1 /* 2 * Copyright 2002-2019 The OpenSSL Project Authors. All Rights Reserved. 3 * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved 4 * 5 * Licensed under the OpenSSL license (the "License"). You may not use 6 * this file except in compliance with the License. You can obtain a copy 7 * in the file LICENSE in the source distribution or at 8 * https://www.openssl.org/source/license.html 9 */ 10 11 #include <string.h> 12 #include <limits.h> 13 14 #include "internal/cryptlib.h" 15 16 #include <openssl/err.h> 17 #include <openssl/bn.h> 18 #include <openssl/objects.h> 19 #include <openssl/ec.h> 20 #include "ec_lcl.h" 21 22 int ossl_ecdh_compute_key(unsigned char **psec, size_t *pseclen, 23 const EC_POINT *pub_key, const EC_KEY *ecdh) 24 { 25 if (ecdh->group->meth->ecdh_compute_key == NULL) { 26 ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_CURVE_DOES_NOT_SUPPORT_ECDH); 27 return 0; 28 } 29 30 return ecdh->group->meth->ecdh_compute_key(psec, pseclen, pub_key, ecdh); 31 } 32 33 /*- 34 * This implementation is based on the following primitives in the IEEE 1363 standard: 35 * - ECKAS-DH1 36 * - ECSVDP-DH 37 */ 38 int ecdh_simple_compute_key(unsigned char **pout, size_t *poutlen, 39 const EC_POINT *pub_key, const EC_KEY *ecdh) 40 { 41 BN_CTX *ctx; 42 EC_POINT *tmp = NULL; 43 BIGNUM *x = NULL; 44 const BIGNUM *priv_key; 45 const EC_GROUP *group; 46 int ret = 0; 47 size_t buflen, len; 48 unsigned char *buf = NULL; 49 50 if ((ctx = BN_CTX_new()) == NULL) 51 goto err; 52 BN_CTX_start(ctx); 53 x = BN_CTX_get(ctx); 54 if (x == NULL) { 55 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); 56 goto err; 57 } 58 59 priv_key = EC_KEY_get0_private_key(ecdh); 60 if (priv_key == NULL) { 61 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_NO_PRIVATE_VALUE); 62 goto err; 63 } 64 65 group = EC_KEY_get0_group(ecdh); 66 67 if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) { 68 if (!EC_GROUP_get_cofactor(group, x, NULL) || 69 !BN_mul(x, x, priv_key, ctx)) { 70 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); 71 goto err; 72 } 73 priv_key = x; 74 } 75 76 if ((tmp = EC_POINT_new(group)) == NULL) { 77 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); 78 goto err; 79 } 80 81 if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) { 82 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE); 83 goto err; 84 } 85 86 if (!EC_POINT_get_affine_coordinates(group, tmp, x, NULL, ctx)) { 87 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE); 88 goto err; 89 } 90 91 buflen = (EC_GROUP_get_degree(group) + 7) / 8; 92 len = BN_num_bytes(x); 93 if (len > buflen) { 94 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_INTERNAL_ERROR); 95 goto err; 96 } 97 if ((buf = OPENSSL_malloc(buflen)) == NULL) { 98 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); 99 goto err; 100 } 101 102 memset(buf, 0, buflen - len); 103 if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) { 104 ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_BN_LIB); 105 goto err; 106 } 107 108 *pout = buf; 109 *poutlen = buflen; 110 buf = NULL; 111 112 ret = 1; 113 114 err: 115 EC_POINT_clear_free(tmp); 116 BN_CTX_end(ctx); 117 BN_CTX_free(ctx); 118 OPENSSL_free(buf); 119 return ret; 120 } 121