1 /* $NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $ */
2
3 /*
4 * Copyright (c) 1989, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/cdefs.h>
36 #ifndef lint
37 __COPYRIGHT("@(#) Copyright (c) 1989, 1993\
38 The Regents of the University of California. All rights reserved.");
39 #endif /* not lint */
40
41 #ifndef lint
42 #if 0
43 static char sccsid[] = "@(#)write.c 8.2 (Berkeley) 4/27/95";
44 #else
45 __RCSID("$NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $");
46 #endif
47 #endif /* not lint */
48
49 #include <sys/types.h>
50 #include <sys/param.h>
51 #include <sys/stat.h>
52 #include <ctype.h>
53 #include <stdio.h>
54 #include <stdlib.h>
55 #include <string.h>
56 #include <signal.h>
57 #include <time.h>
58 #include <fcntl.h>
59 #include <paths.h>
60 #include <pwd.h>
61 #include <unistd.h>
62 #include <err.h>
63 #include <errno.h>
64
65 #include "utmpentry.h"
66 #include "term_chk.h"
67
68 __dead static void done(int);
69 static void do_write(int, const char *, const uid_t);
70 static void wr_fputs(char *);
71 static int search_utmp(char *, char *, uid_t, gid_t);
72 static int utmp_chk(const char *, const char *);
73
74 int
main(int argc,char ** argv)75 main(int argc, char **argv)
76 {
77 time_t atime;
78 uid_t myuid, uid;
79 int msgsok, ttyfd;
80 char *mytty;
81 gid_t saved_egid = getegid();
82
83 if (setegid(getgid()) == -1)
84 err(1, "setegid");
85 myuid = getuid();
86 ttyfd = -1;
87
88 mytty = check_sender(&atime, myuid, saved_egid);
89
90 /* check args */
91 switch (argc) {
92 case 2:
93 ttyfd = search_utmp(argv[1], mytty, myuid, saved_egid);
94 break;
95 case 3:
96 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
97 argv[2] += strlen(_PATH_DEV);
98 if (uid_from_user(argv[1], &uid) == -1)
99 errx(1, "%s: unknown user", argv[1]);
100 if (utmp_chk(argv[1], argv[2]))
101 errx(1, "%s is not logged in on %s",
102 argv[1], argv[2]);
103 ttyfd = term_chk(uid, argv[2], &msgsok, &atime, 0, saved_egid);
104 if (ttyfd == -1)
105 err(1, "%s%s", _PATH_DEV, argv[2]);
106 if (myuid && !msgsok)
107 errx(1, "%s has messages disabled on %s",
108 argv[1], argv[2]);
109 break;
110 default:
111 (void)fprintf(stderr, "usage: write user [tty]\n");
112 exit(1);
113 }
114 if (setgid(getgid()) == -1)
115 err(1, "setgid");
116 do_write(ttyfd, mytty, myuid);
117 done(0);
118 /* NOTREACHED */
119 #ifdef __GNUC__
120 return (0);
121 #endif
122 }
123
124 /*
125 * utmp_chk - checks that the given user is actually logged in on
126 * the given tty
127 */
128 static int
utmp_chk(const char * user,const char * tty)129 utmp_chk(const char *user, const char *tty)
130 {
131 struct utmpentry *ep;
132
133 (void)getutentries(NULL, &ep);
134
135 for (; ep; ep = ep->next)
136 if (strcmp(user, ep->name) == 0 && strcmp(tty, ep->line) == 0)
137 return(0);
138 return(1);
139 }
140
141 /*
142 * search_utmp - search utmp for the "best" terminal to write to
143 *
144 * Ignores terminals with messages disabled, and of the rest, returns
145 * the one with the most recent access time. Returns as value the number
146 * of the user's terminals with messages enabled, or -1 if the user is
147 * not logged in at all.
148 *
149 * Special case for writing to yourself - ignore the terminal you're
150 * writing from, unless that's the only terminal with messages enabled.
151 */
152 static int
search_utmp(char * user,char * mytty,uid_t myuid,gid_t saved_egid)153 search_utmp(char *user, char *mytty, uid_t myuid, gid_t saved_egid)
154 {
155 char tty[MAXPATHLEN];
156 time_t bestatime, atime;
157 int nloggedttys, nttys, msgsok, user_is_me;
158 struct utmpentry *ep;
159 int fd, nfd;
160 uid_t uid;
161
162 if (uid_from_user(user, &uid) == -1)
163 errx(1, "%s: unknown user", user);
164
165 (void)getutentries(NULL, &ep);
166
167 nloggedttys = nttys = 0;
168 bestatime = 0;
169 user_is_me = 0;
170 fd = -1;
171 for (; ep; ep = ep->next)
172 if (strcmp(user, ep->name) == 0) {
173 ++nloggedttys;
174 nfd = term_chk(uid, ep->line, &msgsok, &atime, 0,
175 saved_egid);
176 if (nfd == -1)
177 continue; /* bad term? skip */
178 if (myuid && !msgsok) {
179 close(nfd);
180 continue; /* skip ttys with msgs off */
181 }
182 if (strcmp(ep->line, mytty) == 0) {
183 user_is_me = 1;
184 if (fd == -1)
185 fd = nfd;
186 else
187 close(nfd);
188 continue; /* don't write to yourself */
189 }
190 ++nttys;
191 if (atime > bestatime) {
192 bestatime = atime;
193 (void)strlcpy(tty, ep->line, sizeof(tty));
194 close(fd);
195 fd = nfd;
196 } else
197 close(nfd);
198 }
199
200 if (nloggedttys == 0)
201 errx(1, "%s is not logged in", user);
202 if (nttys == 0) {
203 if (user_is_me) /* ok, so write to yourself! */
204 return fd;
205 errx(1, "%s has messages disabled", user);
206 } else if (nttys > 1)
207 warnx("%s is logged in more than once; writing to %s",
208 user, tty);
209 return fd;
210 }
211
212 /*
213 * do_write - actually make the connection
214 */
215 static void
do_write(int ttyfd,const char * mytty,const uid_t myuid)216 do_write(int ttyfd, const char *mytty, const uid_t myuid)
217 {
218 const char *login;
219 char *nows;
220 struct passwd *pwd;
221 time_t now;
222 char host[MAXHOSTNAMELEN + 1], line[512];
223
224 /* Determine our login name before we re-open stdout */
225 if ((login = getlogin()) == NULL) {
226 if ((pwd = getpwuid(myuid)) != NULL)
227 login = pwd->pw_name;
228 else login = "???";
229 }
230
231 if (dup2(ttyfd, STDOUT_FILENO) == -1)
232 err(1, "dup2");
233
234 (void)signal(SIGINT, done);
235 (void)signal(SIGHUP, done);
236 (void)close(ttyfd);
237
238 /* print greeting */
239 if (gethostname(host, sizeof(host)) < 0)
240 (void)strlcpy(host, "???", sizeof(host));
241 else
242 host[sizeof(host) - 1] = '\0';
243 now = time(NULL);
244 nows = ctime(&now);
245 nows[16] = '\0';
246 (void)printf("\r\n\a\a\aMessage from %s@%s on %s at %s ...\r\n",
247 login, host, mytty, nows + 11);
248
249 while (fgets(line, sizeof(line), stdin) != NULL)
250 wr_fputs(line);
251 }
252
253 /*
254 * done - cleanup and exit
255 */
256 static void
done(int signo)257 done(int signo)
258 {
259
260 (void)write(STDOUT_FILENO, "EOF\r\n", sizeof("EOF\r\n") - 1);
261 if (signo == 0)
262 exit(0);
263 else
264 _exit(0);
265 }
266
267 /*
268 * wr_fputs - like fputs(), but makes control characters visible and
269 * turns \n into \r\n
270 */
271 static void
wr_fputs(char * s)272 wr_fputs(char *s)
273 {
274 unsigned char c;
275
276 #define PUTC(c) if (putchar(c) == EOF) goto err;
277
278 for (; *s != '\0'; ++s) {
279 c = toascii(*s);
280 if (c == '\n') {
281 PUTC('\r');
282 } else if (!isprint(c) && !isspace(c) && c != '\a') {
283 PUTC('^');
284 c ^= 0x40; /* DEL to ?, others to alpha */
285 }
286 PUTC(c);
287 }
288 return;
289
290 err: err(1, NULL);
291 #undef PUTC
292 }
293