/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* Modified for Linux, Mon Mar 8 18:16:24 1993, faith@cs.unc.edu
* Wed Jun 22 21:41:56 1994, faith@cs.unc.edu:
* Added fix from Mike Grupenhoff (kashmir@umiacs.umd.edu)
* Mon Jul 1 17:01:39 MET DST 1996, janl@math.uio.no:
* - Added fix from David.Chapell@mail.trincoll.edu enabling daemons
* to use write.
* - ANSIed it since I was working on it anyway.
* 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
* - added Native Language Support
*
*/
#include <errno.h>
#include <getopt.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <time.h>
#include <unistd.h>
#include <utmpx.h>
#include "c.h"
#include "carefulputc.h"
#include "closestream.h"
#include "nls.h"
#include "strutils.h"
#include "ttyutils.h"
#include "xalloc.h"
static sig_atomic_t signal_received = 0;
struct write_control {
uid_t src_uid;
const char *src_login;
const char *src_tty_path;
const char *src_tty_name;
const char *dst_login;
char *dst_tty_path;
const char *dst_tty_name;
};
static void __attribute__((__noreturn__)) usage(void)
{
FILE *out = stdout;
fputs(USAGE_HEADER, out);
fprintf(out,
_(" %s [options] <user> [<ttyname>]\n"),
program_invocation_short_name);
fputs(USAGE_SEPARATOR, out);
fputs(_("Send a message to another user.\n"), out);
fputs(USAGE_OPTIONS, out);
printf(USAGE_HELP_OPTIONS(16));
printf(USAGE_MAN_TAIL("write(1)"));
exit(EXIT_SUCCESS);
}
/*
* check_tty - check that a terminal exists, and get the message bit
* and the access time
*/
static int check_tty(const char *tty, int *tty_writeable, time_t *tty_atime, int showerror)
{
struct stat s;
if (stat(tty, &s) < 0) {
if (showerror)
warn("%s", tty);
return 1;
}
if (getuid() == 0) /* root can always write */
*tty_writeable = 1;
else {
if (getegid() != s.st_gid) {
warnx(_("effective gid does not match group of %s"), tty);
return 1;
}
*tty_writeable = s.st_mode & S_IWGRP;
}
if (tty_atime)
*tty_atime = s.st_atime;
return 0;
}
/*
* check_utmp - checks that the given user is actually logged in on
* the given tty
*/
static int check_utmp(const struct write_control *ctl)
{
struct utmpx *u;
int res = 1;
utmpxname(_PATH_UTMP);
setutxent();
while ((u = getutxent())) {
if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) == 0 &&
strncmp(ctl->dst_tty_name, u->ut_line, sizeof(u->ut_line)) == 0) {
res = 0;
break;
}
}
endutxent();
return res;
}
/*
* search_utmp - search utmp for the "best" terminal to write to
*
* Ignores terminals with messages disabled, and of the rest, returns
* the one with the most recent access time. Returns as value the number
* of the user's terminals with messages enabled, or -1 if the user is
* not logged in at all.
*
* Special case for writing to yourself - ignore the terminal you're
* writing from, unless that's the only terminal with messages enabled.
*/
static void search_utmp(struct write_control *ctl)
{
struct utmpx *u;
time_t best_atime = 0, tty_atime;
int num_ttys = 0, valid_ttys = 0, tty_writeable = 0, user_is_me = 0;
char path[sizeof(u->ut_line) + 6];
utmpxname(_PATH_UTMP);
setutxent();
while ((u = getutxent())) {
if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) != 0)
continue;
num_ttys++;
sprintf(path, "/dev/%s", u->ut_line);
if (check_tty(path, &tty_writeable, &tty_atime, 0))
/* bad term? skip */
continue;
if (ctl->src_uid && !tty_writeable)
/* skip ttys with msgs off */
continue;
if (strcmp(u->ut_line, ctl->src_tty_name) == 0) {
user_is_me = 1;
/* don't write to yourself */
continue;
}
if (u->ut_type != USER_PROCESS)
/* it's not a valid entry */
continue;
valid_ttys++;
if (best_atime < tty_atime) {
best_atime = tty_atime;
free(ctl->dst_tty_path);
ctl->dst_tty_path = xstrdup(path);
ctl->dst_tty_name = ctl->dst_tty_path + 5;
}
}
endutxent();
if (num_ttys == 0)
errx(EXIT_FAILURE, _("%s is not logged in"), ctl->dst_login);
if (valid_ttys == 0) {
if (user_is_me) {
/* ok, so write to yourself! */
if (!ctl->src_tty_path)
errx(EXIT_FAILURE, _("can't find your tty's name"));
ctl->dst_tty_path = xstrdup(ctl->src_tty_path);
ctl->dst_tty_name = ctl->dst_tty_path + 5;
return;
}
errx(EXIT_FAILURE, _("%s has messages disabled"), ctl->dst_login);
}
if (1 < valid_ttys)
warnx(_("%s is logged in more than once; writing to %s"),
ctl->dst_login, ctl->dst_tty_name);
}
/*
* signal_handler - cause write loop to exit
*/
static void signal_handler(int signo)
{
signal_received = signo;
}
/*
* write_line - like fputs(), but makes control characters visible and
* turns \n into \r\n.
*/
static void write_line(char *s)
{
while (*s) {
const int c = *s++;
if ((c == '\n' && fputc_careful('\r', stdout, '^') == EOF)
|| fputc_careful(c, stdout, '^') == EOF)
err(EXIT_FAILURE, _("carefulputc failed"));
}
}
/*
* do_write - actually make the connection
*/
static void do_write(const struct write_control *ctl)
{
char *login, *pwuid;
struct passwd *pwd;
time_t now;
struct tm *tm;
char *host, line[512];
struct sigaction sigact;
/* Determine our login name(s) before the we reopen() stdout */
if ((pwd = getpwuid(ctl->src_uid)) != NULL)
pwuid = pwd->pw_name;
else
pwuid = "???";
if ((login = getlogin()) == NULL)
login = pwuid;
if ((freopen(ctl->dst_tty_path, "w", stdout)) == NULL)
err(EXIT_FAILURE, "%s", ctl->dst_tty_path);
sigact.sa_handler = signal_handler;
sigemptyset(&sigact.sa_mask);
sigact.sa_flags = 0;
sigaction(SIGINT, &sigact, NULL);
sigaction(SIGHUP, &sigact, NULL);
host = xgethostname();
if (!host)
host = xstrdup("???");
now = time((time_t *)NULL);
tm = localtime(&now);
/* print greeting */
printf("\r\n\a\a\a");
if (strcmp(login, pwuid))
printf(_("Message from %s@%s (as %s) on %s at %02d:%02d ..."),
login, host, pwuid, ctl->src_tty_name,
tm->tm_hour, tm->tm_min);
else
printf(_("Message from %s@%s on %s at %02d:%02d ..."),
login, host, ctl->src_tty_name,
tm->tm_hour, tm->tm_min);
free(host);
printf("\r\n");
while (fgets(line, sizeof(line), stdin) != NULL) {
if (signal_received)
break;
write_line(line);
}
printf("EOF\r\n");
}
int main(int argc, char **argv)
{
int tty_writeable = 0, c;
struct write_control ctl = { 0 };
static const struct option longopts[] = {
{"version", no_argument, NULL, 'V'},
{"help", no_argument, NULL, 'h'},
{NULL, 0, NULL, 0}
};
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
close_stdout_atexit();
while ((c = getopt_long(argc, argv, "Vh", longopts, NULL)) != -1)
switch (c) {
case 'V':
print_version(EXIT_SUCCESS);
case 'h':
usage();
default:
errtryhelp(EXIT_FAILURE);
}
if (get_terminal_name(&ctl.src_tty_path, &ctl.src_tty_name, NULL) == 0) {
/* check that sender has write enabled */
if (check_tty(ctl.src_tty_path, &tty_writeable, NULL, 1))
exit(EXIT_FAILURE);
if (!tty_writeable)
errx(EXIT_FAILURE,
_("you have write permission turned off"));
tty_writeable = 0;
} else
ctl.src_tty_name = "<no tty>";
ctl.src_uid = getuid();
/* check args */
switch (argc) {
case 2:
ctl.dst_login = argv[1];
search_utmp(&ctl);
do_write(&ctl);
break;
case 3:
ctl.dst_login = argv[1];
if (!strncmp(argv[2], "/dev/", 5))
ctl.dst_tty_path = xstrdup(argv[2]);
else
xasprintf(&ctl.dst_tty_path, "/dev/%s", argv[2]);
ctl.dst_tty_name = ctl.dst_tty_path + 5;
if (check_utmp(&ctl))
errx(EXIT_FAILURE,
_("%s is not logged in on %s"),
ctl.dst_login, ctl.dst_tty_name);
if (check_tty(ctl.dst_tty_path, &tty_writeable, NULL, 1))
exit(EXIT_FAILURE);
if (ctl.src_uid && !tty_writeable)
errx(EXIT_FAILURE,
_("%s has messages disabled on %s"),
ctl.dst_login, ctl.dst_tty_name);
do_write(&ctl);
break;
default:
errtryhelp(EXIT_FAILURE);
}
free(ctl.dst_tty_path);
return EXIT_SUCCESS;
}
