[331] | 1 | /*
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| 2 | * Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | /* ====================================================================
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| 11 | * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
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| 12 | *
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| 13 | * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
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| 14 | * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
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| 15 | * to the OpenSSL project.
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| 16 | *
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| 17 | * The ECC Code is licensed pursuant to the OpenSSL open source
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| 18 | * license provided below.
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| 19 | *
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| 20 | * The ECDH software is originally written by Douglas Stebila of
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| 21 | * Sun Microsystems Laboratories.
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| 22 | *
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| 23 | */
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| 24 |
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| 25 | #include <string.h>
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| 26 | #include <limits.h>
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| 27 |
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| 28 | #include "internal/cryptlib.h"
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| 29 |
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| 30 | #include <openssl/err.h>
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| 31 | #include <openssl/bn.h>
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| 32 | #include <openssl/objects.h>
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| 33 | #include <openssl/ec.h>
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| 34 | #include "ec_lcl.h"
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| 35 |
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| 36 | int ossl_ecdh_compute_key(unsigned char **psec, size_t *pseclen,
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| 37 | const EC_POINT *pub_key, const EC_KEY *ecdh)
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| 38 | {
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| 39 | if (ecdh->group->meth->ecdh_compute_key == NULL) {
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| 40 | ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_CURVE_DOES_NOT_SUPPORT_ECDH);
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| 41 | return 0;
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| 42 | }
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| 43 |
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| 44 | return ecdh->group->meth->ecdh_compute_key(psec, pseclen, pub_key, ecdh);
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| 45 | }
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| 46 |
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| 47 | /*-
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| 48 | * This implementation is based on the following primitives in the IEEE 1363 standard:
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| 49 | * - ECKAS-DH1
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| 50 | * - ECSVDP-DH
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| 51 | */
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| 52 | int ecdh_simple_compute_key(unsigned char **pout, size_t *poutlen,
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| 53 | const EC_POINT *pub_key, const EC_KEY *ecdh)
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| 54 | {
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| 55 | BN_CTX *ctx;
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| 56 | EC_POINT *tmp = NULL;
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| 57 | BIGNUM *x = NULL, *y = NULL;
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| 58 | const BIGNUM *priv_key;
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| 59 | const EC_GROUP *group;
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| 60 | int ret = 0;
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| 61 | size_t buflen, len;
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| 62 | unsigned char *buf = NULL;
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| 63 |
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| 64 | if ((ctx = BN_CTX_new()) == NULL)
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| 65 | goto err;
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| 66 | BN_CTX_start(ctx);
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| 67 | x = BN_CTX_get(ctx);
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| 68 | y = BN_CTX_get(ctx);
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| 69 |
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| 70 | priv_key = EC_KEY_get0_private_key(ecdh);
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| 71 | if (priv_key == NULL) {
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| 72 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_NO_PRIVATE_VALUE);
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| 73 | goto err;
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| 74 | }
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| 75 |
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| 76 | group = EC_KEY_get0_group(ecdh);
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| 77 |
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| 78 | if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) {
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| 79 | if (!EC_GROUP_get_cofactor(group, x, NULL) ||
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| 80 | !BN_mul(x, x, priv_key, ctx)) {
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| 81 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
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| 82 | goto err;
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| 83 | }
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| 84 | priv_key = x;
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| 85 | }
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| 86 |
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| 87 | if ((tmp = EC_POINT_new(group)) == NULL) {
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| 88 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
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| 89 | goto err;
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| 90 | }
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| 91 |
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| 92 | if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) {
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| 93 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
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| 94 | goto err;
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| 95 | }
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| 96 |
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| 97 | if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
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| 98 | NID_X9_62_prime_field) {
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| 99 | if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx)) {
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| 100 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
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| 101 | goto err;
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| 102 | }
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| 103 | }
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| 104 | #ifndef OPENSSL_NO_EC2M
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| 105 | else {
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| 106 | if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) {
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| 107 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
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| 108 | goto err;
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| 109 | }
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| 110 | }
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| 111 | #endif
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| 112 |
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| 113 | buflen = (EC_GROUP_get_degree(group) + 7) / 8;
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| 114 | len = BN_num_bytes(x);
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| 115 | if (len > buflen) {
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| 116 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_INTERNAL_ERROR);
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| 117 | goto err;
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| 118 | }
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| 119 | if ((buf = OPENSSL_malloc(buflen)) == NULL) {
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| 120 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
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| 121 | goto err;
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| 122 | }
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| 123 |
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| 124 | memset(buf, 0, buflen - len);
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| 125 | if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) {
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| 126 | ECerr(EC_F_ECDH_SIMPLE_COMPUTE_KEY, ERR_R_BN_LIB);
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| 127 | goto err;
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| 128 | }
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| 129 |
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| 130 | *pout = buf;
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| 131 | *poutlen = buflen;
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| 132 | buf = NULL;
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| 133 |
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| 134 | ret = 1;
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| 135 |
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| 136 | err:
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| 137 | EC_POINT_free(tmp);
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| 138 | if (ctx)
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| 139 | BN_CTX_end(ctx);
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| 140 | BN_CTX_free(ctx);
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| 141 | OPENSSL_free(buf);
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| 142 | return ret;
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| 143 | }
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