2 * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (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 * DH low level APIs are deprecated for public use, but still ok for
14 #include "internal/deprecated.h"
17 #include "internal/cryptlib.h"
19 #include "crypto/bn.h"
20 #include "crypto/dh.h"
22 static int generate_key(DH *dh);
23 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
24 const BIGNUM *a, const BIGNUM *p,
25 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
26 static int dh_init(DH *dh);
27 static int dh_finish(DH *dh);
29 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
32 BN_MONT_CTX *mont = NULL;
39 if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
40 DHerr(0, DH_R_MODULUS_TOO_LARGE);
44 if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
45 DHerr(0, DH_R_MODULUS_TOO_SMALL);
49 ctx = BN_CTX_new_ex(dh->libctx);
53 tmp = BN_CTX_get(ctx);
57 if (dh->priv_key == NULL) {
58 DHerr(0, DH_R_NO_PRIVATE_VALUE);
62 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
63 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
64 dh->lock, dh->params.p, ctx);
65 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
69 /* TODO(3.0) : Solve in a PR related to Key validation for DH */
71 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
72 DHerr(0, DH_R_INVALID_PUBKEY);
76 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->params.p, ctx,
78 DHerr(0, ERR_R_BN_LIB);
82 ret = BN_bn2bin(tmp, key);
89 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
92 return compute_key(key, pub_key, dh);
94 return dh->meth->compute_key(key, pub_key, dh);
98 int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
103 rv = compute_key(key, pub_key, dh);
105 rv = dh->meth->compute_key(key, pub_key, dh);
109 pad = BN_num_bytes(dh->params.p) - rv;
111 memmove(key + pad, key, rv);
117 static DH_METHOD dh_ossl = {
129 static const DH_METHOD *default_DH_method = &dh_ossl;
131 const DH_METHOD *DH_OpenSSL(void)
136 const DH_METHOD *DH_get_default_method(void)
138 return default_DH_method;
141 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
142 const BIGNUM *a, const BIGNUM *p,
143 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
145 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
148 static int dh_init(DH *dh)
150 dh->flags |= DH_FLAG_CACHE_MONT_P;
151 ffc_params_init(&dh->params);
156 static int dh_finish(DH *dh)
158 BN_MONT_CTX_free(dh->method_mont_p);
163 void DH_set_default_method(const DH_METHOD *meth)
165 default_DH_method = meth;
167 #endif /* FIPS_MODE */
169 int DH_generate_key(DH *dh)
172 return generate_key(dh);
174 return dh->meth->generate_key(dh);
178 int dh_generate_public_key(BN_CTX *ctx, DH *dh, const BIGNUM *priv_key,
182 BIGNUM *prk = BN_new();
183 BN_MONT_CTX *mont = NULL;
188 if (dh->flags & DH_FLAG_CACHE_MONT_P) {
189 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
190 dh->lock, dh->params.p, ctx);
194 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
196 /* pub_key = g^priv_key mod p */
197 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->params.g, prk, dh->params.p,
206 static int generate_key(DH *dh)
209 int generate_new_key = 0;
214 BIGNUM *pub_key = NULL, *priv_key = NULL;
216 if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
217 DHerr(0, DH_R_MODULUS_TOO_LARGE);
221 if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
222 DHerr(0, DH_R_MODULUS_TOO_SMALL);
226 ctx = BN_CTX_new_ex(dh->libctx);
230 if (dh->priv_key == NULL) {
231 priv_key = BN_secure_new();
232 if (priv_key == NULL)
234 generate_new_key = 1;
236 priv_key = dh->priv_key;
239 if (dh->pub_key == NULL) {
244 pub_key = dh->pub_key;
246 if (generate_new_key) {
247 /* Is it an approved safe prime ?*/
248 if (DH_get_nid(dh) != NID_undef) {
250 * The safe prime group code sets N = 2*s
251 * (where s = max security strength supported).
252 * N = dh->length (N = maximum bit length of private key)
254 if (dh->params.q == NULL
255 || dh->length > BN_num_bits(dh->params.q))
257 if (!ffc_generate_private_key(ctx, &dh->params, dh->length,
258 dh->length / 2, priv_key))
262 if (dh->params.q == NULL)
265 if (dh->params.q == NULL) {
266 /* secret exponent length */
267 l = dh->length ? dh->length : BN_num_bits(dh->params.p) - 1;
268 if (!BN_priv_rand_ex(priv_key, l, BN_RAND_TOP_ONE,
269 BN_RAND_BOTTOM_ANY, ctx))
272 * We handle just one known case where g is a quadratic non-residue:
273 * for g = 2: p % 8 == 3
275 if (BN_is_word(dh->params.g, DH_GENERATOR_2)
276 && !BN_is_bit_set(dh->params.p, 2)) {
277 /* clear bit 0, since it won't be a secret anyway */
278 if (!BN_clear_bit(priv_key, 0))
285 * For FFC FIPS 186-4 keygen
286 * security strength s = 112,
287 * Max Private key size N = len(q)
289 if (!ffc_generate_private_key(ctx, &dh->params,
290 BN_num_bits(dh->params.q), 112,
297 if (!dh_generate_public_key(ctx, dh, priv_key, pub_key))
300 dh->pub_key = pub_key;
301 dh->priv_key = priv_key;
306 DHerr(0, ERR_R_BN_LIB);
308 if (pub_key != dh->pub_key)
310 if (priv_key != dh->priv_key)
316 int dh_buf2key(DH *dh, const unsigned char *buf, size_t len)
318 int err_reason = DH_R_BN_ERROR;
319 BIGNUM *pubkey = NULL;
323 if ((pubkey = BN_bin2bn(buf, len, NULL)) == NULL)
325 DH_get0_pqg(dh, &p, NULL, NULL);
326 if (p == NULL || (p_size = BN_num_bytes(p)) == 0) {
327 err_reason = DH_R_NO_PARAMETERS_SET;
331 * As per Section 4.2.8.1 of RFC 8446 fail if DHE's
332 * public key is of size not equal to size of p
334 if (BN_is_zero(pubkey) || p_size != len) {
335 err_reason = DH_R_INVALID_PUBKEY;
338 if (DH_set0_key(dh, pubkey, NULL) != 1)
342 DHerr(DH_F_DH_BUF2KEY, err_reason);
347 size_t dh_key2buf(const DH *dh, unsigned char **pbuf_out)
349 const BIGNUM *pubkey;
354 DH_get0_pqg(dh, &p, NULL, NULL);
355 DH_get0_key(dh, &pubkey, NULL);
356 if (p == NULL || pubkey == NULL
357 || (p_size = BN_num_bytes(p)) == 0
358 || BN_num_bytes(pubkey) == 0) {
359 DHerr(DH_F_DH_KEY2BUF, DH_R_INVALID_PUBKEY);
362 if ((pbuf = OPENSSL_malloc(p_size)) == NULL) {
363 DHerr(DH_F_DH_KEY2BUF, ERR_R_MALLOC_FAILURE);
367 * As per Section 4.2.8.1 of RFC 8446 left pad public
368 * key with zeros to the size of p
370 if (BN_bn2binpad(pubkey, pbuf, p_size) < 0) {
372 DHerr(DH_F_DH_KEY2BUF, DH_R_BN_ERROR);