write.c revision 29430 
1/*
2 * Copyright (c) 1989, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#ifndef lint
38static const char copyright[] =
39"@(#) Copyright (c) 1989, 1993\n\
40	The Regents of the University of California.  All rights reserved.\n";
41#endif /* not lint */
42
43#ifndef lint
44#if 0
45static char sccsid[] = "@(#)write.c	8.1 (Berkeley) 6/6/93";
46#endif
47static const char rcsid[] =
48	"$Id: write.c,v 1.7 1997/08/26 11:23:37 charnier Exp $";
49#endif /* not lint */
50
51#include <sys/param.h>
52#include <sys/signal.h>
53#include <sys/stat.h>
54#include <sys/file.h>
55#include <sys/time.h>
56#include <ctype.h>
57#include <err.h>
58#include <locale.h>
59#include <paths.h>
60#include <pwd.h>
61#include <stdio.h>
62#include <string.h>
63#include <unistd.h>
64#include <utmp.h>
65
66void done __P((int));
67void do_write __P((char *, char *, uid_t));
68static void usage __P((void));
69int term_chk __P((char *, int *, time_t *, int));
70void wr_fputs __P((unsigned char *s));
71void search_utmp __P((char *, char *, char *, uid_t));
72int utmp_chk __P((char *, char *));
73
74int
75main(argc, argv)
76	int argc;
77	char **argv;
78{
79	register char *cp;
80	time_t atime;
81	uid_t myuid;
82	int msgsok, myttyfd;
83	char tty[MAXPATHLEN], *mytty;
84
85	(void)setlocale(LC_CTYPE, "");
86
87	/* check that sender has write enabled */
88	if (isatty(fileno(stdin)))
89		myttyfd = fileno(stdin);
90	else if (isatty(fileno(stdout)))
91		myttyfd = fileno(stdout);
92	else if (isatty(fileno(stderr)))
93		myttyfd = fileno(stderr);
94	else
95		errx(1, "can't find your tty");
96	if (!(mytty = ttyname(myttyfd)))
97		errx(1, "can't find your tty's name");
98	if ((cp = rindex(mytty, '/')))
99		mytty = cp + 1;
100	if (term_chk(mytty, &msgsok, &atime, 1))
101		exit(1);
102	if (!msgsok)
103		errx(1, "you have write permission turned off");
104
105	myuid = getuid();
106
107	/* check args */
108	switch (argc) {
109	case 2:
110		search_utmp(argv[1], tty, mytty, myuid);
111		do_write(tty, mytty, myuid);
112		break;
113	case 3:
114		if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
115			argv[2] += strlen(_PATH_DEV);
116		if (utmp_chk(argv[1], argv[2]))
117			errx(1, "%s is not logged in on %s", argv[1], argv[2]);
118		if (term_chk(argv[2], &msgsok, &atime, 1))
119			exit(1);
120		if (myuid && !msgsok)
121			errx(1, "%s has messages disabled on %s", argv[1], argv[2]);
122		do_write(argv[2], mytty, myuid);
123		break;
124	default:
125		usage();
126	}
127	done(0);
128	return (0);
129}
130
131static void
132usage()
133{
134	(void)fprintf(stderr, "usage: write user [tty]\n");
135	exit(1);
136}
137
138/*
139 * utmp_chk - checks that the given user is actually logged in on
140 *     the given tty
141 */
142int
143utmp_chk(user, tty)
144	char *user, *tty;
145{
146	struct utmp u;
147	int ufd;
148
149	if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
150		return(0);	/* ignore error, shouldn't happen anyway */
151
152	while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
153		if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
154		    strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
155			(void)close(ufd);
156			return(0);
157		}
158
159	(void)close(ufd);
160	return(1);
161}
162
163/*
164 * search_utmp - search utmp for the "best" terminal to write to
165 *
166 * Ignores terminals with messages disabled, and of the rest, returns
167 * the one with the most recent access time.  Returns as value the number
168 * of the user's terminals with messages enabled, or -1 if the user is
169 * not logged in at all.
170 *
171 * Special case for writing to yourself - ignore the terminal you're
172 * writing from, unless that's the only terminal with messages enabled.
173 */
174void
175search_utmp(user, tty, mytty, myuid)
176	char *user, *tty, *mytty;
177	uid_t myuid;
178{
179	struct utmp u;
180	time_t bestatime, atime;
181	int ufd, nloggedttys, nttys, msgsok, user_is_me;
182	char atty[UT_LINESIZE + 1];
183
184	if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
185		err(1, "utmp");
186
187	nloggedttys = nttys = 0;
188	bestatime = 0;
189	user_is_me = 0;
190	while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
191		if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
192			++nloggedttys;
193			(void)strncpy(atty, u.ut_line, UT_LINESIZE);
194			atty[UT_LINESIZE] = '\0';
195			if (term_chk(atty, &msgsok, &atime, 0))
196				continue;	/* bad term? skip */
197			if (myuid && !msgsok)
198				continue;	/* skip ttys with msgs off */
199			if (strcmp(atty, mytty) == 0) {
200				user_is_me = 1;
201				continue;	/* don't write to yourself */
202			}
203			++nttys;
204			if (atime > bestatime) {
205				bestatime = atime;
206				(void)strcpy(tty, atty);
207			}
208		}
209
210	(void)close(ufd);
211	if (nloggedttys == 0)
212		errx(1, "%s is not logged in", user);
213	if (nttys == 0) {
214		if (user_is_me) {		/* ok, so write to yourself! */
215			(void)strcpy(tty, mytty);
216			return;
217		}
218		errx(1, "%s has messages disabled", user);
219	} else if (nttys > 1) {
220		warnx("%s is logged in more than once; writing to %s", user, tty);
221	}
222}
223
224/*
225 * term_chk - check that a terminal exists, and get the message bit
226 *     and the access time
227 */
228int
229term_chk(tty, msgsokP, atimeP, showerror)
230	char *tty;
231	int *msgsokP, showerror;
232	time_t *atimeP;
233{
234	struct stat s;
235	char path[MAXPATHLEN];
236
237	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
238	if (stat(path, &s) < 0) {
239		if (showerror)
240			warn("%s", path);
241		return(1);
242	}
243	*msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0;	/* group write bit */
244	*atimeP = s.st_atime;
245	return(0);
246}
247
248/*
249 * do_write - actually make the connection
250 */
251void
252do_write(tty, mytty, myuid)
253	char *tty, *mytty;
254	uid_t myuid;
255{
256	register char *login, *nows;
257	register struct passwd *pwd;
258	time_t now;
259	char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
260
261	/* Determine our login name before the we reopen() stdout */
262	if ((login = getlogin()) == NULL)
263		if ((pwd = getpwuid(myuid)))
264			login = pwd->pw_name;
265		else
266			login = "???";
267
268	(void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
269	if ((freopen(path, "w", stdout)) == NULL)
270		err(1, "%s", path);
271
272	(void)signal(SIGINT, done);
273	(void)signal(SIGHUP, done);
274
275	/* print greeting */
276	if (gethostname(host, sizeof(host)) < 0)
277		(void)strcpy(host, "???");
278	now = time((time_t *)NULL);
279	nows = ctime(&now);
280	nows[16] = '\0';
281	(void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
282	    login, host, mytty, nows + 11);
283
284	while (fgets(line, sizeof(line), stdin) != NULL)
285		wr_fputs(line);
286}
287
288/*
289 * done - cleanup and exit
290 */
291void
292done(n)
293int n;  /* signal number */
294{
295	(void)printf("EOF\r\n");
296	exit(0);
297}
298
299/*
300 * wr_fputs - like fputs(), but makes control characters visible and
301 *     turns \n into \r\n
302 */
303void
304wr_fputs(s)
305	register unsigned char *s;
306{
307
308#define	PUTC(c)	if (putchar(c) == EOF) err(1, NULL);
309
310	for (; *s != '\0'; ++s) {
311		if (*s == '\n') {
312			PUTC('\r');
313		} else if (*s <= 0xA0 || /* disable upper controls */
314			   (!isprint(*s) && !isspace(*s) && *s != '\007')
315			  ) {
316			if (*s & 0x80) {
317				*s &= ~0x80;
318				PUTC('M');
319				PUTC('-');
320			}
321			if (iscntrl(*s)) {
322				*s ^= 0x40;
323				PUTC('^');
324			}
325		}
326		PUTC(*s);
327	}
328	return;
329#undef PUTC
330}
331