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"
12 #include <openssl/rand.h>
14 #include "internal/bn_int.h"
16 static int generate_key(DH *dh);
17 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
18 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
19 const BIGNUM *a, const BIGNUM *p,
20 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
21 static int dh_init(DH *dh);
22 static int dh_finish(DH *dh);
24 int DH_generate_key(DH *dh)
26 return dh->meth->generate_key(dh);
29 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
31 return dh->meth->compute_key(key, pub_key, dh);
34 int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
37 rv = dh->meth->compute_key(key, pub_key, dh);
40 pad = BN_num_bytes(dh->p) - rv;
42 memmove(key + pad, key, rv);
48 static DH_METHOD dh_ossl = {
60 const DH_METHOD *DH_OpenSSL(void)
65 static int generate_key(DH *dh)
68 int generate_new_key = 0;
71 BN_MONT_CTX *mont = NULL;
72 BIGNUM *pub_key = NULL, *priv_key = NULL;
78 if (dh->priv_key == NULL) {
79 priv_key = BN_secure_new();
84 priv_key = dh->priv_key;
86 if (dh->pub_key == NULL) {
91 pub_key = dh->pub_key;
93 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
94 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
95 dh->lock, dh->p, ctx);
100 if (generate_new_key) {
103 if (!BN_rand_range(priv_key, dh->q))
106 while (BN_is_zero(priv_key) || BN_is_one(priv_key));
108 /* secret exponent length */
109 l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
110 if (!BN_rand(priv_key, l, 0, 0))
116 BIGNUM *local_prk = NULL;
119 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
120 local_prk = prk = BN_new();
121 if (local_prk == NULL)
123 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
128 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) {
132 /* We MUST free local_prk before any further use of priv_key */
136 dh->pub_key = pub_key;
137 dh->priv_key = priv_key;
141 DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
143 if (pub_key != dh->pub_key)
145 if (priv_key != dh->priv_key)
151 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
154 BN_MONT_CTX *mont = NULL;
159 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
160 DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
168 tmp = BN_CTX_get(ctx);
170 if (dh->priv_key == NULL) {
171 DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
175 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
176 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
177 dh->lock, dh->p, ctx);
178 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
180 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
186 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
187 DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
192 meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
193 DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
197 ret = BN_bn2bin(tmp, key);
206 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
207 const BIGNUM *a, const BIGNUM *p,
208 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
211 * If a is only one word long and constant time is false, use the faster
212 * exponentiation function.
214 if (bn_get_top(a) == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) {
215 BN_ULONG A = bn_get_words(a)[0];
216 return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx);
218 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
221 static int dh_init(DH *dh)
223 dh->flags |= DH_FLAG_CACHE_MONT_P;
227 static int dh_finish(DH *dh)
229 BN_MONT_CTX_free(dh->method_mont_p);