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/* $OpenBSD: ech_key.c,v 1.30 2023/07/02 02:28:20 tb Exp $ */
/* ====================================================================
* Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
*
* The Elliptic Curve Public-Key Crypto Library (ECC Code) included
* herein is developed by SUN MICROSYSTEMS, INC., and is contributed
* to the OpenSSL project.
*
* The ECC Code is licensed pursuant to the OpenSSL open source
* license provided below.
*
* The ECDH software is originally written by Douglas Stebila of
* Sun Microsystems Laboratories.
*
*/
/* ====================================================================
* Copyright (c) 1998-2003 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@OpenSSL.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* This product includes cryptographic software written by Eric Young
* (eay@cryptsoft.com). This product includes software written by Tim
* Hudson (tjh@cryptsoft.com).
*
*/
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/opensslconf.h>
#include <openssl/bn.h>
#include <openssl/ec.h>
#include <openssl/ecdh.h>
#include <openssl/err.h>
#include "ec_local.h"
/*
* Based on the ECKAS-DH1 and ECSVDP-DH primitives in the IEEE 1363 standard.
*/
/* XXX - KDF handling moved to ECDH_compute_key(). See OpenSSL e2285d87. */
int
ossl_ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
EC_KEY *ecdh,
void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen))
{
BN_CTX *ctx;
EC_POINT *point = NULL;
BIGNUM *x;
const BIGNUM *priv_key;
const EC_GROUP* group;
unsigned char *buf = NULL;
int buflen;
int ret = -1;
if (outlen > INT_MAX) {
/* Sort of, anyway. */
ECDHerror(ERR_R_MALLOC_FAILURE);
return -1;
}
if ((ctx = BN_CTX_new()) == NULL)
goto err;
BN_CTX_start(ctx);
if ((x = BN_CTX_get(ctx)) == NULL)
goto err;
if ((priv_key = EC_KEY_get0_private_key(ecdh)) == NULL) {
ECDHerror(ECDH_R_NO_PRIVATE_VALUE);
goto err;
}
if ((group = EC_KEY_get0_group(ecdh)) == NULL)
goto err;
if (!EC_POINT_is_on_curve(group, pub_key, ctx))
goto err;
if ((point = EC_POINT_new(group)) == NULL) {
ECDHerror(ERR_R_MALLOC_FAILURE);
goto err;
}
if (!EC_POINT_mul(group, point, NULL, pub_key, priv_key, ctx)) {
ECDHerror(ECDH_R_POINT_ARITHMETIC_FAILURE);
goto err;
}
if (!EC_POINT_get_affine_coordinates(group, point, x, NULL, ctx)) {
ECDHerror(ECDH_R_POINT_ARITHMETIC_FAILURE);
goto err;
}
if ((buflen = ECDH_size(ecdh)) < BN_num_bytes(x)) {
ECDHerror(ERR_R_INTERNAL_ERROR);
goto err;
}
if (KDF == NULL && outlen < buflen) {
/* The resulting key would be truncated. */
ECDHerror(ECDH_R_KEY_TRUNCATION);
goto err;
}
if ((buf = malloc(buflen)) == NULL) {
ECDHerror(ERR_R_MALLOC_FAILURE);
goto err;
}
if (BN_bn2binpad(x, buf, buflen) != buflen) {
ECDHerror(ERR_R_BN_LIB);
goto err;
}
if (KDF != NULL) {
if (KDF(buf, buflen, out, &outlen) == NULL) {
ECDHerror(ECDH_R_KDF_FAILED);
goto err;
}
} else {
/* No KDF, just copy out the key and zero the rest. */
if (outlen > buflen) {
memset((void *)((uintptr_t)out + buflen), 0, outlen - buflen);
outlen = buflen;
}
memcpy(out, buf, outlen);
}
ret = outlen;
err:
EC_POINT_free(point);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
free(buf);
return ret;
}
int
ECDH_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
EC_KEY *eckey,
void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen))
{
if (eckey->meth->compute_key == NULL) {
ECerror(EC_R_NOT_IMPLEMENTED);
return 0;
}
return eckey->meth->compute_key(out, outlen, pub_key, eckey, KDF);
}
int
ECDH_size(const EC_KEY *d)
{
return (EC_GROUP_get_degree(EC_KEY_get0_group(d)) + 7) / 8;
}
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