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/*
* broadcast.c
* broadcast a message to every logged in user
*/
/*
* Copyright 2018 Sony Interactive Entertainment Inc.
*
* This file is part of OpenRC. It is subject to the license terms in
* the LICENSE file found in the top-level directory of this
* distribution and at https://github.com/OpenRC/openrc/blob/HEAD/LICENSE
* This file may not be copied, modified, propagated, or distributed
* except according to the terms contained in the LICENSE file.
*/
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <stdio.h>
#include <utmp.h>
#include <utmpx.h>
#include <pwd.h>
#include <fcntl.h>
#include <signal.h>
#include <setjmp.h>
#include <paths.h>
#include <sys/utsname.h>
#include "broadcast.h"
#include "helpers.h"
#ifndef _PATH_DEV
# define _PATH_DEV "/dev/"
#endif
static sigjmp_buf jbuf;
/*
* Alarm handler
*/
/*ARGSUSED*/
_noreturn static void handler(int arg _unused)
{
siglongjmp(jbuf, 1);
}
static void getuidtty(char **userp, char **ttyp)
{
struct passwd *pwd;
uid_t uid;
char *tty;
static char uidbuf[32];
char *ttynm = NULL;
uid = getuid();
if ((pwd = getpwuid(uid)) != NULL) {
uidbuf[0] = 0;
strncat(uidbuf, pwd->pw_name, sizeof(uidbuf) - 1);
} else {
if (uid)
sprintf(uidbuf, "uid %d", (int) uid);
else
sprintf(uidbuf, "root");
}
if ((tty = ttyname(0)) != NULL) {
const size_t plen = strlen(_PATH_DEV);
if (strncmp(tty, _PATH_DEV, plen) == 0) {
tty += plen;
if (tty[0] == '/')
tty++;
}
xasprintf(&ttynm, "(%s) ", tty);
}
*userp = uidbuf;
*ttyp = ttynm;
}
/*
* Check whether the given filename looks like a tty device.
*/
static int file_isatty(const char *fname)
{
struct stat st;
int major;
if (stat(fname, &st) < 0)
return 0;
if (st.st_nlink != 1 || !S_ISCHR(st.st_mode))
return 0;
/*
* It would be an impossible task to list all major/minors
* of tty devices here, so we just exclude the obvious
* majors of which just opening has side-effects:
* printers and tapes.
*/
major = major(st.st_dev);
if (major == 1 || major == 2 || major == 6 || major == 9 ||
major == 12 || major == 16 || major == 21 || major == 27 ||
major == 37 || major == 96 || major == 97 || major == 206 ||
major == 230)
return 0;
return 1;
}
/*
* broadcast function.
*
* NB: Not multithread safe.
*/
void broadcast(char *text)
{
char *tty;
char *user;
struct utsname name;
time_t t;
char *date;
char *p;
char *line = NULL;
struct sigaction sa;
int flags;
char *term = NULL;
struct utmpx *utmp;
/*
* These are set across the sigsetjmp call, so they can't be stored on
* the stack, otherwise they might be clobbered.
*/
static int fd;
static FILE *tp;
getuidtty(&user, &tty);
/*
* Get and report current hostname, to make it easier to find out
* which machine is being shut down.
*/
uname(&name);
/* Get the time */
time(&t);
date = ctime(&t);
p = strchr(date, '\n');
if (p)
*p = 0;
xasprintf(&line, "\007\r\nBroadcast message from %s@%s %s(%s):\r\n\r\n",
user, name.nodename, tty, date);
free(tty);
/*
* Fork to avoid hanging in a write()
*/
if (fork() != 0)
return;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = handler;
sigemptyset(&sa.sa_mask);
sigaction(SIGALRM, &sa, NULL);
setutxent();
while ((utmp = getutxent()) != NULL) {
if (utmp->ut_type != USER_PROCESS || utmp->ut_user[0] == 0)
continue;
if (strncmp(utmp->ut_line, _PATH_DEV, strlen(_PATH_DEV)) == 0)
xasprintf(&term, "%s", utmp->ut_line);
else
xasprintf(&term, "%s%s", _PATH_DEV, utmp->ut_line);
if (strstr(term, "/../")) {
free(term);
continue;
}
/*
* Open it non-delay
*/
if (sigsetjmp(jbuf, 1) == 0) {
alarm(2);
flags = O_WRONLY|O_NDELAY|O_NOCTTY;
if (file_isatty(term) && (fd = open(term, flags)) >= 0) {
if (isatty(fd) && (tp = fdopen(fd, "w")) != NULL) {
fputs(line, tp);
fputs(text, tp);
fflush(tp);
}
}
}
alarm(0);
if (fd >= 0)
close(fd);
if (tp != NULL)
fclose(tp);
free(term);
}
endutxent();
free(line);
exit(0);
}
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