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 * 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