flatpak/common/flatpak-bwrap.c

/*
 * Copyright © 2014-2018 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 <string.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/utsname.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/personality.h>
#include <grp.h>
#include <unistd.h>
#include <gio/gunixfdlist.h>

#include <glib/gi18n.h>

#include <gio/gio.h>
#include "libglnx/libglnx.h"

#include "flatpak-bwrap.h"
#include "flatpak-utils.h"

static void
clear_fd (gpointer data)
{
  int *fd_p = data;
  if (fd_p != NULL && *fd_p != -1)
    close (*fd_p);
}

FlatpakBwrap *
flatpak_bwrap_new (char **env)
{
  FlatpakBwrap *bwrap = g_new0 (FlatpakBwrap, 1);

  bwrap->argv = g_ptr_array_new_with_free_func (g_free);
  bwrap->fds = g_array_new (FALSE, TRUE, sizeof (int));
  g_array_set_clear_func (bwrap->fds, clear_fd);

  if (env)
    bwrap->envp = g_strdupv (env);
  else
    bwrap->envp = g_get_environ ();

  return bwrap;
}

void
flatpak_bwrap_free (FlatpakBwrap *bwrap)
{
  g_ptr_array_unref (bwrap->argv);
  g_array_unref (bwrap->fds);
  g_strfreev (bwrap->envp);
  g_free (bwrap);
}

void
flatpak_bwrap_set_env (FlatpakBwrap *bwrap,
                       const char  *variable,
                       const char  *value,
                       gboolean      overwrite)
{
  bwrap->envp = g_environ_setenv (bwrap->envp, variable, value, overwrite);
}

void
flatpak_bwrap_unset_env (FlatpakBwrap *bwrap,
                         const char  *variable)
{
  bwrap->envp = g_environ_unsetenv (bwrap->envp, variable);
}

void
flatpak_bwrap_add_args (FlatpakBwrap *bwrap, ...)
{
  va_list args;
  const gchar *arg;

  va_start (args, bwrap);
  while ((arg = va_arg (args, const gchar *)))
    g_ptr_array_add (bwrap->argv, g_strdup (arg));
  va_end (args);
}

void
flatpak_bwrap_append_argsv (FlatpakBwrap *bwrap,
                            char **args,
                            int len)
{
  int i;

  if (len < 0)
    len = g_strv_length (args);

  for (i = 0; i < len; i++)
    g_ptr_array_add (bwrap->argv, g_strdup (args[i]));
}

void
flatpak_bwrap_append_args (FlatpakBwrap *bwrap,
                           GPtrArray *other_array)
{
  flatpak_bwrap_append_argsv (bwrap,
                              (char **)other_array->pdata,
                              other_array->len);
}

void
flatpak_bwrap_add_args_data_fd (FlatpakBwrap *bwrap,
                                const char *op,
                                int fd,
                                const char *path_optional)
{
  g_autofree char *fd_str = g_strdup_printf ("%d", fd);

  g_array_append_val (bwrap->fds, fd);
  flatpak_bwrap_add_args (bwrap,
                          op, fd_str, path_optional,
                          NULL);
}


/* Given a buffer @content of size @content_size, generate a fd (memfd if available)
 * of the data.  The @name parameter is used by memfd_create() as a debugging aid;
 * it has no semantic meaning.  The bwrap command line will inject it into the target
 * container as @path.
 */
gboolean
flatpak_bwrap_add_args_data (FlatpakBwrap *bwrap,
                             const char *name,
                             const char *content,
                             gssize content_size,
                             const char *path,
                             GError **error)
{
  g_auto(GLnxTmpfile) args_tmpf  = { 0, };

  if (!flatpak_buffer_to_sealed_memfd_or_tmpfile (&args_tmpf, name, content, content_size, error))
    return FALSE;

  flatpak_bwrap_add_args_data_fd (bwrap, "--bind-data", glnx_steal_fd (&args_tmpf.fd), path);
  return TRUE;
}

/* This resolves the target here rather than in bwrap, because it may
 * not resolve in bwrap setup due to absolute symlinks conflicting
 * with /newroot root. For example, dest could be inside
 * ~/.var/app/XXX where XXX is an absolute symlink.  However, in the
 * usecases here the destination file often doesn't exist, so we
 * only resolve the directory part.
 */
void
flatpak_bwrap_add_bind_arg (FlatpakBwrap *bwrap,
                            const char *type,
                            const char *src,
                            const char *dest)
{
  g_autofree char *dest_dirname = g_path_get_dirname (dest);
  g_autofree char *dest_dirname_real = realpath (dest_dirname, NULL);

  if (dest_dirname_real)
    {
      g_autofree char *dest_basename = g_path_get_basename (dest);
      g_autofree char *dest_real = g_build_filename (dest_dirname_real, dest_basename, NULL);
      flatpak_bwrap_add_args (bwrap, type, src, dest_real, NULL);
    }
}