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announce.c

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. 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.
 */

/*
 * From: @(#)announce.c 5.9 (Berkeley) 2/26/91
 */
char ann_rcsid[] = 
  "$Id: announce.c,v 1.8 2000/07/22 15:27:39 dholland Exp $";

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <errno.h>
#include <syslog.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <paths.h>
#include "prot_talkd.h"
#include "proto.h"

/*
 * Announce an invitation to talk.
 *
 * Because the tty driver insists on attaching a terminal-less
 * process to any terminal that it writes on, we must fork a child
 * to protect ourselves.
 *
 * That hasn't been true since, hrm, 4.2BSD maybe? Even in System V,
 * we can use O_NOCTTY. On the other hand, forking is a good idea in
 * case the tty hangs. But at present we don't take advantage of that;
 * we'd wait() forever.
 */


/*
 * Reject control codes and other crap.
 * FUTURE: don't clear high ascii if the tty is in 8-bit mode
 * Note that we don't need to let through tabs or newlines here.
 */
static int safechar(int ch) {
    if (ch>127 || ch<32) ch = '?';
    return ch;
}

#define max(a,b) ( (a) > (b) ? (a) : (b) )
#define N_LINES 5
#define N_CHARS 120

/*
 * Build a block of characters containing the message. 
 * It is sent blank filled and in a single block to
 * try to keep the message in one piece if the recipient
 * is in, say, vi at the time.
 */
static void
print_mesg(int fd, CTL_MSG *request, const char *remote_machine)
{
      struct timeval clocc;
      struct timezone zone;
      struct tm *localclock;
      char line_buf[N_LINES][N_CHARS];
      int sizes[N_LINES];
      char big_buf[N_LINES*(N_CHARS+2)+16];
      char *bptr, *lptr;
      int i, j, max_size;
      time_t footime;

      i = 0;
      max_size = 0;
      gettimeofday(&clocc, &zone);
      footime = clocc.tv_sec;
      localclock = localtime(&footime);
      snprintf(line_buf[i], N_CHARS, " ");
      sizes[i] = strlen(line_buf[i]);
      max_size = max(max_size, sizes[i]);
      i++;
      snprintf(line_buf[i], N_CHARS, 
             "Message from Talk_Daemon@%s at %d:%02d ...",
             ourhostname, localclock->tm_hour, localclock->tm_min);
      sizes[i] = strlen(line_buf[i]);
      max_size = max(max_size, sizes[i]);
      i++;
      snprintf(line_buf[i], N_CHARS, "talk: connection requested by %s@%s.",
            request->l_name, remote_machine);
      sizes[i] = strlen(line_buf[i]);
      max_size = max(max_size, sizes[i]);
      i++;
      snprintf(line_buf[i], N_CHARS, "talk: respond with:  talk %s@%s",
             request->l_name, remote_machine);
      sizes[i] = strlen(line_buf[i]);
      max_size = max(max_size, sizes[i]);
      i++;
      snprintf(line_buf[i], N_CHARS, " ");
      sizes[i] = strlen(line_buf[i]);
      max_size = max(max_size, sizes[i]);
      i++;
      bptr = big_buf;
      *bptr++ = ''; /* send something to wake them up */
      *bptr++ = '\r';   /* add a \r in case of raw mode */
      *bptr++ = '\n';
      for (i = 0; i < N_LINES; i++) {
            /* copy the line into the big buffer */
            lptr = line_buf[i];
            while (*lptr != '\0')
                  *(bptr++) = safechar(*(lptr++));
            /* pad out the rest of the lines with blanks */
            for (j = sizes[i]; j < max_size + 2; j++)
                  *(bptr++) = ' ';
            *(bptr++) = '\r'; /* add a \r in case of raw mode */
            *(bptr++) = '\n';
      }
      *bptr = 0;
      write(fd, big_buf, strlen(big_buf));
}

/*
 * See if the user is accepting messages. If so, announce that 
 * a talk is requested.
 */
static int
announce_proc(CTL_MSG *request, const char *remote_machine)
{
      char full_tty[32];
      int fd;
      struct stat stbuf;

      snprintf(full_tty, sizeof(full_tty), "%s/%s", _PATH_DEV, 
             request->r_tty);
      if (access(full_tty, F_OK) != 0)
            return FAILED;
      fd = open(full_tty, O_WRONLY|O_NOCTTY);
      if (fd<0) {
            return (PERMISSION_DENIED);
      }
      if (fstat(fd, &stbuf) < 0) {
            return (PERMISSION_DENIED);
      }
      if ((stbuf.st_mode&020) == 0) {
            return (PERMISSION_DENIED);
      }
      print_mesg(fd, request, remote_machine);
      close(fd);
      return SUCCESS;
}

int
announce(CTL_MSG *request, const char *remote_machine)
{
      int pid, val, status;

      pid = fork();
      if (pid==-1) {
            /* fork failed */
            return FAILED;
      }
      if (pid==0) {
            /* child */
            status = announce_proc(request, remote_machine);
            _exit(status);
      }

      /* we are the parent, so wait for the child */
      do {
            val = wait(&status);
            if (val == -1) {
                  if (errno == EINTR || errno == EAGAIN)
                        continue;
                  /* shouldn't happen */
                  syslog(LOG_WARNING, "announce: wait: %m");
                  return (FAILED);
            }
      } while (val != pid);

      if (WIFSIGNALED(status)) {
            /* we were killed by some signal */
            return FAILED;
      }
      /* Send back the exit/return code */
      return (WEXITSTATUS(status));
}

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