misc-utils/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. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * Modified for Linux, Mon Mar  8 18:16:24 1993, faith@cs.unc.edu
  37  * Wed Jun 22 21:41:56 1994, faith@cs.unc.edu:
  38  *      Added fix from Mike Grupenhoff (kashmir@umiacs.umd.edu)
  39  * Mon Jul  1 17:01:39 MET DST 1996, janl@math.uio.no:
  40  *      - Added fix from David.Chapell@mail.trincoll.edu enabeling daemons
  41  *        to use write.
  42  *      - ANSIed it since I was working on it anyway.
  43  * 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@misiek.eu.org>
  44  * - added Native Language Support
  45  *
  46  */
  47
  48 #include <stdio.h>
  49 #include <unistd.h>
  50 #include <utmp.h>
  51 #include <errno.h>
  52 #include <ctype.h>
  53 #include <time.h>
  54 #include <pwd.h>
  55 #include <string.h>
  56 #include <stdlib.h>
  57 #include <locale.h>
  58 #include <signal.h>
  59 #include <sys/param.h>
  60 #include <sys/signal.h>
  61 #include <sys/stat.h>
  62 #include <sys/file.h>
  63 #include <sys/time.h>
  64 #include <paths.h>
  65 #include "pathnames.h"
  66 #include "carefulputc.h"
  67 #include "nls.h"
  68
  69 void search_utmp(char *, char *, char *, uid_t);
  70 void do_write(char *, char *, uid_t);
  71 void wr_fputs(char *);
  72 static void done(int);
  73 int term_chk(char *, int *, time_t *, int);
  74 int utmp_chk(char *, char *);
  75
  76 int
  77 main(int argc, char **argv) {
  78         time_t atime;
  79         uid_t myuid;
  80         int msgsok, myttyfd;
  81         char tty[MAXPATHLEN], *mytty;
  82
  83         setlocale(LC_ALL, "");
  84         bindtextdomain(PACKAGE, LOCALEDIR);
  85         textdomain(PACKAGE);
  86
  87         /* check that sender has write enabled */
  88         if (isatty(fileno(stdin)))
  89                 myttyfd = fileno(stdin);
  90         else if (isatty(fileno(stdout)))
  91                 myttyfd = fileno(stdout);
  92         else if (isatty(fileno(stderr)))
  93                 myttyfd = fileno(stderr);
  94         else {
  95                 myttyfd = -1;
  96         }
  97         if (myttyfd != -1) {
  98           if (!(mytty = ttyname(myttyfd))) {
  99                 (void)fprintf(stderr, _("write: can't find your tty's name\n"));
 100                 exit(1);
 101           }
 102           /* We may have /dev/ttyN but also /dev/pts/xx.
 103              Below, term_chk() will put "/dev/" in front, so remove that part. */
 104           if (!strncmp(mytty, "/dev/", 5))
 105                 mytty += 5;
 106           if (term_chk(mytty, &msgsok, &atime, 1))
 107                 exit(1);
 108           if (!msgsok) {
 109                 (void)fprintf(stderr,
 110                     _("write: you have write permission turned off.\n"));
 111                 exit(1);
 112           }
 113
 114         } else {
 115             mytty = "<no tty>";
 116         }
 117
 118         myuid = getuid();
 119
 120         /* check args */
 121         switch (argc) {
 122         case 2:
 123                 search_utmp(argv[1], tty, mytty, myuid);
 124                 do_write(tty, mytty, myuid);
 125                 break;
 126         case 3:
 127                 if (!strncmp(argv[2], "/dev/", 5))
 128                         argv[2] += 5;
 129                 if (utmp_chk(argv[1], argv[2])) {
 130                         (void)fprintf(stderr,
 131                             _("write: %s is not logged in on %s.\n"),
 132                             argv[1], argv[2]);
 133                         exit(1);
 134                 }
 135                 if (term_chk(argv[2], &msgsok, &atime, 1))
 136                         exit(1);
 137                 if (myuid && !msgsok) {
 138                         (void)fprintf(stderr,
 139                             _("write: %s has messages disabled on %s\n"),
 140                             argv[1], argv[2]);
 141                         exit(1);
 142                 }
 143                 do_write(argv[2], mytty, myuid);
 144                 break;
 145         default:
 146                 (void)fprintf(stderr, _("usage: write user [tty]\n"));
 147                 exit(1);
 148         }
 149         done(0);
 150         /* NOTREACHED */
 151         return 0;
 152 }
 153
 154
 155 /*
 156  * utmp_chk - checks that the given user is actually logged in on
 157  *     the given tty
 158  */
 159 int utmp_chk(char *user, char *tty)
 160
 161 {
 162         struct utmp u;
 163         struct utmp *uptr;
 164         int res = 1;
 165
 166         utmpname(_PATH_UTMP);
 167         setutent();
 168
 169         while ((uptr = getutent())) {
 170                 memcpy(&u, uptr, sizeof(u));
 171                 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0 &&
 172                     strncmp(tty, u.ut_line, sizeof(u.ut_line)) == 0) {
 173                         res = 0;
 174                         break;
 175                 }
 176         }
 177
 178         endutent();
 179         return(res);
 180 }
 181
 182 /*
 183  * search_utmp - search utmp for the "best" terminal to write to
 184  *
 185  * Ignores terminals with messages disabled, and of the rest, returns
 186  * the one with the most recent access time.  Returns as value the number
 187  * of the user's terminals with messages enabled, or -1 if the user is
 188  * not logged in at all.
 189  *
 190  * Special case for writing to yourself - ignore the terminal you're
 191  * writing from, unless that's the only terminal with messages enabled.
 192  */
 193 void search_utmp(char *user, char *tty, char *mytty, uid_t myuid)
 194
 195 {
 196         struct utmp u;
 197         struct utmp *uptr;
 198         time_t bestatime, atime;
 199         int nloggedttys, nttys, msgsok, user_is_me;
 200 #ifdef __linux__
 201         char atty[sizeof(u.ut_line) + 1];
 202 #else
 203         char atty[UT_LINESIZE + 1];
 204 #endif
 205
 206         utmpname(_PATH_UTMP);
 207         setutent();
 208
 209         nloggedttys = nttys = 0;
 210         bestatime = 0;
 211         user_is_me = 0;
 212         while ((uptr = getutent())) {
 213                 memcpy(&u, uptr, sizeof(u));
 214                 if (strncmp(user, u.ut_name, sizeof(u.ut_name)) == 0) {
 215                         ++nloggedttys;
 216 #ifdef __linux__
 217                         (void)strncpy(atty, u.ut_line, sizeof(u.ut_line));
 218                         atty[sizeof(u.ut_line)] = '\0';
 219 #else
 220                         (void)strncpy(atty, u.ut_line, UT_LINESIZE);
 221                         atty[UT_LINESIZE] = '\0';
 222 #endif
 223                         if (term_chk(atty, &msgsok, &atime, 0))
 224                                 continue;       /* bad term? skip */
 225                         if (myuid && !msgsok)
 226                                 continue;       /* skip ttys with msgs off */
 227                         if (strcmp(atty, mytty) == 0) {
 228                                 user_is_me = 1;
 229                                 continue;       /* don't write to yourself */
 230                         }
 231 #ifdef __linux__
 232                         if (u.ut_type != USER_PROCESS)
 233                                 continue;       /* it's not a valid entry */
 234 #endif
 235                         ++nttys;
 236                         if (atime > bestatime) {
 237                                 bestatime = atime;
 238                                 (void)strcpy(tty, atty);
 239                         }
 240                 }
 241         }
 242
 243         endutent();
 244         if (nloggedttys == 0) {
 245                 (void)fprintf(stderr, _("write: %s is not logged in\n"), user);
 246                 exit(1);
 247         }
 248         if (nttys == 0) {
 249                 if (user_is_me) {               /* ok, so write to yourself! */
 250                         (void)strcpy(tty, mytty);
 251                         return;
 252                 }
 253                 (void)fprintf(stderr,
 254                     _("write: %s has messages disabled\n"), user);
 255                 exit(1);
 256         } else if (nttys > 1) {
 257                 (void)fprintf(stderr,
 258                     _("write: %s is logged in more than once; writing to %s\n"),
 259                     user, tty);
 260         }
 261 }
 262
 263 /*
 264  * term_chk - check that a terminal exists, and get the message bit
 265  *     and the access time
 266  */
 267 int term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
 268
 269 {
 270         struct stat s;
 271         char path[MAXPATHLEN];
 272
 273         if (strlen(tty) + 6 > sizeof(path))
 274                 return(1);
 275         (void)sprintf(path, "/dev/%s", tty);
 276         if (stat(path, &s) < 0) {
 277                 if (showerror)
 278                         (void)fprintf(stderr,
 279                             "write: %s: %s\n", path, strerror(errno));
 280                 return(1);
 281         }
 282         *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0;  /* group write bit */
 283         *atimeP = s.st_atime;
 284         return(0);
 285 }
 286
 287 /*
 288  * do_write - actually make the connection
 289  */
 290 void do_write(char *tty, char *mytty, uid_t myuid) {
 291         char *login, *pwuid, *nows;
 292         struct passwd *pwd;
 293         time_t now;
 294         char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
 295
 296         /* Determine our login name(s) before the we reopen() stdout */
 297         if ((pwd = getpwuid(myuid)) != NULL)
 298                 pwuid = pwd->pw_name;
 299         else
 300                 pwuid = "???";
 301         if ((login = getlogin()) == NULL)
 302                 login = pwuid;
 303
 304         if (strlen(tty) + 6 > sizeof(path))
 305                 exit(1);
 306         (void)sprintf(path, "/dev/%s", tty);
 307         if ((freopen(path, "w", stdout)) == NULL) {
 308                 (void)fprintf(stderr, "write: %s: %s\n",
 309                               path, strerror(errno));
 310                 exit(1);
 311         }
 312
 313         (void)signal(SIGINT, done);
 314         (void)signal(SIGHUP, done);
 315
 316         /* print greeting */
 317         if (gethostname(host, sizeof(host)) < 0)
 318                 (void)strcpy(host, "???");
 319         now = time((time_t *)NULL);
 320         nows = ctime(&now);
 321         nows[16] = '\0';
 322         printf("\r\n\007\007\007");
 323         if (strcmp(login, pwuid))
 324                 (void)printf(_("Message from %s@%s (as %s) on %s at %s ..."),
 325                              login, host, pwuid, mytty, nows + 11);
 326         else
 327                 (void)printf(_("Message from %s@%s on %s at %s ..."),
 328                              login, host, mytty, nows + 11);
 329         printf("\r\n");
 330
 331         while (fgets(line, sizeof(line), stdin) != NULL)
 332                 wr_fputs(line);
 333 }
 334
 335 /*
 336  * done - cleanup and exit
 337  */
 338 static void
 339 done(int dummy) {
 340         (void)printf("EOF\r\n");
 341         exit(0);
 342 }
 343
 344 /*
 345  * wr_fputs - like fputs(), but makes control characters visible and
 346  *     turns \n into \r\n.
 347  */
 348 void
 349 wr_fputs(char *s) {
 350         char c;
 351
 352 #define PUTC(c) if (carefulputc(c,stdout) == EOF) goto err;
 353
 354         while(*s) {
 355                 c = *s++;
 356                 if (c == '\n')
 357                         PUTC('\r');
 358                 PUTC(c);
 359         }
 360         return;
 361
 362 err:
 363         fprintf(stderr, "write: %s\n", strerror(errno));
 364         exit(1);
 365 #undef PUTC
 366 }