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
  60
  61 #include <stdio.h>
  62 #include "cryptlib.h"
  63 #include <openssl/bn.h>
  64 #include <openssl/rand.h>
  65 #include <openssl/dh.h>
  66
  67 static int generate_key(DH *dh);
  68 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
  69 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
  70                         const BIGNUM *a, const BIGNUM *p,
  71                         const BIGNUM *m, BN_CTX *ctx,
  72                         BN_MONT_CTX *m_ctx);
  73 static int dh_init(DH *dh);
  74 static int dh_finish(DH *dh);
  75
  76 int DH_generate_key(DH *dh)
  77         {
  78         return dh->meth->generate_key(dh);
  79         }
  80
  81 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  82         {
  83         return dh->meth->compute_key(key, pub_key, dh);
  84         }
  85
  86 int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  87         {
  88         int rv, pad;
  89         rv = dh->meth->compute_key(key, pub_key, dh);
  90         if (rv <= 0)
  91                 return rv;
  92         pad = BN_num_bytes(dh->p) - rv;
  93         if (pad > 0)
  94                 {
  95                 memmove(key + pad, key, rv);
  96                 memset(key, 0, pad);
  97                 }
  98         return rv + pad;
  99         }
 100
 101 static DH_METHOD dh_ossl = {
 102 "OpenSSL DH Method",
 103 generate_key,
 104 compute_key,
 105 dh_bn_mod_exp,
 106 dh_init,
 107 dh_finish,
 108 DH_FLAG_FIPS_METHOD,
 109 NULL,
 110 NULL
 111 };
 112
 113 const DH_METHOD *DH_OpenSSL(void)
 114 {
 115         return &dh_ossl;
 116 }
 117
 118 static int generate_key(DH *dh)
 119         {
 120         int ok=0;
 121         int generate_new_key=0;
 122         unsigned l;
 123         BN_CTX *ctx;
 124         BN_MONT_CTX *mont=NULL;
 125         BIGNUM *pub_key=NULL,*priv_key=NULL;
 126
 127         ctx = BN_CTX_new();
 128         if (ctx == NULL) goto err;
 129
 130         if (dh->priv_key == NULL)
 131                 {
 132                 priv_key=BN_new();
 133                 if (priv_key == NULL) goto err;
 134                 generate_new_key=1;
 135                 }
 136         else
 137                 priv_key=dh->priv_key;
 138
 139         if (dh->pub_key == NULL)
 140                 {
 141                 pub_key=BN_new();
 142                 if (pub_key == NULL) goto err;
 143                 }
 144         else
 145                 pub_key=dh->pub_key;
 146
 147
 148         if (dh->flags & DH_FLAG_CACHE_MONT_P)
 149                 {
 150                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 151                                 CRYPTO_LOCK_DH, dh->p, ctx);
 152                 if (!mont)
 153                         goto err;
 154                 }
 155
 156         if (generate_new_key)
 157                 {
 158                 if (dh->q)
 159                         {
 160                         do
 161                                 {
 162                                 if (!BN_rand_range(priv_key, dh->q))
 163                                         goto err;
 164                                 }
 165                         while (BN_is_zero(priv_key) || BN_is_one(priv_key));
 166                         }
 167                 else
 168                         {
 169                         /* secret exponent length */
 170                         l = dh->length ? dh->length : BN_num_bits(dh->p)-1;
 171                         if (!BN_rand(priv_key, l, 0, 0)) goto err;
 172                         }
 173                 }
 174
 175         {
 176                 BIGNUM local_prk;
 177                 BIGNUM *prk;
 178
 179                 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
 180                         {
 181                         BN_init(&local_prk);
 182                         prk = &local_prk;
 183                         BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
 184                         }
 185                 else
 186                         prk = priv_key;
 187
 188                 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) goto err;
 189         }
 190
 191         dh->pub_key=pub_key;
 192         dh->priv_key=priv_key;
 193         ok=1;
 194 err:
 195         if (ok != 1)
 196                 DHerr(DH_F_GENERATE_KEY,ERR_R_BN_LIB);
 197
 198         if ((pub_key != NULL)  && (dh->pub_key == NULL))  BN_free(pub_key);
 199         if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
 200         BN_CTX_free(ctx);
 201         return(ok);
 202         }
 203
 204 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 205         {
 206         BN_CTX *ctx=NULL;
 207         BN_MONT_CTX *mont=NULL;
 208         BIGNUM *tmp;
 209         int ret= -1;
 210         int check_result;
 211
 212         if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS)
 213                 {
 214                 DHerr(DH_F_COMPUTE_KEY,DH_R_MODULUS_TOO_LARGE);
 215                 goto err;
 216                 }
 217
 218         ctx = BN_CTX_new();
 219         if (ctx == NULL) goto err;
 220         BN_CTX_start(ctx);
 221         tmp = BN_CTX_get(ctx);
 222
 223         if (dh->priv_key == NULL)
 224                 {
 225                 DHerr(DH_F_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
 226                 goto err;
 227                 }
 228
 229         if (dh->flags & DH_FLAG_CACHE_MONT_P)
 230                 {
 231                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 232                                 CRYPTO_LOCK_DH, dh->p, ctx);
 233                 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
 234                         {
 235                         /* XXX */
 236                         BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
 237                         }
 238                 if (!mont)
 239                         goto err;
 240                 }
 241
 242         if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result)
 243                 {
 244                 DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY);
 245                 goto err;
 246                 }
 247
 248         if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
 249                 {
 250                 DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB);
 251                 goto err;
 252                 }
 253
 254         ret=BN_bn2bin(tmp,key);
 255 err:
 256         if (ctx != NULL)
 257                 {
 258                 BN_CTX_end(ctx);
 259                 BN_CTX_free(ctx);
 260                 }
 261         return(ret);
 262         }
 263
 264 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
 265                         const BIGNUM *a, const BIGNUM *p,
 266                         const BIGNUM *m, BN_CTX *ctx,
 267                         BN_MONT_CTX *m_ctx)
 268         {
 269         /* If a is only one word long and constant time is false, use the faster
 270          * exponenentiation function.
 271          */
 272         if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0))
 273                 {
 274                 BN_ULONG A = a->d[0];
 275                 return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx);
 276                 }
 277         else
 278                 return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx);
 279         }
 280
 281
 282 static int dh_init(DH *dh)
 283         {
 284         dh->flags |= DH_FLAG_CACHE_MONT_P;
 285         return(1);
 286         }
 287
 288 static int dh_finish(DH *dh)
 289         {
 290         if(dh->method_mont_p)
 291                 BN_MONT_CTX_free(dh->method_mont_p);
 292         return(1);
 293         }