dh.c

   1 /* borrowed from isakmpd-20030718 (-; */
   2
   3 /*      $OpenBSD: dh.c,v 1.8 2003/06/03 14:28:16 ho Exp $       */
   4 /*      $EOM: dh.c,v 1.5 1999/04/17 23:20:22 niklas Exp $       */
   5
   6 /*
   7  * Copyright (c) 1998 Niels Provos.  All rights reserved.
   8  * Copyright (c) 1999 Niklas Hallqvist.  All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 /*
  32  * This code was written under funding by Ericsson Radio Systems.
  33  */
  34
  35 #include "math_group.h"
  36 #include "dh.h"
  37
  38 /*
  39  * Returns the length of our exchange value.
  40  */
  41
  42 int dh_getlen(struct group *group)
  43 {
  44         return group->getlen(group);
  45 }
  46
  47 /*
  48  * Creates the exchange value we are offering to the other party.
  49  * Each time this function is called a new value is created, that
  50  * means the application has to save the exchange value itself,
  51  * dh_create_exchange should only be called once.
  52  */
  53 int dh_create_exchange(struct group *group, unsigned char *buf)
  54 {
  55         if (group->setrandom(group, group->c))
  56                 return -1;
  57         if (group->operation(group, group->a, group->gen, group->c))
  58                 return -1;
  59         group->getraw(group, group->a, buf);
  60         return 0;
  61 }
  62
  63 /*
  64  * Creates the Diffie-Hellman shared secret in 'secret', where 'exchange'
  65  * is the exchange value offered by the other party. No length verification
  66  * is done for the value, the application has to do that.
  67  */
  68 int dh_create_shared(struct group *group, unsigned char *secret, unsigned char *exchange)
  69 {
  70         if (group->setraw(group, group->b, exchange, group->getlen(group)))
  71                 return -1;
  72         if (group->operation(group, group->a, group->b, group->c))
  73                 return -1;
  74         group->getraw(group, group->a, secret);
  75         return 0;
  76 }