lib/libcrypto/dh/dh_key.c

   1 /* $OpenBSD: dh_key.c,v 1.27.2.1 2018/06/13 15:13:30 jsing Exp $ */
   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
  61 #include <openssl/bn.h>
  62 #include <openssl/dh.h>
  63 #include <openssl/err.h>
  64
  65 #include "bn_lcl.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, const BIGNUM *a,
  70             const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
  71 static int dh_init(DH *dh);
  72 static int dh_finish(DH *dh);
  73
  74 int
  75 DH_generate_key(DH *dh)
  76 {
  77         return dh->meth->generate_key(dh);
  78 }
  79
  80 int
  81 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 static DH_METHOD dh_ossl = {
  87         .name = "OpenSSL DH Method",
  88         .generate_key = generate_key,
  89         .compute_key = compute_key,
  90         .bn_mod_exp = dh_bn_mod_exp,
  91         .init = dh_init,
  92         .finish = dh_finish,
  93 };
  94
  95 const DH_METHOD *
  96 DH_OpenSSL(void)
  97 {
  98         return &dh_ossl;
  99 }
 100
 101 static int
 102 generate_key(DH *dh)
 103 {
 104         int ok = 0;
 105         int generate_new_key = 0;
 106         unsigned l;
 107         BN_CTX *ctx;
 108         BN_MONT_CTX *mont = NULL;
 109         BIGNUM *pub_key = NULL, *priv_key = NULL;
 110
 111         if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
 112                 DHerror(DH_R_MODULUS_TOO_LARGE);
 113                 return 0;
 114         }
 115
 116         ctx = BN_CTX_new();
 117         if (ctx == NULL)
 118                 goto err;
 119
 120         if (dh->priv_key == NULL) {
 121                 priv_key = BN_new();
 122                 if (priv_key == NULL)
 123                         goto err;
 124                 generate_new_key = 1;
 125         } else
 126                 priv_key = dh->priv_key;
 127
 128         if (dh->pub_key == NULL) {
 129                 pub_key = BN_new();
 130                 if (pub_key == NULL)
 131                         goto err;
 132         } else
 133                 pub_key = dh->pub_key;
 134
 135         if (dh->flags & DH_FLAG_CACHE_MONT_P) {
 136                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 137                     CRYPTO_LOCK_DH, dh->p, ctx);
 138                 if (!mont)
 139                         goto err;
 140         }
 141
 142         if (generate_new_key) {
 143                 if (dh->q) {
 144                         do {
 145                                 if (!BN_rand_range(priv_key, dh->q))
 146                                         goto err;
 147                         } while (BN_is_zero(priv_key) || BN_is_one(priv_key));
 148                 } else {
 149                         /* secret exponent length */
 150                         l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
 151                         if (!BN_rand(priv_key, l, 0, 0))
 152                                 goto err;
 153                 }
 154         }
 155
 156         {
 157                 BIGNUM prk;
 158
 159                 BN_init(&prk);
 160                 BN_with_flags(&prk, priv_key, BN_FLG_CONSTTIME);
 161
 162                 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, &prk, dh->p, ctx,
 163                     mont)) {
 164                         goto err;
 165                 }
 166         }
 167
 168         dh->pub_key = pub_key;
 169         dh->priv_key = priv_key;
 170         ok = 1;
 171 err:
 172         if (ok != 1)
 173                 DHerror(ERR_R_BN_LIB);
 174
 175         if (pub_key != NULL && dh->pub_key == NULL)
 176                 BN_free(pub_key);
 177         if (priv_key != NULL && dh->priv_key == NULL)
 178                 BN_free(priv_key);
 179         BN_CTX_free(ctx);
 180         return ok;
 181 }
 182
 183 static int
 184 compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 185 {
 186         BN_CTX *ctx = NULL;
 187         BN_MONT_CTX *mont = NULL;
 188         BIGNUM *tmp;
 189         int ret = -1;
 190         int check_result;
 191
 192         if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
 193                 DHerror(DH_R_MODULUS_TOO_LARGE);
 194                 goto err;
 195         }
 196
 197         ctx = BN_CTX_new();
 198         if (ctx == NULL)
 199                 goto err;
 200         BN_CTX_start(ctx);
 201         if ((tmp = BN_CTX_get(ctx)) == NULL)
 202                 goto err;
 203
 204         if (dh->priv_key == NULL) {
 205                 DHerror(DH_R_NO_PRIVATE_VALUE);
 206                 goto err;
 207         }
 208
 209         if (dh->flags & DH_FLAG_CACHE_MONT_P) {
 210                 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 211                     CRYPTO_LOCK_DH, dh->p, ctx);
 212
 213                 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
 214
 215                 if (!mont)
 216                         goto err;
 217         }
 218
 219         if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
 220                 DHerror(DH_R_INVALID_PUBKEY);
 221                 goto err;
 222         }
 223
 224         if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx,
 225             mont)) {
 226                 DHerror(ERR_R_BN_LIB);
 227                 goto err;
 228         }
 229
 230         ret = BN_bn2bin(tmp, key);
 231 err:
 232         if (ctx != NULL) {
 233                 BN_CTX_end(ctx);
 234                 BN_CTX_free(ctx);
 235         }
 236         return ret;
 237 }
 238
 239 static int
 240 dh_bn_mod_exp(const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 241     const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
 242 {
 243         return BN_mod_exp_mont_ct(r, a, p, m, ctx, m_ctx);
 244 }
 245
 246 static int
 247 dh_init(DH *dh)
 248 {
 249         dh->flags |= DH_FLAG_CACHE_MONT_P;
 250         return 1;
 251 }
 252
 253 static int
 254 dh_finish(DH *dh)
 255 {
 256         BN_MONT_CTX_free(dh->method_mont_p);
 257         return 1;
 258 }