login_manager/system_utils_impl.cc

// Copyright (c) 2012 The Chromium OS 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 "login_manager/system_utils_impl.h"

#include <errno.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#include <limits>
#include <string>
#include <vector>

#include <base/files/file_path.h>
#include <base/files/file_util.h>
#include <base/files/important_file_writer.h>
#include <base/files/scoped_temp_dir.h>
#include <base/logging.h>
#include <base/process/launch.h>
#include <base/strings/string_util.h>
#include <base/sys_info.h>
#include <base/time/time.h>
#include <brillo/process.h>
#include <chromeos/dbus/service_constants.h>

using std::string;
using std::vector;

namespace login_manager {

namespace {

bool LaunchAndWait(const vector<string>& argv, int* out_exit_code) {
  base::Process process(base::LaunchProcess(argv, base::LaunchOptions()));
  if (!process.IsValid()) {
    PLOG(ERROR) << "Failed to create a process for '"
                << base::JoinString(argv, " ") << "'";
    return false;
  }
  if (!process.WaitForExit(out_exit_code)) {
    PLOG(ERROR) << "Failed to wait for '" << base::JoinString(argv, " ")
                << "' to exit";
    return false;
  }
  return true;
}

}  // namespace

SystemUtilsImpl::SystemUtilsImpl()
    : dev_mode_state_(DevModeState::DEV_MODE_UNKNOWN),
      vm_state_(VmState::UNKNOWN) {
}

SystemUtilsImpl::~SystemUtilsImpl() {
}

DevModeState SystemUtilsImpl::GetDevModeState() {
  // Return the cached result when possible. There is no reason to run
  // crossytem twice as cros_debug is always read-only.
  if (dev_mode_state_ == DevModeState::DEV_MODE_UNKNOWN) {
    int exit_code = -1;
    if (LaunchAndWait({"crossystem", "cros_debug?0"}, &exit_code)) {
      switch (exit_code) {
        case 0:
          dev_mode_state_ = DevModeState::DEV_MODE_OFF;
          break;
        case 1:
          dev_mode_state_ = DevModeState::DEV_MODE_ON;
          break;
        default:
          LOG(ERROR) << "Unexpected exit code from crossystem: " << exit_code;
          break;
      }
    }
  }
  return dev_mode_state_;
}

VmState SystemUtilsImpl::GetVmState() {
  // Return the cached result when possible. There is no reason to run
  // crossystem twice as inside_vm is always read-only.
  if (vm_state_ == VmState::UNKNOWN) {
    int exit_code = -1;
    if (LaunchAndWait({"crossystem", "inside_vm?0"}, &exit_code)) {
      switch (exit_code) {
        case 0:
          vm_state_ = VmState::OUTSIDE_VM;
          break;
        case 1:
          vm_state_ = VmState::INSIDE_VM;
          break;
        default:
          LOG(ERROR) << "Unexpected exit code from crossystem: " << exit_code;
          break;
      }
    }
  }
  return vm_state_;
}

int SystemUtilsImpl::kill(pid_t pid, uid_t owner, int signal) {
  LOG(INFO) << "Sending " << signal << " to " << pid << " as " << owner;
  uid_t uid, euid, suid;
  getresuid(&uid, &euid, &suid);
  if (setresuid(owner, owner, -1)) {
    PLOG(ERROR) << "Couldn't assume uid " << owner;
    return -1;
  }
  int ret = ::kill(pid, signal);
  if (setresuid(uid, euid, -1)) {
    PLOG(ERROR) << "Couldn't return to root";
    return -1;
  }
  return ret;
}

time_t SystemUtilsImpl::time(time_t* t) {
  return ::time(t);
}

pid_t SystemUtilsImpl::fork() {
  return ::fork();
}

bool SystemUtilsImpl::ProcessGroupIsGone(pid_t child_spec,
                                         base::TimeDelta timeout) {
  base::TimeTicks start = base::TimeTicks::Now();
  base::TimeDelta elapsed;
  int ret;

  DCHECK_GE(timeout.InSeconds(), 0);
  DCHECK_LE(timeout.InSeconds(),
            static_cast<int64_t>(std::numeric_limits<int>::max()));
  alarm(static_cast<int32_t>(timeout.InSeconds()));
  do {
    errno = 0;
    ret = ::waitpid(-child_spec, NULL, 0);
    elapsed = base::TimeTicks::Now() - start;
  } while (ret > 0 || (errno == EINTR && elapsed < timeout));

  // Once we exit the loop, we know there was an error.
  alarm(0);
  return errno == ECHILD;  // EINTR means we timed out.
}

bool SystemUtilsImpl::EnsureAndReturnSafeFileSize(const base::FilePath& file,
                                                  int32_t* file_size_32) {
  const base::FilePath file_in_base_dir = PutInsideBaseDir(file);
  // Get the file size (must fit in a 32 bit int for NSS).
  int64_t file_size;
  if (!base::GetFileSize(file_in_base_dir, &file_size)) {
    LOG(ERROR) << "Could not get size of " << file_in_base_dir.value();
    return false;
  }
  if (file_size > static_cast<int64_t>(std::numeric_limits<int32_t>::max())) {
    LOG(ERROR) << file_in_base_dir.value() << "is " << file_size
               << "bytes!!!  Too big!";
    return false;
  }
  *file_size_32 = static_cast<int32_t>(file_size);
  return true;
}

bool SystemUtilsImpl::Exists(const base::FilePath& file) {
  return base::PathExists(PutInsideBaseDir(file));
}

bool SystemUtilsImpl::CreateReadOnlyFileInTempDir(base::FilePath* temp_file) {
  if (!temp_dir_.IsValid() && !temp_dir_.CreateUniqueTempDir())
    return false;
  base::FilePath local_temp_file;
  if (base::CreateTemporaryFileInDir(temp_dir_.path(), &local_temp_file)) {
    if (chmod(local_temp_file.value().c_str(), 0644) == 0) {
      *temp_file = local_temp_file;
      return true;
    } else {
      PLOG(ERROR) << "Can't chmod " << local_temp_file.value() << " to 0644.";
    }
    RemoveFile(local_temp_file);
  }
  return false;
}

bool SystemUtilsImpl::GetUniqueFilenameInWriteOnlyTempDir(
    base::FilePath* temp_file_path) {
  // Create a temporary directory to put the testing channel in.
  // It will be made write-only below; we need to be able to read it
  // when trying to create a unique name inside it.
  base::FilePath temp_dir_path;
  if (!base::CreateNewTempDirectory(FILE_PATH_LITERAL(""), &temp_dir_path)) {
    PLOG(ERROR) << "Can't create temp dir";
    return false;
  }
  // Create a temporary file in the temporary directory, to be deleted later.
  // This ensures a unique name.
  if (!base::CreateTemporaryFileInDir(temp_dir_path, temp_file_path)) {
    PLOG(ERROR) << "Can't get temp file name in " << temp_dir_path.value();
    return false;
  }
  // Now, allow access to non-root processes.
  if (chmod(temp_dir_path.value().c_str(), 0333)) {
    PLOG(ERROR) << "Can't chmod " << temp_file_path->value() << " to 0333.";
    return false;
  }
  if (!RemoveFile(*temp_file_path)) {
    PLOG(ERROR) << "Can't clear temp file in " << temp_file_path->value();
    return false;
  }
  return true;
}

bool SystemUtilsImpl::RemoveDirTree(const base::FilePath& dir) {
  const base::FilePath dir_in_base_dir = PutInsideBaseDir(dir);
  if (!base::DirectoryExists(dir_in_base_dir))
    return false;
  return base::DeleteFile(dir_in_base_dir, true);
}

bool SystemUtilsImpl::RemoveFile(const base::FilePath& filename) {
  const base::FilePath filename_in_base_dir = PutInsideBaseDir(filename);
  if (base::DirectoryExists(filename_in_base_dir))
    return false;
  return base::DeleteFile(filename_in_base_dir, false);
}

bool SystemUtilsImpl::AtomicFileWrite(const base::FilePath& filename,
                                      const std::string& data) {
  const base::FilePath filename_in_base_dir = PutInsideBaseDir(filename);
  return (
      base::ImportantFileWriter::WriteFileAtomically(
          filename_in_base_dir, data) &&
      base::SetPosixFilePermissions(
          filename_in_base_dir, (S_IRUSR | S_IWUSR | S_IROTH)));
}

bool SystemUtilsImpl::DirectoryExists(const base::FilePath& dir) {
  return base::DirectoryExists(PutInsideBaseDir(dir));
}

bool SystemUtilsImpl::CreateTemporaryDirIn(const base::FilePath& parent_dir,
                                           base::FilePath* out_dir) {
  return base::CreateTemporaryDirInDir(
      PutInsideBaseDir(parent_dir), "temp", out_dir);
}

bool SystemUtilsImpl::RenameDir(const base::FilePath& source,
                                const base::FilePath& target) {
  const base::FilePath source_in_base_dir = PutInsideBaseDir(source);
  if (!base::DirectoryExists(source_in_base_dir))
    return false;
  return base::ReplaceFile(
      source_in_base_dir, PutInsideBaseDir(target), nullptr);
}

bool SystemUtilsImpl::CreateDir(const base::FilePath& dir) {
  return base::CreateDirectoryAndGetError(PutInsideBaseDir(dir), nullptr);
}

bool SystemUtilsImpl::IsDirectoryEmpty(const base::FilePath& dir) {
  const base::FilePath dir_in_base_dir = PutInsideBaseDir(dir);
  return !base::DirectoryExists(dir_in_base_dir) ||
      base::IsDirectoryEmpty(dir_in_base_dir);
}

int64_t SystemUtilsImpl::AmountOfFreeDiskSpace(const base::FilePath& path) {
  return base::SysInfo::AmountOfFreeDiskSpace(path);
}

base::FilePath SystemUtilsImpl::PutInsideBaseDirForTesting(
    const base::FilePath& path) {
  return PutInsideBaseDir(path);
}

base::FilePath SystemUtilsImpl::PutInsideBaseDir(const base::FilePath& path) {
  if (base_dir_for_testing_.empty())
    return path;  // for production, this function does nothing.

  if (base_dir_for_testing_.IsParent(path))
    return path;  // already chroot'ed.

  base::FilePath to_append(path);
  while (to_append.IsAbsolute()) {
    std::string ascii(path.MaybeAsASCII());
    to_append = base::FilePath(ascii.substr(1, std::string::npos));
  }
  return base_dir_for_testing_.Append(to_append);
}

}  // namespace login_manager