/* * Copyright 2002-2020 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 #include #include "internal/cryptlib.h" #include #include #include #include #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) { ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, 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 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) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); goto err; } priv_key = EC_KEY_get0_private_key(ecdh); if (priv_key == NULL) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, 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) || !BN_mul(x, x, priv_key, ctx)) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); goto err; } priv_key = x; } if ((tmp = EC_POINT_new(group)) == NULL) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); goto err; } if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, 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)) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, 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) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_INTERNAL_ERROR); goto err; } if ((buf = OPENSSL_malloc(buflen)) == NULL) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); goto err; } memset(buf, 0, buflen - len); if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) { ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, 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; }