crypto/ecdh/ech_ossl.c

   1 /* crypto/ecdh/ech_ossl.c */
   2 /* ====================================================================
   3  * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
   4  *
   5  * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
   6  * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
   7  * to the OpenSSL project.
   8  *
   9  * The ECC Code is licensed pursuant to the OpenSSL open source
  10  * license provided below.
  11  *
  12  * The ECDH software is originally written by Douglas Stebila of
  13  * Sun Microsystems Laboratories.
  14  *
  15  */
  16 /* ====================================================================
  17  * Copyright (c) 1998-2003 The OpenSSL Project.  All rights reserved.
  18  *
  19  * Redistribution and use in source and binary forms, with or without
  20  * modification, are permitted provided that the following conditions
  21  * are met:
  22  *
  23  * 1. Redistributions of source code must retain the above copyright
  24  *    notice, this list of conditions and the following disclaimer.
  25  *
  26  * 2. Redistributions in binary form must reproduce the above copyright
  27  *    notice, this list of conditions and the following disclaimer in
  28  *    the documentation and/or other materials provided with the
  29  *    distribution.
  30  *
  31  * 3. All advertising materials mentioning features or use of this
  32  *    software must display the following acknowledgment:
  33  *    "This product includes software developed by the OpenSSL Project
  34  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
  35  *
  36  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  37  *    endorse or promote products derived from this software without
  38  *    prior written permission. For written permission, please contact
  39  *    openssl-core@OpenSSL.org.
  40  *
  41  * 5. Products derived from this software may not be called "OpenSSL"
  42  *    nor may "OpenSSL" appear in their names without prior written
  43  *    permission of the OpenSSL Project.
  44  *
  45  * 6. Redistributions of any form whatsoever must retain the following
  46  *    acknowledgment:
  47  *    "This product includes software developed by the OpenSSL Project
  48  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
  49  *
  50  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  51  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  53  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  54  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  55  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  56  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  57  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  58  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  59  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  60  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  61  * OF THE POSSIBILITY OF SUCH DAMAGE.
  62  * ====================================================================
  63  *
  64  * This product includes cryptographic software written by Eric Young
  65  * (eay@cryptsoft.com).  This product includes software written by Tim
  66  * Hudson (tjh@cryptsoft.com).
  67  *
  68  */
  69
  70 #include <string.h>
  71 #include <limits.h>
  72
  73 #include "cryptlib.h"
  74
  75 #include "ech_locl.h"
  76 #include <openssl/err.h>
  77 #include <openssl/sha.h>
  78 #include <openssl/obj_mac.h>
  79 #include <openssl/bn.h>
  80
  81 static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key,
  82                             EC_KEY *ecdh,
  83                             void *(*KDF) (const void *in, size_t inlen,
  84                                           void *out, size_t *outlen));
  85
  86 static ECDH_METHOD openssl_ecdh_meth = {
  87     "OpenSSL ECDH method",
  88     ecdh_compute_key,
  89 #if 0
  90     NULL,                       /* init */
  91     NULL,                       /* finish */
  92 #endif
  93     0,                          /* flags */
  94     NULL                        /* app_data */
  95 };
  96
  97 const ECDH_METHOD *ECDH_OpenSSL(void)
  98 {
  99     return &openssl_ecdh_meth;
 100 }
 101
 102 /*-
 103  * This implementation is based on the following primitives in the IEEE 1363 standard:
 104  *  - ECKAS-DH1
 105  *  - ECSVDP-DH
 106  * Finally an optional KDF is applied.
 107  */
 108 static int ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
 109                             EC_KEY *ecdh,
 110                             void *(*KDF) (const void *in, size_t inlen,
 111                                           void *out, size_t *outlen))
 112 {
 113     BN_CTX *ctx;
 114     EC_POINT *tmp = NULL;
 115     BIGNUM *x = NULL, *y = NULL;
 116     const BIGNUM *priv_key;
 117     const EC_GROUP *group;
 118     int ret = -1;
 119     size_t buflen, len;
 120     unsigned char *buf = NULL;
 121
 122     if (outlen > INT_MAX) {
 123         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); /* sort of,
 124                                                                  * anyway */
 125         return -1;
 126     }
 127
 128     if ((ctx = BN_CTX_new()) == NULL)
 129         goto err;
 130     BN_CTX_start(ctx);
 131     x = BN_CTX_get(ctx);
 132     y = BN_CTX_get(ctx);
 133
 134     priv_key = EC_KEY_get0_private_key(ecdh);
 135     if (priv_key == NULL) {
 136         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_NO_PRIVATE_VALUE);
 137         goto err;
 138     }
 139
 140     group = EC_KEY_get0_group(ecdh);
 141
 142     if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) {
 143         if (!EC_GROUP_get_cofactor(group, x, ctx) ||
 144             !BN_mul(x, x, priv_key, ctx)) {
 145             ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
 146             goto err;
 147         }
 148         priv_key = x;
 149     }
 150
 151     if ((tmp = EC_POINT_new(group)) == NULL) {
 152         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
 153         goto err;
 154     }
 155
 156     if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) {
 157         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);
 158         goto err;
 159     }
 160
 161     if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
 162         NID_X9_62_prime_field) {
 163         if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx)) {
 164             ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);
 165             goto err;
 166         }
 167     }
 168 #ifndef OPENSSL_NO_EC2M
 169     else {
 170         if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) {
 171             ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);
 172             goto err;
 173         }
 174     }
 175 #endif
 176
 177     buflen = (EC_GROUP_get_degree(group) + 7) / 8;
 178     len = BN_num_bytes(x);
 179     if (len > buflen) {
 180         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_INTERNAL_ERROR);
 181         goto err;
 182     }
 183     if ((buf = OPENSSL_malloc(buflen)) == NULL) {
 184         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
 185         goto err;
 186     }
 187
 188     memset(buf, 0, buflen - len);
 189     if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) {
 190         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_BN_LIB);
 191         goto err;
 192     }
 193
 194     if (KDF != 0) {
 195         if (KDF(buf, buflen, out, &outlen) == NULL) {
 196             ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_KDF_FAILED);
 197             goto err;
 198         }
 199         ret = outlen;
 200     } else {
 201         /* no KDF, just copy as much as we can */
 202         if (outlen > buflen)
 203             outlen = buflen;
 204         memcpy(out, buf, outlen);
 205         ret = outlen;
 206     }
 207
 208  err:
 209     if (tmp)
 210         EC_POINT_clear_free(tmp);
 211     if (ctx)
 212         BN_CTX_end(ctx);
 213     if (ctx)
 214         BN_CTX_free(ctx);
 215     if (buf) {
 216         OPENSSL_cleanse(buf, buflen);
 217         OPENSSL_free(buf);
 218     }
 219     return (ret);
 220 }