wall.tproj/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
  34 #include <sys/cdefs.h>
  35
  36
  37 #ifndef lint
  38 static const char sccsid[] = "@(#)ttymsg.c      8.2 (Berkeley) 11/16/93";
  39 #endif
  40
  41 #include <sys/types.h>
  42 #include <sys/uio.h>
  43 #include <dirent.h>
  44 #include <errno.h>
  45 #include <fcntl.h>
  46 #include <paths.h>
  47 #include <signal.h>
  48 #include <stdio.h>
  49 #include <string.h>
  50 #include <stdlib.h>
  51 #include <unistd.h>
  52
  53 #include "ttymsg.h"
  54
  55 /*
  56  * Display the contents of a uio structure on a terminal.  Used by wall(1),
  57  * syslogd(8), and talkd(8).  Forks and finishes in child if write would block,
  58  * waiting up to tmout seconds.  Returns pointer to error string on unexpected
  59  * error; string is not newline-terminated.  Various "normal" errors are
  60  * ignored (exclusive-use, lack of permission, etc.).
  61  */
  62 const char *
  63 ttymsg(struct iovec *iov, int iovcnt, const char *line, int tmout)
  64 {
  65         struct iovec localiov[7];
  66         ssize_t left, wret;
  67         int cnt, fd;
  68         static char device[MAXNAMLEN] = _PATH_DEV;
  69         static char errbuf[1024];
  70         int forked;
  71
  72         forked = 0;
  73         if (iovcnt > (int)(sizeof(localiov) / sizeof(localiov[0])))
  74                 return ("too many iov's (change code in wall/ttymsg.c)");
  75
  76         strlcpy(device + sizeof(_PATH_DEV) - 1, line, sizeof(device));
  77         if (strchr(device + sizeof(_PATH_DEV) - 1, '/')) {
  78                 /* A slash is an attempt to break security... */
  79                 (void) snprintf(errbuf, sizeof(errbuf),
  80                     "Too many '/' in \"%s\"", device);
  81                 return (errbuf);
  82         }
  83
  84         /*
  85          * open will fail on slip lines or exclusive-use lines
  86          * if not running as root; not an error.
  87          */
  88         if ((fd = open(device, O_WRONLY|O_NONBLOCK, 0)) < 0) {
  89                 if (errno == EBUSY || errno == EACCES)
  90                         return (NULL);
  91                 (void) snprintf(errbuf, sizeof(errbuf), "%s: %s", device,
  92                     strerror(errno));
  93                 return (errbuf);
  94         }
  95
  96         for (cnt = 0, left = 0; cnt < iovcnt; ++cnt)
  97                 left += iov[cnt].iov_len;
  98
  99         for (;;) {
 100                 wret = writev(fd, iov, iovcnt);
 101                 if (wret >= left)
 102                         break;
 103                 if (wret >= 0) {
 104                         left -= wret;
 105                         if (iov != localiov) {
 106                                 bcopy(iov, localiov,
 107                                     iovcnt * sizeof(struct iovec));
 108                                 iov = localiov;
 109                         }
 110                         for (cnt = 0; (size_t)wret >= iov->iov_len; ++cnt) {
 111                                 wret -= iov->iov_len;
 112                                 ++iov;
 113                                 --iovcnt;
 114                         }
 115                         if (wret) {
 116                                 iov->iov_base = (char *)iov->iov_base + wret;
 117                                 iov->iov_len -= wret;
 118                         }
 119                         continue;
 120                 }
 121                 if (errno == EWOULDBLOCK) {
 122                         int cpid;
 123
 124                         if (forked) {
 125                                 (void) close(fd);
 126                                 _exit(1);
 127                         }
 128                         cpid = fork();
 129                         if (cpid < 0) {
 130                                 (void) snprintf(errbuf, sizeof(errbuf),
 131                                     "fork: %s", strerror(errno));
 132                                 (void) close(fd);
 133                                 return (errbuf);
 134                         }
 135                         if (cpid) {     /* parent */
 136                                 (void) close(fd);
 137                                 return (NULL);
 138                         }
 139                         forked++;
 140                         /* wait at most tmout seconds */
 141                         (void) signal(SIGALRM, SIG_DFL);
 142                         (void) signal(SIGTERM, SIG_DFL); /* XXX */
 143                         (void) sigsetmask(0);
 144                         (void) alarm((u_int)tmout);
 145                         (void) fcntl(fd, F_SETFL, 0);   /* clear O_NONBLOCK */
 146                         continue;
 147                 }
 148                 /*
 149                  * We get ENODEV on a slip line if we're running as root,
 150                  * and EIO if the line just went away.
 151                  */
 152                 if (errno == ENODEV || errno == EIO)
 153                         break;
 154                 (void) close(fd);
 155                 if (forked)
 156                         _exit(1);
 157                 (void) snprintf(errbuf, sizeof(errbuf),
 158                     "%s: %s", device, strerror(errno));
 159                 return (errbuf);
 160         }
 161
 162         (void) close(fd);
 163         if (forked)
 164                 _exit(0);
 165         return (NULL);
 166 }