mojo/public/cpp/platform/platform_channel.cc

// Copyright 2018 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 "mojo/public/cpp/platform/platform_channel.h"

#include <cstddef>
#include <cstdint>
#include <string>
#include <utility>

#include "base/logging.h"
#include "base/rand_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_piece.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "build/build_config.h"
#include "mojo/public/cpp/platform/features.h"

#if defined(OS_WIN)
#include <windows.h>

#include "base/win/scoped_handle.h"
#elif defined(OS_FUCHSIA)
#include <lib/zx/channel.h>
#include <zircon/process.h>
#include <zircon/processargs.h>

#include "base/fuchsia/fuchsia_logging.h"
#elif defined(OS_POSIX)
#include <fcntl.h>
#include <sys/types.h>
#include <unistd.h>

#include "base/files/scoped_file.h"
#include "base/posix/global_descriptors.h"
#endif

#if defined(OS_MACOSX) && !defined(OS_IOS)
#include <mach/port.h>

#include "base/mac/mach_logging.h"
#include "base/mac/scoped_mach_port.h"
#endif

#if defined(OS_POSIX) && !defined(OS_NACL_SFI)
#include <sys/socket.h>
#elif defined(OS_NACL_SFI)
#include "native_client/src/public/imc_syscalls.h"
#endif

namespace mojo {

namespace {

#if defined(OS_WIN)
void CreateChannel(PlatformHandle* local_endpoint,
                   PlatformHandle* remote_endpoint) {
  base::string16 pipe_name = base::UTF8ToUTF16(base::StringPrintf(
      "\\\\.\\pipe\\mojo.%lu.%lu.%I64u", ::GetCurrentProcessId(),
      ::GetCurrentThreadId(), base::RandUint64()));
  DWORD kOpenMode =
      PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED | FILE_FLAG_FIRST_PIPE_INSTANCE;
  const DWORD kPipeMode = PIPE_TYPE_BYTE | PIPE_READMODE_BYTE;
  *local_endpoint = PlatformHandle(base::win::ScopedHandle(
      ::CreateNamedPipeW(pipe_name.c_str(), kOpenMode, kPipeMode,
                         1,           // Max instances.
                         4096,        // Output buffer size.
                         4096,        // Input buffer size.
                         5000,        // Timeout in ms.
                         nullptr)));  // Default security descriptor.
  PCHECK(local_endpoint->is_valid());

  const DWORD kDesiredAccess = GENERIC_READ | GENERIC_WRITE;
  // The SECURITY_ANONYMOUS flag means that the server side cannot impersonate
  // the client.
  DWORD kFlags =
      SECURITY_SQOS_PRESENT | SECURITY_ANONYMOUS | FILE_FLAG_OVERLAPPED;
  // Allow the handle to be inherited by child processes.
  SECURITY_ATTRIBUTES security_attributes = {sizeof(SECURITY_ATTRIBUTES),
                                             nullptr, TRUE};
  *remote_endpoint = PlatformHandle(base::win::ScopedHandle(
      ::CreateFileW(pipe_name.c_str(), kDesiredAccess, 0, &security_attributes,
                    OPEN_EXISTING, kFlags, nullptr)));
  PCHECK(remote_endpoint->is_valid());

  // Since a client has connected, ConnectNamedPipe() should return zero and
  // GetLastError() should return ERROR_PIPE_CONNECTED.
  CHECK(!::ConnectNamedPipe(local_endpoint->GetHandle().Get(), nullptr));
  PCHECK(::GetLastError() == ERROR_PIPE_CONNECTED);
}
#elif defined(OS_FUCHSIA)
void CreateChannel(PlatformHandle* local_endpoint,
                   PlatformHandle* remote_endpoint) {
  zx::channel handles[2];
  zx_status_t result = zx::channel::create(0, &handles[0], &handles[1]);
  ZX_CHECK(result == ZX_OK, result);

  *local_endpoint = PlatformHandle(std::move(handles[0]));
  *remote_endpoint = PlatformHandle(std::move(handles[1]));
  DCHECK(local_endpoint->is_valid());
  DCHECK(remote_endpoint->is_valid());
}
#elif defined(OS_POSIX)

#if defined(OS_MACOSX) && !defined(OS_IOS)
// TODO(crbug.com/932175): This will be renamed CreateChannel().
void CreateMachChannel(PlatformHandle* local_endpoint,
                       PlatformHandle* remote_endpoint) {
  // Mach messaging is simplex; and in order to enable full-duplex
  // communication, the Mojo channel implementation performs an internal
  // handshake with its peer to establish two sets of Mach receive and send
  // rights. The handshake process starts with the creation of one
  // PlatformChannel endpoint.
  base::mac::ScopedMachReceiveRight receive;
  base::mac::ScopedMachSendRight send;
  // The mpl_qlimit specified here should stay in sync with
  // NamedPlatformChannel.
  CHECK(base::mac::CreateMachPort(&receive, &send, MACH_PORT_QLIMIT_LARGE));

  // In a reverse of Mach messaging semantics, in Mojo the "local" endpoint is
  // the send right, while the "remote" end is the receive right.
  *local_endpoint = PlatformHandle(std::move(send));
  *remote_endpoint = PlatformHandle(std::move(receive));
}
#endif  // defined(OS_MACOSX) && !defined(OS_IOS)

#if defined(OS_ANDROID)
// Leave room for any other descriptors defined in content for example.
// TODO(https://crbug.com/676442): Consider changing base::GlobalDescriptors to
// generate a key when setting the file descriptor.
constexpr int kAndroidClientHandleDescriptor =
    base::GlobalDescriptors::kBaseDescriptor + 10000;
#else
bool IsTargetDescriptorUsed(const base::FileHandleMappingVector& mapping,
                            int target_fd) {
  for (size_t i = 0; i < mapping.size(); ++i) {
    if (mapping[i].second == target_fd)
      return true;
  }
  return false;
}
#endif

void CreateChannel(PlatformHandle* local_endpoint,
                   PlatformHandle* remote_endpoint) {
#if defined(OS_MACOSX) && !defined(OS_IOS)
  if (base::FeatureList::IsEnabled(features::kMojoChannelMac)) {
    return CreateMachChannel(local_endpoint, remote_endpoint);
  }
#endif
  int fds[2];
#if defined(OS_NACL_SFI)
  PCHECK(imc_socketpair(fds) == 0);
#else
  PCHECK(socketpair(AF_UNIX, SOCK_STREAM, 0, fds) == 0);

  // Set non-blocking on both ends.
  PCHECK(fcntl(fds[0], F_SETFL, O_NONBLOCK) == 0);
  PCHECK(fcntl(fds[1], F_SETFL, O_NONBLOCK) == 0);

#if defined(OS_MACOSX)
  // This turns off |SIGPIPE| when writing to a closed socket, causing the call
  // to fail with |EPIPE| instead. On Linux we have to use |send...()| with
  // |MSG_NOSIGNAL| instead, which is not supported on Mac.
  int no_sigpipe = 1;
  PCHECK(setsockopt(fds[0], SOL_SOCKET, SO_NOSIGPIPE, &no_sigpipe,
                    sizeof(no_sigpipe)) == 0);
  PCHECK(setsockopt(fds[1], SOL_SOCKET, SO_NOSIGPIPE, &no_sigpipe,
                    sizeof(no_sigpipe)) == 0);
#endif  // defined(OS_MACOSX)
#endif  // defined(OS_NACL_SFI)

  *local_endpoint = PlatformHandle(base::ScopedFD(fds[0]));
  *remote_endpoint = PlatformHandle(base::ScopedFD(fds[1]));
  DCHECK(local_endpoint->is_valid());
  DCHECK(remote_endpoint->is_valid());
}
#else
#error "Unsupported platform."
#endif

}  // namespace

const char PlatformChannel::kHandleSwitch[] = "mojo-platform-channel-handle";

PlatformChannel::PlatformChannel() {
  PlatformHandle local_handle;
  PlatformHandle remote_handle;
  CreateChannel(&local_handle, &remote_handle);
  local_endpoint_ = PlatformChannelEndpoint(std::move(local_handle));
  remote_endpoint_ = PlatformChannelEndpoint(std::move(remote_handle));
}

PlatformChannel::PlatformChannel(PlatformChannel&& other) = default;

PlatformChannel::~PlatformChannel() = default;

PlatformChannel& PlatformChannel::operator=(PlatformChannel&& other) = default;

void PlatformChannel::PrepareToPassRemoteEndpoint(HandlePassingInfo* info_input,
                                                  std::string* value) {
#if !defined(OS_MACOSX) || defined(OS_IOS)
  auto* info = info_input;
  DCHECK(info);
#endif
  DCHECK(value);
  DCHECK(remote_endpoint_.is_valid());

#if defined(OS_WIN)
  info->push_back(remote_endpoint_.platform_handle().GetHandle().Get());
  *value = base::NumberToString(
      HandleToLong(remote_endpoint_.platform_handle().GetHandle().Get()));
#elif defined(OS_FUCHSIA)
  const uint32_t id = base::LaunchOptions::AddHandleToTransfer(
      info, remote_endpoint_.platform_handle().GetHandle().get());
  *value = base::NumberToString(id);
#elif defined(OS_ANDROID)
  int fd = remote_endpoint_.platform_handle().GetFD().get();
  int mapped_fd = kAndroidClientHandleDescriptor + info->size();
  info->emplace_back(fd, mapped_fd);
  *value = base::NumberToString(mapped_fd);
#elif defined(OS_POSIX)
#if defined(OS_MACOSX) && !defined(OS_IOS)
  if (base::FeatureList::IsEnabled(features::kMojoChannelMac)) {
    auto* info = static_cast<base::MachPortsForRendezvous*>(info_input);
    DCHECK(remote_endpoint_.platform_handle().is_mach_receive());
    base::mac::ScopedMachReceiveRight receive_right =
        remote_endpoint_.TakePlatformHandle().TakeMachReceiveRight();
    base::MachPortsForRendezvous::key_type rendezvous_key = 0;
    do {
      rendezvous_key =
          static_cast<decltype(rendezvous_key)>(base::RandUint64());
    } while (info->find(rendezvous_key) != info->end());
    auto it = info->insert(std::make_pair(
        rendezvous_key, base::MachRendezvousPort(std::move(receive_right))));
    DCHECK(it.second) << "Failed to insert port for rendezvous.";
    *value = base::NumberToString(rendezvous_key);
    return;
  }

  auto* info = static_cast<base::FileHandleMappingVector*>(info_input);
#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
  // Arbitrary sanity check to ensure the loop below terminates reasonably
  // quickly.
  CHECK_LT(info->size(), 1000u);

  // Find a suitable FD to map the remote endpoint handle to in the child
  // process. This has quadratic time complexity in the size of |*info|, but
  // |*info| should be very small and is usually empty.
  int target_fd = base::GlobalDescriptors::kBaseDescriptor;
  while (IsTargetDescriptorUsed(*info, target_fd))
    ++target_fd;
  info->emplace_back(remote_endpoint_.platform_handle().GetFD().get(),
                     target_fd);
  *value = base::NumberToString(target_fd);
#endif
}

void PlatformChannel::PrepareToPassRemoteEndpoint(
    HandlePassingInfo* info,
    base::CommandLine* command_line) {
  std::string value;
  PrepareToPassRemoteEndpoint(info, &value);
  if (!value.empty())
    command_line->AppendSwitchASCII(kHandleSwitch, value);
}

void PlatformChannel::PrepareToPassRemoteEndpoint(
    base::LaunchOptions* options,
    base::CommandLine* command_line) {
#if defined(OS_WIN)
  PrepareToPassRemoteEndpoint(&options->handles_to_inherit, command_line);
#elif defined(OS_FUCHSIA)
  PrepareToPassRemoteEndpoint(&options->handles_to_transfer, command_line);
#elif defined(OS_MACOSX) && !defined(OS_IOS)
  HandlePassingInfo info;
  if (base::FeatureList::IsEnabled(features::kMojoChannelMac))
    info = options->mach_ports_for_rendezvous;
  else
    info = options->fds_to_remap;

  PrepareToPassRemoteEndpoint(&info, command_line);

  if (base::FeatureList::IsEnabled(features::kMojoChannelMac))
    options->mach_ports_for_rendezvous = info;
  else
    options->fds_to_remap = info;
#elif defined(OS_POSIX)
  PrepareToPassRemoteEndpoint(&options->fds_to_remap, command_line);
#else
#error "Platform not supported."
#endif
}

void PlatformChannel::RemoteProcessLaunchAttempted() {
#if defined(OS_FUCHSIA)
  // Unlike other platforms, Fuchsia transfers handle ownership to the new
  // process, rather than duplicating it. For consistency the process-launch
  // call will have consumed the handle regardless of whether launch succeeded.
  DCHECK(remote_endpoint_.platform_handle().is_valid_handle());
  ignore_result(remote_endpoint_.TakePlatformHandle().ReleaseHandle());
#else
  remote_endpoint_.reset();
#endif
}

// static
PlatformChannelEndpoint PlatformChannel::RecoverPassedEndpointFromString(
    base::StringPiece value) {
#if defined(OS_WIN)
  int handle_value = 0;
  if (value.empty() || !base::StringToInt(value, &handle_value)) {
    DLOG(ERROR) << "Invalid PlatformChannel endpoint string.";
    return PlatformChannelEndpoint();
  }
  return PlatformChannelEndpoint(
      PlatformHandle(base::win::ScopedHandle(LongToHandle(handle_value))));
#elif defined(OS_FUCHSIA)
  unsigned int handle_value = 0;
  if (value.empty() || !base::StringToUint(value, &handle_value)) {
    DLOG(ERROR) << "Invalid PlatformChannel endpoint string.";
    return PlatformChannelEndpoint();
  }
  return PlatformChannelEndpoint(PlatformHandle(zx::handle(
      zx_take_startup_handle(base::checked_cast<uint32_t>(handle_value)))));
#elif defined(OS_ANDROID)
  base::GlobalDescriptors::Key key = -1;
  if (value.empty() || !base::StringToUint(value, &key)) {
    DLOG(ERROR) << "Invalid PlatformChannel endpoint string.";
    return PlatformChannelEndpoint();
  }
  return PlatformChannelEndpoint(PlatformHandle(
      base::ScopedFD(base::GlobalDescriptors::GetInstance()->Get(key))));
#elif defined(OS_POSIX)
#if defined(OS_MACOSX) && !defined(OS_IOS)
  if (base::FeatureList::IsEnabled(features::kMojoChannelMac)) {
    auto* client = base::MachPortRendezvousClient::GetInstance();
    if (!client) {
      DLOG(ERROR) << "Mach rendezvous failed.";
      return PlatformChannelEndpoint();
    }
    uint32_t rendezvous_key = 0;
    if (value.empty() || !base::StringToUint(value, &rendezvous_key)) {
      DLOG(ERROR) << "Invalid PlatformChannel rendezvous key.";
      return PlatformChannelEndpoint();
    }
    auto receive = client->TakeReceiveRight(rendezvous_key);
    if (!receive.is_valid()) {
      DLOG(ERROR) << "Invalid PlatformChannel receive right.";
      return PlatformChannelEndpoint();
    }
    return PlatformChannelEndpoint(PlatformHandle(std::move(receive)));
  }
#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
  int fd = -1;
  if (value.empty() || !base::StringToInt(value, &fd) ||
      fd < base::GlobalDescriptors::kBaseDescriptor) {
    DLOG(ERROR) << "Invalid PlatformChannel endpoint string.";
    return PlatformChannelEndpoint();
  }
  return PlatformChannelEndpoint(PlatformHandle(base::ScopedFD(fd)));
#endif
}

// static
PlatformChannelEndpoint PlatformChannel::RecoverPassedEndpointFromCommandLine(
    const base::CommandLine& command_line) {
  return RecoverPassedEndpointFromString(
      command_line.GetSwitchValueASCII(kHandleSwitch));
}

}  // namespace mojo