2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 #include "internal/cryptlib.h"
13 #include "internal/bn_int.h"
15 static int generate_key(DH *dh);
16 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
17 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
18 const BIGNUM *a, const BIGNUM *p,
19 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
20 static int dh_init(DH *dh);
21 static int dh_finish(DH *dh);
23 int DH_generate_key(DH *dh)
25 return dh->meth->generate_key(dh);
28 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
30 return dh->meth->compute_key(key, pub_key, dh);
33 int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
36 rv = dh->meth->compute_key(key, pub_key, dh);
39 pad = BN_num_bytes(dh->p) - rv;
41 memmove(key + pad, key, rv);
47 static DH_METHOD dh_ossl = {
59 static const DH_METHOD *default_DH_method = &dh_ossl;
61 const DH_METHOD *DH_OpenSSL(void)
66 void DH_set_default_method(const DH_METHOD *meth)
68 default_DH_method = meth;
71 const DH_METHOD *DH_get_default_method(void)
73 return default_DH_method;
76 static int generate_key(DH *dh)
79 int generate_new_key = 0;
82 BN_MONT_CTX *mont = NULL;
83 BIGNUM *pub_key = NULL, *priv_key = NULL;
89 if (dh->priv_key == NULL) {
90 priv_key = BN_secure_new();
95 priv_key = dh->priv_key;
97 if (dh->pub_key == NULL) {
102 pub_key = dh->pub_key;
104 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
105 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
106 dh->lock, dh->p, ctx);
111 if (generate_new_key) {
114 if (!BN_priv_rand_range(priv_key, dh->q))
117 while (BN_is_zero(priv_key) || BN_is_one(priv_key));
119 /* secret exponent length */
120 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
121 if (!BN_priv_rand(priv_key, l, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY))
127 BIGNUM *prk = BN_new();
131 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
133 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) {
137 /* We MUST free prk before any further use of priv_key */
141 dh->pub_key = pub_key;
142 dh->priv_key = priv_key;
146 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
148 if (pub_key != dh->pub_key)
150 if (priv_key != dh->priv_key)
156 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
159 BN_MONT_CTX *mont = NULL;
164 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
165 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
173 tmp = BN_CTX_get(ctx);
177 if (dh->priv_key == NULL) {
178 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
182 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
183 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
184 dh->lock, dh->p, ctx);
185 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
190 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
191 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
196 meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
197 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
201 ret = BN_bn2bin(tmp, key);
210 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
211 const BIGNUM *a, const BIGNUM *p,
212 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
214 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
217 static int dh_init(DH *dh)
219 dh->flags |= DH_FLAG_CACHE_MONT_P;
223 static int dh_finish(DH *dh)
225 BN_MONT_CTX_free(dh->method_mont_p);