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 #define OPENSSL_FIPSAPI
  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 #ifdef OPENSSL_FIPS
  67 #include <openssl/fips.h>
  68 #endif
  69
  70 static int generate_key(DH *dh);
  71 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
  72 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
  73                         const BIGNUM *a, const BIGNUM *p,
  74                         const BIGNUM *m, BN_CTX *ctx,
  75                         BN_MONT_CTX *m_ctx);
  76 static int dh_init(DH *dh);
  77 static int dh_finish(DH *dh);
  78
  79 int DH_generate_key(DH *dh)
  80         {
  81         return dh->meth->generate_key(dh);
  82         }
  83
  84 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  85         {
  86         return dh->meth->compute_key(key, pub_key, dh);
  87         }
  88
  89 int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  90         {
  91         int rv, pad;
  92         rv = dh->meth->compute_key(key, pub_key, dh);
  93         if (rv <= 0)
  94                 return rv;
  95         pad = BN_num_bytes(dh->p) - rv;
  96         if (pad > 0)
  97                 {
  98                 memmove(key + pad, key, rv);
  99                 memset(key, 0, pad);
 100                 }
 101         return rv + pad;
 102         }
 103
 104 static DH_METHOD dh_ossl = {
 105 "OpenSSL DH Method",
 106 generate_key,
 107 compute_key,
 108 dh_bn_mod_exp,
 109 dh_init,
 110 dh_finish,
 111 0,
 112 NULL,
 113 NULL
 114 };
 115
 116 const DH_METHOD *DH_OpenSSL(void)
 117 {
 118         return &dh_ossl;
 119 }
 120
 121 static int generate_key(DH *dh)
 122         {
 123         int ok=0;
 124         int generate_new_key=0;
 125         unsigned l;
 126         BN_CTX *ctx;
 127         BN_MONT_CTX *mont=NULL;
 128         BIGNUM *pub_key=NULL,*priv_key=NULL;
 129
 130 #ifdef OPENSSL_FIPS
 131         if (FIPS_mode() && (BN_num_bits(dh->p) < OPENSSL_DH_FIPS_MIN_MODULUS_BITS))
 132                 {
 133                 DHerr(DH_F_GENERATE_KEY, DH_R_KEY_SIZE_TOO_SMALL);
 134                 return 0;
 135                 }
 136 #endif
 137
 138         ctx = BN_CTX_new();
 139         if (ctx == NULL) goto err;
 140
 141         if (dh->priv_key == NULL)
 142                 {
 143                 priv_key=BN_new();
 144                 if (priv_key == NULL) goto err;
 145                 generate_new_key=1;
 146                 }
 147         else
 148                 priv_key=dh->priv_key;
 149
 150         if (dh->pub_key == NULL)
 151                 {
 152                 pub_key=BN_new();
 153                 if (pub_key == NULL) goto err;
 154                 }
 155         else
 156                 pub_key=dh->pub_key;
 157
 158
 159         if (dh->flags & DH_FLAG_CACHE_MONT_P)
 160                 {
 161                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 162                                 CRYPTO_LOCK_DH, dh->p, ctx);
 163                 if (!mont)
 164                         goto err;
 165                 }
 166
 167         if (generate_new_key)
 168                 {
 169                 if (dh->q)
 170                         {
 171                         do
 172                                 {
 173                                 if (!BN_rand_range(priv_key, dh->q))
 174                                         goto err;
 175                                 }
 176                         while (BN_is_zero(priv_key) || BN_is_one(priv_key));
 177                         }
 178                 else
 179                         {
 180                         /* secret exponent length */
 181                         l = dh->length ? dh->length : BN_num_bits(dh->p)-1;
 182                         if (!BN_rand(priv_key, l, 0, 0)) goto err;
 183                         }
 184                 }
 185
 186         {
 187                 BIGNUM local_prk;
 188                 BIGNUM *prk;
 189
 190                 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
 191                         {
 192                         BN_init(&local_prk);
 193                         prk = &local_prk;
 194                         BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
 195                         }
 196                 else
 197                         prk = priv_key;
 198
 199                 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) goto err;
 200         }
 201
 202         dh->pub_key=pub_key;
 203         dh->priv_key=priv_key;
 204         ok=1;
 205 err:
 206         if (ok != 1)
 207                 DHerr(DH_F_GENERATE_KEY,ERR_R_BN_LIB);
 208
 209         if ((pub_key != NULL)  && (dh->pub_key == NULL))  BN_free(pub_key);
 210         if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
 211         BN_CTX_free(ctx);
 212         return(ok);
 213         }
 214
 215 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 216         {
 217         BN_CTX *ctx=NULL;
 218         BN_MONT_CTX *mont=NULL;
 219         BIGNUM *tmp;
 220         int ret= -1;
 221         int check_result;
 222
 223         if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS)
 224                 {
 225                 DHerr(DH_F_COMPUTE_KEY,DH_R_MODULUS_TOO_LARGE);
 226                 goto err;
 227                 }
 228
 229 #ifdef OPENSSL_FIPS
 230         if (FIPS_mode() && (BN_num_bits(dh->p) < OPENSSL_DH_FIPS_MIN_MODULUS_BITS))
 231                 {
 232                 DHerr(DH_F_COMPUTE_KEY, DH_R_KEY_SIZE_TOO_SMALL);
 233                 goto err;
 234                 }
 235 #endif
 236
 237         ctx = BN_CTX_new();
 238         if (ctx == NULL) goto err;
 239         BN_CTX_start(ctx);
 240         tmp = BN_CTX_get(ctx);
 241
 242         if (dh->priv_key == NULL)
 243                 {
 244                 DHerr(DH_F_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
 245                 goto err;
 246                 }
 247
 248         if (dh->flags & DH_FLAG_CACHE_MONT_P)
 249                 {
 250                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 251                                 CRYPTO_LOCK_DH, dh->p, ctx);
 252                 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
 253                         {
 254                         /* XXX */
 255                         BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
 256                         }
 257                 if (!mont)
 258                         goto err;
 259                 }
 260
 261         if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result)
 262                 {
 263                 DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY);
 264                 goto err;
 265                 }
 266
 267         if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
 268                 {
 269                 DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB);
 270                 goto err;
 271                 }
 272
 273         ret=BN_bn2bin(tmp,key);
 274 err:
 275         if (ctx != NULL)
 276                 {
 277                 BN_CTX_end(ctx);
 278                 BN_CTX_free(ctx);
 279                 }
 280         return(ret);
 281         }
 282
 283 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
 284                         const BIGNUM *a, const BIGNUM *p,
 285                         const BIGNUM *m, BN_CTX *ctx,
 286                         BN_MONT_CTX *m_ctx)
 287         {
 288         /* If a is only one word long and constant time is false, use the faster
 289          * exponenentiation function.
 290          */
 291         if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0))
 292                 {
 293                 BN_ULONG A = a->d[0];
 294                 return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx);
 295                 }
 296         else
 297                 return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx);
 298         }
 299
 300
 301 static int dh_init(DH *dh)
 302         {
 303 #ifdef OPENSSL_FIPS
 304         FIPS_selftest_check();
 305 #endif
 306         dh->flags |= DH_FLAG_CACHE_MONT_P;
 307         return(1);
 308         }
 309
 310 static int dh_finish(DH *dh)
 311         {
 312         if(dh->method_mont_p)
 313                 BN_MONT_CTX_free(dh->method_mont_p);
 314         return(1);
 315         }