OpenBSD-4.6/usr.bin/write/write.c
/* $OpenBSD: write.c,v 1.25 2008/07/06 13:42:35 sobrado Exp $ */
/* $NetBSD: write.c,v 1.5 1995/08/31 21:48:32 jtc 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.
*/
#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1989, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
#if 0
static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95";
#endif
static char *rcsid = "$OpenBSD: write.c,v 1.25 2008/07/06 13:42:35 sobrado Exp $";
#endif /* not lint */
#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 <utmp.h>
#include <err.h>
#include <vis.h>
void done(int sig);
void do_write(char *, char *, uid_t);
void wr_fputs(char *);
void search_utmp(char *, char *, int, char *, uid_t);
int term_chk(char *, int *, time_t *, int);
int utmp_chk(char *, char *);
int
main(int argc, char *argv[])
{
char tty[MAXPATHLEN], *mytty, *cp;
int msgsok, myttyfd;
time_t atime;
uid_t myuid;
/* check that sender has write enabled */
if (isatty(fileno(stdin)))
myttyfd = fileno(stdin);
else if (isatty(fileno(stdout)))
myttyfd = fileno(stdout);
else if (isatty(fileno(stderr)))
myttyfd = fileno(stderr);
else
errx(1, "can't find your tty");
if (!(mytty = ttyname(myttyfd)))
errx(1, "can't find your tty's name");
if ((cp = strrchr(mytty, '/')))
mytty = cp + 1;
if (term_chk(mytty, &msgsok, &atime, 1))
exit(1);
if (!msgsok)
warnx("you have write permission turned off");
myuid = getuid();
/* check args */
switch (argc) {
case 2:
search_utmp(argv[1], tty, sizeof tty, mytty, myuid);
do_write(tty, mytty, myuid);
break;
case 3:
if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
argv[2] += sizeof(_PATH_DEV) - 1;
if (utmp_chk(argv[1], argv[2]))
errx(1, "%s is not logged in on %s",
argv[1], argv[2]);
if (term_chk(argv[2], &msgsok, &atime, 1))
exit(1);
if (myuid && !msgsok)
errx(1, "%s has messages disabled on %s",
argv[1], argv[2]);
do_write(argv[2], mytty, myuid);
break;
default:
(void)fprintf(stderr, "usage: write user [ttyname]\n");
exit(1);
}
done(0);
/* NOTREACHED */
return (0);
}
/*
* utmp_chk - checks that the given user is actually logged in on
* the given tty
*/
int
utmp_chk(char *user, char *tty)
{
struct utmp u;
int ufd;
if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
return(1); /* no utmp, cannot talk to users */
while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
(void)close(ufd);
return(0);
}
(void)close(ufd);
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.
*/
void
search_utmp(char *user, char *tty, int ttyl, char *mytty, uid_t myuid)
{
struct utmp u;
time_t bestatime, atime;
int ufd, nloggedttys, nttys, msgsok, user_is_me;
char atty[UT_LINESIZE + 1];
if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
err(1, "%s", _PATH_UTMP);
nloggedttys = nttys = 0;
bestatime = 0;
user_is_me = 0;
while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
++nloggedttys;
(void)strncpy(atty, u.ut_line, UT_LINESIZE);
atty[UT_LINESIZE] = '\0';
if (term_chk(atty, &msgsok, &atime, 0))
continue; /* bad term? skip */
if (myuid && !msgsok)
continue; /* skip ttys with msgs off */
if (strcmp(atty, mytty) == 0) {
user_is_me = 1;
continue; /* don't write to yourself */
}
++nttys;
if (atime > bestatime) {
bestatime = atime;
(void)strlcpy(tty, atty, ttyl);
}
}
(void)close(ufd);
if (nloggedttys == 0)
errx(1, "%s is not logged in", user);
if (nttys == 0) {
if (user_is_me) { /* ok, so write to yourself! */
(void)strlcpy(tty, mytty, ttyl);
return;
}
errx(1, "%s has messages disabled", user);
} else if (nttys > 1)
warnx("%s is logged in more than once; writing to %s",
user, tty);
}
/*
* term_chk - check that a terminal exists, and get the message bit
* and the access time
*/
int
term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
{
struct stat s;
char path[MAXPATHLEN];
(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
if (stat(path, &s) < 0) {
if (showerror)
warn("%s", path);
return(1);
}
*msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
*atimeP = s.st_atime;
return(0);
}
/*
* do_write - actually make the connection
*/
void
do_write(char *tty, char *mytty, uid_t myuid)
{
char *login, *nows;
struct passwd *pwd;
time_t now;
char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
gid_t gid;
/* Determine our login name before the we reopen() stdout */
if ((login = getlogin()) == NULL) {
if ((pwd = getpwuid(myuid)))
login = pwd->pw_name;
else
login = "???";
}
(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
if ((freopen(path, "w", stdout)) == NULL)
err(1, "%s", path);
/* revoke privs, now that we have opened the tty */
gid = getgid();
if (setresgid(gid, gid, gid) == -1)
err(1, "setresgid");
(void)signal(SIGINT, done);
(void)signal(SIGHUP, done);
/* print greeting */
if (gethostname(host, sizeof(host)) < 0)
(void)strlcpy(host, "???", sizeof host);
now = time((time_t *)NULL);
nows = ctime(&now);
nows[16] = '\0';
(void)printf("\r\n\007\007\007Message 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
*/
void
done(int sig)
{
(void)write(STDOUT_FILENO, "EOF\r\n", 5);
if (sig)
_exit(0);
else
exit(0);
}
/*
* wr_fputs - like fputs(), but makes control characters visible and
* turns \n into \r\n
*/
void
wr_fputs(char *s)
{
u_char c;
char visout[5], *s2;
#define PUTC(c) if (putchar(c) == EOF) goto err;
for (; *s != '\0'; ++s) {
c = toascii(*s);
if (c == '\n') {
PUTC('\r');
PUTC('\n');
continue;
}
vis(visout, c, VIS_SAFE|VIS_NOSLASH, s[1]);
for (s2 = visout; *s2; s2++)
PUTC(*s2);
}
return;
err: err(1, NULL);
#undef PUTC
}