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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2008 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/common/ipc_channel_posix.h"
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include "mozilla/Mutex.h"
#if defined(XP_DARWIN)
# include <mach/message.h>
# include <mach/port.h>
# include "mozilla/UniquePtrExtensions.h"
# include "chrome/common/mach_ipc_mac.h"
#endif
#if defined(XP_DARWIN) || defined(XP_NETBSD)
# include <sched.h>
#endif
#include <stddef.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <sys/uio.h>
#include <string>
#include <map>
#include "base/command_line.h"
#include "base/eintr_wrapper.h"
#include "base/logging.h"
#include "base/process.h"
#include "base/process_util.h"
#include "base/string_util.h"
#include "chrome/common/chrome_switches.h"
#include "chrome/common/ipc_channel_utils.h"
#include "chrome/common/ipc_message_utils.h"
#include "mozilla/ipc/Endpoint.h"
#include "mozilla/ipc/ProtocolUtils.h"
#include "mozilla/Atomics.h"
#include "mozilla/StaticMutex.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"
// Use OS specific iovec array limit where it's possible.
#if defined(IOV_MAX)
static const size_t kMaxIOVecSize = IOV_MAX;
#elif defined(ANDROID)
static const size_t kMaxIOVecSize = 256;
#else
static const size_t kMaxIOVecSize = 16;
#endif
using namespace mozilla::ipc;
namespace IPC {
// IPC channels on Windows use named pipes (CreateNamedPipe()) with
// channel ids as the pipe names. Channels on POSIX use anonymous
// Unix domain sockets created via socketpair() as pipes. These don't
// quite line up.
//
// When creating a child subprocess, the parent side of the fork
// arranges it such that the initial control channel ends up on the
// magic file descriptor gClientChannelFd in the child. Future
// connections (file descriptors) can then be passed via that
// connection via sendmsg().
//
// On Android, child processes are created as a service instead of
// forking the parent process. The Android Binder service is used to
// transport the IPC channel file descriptor to the child process.
// So rather than re-mapping the file descriptor to a known value,
// the received channel file descriptor is set by calling
// SetClientChannelFd before gecko has been initialized and started
// in the child process.
//------------------------------------------------------------------------------
namespace {
// This is the file descriptor number that a client process expects to find its
// IPC socket.
static int gClientChannelFd =
#if defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
// On android/ios the fd is set at the time of child creation.
-1
#else
3
#endif // defined(MOZ_WIDGET_ANDROID)
;
//------------------------------------------------------------------------------
bool ErrorIsBrokenPipe(int err) { return err == EPIPE || err == ECONNRESET; }
// Some Android ARM64 devices appear to have a bug where sendmsg
// sometimes returns 0xFFFFFFFF, which we're assuming is a -1 that was
// incorrectly truncated to 32-bit and then zero-extended.
//
// This is a workaround to detect that value and replace it with -1
// (and check that there really was an error), because the largest
// amount we'll ever write is Channel::kMaximumMessageSize (256MiB).
//
// The workaround is also enabled on x86_64 Android on debug builds,
// although the bug isn't known to manifest there, so that there will
// be some CI coverage of this code.
static inline ssize_t corrected_sendmsg(int socket,
const struct msghdr* message,
int flags) {
#if defined(ANDROID) && \
(defined(__aarch64__) || (defined(DEBUG) && defined(__x86_64__)))
static constexpr auto kBadValue = static_cast<ssize_t>(0xFFFFFFFF);
static_assert(kBadValue > 0);
# ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
errno = 0;
# endif
ssize_t bytes_written = sendmsg(socket, message, flags);
if (bytes_written == kBadValue) {
MOZ_DIAGNOSTIC_ASSERT(errno != 0);
bytes_written = -1;
}
MOZ_DIAGNOSTIC_ASSERT(bytes_written < kBadValue);
return bytes_written;
#else
return sendmsg(socket, message, flags);
#endif
}
} // namespace
//------------------------------------------------------------------------------
#if defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
void Channel::SetClientChannelFd(int fd) { gClientChannelFd = fd; }
#endif // defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
int Channel::GetClientChannelHandle() { return gClientChannelFd; }
Channel::ChannelImpl::ChannelImpl(ChannelHandle pipe, Mode mode,
base::ProcessId other_pid)
: chan_cap_("ChannelImpl::SendMutex",
MessageLoopForIO::current()->SerialEventTarget()),
other_pid_(other_pid) {
Init(mode);
SetPipe(pipe.release());
EnqueueHelloMessage();
}
void Channel::ChannelImpl::SetPipe(int fd) {
chan_cap_.NoteExclusiveAccess();
pipe_ = fd;
pipe_buf_len_ = 0;
if (fd >= 0) {
int buf_len;
socklen_t optlen = sizeof(buf_len);
if (getsockopt(fd, SOL_SOCKET, SO_SNDBUF, &buf_len, &optlen) != 0) {
CHROMIUM_LOG(WARNING)
<< "Unable to determine pipe buffer size: " << strerror(errno);
return;
}
CHECK(optlen == sizeof(buf_len));
CHECK(buf_len > 0);
pipe_buf_len_ = static_cast<unsigned>(buf_len);
}
}
bool Channel::ChannelImpl::PipeBufHasSpaceAfter(size_t already_written) {
// If the OS didn't tell us the buffer size for some reason, then
// don't apply this limitation on the amount we try to write.
return pipe_buf_len_ == 0 ||
static_cast<size_t>(pipe_buf_len_) > already_written;
}
void Channel::ChannelImpl::Init(Mode mode) {
// Verify that we fit in a "quantum-spaced" jemalloc bucket.
static_assert(sizeof(*this) <= 512, "Exceeded expected size class");
MOZ_RELEASE_ASSERT(kControlBufferHeaderSize >= CMSG_SPACE(0));
MOZ_RELEASE_ASSERT(kControlBufferSize >=
CMSG_SPACE(sizeof(int) * kControlBufferMaxFds));
chan_cap_.NoteExclusiveAccess();
mode_ = mode;
is_blocked_on_write_ = false;
partial_write_.reset();
input_buf_offset_ = 0;
input_buf_ = mozilla::MakeUnique<char[]>(Channel::kReadBufferSize);
input_cmsg_buf_ = mozilla::MakeUnique<char[]>(kControlBufferSize);
SetPipe(-1);
waiting_connect_ = true;
#if defined(XP_DARWIN)
last_pending_fd_id_ = 0;
other_task_ = nullptr;
#endif
}
bool Channel::ChannelImpl::EnqueueHelloMessage() {
mozilla::UniquePtr<Message> msg(
new Message(MSG_ROUTING_NONE, HELLO_MESSAGE_TYPE));
if (!msg->WriteInt(base::GetCurrentProcId())) {
CloseLocked();
return false;
}
OutputQueuePush(std::move(msg));
return true;
}
bool Channel::ChannelImpl::Connect(Listener* listener) {
IOThread().AssertOnCurrentThread();
mozilla::MutexAutoLock lock(SendMutex());
chan_cap_.NoteExclusiveAccess();
if (pipe_ == -1) {
return false;
}
listener_ = listener;
return ContinueConnect();
}
bool Channel::ChannelImpl::ContinueConnect() {
chan_cap_.NoteExclusiveAccess();
MOZ_ASSERT(pipe_ != -1);
#if defined(XP_DARWIN)
// If we're still waiting for our peer task to be provided, don't start
// listening yet. We'll start receiving messages once the task_t is set.
if (accept_mach_ports_ && privileged_ && !other_task_) {
MOZ_ASSERT(waiting_connect_);
return true;
}
#endif
MessageLoopForIO::current()->WatchFileDescriptor(
pipe_, true, MessageLoopForIO::WATCH_READ, &read_watcher_, this);
waiting_connect_ = false;
return ProcessOutgoingMessages();
}
void Channel::ChannelImpl::SetOtherPid(base::ProcessId other_pid) {
IOThread().AssertOnCurrentThread();
mozilla::MutexAutoLock lock(SendMutex());
chan_cap_.NoteExclusiveAccess();
MOZ_RELEASE_ASSERT(
other_pid_ == base::kInvalidProcessId || other_pid_ == other_pid,
"Multiple sources of SetOtherPid disagree!");
other_pid_ = other_pid;
}
bool Channel::ChannelImpl::ProcessIncomingMessages() {
chan_cap_.NoteOnIOThread();
struct msghdr msg = {0};
struct iovec iov;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = input_cmsg_buf_.get();
for (;;) {
msg.msg_controllen = kControlBufferSize;
if (pipe_ == -1) return false;
// In some cases the beginning of a message will be stored in input_buf_. We
// don't want to overwrite that, so we store the new data after it.
iov.iov_base = input_buf_.get() + input_buf_offset_;
iov.iov_len = Channel::kReadBufferSize - input_buf_offset_;
// Read from pipe.
// recvmsg() returns 0 if the connection has closed or EAGAIN if no data
// is waiting on the pipe.
ssize_t bytes_read = HANDLE_EINTR(recvmsg(pipe_, &msg, MSG_DONTWAIT));
if (bytes_read < 0) {
if (errno == EAGAIN) {
return true;
} else {
if (!ErrorIsBrokenPipe(errno)) {
CHROMIUM_LOG(ERROR)
<< "pipe error (fd " << pipe_ << "): " << strerror(errno);
}
return false;
}
} else if (bytes_read == 0) {
// The pipe has closed...
Close();
return false;
}
DCHECK(bytes_read);
// a pointer to an array of |num_wire_fds| file descriptors from the read
const int* wire_fds = NULL;
unsigned num_wire_fds = 0;
// walk the list of control messages and, if we find an array of file
// descriptors, save a pointer to the array
// This next if statement is to work around an OSX issue where
// CMSG_FIRSTHDR will return non-NULL in the case that controllen == 0.
// Here's a test case:
//
// int main() {
// struct msghdr msg;
// msg.msg_control = &msg;
// msg.msg_controllen = 0;
// if (CMSG_FIRSTHDR(&msg))
// printf("Bug found!\n");
// }
if (msg.msg_controllen > 0) {
// On OSX, CMSG_FIRSTHDR doesn't handle the case where controllen is 0
// and will return a pointer into nowhere.
for (struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg); cmsg;
cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
const unsigned payload_len = cmsg->cmsg_len - CMSG_LEN(0);
DCHECK(payload_len % sizeof(int) == 0);
wire_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
num_wire_fds = payload_len / 4;
if (msg.msg_flags & MSG_CTRUNC) {
CHROMIUM_LOG(ERROR)
<< "SCM_RIGHTS message was truncated"
<< " cmsg_len:" << cmsg->cmsg_len << " fd:" << pipe_;
for (unsigned i = 0; i < num_wire_fds; ++i)
IGNORE_EINTR(close(wire_fds[i]));
return false;
}
break;
}
}
}
// Process messages from input buffer.
const char* p = input_buf_.get();
const char* end = input_buf_.get() + input_buf_offset_ + bytes_read;
// A pointer to an array of |num_fds| file descriptors which includes any
// fds that have spilled over from a previous read.
const int* fds;
unsigned num_fds;
unsigned fds_i = 0; // the index of the first unused descriptor
if (input_overflow_fds_.empty()) {
fds = wire_fds;
num_fds = num_wire_fds;
} else {
// This code may look like a no-op in the case where
// num_wire_fds == 0, but in fact:
//
// 1. wire_fds will be nullptr, so passing it to memcpy is
// undefined behavior according to the C standard, even though
// the memcpy length is 0.
//
// 2. prev_size will be an out-of-bounds index for
// input_overflow_fds_; this is undefined behavior according to
// the C++ standard, even though the element only has its
// pointer taken and isn't accessed (and the corresponding
// operation on a C array would be defined).
//
// UBSan makes #1 a fatal error, and assertions in libstdc++ do
// the same for #2 if enabled.
if (num_wire_fds > 0) {
const size_t prev_size = input_overflow_fds_.size();
input_overflow_fds_.resize(prev_size + num_wire_fds);
memcpy(&input_overflow_fds_[prev_size], wire_fds,
num_wire_fds * sizeof(int));
}
fds = &input_overflow_fds_[0];
num_fds = input_overflow_fds_.size();
}
// The data for the message we're currently reading consists of any data
// stored in incoming_message_ followed by data in input_buf_ (followed by
// other messages).
// NOTE: We re-check `pipe_` after each message to make sure we weren't
// closed while calling `OnMessageReceived` or `OnChannelConnected`.
while (p < end && pipe_ != -1) {
// Try to figure out how big the message is. Size is 0 if we haven't read
// enough of the header to know the size.
uint32_t message_length = 0;
if (incoming_message_) {
message_length = incoming_message_->size();
} else {
message_length = Message::MessageSize(p, end);
}
if (!message_length) {
// We haven't seen the full message header.
MOZ_ASSERT(!incoming_message_);
// Move everything we have to the start of the buffer. We'll finish
// reading this message when we get more data. For now we leave it in
// input_buf_.
memmove(input_buf_.get(), p, end - p);
input_buf_offset_ = end - p;
break;
}
input_buf_offset_ = 0;
bool partial;
if (incoming_message_) {
// We already have some data for this message stored in
// incoming_message_. We want to append the new data there.
Message& m = *incoming_message_;
// How much data from this message remains to be added to
// incoming_message_?
MOZ_DIAGNOSTIC_ASSERT(message_length > m.CurrentSize());
uint32_t remaining = message_length - m.CurrentSize();
// How much data from this message is stored in input_buf_?
uint32_t in_buf = std::min(remaining, uint32_t(end - p));
m.InputBytes(p, in_buf);
p += in_buf;
// Are we done reading this message?
partial = in_buf != remaining;
} else {
// How much data from this message is stored in input_buf_?
uint32_t in_buf = std::min(message_length, uint32_t(end - p));
incoming_message_ = mozilla::MakeUnique<Message>(p, in_buf);
p += in_buf;
// Are we done reading this message?
partial = in_buf != message_length;
}
if (partial) {
break;
}
Message& m = *incoming_message_;
if (m.header()->num_handles) {
// the message has file descriptors
const char* error = NULL;
if (m.header()->num_handles > num_fds - fds_i) {
// the message has been completely received, but we didn't get
// enough file descriptors.
error = "Message needs unreceived descriptors";
}
if (m.header()->num_handles >
IPC::Message::MAX_DESCRIPTORS_PER_MESSAGE) {
// There are too many descriptors in this message
error = "Message requires an excessive number of descriptors";
}
if (error) {
CHROMIUM_LOG(WARNING)
<< error << " channel:" << this << " message-type:" << m.type()
<< " header()->num_handles:" << m.header()->num_handles
<< " num_fds:" << num_fds << " fds_i:" << fds_i;
// close the existing file descriptors so that we don't leak them
for (unsigned i = fds_i; i < num_fds; ++i)
IGNORE_EINTR(close(fds[i]));
input_overflow_fds_.clear();
// abort the connection
return false;
}
#if defined(XP_DARWIN)
// Send a message to the other side, indicating that we are now
// responsible for closing the descriptor.
auto fdAck = mozilla::MakeUnique<Message>(MSG_ROUTING_NONE,
RECEIVED_FDS_MESSAGE_TYPE);
DCHECK(m.fd_cookie() != 0);
fdAck->set_fd_cookie(m.fd_cookie());
{
mozilla::MutexAutoLock lock(SendMutex());
OutputQueuePush(std::move(fdAck));
}
#endif
nsTArray<mozilla::UniqueFileHandle> handles(m.header()->num_handles);
for (unsigned end_i = fds_i + m.header()->num_handles; fds_i < end_i;
++fds_i) {
handles.AppendElement(mozilla::UniqueFileHandle(fds[fds_i]));
}
m.SetAttachedFileHandles(std::move(handles));
}
// Note: We set other_pid_ below when we receive a Hello message (which
// has no routing ID), but we only emit a profiler marker for messages
// with a routing ID, so there's no conflict here.
AddIPCProfilerMarker(m, other_pid_, MessageDirection::eReceiving,
MessagePhase::TransferEnd);
#ifdef IPC_MESSAGE_DEBUG_EXTRA
DLOG(INFO) << "received message on channel @" << this << " with type "
<< m.type();
#endif
if (m.routing_id() == MSG_ROUTING_NONE &&
m.type() == HELLO_MESSAGE_TYPE) {
// The Hello message contains only the process id.
int32_t other_pid = MessageIterator(m).NextInt();
SetOtherPid(other_pid);
listener_->OnChannelConnected(other_pid);
#if defined(XP_DARWIN)
} else if (m.routing_id() == MSG_ROUTING_NONE &&
m.type() == RECEIVED_FDS_MESSAGE_TYPE) {
DCHECK(m.fd_cookie() != 0);
CloseDescriptors(m.fd_cookie());
#endif
} else {
mozilla::LogIPCMessage::Run run(&m);
#if defined(XP_DARWIN)
if (!AcceptMachPorts(m)) {
return false;
}
#endif
listener_->OnMessageReceived(std::move(incoming_message_));
}
incoming_message_ = nullptr;
}
input_overflow_fds_ = std::vector<int>(&fds[fds_i], &fds[num_fds]);
// When the input data buffer is empty, the overflow fds should be too. If
// this is not the case, we probably have a rogue renderer which is trying
// to fill our descriptor table.
if (!incoming_message_ && input_buf_offset_ == 0 &&
!input_overflow_fds_.empty()) {
// We close these descriptors in Close()
return false;
}
}
}
bool Channel::ChannelImpl::ProcessOutgoingMessages() {
// NOTE: This method may be called on threads other than `IOThread()`.
chan_cap_.NoteSendMutex();
DCHECK(!waiting_connect_); // Why are we trying to send messages if there's
// no connection?
is_blocked_on_write_ = false;
if (output_queue_.IsEmpty()) return true;
if (pipe_ == -1) return false;
// Write out all the messages we can till the write blocks or there are no
// more outgoing messages.
while (!output_queue_.IsEmpty()) {
Message* msg = output_queue_.FirstElement().get();
struct msghdr msgh = {0};
char cmsgBuf[kControlBufferSize];
if (partial_write_.isNothing()) {
#if defined(XP_DARWIN)
if (!TransferMachPorts(*msg)) {
return false;
}
#endif
if (msg->attached_handles_.Length() >
IPC::Message::MAX_DESCRIPTORS_PER_MESSAGE) {
MOZ_DIAGNOSTIC_ASSERT(false, "Too many file descriptors!");
CHROMIUM_LOG(FATAL) << "Too many file descriptors!";
// This should not be reached.
return false;
}
msg->header()->num_handles = msg->attached_handles_.Length();
#if defined(XP_DARWIN)
if (!msg->attached_handles_.IsEmpty()) {
msg->set_fd_cookie(++last_pending_fd_id_);
}
#endif
Pickle::BufferList::IterImpl iter(msg->Buffers());
MOZ_DIAGNOSTIC_ASSERT(!iter.Done(), "empty message");
partial_write_.emplace(PartialWrite{iter, msg->attached_handles_});
AddIPCProfilerMarker(*msg, other_pid_, MessageDirection::eSending,
MessagePhase::TransferStart);
}
if (partial_write_->iter_.Done()) {
MOZ_DIAGNOSTIC_ASSERT(false, "partial_write_->iter_ should not be done");
// report a send error to our caller, which will close the channel.
return false;
}
// How much of this message have we written so far?
Pickle::BufferList::IterImpl iter = partial_write_->iter_;
auto handles = partial_write_->handles_;
// Serialize attached file descriptors into the cmsg header. Only up to
// kControlBufferMaxFds can be serialized at once, so messages with more
// attachments must be sent over multiple `sendmsg` calls.
const size_t num_fds = std::min(handles.Length(), kControlBufferMaxFds);
size_t max_amt_to_write = iter.TotalBytesAvailable(msg->Buffers());
if (num_fds > 0) {
msgh.msg_control = cmsgBuf;
msgh.msg_controllen = CMSG_LEN(sizeof(int) * num_fds);
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msgh);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = msgh.msg_controllen;
for (size_t i = 0; i < num_fds; ++i) {
reinterpret_cast<int*>(CMSG_DATA(cmsg))[i] = handles[i].get();
}
// Avoid writing one byte per remaining handle in excess of
// kControlBufferMaxFds. Each handle written will consume a minimum of 4
// bytes in the message (to store it's index), so we can depend on there
// being enough data to send every handle.
size_t remaining = handles.Length() - num_fds;
MOZ_ASSERT(max_amt_to_write > remaining,
"must be at least one byte in the message for each handle");
max_amt_to_write -= remaining;
}
// Store remaining segments to write into iovec.
//
// Don't add more than kMaxIOVecSize iovecs so that we avoid
// OS-dependent limits. Also, stop adding iovecs if we've already
// prepared to write at least the full buffer size.
struct iovec iov[kMaxIOVecSize];
size_t iov_count = 0;
size_t amt_to_write = 0;
while (!iter.Done() && iov_count < kMaxIOVecSize &&
PipeBufHasSpaceAfter(amt_to_write) &&
amt_to_write < max_amt_to_write) {
char* data = iter.Data();
size_t size =
std::min(iter.RemainingInSegment(), max_amt_to_write - amt_to_write);
iov[iov_count].iov_base = data;
iov[iov_count].iov_len = size;
iov_count++;
amt_to_write += size;
iter.Advance(msg->Buffers(), size);
}
MOZ_ASSERT(amt_to_write <= max_amt_to_write);
MOZ_ASSERT(amt_to_write > 0);
const bool intentional_short_write = !iter.Done();
msgh.msg_iov = iov;
msgh.msg_iovlen = iov_count;
ssize_t bytes_written =
HANDLE_EINTR(corrected_sendmsg(pipe_, &msgh, MSG_DONTWAIT));
if (bytes_written < 0) {
switch (errno) {
case EAGAIN:
// Not an error; the sendmsg would have blocked, so return to the
// event loop and try again later.
break;
#if defined(XP_DARWIN) || defined(XP_NETBSD)
//
// On OS X if sendmsg() is trying to send fds between processes and
// there isn't enough room in the output buffer to send the fd
// structure over atomically then EMSGSIZE is returned. The same
// applies to NetBSD as well.
//
// EMSGSIZE presents a problem since the system APIs can only call us
// when there's room in the socket buffer and not when there is
// "enough" room.
//
// The current behavior is to return to the event loop when EMSGSIZE
// is received and hopefull service another FD. This is however still
// technically a busy wait since the event loop will call us right
// back until the receiver has read enough data to allow passing the
// FD over atomically.
case EMSGSIZE:
// Because this is likely to result in a busy-wait, we'll try to make
// it easier for the receiver to make progress, but only if we're on
// the I/O thread already.
if (IOThread().IsOnCurrentThread()) {
sched_yield();
}
break;
#endif
default:
if (!ErrorIsBrokenPipe(errno)) {
CHROMIUM_LOG(ERROR) << "pipe error: " << strerror(errno);
}
return false;
}
}
if (intentional_short_write ||
static_cast<size_t>(bytes_written) != amt_to_write) {
// If write() fails with EAGAIN or EMSGSIZE then bytes_written will be -1.
if (bytes_written > 0) {
MOZ_DIAGNOSTIC_ASSERT(intentional_short_write ||
static_cast<size_t>(bytes_written) <
amt_to_write);
partial_write_->iter_.AdvanceAcrossSegments(msg->Buffers(),
bytes_written);
partial_write_->handles_ = handles.From(num_fds);
// We should not hit the end of the buffer.
MOZ_DIAGNOSTIC_ASSERT(!partial_write_->iter_.Done());
}
is_blocked_on_write_ = true;
if (IOThread().IsOnCurrentThread()) {
// If we're on the I/O thread already, tell libevent to call us back
// when things are unblocked.
MessageLoopForIO::current()->WatchFileDescriptor(
pipe_,
false, // One shot
MessageLoopForIO::WATCH_WRITE, &write_watcher_, this);
} else {
// Otherwise, emulate being called back from libevent on the I/O thread,
// which will re-try the write, and then potentially start watching if
// still necessary.
IOThread().Dispatch(mozilla::NewRunnableMethod<int>(
"ChannelImpl::ContinueProcessOutgoing", this,
&ChannelImpl::OnFileCanWriteWithoutBlocking, -1));
}
return true;
} else {
MOZ_ASSERT(partial_write_->handles_.Length() == num_fds,
"not all handles were sent");
partial_write_.reset();
#if defined(XP_DARWIN)
if (!msg->attached_handles_.IsEmpty()) {
pending_fds_.push_back(PendingDescriptors{
msg->fd_cookie(), std::move(msg->attached_handles_)});
}
#else
if (bytes_written > 0) {
msg->attached_handles_.Clear();
}
#endif
// Message sent OK!
AddIPCProfilerMarker(*msg, other_pid_, MessageDirection::eSending,
MessagePhase::TransferEnd);
#ifdef IPC_MESSAGE_DEBUG_EXTRA
DLOG(INFO) << "sent message @" << msg << " on channel @" << this
<< " with type " << msg->type();
#endif
OutputQueuePop();
// msg has been destroyed, so clear the dangling reference.
msg = nullptr;
}
}
return true;
}
bool Channel::ChannelImpl::Send(mozilla::UniquePtr<Message> message) {
// NOTE: This method may be called on threads other than `IOThread()`.
mozilla::MutexAutoLock lock(SendMutex());
chan_cap_.NoteSendMutex();
#ifdef IPC_MESSAGE_DEBUG_EXTRA
DLOG(INFO) << "sending message @" << message.get() << " on channel @" << this
<< " with type " << message->type() << " ("
<< output_queue_.Count() << " in queue)";
#endif
// If the channel has been closed, ProcessOutgoingMessages() is never going
// to pop anything off output_queue; output_queue will only get emptied when
// the channel is destructed. We might as well delete message now, instead
// of waiting for the channel to be destructed.
if (pipe_ == -1) {
if (mozilla::ipc::LoggingEnabled()) {
fprintf(stderr,
"Can't send message %s, because this channel is closed.\n",
message->name());
}
return false;
}
OutputQueuePush(std::move(message));
if (!waiting_connect_) {
if (!is_blocked_on_write_) {
if (!ProcessOutgoingMessages()) return false;
}
}
return true;
}
// Called by libevent when we can read from th pipe without blocking.
void Channel::ChannelImpl::OnFileCanReadWithoutBlocking(int fd) {
IOThread().AssertOnCurrentThread();
chan_cap_.NoteOnIOThread();
if (!waiting_connect_ && fd == pipe_ && pipe_ != -1) {
if (!ProcessIncomingMessages()) {
Close();
listener_->OnChannelError();
// The OnChannelError() call may delete this, so we need to exit now.
return;
}
}
}
#if defined(XP_DARWIN)
void Channel::ChannelImpl::CloseDescriptors(uint32_t pending_fd_id) {
mozilla::MutexAutoLock lock(SendMutex());
chan_cap_.NoteExclusiveAccess();
DCHECK(pending_fd_id != 0);
for (std::list<PendingDescriptors>::iterator i = pending_fds_.begin();
i != pending_fds_.end(); i++) {
if ((*i).id == pending_fd_id) {
pending_fds_.erase(i);
return;
}
}
DCHECK(false) << "pending_fd_id not in our list!";
}
#endif
void Channel::ChannelImpl::OutputQueuePush(mozilla::UniquePtr<Message> msg) {
chan_cap_.NoteSendMutex();
mozilla::LogIPCMessage::LogDispatchWithPid(msg.get(), other_pid_);
MOZ_DIAGNOSTIC_ASSERT(pipe_ != -1);
msg->AssertAsLargeAsHeader();
output_queue_.Push(std::move(msg));
}
void Channel::ChannelImpl::OutputQueuePop() {
// Clear any reference to the front of output_queue_ before we destroy it.
partial_write_.reset();
mozilla::UniquePtr<Message> message = output_queue_.Pop();
}
// Called by libevent when we can write to the pipe without blocking.
void Channel::ChannelImpl::OnFileCanWriteWithoutBlocking(int fd) {
RefPtr<ChannelImpl> grip(this);
IOThread().AssertOnCurrentThread();
mozilla::ReleasableMutexAutoLock lock(SendMutex());
chan_cap_.NoteExclusiveAccess();
if (pipe_ != -1 && !ProcessOutgoingMessages()) {
CloseLocked();
lock.Unlock();
listener_->OnChannelError();
}
}
void Channel::ChannelImpl::Close() {
IOThread().AssertOnCurrentThread();
mozilla::MutexAutoLock lock(SendMutex());
CloseLocked();
}
void Channel::ChannelImpl::CloseLocked() {
chan_cap_.NoteExclusiveAccess();
// Close can be called multiple times, so we need to make sure we're
// idempotent.
// Unregister libevent for the FIFO and close it.
read_watcher_.StopWatchingFileDescriptor();
write_watcher_.StopWatchingFileDescriptor();
if (pipe_ != -1) {
IGNORE_EINTR(close(pipe_));
SetPipe(-1);
}
while (!output_queue_.IsEmpty()) {
OutputQueuePop();
}
// Close any outstanding, received file descriptors
for (std::vector<int>::iterator i = input_overflow_fds_.begin();
i != input_overflow_fds_.end(); ++i) {
IGNORE_EINTR(close(*i));
}
input_overflow_fds_.clear();
#if defined(XP_DARWIN)
pending_fds_.clear();
other_task_ = nullptr;
#endif
}
#if defined(XP_DARWIN)
void Channel::ChannelImpl::SetOtherMachTask(task_t task) {
IOThread().AssertOnCurrentThread();
mozilla::MutexAutoLock lock(SendMutex());
chan_cap_.NoteExclusiveAccess();
if (NS_WARN_IF(pipe_ == -1)) {
return;
}
MOZ_ASSERT(accept_mach_ports_ && privileged_ && waiting_connect_);
other_task_ = mozilla::RetainMachSendRight(task);
// Now that `other_task_` is provided, we can continue connecting.
ContinueConnect();
}
void Channel::ChannelImpl::StartAcceptingMachPorts(Mode mode) {
IOThread().AssertOnCurrentThread();
mozilla::MutexAutoLock lock(SendMutex());
chan_cap_.NoteExclusiveAccess();
if (accept_mach_ports_) {
MOZ_ASSERT(privileged_ == (MODE_SERVER == mode));
return;
}
accept_mach_ports_ = true;
privileged_ = MODE_SERVER == mode;
}
//------------------------------------------------------------------------------
// Mach port transferring logic
//
// It is currently not possible to directly transfer a mach send right between
// two content processes using SCM_RIGHTS, unlike how we can handle file
// descriptors. This means that mach ports need to be transferred through a
// separate mechanism. This file only implements support for transferring mach
// ports between a (potentially sandboxed) child process and the parent process.
// Support for transferring mach ports between other process pairs is handled by
// `NodeController`, which is responsible for relaying messages which carry
// handles via the parent process.
//
// The logic which we use for doing this is based on the following from
// Chromium, which pioneered this technique. As of this writing, chromium no
// longer uses this strategy, as all IPC messages are sent using mach ports on
// macOS.
//
// As we only need to consider messages between the privileged (parent) and
// unprivileged (child) processes in this code, there are 2 relevant cases which
// we need to handle:
//
// # Unprivileged (child) to Privileged (parent)
//
// As the privileged process has access to the unprivileged process' `task_t`,
// it is possible to directly extract the mach port from the target process'
// address space, given its name, using `mach_port_extract_right`.
//
// To transfer the port, the unprivileged process will leak a reference to the
// send right, and include the port's name in the message footer. The privileged
// process will extract that port right (and drop the reference in the old
// process) using `mach_port_extract_right` with `MACH_MSG_TYPE_MOVE_SEND`. The
// call to `mach_port_extract_right` is handled by `BrokerExtractSendRight`
//
// # Privileged (parent) to Unprivileged (child)
//
// Unfortunately, the process of transferring a right into a target process is
// more complex. The only well-supported way to transfer a right into a process
// is by sending it with `mach_msg`, and receiving it on the other side [1].
//
// To work around this, the privileged process uses `mach_port_allocate` to
// create a new receive right in the target process using its `task_t`, and
// `mach_port_extract_right` to extract a send-once right to that port. It then
// sends a message to the port with port we're intending to send as an
// attachment. This is handled by `BrokerTransferSendRight`, which returns the
// name of the newly created receive right in the target process to be sent in
// the message footer.
//
// In the unprivileged process, `mach_msg` is used to receive a single message
// from the receive right, which will have the actual port we were trying to
// transfer as an attachment. This is handled by the `MachReceivePortSendRight`
// function.
//
// [1] We cannot use `mach_port_insert_right` to transfer the right into the
// target process, as that method requires explicitly specifying the remote
// port's name, and we do not control the port name allocator.
// Extract a send right from the given peer task. A reference to the remote
// right will be dropped. See comment above for details.
static mozilla::UniqueMachSendRight BrokerExtractSendRight(
task_t task, mach_port_name_t name) {
mach_port_t extractedRight = MACH_PORT_NULL;
mach_msg_type_name_t extractedRightType;
kern_return_t kr =
mach_port_extract_right(task, name, MACH_MSG_TYPE_MOVE_SEND,
&extractedRight, &extractedRightType);
if (kr != KERN_SUCCESS) {
CHROMIUM_LOG(ERROR) << "failed to extract port right from other process. "
<< mach_error_string(kr);
return nullptr;
}
MOZ_ASSERT(extractedRightType == MACH_MSG_TYPE_PORT_SEND,
"We asked the OS for a send port");
return mozilla::UniqueMachSendRight(extractedRight);
}
// Transfer a send right to the given peer task. The name of a receive right in
// the remote process will be returned if successful. The sent port can be
// obtained from that port in the peer task using `MachReceivePortSendRight`.
// See comment above for details.
static mozilla::Maybe<mach_port_name_t> BrokerTransferSendRight(
task_t task, mozilla::UniqueMachSendRight port_to_send) {
mach_port_name_t endpoint;
kern_return_t kr =
mach_port_allocate(task, MACH_PORT_RIGHT_RECEIVE, &endpoint);
if (kr != KERN_SUCCESS) {
CHROMIUM_LOG(ERROR)
<< "Unable to create receive right in TransferMachPorts. "
<< mach_error_string(kr);
return mozilla::Nothing();
}
// Clean up the endpoint on error.
auto destroyEndpoint =
mozilla::MakeScopeExit([&] { mach_port_deallocate(task, endpoint); });
// 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, endpoint, MACH_PORT_LIMITS_INFO,
reinterpret_cast<mach_port_info_t>(&limits),
MACH_PORT_LIMITS_INFO_COUNT);
if (kr != KERN_SUCCESS) {
CHROMIUM_LOG(ERROR)
<< "Unable configure receive right in TransferMachPorts. "
<< mach_error_string(kr);
return mozilla::Nothing();
}
// Get a send right.
mach_port_t send_once_right;
mach_msg_type_name_t send_right_type;
kr = mach_port_extract_right(task, endpoint, MACH_MSG_TYPE_MAKE_SEND_ONCE,
&send_once_right, &send_right_type);
if (kr != KERN_SUCCESS) {
CHROMIUM_LOG(ERROR) << "Unable extract send right in TransferMachPorts. "
<< mach_error_string(kr);
return mozilla::Nothing();
}
MOZ_ASSERT(MACH_MSG_TYPE_PORT_SEND_ONCE == send_right_type);
kr = MachSendPortSendRight(send_once_right, port_to_send.get(),
mozilla::Some(0), MACH_MSG_TYPE_MOVE_SEND_ONCE);
if (kr != KERN_SUCCESS) {
// This right will be destroyed due to being a SEND_ONCE right if we
// succeed.
mach_port_deallocate(mach_task_self(), send_once_right);
CHROMIUM_LOG(ERROR) << "Unable to transfer right in TransferMachPorts. "
<< mach_error_string(kr);
return mozilla::Nothing();
}
destroyEndpoint.release();
return mozilla::Some(endpoint);
}
// Process footer information attached to the message, and acquire owning
// references to any transferred mach ports. See comment above for details.
bool Channel::ChannelImpl::AcceptMachPorts(Message& msg) {
chan_cap_.NoteOnIOThread();
uint32_t num_send_rights = msg.header()->num_send_rights;
if (num_send_rights == 0) {
return true;
}
if (!accept_mach_ports_) {
CHROMIUM_LOG(ERROR) << "invalid message: " << msg.name()
<< ". channel is not configured to accept mach ports";
return false;
}
// Read in the payload from the footer, truncating the message.
nsTArray<uint32_t> payload;
payload.AppendElements(num_send_rights);
if (!msg.ReadFooter(payload.Elements(), num_send_rights * sizeof(uint32_t),
/* truncate */ true)) {
CHROMIUM_LOG(ERROR) << "failed to read mach port payload from message";
return false;
}
msg.header()->num_send_rights = 0;
// Read in the handles themselves, transferring ownership as required.
nsTArray<mozilla::UniqueMachSendRight> rights(num_send_rights);
for (uint32_t name : payload) {
mozilla::UniqueMachSendRight right;
if (privileged_) {
if (!other_task_) {
CHROMIUM_LOG(ERROR) << "other_task_ is invalid in AcceptMachPorts";
return false;
}
right = BrokerExtractSendRight(other_task_.get(), name);
} else {
kern_return_t kr = MachReceivePortSendRight(
mozilla::UniqueMachReceiveRight(name), mozilla::Some(0), &right);
if (kr != KERN_SUCCESS) {
CHROMIUM_LOG(ERROR)
<< "failed to receive mach send right. " << mach_error_string(kr);
return false;
}
}
if (!right) {
return false;
}
rights.AppendElement(std::move(right));
}
// We're done with the handle footer, truncate the message at that point.
msg.attached_send_rights_ = std::move(rights);
MOZ_ASSERT(msg.num_send_rights() == num_send_rights);
return true;
}
// Transfer ownership of any attached mach ports to the peer task, and add the
// required information for AcceptMachPorts to the message footer. See comment
// above for details.
bool Channel::ChannelImpl::TransferMachPorts(Message& msg) {
uint32_t num_send_rights = msg.num_send_rights();
if (num_send_rights == 0) {
return true;
}
if (!accept_mach_ports_) {
CHROMIUM_LOG(ERROR) << "cannot send message: " << msg.name()
<< ". channel is not configured to accept mach ports";
return false;
}
# ifdef DEBUG
uint32_t rights_offset = msg.header()->payload_size;
# endif
nsTArray<uint32_t> payload(num_send_rights);
for (auto& port_to_send : msg.attached_send_rights_) {
if (privileged_) {
if (!other_task_) {
CHROMIUM_LOG(ERROR) << "other_task_ is invalid in TransferMachPorts";
return false;
}
mozilla::Maybe<mach_port_name_t> endpoint =
BrokerTransferSendRight(other_task_.get(), std::move(port_to_send));
if (!endpoint) {
return false;
}
payload.AppendElement(*endpoint);
} else {
payload.AppendElement(port_to_send.release());
}
}
msg.attached_send_rights_.Clear();
msg.WriteFooter(payload.Elements(), payload.Length() * sizeof(uint32_t));
msg.header()->num_send_rights = num_send_rights;
MOZ_ASSERT(msg.header()->payload_size ==
rights_offset + (sizeof(uint32_t) * num_send_rights),
"Unexpected number of bytes written for send rights footer?");
return true;
}
#endif
//------------------------------------------------------------------------------
// Channel's methods simply call through to ChannelImpl.
Channel::Channel(ChannelHandle pipe, Mode mode, base::ProcessId other_pid)
: channel_impl_(new ChannelImpl(std::move(pipe), mode, other_pid)) {
MOZ_COUNT_CTOR(IPC::Channel);
}
Channel::~Channel() { MOZ_COUNT_DTOR(IPC::Channel); }
bool Channel::Connect(Listener* listener) {
return channel_impl_->Connect(listener);
}
void Channel::Close() { channel_impl_->Close(); }
bool Channel::Send(mozilla::UniquePtr<Message> message) {
return channel_impl_->Send(std::move(message));
}
void Channel::SetOtherPid(base::ProcessId other_pid) {
channel_impl_->SetOtherPid(other_pid);
}
bool Channel::IsClosed() const { return channel_impl_->IsClosed(); }
#if defined(XP_DARWIN)
void Channel::SetOtherMachTask(task_t task) {
channel_impl_->SetOtherMachTask(task);
}
void Channel::StartAcceptingMachPorts(Mode mode) {
channel_impl_->StartAcceptingMachPorts(mode);
}
#endif
// static
bool Channel::CreateRawPipe(ChannelHandle* server, ChannelHandle* client) {
int fds[2];
if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) < 0) {
mozilla::ipc::AnnotateCrashReportWithErrno(
CrashReporter::Annotation::IpcCreatePipeSocketPairErrno, errno);
return false;
}
auto configureFd = [](int fd) -> bool {
// Mark the endpoints as non-blocking
if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1) {
mozilla::ipc::AnnotateCrashReportWithErrno(
CrashReporter::Annotation::IpcCreatePipeFcntlErrno, errno);
return false;
}
// Mark the pipes as FD_CLOEXEC
int flags = fcntl(fd, F_GETFD);
if (flags == -1) {
mozilla::ipc::AnnotateCrashReportWithErrno(
CrashReporter::Annotation::IpcCreatePipeCloExecErrno, errno);
return false;
}
flags |= FD_CLOEXEC;
if (fcntl(fd, F_SETFD, flags) == -1) {
mozilla::ipc::AnnotateCrashReportWithErrno(
CrashReporter::Annotation::IpcCreatePipeCloExecErrno, errno);
return false;
}
return true;
};
if (!configureFd(fds[0]) || !configureFd(fds[1])) {
IGNORE_EINTR(close(fds[0]));
IGNORE_EINTR(close(fds[1]));
return false;
}
server->reset(fds[0]);
client->reset(fds[1]);
return true;
}
} // namespace IPC