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process.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: @(#)process.c  5.10 (Berkeley) 2/26/91
 */
char rcsid[] = 
"$Id: process.c,v 1.14 1999/09/28 22:04:15 netbug Exp $";

/*
 * process.c handles the requests, which can be of three types:
 *    ANNOUNCE - announce to a user that a talk is wanted
 *    LEAVE_INVITE - insert the request into the table
 *    LOOK_UP - look up to see if a request is waiting in
 *            in the table for the local user
 *    DELETE - delete invitation
 */

#include <sys/param.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
/* #include <netinet/ip.h> <--- unused? */
#include <netdb.h>
#include <syslog.h>
#include <stdio.h>
#include <string.h>
/* #include <paths.h> <---- unused? */
#include <utmp.h>
#include "prot_talkd.h"
#include "proto.h"

static int
check_one_utmp(const struct utmp *ut, const char *name)
{
      /* 
       * We've got uptr->ut_name, and name, neither of which is
       * necessarily null-terminated. Worse, either might be larger,
       * depending on libc version. name came from a talkd
       * structure, so it's at most NAME_SIZE.  ut->ut_name is at
       * most UT_NAMESIZE. So the sum is guaranteed to hold
       * either...
       * Worse, strncmp isn't good enough. Suppose UT_NAMESIZE is 6 and 
       * NAME_SIZE is 4, and ut_name is "abcdef" and name is "abcd".
       * We don't really want those to match. Now, NAME_SIZE is 12, but
       * UT_NAMESIZE is 256 on some platforms. I suppose maybe you *want*
       * to be able to have name be a prefix of ut_name in this case, or
       * you can't talk request people with huge names at all, but suppose
       * there are several such people? Argh. *punt*
       */
      char nametmp1[UT_NAMESIZE+NAME_SIZE+1];
      char nametmp2[UT_NAMESIZE+NAME_SIZE+1];

      strncpy(nametmp1, name, NAME_SIZE);
      strncpy(nametmp2, ut->ut_name, UT_NAMESIZE);
      nametmp1[NAME_SIZE] = 0;
      nametmp2[UT_NAMESIZE] = 0;

      if (strcmp(nametmp1, nametmp2)!=0) {
            debug("utmp: %s!=%s\n", nametmp1, nametmp2);
            return NOT_HERE;
      }
      debug("utmp: %s==%s\n", nametmp1, nametmp2);
      return SUCCESS;
}

static int
check_tty_perms(const char *tty, time_t *atime)
{
      struct stat statb;

      /* our current dir is /dev, no need to prepend it */
      if (stat(tty, &statb) != 0) {
            return FAILED;
      }
      if (!(statb.st_mode & 020)) {
            return PERMISSION_DENIED;
      }
      *atime = statb.st_atime;
      return SUCCESS;
}

/*
 * Search utmp for the local user
 */
static int
find_user(const char *name, char *tty)
{
      struct utmp *uptr;
      int found=0, ok=0, ret;
      time_t best_time = 0, this_time;
      char besttty[PATH_MAX];

      *besttty = 0;
      setutent();
      while ((uptr = getutent())!=NULL) {
#ifdef USER_PROCESS
            if (uptr->ut_type!=USER_PROCESS) continue;
#endif
            ret = check_one_utmp(uptr, name);
            if (ret!=SUCCESS) {
                  /* wrong user */
                  continue;
            }
            if (*tty && !strcmp(tty, uptr->ut_line)) {
                  /* asked for a tty, found it */
                  endutent();
                  return SUCCESS;
            }
            ret = check_tty_perms(uptr->ut_line, &this_time);
            if (ret != SUCCESS) {
                  found = 1; /* but don't set ok */
                  continue;
            }
            found = ok = 1;
            if (this_time > best_time) {
                  best_time = this_time;
                  strcpy(besttty, uptr->ut_line);
            }
      }
      endutent();
      strcpy(tty, besttty);
      return !found ? NOT_HERE : (!ok ? PERMISSION_DENIED : SUCCESS);
}

static void
do_announce(CTL_MSG *mp, CTL_RESPONSE *rp, const char *fromhost)
{
      CTL_MSG *ptr;
      int result;
      u_int32_t temp;

      /* 
       * See if the user is logged in.
       * Clobbers mp->r_tty, replacing it with the tty to page them on.
       * (If mp->r_tty is not empty, should only return that tty, or fail.)
       */
      result = find_user(mp->r_name, mp->r_tty);
      if (result != SUCCESS) {
            rp->answer = result;
            return;
      }
      ptr = find_request(mp);
      if (ptr == NULL) {
            insert_table(mp, rp);
            rp->answer = announce(mp, fromhost);
            return;
      }

      /*
       * Voodoo #1: if the client is opposite-endian and old/broken,
       * it will have added one to the id while it was byte-swapped.
       * Try undoing this. If it matches the id we have on file, it
       * was a broken attempt to re-announce.
       * We don't use ntohl because if we're big-endian ntohl is a nop.
       */
      temp = byte_swap32(byte_swap32(mp->id_num)-1);

      if (mp->id_num > ptr->id_num || temp==ptr->id_num) {
            /*
             * This is an explicit re-announce, so update the id_num
             * field to avoid duplicates and re-announce the talk.
             */
            ptr->id_num = new_id();
            rp->id_num = htonl(ptr->id_num);
            rp->answer = announce(mp, fromhost);
      } 
      else {
            /* duplicated or garbage request, so ignore it */
            rp->id_num = htonl(ptr->id_num);
            rp->answer = SUCCESS;
      }
}

void
process_request(CTL_MSG *mp, CTL_RESPONSE *rp, const char *fromhost)
{
      CTL_MSG *ptr;

      /* Ensure null-termination */
      mp->l_name[sizeof(mp->l_name)-1] = 0;
      mp->r_name[sizeof(mp->r_name)-1] = 0;
      mp->r_tty[sizeof(mp->r_tty)-1] = 0;
  
      rp->vers = TALK_VERSION;
      rp->type = mp->type;
      rp->id_num = htonl(0);
      if (mp->vers != TALK_VERSION) {
            syslog(LOG_WARNING, "Bad protocol version %d", mp->vers);
            rp->answer = BADVERSION;
            return;
      }
      mp->id_num = ntohl(mp->id_num);
      mp->pid = ntohl(mp->pid);
      print_request("process_request", mp);
  
      switch (mp->type) {
        case ANNOUNCE:
            do_announce(mp, rp, fromhost);
            break;
        case LEAVE_INVITE:
            ptr = find_request(mp);
            if (ptr != NULL) {
                  rp->id_num = htonl(ptr->id_num);
                  rp->answer = SUCCESS;
            } 
            else insert_table(mp, rp);
            break;
        case LOOK_UP:
            ptr = find_match(mp);
            if (ptr != NULL) {
                  rp->id_num = htonl(ptr->id_num);
                  rp->addr = ptr->addr;
                  rp->addr.ta_family = htons(ptr->addr.ta_family);
                  rp->answer = SUCCESS;
            } 
            else rp->answer = NOT_HERE;
            break;
        case DELETE:
            rp->answer = delete_invite(mp->id_num);
            break;
        default:
            rp->answer = UNKNOWN_REQUEST;
            break;
      }
      print_response("process_request", rp);
}


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