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 * %sccs.include.redist.c%
9 */
10
11 #ifndef lint
12 static char copyright[] =
13 "@(#) Copyright (c) 1989, 1993\n\
14 The Regents of the University of California. All rights reserved.\n";
15 #endif /* not lint */
16
17 #ifndef lint
18 static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 04/27/95";
19 #endif /* not lint */
20
21 #include <sys/param.h>
22 #include <sys/signal.h>
23 #include <sys/stat.h>
24 #include <sys/file.h>
25 #include <sys/time.h>
26
27 #include <err.h>
28 #include <utmp.h>
29 #include <ctype.h>
30 #include <pwd.h>
31 #include <stdio.h>
32 #include <string.h>
33
34 extern int errno;
35
main(argc,argv)36 main(argc, argv)
37 int argc;
38 char **argv;
39 {
40 register char *cp;
41 time_t atime;
42 uid_t myuid;
43 int msgsok, myttyfd;
44 char tty[MAXPATHLEN], *mytty, *ttyname();
45 void done();
46
47 /* check that sender has write enabled */
48 if (isatty(fileno(stdin)))
49 myttyfd = fileno(stdin);
50 else if (isatty(fileno(stdout)))
51 myttyfd = fileno(stdout);
52 else if (isatty(fileno(stderr)))
53 myttyfd = fileno(stderr);
54 else
55 errx(1, "can't find your tty");
56 if (!(mytty = ttyname(myttyfd)))
57 errx(1, "can't find your tty's name");
58 if (cp = strrchr(mytty, '/'))
59 mytty = cp + 1;
60 if (term_chk(mytty, &msgsok, &atime, 1))
61 exit(1);
62 if (!msgsok)
63 errx(1, "you have write permission turned off");
64
65 myuid = getuid();
66
67 /* check args */
68 switch (argc) {
69 case 2:
70 search_utmp(argv[1], tty, mytty, myuid);
71 do_write(tty, mytty, myuid);
72 break;
73 case 3:
74 if (!strncmp(argv[2], "/dev/", 5))
75 argv[2] += 5;
76 if (utmp_chk(argv[1], argv[2]))
77 errx(1, "%s is not logged in on %s",
78 argv[1], argv[2]);
79 if (term_chk(argv[2], &msgsok, &atime, 1))
80 exit(1);
81 if (myuid && !msgsok)
82 errx(1, "%s has messages disabled on %s",
83 argv[1], argv[2]);
84 do_write(argv[2], mytty, myuid);
85 break;
86 default:
87 (void)fprintf(stderr, "usage: write user [tty]\n");
88 exit(1);
89 }
90 done();
91 /* NOTREACHED */
92 }
93
94 /*
95 * utmp_chk - checks that the given user is actually logged in on
96 * the given tty
97 */
utmp_chk(user,tty)98 utmp_chk(user, tty)
99 char *user, *tty;
100 {
101 struct utmp u;
102 int ufd;
103
104 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
105 return(0); /* ignore error, shouldn't happen anyway */
106
107 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
108 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
109 strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
110 (void)close(ufd);
111 return(0);
112 }
113
114 (void)close(ufd);
115 return(1);
116 }
117
118 /*
119 * search_utmp - search utmp for the "best" terminal to write to
120 *
121 * Ignores terminals with messages disabled, and of the rest, returns
122 * the one with the most recent access time. Returns as value the number
123 * of the user's terminals with messages enabled, or -1 if the user is
124 * not logged in at all.
125 *
126 * Special case for writing to yourself - ignore the terminal you're
127 * writing from, unless that's the only terminal with messages enabled.
128 */
search_utmp(user,tty,mytty,myuid)129 search_utmp(user, tty, mytty, myuid)
130 char *user, *tty, *mytty;
131 uid_t myuid;
132 {
133 struct utmp u;
134 time_t bestatime, atime;
135 int ufd, nloggedttys, nttys, msgsok, user_is_me;
136 char atty[UT_LINESIZE + 1];
137
138 if ((ufd = open(_PATH_UTMP, O_RDONLY)) < 0)
139 err(1, "%s", _PATH_UTMP);
140
141 nloggedttys = nttys = 0;
142 bestatime = 0;
143 user_is_me = 0;
144 while (read(ufd, (char *) &u, sizeof(u)) == sizeof(u))
145 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
146 ++nloggedttys;
147 (void)strncpy(atty, u.ut_line, UT_LINESIZE);
148 atty[UT_LINESIZE] = '\0';
149 if (term_chk(atty, &msgsok, &atime, 0))
150 continue; /* bad term? skip */
151 if (myuid && !msgsok)
152 continue; /* skip ttys with msgs off */
153 if (strcmp(atty, mytty) == 0) {
154 user_is_me = 1;
155 continue; /* don't write to yourself */
156 }
157 ++nttys;
158 if (atime > bestatime) {
159 bestatime = atime;
160 (void)strcpy(tty, atty);
161 }
162 }
163
164 (void)close(ufd);
165 if (nloggedttys == 0)
166 errx(1, "%s is not logged in", user);
167 if (nttys == 0) {
168 if (user_is_me) { /* ok, so write to yourself! */
169 (void)strcpy(tty, mytty);
170 return;
171 }
172 errx(1, "%s has messages disabled", user);
173 } else if (nttys > 1)
174 warnx("%s is logged in more than once; writing to %s",
175 user, tty);
176 }
177
178 /*
179 * term_chk - check that a terminal exists, and get the message bit
180 * and the access time
181 */
term_chk(tty,msgsokP,atimeP,showerror)182 term_chk(tty, msgsokP, atimeP, showerror)
183 char *tty;
184 int *msgsokP, showerror;
185 time_t *atimeP;
186 {
187 struct stat s;
188 char path[MAXPATHLEN];
189
190 (void)sprintf(path, "/dev/%s", tty);
191 if (stat(path, &s) < 0) {
192 if (showerror)
193 warn("%s", path);
194 return(1);
195 }
196 *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */
197 *atimeP = s.st_atime;
198 return(0);
199 }
200
201 /*
202 * do_write - actually make the connection
203 */
do_write(tty,mytty,myuid)204 do_write(tty, mytty, myuid)
205 char *tty, *mytty;
206 uid_t myuid;
207 {
208 register char *login, *nows;
209 register struct passwd *pwd;
210 time_t now, time();
211 char *getlogin(), path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
212 void done();
213
214 /* Determine our login name before the we reopen() stdout */
215 if ((login = getlogin()) == NULL)
216 if (pwd = getpwuid(myuid))
217 login = pwd->pw_name;
218 else
219 login = "???";
220
221 (void)sprintf(path, "/dev/%s", tty);
222 if ((freopen(path, "w", stdout)) == NULL)
223 err(1, "%s", path);
224
225 (void)signal(SIGINT, done);
226 (void)signal(SIGHUP, done);
227
228 /* print greeting */
229 if (gethostname(host, sizeof(host)) < 0)
230 (void)strcpy(host, "???");
231 now = time((time_t *)NULL);
232 nows = ctime(&now);
233 nows[16] = '\0';
234 (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
235 login, host, mytty, nows + 11);
236
237 while (fgets(line, sizeof(line), stdin) != NULL)
238 wr_fputs(line);
239 }
240
241 /*
242 * done - cleanup and exit
243 */
244 void
done()245 done()
246 {
247 (void)printf("EOF\r\n");
248 exit(0);
249 }
250
251 /*
252 * wr_fputs - like fputs(), but makes control characters visible and
253 * turns \n into \r\n
254 */
wr_fputs(s)255 wr_fputs(s)
256 register char *s;
257 {
258 register char c;
259
260 #define PUTC(c) if (putchar(c) == EOF) goto err;
261
262 for (; *s != '\0'; ++s) {
263 c = toascii(*s);
264 if (c == '\n') {
265 PUTC('\r');
266 PUTC('\n');
267 } else if (!isprint(c) && !isspace(c) && c != '\007') {
268 PUTC('^');
269 PUTC(c^0x40); /* DEL to ?, others to alpha */
270 } else
271 PUTC(c);
272 }
273 return;
274
275 err: err(1, NULL);
276 #undef PUTC
277 }
278