1 /* crypto/dh/dh_key.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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.
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).
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.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
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)"
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
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.]
61 #include <openssl/rand.h>
62 #include <openssl/dh.h>
63 #include "internal/bn_int.h"
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, BN_MONT_CTX *m_ctx);
70 static int dh_init(DH *dh);
71 static int dh_finish(DH *dh);
73 int DH_generate_key(DH *dh)
75 return dh->meth->generate_key(dh);
78 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
80 return dh->meth->compute_key(key, pub_key, dh);
83 int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
86 rv = dh->meth->compute_key(key, pub_key, dh);
89 pad = BN_num_bytes(dh->p) - rv;
91 memmove(key + pad, key, rv);
97 static DH_METHOD dh_ossl = {
109 const DH_METHOD *DH_OpenSSL(void)
114 static int generate_key(DH *dh)
117 int generate_new_key = 0;
120 BN_MONT_CTX *mont = NULL;
121 BIGNUM *pub_key = NULL, *priv_key = NULL;
127 if (dh->priv_key == NULL) {
129 if (priv_key == NULL)
131 generate_new_key = 1;
133 priv_key = dh->priv_key;
135 if (dh->pub_key == NULL) {
140 pub_key = dh->pub_key;
142 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
143 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
144 CRYPTO_LOCK_DH, dh->p, ctx);
149 if (generate_new_key) {
152 if (!BN_rand_range(priv_key, dh->q))
155 while (BN_is_zero(priv_key) || BN_is_one(priv_key));
157 /* secret exponent length */
158 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
159 if (!BN_rand(priv_key, l, 0, 0))
165 BIGNUM *local_prk = NULL;
168 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
169 local_prk = prk = BN_new();
170 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
174 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) {
183 dh->pub_key = pub_key;
184 dh->priv_key = priv_key;
188 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
190 if ((pub_key != NULL) && (dh->pub_key == NULL))
192 if ((priv_key != NULL) && (dh->priv_key == NULL))
198 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
201 BN_MONT_CTX *mont = NULL;
206 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
207 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
215 tmp = BN_CTX_get(ctx);
217 if (dh->priv_key == NULL) {
218 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
222 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
223 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
224 CRYPTO_LOCK_DH, dh->p, ctx);
225 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
227 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
233 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
234 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
239 meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
240 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
244 ret = BN_bn2bin(tmp, key);
253 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
254 const BIGNUM *a, const BIGNUM *p,
255 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
258 * If a is only one word long and constant time is false, use the faster
259 * exponenentiation function.
261 if (bn_get_top(a) == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) {
262 BN_ULONG A = bn_get_words(a)[0];
263 return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx);
265 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
268 static int dh_init(DH *dh)
270 dh->flags |= DH_FLAG_CACHE_MONT_P;
274 static int dh_finish(DH *dh)
276 if (dh->method_mont_p)
277 BN_MONT_CTX_free(dh->method_mont_p);