/* setuidgid - run a command with the UID and GID of a specified user
   Copyright (C) 2003 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Written by Jim Meyering  */

#include <config.h>
#include <stdio.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>

#include "system.h"

#include "error.h"
#include "long-options.h"
#include "quote.h"

#define PROGRAM_NAME "setuidgid"

/* I wrote this program from scratch, based on the description of
   D.J. Bernstein's program: http://cr.yp.to/daemontools/setuidgid.html.  */
#define WRITTEN_BY _("Written by Jim Meyering.")

#define FAIL_STATUS 111

char *program_name;

void
usage (int status)
{
  if (status != 0)
    fprintf (stderr, _("Try `%s --help' for more information.\n"),
	     program_name);
  else
    {
      printf (_("\
Usage: %s USERNAME COMMAND [ARGUMENT]...\n\
  or:  %s OPTION\n\
"),
	      program_name, program_name);

      fputs (_("\
Drop any supplemental groups, assume the user-ID and group-ID of\n\
the specified USERNAME, and run COMMAND with any specified ARGUMENTs.\n\
Exit with status 111 if unable to assume the required UID and GID.\n\
Otherwise, exit with the exit status of COMMAND.\n\
This program is useful only when run by root (UID=0).\n\
\n\
"), stdout);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
    }
  exit (status);
}

int
main (int argc, char **argv)
{
  char const *user_id;
  struct passwd *pwd;

  initialize_main (&argc, &argv);
  program_name = argv[0];
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  atexit (close_stdout);

  parse_long_options (argc, argv, PROGRAM_NAME, GNU_PACKAGE, VERSION,
		      WRITTEN_BY, usage);

  /* The above handles --help and --version.
     Since there is no other invocation of getopt, handle `--' here.  */
  if (argc > 1 && STREQ (argv[1], "--"))
    {
      --argc;
      ++argv;
    }

  if (argc <= 2)
    {
      error (0, 0, _("too few arguments"));
      usage (FAIL_STATUS);
    }

  user_id = argv[1];
  pwd = getpwnam (user_id);
  if (pwd == NULL)
    {
      error (0, errno, _("unknown user-ID: %s"), quote (user_id));
      exit (FAIL_STATUS);
    }

  if (setgroups (1, &pwd->pw_gid))
    {
      error (0, errno, _("cannot set supplemental group"));
      exit (FAIL_STATUS);
    }

  if (setgid (pwd->pw_gid))
    {
      error (0, errno, _("cannot set group-ID to %ld"), (long) pwd->pw_gid);
      exit (FAIL_STATUS);
    }

  if (setuid (pwd->pw_uid))
    {
      error (0, errno, _("cannot set user-ID to %ld"), (long) pwd->pw_uid);
      exit (FAIL_STATUS);
    }

  {
    char **cmd = argv + 2;
    execvp (*cmd, cmd);

    error (0, errno, _("cannot run command %s"), quote (*cmd));
    exit (FAIL_STATUS);
  }
}