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- /*
- * Copyright 2002-2021 The OpenSSL Project Authors. All Rights Reserved.
- * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
- *
- * Licensed under the Apache License 2.0 (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
- */
- /*
- * ECDH low level APIs are deprecated for public use, but still ok for
- * internal use.
- */
- #include "internal/deprecated.h"
- #include <string.h>
- #include <limits.h>
- #include "internal/cryptlib.h"
- #include <openssl/err.h>
- #include <openssl/bn.h>
- #include <openssl/objects.h>
- #include <openssl/ec.h>
- #include "ec_local.h"
- int ossl_ecdh_compute_key(unsigned char **psec, size_t *pseclen,
- const EC_POINT *pub_key, const EC_KEY *ecdh)
- {
- if (ecdh->group->meth->ecdh_compute_key == NULL) {
- ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDH);
- return 0;
- }
- return ecdh->group->meth->ecdh_compute_key(psec, pseclen, pub_key, ecdh);
- }
- /*-
- * This implementation is based on the following primitives in the
- * IEEE 1363 standard:
- * - ECKAS-DH1
- * - ECSVDP-DH
- *
- * It also conforms to SP800-56A r3
- * See Section 5.7.1.2 "Elliptic Curve Cryptography Cofactor Diffie-Hellman
- * (ECC CDH) Primitive:". The steps listed below refer to SP800-56A.
- */
- int ossl_ecdh_simple_compute_key(unsigned char **pout, size_t *poutlen,
- const EC_POINT *pub_key, const EC_KEY *ecdh)
- {
- BN_CTX *ctx;
- EC_POINT *tmp = NULL;
- BIGNUM *x = NULL;
- const BIGNUM *priv_key;
- const EC_GROUP *group;
- int ret = 0;
- size_t buflen, len;
- unsigned char *buf = NULL;
- if ((ctx = BN_CTX_new_ex(ecdh->libctx)) == NULL)
- goto err;
- BN_CTX_start(ctx);
- x = BN_CTX_get(ctx);
- if (x == NULL) {
- ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
- goto err;
- }
- priv_key = EC_KEY_get0_private_key(ecdh);
- if (priv_key == NULL) {
- ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
- goto err;
- }
- group = EC_KEY_get0_group(ecdh);
- /*
- * Step(1) - Compute the point tmp = cofactor * owners_private_key
- * * peer_public_key.
- */
- if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) {
- if (!EC_GROUP_get_cofactor(group, x, NULL)) {
- ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
- goto err;
- }
- if (!BN_mul(x, x, priv_key, ctx)) {
- ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
- goto err;
- }
- priv_key = x;
- }
- if ((tmp = EC_POINT_new(group)) == NULL) {
- ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
- goto err;
- }
- if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) {
- ERR_raise(ERR_LIB_EC, EC_R_POINT_ARITHMETIC_FAILURE);
- goto err;
- }
- /*
- * Step(2) : If point tmp is at infinity then clear intermediate values and
- * exit. Note: getting affine coordinates returns 0 if point is at infinity.
- * Step(3a) : Get x-coordinate of point x = tmp.x
- */
- if (!EC_POINT_get_affine_coordinates(group, tmp, x, NULL, ctx)) {
- ERR_raise(ERR_LIB_EC, EC_R_POINT_ARITHMETIC_FAILURE);
- goto err;
- }
- /*
- * Step(3b) : convert x to a byte string, using the field-element-to-byte
- * string conversion routine defined in Appendix C.2
- */
- buflen = (EC_GROUP_get_degree(group) + 7) / 8;
- len = BN_num_bytes(x);
- if (len > buflen) {
- ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
- goto err;
- }
- if ((buf = OPENSSL_malloc(buflen)) == NULL)
- goto err;
- memset(buf, 0, buflen - len);
- if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) {
- ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
- goto err;
- }
- *pout = buf;
- *poutlen = buflen;
- buf = NULL;
- ret = 1;
- err:
- /* Step(4) : Destroy all intermediate calculations */
- BN_clear(x);
- EC_POINT_clear_free(tmp);
- BN_CTX_end(ctx);
- BN_CTX_free(ctx);
- OPENSSL_free(buf);
- return ret;
- }
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