1 /* $OpenBSD: ttymsg.c,v 1.21 2023/05/02 09:51:22 tb Exp $ */
2 /* $NetBSD: ttymsg.c,v 1.3 1994/11/17 07:17:55 jtc Exp $ */
3
4 /*
5 * Copyright (c) 1989, 1993
6 * The Regents of the University of California. All rights reserved.
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
33 #include <sys/types.h>
34 #include <sys/stat.h>
35 #include <sys/uio.h>
36 #include <signal.h>
37 #include <fcntl.h>
38 #include <dirent.h>
39 #include <errno.h>
40 #include <paths.h>
41 #include <unistd.h>
42 #include <stdio.h>
43 #include <string.h>
44 #include <stdlib.h>
45 #include <err.h>
46
47 char *ttymsg(struct iovec *, int, char *, int);
48
49 /*
50 * Display the contents of a uio structure on a terminal. Used by wall(1)
51 * and talkd(8). Forks and finishes in child if write would block,
52 * waiting up to tmout seconds. Returns pointer to error string on unexpected
53 * error; string is not newline-terminated. Various "normal" errors are
54 * ignored (exclusive-use, lack of permission, etc.).
55 */
56 char *
ttymsg(struct iovec * iov,int iovcnt,char * line,int tmout)57 ttymsg(struct iovec *iov, int iovcnt, char *line, int tmout)
58 {
59 static char device[MAXNAMLEN] = _PATH_DEV;
60 static char errbuf[1024];
61 int cnt, fd, left, wret;
62 struct iovec localiov[6];
63 int forked = 0;
64 struct stat st;
65 sigset_t mask;
66
67 if (iovcnt > sizeof(localiov) / sizeof(localiov[0]))
68 return ("too many iov's (change code in wall/ttymsg.c)");
69
70 /*
71 * Ignore lines that start with "ftp" or "uucp".
72 */
73 if ((strncmp(line, "ftp", 3) == 0) ||
74 (strncmp(line, "uucp", 4) == 0))
75 return (NULL);
76
77 (void) strlcpy(device + sizeof(_PATH_DEV) - 1, line,
78 sizeof(device) - (sizeof(_PATH_DEV) - 1));
79 if (strchr(device + sizeof(_PATH_DEV) - 1, '/')) {
80 /* A slash is an attempt to break security... */
81 (void) snprintf(errbuf, sizeof(errbuf), "'/' in \"%s\"",
82 device);
83 return (errbuf);
84 }
85
86 /*
87 * open will fail on slip lines or exclusive-use lines
88 * if not running as root; not an error.
89 */
90 if ((fd = open(device, O_WRONLY|O_NONBLOCK)) == -1) {
91 if (errno == EBUSY || errno == EACCES)
92 return (NULL);
93 (void) snprintf(errbuf, sizeof(errbuf),
94 "%s: %s", device, strerror(errno));
95 return (errbuf);
96 }
97
98 if (getuid()) {
99 if (fstat(fd, &st) == -1 ||
100 (st.st_mode & S_IWGRP) == 0) {
101 close(fd);
102 return (NULL);
103 }
104 }
105
106 for (cnt = left = 0; cnt < iovcnt; ++cnt)
107 left += iov[cnt].iov_len;
108
109 for (;;) {
110 wret = writev(fd, iov, iovcnt);
111 if (wret >= left)
112 break;
113 if (wret >= 0) {
114 left -= wret;
115 if (iov != localiov) {
116 bcopy(iov, localiov,
117 iovcnt * sizeof(struct iovec));
118 iov = localiov;
119 }
120 for (cnt = 0; wret >= iov->iov_len; ++cnt) {
121 wret -= iov->iov_len;
122 ++iov;
123 --iovcnt;
124 }
125 if (wret) {
126 char *base = iov->iov_base;
127
128 iov->iov_base = base + wret;
129 iov->iov_len -= wret;
130 }
131 continue;
132 }
133 if (errno == EWOULDBLOCK) {
134 int off = 0;
135 pid_t cpid;
136
137 if (forked) {
138 (void) close(fd);
139 _exit(1);
140 }
141 cpid = fork();
142 if (cpid == -1) {
143 (void) snprintf(errbuf, sizeof(errbuf),
144 "fork: %s", strerror(errno));
145 (void) close(fd);
146 return (errbuf);
147 }
148 if (cpid) { /* parent */
149 (void) close(fd);
150 return (NULL);
151 }
152
153 if (pledge("stdio", NULL) == -1)
154 err(1, "pledge");
155
156 forked++;
157 /* wait at most tmout seconds */
158 (void) signal(SIGALRM, SIG_DFL);
159 (void) signal(SIGTERM, SIG_DFL); /* XXX */
160 (void) sigemptyset(&mask);
161 (void) sigprocmask(SIG_SETMASK, &mask, NULL);
162 (void) alarm((u_int)tmout);
163 (void) fcntl(fd, O_NONBLOCK, &off);
164 continue;
165 }
166 /*
167 * We get ENODEV on a slip line if we're running as root,
168 * and EIO if the line just went away.
169 */
170 if (errno == ENODEV || errno == EIO)
171 break;
172 (void) close(fd);
173 if (forked)
174 _exit(1);
175 (void) snprintf(errbuf, sizeof(errbuf),
176 "%s: %s", device, strerror(errno));
177 return (errbuf);
178 }
179
180 (void) close(fd);
181 if (forked)
182 _exit(0);
183 return (NULL);
184 }
185