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 * 4. 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
33 #ifndef lint
34 static const char copyright[] =
35 "@(#) Copyright (c) 1989, 1993\n\
36 The Regents of the University of California. All rights reserved.\n";
37 #endif
38
39 #if 0
40 #ifndef lint
41 static char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93";
42 #endif
43 #endif
44
45 #include <sys/cdefs.h>
46 __FBSDID("$FreeBSD$");
47
48 #include <sys/param.h>
49 #include <sys/signal.h>
50 #include <sys/stat.h>
51 #include <sys/file.h>
52 #include <sys/time.h>
53 #include <ctype.h>
54 #include <err.h>
55 #include <locale.h>
56 #include <paths.h>
57 #include <pwd.h>
58 #include <stdio.h>
59 #include <stdlib.h>
60 #include <string.h>
61 #include <unistd.h>
62 #include <utmpx.h>
63 #include <wchar.h>
64 #include <wctype.h>
65
66 void done(int);
67 void do_write(char *, char *, uid_t);
68 static void usage(void);
69 int term_chk(char *, int *, time_t *, int);
70 void wr_fputs(wchar_t *s);
71 void search_utmp(char *, char *, char *, uid_t);
72 int utmp_chk(char *, char *);
73
74 int
main(int argc,char ** argv)75 main(int argc, char **argv)
76 {
77 time_t atime;
78 uid_t myuid;
79 int msgsok, myttyfd;
80 char tty[MAXPATHLEN], *mytty;
81
82 (void)setlocale(LC_CTYPE, "");
83
84 while (getopt(argc, argv, "") != -1)
85 usage();
86 argc -= optind;
87 argv += optind;
88
89 /* check that sender has write enabled */
90 if (isatty(fileno(stdin)))
91 myttyfd = fileno(stdin);
92 else if (isatty(fileno(stdout)))
93 myttyfd = fileno(stdout);
94 else if (isatty(fileno(stderr)))
95 myttyfd = fileno(stderr);
96 else
97 errx(1, "can't find your tty");
98 if (!(mytty = ttyname(myttyfd)))
99 errx(1, "can't find your tty's name");
100 if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV)))
101 mytty += strlen(_PATH_DEV);
102 if (term_chk(mytty, &msgsok, &atime, 1))
103 exit(1);
104 if (!msgsok)
105 errx(1, "you have write permission turned off");
106
107 myuid = getuid();
108
109 /* check args */
110 switch (argc) {
111 case 1:
112 search_utmp(argv[0], tty, mytty, myuid);
113 do_write(tty, mytty, myuid);
114 break;
115 case 2:
116 if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV)))
117 argv[1] += strlen(_PATH_DEV);
118 if (utmp_chk(argv[0], argv[1]))
119 errx(1, "%s is not logged in on %s", argv[0], argv[1]);
120 if (term_chk(argv[1], &msgsok, &atime, 1))
121 exit(1);
122 if (myuid && !msgsok)
123 errx(1, "%s has messages disabled on %s", argv[0], argv[1]);
124 do_write(argv[1], mytty, myuid);
125 break;
126 default:
127 usage();
128 }
129 done(0);
130 return (0);
131 }
132
133 static void
usage(void)134 usage(void)
135 {
136 (void)fprintf(stderr, "usage: write user [tty]\n");
137 exit(1);
138 }
139
140 /*
141 * utmp_chk - checks that the given user is actually logged in on
142 * the given tty
143 */
144 int
utmp_chk(char * user,char * tty)145 utmp_chk(char *user, char *tty)
146 {
147 struct utmpx lu, *u;
148
149 strncpy(lu.ut_line, tty, sizeof lu.ut_line);
150 setutxent();
151 while ((u = getutxline(&lu)) != NULL)
152 if (u->ut_type == USER_PROCESS &&
153 strcmp(user, u->ut_user) == 0) {
154 endutxent();
155 return(0);
156 }
157 endutxent();
158 return(1);
159 }
160
161 /*
162 * search_utmp - search utmp for the "best" terminal to write to
163 *
164 * Ignores terminals with messages disabled, and of the rest, returns
165 * the one with the most recent access time. Returns as value the number
166 * of the user's terminals with messages enabled, or -1 if the user is
167 * not logged in at all.
168 *
169 * Special case for writing to yourself - ignore the terminal you're
170 * writing from, unless that's the only terminal with messages enabled.
171 */
172 void
search_utmp(char * user,char * tty,char * mytty,uid_t myuid)173 search_utmp(char *user, char *tty, char *mytty, uid_t myuid)
174 {
175 struct utmpx *u;
176 time_t bestatime, atime;
177 int nloggedttys, nttys, msgsok, user_is_me;
178
179 nloggedttys = nttys = 0;
180 bestatime = 0;
181 user_is_me = 0;
182
183 setutxent();
184 while ((u = getutxent()) != NULL)
185 if (u->ut_type == USER_PROCESS &&
186 strcmp(user, u->ut_user) == 0) {
187 ++nloggedttys;
188 if (term_chk(u->ut_line, &msgsok, &atime, 0))
189 continue; /* bad term? skip */
190 if (myuid && !msgsok)
191 continue; /* skip ttys with msgs off */
192 if (strcmp(u->ut_line, 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)strlcpy(tty, u->ut_line, MAXPATHLEN);
200 }
201 }
202 endutxent();
203
204 if (nloggedttys == 0)
205 errx(1, "%s is not logged in", user);
206 if (nttys == 0) {
207 if (user_is_me) { /* ok, so write to yourself! */
208 (void)strlcpy(tty, mytty, MAXPATHLEN);
209 return;
210 }
211 errx(1, "%s has messages disabled", user);
212 } else if (nttys > 1) {
213 warnx("%s is logged in more than once; writing to %s", user, tty);
214 }
215 }
216
217 /*
218 * term_chk - check that a terminal exists, and get the message bit
219 * and the access time
220 */
221 int
term_chk(char * tty,int * msgsokP,time_t * atimeP,int showerror)222 term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
223 {
224 struct stat s;
225 char path[MAXPATHLEN];
226
227 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
228 if (stat(path, &s) < 0) {
229 if (showerror)
230 warn("%s", path);
231 return(1);
232 }
233 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */
234 *atimeP = s.st_atime;
235 return(0);
236 }
237
238 /*
239 * do_write - actually make the connection
240 */
241 void
do_write(char * tty,char * mytty,uid_t myuid)242 do_write(char *tty, char *mytty, uid_t myuid)
243 {
244 const char *login;
245 char *nows;
246 struct passwd *pwd;
247 time_t now;
248 char path[MAXPATHLEN], host[MAXHOSTNAMELEN];
249 wchar_t line[512];
250
251 /* Determine our login name before we reopen() stdout */
252 if ((login = getlogin()) == NULL) {
253 if ((pwd = getpwuid(myuid)))
254 login = pwd->pw_name;
255 else
256 login = "???";
257 }
258
259 (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
260 if ((freopen(path, "w", stdout)) == NULL)
261 err(1, "%s", path);
262
263 (void)signal(SIGINT, done);
264 (void)signal(SIGHUP, done);
265
266 /* print greeting */
267 if (gethostname(host, sizeof(host)) < 0)
268 (void)strcpy(host, "???");
269 now = time((time_t *)NULL);
270 nows = ctime(&now);
271 nows[16] = '\0';
272 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
273 login, host, mytty, nows + 11);
274
275 while (fgetws(line, sizeof(line)/sizeof(wchar_t), stdin) != NULL)
276 wr_fputs(line);
277 }
278
279 /*
280 * done - cleanup and exit
281 */
282 void
done(int n __unused)283 done(int n __unused)
284 {
285 (void)printf("EOF\r\n");
286 exit(0);
287 }
288
289 /*
290 * wr_fputs - like fputs(), but makes control characters visible and
291 * turns \n into \r\n
292 */
293 void
wr_fputs(wchar_t * s)294 wr_fputs(wchar_t *s)
295 {
296
297 #define PUTC(c) if (putwchar(c) == WEOF) err(1, NULL);
298
299 for (; *s != L'\0'; ++s) {
300 if (*s == L'\n') {
301 PUTC(L'\r');
302 PUTC(L'\n');
303 } else if (iswprint(*s) || iswspace(*s)) {
304 PUTC(*s);
305 } else {
306 wprintf(L"<0x%X>", *s);
307 }
308 }
309 return;
310 #undef PUTC
311 }
312