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 <openssl/bn.h>
  62 #include <openssl/rand.h>
  63 #include <openssl/dh.h>
  64
  65 static int generate_key(DH *dh);
  66 static int compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh);
  67 static int dh_bn_mod_exp(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
  68                         const BIGNUM *m, BN_CTX *ctx,
  69                         BN_MONT_CTX *m_ctx);
  70 static int dh_init(DH *dh);
  71 static int dh_finish(DH *dh);
  72
  73 int DH_generate_key(DH *dh)
  74         {
  75         return dh->meth->generate_key(dh);
  76         }
  77
  78 int DH_compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh)
  79         {
  80         return dh->meth->compute_key(key, pub_key, dh);
  81         }
  82
  83 static DH_METHOD dh_ossl = {
  84 "OpenSSL DH Method",
  85 generate_key,
  86 compute_key,
  87 dh_bn_mod_exp,
  88 dh_init,
  89 dh_finish,
  90 0,
  91 NULL
  92 };
  93
  94 DH_METHOD *DH_OpenSSL(void)
  95 {
  96         return &dh_ossl;
  97 }
  98
  99 static int generate_key(DH *dh)
 100         {
 101         int ok=0;
 102         unsigned int i;
 103         BN_CTX ctx;
 104         BN_MONT_CTX *mont;
 105         BIGNUM *pub_key=NULL,*priv_key=NULL;
 106
 107         BN_CTX_init(&ctx);
 108
 109         if (dh->priv_key == NULL)
 110                 {
 111                 i=dh->length;
 112                 if (i == 0)
 113                         {
 114                         /* Make the number p-1 bits long */
 115                         i=BN_num_bits(dh->p)-1;
 116                         }
 117                 priv_key=BN_new();
 118                 if (priv_key == NULL) goto err;
 119                 if (!BN_rand(priv_key,i,0,0)) goto err;
 120                 }
 121         else
 122                 priv_key=dh->priv_key;
 123
 124         if (dh->pub_key == NULL)
 125                 {
 126                 pub_key=BN_new();
 127                 if (pub_key == NULL) goto err;
 128                 }
 129         else
 130                 pub_key=dh->pub_key;
 131
 132         if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
 133                 {
 134                 if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 135                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
 136                                 dh->p,&ctx)) goto err;
 137                 }
 138         mont=(BN_MONT_CTX *)dh->method_mont_p;
 139
 140         if (!dh->meth->bn_mod_exp(dh, pub_key,dh->g,priv_key,dh->p,&ctx,mont))
 141                                                                 goto err;
 142
 143         dh->pub_key=pub_key;
 144         dh->priv_key=priv_key;
 145         ok=1;
 146 err:
 147         if (ok != 1)
 148                 DHerr(DH_F_DH_GENERATE_KEY,ERR_R_BN_LIB);
 149
 150         if ((pub_key != NULL)  && (dh->pub_key == NULL))  BN_free(pub_key);
 151         if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
 152         BN_CTX_free(&ctx);
 153         return(ok);
 154         }
 155
 156 static int compute_key(unsigned char *key, BIGNUM *pub_key, DH *dh)
 157         {
 158         BN_CTX ctx;
 159         BN_MONT_CTX *mont;
 160         BIGNUM *tmp;
 161         int ret= -1;
 162
 163         BN_CTX_init(&ctx);
 164         tmp= &(ctx.bn[ctx.tos++]);
 165
 166         if (dh->priv_key == NULL)
 167                 {
 168                 DHerr(DH_F_DH_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
 169                 goto err;
 170                 }
 171         if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
 172                 {
 173                 if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 174                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
 175                                 dh->p,&ctx)) goto err;
 176                 }
 177
 178         mont=(BN_MONT_CTX *)dh->method_mont_p;
 179         if (!dh->meth->bn_mod_exp(dh, tmp,pub_key,dh->priv_key,dh->p,&ctx,mont))
 180                 {
 181                 DHerr(DH_F_DH_COMPUTE_KEY,ERR_R_BN_LIB);
 182                 goto err;
 183                 }
 184
 185         ret=BN_bn2bin(tmp,key);
 186 err:
 187         BN_CTX_free(&ctx);
 188         return(ret);
 189         }
 190
 191 static int dh_bn_mod_exp(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
 192                         const BIGNUM *m, BN_CTX *ctx,
 193                         BN_MONT_CTX *m_ctx)
 194 {
 195         return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
 196 }
 197
 198 static int dh_init(DH *dh)
 199 {
 200         dh->flags |= DH_FLAG_CACHE_MONT_P;
 201         return(1);
 202 }
 203
 204 static int dh_finish(DH *dh)
 205 {
 206         if(dh->method_mont_p)
 207                 BN_MONT_CTX_free((BN_MONT_CTX *)dh->method_mont_p);
 208         return(1);
 209 }