login/programs/pt_chown.c

   1 /* pt_chmod - helper program for `grantpt'.
   2    Copyright (C) 1998, 1999 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by C. Scott Ananian <cananian@alumni.princeton.edu>, 1998.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <argp.h>
  22 #include <errno.h>
  23 #include <error.h>
  24 #include <grp.h>
  25 #include <libintl.h>
  26 #include <locale.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <sys/stat.h>
  31 #include <unistd.h>
  32
  33 #include "pty-private.h"
  34
  35 /* Get libc version number.  */
  36 #include "../version.h"
  37
  38 #define PACKAGE _libc_intl_domainname
  39
  40 /* Name and version of program.  */
  41 static void print_version (FILE *stream, struct argp_state *state);
  42 void (*argp_program_version_hook) (FILE *, struct argp_state *) = print_version;
  43
  44 /* Function to print some extra text in the help message.  */
  45 static char *more_help (int key, const char *text, void *input);
  46
  47 /* Data structure to communicate with argp functions.  */
  48 static struct argp argp =
  49 {
  50   NULL, NULL, NULL, NULL, NULL, more_help
  51 };
  52
  53
  54 /* Print the version information.  */
  55 static void
  56 print_version (FILE *stream, struct argp_state *state)
  57 {
  58   fprintf (stream, "pt_chown (GNU %s) %s\n", PACKAGE, VERSION);
  59   fprintf (stream, gettext ("\
  60 Copyright (C) %s Free Software Foundation, Inc.\n\
  61 This is free software; see the source for copying conditions.  There is NO\n\
  62 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
  63 "), "1999");
  64 }
  65
  66 static char *
  67 more_help (int key, const char *text, void *input)
  68 {
  69   char *cp;
  70
  71   switch (key)
  72     {
  73     case ARGP_KEY_HELP_PRE_DOC:
  74       asprintf (&cp, gettext ("\
  75 Set the owner, group and access permission of the slave pseudo\
  76  terminal corresponding to the master pseudo terminal passed on\
  77  file descriptor `%d'.  This is the helper program for the\
  78  `grantpt' function.  It is not intended to be run directly from\
  79  the command line.\n"),
  80                 PTY_FILENO);
  81       return cp;
  82     case ARGP_KEY_HELP_EXTRA:
  83       /* We print some extra information.  */
  84       asprintf (&cp, gettext ("\
  85 The owner is set to the current user, the group is set to `%s',\
  86  and the access permission is set to `%o'.\n\n\
  87 %s"),
  88                 TTY_GROUP, S_IRUSR|S_IWUSR|S_IWGRP, gettext ("\
  89 Report bugs using the `glibcbug' script to <bugs@gnu.org>.\n"));
  90       return cp;
  91     default:
  92       break;
  93     }
  94   return (char *) text;
  95 }
  96
  97 int
  98 do_pt_chown (void)
  99 {
 100   char *pty;
 101   struct stat st;
 102   struct group *p;
 103   gid_t gid;
 104
 105   /* Check that PTY_FILENO is a valid master pseudo terminal.  */
 106   pty = ptsname (PTY_FILENO);
 107   if (pty == NULL)
 108     return errno == EBADF ? FAIL_EBADF : FAIL_EINVAL;
 109
 110   /* Check that the returned slave pseudo terminal is a
 111      character device.  */
 112   if (stat (pty, &st) < 0 || !S_ISCHR(st.st_mode))
 113     return FAIL_EINVAL;
 114
 115   /* Get the group ID of the special `tty' group.  */
 116   p = getgrnam (TTY_GROUP);
 117   gid = p ? p->gr_gid : getgid ();
 118
 119   /* Set the owner to the real user ID, and the group to that special
 120      group ID.  */
 121   if (chown (pty, getuid (), gid) < 0)
 122     return FAIL_EACCES;
 123
 124   /* Set the permission mode to readable and writable by the owner,
 125      and writable by the group.  */
 126   if (chmod (pty, S_IRUSR|S_IWUSR|S_IWGRP) < 0)
 127     return FAIL_EACCES;
 128
 129   return 0;
 130 }
 131
 132
 133 int
 134 main (int argc, char *argv[])
 135 {
 136   uid_t euid = geteuid ();
 137   int remaining;
 138
 139   /* Normal invocation of this program is with no arguments and
 140      with privileges.
 141      FIXME: Should use capable (CAP_CHOWN|CAP_FOWNER).  */
 142   if (argc == 1 && euid == 0)
 143     return do_pt_chown ();
 144
 145   /* We aren't going to be using privileges, so drop them right now. */
 146   setuid (getuid ());
 147
 148   /* Set locale via LC_ALL.  */
 149   setlocale (LC_ALL, "");
 150
 151   /* Set the text message domain.  */
 152   textdomain (PACKAGE);
 153
 154   /* parse and process arguments.  */
 155   argp_parse (&argp, argc, argv, 0, &remaining, NULL);
 156
 157   if (remaining < argc)
 158     {
 159       /* We should not be called with any non-option parameters.  */
 160       error (0, 0, gettext ("too many arguments"));
 161       argp_help (&argp, stdout, ARGP_HELP_SEE | ARGP_HELP_EXIT_ERR,
 162                  program_invocation_short_name);
 163       return EXIT_FAILURE;
 164     }
 165
 166   /* Check if we are properly installed.  */
 167   if (euid != 0)
 168     error (FAIL_EXEC, 0, gettext ("needs to be installed setuid `root'"));
 169
 170   return EXIT_SUCCESS;
 171 }