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         char *p;
  68         int forked;
  69
  70         forked = 0;
  71         if (iovcnt > (int)(sizeof(localiov) / sizeof(localiov[0])))
  72                 return ("too many iov's (change code in wall/ttymsg.c)");
  73
  74         p = device + sizeof(_PATH_DEV) - 1;
  75         strlcpy(p, line, sizeof(device));
  76         if (!strncmp(p, "pts/", 4))
  77                 p += 4;
  78         if (strchr(p, '/') != NULL) {
  79                 /* A slash is an attempt to break security... */
  80                 (void) snprintf(errbuf, sizeof(errbuf),
  81                     "Too many '/' in \"%s\"", device);
  82                 return (errbuf);
  83         }
  84
  85         /*
  86          * open will fail on slip lines or exclusive-use lines
  87          * if not running as root; not an error.
  88          */
  89         if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
  90                 if (errno == EBUSY || errno == EACCES)
  91                         return (NULL);
  92                 (void) snprintf(errbuf, sizeof(errbuf), "%s: %s", device,
  93                     strerror(errno));
  94                 return (errbuf);
  95         }
  96
  97         for (cnt = 0, left = 0; cnt < iovcnt; ++cnt)
  98                 left += iov[cnt].iov_len;
  99
 100         for (;;) {
 101                 wret = writev(fd, iov, iovcnt);
 102                 if (wret >= left)
 103                         break;
 104                 if (wret >= 0) {
 105                         left -= wret;
 106                         if (iov != localiov) {
 107                                 bcopy(iov, localiov,
 108                                     iovcnt * sizeof(struct iovec));
 109                                 iov = localiov;
 110                         }
 111                         for (cnt = 0; (size_t)wret >= iov->iov_len; ++cnt) {
 112                                 wret -= iov->iov_len;
 113                                 ++iov;
 114                                 --iovcnt;
 115                         }
 116                         if (wret) {
 117                                 iov->iov_base += wret;
 118                                 iov->iov_len -= wret;
 119                         }
 120                         continue;
 121                 }
 122                 if (errno == EWOULDBLOCK) {
 123                         int cpid;
 124
 125                         if (forked) {
 126                                 (void) close(fd);
 127                                 _exit(1);
 128                         }
 129                         cpid = fork();
 130                         if (cpid < 0) {
 131                                 (void) snprintf(errbuf, sizeof(errbuf),
 132                                     "fork: %s", strerror(errno));
 133                                 (void) close(fd);
 134                                 return (errbuf);
 135                         }
 136                         if (cpid) {     /* parent */
 137                                 (void) close(fd);
 138                                 return (NULL);
 139                         }
 140                         forked++;
 141                         /* wait at most tmout seconds */
 142                         (void) signal(SIGALRM, SIG_DFL);
 143                         (void) signal(SIGTERM, SIG_DFL); /* XXX */
 144                         (void) sigsetmask(0);
 145                         (void) alarm((u_int)tmout);
 146                         (void) fcntl(fd, F_SETFL, 0);   /* clear O_NONBLOCK */
 147                         continue;
 148                 }
 149                 /*
 150                  * We get ENODEV on a slip line if we're running as root,
 151                  * and EIO if the line just went away.
 152                  */
 153                 if (errno == ENODEV || errno == EIO)
 154                         break;
 155                 (void) close(fd);
 156                 if (forked)
 157                         _exit(1);
 158                 (void) snprintf(errbuf, sizeof(errbuf),
 159                     "%s: %s", device, strerror(errno));
 160                 return (errbuf);
 161         }
 162
 163         (void) close(fd);
 164         if (forked)
 165                 _exit(0);
 166         return (NULL);
 167 }