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/*
* Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdio.h>
#include "internal/cryptlib.h"
#include "dh_local.h"
#include "crypto/bn.h"
static int generate_key(DH *dh);
static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
static int dh_init(DH *dh);
static int dh_finish(DH *dh);
int DH_generate_key(DH *dh)
{
return dh->meth->generate_key(dh);
}
int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
return dh->meth->compute_key(key, pub_key, dh);
}
int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
int rv, pad;
rv = dh->meth->compute_key(key, pub_key, dh);
if (rv <= 0)
return rv;
pad = BN_num_bytes(dh->p) - rv;
if (pad > 0) {
memmove(key + pad, key, rv);
memset(key, 0, pad);
}
return rv + pad;
}
static DH_METHOD dh_ossl = {
"OpenSSL DH Method",
generate_key,
compute_key,
dh_bn_mod_exp,
dh_init,
dh_finish,
DH_FLAG_FIPS_METHOD,
NULL,
NULL
};
static const DH_METHOD *default_DH_method = &dh_ossl;
const DH_METHOD *DH_OpenSSL(void)
{
return &dh_ossl;
}
void DH_set_default_method(const DH_METHOD *meth)
{
default_DH_method = meth;
}
const DH_METHOD *DH_get_default_method(void)
{
return default_DH_method;
}
static int generate_key(DH *dh)
{
int ok = 0;
int generate_new_key = 0;
unsigned l;
BN_CTX *ctx = NULL;
BN_MONT_CTX *mont = NULL;
BIGNUM *pub_key = NULL, *priv_key = NULL;
if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
DHerr(DH_F_GENERATE_KEY, DH_R_MODULUS_TOO_LARGE);
return 0;
}
ctx = BN_CTX_new();
if (ctx == NULL)
goto err;
if (dh->priv_key == NULL) {
priv_key = BN_secure_new();
if (priv_key == NULL)
goto err;
generate_new_key = 1;
} else
priv_key = dh->priv_key;
if (dh->pub_key == NULL) {
pub_key = BN_new();
if (pub_key == NULL)
goto err;
} else
pub_key = dh->pub_key;
if (dh->flags & DH_FLAG_CACHE_MONT_P) {
mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
dh->lock, dh->p, ctx);
if (!mont)
goto err;
}
if (generate_new_key) {
if (dh->q) {
do {
if (!BN_priv_rand_range(priv_key, dh->q))
goto err;
}
while (BN_is_zero(priv_key) || BN_is_one(priv_key));
} else {
/* secret exponent length */
l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
if (!BN_priv_rand(priv_key, l, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY))
goto err;
/*
* We handle just one known case where g is a quadratic non-residue:
* for g = 2: p % 8 == 3
*/
if (BN_is_word(dh->g, DH_GENERATOR_2) && !BN_is_bit_set(dh->p, 2)) {
/* clear bit 0, since it won't be a secret anyway */
if (!BN_clear_bit(priv_key, 0))
goto err;
}
}
}
{
BIGNUM *prk = BN_new();
if (prk == NULL)
goto err;
BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) {
BN_clear_free(prk);
goto err;
}
/* We MUST free prk before any further use of priv_key */
BN_clear_free(prk);
}
dh->pub_key = pub_key;
dh->priv_key = priv_key;
ok = 1;
err:
if (ok != 1)
DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
if (pub_key != dh->pub_key)
BN_free(pub_key);
if (priv_key != dh->priv_key)
BN_free(priv_key);
BN_CTX_free(ctx);
return ok;
}
static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
BN_CTX *ctx = NULL;
BN_MONT_CTX *mont = NULL;
BIGNUM *tmp;
int ret = -1;
int check_result;
if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
goto err;
}
ctx = BN_CTX_new();
if (ctx == NULL)
goto err;
BN_CTX_start(ctx);
tmp = BN_CTX_get(ctx);
if (tmp == NULL)
goto err;
if (dh->priv_key == NULL) {
DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
goto err;
}
if (dh->flags & DH_FLAG_CACHE_MONT_P) {
mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
dh->lock, dh->p, ctx);
BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
if (!mont)
goto err;
}
if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
goto err;
}
if (!dh->
meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
goto err;
}
ret = BN_bn2bin(tmp, key);
err:
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ret;
}
static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
const BIGNUM *a, const BIGNUM *p,
const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
{
return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
}
static int dh_init(DH *dh)
{
dh->flags |= DH_FLAG_CACHE_MONT_P;
return 1;
}
static int dh_finish(DH *dh)
{
BN_MONT_CTX_free(dh->method_mont_p);
return 1;
}
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