crypto/dh/dh_key.c

   1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   2  * All rights reserved.
   3  *
   4  * This package is an SSL implementation written
   5  * by Eric Young (eay@cryptsoft.com).
   6  * The implementation was written so as to conform with Netscapes SSL.
   7  *
   8  * This library is free for commercial and non-commercial use as long as
   9  * the following conditions are aheared to.  The following conditions
  10  * apply to all code found in this distribution, be it the RC4, RSA,
  11  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  12  * included with this distribution is covered by the same copyright terms
  13  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  14  *
  15  * Copyright remains Eric Young's, and as such any Copyright notices in
  16  * the code are not to be removed.
  17  * If this package is used in a product, Eric Young should be given attribution
  18  * as the author of the parts of the library used.
  19  * This can be in the form of a textual message at program startup or
  20  * in documentation (online or textual) provided with the package.
  21  *
  22  * Redistribution and use in source and binary forms, with or without
  23  * modification, are permitted provided that the following conditions
  24  * are met:
  25  * 1. Redistributions of source code must retain the copyright
  26  *    notice, this list of conditions and the following disclaimer.
  27  * 2. Redistributions in binary form must reproduce the above copyright
  28  *    notice, this list of conditions and the following disclaimer in the
  29  *    documentation and/or other materials provided with the distribution.
  30  * 3. All advertising materials mentioning features or use of this software
  31  *    must display the following acknowledgement:
  32  *    "This product includes cryptographic software written by
  33  *     Eric Young (eay@cryptsoft.com)"
  34  *    The word 'cryptographic' can be left out if the rouines from the library
  35  *    being used are not cryptographic related :-).
  36  * 4. If you include any Windows specific code (or a derivative thereof) from
  37  *    the apps directory (application code) you must include an acknowledgement:
  38  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  39  *
  40  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  41  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  43  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  44  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  45  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  46  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  48  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  49  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  50  * SUCH DAMAGE.
  51  *
  52  * The licence and distribution terms for any publically available version or
  53  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  54  * copied and put under another distribution licence
  55  * [including the GNU Public Licence.]
  56  */
  57
  58 #include <stdio.h>
  59 #include "internal/cryptlib.h"
  60 #include <openssl/rand.h>
  61 #include <openssl/dh.h>
  62 #include "internal/bn_int.h"
  63
  64 static int generate_key(DH *dh);
  65 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
  66 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
  67                          const BIGNUM *a, const BIGNUM *p,
  68                          const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
  69 static int dh_init(DH *dh);
  70 static int dh_finish(DH *dh);
  71
  72 int DH_generate_key(DH *dh)
  73 {
  74     return dh->meth->generate_key(dh);
  75 }
  76
  77 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  78 {
  79     return dh->meth->compute_key(key, pub_key, dh);
  80 }
  81
  82 int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
  83 {
  84     int rv, pad;
  85     rv = dh->meth->compute_key(key, pub_key, dh);
  86     if (rv <= 0)
  87         return rv;
  88     pad = BN_num_bytes(dh->p) - rv;
  89     if (pad > 0) {
  90         memmove(key + pad, key, rv);
  91         memset(key, 0, pad);
  92     }
  93     return rv + pad;
  94 }
  95
  96 static DH_METHOD dh_ossl = {
  97     "OpenSSL DH Method",
  98     generate_key,
  99     compute_key,
 100     dh_bn_mod_exp,
 101     dh_init,
 102     dh_finish,
 103     DH_FLAG_FIPS_METHOD,
 104     NULL,
 105     NULL
 106 };
 107
 108 const DH_METHOD *DH_OpenSSL(void)
 109 {
 110     return &dh_ossl;
 111 }
 112
 113 static int generate_key(DH *dh)
 114 {
 115     int ok = 0;
 116     int generate_new_key = 0;
 117     unsigned l;
 118     BN_CTX *ctx;
 119     BN_MONT_CTX *mont = NULL;
 120     BIGNUM *pub_key = NULL, *priv_key = NULL;
 121
 122     ctx = BN_CTX_new();
 123     if (ctx == NULL)
 124         goto err;
 125
 126     if (dh->priv_key == NULL) {
 127         priv_key = BN_secure_new();
 128         if (priv_key == NULL)
 129             goto err;
 130         generate_new_key = 1;
 131     } else
 132         priv_key = dh->priv_key;
 133
 134     if (dh->pub_key == NULL) {
 135         pub_key = BN_new();
 136         if (pub_key == NULL)
 137             goto err;
 138     } else
 139         pub_key = dh->pub_key;
 140
 141     if (dh->flags & DH_FLAG_CACHE_MONT_P) {
 142         mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 143                                       CRYPTO_LOCK_DH, dh->p, ctx);
 144         if (!mont)
 145             goto err;
 146     }
 147
 148     if (generate_new_key) {
 149         if (dh->q) {
 150             do {
 151                 if (!BN_rand_range(priv_key, dh->q))
 152                     goto err;
 153             }
 154             while (BN_is_zero(priv_key) || BN_is_one(priv_key));
 155         } else {
 156             /* secret exponent length */
 157             l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
 158             if (!BN_rand(priv_key, l, 0, 0))
 159                 goto err;
 160         }
 161     }
 162
 163     {
 164         BIGNUM *local_prk = NULL;
 165         BIGNUM *prk;
 166
 167         if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
 168             local_prk = prk = BN_new();
 169             if (local_prk == NULL)
 170                 goto err;
 171             BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
 172         } else {
 173             prk = priv_key;
 174         }
 175
 176         if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) {
 177             BN_free(local_prk);
 178             goto err;
 179         }
 180         /* We MUST free local_prk before any further use of priv_key */
 181         BN_free(local_prk);
 182     }
 183
 184     dh->pub_key = pub_key;
 185     dh->priv_key = priv_key;
 186     ok = 1;
 187  err:
 188     if (ok != 1)
 189         DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
 190
 191     if (pub_key != dh->pub_key)
 192         BN_free(pub_key);
 193     if (priv_key != dh->priv_key)
 194         BN_free(priv_key);
 195     BN_CTX_free(ctx);
 196     return (ok);
 197 }
 198
 199 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 200 {
 201     BN_CTX *ctx = NULL;
 202     BN_MONT_CTX *mont = NULL;
 203     BIGNUM *tmp;
 204     int ret = -1;
 205     int check_result;
 206
 207     if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
 208         DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
 209         goto err;
 210     }
 211
 212     ctx = BN_CTX_new();
 213     if (ctx == NULL)
 214         goto err;
 215     BN_CTX_start(ctx);
 216     tmp = BN_CTX_get(ctx);
 217
 218     if (dh->priv_key == NULL) {
 219         DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
 220         goto err;
 221     }
 222
 223     if (dh->flags & DH_FLAG_CACHE_MONT_P) {
 224         mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
 225                                       CRYPTO_LOCK_DH, dh->p, ctx);
 226         if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
 227             /* XXX */
 228             BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
 229         }
 230         if (!mont)
 231             goto err;
 232     }
 233
 234     if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
 235         DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
 236         goto err;
 237     }
 238
 239     if (!dh->
 240         meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
 241         DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
 242         goto err;
 243     }
 244
 245     ret = BN_bn2bin(tmp, key);
 246  err:
 247     if (ctx != NULL) {
 248         BN_CTX_end(ctx);
 249         BN_CTX_free(ctx);
 250     }
 251     return (ret);
 252 }
 253
 254 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
 255                          const BIGNUM *a, const BIGNUM *p,
 256                          const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
 257 {
 258     /*
 259      * If a is only one word long and constant time is false, use the faster
 260      * exponentiation function.
 261      */
 262     if (bn_get_top(a) == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) {
 263         BN_ULONG A = bn_get_words(a)[0];
 264         return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx);
 265     } else
 266         return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
 267 }
 268
 269 static int dh_init(DH *dh)
 270 {
 271     dh->flags |= DH_FLAG_CACHE_MONT_P;
 272     return (1);
 273 }
 274
 275 static int dh_finish(DH *dh)
 276 {
 277     BN_MONT_CTX_free(dh->method_mont_p);
 278     return (1);
 279 }