flatpak/app/flatpak-builtins-enter.c

/*
 * Copyright © 2014 Red Hat, Inc
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 * Authors:
 *       Alexander Larsson <alexl@redhat.com>
 */

#include "config.h"

#include <locale.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>

#include <glib/gi18n.h>

#include "libglnx/libglnx.h"

#include "flatpak-builtins.h"
#include "flatpak-utils.h"
#include "flatpak-dbus.h"
#include "flatpak-run.h"


static GOptionEntry options[] = {
  { NULL }
};


gboolean
flatpak_builtin_enter (int           argc,
                       char        **argv,
                       GCancellable *cancellable,
                       GError      **error)
{
  g_autoptr(GOptionContext) context = NULL;
  int rest_argv_start, rest_argc;
  const char *ns_name[] = { "ipc", "net", "pid", "mnt", "user" };
  int ns_fd[G_N_ELEMENTS (ns_name)];
  char pid_ns[256] = { 0 };
  ssize_t pid_ns_len;
  char self_ns[256];
  ssize_t self_ns_len;
  char *pid_s;
  int pid, i;
  g_autofree char *environment_path = NULL;
  g_autoptr(GPtrArray) argv_array = NULL;
  g_autoptr(GPtrArray) envp_array = NULL;
  g_autofree char *environment = NULL;
  gsize environment_len;
  char *e;
  g_autofree char *pulse_path = NULL;
  g_autofree char *session_bus_path = NULL;
  g_autofree char *xdg_runtime_dir = NULL;
  g_autofree char *stat_path = NULL;
  g_autofree char *root_path = NULL;
  char root_link[256] = { 0 };
  gssize root_link_len;
  g_autofree char *cwd_path = NULL;
  char cwd_link[256] = { 0 };
  gssize cwd_link_len;
  int status;
  struct stat stat_buf;
  uid_t uid;
  gid_t gid;

  context = g_option_context_new (_("SANDBOXEDPID [COMMAND [args...]] - Run a command inside a running sandbox"));
  g_option_context_set_translation_domain (context, GETTEXT_PACKAGE);

  rest_argc = 0;
  for (i = 1; i < argc; i++)
    {
      /* The non-option is the command, take it out of the arguments */
      if (argv[i][0] != '-')
        {
          rest_argv_start = i;
          rest_argc = argc - i;
          argc = i;
          break;
        }
    }

  if (!flatpak_option_context_parse (context, options, &argc, &argv, FLATPAK_BUILTIN_FLAG_NO_DIR, NULL, cancellable, error))
    return FALSE;

  if (rest_argc < 2)
    {
      usage_error (context, _("SANDBOXEDPID and COMMAND must be specified"), error);
      return FALSE;
    }

  /* Before further checks, warn if we are not already root */
  if (geteuid () != 0)
    g_printerr ("%s\n", _("Not running as root, may be unable to enter namespace"));

  pid_s = argv[rest_argv_start];

  pid = atoi (pid_s);
  if (pid <= 0)
    return flatpak_fail (error, _("Invalid pid %s"), pid_s);

  stat_path = g_strdup_printf ("/proc/%d/root", pid);
  if (stat (stat_path, &stat_buf))
    return flatpak_fail (error, _("No such pid %s"), pid_s);

  uid = stat_buf.st_uid;
  gid = stat_buf.st_gid;

  environment_path = g_strdup_printf ("/proc/%d/environ", pid);
  if (!g_file_get_contents (environment_path, &environment, &environment_len, error))
    return FALSE;

  cwd_path = g_strdup_printf ("/proc/%d/cwd", pid);
  cwd_link_len = readlink (cwd_path, cwd_link, sizeof (cwd_link) - 1);
  if (cwd_link_len <= 0)
    return flatpak_fail (error, _("Can't read cwd"));

  root_path = g_strdup_printf ("/proc/%d/root", pid);
  root_link_len = readlink (root_path, root_link, sizeof (root_link) - 1);
  if (root_link_len <= 0)
    return flatpak_fail (error, _("Can't read root"));

  for (i = 0; i < G_N_ELEMENTS (ns_name); i++)
    {
      g_autofree char *path = g_strdup_printf ("/proc/%d/ns/%s", pid, ns_name[i]);
      g_autofree char *self_path = g_strdup_printf ("/proc/self/ns/%s", ns_name[i]);

      pid_ns_len = readlink (path, pid_ns, sizeof (pid_ns) - 1);
      if (pid_ns_len <= 0)
        return flatpak_fail (error, _("Invalid %s namespace for pid %d"), ns_name[i], pid);
      pid_ns[pid_ns_len] = 0;

      self_ns_len = readlink (self_path, self_ns, sizeof (self_ns) - 1);
      if (self_ns_len <= 0)
        return flatpak_fail (error, _("Invalid %s namespace for self"), ns_name[i]);
      self_ns[self_ns_len] = 0;

      if (strcmp (self_ns, pid_ns) == 0)
        {
          /* No need to setns to the same namespace, it will only fail */
          ns_fd[i] = -1;
        }
      else
        {
          ns_fd[i] = open (path, O_RDONLY);
          if (ns_fd[i] == -1)
            return flatpak_fail (error, _("Can't open %s namespace: %s"), ns_name[i], g_strerror (errno));
        }
    }

  for (i = 0; i < G_N_ELEMENTS (ns_fd); i++)
    {
      if (ns_fd[i] != -1)
        {
          if (setns (ns_fd[i], 0) == -1)
            return flatpak_fail (error, _("Can't enter %s namespace: %s"), ns_name[i], g_strerror (errno));
          close (ns_fd[i]);
        }
    }

  if (chdir (cwd_link))
    return flatpak_fail (error, _("Can't chdir"));

  if (chroot (root_link))
    return flatpak_fail (error, _("Can't chroot"));

  envp_array = g_ptr_array_new_with_free_func (g_free);
  for (e = environment; e < environment + environment_len; e = e + strlen (e) + 1)
    {
      if (*e != 0 &&
          !g_str_has_prefix (e, "DISPLAY=") &&
          !g_str_has_prefix (e, "PULSE_SERVER=") &&
          !g_str_has_prefix (e, "PULSE_CLIENTCONFIG=") &&
          !g_str_has_prefix (e, "XDG_RUNTIME_DIR=") &&
          !g_str_has_prefix (e, "DBUS_SYSTEM_BUS_ADDRESS=") &&
          !g_str_has_prefix (e, "DBUS_SESSION_BUS_ADDRESS="))
        {
          if (g_str_has_prefix (e, "_LD_LIBRARY_PATH="))
            e++;
          g_ptr_array_add (envp_array, g_strdup (e));
        }
    }

  xdg_runtime_dir = g_strdup_printf ("/run/user/%d", uid);
  g_ptr_array_add (envp_array, g_strdup_printf ("XDG_RUNTIME_DIR=%s", xdg_runtime_dir));

  if (g_file_test ("/tmp/.X11-unix/X99", G_FILE_TEST_EXISTS))
    g_ptr_array_add (envp_array, g_strdup ("DISPLAY=:99.0"));

  pulse_path = g_strdup_printf ("/run/user/%d/pulse/native", uid);
  if (g_file_test (pulse_path, G_FILE_TEST_EXISTS))
    {
      g_ptr_array_add (envp_array, g_strdup_printf ("PULSE_SERVER=unix:%s", pulse_path));
      g_ptr_array_add (envp_array, g_strdup_printf ("PULSE_CLIENTCONFIG=/run/user/%d/pulse/config", uid));
    }

  session_bus_path = g_strdup_printf ("/run/user/%d/bus", uid);
  if (g_file_test (session_bus_path, G_FILE_TEST_EXISTS))
    g_ptr_array_add (envp_array, g_strdup_printf ("DBUS_SESSION_BUS_ADDRESS=unix:%s", session_bus_path));

  if (g_file_test ("/run/dbus/system_bus_socket", G_FILE_TEST_EXISTS))
    g_ptr_array_add (envp_array, g_strdup ("DBUS_SYSTEM_BUS_ADDRESS=unix:/run/dbus/system_bus_socket"));

  g_ptr_array_add (envp_array, NULL);

  argv_array = g_ptr_array_new_with_free_func (g_free);
  for (i = 1; i < rest_argc; i++)
    g_ptr_array_add (argv_array, g_strdup (argv[rest_argv_start + i]));
  g_ptr_array_add (argv_array, NULL);

  if (setgid (gid))
    return flatpak_fail (error, _("Can't switch gid"));

  if (setuid (uid))
    return flatpak_fail (error, _("Can't switch uid"));

  if (!g_spawn_sync (NULL, (char **) argv_array->pdata, (char **) envp_array->pdata,
                     G_SPAWN_SEARCH_PATH_FROM_ENVP | G_SPAWN_CHILD_INHERITS_STDIN,
                     NULL, NULL,
                     NULL, NULL,
                     &status, error))
    return FALSE;

  exit (status);
}

gboolean
flatpak_complete_enter (FlatpakCompletion *completion)
{
  g_autoptr(GOptionContext) context = NULL;

  context = g_option_context_new ("");
  if (!flatpak_option_context_parse (context, options, &completion->argc, &completion->argv, FLATPAK_BUILTIN_FLAG_NO_DIR, NULL, NULL, NULL))
    return FALSE;

  switch (completion->argc)
    {
    case 0:
    case 1:
      flatpak_complete_options (completion, global_entries);
      flatpak_complete_options (completion, options);
      break;

    default:
      break;
    }

  return TRUE;
}