crypto/dh/dh_key.c

   1 /* crypto/dh/dh_key.c */
   2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   3  * All rights reserved.
   4  *
   5  * This package is an SSL implementation written
   6  * by Eric Young (eay@cryptsoft.com).
   7  * The implementation was written so as to conform with Netscapes SSL.
   8  *
   9  * This library is free for commercial and non-commercial use as long as
  10  * the following conditions are aheared to.  The following conditions
  11  * apply to all code found in this distribution, be it the RC4, RSA,
  12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  13  * included with this distribution is covered by the same copyright terms
  14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  15  *
  16  * Copyright remains Eric Young's, and as such any Copyright notices in
  17  * the code are not to be removed.
  18  * If this package is used in a product, Eric Young should be given attribution
  19  * as the author of the parts of the library used.
  20  * This can be in the form of a textual message at program startup or
  21  * in documentation (online or textual) provided with the package.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 3. All advertising materials mentioning features or use of this software
  32  *    must display the following acknowledgement:
  33  *    "This product includes cryptographic software written by
  34  *     Eric Young (eay@cryptsoft.com)"
  35  *    The word 'cryptographic' can be left out if the rouines from the library
  36  *    being used are not cryptographic related :-).
  37  * 4. If you include any Windows specific code (or a derivative thereof) from
  38  *    the apps directory (application code) you must include an acknowledgement:
  39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  * The licence and distribution terms for any publically available version or
  54  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  55  * copied and put under another distribution licence
  56  * [including the GNU Public Licence.]
  57  */
  58
  59 #include <stdio.h>
  60 #include "cryptlib.h"
  61 #include "bn.h"
  62 #include "rand.h"
  63 #include "dh.h"
  64
  65 int DH_generate_key(dh)
  66 DH *dh;
  67         {
  68         int ok=0;
  69         unsigned int i;
  70         BN_CTX ctx;
  71         BN_MONT_CTX *mont;
  72         BIGNUM *pub_key=NULL,*priv_key=NULL;
  73
  74         BN_CTX_init(&ctx);
  75
  76         if (dh->priv_key == NULL)
  77                 {
  78                 i=dh->length;
  79                 if (i == 0)
  80                         {
  81                         /* Make the number p-1 bits long */
  82                         i=BN_num_bits(dh->p)-1;
  83                         }
  84                 priv_key=BN_new();
  85                 if (priv_key == NULL) goto err;
  86                 if (!BN_rand(priv_key,i,0,0)) goto err;
  87                 }
  88         else
  89                 priv_key=dh->priv_key;
  90
  91         if (dh->pub_key == NULL)
  92                 {
  93                 pub_key=BN_new();
  94                 if (pub_key == NULL) goto err;
  95                 }
  96         else
  97                 pub_key=dh->pub_key;
  98
  99         if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
 100                 {
 101                 if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 102                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
 103                                 dh->p,&ctx)) goto err;
 104                 }
 105         mont=(BN_MONT_CTX *)dh->method_mont_p;
 106
 107         if (!BN_mod_exp_mont(pub_key,dh->g,priv_key,dh->p,&ctx,mont)) goto err;
 108
 109         dh->pub_key=pub_key;
 110         dh->priv_key=priv_key;
 111         ok=1;
 112 err:
 113         if (ok != 1)
 114                 DHerr(DH_F_DH_GENERATE_KEY,ERR_R_BN_LIB);
 115
 116         if ((pub_key != NULL)  && (dh->pub_key == NULL))  BN_free(pub_key);
 117         if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
 118         BN_CTX_free(&ctx);
 119         return(ok);
 120         }
 121
 122 int DH_compute_key(key,pub_key,dh)
 123 unsigned char *key;
 124 BIGNUM *pub_key;
 125 DH *dh;
 126         {
 127         BN_CTX ctx;
 128         BN_MONT_CTX *mont;
 129         BIGNUM *tmp;
 130         int ret= -1;
 131
 132         BN_CTX_init(&ctx);
 133         tmp= &(ctx.bn[ctx.tos++]);
 134
 135         if (dh->priv_key == NULL)
 136                 {
 137                 DHerr(DH_F_DH_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
 138                 goto err;
 139                 }
 140         if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
 141                 {
 142                 if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 143                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
 144                                 dh->p,&ctx)) goto err;
 145                 }
 146
 147         mont=(BN_MONT_CTX *)dh->method_mont_p;
 148         if (!BN_mod_exp_mont(tmp,pub_key,dh->priv_key,dh->p,&ctx,mont))
 149                 {
 150                 DHerr(DH_F_DH_COMPUTE_KEY,ERR_R_BN_LIB);
 151                 goto err;
 152                 }
 153
 154         ret=BN_bn2bin(tmp,key);
 155 err:
 156         BN_CTX_free(&ctx);
 157         return(ret);
 158         }