sysvinit/src/mesg.c
Petter Reinholdtsen 2fe47a3c9f Drop hurd specific dependency on libc0.3 (>= 2.3.2.ds1-12). It is
no longer needed according to Michael Bunk.  Patch from Michael
Biebl.
2009-09-10 08:28:49 +00:00

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;
}