/* $NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $ */
/*
* 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. 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.
*/
#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
The Regents of the University of California. All rights reserved.");
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95";
#else
__RCSID("$NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $");
#endif
#endif /* not lint */
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <time.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <unistd.h>
#include <err.h>
#include <errno.h>
#include "utmpentry.h"
#include "term_chk.h"
__dead static void done(int);
static void do_write(int, const char *, const uid_t);
static void wr_fputs(char *);
static int search_utmp(char *, char *, uid_t, gid_t);
static int utmp_chk(const char *, const char *);
int
main(int argc, char **argv)
{
time_t atime;
uid_t myuid, uid;
int msgsok, ttyfd;
char *mytty;
gid_t saved_egid = getegid();
if (setegid(getgid()) == -1)
err(1, "setegid");
myuid = getuid();
ttyfd = -1;
mytty = check_sender(&atime, myuid, saved_egid);
/* check args */
switch (argc) {
case 2:
ttyfd = search_utmp(argv[1], mytty, myuid, saved_egid);
break;
case 3:
if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
argv[2] += strlen(_PATH_DEV);
if (uid_from_user(argv[1], &uid) == -1)
errx(1, "%s: unknown user", argv[1]);
if (utmp_chk(argv[1], argv[2]))
errx(1, "%s is not logged in on %s",
argv[1], argv[2]);
ttyfd = term_chk(uid, argv[2], &msgsok, &atime, 0, saved_egid);
if (ttyfd == -1)
err(1, "%s%s", _PATH_DEV, argv[2]);
if (myuid && !msgsok)
errx(1, "%s has messages disabled on %s",
argv[1], argv[2]);
break;
default:
(void)fprintf(stderr, "usage: write user [tty]\n");
exit(1);
}
if (setgid(getgid()) == -1)
err(1, "setgid");
do_write(ttyfd, mytty, myuid);
done(0);
/* NOTREACHED */
#ifdef __GNUC__
return (0);
#endif
}
/*
* utmp_chk - checks that the given user is actually logged in on
* the given tty
*/
static int
utmp_chk(const char *user, const char *tty)
{
struct utmpentry *ep;
(void)getutentries(NULL, &ep);
for (; ep; ep = ep->next)
if (strcmp(user, ep->name) == 0 && strcmp(tty, ep->line) == 0)
return(0);
return(1);
}
/*
* 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 int
search_utmp(char *user, char *mytty, uid_t myuid, gid_t saved_egid)
{
char tty[MAXPATHLEN];
time_t bestatime, atime;
int nloggedttys, nttys, msgsok, user_is_me;
struct utmpentry *ep;
int fd, nfd;
uid_t uid;
if (uid_from_user(user, &uid) == -1)
errx(1, "%s: unknown user", user);
(void)getutentries(NULL, &ep);
nloggedttys = nttys = 0;
bestatime = 0;
user_is_me = 0;
fd = -1;
for (; ep; ep = ep->next)
if (strcmp(user, ep->name) == 0) {
++nloggedttys;
nfd = term_chk(uid, ep->line, &msgsok, &atime, 0,
saved_egid);
if (nfd == -1)
continue; /* bad term? skip */
if (myuid && !msgsok) {
close(nfd);
continue; /* skip ttys with msgs off */
}
if (strcmp(ep->line, mytty) == 0) {
user_is_me = 1;
if (fd == -1)
fd = nfd;
else
close(nfd);
continue; /* don't write to yourself */
}
++nttys;
if (atime > bestatime) {
bestatime = atime;
(void)strlcpy(tty, ep->line, sizeof(tty));
close(fd);
fd = nfd;
} else
close(nfd);
}
if (nloggedttys == 0)
errx(1, "%s is not logged in", user);
if (nttys == 0) {
if (user_is_me) /* ok, so write to yourself! */
return fd;
errx(1, "%s has messages disabled", user);
} else if (nttys > 1)
warnx("%s is logged in more than once; writing to %s",
user, tty);
return fd;
}
/*
* do_write - actually make the connection
*/
static void
do_write(int ttyfd, const char *mytty, const uid_t myuid)
{
const char *login;
char *nows;
struct passwd *pwd;
time_t now;
char host[MAXHOSTNAMELEN + 1], line[512];
/* Determine our login name before we re-open stdout */
if ((login = getlogin()) == NULL) {
if ((pwd = getpwuid(myuid)) != NULL)
login = pwd->pw_name;
else login = "???";
}
if (dup2(ttyfd, STDOUT_FILENO) == -1)
err(1, "dup2");
(void)signal(SIGINT, done);
(void)signal(SIGHUP, done);
(void)close(ttyfd);
/* print greeting */
if (gethostname(host, sizeof(host)) < 0)
(void)strlcpy(host, "???", sizeof(host));
else
host[sizeof(host) - 1] = '\0';
now = time(NULL);
nows = ctime(&now);
nows[16] = '\0';
(void)printf("\r\n\a\a\aMessage from %s@%s on %s at %s ...\r\n",
login, host, mytty, nows + 11);
while (fgets(line, sizeof(line), stdin) != NULL)
wr_fputs(line);
}
/*
* done - cleanup and exit
*/
static void
done(int signo)
{
(void)write(STDOUT_FILENO, "EOF\r\n", sizeof("EOF\r\n") - 1);
if (signo == 0)
exit(0);
else
_exit(0);
}
/*
* wr_fputs - like fputs(), but makes control characters visible and
* turns \n into \r\n
*/
static void
wr_fputs(char *s)
{
unsigned char c;
#define PUTC(c) if (putchar(c) == EOF) goto err;
for (; *s != '\0'; ++s) {
c = toascii(*s);
if (c == '\n') {
PUTC('\r');
} else if (!isprint(c) && !isspace(c) && c != '\a') {
PUTC('^');
c ^= 0x40; /* DEL to ?, others to alpha */
}
PUTC(c);
}
return;
err: err(1, NULL);
#undef PUTC
}
