basic_cmds/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. 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
  37 #include <sys/cdefs.h>
  38 #ifndef lint
  39 __unused static const char copyright[] =
  40 "@(#) Copyright (c) 1989, 1993\n\
  41         The Regents of the University of California.  All rights reserved.\n";
  42 #endif
  43
  44 #if 0
  45 #ifndef lint
  46 static char sccsid[] = "@(#)write.c     8.1 (Berkeley) 6/6/93";
  47 #endif
  48 #endif
  49
  50 __RCSID("$FreeBSD: src/usr.bin/write/write.c,v 1.17 2002/09/04 23:29:09 dwmalone Exp $");
  51
  52 #include <sys/param.h>
  53 #include <sys/signal.h>
  54 #include <sys/stat.h>
  55 #include <sys/file.h>
  56 #include <sys/time.h>
  57 #include <ctype.h>
  58 #include <err.h>
  59 #include <locale.h>
  60 #include <paths.h>
  61 #include <pwd.h>
  62 #include <stdio.h>
  63 #include <stdlib.h>
  64 #include <string.h>
  65 #include <unistd.h>
  66 #include <utmpx.h>
  67
  68 void done(int);
  69 void do_write(char *, char *, uid_t);
  70 static void usage(void);
  71 int term_chk(char *, int *, time_t *, int);
  72 void wr_fputs(unsigned char *s);
  73 void search_utmp(char *, char *, char *, uid_t);
  74 int utmp_chk(char *, char *);
  75
  76 int
  77 main(int argc, char **argv)
  78 {
  79         char *cp;
  80         time_t atime;
  81         uid_t myuid;
  82         int msgsok, myttyfd;
  83         char tty[MAXPATHLEN], *mytty;
  84
  85         (void)setlocale(LC_CTYPE, "");
  86
  87         while (getopt(argc, argv, "") != -1)
  88                 usage();
  89         argc -= optind;
  90         argv += optind;
  91
  92         /* check that sender has write enabled */
  93         if (isatty(fileno(stdin)))
  94                 myttyfd = fileno(stdin);
  95         else if (isatty(fileno(stdout)))
  96                 myttyfd = fileno(stdout);
  97         else if (isatty(fileno(stderr)))
  98                 myttyfd = fileno(stderr);
  99         else
 100                 myttyfd=-1;
 101         if(myttyfd == -1)
 102                 mytty = "tty??";
 103         else
 104         {
 105         if (!(mytty = ttyname(myttyfd)))
 106                 errx(1, "can't find your tty's name");
 107         if ((cp = rindex(mytty, '/')))
 108                 mytty = cp + 1;
 109         if (term_chk(mytty, &msgsok, &atime, 1))
 110                 exit(1);
 111         if (!msgsok)
 112                 errx(1, "you have write permission turned off");
 113         }
 114         myuid = getuid();
 115
 116         /* check args */
 117         switch (argc) {
 118         case 1:
 119                 search_utmp(argv[0], tty, mytty, myuid);
 120                 do_write(tty, mytty, myuid);
 121                 break;
 122         case 2:
 123                 if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV)))
 124                         argv[1] += strlen(_PATH_DEV);
 125                 if (utmp_chk(argv[0], argv[1]))
 126                         errx(1, "%s is not logged in on %s", argv[0], argv[1]);
 127                 if (term_chk(argv[1], &msgsok, &atime, 1))
 128                         exit(1);
 129                 if (myuid && !msgsok)
 130                         errx(1, "%s has messages disabled on %s", argv[0], argv[1]);
 131                 do_write(argv[1], mytty, myuid);
 132                 break;
 133         default:
 134                 usage();
 135         }
 136         done(0);
 137         return (0);
 138 }
 139
 140 static void
 141 usage(void)
 142 {
 143         (void)fprintf(stderr, "usage: write user [tty]\n");
 144         exit(1);
 145 }
 146
 147 /*
 148  * utmp_chk - checks that the given user is actually logged in on
 149  *     the given tty
 150  */
 151 int
 152 utmp_chk(char *user, char *tty)
 153 {
 154         struct utmpx *u;
 155
 156         setutxent();
 157         while((u = getutxent()) != NULL)
 158                 if(strncmp(u->ut_line, tty, sizeof(u->ut_line)) == 0) {
 159                         if(u->ut_type == USER_PROCESS &&
 160                           strncmp(u->ut_user, user, sizeof(u->ut_user)) == 0) {
 161                                 endutxent();
 162                                 return 0;
 163                         }
 164                         break;
 165                 }
 166         endutxent();
 167         return 1;
 168 }
 169
 170 /*
 171  * search_utmp - search utmp for the "best" terminal to write to
 172  *
 173  * Ignores terminals with messages disabled, and of the rest, returns
 174  * the one with the most recent access time.  Returns as value the number
 175  * of the user's terminals with messages enabled, or -1 if the user is
 176  * not logged in at all.
 177  *
 178  * Special case for writing to yourself - ignore the terminal you're
 179  * writing from, unless that's the only terminal with messages enabled.
 180  */
 181 void
 182 search_utmp(char *user, char *tty, char *mytty, uid_t myuid)
 183 {
 184         struct utmpx ux, *u;
 185         time_t bestatime, atime;
 186         int nloggedttys, nttys, msgsok, user_is_me;
 187         char atty[sizeof(ux.ut_line) + 1];
 188
 189         nloggedttys = nttys = 0;
 190         bestatime = 0;
 191         user_is_me = 0;
 192         setutxent();
 193         while ((u = getutxent()) != NULL) {
 194                 if (u->ut_type != USER_PROCESS)
 195                         continue;
 196                 if (strncmp(user, u->ut_user, sizeof(u->ut_user)) == 0) {
 197                         ++nloggedttys;
 198                         (void)strlcpy(atty, u->ut_line, sizeof(atty));
 199                         if (term_chk(atty, &msgsok, &atime, 0))
 200                                 continue;       /* bad term? skip */
 201                         if (myuid && !msgsok)
 202                                 continue;       /* skip ttys with msgs off */
 203                         if (strcmp(atty, mytty) == 0) {
 204                                 user_is_me = 1;
 205                                 continue;       /* don't write to yourself */
 206                         }
 207                         ++nttys;
 208                         if (atime > bestatime) {
 209                                 bestatime = atime;
 210                                 (void)strcpy(tty, atty);
 211                         }
 212                 }
 213         }
 214
 215         endutxent();
 216         if (nloggedttys == 0)
 217                 errx(1, "%s is not logged in", user);
 218         if (nttys == 0) {
 219                 if (user_is_me) {               /* ok, so write to yourself! */
 220                         (void)strcpy(tty, mytty);
 221                         return;
 222                 }
 223                 errx(1, "%s has messages disabled", user);
 224         } else if (nttys > 1) {
 225                 warnx("%s is logged in more than once; writing to %s", user, tty);
 226         }
 227 }
 228
 229 /*
 230  * term_chk - check that a terminal exists, and get the message bit
 231  *     and the access time
 232  */
 233 int
 234 term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror)
 235 {
 236         struct stat s;
 237         char path[MAXPATHLEN];
 238
 239         (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
 240         if (stat(path, &s) < 0) {
 241                 if (showerror)
 242                         warn("%s", path);
 243                 return(1);
 244         }
 245         *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0;  /* group write bit */
 246         *atimeP = s.st_atime;
 247         return(0);
 248 }
 249
 250 /*
 251  * do_write - actually make the connection
 252  */
 253 void
 254 do_write(char *tty, char *mytty, uid_t myuid)
 255 {
 256         const char *login;
 257         char *nows;
 258         struct passwd *pwd;
 259         time_t now;
 260         char path[MAXPATHLEN], host[MAXHOSTNAMELEN], line[512];
 261
 262         /* Determine our login name before the we reopen() stdout */
 263         if ((login = getlogin()) == NULL) {
 264                 if ((pwd = getpwuid(myuid)))
 265                         login = pwd->pw_name;
 266                 else
 267                         login = "???";
 268         }
 269
 270         (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty);
 271         if ((freopen(path, "w", stdout)) == NULL)
 272                 err(1, "%s", path);
 273
 274         (void)signal(SIGINT, done);
 275         (void)signal(SIGHUP, done);
 276
 277         /* print greeting */
 278         if (gethostname(host, sizeof(host)) < 0)
 279                 (void)strcpy(host, "???");
 280         now = time((time_t *)NULL);
 281         nows = ctime(&now);
 282         nows[16] = '\0';
 283         (void)printf("\r\n\007\007\007Message from %s@%s on %s at %s ...\r\n",
 284             login, host, mytty, nows + 11);
 285
 286         while (fgets(line, sizeof(line), stdin) != NULL)
 287                 wr_fputs((unsigned char *)line);
 288 }
 289
 290 /*
 291  * done - cleanup and exit
 292  */
 293 void
 294 done(int n)
 295 {
 296         (void)printf("EOF\r\n");
 297         exit(0);
 298 }
 299
 300 /*
 301  * wr_fputs - like fputs(), but makes control characters visible and
 302  *     turns \n into \r\n
 303  */
 304 void
 305 wr_fputs(unsigned char *s)
 306 {
 307
 308 #define PUTC(c) if (putchar(c) == EOF) err(1, NULL);
 309
 310         for (; *s != '\0'; ++s) {
 311                 if (*s == '\n') {
 312                         PUTC('\r');
 313                 } else if (((*s & 0x80) && *s < 0xA0) ||
 314                            /* disable upper controls */
 315                            (!isprint(*s) && !isspace(*s) &&
 316                             *s != '\a' && *s != '\b')
 317                           ) {
 318                         if (*s & 0x80) {
 319                                 *s &= ~0x80;
 320                                 PUTC('M');
 321                                 PUTC('-');
 322                         }
 323                         if (iscntrl(*s)) {
 324                                 *s ^= 0x40;
 325                                 PUTC('^');
 326                         }
 327                 }
 328                 PUTC(*s);
 329         }
 330         return;
 331 #undef PUTC
 332 }