125 lines
2.8 KiB
C
125 lines
2.8 KiB
C
/*
|
|
* mesg.c The "mesg" utility. Gives / restrict access to
|
|
* your terminal by others.
|
|
*
|
|
* Usage: mesg [y|n].
|
|
* Without arguments prints out the current settings.
|
|
*
|
|
* This file is part of the sysvinit suite,
|
|
* Copyright (C) 1991-2001 Miquel van Smoorenburg.
|
|
*
|
|
* 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 of the License, 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <errno.h>
|
|
#include <unistd.h>
|
|
#include <grp.h>
|
|
|
|
char *Version = "@(#) mesg 2.81 31-Jul-2001 miquels@cistron.nl";
|
|
|
|
#define TTYGRP "tty"
|
|
|
|
/*
|
|
* See if the system has a special 'tty' group.
|
|
* If it does, and the tty device is in that group,
|
|
* we set the modes to -rw--w--- instead if -rw--w--w.
|
|
*/
|
|
int hasttygrp(void)
|
|
{
|
|
struct group *grp;
|
|
|
|
if ((grp = getgrnam(TTYGRP)) != NULL)
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
|
|
/*
|
|
* See if the tty devices group is indeed 'tty'
|
|
*/
|
|
int tty_in_ttygrp(struct stat *st)
|
|
{
|
|
struct group *gr;
|
|
|
|
if ((gr = getgrgid(st->st_gid)) == NULL)
|
|
return 0;
|
|
if (strcmp(gr->gr_name, TTYGRP) != 0)
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
int main(int argc, char **argv)
|
|
{
|
|
struct stat st;
|
|
unsigned int ttymode, st_mode_old;
|
|
int ht;
|
|
int it;
|
|
int e;
|
|
|
|
if (!isatty(0)) {
|
|
/* Or should we look in /var/run/utmp? */
|
|
fprintf(stderr, "stdin: is not a tty\n");
|
|
return(1);
|
|
}
|
|
|
|
if (fstat(0, &st) < 0) {
|
|
perror("fstat");
|
|
return(1);
|
|
}
|
|
|
|
ht = hasttygrp();
|
|
it = tty_in_ttygrp(&st);
|
|
|
|
if (argc < 2) {
|
|
ttymode = (ht && it) ? 020 : 002;
|
|
printf("is %s\n", (st.st_mode & ttymode) ? "y" : "n");
|
|
return 0;
|
|
}
|
|
if (argc > 2 || (argv[1][0] != 'y' && argv[1][0] != 'n')) {
|
|
fprintf(stderr, "Usage: mesg [y|n]\n");
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Security check: allow mesg n when group is
|
|
* weird, but don't allow mesg y.
|
|
*/
|
|
ttymode = ht ? 020 : 022;
|
|
if (ht && !it && argv[1][0] == 'y') {
|
|
fprintf(stderr, "mesg: error: tty device is not owned "
|
|
"by group `%s'\n", TTYGRP);
|
|
exit(1);
|
|
}
|
|
|
|
st_mode_old = st.st_mode;
|
|
if (argv[1][0] == 'y')
|
|
st.st_mode |= ttymode;
|
|
else
|
|
st.st_mode &= ~(ttymode);
|
|
if (st_mode_old != st.st_mode && fchmod(0, st.st_mode) != 0) {
|
|
e = errno;
|
|
fprintf(stderr, "mesg: %s: %s\n",
|
|
ttyname(0), strerror(e));
|
|
exit(1);
|
|
}
|
|
|
|
return 0;
|
|
}
|