usr.bin/write/write.c

   1 /*
   2  * Copyright (c) 1989, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
   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  * @(#) Copyright (c) 1989, 1993 The Regents of the University of California.  All rights reserved.
  33  * @(#)write.c  8.1 (Berkeley) 6/6/93
  34  * $FreeBSD: src/usr.bin/write/write.c,v 1.12 1999/08/28 01:07:48 peter Exp $
  35  */
  36
  37 #include <sys/param.h>
  38 #include <sys/stat.h>
  39 #include <sys/file.h>
  40
  41 #include <ctype.h>
  42 #include <err.h>
  43 #include <locale.h>
  44 #include <paths.h>
  45 #include <pwd.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include <string.h>
  49 #include <signal.h>
  50 #include <time.h>
  51 #include <unistd.h>
  52 #include "utmpentry.h"
  53
  54 static void     done(int);
  55 static void     do_write(const char *, const char *, uid_t, int *);
  56 static void     usage(void);
  57 static int      term_chk(const char *, int *, time_t *, int);
  58 static void     wr_fputs(unsigned char *s);
  59 static void     search_utmpx(const char *, char *, size_t, const char *, uid_t);
  60 static int      utmpx_chk(const char *, const char *);
  61
  62 int
  63 main(int argc, char **argv)
  64 {
  65         time_t atime;
  66         uid_t myuid;
  67         int msgsok, mymsgok, myttyfd;
  68         char tty[MAXPATHLEN], *mytty;
  69
  70         setlocale(LC_CTYPE, "");
  71
  72         /* check that sender has write enabled */
  73         if (isatty(fileno(stdin)))
  74                 myttyfd = fileno(stdin);
  75         else if (isatty(fileno(stdout)))
  76                 myttyfd = fileno(stdout);
  77         else if (isatty(fileno(stderr)))
  78                 myttyfd = fileno(stderr);
  79         else
  80                 errx(1, "can't find your tty");
  81         if (!(mytty = ttyname(myttyfd)))
  82                 errx(1, "can't find your tty's name");
  83         if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV)))
  84                 mytty += strlen(_PATH_DEV);
  85         if (term_chk(mytty, &mymsgok, &atime, 1))
  86                 exit(1);
  87         if (!mymsgok)
  88                 warnx("you have write permission turned off (man mesg)");
  89
  90         myuid = getuid();
  91
  92         /* check args */
  93         switch (argc) {
  94         case 2:
  95                 search_utmpx(argv[1], tty, sizeof tty, mytty, myuid);
  96                 do_write(tty, mytty, myuid, &mymsgok);
  97                 break;
  98         case 3:
  99                 if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
 100                         argv[2] += strlen(_PATH_DEV);
 101                 if (utmpx_chk(argv[1], argv[2]))
 102                         errx(1, "%s is not logged in on %s", argv[1], argv[2]);
 103                 if (term_chk(argv[2], &msgsok, &atime, 1))
 104                         exit(1);
 105                 if (myuid && !msgsok)
 106                         errx(1, "%s has messages disabled on %s", argv[1], argv[2]);
 107                 do_write(argv[2], mytty, myuid, &mymsgok);
 108                 break;
 109         default:
 110                 usage();
 111         }
 112         done(0);
 113         return (0);
 114 }
 115
 116 static void
 117 usage(void)
 118 {
 119         fprintf(stderr, "usage: write user [tty]\n");
 120         exit(1);
 121 }
 122
 123 /*
 124  * utmpx_chk - checks that the given user is actually logged in on
 125  *     the given tty
 126  */
 127 static int
 128 utmpx_chk(const char *user, const char *tty)
 129 {
 130         struct utmpentry *ep;
 131
 132         getutentries(NULL, &ep);
 133
 134         for (; ep; ep = ep->next) {
 135                 if (strcmp(user, ep->name) == 0 &&
 136                     strcmp(tty, ep->line) == 0) {
 137                         return(0);
 138                 }
 139         }
 140
 141         return(1);
 142 }
 143
 144 /*
 145  * search_utmpx - search utmpx for the "best" terminal to write to
 146  *
 147  * Ignores terminals with messages disabled, and of the rest, returns
 148  * the one with the most recent access time.  Returns as value the number
 149  * of the user's terminals with messages enabled, or -1 if the user is
 150  * not logged in at all.
 151  *
 152  * Special case for writing to yourself - ignore the terminal you're
 153  * writing from, unless that's the only terminal with messages enabled.
 154  */
 155 static void
 156 search_utmpx(const char *user, char *tty, size_t ttyl, const char *mytty, uid_t myuid)
 157 {
 158         struct utmpentry *ep;
 159         time_t bestatime, atime;
 160         int nloggedttys, nttys, msgsok, user_is_me;
 161
 162         getutentries(NULL, &ep);
 163
 164         nloggedttys = nttys = 0;
 165         bestatime = 0;
 166         user_is_me = 0;
 167         for (; ep; ep = ep->next)
 168                 if (strcmp(user, ep->name) == 0) {
 169                         ++nloggedttys;
 170                         if (term_chk(ep->line, &msgsok, &atime, 0))
 171                                 continue;       /* bad term? skip */
 172                         if (myuid && !msgsok)
 173                                 continue;       /* skip ttys with msgs off */
 174                         if (strcmp(ep->line, mytty) == 0) {
 175                                 user_is_me = 1;
 176                                 continue;       /* don't write to yourself */
 177                         }
 178                         ++nttys;
 179                         if (atime > bestatime) {
 180                                 bestatime = atime;
 181                                 strlcpy(tty, ep->line, ttyl);
 182                         }
 183                 }
 184
 185         if (nloggedttys == 0)
 186                 errx(1, "%s is not logged in", user);
 187         if (nttys == 0) {
 188                 if (user_is_me) {               /* ok, so write to yourself! */
 189                         strlcpy(tty, mytty, ttyl);
 190                         return;
 191                 }
 192                 errx(1, "%s has messages disabled", user);
 193         } else if (nttys > 1) {
 194                 warnx("%s is logged in more than once; writing to %s", user, tty);
 195         }
 196 }
 197
 198 /*
 199  * term_chk - check that a terminal exists, and get the message bit
 200  *     and the access time
 201  */
 202 static int
 203 term_chk(const char *tty, int *msgsokP, time_t *atimeP, int showerror)
 204 {
 205         struct stat s;
 206         char path[MAXPATHLEN];
 207
 208         snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
 209         if (stat(path, &s) < 0) {
 210                 if (showerror)
 211                         warn("%s", path);
 212                 return(1);
 213         }
 214         *msgsokP = (s.st_mode & S_IWGRP) != 0;  /* group write bit */
 215         *atimeP = s.st_atime;
 216         return(0);
 217 }
 218
 219 /*
 220  * do_write - actually make the connection
 221  */
 222 static void
 223 do_write(const char *tty, const char *mytty, uid_t myuid, int *mymsgok)
 224 {
 225         const char *login;
 226         char *nows;
 227         struct passwd *pwd;
 228         time_t now;
 229         char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
 230
 231         /* Determine our login name before we reopen() stdout */
 232         if ((login = getlogin()) == NULL) {
 233                 if ((pwd = getpwuid(myuid)))
 234                         login = pwd->pw_name;
 235                 else
 236                         login = "???";
 237         }
 238
 239         snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
 240         if ((freopen(path, "w", stdout)) == NULL)
 241                 err(1, "%s", path);
 242
 243         signal(SIGINT, done);
 244         signal(SIGHUP, done);
 245
 246         /* print greeting */
 247         if (gethostname(host, sizeof(host)) < 0)
 248                 strlcpy(host, "???", sizeof host);
 249         now = time(NULL);
 250         nows = ctime(&now);
 251         nows[16] = '\0';
 252         printf("\r\n\007\007\007Message from %s@%s on %s at %s (%s %s replies)...\r\n",
 253             login, host, mytty, nows + 11, login, *mymsgok == 0 ? "does not accept" : "accepts");
 254
 255         while (fgets(line, sizeof(line), stdin) != NULL)
 256                 wr_fputs(line);
 257 }
 258
 259 /*
 260  * done - cleanup and exit
 261  */
 262 static void
 263 done(__unused int n)
 264 {
 265         printf("EOF\r\n");
 266         exit(0);
 267 }
 268
 269 /*
 270  * wr_fputs - like fputs(), but makes control characters visible and
 271  *     turns \n into \r\n
 272  */
 273 static void
 274 wr_fputs(unsigned char *s)
 275 {
 276
 277 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL);
 278
 279         for (; *s != '\0'; ++s) {
 280                 if (*s == '\n') {
 281                         PUTC('\r');
 282                 } else if (((*s & 0x80) && *s < 0xA0) ||
 283                            /* disable upper controls */
 284                            (!isprint(*s) && !isspace(*s) &&
 285                             *s != '\a' && *s != '\b')
 286                           ) {
 287                         if (*s & 0x80) {
 288                                 *s &= ~0x80;
 289                                 PUTC('M');
 290                                 PUTC('-');
 291                         }
 292                         if (iscntrl(*s)) {
 293                                 *s ^= 0x40;
 294                                 PUTC('^');
 295                         }
 296                 }
 297                 PUTC(*s);
 298         }
 299         return;
 300 #undef PUTC
 301 }