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, const BIGNUM *pub_key, DH *dh);
  67 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
  68                         const BIGNUM *a, const BIGNUM *p,
  69                         const BIGNUM *m, BN_CTX *ctx,
  70                         BN_MONT_CTX *m_ctx);
  71 static int dh_init(DH *dh);
  72 static int dh_finish(DH *dh);
  73
  74 int DH_generate_key(DH *dh)
  75         {
  76         return dh->meth->generate_key(dh);
  77         }
  78
  79 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  80         {
  81         return dh->meth->compute_key(key, pub_key, dh);
  82         }
  83
  84 static DH_METHOD dh_ossl = {
  85 "OpenSSL DH Method",
  86 generate_key,
  87 compute_key,
  88 dh_bn_mod_exp,
  89 dh_init,
  90 dh_finish,
  91 0,
  92 NULL,
  93 NULL
  94 };
  95
  96 const DH_METHOD *DH_OpenSSL(void)
  97 {
  98         return &dh_ossl;
  99 }
 100
 101 static int generate_key(DH *dh)
 102         {
 103         int ok=0;
 104         int generate_new_key=0;
 105         unsigned l;
 106         BN_CTX *ctx;
 107         BN_MONT_CTX *mont=NULL;
 108         BIGNUM *pub_key=NULL,*priv_key=NULL;
 109
 110         ctx = BN_CTX_new();
 111         if (ctx == NULL) goto err;
 112
 113         if (dh->priv_key == NULL)
 114                 {
 115                 priv_key=BN_new();
 116                 if (priv_key == NULL) goto err;
 117                 generate_new_key=1;
 118                 }
 119         else
 120                 priv_key=dh->priv_key;
 121
 122         if (dh->pub_key == NULL)
 123                 {
 124                 pub_key=BN_new();
 125                 if (pub_key == NULL) goto err;
 126                 }
 127         else
 128                 pub_key=dh->pub_key;
 129
 130
 131         if (dh->flags & DH_FLAG_CACHE_MONT_P)
 132                 {
 133                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 134                                 CRYPTO_LOCK_DH, dh->p, ctx);
 135                 if (!mont)
 136                         goto err;
 137                 }
 138
 139         if (generate_new_key)
 140                 {
 141                 l = dh->length ? dh->length : BN_num_bits(dh->p)-1; /* secret exponent length */
 142                 if (!BN_rand(priv_key, l, 0, 0)) goto err;
 143                 }
 144
 145         {
 146                 BIGNUM local_prk;
 147                 BIGNUM *prk;
 148
 149                 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
 150                         {
 151                         BN_init(&local_prk);
 152                         prk = &local_prk;
 153                         BN_with_flags(prk, priv_key, BN_FLG_EXP_CONSTTIME);
 154                         }
 155                 else
 156                         prk = priv_key;
 157
 158                 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) goto err;
 159         }
 160
 161         dh->pub_key=pub_key;
 162         dh->priv_key=priv_key;
 163         ok=1;
 164 err:
 165         if (ok != 1)
 166                 DHerr(DH_F_GENERATE_KEY,ERR_R_BN_LIB);
 167
 168         if ((pub_key != NULL)  && (dh->pub_key == NULL))  BN_free(pub_key);
 169         if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
 170         BN_CTX_free(ctx);
 171         return(ok);
 172         }
 173
 174 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 175         {
 176         BN_CTX *ctx;
 177         BN_MONT_CTX *mont=NULL;
 178         BIGNUM *tmp;
 179         int ret= -1;
 180         int check_result;
 181
 182         if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS)
 183                 {
 184                 DHerr(DH_F_COMPUTE_KEY,DH_R_MODULUS_TOO_LARGE);
 185                 goto err;
 186                 }
 187
 188         ctx = BN_CTX_new();
 189         if (ctx == NULL) goto err;
 190         BN_CTX_start(ctx);
 191         tmp = BN_CTX_get(ctx);
 192
 193         if (dh->priv_key == NULL)
 194                 {
 195                 DHerr(DH_F_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
 196                 goto err;
 197                 }
 198
 199         if (dh->flags & DH_FLAG_CACHE_MONT_P)
 200                 {
 201                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 202                                 CRYPTO_LOCK_DH, dh->p, ctx);
 203                 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
 204                         {
 205                         /* XXX */
 206                         BN_set_flags(dh->priv_key, BN_FLG_EXP_CONSTTIME);
 207                         }
 208                 if (!mont)
 209                         goto err;
 210                 }
 211
 212         if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result)
 213                 {
 214                 DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY);
 215                 goto err;
 216                 }
 217
 218         if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
 219                 {
 220                 DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB);
 221                 goto err;
 222                 }
 223
 224         ret=BN_bn2bin(tmp,key);
 225 err:
 226         if (ctx != NULL)
 227                 {
 228                 BN_CTX_end(ctx);
 229                 BN_CTX_free(ctx);
 230                 }
 231         return(ret);
 232         }
 233
 234 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
 235                         const BIGNUM *a, const BIGNUM *p,
 236                         const BIGNUM *m, BN_CTX *ctx,
 237                         BN_MONT_CTX *m_ctx)
 238         {
 239         /* If a is only one word long and constant time is false, use the faster
 240          * exponenentiation function.
 241          */
 242         if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0))
 243                 {
 244                 BN_ULONG A = a->d[0];
 245                 return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx);
 246                 }
 247         else
 248                 return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx);
 249         }
 250
 251
 252 static int dh_init(DH *dh)
 253         {
 254         dh->flags |= DH_FLAG_CACHE_MONT_P;
 255         return(1);
 256         }
 257
 258 static int dh_finish(DH *dh)
 259         {
 260         if(dh->method_mont_p)
 261                 BN_MONT_CTX_free(dh->method_mont_p);
 262         return(1);
 263         }