GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: usr.bin/write/write.c Lines: 0 134 0.0 %
Date: 2017-11-13 Branches: 0 119 0.0 %

Line Branch Exec Source
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/*	$OpenBSD: write.c,v 1.33 2016/02/05 19:00:39 martijn Exp $	*/
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/*	$NetBSD: write.c,v 1.5 1995/08/31 21:48:32 jtc Exp $	*/
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/*
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 * Copyright (c) 1989, 1993
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 *	The Regents of the University of California.  All rights reserved.
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 *
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 * This code is derived from software contributed to Berkeley by
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 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the University nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include <sys/stat.h>
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#include <ctype.h>
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#include <err.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <paths.h>
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#include <pwd.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <unistd.h>
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#include <utmp.h>
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void done(int sig);
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void do_write(char *, char *, uid_t);
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void wr_fputs(char *);
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void search_utmp(char *, char *, int, char *, uid_t);
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int term_chk(char *, int *, time_t *, int);
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int utmp_chk(char *, char *);
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static int isu8cont(unsigned char c);
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int
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main(int argc, char *argv[])
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{
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	char tty[PATH_MAX], *mytty, *cp;
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	int msgsok, myttyfd;
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	time_t atime;
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	uid_t myuid;
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	/* check that sender has write enabled */
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	if (isatty(fileno(stdin)))
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		myttyfd = fileno(stdin);
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	else if (isatty(fileno(stdout)))
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		myttyfd = fileno(stdout);
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	else if (isatty(fileno(stderr)))
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		myttyfd = fileno(stderr);
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	else
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		errx(1, "can't find your tty");
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	if (!(mytty = ttyname(myttyfd)))
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		errx(1, "can't find your tty's name");
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	if ((cp = strrchr(mytty, '/')))
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		mytty = cp + 1;
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	if (term_chk(mytty, &msgsok, &atime, 1))
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		exit(1);
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	if (!msgsok)
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		warnx("you have write permission turned off");
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	myuid = getuid();
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	/* check args */
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	switch (argc) {
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	case 2:
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		search_utmp(argv[1], tty, sizeof tty, mytty, myuid);
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		do_write(tty, mytty, myuid);
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		break;
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	case 3:
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		if (!strncmp(argv[2], _PATH_DEV, sizeof(_PATH_DEV) - 1))
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			argv[2] += sizeof(_PATH_DEV) - 1;
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		if (utmp_chk(argv[1], argv[2]))
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			errx(1, "%s is not logged in on %s",
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			    argv[1], argv[2]);
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		if (term_chk(argv[2], &msgsok, &atime, 1))
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			exit(1);
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		if (myuid && !msgsok)
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			errx(1, "%s has messages disabled on %s",
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			    argv[1], argv[2]);
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		do_write(argv[2], mytty, myuid);
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		break;
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	default:
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		(void)fprintf(stderr, "usage: write user [ttyname]\n");
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		exit(1);
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	}
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	done(0);
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	/* NOTREACHED */
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	return (0);
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}
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/*
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 * utmp_chk - checks that the given user is actually logged in on
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 *     the given tty
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 */
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int
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utmp_chk(char *user, char *tty)
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{
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	struct utmp u;
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	int ufd;
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	if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
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		return(1);	/* no utmp, cannot talk to users */
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	while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
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		if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
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		    strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
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			(void)close(ufd);
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			return(0);
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		}
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	(void)close(ufd);
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	return(1);
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}
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/*
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 * search_utmp - search utmp for the "best" terminal to write to
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 *
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 * Ignores terminals with messages disabled, and of the rest, returns
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 * the one with the most recent access time.  Returns as value the number
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 * of the user's terminals with messages enabled, or -1 if the user is
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 * not logged in at all.
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 *
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 * Special case for writing to yourself - ignore the terminal you're
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 * writing from, unless that's the only terminal with messages enabled.
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 */
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void
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search_utmp(char *user, char *tty, int ttyl, char *mytty, uid_t myuid)
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{
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	struct utmp u;
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	time_t bestatime, atime;
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	int ufd, nloggedttys, nttys, msgsok, user_is_me;
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	char atty[UT_LINESIZE + 1];
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	if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
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		err(1, "%s", _PATH_UTMP);
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	nloggedttys = nttys = 0;
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	bestatime = 0;
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	user_is_me = 0;
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	while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
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		if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
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			++nloggedttys;
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			(void)strncpy(atty, u.ut_line, UT_LINESIZE);
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			atty[UT_LINESIZE] = '\0';
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			if (term_chk(atty, &msgsok, &atime, 0))
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				continue;	/* bad term? skip */
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			if (myuid && !msgsok)
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				continue;	/* skip ttys with msgs off */
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			if (strcmp(atty, mytty) == 0) {
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				user_is_me = 1;
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				continue;	/* don't write to yourself */
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			}
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			++nttys;
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			if (atime > bestatime) {
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				bestatime = atime;
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				(void)strlcpy(tty, atty, ttyl);
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			}
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		}
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	(void)close(ufd);
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	if (nloggedttys == 0)
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		errx(1, "%s is not logged in", user);
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	if (nttys == 0) {
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		if (user_is_me) {		/* ok, so write to yourself! */
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			(void)strlcpy(tty, mytty, ttyl);
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			return;
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		}
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		errx(1, "%s has messages disabled", user);
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	} else if (nttys > 1)
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		warnx("%s is logged in more than once; writing to %s",
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		    user, tty);
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}
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/*
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 * term_chk - check that a terminal exists, and get the message bit
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 *     and the access time
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 */
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int
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term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
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{
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	struct stat s;
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	char path[PATH_MAX];
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	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
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	if (stat(path, &s) < 0) {
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		if (showerror)
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			warn("%s", path);
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		return(1);
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	}
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	*msgsokP = (s.st_mode & S_IWGRP) != 0;	/* group write bit */
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	*atimeP = s.st_atime;
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	return(0);
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}
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/*
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 * do_write - actually make the connection
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 */
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void
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do_write(char *tty, char *mytty, uid_t myuid)
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{
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	char *login, *nows;
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	struct passwd *pwd;
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	time_t now;
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	char path[PATH_MAX], host[HOST_NAME_MAX+1], line[512];
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	gid_t gid;
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	int fd;
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	/* Determine our login name before the we reopen() stdout */
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	if ((login = getlogin()) == NULL) {
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		if ((pwd = getpwuid(myuid)))
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			login = pwd->pw_name;
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		else
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			login = "???";
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	}
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	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
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	fd = open(path, O_WRONLY, 0666);
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	if (fd == -1)
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		err(1, "open %s", path);
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	fflush(stdout);
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	if (dup2(fd, STDOUT_FILENO) == -1)
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		err(1, "dup2 %s", path);
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	if (fd != STDOUT_FILENO)
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		close(fd);
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	/* revoke privs, now that we have opened the tty */
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	gid = getgid();
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	if (setresgid(gid, gid, gid) == -1)
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		err(1, "setresgid");
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	/*
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	 * Unfortunately this is rather late - well after utmp
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	 * parsing, then pinned by the tty open and setresgid
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	 */
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	if (pledge("stdio flock rpath cpath wpath", NULL) == -1)
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		err(1, "pledge");
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	(void)signal(SIGINT, done);
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	(void)signal(SIGHUP, done);
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	/* print greeting */
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	if (gethostname(host, sizeof(host)) < 0)
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		(void)strlcpy(host, "???", sizeof host);
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	now = time(NULL);
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	nows = ctime(&now);
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	nows[16] = '\0';
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	(void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
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	    login, host, mytty, nows + 11);
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	while (fgets(line, sizeof(line), stdin) != NULL)
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		wr_fputs(line);
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}
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/*
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 * done - cleanup and exit
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 */
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void
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done(int sig)
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{
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	(void)write(STDOUT_FILENO, "EOF\r\n", 5);
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	if (sig)
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		_exit(0);
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	else
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		exit(0);
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}
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/*
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 * wr_fputs - like fputs(), but makes control characters visible and
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 *     turns \n into \r\n
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 */
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void
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wr_fputs(char *s)
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{
300
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#define	PUTC(c)	if (putchar(c) == EOF) goto err;
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	for (; *s != '\0'; ++s) {
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		if (*s == '\n') {
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			PUTC('\r');
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			PUTC('\n');
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			continue;
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		}
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		if (isu8cont(*s))
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			continue;
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		if (isprint(*s) || isspace(*s) || *s == '\a') {
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			PUTC(*s);
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		} else {
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			PUTC('?');
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		}
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	}
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	return;
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err:	err(1, NULL);
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#undef PUTC
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}
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static int
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isu8cont(unsigned char c)
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{
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	return (c & (0x80 | 0x40)) == 0x80;
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}