/*      $NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $ */

/*
* Copyright (c) 1989, 1993
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jef Poskanzer and Craig Leres of the Lawrence Berkeley Laboratory.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#include <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)write.c     8.2 (Berkeley) 4/27/95";
#else
__RCSID("$NetBSD: write.c,v 1.27 2011/09/06 18:46:35 joerg Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <time.h>
#include <fcntl.h>
#include <paths.h>
#include <pwd.h>
#include <unistd.h>
#include <err.h>
#include <errno.h>

#include "utmpentry.h"
#include "term_chk.h"

__dead static void done(int);
static void do_write(int, const char *, const uid_t);
static void wr_fputs(char *);
static int search_utmp(char *, char *, uid_t, gid_t);
static int utmp_chk(const char *, const char *);

int
main(int argc, char **argv)
{
       time_t atime;
       uid_t myuid, uid;
       int msgsok, ttyfd;
       char *mytty;
       gid_t saved_egid = getegid();

       if (setegid(getgid()) == -1)
               err(1, "setegid");
       myuid = getuid();
       ttyfd = -1;

       mytty = check_sender(&atime, myuid, saved_egid);

       /* check args */
       switch (argc) {
       case 2:
               ttyfd = search_utmp(argv[1], mytty, myuid, saved_egid);
               break;
       case 3:
               if (!strncmp(argv[2], _PATH_DEV, strlen(_PATH_DEV)))
                       argv[2] += strlen(_PATH_DEV);
               if (uid_from_user(argv[1], &uid) == -1)
                       errx(1, "%s: unknown user", argv[1]);
               if (utmp_chk(argv[1], argv[2]))
                       errx(1, "%s is not logged in on %s",
                           argv[1], argv[2]);
               ttyfd = term_chk(uid, argv[2], &msgsok, &atime, 0, saved_egid);
               if (ttyfd == -1)
                       err(1, "%s%s", _PATH_DEV, argv[2]);
               if (myuid && !msgsok)
                       errx(1, "%s has messages disabled on %s",
                           argv[1], argv[2]);
               break;
       default:
               (void)fprintf(stderr, "usage: write user [tty]\n");
               exit(1);
       }
       if (setgid(getgid()) == -1)
               err(1, "setgid");
       do_write(ttyfd, mytty, myuid);
       done(0);
       /* NOTREACHED */
#ifdef __GNUC__
       return (0);
#endif
}

/*
* utmp_chk - checks that the given user is actually logged in on
*     the given tty
*/
static int
utmp_chk(const char *user, const char *tty)
{
       struct utmpentry *ep;

       (void)getutentries(NULL, &ep);

       for (; ep; ep = ep->next)
               if (strcmp(user, ep->name) == 0 && strcmp(tty, ep->line) == 0)
                       return(0);
       return(1);
}

/*
* search_utmp - search utmp for the "best" terminal to write to
*
* Ignores terminals with messages disabled, and of the rest, returns
* the one with the most recent access time.  Returns as value the number
* of the user's terminals with messages enabled, or -1 if the user is
* not logged in at all.
*
* Special case for writing to yourself - ignore the terminal you're
* writing from, unless that's the only terminal with messages enabled.
*/
static int
search_utmp(char *user, char *mytty, uid_t myuid, gid_t saved_egid)
{
       char tty[MAXPATHLEN];
       time_t bestatime, atime;
       int nloggedttys, nttys, msgsok, user_is_me;
       struct utmpentry *ep;
       int fd, nfd;
       uid_t uid;

       if (uid_from_user(user, &uid) == -1)
               errx(1, "%s: unknown user", user);

       (void)getutentries(NULL, &ep);

       nloggedttys = nttys = 0;
       bestatime = 0;
       user_is_me = 0;
       fd = -1;
       for (; ep; ep = ep->next)
               if (strcmp(user, ep->name) == 0) {
                       ++nloggedttys;
                       nfd = term_chk(uid, ep->line, &msgsok, &atime, 0,
                           saved_egid);
                       if (nfd == -1)
                               continue;       /* bad term? skip */
                       if (myuid && !msgsok) {
                               close(nfd);
                               continue;       /* skip ttys with msgs off */
                       }
                       if (strcmp(ep->line, mytty) == 0) {
                               user_is_me = 1;
                               if (fd == -1)
                                       fd = nfd;
                               else
                                       close(nfd);
                               continue;       /* don't write to yourself */
                       }
                       ++nttys;
                       if (atime > bestatime) {
                               bestatime = atime;
                               (void)strlcpy(tty, ep->line, sizeof(tty));
                               close(fd);
                               fd = nfd;
                       } else
                               close(nfd);
               }

       if (nloggedttys == 0)
               errx(1, "%s is not logged in", user);
       if (nttys == 0) {
               if (user_is_me)                 /* ok, so write to yourself! */
                       return fd;
               errx(1, "%s has messages disabled", user);
       } else if (nttys > 1)
               warnx("%s is logged in more than once; writing to %s",
                   user, tty);
       return fd;
}

/*
* do_write - actually make the connection
*/
static void
do_write(int ttyfd, const char *mytty, const uid_t myuid)
{
       const char *login;
       char *nows;
       struct passwd *pwd;
       time_t now;
       char host[MAXHOSTNAMELEN + 1], line[512];

       /* Determine our login name before we re-open stdout */
       if ((login = getlogin()) == NULL) {
               if ((pwd = getpwuid(myuid)) != NULL)
                       login = pwd->pw_name;
               else    login = "???";
       }

       if (dup2(ttyfd, STDOUT_FILENO) == -1)
               err(1, "dup2");

       (void)signal(SIGINT, done);
       (void)signal(SIGHUP, done);
       (void)close(ttyfd);

       /* print greeting */
       if (gethostname(host, sizeof(host)) < 0)
               (void)strlcpy(host, "???", sizeof(host));
       else
               host[sizeof(host) - 1] = '\0';
       now = time(NULL);
       nows = ctime(&now);
       nows[16] = '\0';
       (void)printf("\r\n\a\a\aMessage from %s@%s on %s at %s ...\r\n",
           login, host, mytty, nows + 11);

       while (fgets(line, sizeof(line), stdin) != NULL)
               wr_fputs(line);
}

/*
* done - cleanup and exit
*/
static void
done(int signo)
{

       (void)write(STDOUT_FILENO, "EOF\r\n", sizeof("EOF\r\n") - 1);
       if (signo == 0)
               exit(0);
       else
               _exit(0);
}

/*
* wr_fputs - like fputs(), but makes control characters visible and
*     turns \n into \r\n
*/
static void
wr_fputs(char *s)
{
       unsigned char c;

#define PUTC(c) if (putchar(c) == EOF) goto err;

       for (; *s != '\0'; ++s) {
               c = toascii(*s);
               if (c == '\n') {
                       PUTC('\r');
               } else if (!isprint(c) && !isspace(c) && c != '\a') {
                       PUTC('^');
                       c ^= 0x40;      /* DEL to ?, others to alpha */
               }
               PUTC(c);
       }
       return;

err:    err(1, NULL);
#undef PUTC
}

You are viewing proxied material from ftp.icm.edu.pl. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.