Have each SandboxedProcessLauncherDelegate maintain a zygote.

content/browser/zygote_host/zygote_communication_linux.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 "content/browser/zygote_host/zygote_communication_linux.h"
+
+#include <sys/socket.h>
+
+#include "base/base_switches.h"
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
+#include "base/path_service.h"
+#include "base/pickle.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/posix/unix_domain_socket_linux.h"
+#include "content/browser/renderer_host/render_sandbox_host_linux.h"
+#include "content/browser/zygote_host/zygote_host_impl_linux.h"
+#include "content/common/child_process_sandbox_support_impl_linux.h"
+#include "content/common/zygote_commands_linux.h"
+#include "content/public/browser/content_browser_client.h"
+#include "content/public/common/content_switches.h"
+#include "content/public/common/result_codes.h"
+#include "sandbox/linux/services/credentials.h"
+#include "sandbox/linux/services/namespace_sandbox.h"
+#include "sandbox/linux/suid/client/setuid_sandbox_host.h"
+#include "ui/gfx/switches.h"
+
+namespace content {
+
+namespace {
+
+// Receive a fixed message on fd and return the sender's PID.
+// Returns true if the message received matches the expected message.
+bool ReceiveFixedMessage(int fd,
+                         const char* expect_msg,
+                         size_t expect_len,
+                         base::ProcessId* sender_pid) {
+  char buf[expect_len + 1];
+  std::vector<base::ScopedFD> fds_vec;
+
+  const ssize_t len = base::UnixDomainSocket::RecvMsgWithPid(
+      fd, buf, sizeof(buf), &fds_vec, sender_pid);
+  if (static_cast<size_t>(len) != expect_len)
+    return false;
+  if (memcmp(buf, expect_msg, expect_len) != 0)
+    return false;
+  if (!fds_vec.empty())
+    return false;
+  return true;
+}
+
+}  // namespace
+
+#if defined(OS_POSIX)

[mdempsky, 2016/01/05 22:41:57]

This shouldn't be necessary since Linux is always OS_POSIX?

[Greg K, 2016/01/06 18:20:41]

Done.

+ZygoteCommunication::ZygoteCommunication()
+    : init_(false),
+      control_fd_(-1),
+      control_lock_(),
+      pid_(),
+      list_of_running_zygote_children_(),
+      child_tracking_lock_(),
+      have_read_sandbox_status_word_(false),
+      use_suid_sandbox_for_adj_oom_score_(false),
+      sandbox_status_(0) {}
+
+ZygoteCommunication::~ZygoteCommunication() {}
+
+bool ZygoteCommunication::SendMessage(const base::Pickle& data,
+                                      const std::vector<int>* fds) {
+  DCHECK_NE(-1, control_fd_);
+  CHECK(data.size() <= kZygoteMaxMessageLength)
+      << "Trying to send too-large message to zygote (sending " << data.size()
+      << " bytes, max is " << kZygoteMaxMessageLength << ")";
+  CHECK(!fds || fds->size() <= base::UnixDomainSocket::kMaxFileDescriptors)
+      << "Trying to send message with too many file descriptors to zygote "
+      << "(sending " << fds->size() << ", max is "
+      << base::UnixDomainSocket::kMaxFileDescriptors << ")";
+
+  return base::UnixDomainSocket::SendMsg(control_fd_, data.data(), data.size(),
+                                         fds ? *fds : std::vector<int>());
+}
+
+ssize_t ZygoteCommunication::ReadSandboxStatus() {
+  DCHECK_NE(-1, control_fd_);
+  // At startup we send a kZygoteCommandGetSandboxStatus request to the zygote,
+  // but don't wait for the reply. Thus, the first time that we read from the
+  // zygote, we get the reply to that request.
+  ssize_t bytes_read = HANDLE_EINTR(
+      read(control_fd_, &sandbox_status_, sizeof(sandbox_status_)));
+  if (bytes_read != sizeof(sandbox_status_)) {
+    return -1;
+  }
+  return bytes_read;
+}
+
+ssize_t ZygoteCommunication::ReadReply(void* buf, size_t buf_len) {
+  DCHECK_NE(-1, control_fd_);
+  if (!have_read_sandbox_status_word_) {
+    if (ReadSandboxStatus() == -1) {
+      return -1;
+    }
+    have_read_sandbox_status_word_ = true;
+    UMA_HISTOGRAM_SPARSE_SLOWLY("Linux.SandboxStatus", sandbox_status_);
+  }
+
+  return HANDLE_EINTR(read(control_fd_, buf, buf_len));
+}
+
+pid_t ZygoteCommunication::ForkRequest(const std::vector<std::string>& argv,
+                                       scoped_ptr<FileDescriptorInfo> mapping,
+                                       const std::string& process_type) {
+  DCHECK(init_);
+
+  base::Pickle pickle;
+  int raw_socks[2];
+  PCHECK(0 == socketpair(AF_UNIX, SOCK_SEQPACKET, 0, raw_socks));
+  base::ScopedFD my_sock(raw_socks[0]);
+  base::ScopedFD peer_sock(raw_socks[1]);
+  CHECK(base::UnixDomainSocket::EnableReceiveProcessId(my_sock.get()));
+
+  pickle.WriteInt(kZygoteCommandFork);
+  pickle.WriteString(process_type);
+  pickle.WriteInt(argv.size());
+  for (std::vector<std::string>::const_iterator i = argv.begin();
+       i != argv.end(); ++i)
+    pickle.WriteString(*i);
+
+  // Fork requests contain one file descriptor for the PID oracle, and one
+  // more for each file descriptor mapping for the child process.
+  const size_t num_fds_to_send = 1 + mapping->GetMappingSize();
+  pickle.WriteInt(num_fds_to_send);
+
+  std::vector<int> fds;
+
+  // First FD to send is peer_sock.
+  // TODO(morrita): Ideally, this should be part of the mapping so that
+  // FileDescriptorInfo can manages its lifetime.
+  fds.push_back(peer_sock.get());
+
+  // The rest come from mapping.
+  for (size_t i = 0; i < mapping->GetMappingSize(); ++i) {
+    pickle.WriteUInt32(mapping->GetIDAt(i));
+    fds.push_back(mapping->GetFDAt(i));
+  }
+
+  // Sanity check that we've populated |fds| correctly.
+  DCHECK_EQ(num_fds_to_send, fds.size());
+
+  pid_t pid;
+  {
+    base::AutoLock lock(control_lock_);
+    if (!SendMessage(pickle, &fds))
+      return base::kNullProcessHandle;
+    mapping.reset();
+    peer_sock.reset();
+
+    {
+      char buf[sizeof(kZygoteChildPingMessage) + 1];
+      std::vector<base::ScopedFD> recv_fds;
+      base::ProcessId real_pid;
+
+      ssize_t n = base::UnixDomainSocket::RecvMsgWithPid(
+          my_sock.get(), buf, sizeof(buf), &recv_fds, &real_pid);
+      if (n != sizeof(kZygoteChildPingMessage) ||
+          0 != memcmp(buf, kZygoteChildPingMessage,
+                      sizeof(kZygoteChildPingMessage))) {
+        // Zygote children should still be trustworthy when they're supposed to
+        // ping us, so something's broken if we don't receive a valid ping.
+        LOG(ERROR) << "Did not receive ping from zygote child";
+        NOTREACHED();
+        real_pid = -1;
+      }
+      my_sock.reset();
+
+      // Always send PID back to zygote.
+      base::Pickle pid_pickle;
+      pid_pickle.WriteInt(kZygoteCommandForkRealPID);
+      pid_pickle.WriteInt(real_pid);
+      if (!SendMessage(pid_pickle, NULL))
+        return base::kNullProcessHandle;
+    }
+
+    // Read the reply, which pickles the PID and an optional UMA enumeration.
+    static const unsigned kMaxReplyLength = 2048;
+    char buf[kMaxReplyLength];
+    const ssize_t len = ReadReply(buf, sizeof(buf));
+
+    base::Pickle reply_pickle(buf, len);
+    base::PickleIterator iter(reply_pickle);
+    if (len <= 0 || !iter.ReadInt(&pid))
+      return base::kNullProcessHandle;
+
+    // If there is a nonempty UMA name string, then there is a UMA
+    // enumeration to record.
+    std::string uma_name;
+    int uma_sample;
+    int uma_boundary_value;
+    if (iter.ReadString(&uma_name) && !uma_name.empty() &&
+        iter.ReadInt(&uma_sample) && iter.ReadInt(&uma_boundary_value)) {
+      // We cannot use the UMA_HISTOGRAM_ENUMERATION macro here,
+      // because that's only for when the name is the same every time.
+      // Here we're using whatever name we got from the other side.
+      // But since it's likely that the same one will be used repeatedly
+      // (even though it's not guaranteed), we cache it here.
+      static base::HistogramBase* uma_histogram;
+      if (!uma_histogram || uma_histogram->histogram_name() != uma_name) {
+        uma_histogram = base::LinearHistogram::FactoryGet(
+            uma_name, 1, uma_boundary_value, uma_boundary_value + 1,
+            base::HistogramBase::kUmaTargetedHistogramFlag);
+      }
+      uma_histogram->Add(uma_sample);
+    }
+
+    if (pid <= 0)
+      return base::kNullProcessHandle;
+  }
+
+#if !defined(OS_OPENBSD)
+  // This is just a starting score for a renderer or extension (the
+  // only types of processes that will be started this way).  It will
+  // get adjusted as time goes on.  (This is the same value as
+  // chrome::kLowestRendererOomScore in chrome/chrome_constants.h, but
+  // that's not something we can include here.)
+  const int kLowestRendererOomScore = 300;
+  ZygoteHostImpl::GetInstance()->AdjustRendererOOMScore(
+      pid, kLowestRendererOomScore);
+#endif
+
+  ZygoteChildBorn(pid);
+  return pid;
+}
+
+void ZygoteCommunication::EnsureProcessTerminated(pid_t process) {
+  DCHECK(init_);
+  base::Pickle pickle;
+
+  pickle.WriteInt(kZygoteCommandReap);
+  pickle.WriteInt(process);
+  if (!SendMessage(pickle, NULL))
+    LOG(ERROR) << "Failed to send Reap message to zygote";
+  ZygoteChildDied(process);
+}
+
+void ZygoteCommunication::ZygoteChildBorn(pid_t process) {
+  base::AutoLock lock(child_tracking_lock_);
+  bool new_element_inserted =
+      list_of_running_zygote_children_.insert(process).second;
+  DCHECK(new_element_inserted);
+}
+
+void ZygoteCommunication::ZygoteChildDied(pid_t process) {
+  base::AutoLock lock(child_tracking_lock_);
+  size_t num_erased = list_of_running_zygote_children_.erase(process);
+  DCHECK_EQ(1U, num_erased);
+}
+
+void ZygoteCommunication::Init() {
+  CHECK(!init_);
+
+  base::FilePath chrome_path;
+  CHECK(PathService::Get(base::FILE_EXE, &chrome_path));
+  base::CommandLine cmd_line(chrome_path);
+
+  cmd_line.AppendSwitchASCII(switches::kProcessType, switches::kZygoteProcess);
+
+  int fds[2];
+  CHECK(socketpair(AF_UNIX, SOCK_SEQPACKET, 0, fds) == 0);
+  CHECK(base::UnixDomainSocket::EnableReceiveProcessId(fds[0]));
+  base::FileHandleMappingVector fds_to_map;
+  fds_to_map.push_back(std::make_pair(fds[1], kZygoteSocketPairFd));
+
+  base::LaunchOptions options;
+  const base::CommandLine& browser_command_line =
+      *base::CommandLine::ForCurrentProcess();
+  if (browser_command_line.HasSwitch(switches::kZygoteCmdPrefix)) {
+    cmd_line.PrependWrapper(
+        browser_command_line.GetSwitchValueNative(switches::kZygoteCmdPrefix));
+  }
+  // Append any switches from the browser process that need to be forwarded on
+  // to the zygote/renderers.
+  // Should this list be obtained from browser_render_process_host.cc?
+  static const char* kForwardSwitches[] = {
+      switches::kAllowSandboxDebugging, switches::kDisableSeccompFilterSandbox,
+      switches::kEnableHeapProfiling,
+      switches::kEnableLogging,  // Support, e.g., --enable-logging=stderr.
+      // Zygote process needs to know what resources to have loaded when it
+      // becomes a renderer process.
+      switches::kForceDeviceScaleFactor, switches::kLoggingLevel,
+      switches::kNoSandbox, switches::kPpapiInProcess,
+      switches::kRegisterPepperPlugins, switches::kV, switches::kVModule,
+  };
+  cmd_line.CopySwitchesFrom(browser_command_line, kForwardSwitches,
+                            arraysize(kForwardSwitches));
+
+  GetContentClient()->browser()->AppendExtraCommandLineSwitches(&cmd_line, -1);
+
+  const bool using_namespace_sandbox = ShouldUseNamespaceSandbox();
+  // A non empty sandbox_cmd means we want a SUID sandbox.
+  const bool using_suid_sandbox =
+      !ZygoteHostImpl::GetInstance()->SandboxCommand().empty() &&
+      !using_namespace_sandbox;
+  // Use the SUID sandbox for adjusting OOM scores when we are using the setuid
+  // or namespace sandbox. This is needed beacuse the processes are
+  // non-dumpable, so /proc/pid/oom_score_adj can only be written by root.
+  use_suid_sandbox_for_adj_oom_score_ =
+      !ZygoteHostImpl::GetInstance()->SandboxCommand().empty() &&
+      (using_namespace_sandbox || using_suid_sandbox);
+
+  // Start up the sandbox host process and get the file descriptor for the
+  // renderers to talk to it.
+  const int sfd = RenderSandboxHostLinux::GetInstance()->GetRendererSocket();
+  fds_to_map.push_back(std::make_pair(sfd, GetSandboxFD()));
+
+  base::ScopedFD dummy_fd;
+  if (using_suid_sandbox) {
+    scoped_ptr<sandbox::SetuidSandboxHost> sandbox_host(
+        sandbox::SetuidSandboxHost::Create());
+    sandbox_host->PrependWrapper(&cmd_line);
+    sandbox_host->SetupLaunchOptions(&options, &fds_to_map, &dummy_fd);
+    sandbox_host->SetupLaunchEnvironment();
+  }
+
+  options.fds_to_remap = &fds_to_map;
+  base::Process process =
+      using_namespace_sandbox
+          ? sandbox::NamespaceSandbox::LaunchProcess(cmd_line, options)
+          : base::LaunchProcess(cmd_line, options);
+  CHECK(process.IsValid()) << "Failed to launch zygote process";
+
+  dummy_fd.reset();
+
+  if (using_suid_sandbox || using_namespace_sandbox) {
+    // The SUID sandbox will execute the zygote in a new PID namespace, and
+    // the main zygote process will then fork from there.  Watch now our
+    // elaborate dance to find and validate the zygote's PID.
+
+    // First we receive a message from the zygote boot process.
+    base::ProcessId boot_pid;
+    CHECK(ReceiveFixedMessage(fds[0], kZygoteBootMessage,
+                              sizeof(kZygoteBootMessage), &boot_pid));
+
+    // Within the PID namespace, the zygote boot process thinks it's PID 1,
+    // but its real PID can never be 1. This gives us a reliable test that
+    // the kernel is translating the sender's PID to our namespace.
+    CHECK_GT(boot_pid, 1)
+        << "Received invalid process ID for zygote; kernel might be too old? "
+           "See crbug.com/357670 or try using --"
+        << switches::kDisableSetuidSandbox << " to workaround.";
+
+    // Now receive the message that the zygote's ready to go, along with the
+    // main zygote process's ID.
+    CHECK(ReceiveFixedMessage(fds[0], kZygoteHelloMessage,
+                              sizeof(kZygoteHelloMessage), &pid_));
+    CHECK_GT(pid_, 1);
+
+    if (process.Pid() != pid_) {
+      // Reap the sandbox.
+      base::EnsureProcessGetsReaped(process.Pid());
+    }
+  } else {
+    // Not using the SUID sandbox.
+    // Note that ~base::Process() will reset the internal value, but there's no
+    // real "handle" on POSIX so that is safe.
+    pid_ = process.Pid();
+  }
+
+  close(fds[1]);
+  control_fd_ = fds[0];
+
+  ZygoteHostImpl::GetInstance()->AddZygotePid(pid_);
+
+  base::Pickle pickle;
+  pickle.WriteInt(kZygoteCommandGetSandboxStatus);
+  if (!SendMessage(pickle, NULL))
+    LOG(FATAL) << "Cannot communicate with zygote";
+
+  init_ = true;
+}
+
+base::TerminationStatus ZygoteCommunication::GetTerminationStatus(
+    base::ProcessHandle handle,
+    bool known_dead,
+    int* exit_code) {
+  DCHECK(init_);
+  base::Pickle pickle;
+  pickle.WriteInt(kZygoteCommandGetTerminationStatus);
+  pickle.WriteBool(known_dead);
+  pickle.WriteInt(handle);
+
+  static const unsigned kMaxMessageLength = 128;
+  char buf[kMaxMessageLength];
+  ssize_t len;
+  {
+    base::AutoLock lock(control_lock_);
+    if (!SendMessage(pickle, NULL))
+      LOG(ERROR) << "Failed to send GetTerminationStatus message to zygote";
+    len = ReadReply(buf, sizeof(buf));
+  }
+
+  // Set this now to handle the error cases.
+  if (exit_code)
+    *exit_code = RESULT_CODE_NORMAL_EXIT;
+  int status = base::TERMINATION_STATUS_NORMAL_TERMINATION;
+
+  if (len == -1) {
+    LOG(WARNING) << "Error reading message from zygote: " << errno;
+  } else if (len == 0) {
+    LOG(WARNING) << "Socket closed prematurely.";
+  } else {
+    base::Pickle read_pickle(buf, len);
+    int tmp_status, tmp_exit_code;
+    base::PickleIterator iter(read_pickle);
+    if (!iter.ReadInt(&tmp_status) || !iter.ReadInt(&tmp_exit_code)) {
+      LOG(WARNING)
+          << "Error parsing GetTerminationStatus response from zygote.";
+    } else {
+      if (exit_code)
+        *exit_code = tmp_exit_code;
+      status = tmp_status;
+    }
+  }
+
+  if (status != base::TERMINATION_STATUS_STILL_RUNNING) {
+    ZygoteChildDied(handle);
+  }
+  return static_cast<base::TerminationStatus>(status);
+}
+
+bool ZygoteCommunication::ShouldUseNamespaceSandbox() {
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+  if (command_line.HasSwitch(switches::kNoSandbox)) {
+    return false;
+  }
+
+  if (command_line.HasSwitch(switches::kDisableNamespaceSandbox)) {
+    return false;
+  }
+
+  if (!sandbox::Credentials::CanCreateProcessInNewUserNS()) {
+    return false;
+  }
+
+  return true;
+}
+
+int ZygoteCommunication::GetSandboxStatus() {
+  if (have_read_sandbox_status_word_) {
+    return sandbox_status_;
+  }
+  if (ReadSandboxStatus() == -1) {
+    return 0;
+  }
+  have_read_sandbox_status_word_ = true;
+  return sandbox_status_;
+}
+
+#endif  // defined(OS_POSIX)
+
+}  // namespace content