usr.bin/wall/ttymsg.c

   1 /*
   2  * Copyright (c) 1989, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)ttymsg.c 8.2 (Berkeley) 11/16/93
  34  * $FreeBSD: src/usr.bin/wall/ttymsg.c,v 1.4.2.3 2001/10/18 08:08:17 des Exp $
  35  * $DragonFly: src/usr.bin/wall/ttymsg.c,v 1.3 2005/08/08 16:39:17 joerg Exp $
  36  */
  37
  38 #include <sys/types.h>
  39 #include <sys/uio.h>
  40 #include <errno.h>
  41 #include <fcntl.h>
  42 #include <limits.h>
  43 #include <paths.h>
  44 #include <signal.h>
  45 #include <stdio.h>
  46 #include <string.h>
  47 #include <stdlib.h>
  48 #include <unistd.h>
  49
  50 #include "ttymsg.h"
  51
  52 /*
  53  * Display the contents of a uio structure on a terminal.  Used by wall(1),
  54  * syslogd(8), and talkd(8).  Forks and finishes in child if write would block,
  55  * waiting up to tmout seconds.  Returns pointer to error string on unexpected
  56  * error; string is not newline-terminated.  Various "normal" errors are
  57  * ignored (exclusive-use, lack of permission, etc.).
  58  */
  59 const char *
  60 ttymsg(struct iovec *iov, int iovcnt, const char *line, int tmout)
  61 {
  62         struct iovec localiov[7];
  63         ssize_t left, wret;
  64         int cnt, fd;
  65         static char device[PATH_MAX] = _PATH_DEV;
  66         static char errbuf[1024];
  67         int forked;
  68
  69         forked = 0;
  70         if (iovcnt > (int)(sizeof(localiov) / sizeof(localiov[0])))
  71                 return ("too many iov's (change code in wall/ttymsg.c)");
  72
  73         strlcpy(device + sizeof(_PATH_DEV) - 1, line, sizeof(device));
  74         if (strchr(device + sizeof(_PATH_DEV) - 1, '/')) {
  75                 /* A slash is an attempt to break security... */
  76                 (void) snprintf(errbuf, sizeof(errbuf),
  77                     "Too many '/' in \"%s\"", device);
  78                 return (errbuf);
  79         }
  80
  81         /*
  82          * open will fail on slip lines or exclusive-use lines
  83          * if not running as root; not an error.
  84          */
  85         if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
  86                 if (errno == EBUSY || errno == EACCES)
  87                         return (NULL);
  88                 (void) snprintf(errbuf, sizeof(errbuf), "%s: %s", device,
  89                     strerror(errno));
  90                 return (errbuf);
  91         }
  92
  93         for (cnt = 0, left = 0; cnt < iovcnt; ++cnt)
  94                 left += iov[cnt].iov_len;
  95
  96         for (;;) {
  97                 wret = writev(fd, iov, iovcnt);
  98                 if (wret >= left)
  99                         break;
 100                 if (wret >= 0) {
 101                         left -= wret;
 102                         if (iov != localiov) {
 103                                 bcopy(iov, localiov,
 104                                     iovcnt * sizeof(struct iovec));
 105                                 iov = localiov;
 106                         }
 107                         for (cnt = 0; (size_t)wret >= iov->iov_len; ++cnt) {
 108                                 wret -= iov->iov_len;
 109                                 ++iov;
 110                                 --iovcnt;
 111                         }
 112                         if (wret) {
 113                                 iov->iov_base += wret;
 114                                 iov->iov_len -= wret;
 115                         }
 116                         continue;
 117                 }
 118                 if (errno == EWOULDBLOCK) {
 119                         int cpid;
 120
 121                         if (forked) {
 122                                 (void) close(fd);
 123                                 _exit(1);
 124                         }
 125                         cpid = fork();
 126                         if (cpid < 0) {
 127                                 (void) snprintf(errbuf, sizeof(errbuf),
 128                                     "fork: %s", strerror(errno));
 129                                 (void) close(fd);
 130                                 return (errbuf);
 131                         }
 132                         if (cpid) {     /* parent */
 133                                 (void) close(fd);
 134                                 return (NULL);
 135                         }
 136                         forked++;
 137                         /* wait at most tmout seconds */
 138                         (void) signal(SIGALRM, SIG_DFL);
 139                         (void) signal(SIGTERM, SIG_DFL); /* XXX */
 140                         (void) sigsetmask(0);
 141                         (void) alarm((u_int)tmout);
 142                         (void) fcntl(fd, F_SETFL, 0);   /* clear O_NONBLOCK */
 143                         continue;
 144                 }
 145                 /*
 146                  * We get ENODEV on a slip line if we're running as root,
 147                  * and EIO if the line just went away.
 148                  */
 149                 if (errno == ENODEV || errno == EIO)
 150                         break;
 151                 (void) close(fd);
 152                 if (forked)
 153                         _exit(1);
 154                 (void) snprintf(errbuf, sizeof(errbuf),
 155                     "%s: %s", device, strerror(errno));
 156                 return (errbuf);
 157         }
 158
 159         (void) close(fd);
 160         if (forked)
 161                 _exit(0);
 162         return (NULL);
 163 }