/*
* Copyright (C) 2019 Sean Parkinson, wolfSSL Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "wolfssl_common.h"
#ifdef HAVE_ECC_DHE
#include <wolfssl/wolfcrypt/ecc.h>
#include "wolfssl_ec_diffie_hellman.h"
#include "wolfssl_util.h"
#include <utils/debug.h>
typedef struct private_wolfssl_ec_diffie_hellman_t private_wolfssl_ec_diffie_hellman_t;
/**
* Private data of an wolfssl_ec_diffie_hellman_t object.
*/
struct private_wolfssl_ec_diffie_hellman_t {
/**
* Public wolfssl_ec_diffie_hellman_t interface.
*/
wolfssl_ec_diffie_hellman_t public;
/**
* Diffie Hellman group number.
*/
diffie_hellman_group_t group;
/**
* EC curve id for creating keys
*/
ecc_curve_id curve_id;
/**
* Size of an ordinate in bytes
*/
int keysize;
/**
* EC private (public) key
*/
ecc_key key;
/**
* Shared secret
*/
chunk_t shared_secret;
};
/**
* Convert a chunk to an ecc_point (which must already exist). The x and y
* coordinates of the point have to be concatenated in the chunk.
*/
static bool chunk2ecp(chunk_t chunk, ecc_point *point)
{
if (!wolfssl_mp_split(chunk, point->x, point->y))
{
return FALSE;
}
if (mp_set(point->z, 1) != 0)
{
return FALSE;
}
return TRUE;
}
/**
* Convert an ec_point to a chunk by concatenating the x and y coordinates of
* the point. This function allocates memory for the chunk.
*/
static bool ecp2chunk(int keysize, ecc_point *point, chunk_t *chunk,
bool x_coordinate_only)
{
mp_int *y = NULL;
if (!x_coordinate_only)
{
keysize *= 2;
y = point->y;
}
return wolfssl_mp_cat(keysize, point->x, y, chunk);
}
/**
* Perform the elliptic curve scalar multiplication.
*/
static bool wolfssl_ecc_multiply(const ecc_set_type *ecc_set, mp_int *scalar,
ecc_point *point, ecc_point *r)
{
mp_int a, prime;
int ret;
if (mp_init(&a) != 0)
{
return FALSE;
}
if (mp_init(&prime) != 0)
{
mp_free(&a);
return FALSE;
}
ret = mp_read_radix(&a, ecc_set->Af, MP_RADIX_HEX);
if (ret == 0)
{
ret = mp_read_radix(&prime, ecc_set->prime, MP_RADIX_HEX);
}
if (ret == 0)
{
/* multiply the point by our secret */
ret = wc_ecc_mulmod(scalar, point, r, &a, &prime, 1);
}
mp_free(&prime);
mp_free(&a);
return ret == 0;
}
/**
* Compute the shared secret.
*
* We cannot use the function wc_ecc_shared_secret() because that returns only
* the x coordinate of the shared secret point (which is defined, for instance,
* in 'NIST SP 800-56A').
* However, we need both coordinates as RFC 4753 says: "The Diffie-Hellman
* public value is obtained by concatenating the x and y values. The format
* of the Diffie-Hellman shared secret value is the same as that of the
* Diffie-Hellman public value."
*/
static bool compute_shared_key(private_wolfssl_ec_diffie_hellman_t *this,
ecc_point *pub_key, chunk_t *shared_secret)
{
ecc_point* secret;
bool success = FALSE;
if ((secret = wc_ecc_new_point()) == NULL)
{
return FALSE;
}
if (wolfssl_ecc_multiply(this->key.dp, &this->key.k, pub_key, secret))
{
success = ecp2chunk(this->keysize, secret, shared_secret, TRUE);
}
wc_ecc_del_point(secret);
return success;
}
METHOD(diffie_hellman_t, set_other_public_value, bool,
private_wolfssl_ec_diffie_hellman_t *this, chunk_t value)
{
ecc_point *pub_key;
if (!diffie_hellman_verify_value(this->group, value))
{
return FALSE;
}
if ((pub_key = wc_ecc_new_point()) == NULL)
{
return FALSE;
}
if (!chunk2ecp(value, pub_key))
{
DBG1(DBG_LIB, "ECDH public value is malformed");
wc_ecc_del_point(pub_key);
return FALSE;
}
chunk_clear(&this->shared_secret);
if (!compute_shared_key(this, pub_key, &this->shared_secret))
{
DBG1(DBG_LIB, "ECDH shared secret computation failed");
chunk_clear(&this->shared_secret);
wc_ecc_del_point(pub_key);
return FALSE;
}
wc_ecc_del_point(pub_key);
return TRUE;
}
METHOD(diffie_hellman_t, get_my_public_value, bool,
private_wolfssl_ec_diffie_hellman_t *this,chunk_t *value)
{
return ecp2chunk(this->keysize, &this->key.pubkey, value, FALSE);
}
METHOD(diffie_hellman_t, set_private_value, bool,
private_wolfssl_ec_diffie_hellman_t *this, chunk_t value)
{
bool success = FALSE;
ecc_point *base;
int ret;
if ((base = wc_ecc_new_point()) == NULL)
{
return FALSE;
}
ret = mp_read_unsigned_bin(&this->key.k, value.ptr, value.len);
/* get base point */
if (ret == 0)
{
ret = mp_read_radix(base->x, this->key.dp->Gx, MP_RADIX_HEX);
}
if (ret == 0)
{
ret = mp_read_radix(base->y, this->key.dp->Gy, MP_RADIX_HEX);
}
if (ret == 0)
{
ret = mp_set(base->z, 1);
}
if (ret == 0)
{
/* calculate public key */
success = wolfssl_ecc_multiply(this->key.dp, &this->key.k, base,
&this->key.pubkey);
}
wc_ecc_del_point(base);
return success;
}
METHOD(diffie_hellman_t, get_shared_secret, bool,
private_wolfssl_ec_diffie_hellman_t *this, chunk_t *secret)
{
if (!this->shared_secret.len)
{
return FALSE;
}
*secret = chunk_clone(this->shared_secret);
return TRUE;
}
METHOD(diffie_hellman_t, get_dh_group, diffie_hellman_group_t,
private_wolfssl_ec_diffie_hellman_t *this)
{
return this->group;
}
METHOD(diffie_hellman_t, destroy, void,
private_wolfssl_ec_diffie_hellman_t *this)
{
wc_ecc_free(&this->key);
chunk_clear(&this->shared_secret);
free(this);
}
/*
* Described in header
*/
wolfssl_ec_diffie_hellman_t *wolfssl_ec_diffie_hellman_create(diffie_hellman_group_t group)
{
private_wolfssl_ec_diffie_hellman_t *this;
WC_RNG rng;
INIT(this,
.public = {
.dh = {
.get_shared_secret = _get_shared_secret,
.set_other_public_value = _set_other_public_value,
.get_my_public_value = _get_my_public_value,
.set_private_value = _set_private_value,
.get_dh_group = _get_dh_group,
.destroy = _destroy,
},
},
.group = group,
);
if (wc_ecc_init(&this->key) != 0)
{
DBG1(DBG_LIB, "key init failed, ecdh create failed");
free(this);
return NULL;
}
switch (group)
{
case ECP_192_BIT:
this->curve_id = ECC_SECP192R1;
this->keysize = 192 / 8;
break;
case ECP_224_BIT:
this->curve_id = ECC_SECP224R1;
this->keysize = 224 / 8;
break;
case ECP_256_BIT:
this->curve_id = ECC_SECP256R1;
this->keysize = 256 / 8;
break;
case ECP_384_BIT:
this->curve_id = ECC_SECP384R1;
this->keysize = 384 / 8;
break;
case ECP_521_BIT:
this->curve_id = ECC_SECP521R1;
this->keysize = (521 + 7) / 8;
break;
#ifdef HAVE_ECC_BRAINPOOL
case ECP_224_BP:
this->curve_id = ECC_BRAINPOOLP224R1;
this->keysize = 224 / 8;
break;
case ECP_256_BP:
this->curve_id = ECC_BRAINPOOLP256R1;
this->keysize = 256 / 8;
break;
case ECP_384_BP:
this->curve_id = ECC_BRAINPOOLP384R1;
this->keysize = 384 / 8;
break;
case ECP_512_BP:
this->curve_id = ECC_BRAINPOOLP512R1;
this->keysize = 512 / 8;
break;
#endif
default:
destroy(this);
return NULL;
}
if (wc_InitRng(&rng) != 0)
{
DBG1(DBG_LIB, "RNG init failed, ecdh create failed");
destroy(this);
return NULL;
}
/* generate an EC private (public) key */
if (wc_ecc_make_key_ex(&rng, this->keysize, &this->key,
this->curve_id) != 0)
{
DBG1(DBG_LIB, "make key failed, wolfssl ECDH create failed");
destroy(this);
return NULL;
}
wc_FreeRng(&rng);
return &this->public;
}
#endif /* HAVE_ECC_DHE */
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