inetutils/talkd/process.c

/*
  Copyright (C) 1996-2025 Free Software Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or (at
  your option) any later version.

  GNU Inetutils is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see `http://www.gnu.org/licenses/'. */

#include <config.h>

#include <intalkd.h>
#include <readutmp.h>

int find_user (char *name, char *tty);
void do_announce (CTL_MSG * mp, CTL_RESPONSE * rp);

int
process_request (CTL_MSG *msg, struct sockaddr_in *sa_in, CTL_RESPONSE *rp)
{
  CTL_MSG *ptr;

  rp->vers = TALK_VERSION;
  rp->type = msg->type;
  rp->id_num = htonl (0);
  if (msg->vers != TALK_VERSION)
    {
      if (logging || debug)
	syslog (LOG_NOTICE, "Bad protocol version %d", msg->vers);
      rp->answer = BADVERSION;
      return 0;
    }

  /* Convert the machine independent representation
   * of the talk protocol to the present architecture.
   * In particular, `msg->addr.sa_family' will be
   * valid for socket initialization.
   */
  msg->id_num = ntohl (msg->id_num);
  msg->addr.sa_family = ntohs (msg->addr.sa_family);
  if (msg->addr.sa_family != AF_INET)
    {
      if (logging || debug)
	syslog (LOG_NOTICE, "Bad address, family %d", msg->addr.sa_family);
      rp->answer = BADADDR;
      return 0;
    }
  /* Convert to valid socket address for this architecture.  */
  msg->ctl_addr.sa_family = ntohs (msg->ctl_addr.sa_family);
  if (msg->ctl_addr.sa_family != AF_INET)
    {
      if (logging || debug)
	syslog (LOG_NOTICE, "Bad control address, family %d",
		msg->ctl_addr.sa_family);
      rp->answer = BADCTLADDR;
      return 0;
    }
  /* FIXME: compare address and sa_in? */

  if (acl_match (msg, sa_in) == ACL_DENY)
    {
      /* This denial happens for each of LOOK_UP,
       * ANNOUNCE, and DELETE, in this order.
       * Make a syslog note only for the first of them.
       */
      if ((logging || debug) && msg->type == LOOK_UP)
	syslog (LOG_NOTICE, "dropping request: %s@%s",
		msg->l_name, inet_ntoa (sa_in->sin_addr));

      /* The answer FAILED is returned to minimize the amount
       * of information disclosure, since ACL has denied access.
       */
      rp->answer = FAILED;
      return 0;
    }

  if (debug)
    {
      print_request ("process_request", msg);
    }

  msg->pid = ntohl (msg->pid);

  switch (msg->type)
    {
    case ANNOUNCE:
      do_announce (msg, rp);
      if (logging && rp->answer == SUCCESS)
	syslog (LOG_INFO, "%s@%s called by %s@%s",
		msg->r_name,
		(msg->r_tty[0]
		 ? msg->r_tty
		 : inet_ntoa (sa_in->sin_addr)),
		msg->l_name, inet_ntoa (os2sin_addr (msg->addr)));
      break;

    case LEAVE_INVITE:
      ptr = find_request (msg);
      if (ptr)
	{
	  rp->id_num = htonl (ptr->id_num);
	  rp->answer = SUCCESS;
	}
      else
	insert_table (msg, rp);
      break;

    case LOOK_UP:
      ptr = find_match (msg);
      if (ptr)
	{
	  rp->id_num = htonl (ptr->id_num);
	  rp->addr = ptr->addr;
	  rp->addr.sa_family = htons (ptr->addr.sa_family);
	  rp->answer = SUCCESS;
	  if (logging)
	    syslog (LOG_INFO, "%s talks to %s@%s",
		    msg->r_name, msg->l_name, inet_ntoa (sa_in->sin_addr));
	}
      else
	rp->answer = NOT_HERE;
      break;

    case DELETE:
      rp->answer = delete_invite (msg->id_num);
      break;

    default:
      rp->answer = UNKNOWN_REQUEST;
      break;
    }

  if (debug)
    print_response ("process_request response", rp);

  return 0;
}

void
do_announce (CTL_MSG *mp, CTL_RESPONSE *rp)
{
  struct hostent *hp;
  CTL_MSG *ptr;
  int result;

  result = find_user (mp->r_name, mp->r_tty);
  if (result != SUCCESS)
    {
      rp->answer = result;
      return;
    }

  hp = gethostbyaddr ((char *) &os2sin_addr (mp->ctl_addr),
		      sizeof (struct in_addr), AF_INET);
  if (!hp)
    {
      rp->answer = MACHINE_UNKNOWN;
      return;
    }
  ptr = find_request (mp);
  if (!ptr)
    {
      insert_table (mp, rp);
      rp->answer = announce (mp, hp->h_name);
      return;
    }
  if (mp->id_num > ptr->id_num)
    {
      /* Explicit re-announce: update the id_num to avoid duplicates
         and re-announce the talk. */
      ptr->id_num = new_id ();
      rp->id_num = htonl (ptr->id_num);
      rp->answer = announce (mp, hp->h_name);
    }
  else
    {
      /* a duplicated request, so ignore it */
      rp->id_num = htonl (ptr->id_num);
      rp->answer = SUCCESS;
    }
}

/* Search utmp for the local user.  */
int
find_user (char *name, char *tty)
{
  STRUCT_UTMP *uptr;
#ifndef HAVE_GETUTXUSER
  STRUCT_UTMP *utmpbuf;
  size_t utmp_count;
#endif /* HAVE_GETUTXUSER */
  int status;
  struct stat statb;
  char ftty[sizeof (PATH_TTY_PFX) + sizeof (uptr->ut_line)];
  time_t last_time = 0;
  int notty;

  notty = (*tty == '\0');

  status = NOT_HERE;
  strcpy (ftty, PATH_TTY_PFX);

/* *INDENT-OFF* */
#ifdef HAVE_GETUTXUSER
  setutxent ();

  while ((uptr = getutxuser (name)))
#else /* !HAVE_GETUTXUSER */
  if (read_utmp (UTMP_FILE, &utmp_count, &utmpbuf,
		 READ_UTMP_USER_PROCESS | READ_UTMP_CHECK_PIDS) < 0)
    return FAILED;

  for (uptr = utmpbuf; uptr < utmpbuf + utmp_count; uptr++)
    {
      if (!strncmp (UT_USER (uptr), name, sizeof (UT_USER (uptr))))
#endif /* !HAVE_GETUTXUSER */
/* *INDENT-ON* */
  {
    if (notty)
      {
	/* no particular tty was requested */
	strncpy (ftty + sizeof (PATH_TTY_PFX) - 1,
		 uptr->ut_line, sizeof (ftty) - sizeof (PATH_TTY_PFX) - 1);
	ftty[sizeof (ftty) - 1] = 0;

	if (stat (ftty, &statb) == 0)
	  {
	    if (!(statb.st_mode & S_IWGRP))
	      {
		if (status != SUCCESS)
		  status = PERMISSION_DENIED;
		continue;
	      }
	    if (statb.st_atime > last_time)
	      {
		last_time = statb.st_atime;
		strcpy (tty, uptr->ut_line);
		status = SUCCESS;
	      }
	    continue;
	  }
      }
    if (!strcmp (uptr->ut_line, tty))
      {
	status = SUCCESS;
	break;
      }
  }
/* *INDENT-OFF* */
#ifndef HAVE_GETUTXUSER
    }
  free (utmpbuf);
#else /* HAVE_GETUTXUSER */
  endutxent ();
#endif
/* *INDENT-ON* */

  return status;
}