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 Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the 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    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    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 For bug reporting instructions, please see:\n\
  90 <http://www.gnu.org/software/libc/bugs.html>.\n"));
  91       return cp;
  92     default:
  93       break;
  94     }
  95   return (char *) text;
  96 }
  97
  98 static int
  99 do_pt_chown (void)
 100 {
 101   char *pty;
 102   struct stat st;
 103   struct group *p;
 104   gid_t gid;
 105
 106   /* Check that PTY_FILENO is a valid master pseudo terminal.  */
 107   pty = ptsname (PTY_FILENO);
 108   if (pty == NULL)
 109     return errno == EBADF ? FAIL_EBADF : FAIL_EINVAL;
 110
 111   /* Check that the returned slave pseudo terminal is a
 112      character device.  */
 113   if (stat (pty, &st) < 0 || !S_ISCHR(st.st_mode))
 114     return FAIL_EINVAL;
 115
 116   /* Get the group ID of the special `tty' group.  */
 117   p = getgrnam (TTY_GROUP);
 118   gid = p ? p->gr_gid : getgid ();
 119
 120   /* Set the owner to the real user ID, and the group to that special
 121      group ID.  */
 122   if (chown (pty, getuid (), gid) < 0)
 123     return FAIL_EACCES;
 124
 125   /* Set the permission mode to readable and writable by the owner,
 126      and writable by the group.  */
 127   if (chmod (pty, S_IRUSR|S_IWUSR|S_IWGRP) < 0)
 128     return FAIL_EACCES;
 129
 130   return 0;
 131 }
 132
 133
 134 int
 135 main (int argc, char *argv[])
 136 {
 137   uid_t euid = geteuid ();
 138   int remaining;
 139
 140   /* Normal invocation of this program is with no arguments and
 141      with privileges.
 142      FIXME: Should use capable (CAP_CHOWN|CAP_FOWNER).  */
 143   if (argc == 1 && euid == 0)
 144     return do_pt_chown ();
 145
 146   /* We aren't going to be using privileges, so drop them right now. */
 147   setuid (getuid ());
 148
 149   /* Set locale via LC_ALL.  */
 150   setlocale (LC_ALL, "");
 151
 152   /* Set the text message domain.  */
 153   textdomain (PACKAGE);
 154
 155   /* parse and process arguments.  */
 156   argp_parse (&argp, argc, argv, 0, &remaining, NULL);
 157
 158   if (remaining < argc)
 159     {
 160       /* We should not be called with any non-option parameters.  */
 161       error (0, 0, gettext ("too many arguments"));
 162       argp_help (&argp, stdout, ARGP_HELP_SEE | ARGP_HELP_EXIT_ERR,
 163                  program_invocation_short_name);
 164       return EXIT_FAILURE;
 165     }
 166
 167   /* Check if we are properly installed.  */
 168   if (euid != 0)
 169     error (FAIL_EXEC, 0, gettext ("needs to be installed setuid `root'"));
 170
 171   return EXIT_SUCCESS;
 172 }