1 /*
2 * Copyright (c) 1989 The Regents of the University of California.
3 * 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
38 char copyright[] =
39 "@(#) Copyright (c) 1989 The Regents of the University of California.\n\
40 All rights reserved.\n";
41 #endif /* not lint */
42
43 #ifndef lint
44 static char sccsid[] = "@(#)write.c 4.22 (Berkeley) 6/1/90";
45 #endif /* not lint */
46
47 #include <sys/param.h>
48 #include <sys/signal.h>
49 #include <sys/stat.h>
50 #include <sys/file.h>
51 #include <sys/time.h>
52 #include <utmp.h>
53 #include <ctype.h>
54 #include <pwd.h>
55 #include <stdio.h>
56 #include <string.h>
57
58 extern int errno;
59
main(argc,argv)60 main(argc, argv)
61 int argc;
62 char **argv;
63 {
64 register char *cp;
65 time_t atime;
66 uid_t myuid;
67 int msgsok, myttyfd;
68 char tty[PATH_MAX], *mytty, *ttyname();
69 void done();
70
71 /* check that sender has write enabled */
72 if (isatty(fileno(stdin)))
73 myttyfd = fileno(stdin);
74 else if (isatty(fileno(stdout)))
75 myttyfd = fileno(stdout);
76 else if (isatty(fileno(stderr)))
77 myttyfd = fileno(stderr);
78 else {
79 (void)fprintf(stderr, "write: can't find your tty\n");
80 exit(1);
81 }
82 if (!(mytty = ttyname(myttyfd))) {
83 (void)fprintf(stderr, "write: can't find your tty's name\n");
84 exit(1);
85 }
86 if (cp = rindex(mytty, '/'))
87 mytty = cp + 1;
88 if (term_chk(mytty, &msgsok, &atime, 1))
89 exit(1);
90 if (!msgsok) {
91 (void)fprintf(stderr,
92 "write: you have write permission turned off.\n");
93 exit(1);
94 }
95
96 myuid = getuid();
97
98 /* check args */
99 switch (argc) {
100 case 2:
101 search_utmp(argv[1], tty, mytty, myuid);
102 do_write(tty, mytty, myuid);
103 break;
104 case 3:
105 if (!strncmp(argv[2], "/dev/", 5))
106 argv[2] += 5;
107 if (utmp_chk(argv[1], argv[2])) {
108 (void)fprintf(stderr,
109 "write: %s is not logged in on %s.\n",
110 argv[1], argv[2]);
111 exit(1);
112 }
113 if (term_chk(argv[2], &msgsok, &atime, 1))
114 exit(1);
115 if (myuid && !msgsok) {
116 (void)fprintf(stderr,
117 "write: %s has messages disabled on %s\n",
118 argv[1], argv[2]);
119 exit(1);
120 }
121 do_write(argv[2], mytty, myuid);
122 break;
123 default:
124 (void)fprintf(stderr, "usage: write user [tty]\n");
125 exit(1);
126 }
127 done();
128 /* NOTREACHED */
129 }
130
131 /*
132 * utmp_chk - checks that the given user is actually logged in on
133 * the given tty
134 */
utmp_chk(user,tty)135 utmp_chk(user, tty)
136 char *user, *tty;
137 {
138 struct utmp u;
139 int ufd;
140
141 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
142 return(0); /* ignore error, shouldn't happen anyway */
143
144 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
145 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
146 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
147 (void)close(ufd);
148 return(0);
149 }
150
151 (void)close(ufd);
152 return(1);
153 }
154
155 /*
156 * search_utmp - search utmp for the "best" terminal to write to
157 *
158 * Ignores terminals with messages disabled, and of the rest, returns
159 * the one with the most recent access time. Returns as value the number
160 * of the user's terminals with messages enabled, or -1 if the user is
161 * not logged in at all.
162 *
163 * Special case for writing to yourself - ignore the terminal you're
164 * writing from, unless that's the only terminal with messages enabled.
165 */
search_utmp(user,tty,mytty,myuid)166 search_utmp(user, tty, mytty, myuid)
167 char *user, *tty, *mytty;
168 uid_t myuid;
169 {
170 struct utmp u;
171 time_t bestatime, atime;
172 int ufd, nloggedttys, nttys, msgsok, user_is_me;
173 char atty[UT_LINESIZE + 1];
174
175 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0) {
176 perror("utmp");
177 exit(1);
178 }
179
180 nloggedttys = nttys = 0;
181 bestatime = 0;
182 user_is_me = 0;
183 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
184 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
185 ++nloggedttys;
186 (void)strncpy(atty, u.ut_line, UT_LINESIZE);
187 atty[UT_LINESIZE] = '\0';
188 if (term_chk(atty, &msgsok, &atime, 0))
189 continue; /* bad term? skip */
190 if (myuid && !msgsok)
191 continue; /* skip ttys with msgs off */
192 if (strcmp(atty, mytty) == 0) {
193 user_is_me = 1;
194 continue; /* don't write to yourself */
195 }
196 ++nttys;
197 if (atime > bestatime) {
198 bestatime = atime;
199 (void)strcpy(tty, atty);
200 }
201 }
202
203 (void)close(ufd);
204 if (nloggedttys == 0) {
205 (void)fprintf(stderr, "write: %s is not logged in\n", user);
206 exit(1);
207 }
208 if (nttys == 0) {
209 if (user_is_me) { /* ok, so write to yourself! */
210 (void)strcpy(tty, mytty);
211 return;
212 }
213 (void)fprintf(stderr,
214 "write: %s has messages disabled\n", user);
215 exit(1);
216 } else if (nttys > 1) {
217 (void)fprintf(stderr,
218 "write: %s is logged in more than once; writing to %s\n",
219 user, tty);
220 }
221 }
222
223 /*
224 * term_chk - check that a terminal exists, and get the message bit
225 * and the access time
226 */
term_chk(tty,msgsokP,atimeP,showerror)227 term_chk(tty, msgsokP, atimeP, showerror)
228 char *tty;
229 int *msgsokP, showerror;
230 time_t *atimeP;
231 {
232 struct stat s;
233 char path[PATH_MAX];
234
235 (void)sprintf(path, "/dev/%s", tty);
236 if (stat(path, &s) < 0) {
237 if (showerror)
238 (void)fprintf(stderr,
239 "write: %s: %s\n", path, strerror(errno));
240 return(1);
241 }
242 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */
243 *atimeP = s.st_atime;
244 return(0);
245 }
246
247 /*
248 * do_write - actually make the connection
249 */
do_write(tty,mytty,myuid)250 do_write(tty, mytty, myuid)
251 char *tty, *mytty;
252 uid_t myuid;
253 {
254 register char *login, *nows;
255 register struct passwd *pwd;
256 time_t now, time();
257 char *getlogin(), path[PATH_MAX], host[MAXHOSTNAMELEN], line[512];
258 void done();
259
260 /* Determine our login name before the we reopen() stdout */
261 if ((login = getlogin()) == NULL)
262 if (pwd = getpwuid(myuid))
263 login = pwd->pw_name;
264 else
265 login = "???";
266
267 (void)sprintf(path, "/dev/%s", tty);
268 if ((freopen(path, "w", stdout)) == NULL) {
269 (void)fprintf(stderr, "write: %s: %s\n", path, strerror(errno));
270 exit(1);
271 }
272
273 (void)signal(SIGINT, done);
274 (void)signal(SIGHUP, done);
275
276 /* print greeting */
277 if (gethostname(host, sizeof(host)) < 0)
278 (void)strcpy(host, "???");
279 now = time((time_t *)NULL);
280 nows = ctime(&now);
281 nows[16] = '\0';
282 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
283 login, host, mytty, nows + 11);
284
285 while (fgets(line, sizeof(line), stdin) != NULL)
286 wr_fputs(line);
287 }
288
289 /*
290 * done - cleanup and exit
291 */
292 void
done()293 done()
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 */
wr_fputs(s)303 wr_fputs(s)
304 register char *s;
305 {
306 register char c;
307
308 #define PUTC(c) if (putchar(c) == EOF) goto err;
309
310 for (; *s != '\0'; ++s) {
311 c = toascii(*s);
312 if (c == '\n') {
313 PUTC('\r');
314 PUTC('\n');
315 } else if (!isprint(c) && !isspace(c) && c != '\007') {
316 PUTC('^');
317 PUTC(c^0x40); /* DEL to ?, others to alpha */
318 } else
319 PUTC(c);
320 }
321 return;
322
323 err: (void)fprintf(stderr, "write: %s\n", strerror(errno));
324 exit(1);
325 #undef PUTC
326 }
327