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 #ifndef OPENSSL_NO_ENGINE
  65 #include <openssl/engine.h>
  66 #endif
  67
  68 static int generate_key(DH *dh);
  69 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
  70 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
  71                         const BIGNUM *a, const BIGNUM *p,
  72                         const BIGNUM *m, BN_CTX *ctx,
  73                         BN_MONT_CTX *m_ctx);
  74 static int dh_init(DH *dh);
  75 static int dh_finish(DH *dh);
  76
  77 int DH_generate_key(DH *dh)
  78         {
  79         return dh->meth->generate_key(dh);
  80         }
  81
  82 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  83         {
  84         return dh->meth->compute_key(key, pub_key, dh);
  85         }
  86
  87 static DH_METHOD dh_ossl = {
  88 "OpenSSL DH Method",
  89 generate_key,
  90 compute_key,
  91 dh_bn_mod_exp,
  92 dh_init,
  93 dh_finish,
  94 0,
  95 NULL,
  96 NULL
  97 };
  98
  99 const DH_METHOD *DH_OpenSSL(void)
 100 {
 101         return &dh_ossl;
 102 }
 103
 104 static int generate_key(DH *dh)
 105         {
 106         int ok=0;
 107         int generate_new_key=0;
 108         unsigned l;
 109         BN_CTX *ctx;
 110         BN_MONT_CTX *mont;
 111         BIGNUM *pub_key=NULL,*priv_key=NULL;
 112
 113         ctx = BN_CTX_new();
 114         if (ctx == NULL) goto err;
 115
 116         if (dh->priv_key == NULL)
 117                 {
 118                 priv_key=BN_new();
 119                 if (priv_key == NULL) goto err;
 120                 generate_new_key=1;
 121                 }
 122         else
 123                 priv_key=dh->priv_key;
 124
 125         if (dh->pub_key == NULL)
 126                 {
 127                 pub_key=BN_new();
 128                 if (pub_key == NULL) goto err;
 129                 }
 130         else
 131                 pub_key=dh->pub_key;
 132
 133         if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
 134                 {
 135                 if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 136                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
 137                                 dh->p,ctx)) goto err;
 138                 }
 139         mont=(BN_MONT_CTX *)dh->method_mont_p;
 140
 141         if (generate_new_key)
 142                 {
 143                 l = dh->length ? dh->length : BN_num_bits(dh->p)-1; /* secret exponent length */
 144                 if (!BN_rand(priv_key, l, 0, 0)) goto err;
 145                 }
 146         if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, priv_key,dh->p,ctx,mont))
 147                 goto err;
 148
 149         dh->pub_key=pub_key;
 150         dh->priv_key=priv_key;
 151         ok=1;
 152 err:
 153         if (ok != 1)
 154                 DHerr(DH_F_DH_GENERATE_KEY,ERR_R_BN_LIB);
 155
 156         if ((pub_key != NULL)  && (dh->pub_key == NULL))  BN_free(pub_key);
 157         if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
 158         BN_CTX_free(ctx);
 159         return(ok);
 160         }
 161
 162 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 163         {
 164         BN_CTX *ctx;
 165         BN_MONT_CTX *mont;
 166         BIGNUM *tmp;
 167         int ret= -1;
 168
 169         ctx = BN_CTX_new();
 170         if (ctx == NULL) goto err;
 171         BN_CTX_start(ctx);
 172         tmp = BN_CTX_get(ctx);
 173
 174         if (dh->priv_key == NULL)
 175                 {
 176                 DHerr(DH_F_DH_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
 177                 goto err;
 178                 }
 179         if ((dh->method_mont_p == NULL) && (dh->flags & DH_FLAG_CACHE_MONT_P))
 180                 {
 181                 if ((dh->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 182                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dh->method_mont_p,
 183                                 dh->p,ctx)) goto err;
 184                 }
 185
 186         mont=(BN_MONT_CTX *)dh->method_mont_p;
 187         if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
 188                 {
 189                 DHerr(DH_F_DH_COMPUTE_KEY,ERR_R_BN_LIB);
 190                 goto err;
 191                 }
 192
 193         ret=BN_bn2bin(tmp,key);
 194 err:
 195         BN_CTX_end(ctx);
 196         BN_CTX_free(ctx);
 197         return(ret);
 198         }
 199
 200 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
 201                         const BIGNUM *a, const BIGNUM *p,
 202                         const BIGNUM *m, BN_CTX *ctx,
 203                         BN_MONT_CTX *m_ctx)
 204         {
 205         if (a->top == 1)
 206                 {
 207                 BN_ULONG A = a->d[0];
 208                 return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx);
 209                 }
 210         else
 211                 return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx);
 212         }
 213
 214
 215 static int dh_init(DH *dh)
 216         {
 217         dh->flags |= DH_FLAG_CACHE_MONT_P;
 218         return(1);
 219         }
 220
 221 static int dh_finish(DH *dh)
 222         {
 223         if(dh->method_mont_p)
 224                 BN_MONT_CTX_free((BN_MONT_CTX *)dh->method_mont_p);
 225         return(1);
 226         }