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. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved.
33 * @(#)write.c 8.1 (Berkeley) 6/6/93
34 * $FreeBSD: src/usr.bin/write/write.c,v 1.12 1999/08/28 01:07:48 peter Exp $
35 */
36
37 #include <sys/param.h>
38 #include <sys/stat.h>
39 #include <sys/file.h>
40
41 #include <ctype.h>
42 #include <err.h>
43 #include <locale.h>
44 #include <paths.h>
45 #include <pwd.h>
46 #include <stdio.h>
47 #include <stdlib.h>
48 #include <string.h>
49 #include <signal.h>
50 #include <time.h>
51 #include <unistd.h>
52 #include "utmpentry.h"
53
54 static void done(int);
55 static void do_write(const char *, const char *, uid_t, int *);
56 static void usage(void);
57 static int term_chk(const char *, int *, time_t *, int);
58 static void wr_fputs(unsigned char *s);
59 static void search_utmpx(const char *, char *, size_t, const char *, uid_t);
60 static int utmpx_chk(const char *, const char *);
61
62 int
main(int argc,char ** argv)63 main(int argc, char **argv)
64 {
65 time_t atime;
66 uid_t myuid;
67 int msgsok, mymsgok, myttyfd;
68 char tty[MAXPATHLEN], *mytty;
69
70 setlocale(LC_CTYPE, "");
71
72 /* check that sender has write enabled */
73 if (isatty(fileno(stdin)))
74 myttyfd = fileno(stdin);
75 else if (isatty(fileno(stdout)))
76 myttyfd = fileno(stdout);
77 else if (isatty(fileno(stderr)))
78 myttyfd = fileno(stderr);
79 else
80 errx(1, "can't find your tty");
81 if (!(mytty = ttyname(myttyfd)))
82 errx(1, "can't find your tty's name");
83 if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV)))
84 mytty += strlen(_PATH_DEV);
85 if (term_chk(mytty, &mymsgok, &atime, 1))
86 exit(1);
87 if (!mymsgok)
88 warnx("you have write permission turned off (man mesg)");
89
90 myuid = getuid();
91
92 /* check args */
93 switch (argc) {
94 case 2:
95 search_utmpx(argv[1], tty, sizeof tty, mytty, myuid);
96 do_write(tty, mytty, myuid, &mymsgok);
97 break;
98 case 3:
99 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
100 argv[2] += strlen(_PATH_DEV);
101 if (utmpx_chk(argv[1], argv[2]))
102 errx(1, "%s is not logged in on %s", argv[1], argv[2]);
103 if (term_chk(argv[2], &msgsok, &atime, 1))
104 exit(1);
105 if (myuid && !msgsok)
106 errx(1, "%s has messages disabled on %s", argv[1], argv[2]);
107 do_write(argv[2], mytty, myuid, &mymsgok);
108 break;
109 default:
110 usage();
111 }
112 done(0);
113 return (0);
114 }
115
116 static void
usage(void)117 usage(void)
118 {
119 fprintf(stderr, "usage: write user [tty]\n");
120 exit(1);
121 }
122
123 /*
124 * utmpx_chk - checks that the given user is actually logged in on
125 * the given tty
126 */
127 static int
utmpx_chk(const char * user,const char * tty)128 utmpx_chk(const char *user, const char *tty)
129 {
130 struct utmpentry *ep;
131
132 getutentries(NULL, &ep);
133
134 for (; ep; ep = ep->next) {
135 if (strcmp(user, ep->name) == 0 &&
136 strcmp(tty, ep->line) == 0) {
137 return(0);
138 }
139 }
140
141 return(1);
142 }
143
144 /*
145 * search_utmpx - search utmpx for the "best" terminal to write to
146 *
147 * Ignores terminals with messages disabled, and of the rest, returns
148 * the one with the most recent access time. Returns as value the number
149 * of the user's terminals with messages enabled, or -1 if the user is
150 * not logged in at all.
151 *
152 * Special case for writing to yourself - ignore the terminal you're
153 * writing from, unless that's the only terminal with messages enabled.
154 */
155 static void
search_utmpx(const char * user,char * tty,size_t ttyl,const char * mytty,uid_t myuid)156 search_utmpx(const char *user, char *tty, size_t ttyl, const char *mytty, uid_t myuid)
157 {
158 struct utmpentry *ep;
159 time_t bestatime, atime;
160 int nloggedttys, nttys, msgsok, user_is_me;
161
162 getutentries(NULL, &ep);
163
164 nloggedttys = nttys = 0;
165 bestatime = 0;
166 user_is_me = 0;
167 for (; ep; ep = ep->next)
168 if (strcmp(user, ep->name) == 0) {
169 ++nloggedttys;
170 if (term_chk(ep->line, &msgsok, &atime, 0))
171 continue; /* bad term? skip */
172 if (myuid && !msgsok)
173 continue; /* skip ttys with msgs off */
174 if (strcmp(ep->line, mytty) == 0) {
175 user_is_me = 1;
176 continue; /* don't write to yourself */
177 }
178 ++nttys;
179 if (atime > bestatime) {
180 bestatime = atime;
181 strlcpy(tty, ep->line, ttyl);
182 }
183 }
184
185 if (nloggedttys == 0)
186 errx(1, "%s is not logged in", user);
187 if (nttys == 0) {
188 if (user_is_me) { /* ok, so write to yourself! */
189 strlcpy(tty, mytty, ttyl);
190 return;
191 }
192 errx(1, "%s has messages disabled", user);
193 } else if (nttys > 1) {
194 warnx("%s is logged in more than once; writing to %s", user, tty);
195 }
196 }
197
198 /*
199 * term_chk - check that a terminal exists, and get the message bit
200 * and the access time
201 */
202 static int
term_chk(const char * tty,int * msgsokP,time_t * atimeP,int showerror)203 term_chk(const char *tty, int *msgsokP, time_t *atimeP, int showerror)
204 {
205 struct stat s;
206 char path[MAXPATHLEN];
207
208 snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
209 if (stat(path, &s) < 0) {
210 if (showerror)
211 warn("%s", path);
212 return(1);
213 }
214 *msgsokP = (s.st_mode & S_IWGRP) != 0; /* group write bit */
215 *atimeP = s.st_atime;
216 return(0);
217 }
218
219 /*
220 * do_write - actually make the connection
221 */
222 static void
do_write(const char * tty,const char * mytty,uid_t myuid,int * mymsgok)223 do_write(const char *tty, const char *mytty, uid_t myuid, int *mymsgok)
224 {
225 const char *login;
226 char *nows;
227 struct passwd *pwd;
228 time_t now;
229 char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
230
231 /* Determine our login name before we reopen() stdout */
232 if ((login = getlogin()) == NULL) {
233 if ((pwd = getpwuid(myuid)))
234 login = pwd->pw_name;
235 else
236 login = "???";
237 }
238
239 snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
240 if ((freopen(path, "w", stdout)) == NULL)
241 err(1, "%s", path);
242
243 signal(SIGINT, done);
244 signal(SIGHUP, done);
245
246 /* print greeting */
247 if (gethostname(host, sizeof(host)) < 0)
248 strlcpy(host, "???", sizeof host);
249 now = time(NULL);
250 nows = ctime(&now);
251 nows[16] = '\0';
252 printf("\r\n\007\007\007Message from %s@%s on %s at %s (%s %s replies)...\r\n",
253 login, host, mytty, nows + 11, login, *mymsgok == 0 ? "does not accept" : "accepts");
254
255 while (fgets(line, sizeof(line), stdin) != NULL)
256 wr_fputs(line);
257 }
258
259 /*
260 * done - cleanup and exit
261 */
262 static void
done(__unused int n)263 done(__unused int n)
264 {
265 printf("EOF\r\n");
266 exit(0);
267 }
268
269 /*
270 * wr_fputs - like fputs(), but makes control characters visible and
271 * turns \n into \r\n
272 */
273 static void
wr_fputs(unsigned char * s)274 wr_fputs(unsigned char *s)
275 {
276
277 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL);
278
279 for (; *s != '\0'; ++s) {
280 if (*s == '\n') {
281 PUTC('\r');
282 } else if (((*s & 0x80) && *s < 0xA0) ||
283 /* disable upper controls */
284 (!isprint(*s) && !isspace(*s) &&
285 *s != '\a' && *s != '\b')
286 ) {
287 if (*s & 0x80) {
288 *s &= ~0x80;
289 PUTC('M');
290 PUTC('-');
291 }
292 if (iscntrl(*s)) {
293 *s ^= 0x40;
294 PUTC('^');
295 }
296 }
297 PUTC(*s);
298 }
299 return;
300 #undef PUTC
301 }
302