crypto/ec/ecdh_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 "internal/cryptlib.h"
  74
  75 #include <openssl/err.h>
  76 #include <openssl/bn.h>
  77 #include <openssl/objects.h>
  78 #include <openssl/ec.h>
  79 #include "ec_lcl.h"
  80
  81 /*-
  82  * This implementation is based on the following primitives in the IEEE 1363 standard:
  83  *  - ECKAS-DH1
  84  *  - ECSVDP-DH
  85  * Finally an optional KDF is applied.
  86  */
  87 int ossl_ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
  88                           const EC_KEY *ecdh,
  89                           void *(*KDF) (const void *in, size_t inlen,
  90                                         void *out, size_t *outlen))
  91 {
  92     BN_CTX *ctx;
  93     EC_POINT *tmp = NULL;
  94     BIGNUM *x = NULL, *y = NULL;
  95     const BIGNUM *priv_key;
  96     const EC_GROUP *group;
  97     int ret = -1;
  98     size_t buflen, len;
  99     unsigned char *buf = NULL;
 100
 101     if (outlen > INT_MAX) {
 102         ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); /* sort of,
 103                                                                  * anyway */
 104         return -1;
 105     }
 106
 107     if ((ctx = BN_CTX_new()) == NULL)
 108         goto err;
 109     BN_CTX_start(ctx);
 110     x = BN_CTX_get(ctx);
 111     y = BN_CTX_get(ctx);
 112
 113     priv_key = EC_KEY_get0_private_key(ecdh);
 114     if (priv_key == NULL) {
 115         ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_NO_PRIVATE_VALUE);
 116         goto err;
 117     }
 118
 119     group = EC_KEY_get0_group(ecdh);
 120
 121     if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) {
 122         if (!EC_GROUP_get_cofactor(group, x, ctx) ||
 123             !BN_mul(x, x, priv_key, ctx)) {
 124             ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
 125             goto err;
 126         }
 127         priv_key = x;
 128     }
 129
 130     if ((tmp = EC_POINT_new(group)) == NULL) {
 131         ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
 132         goto err;
 133     }
 134
 135     if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) {
 136         ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
 137         goto err;
 138     }
 139
 140     if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
 141         NID_X9_62_prime_field) {
 142         if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx)) {
 143             ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
 144             goto err;
 145         }
 146     }
 147 #ifndef OPENSSL_NO_EC2M
 148     else {
 149         if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) {
 150             ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_POINT_ARITHMETIC_FAILURE);
 151             goto err;
 152         }
 153     }
 154 #endif
 155
 156     buflen = (EC_GROUP_get_degree(group) + 7) / 8;
 157     len = BN_num_bytes(x);
 158     if (len > buflen) {
 159         ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_INTERNAL_ERROR);
 160         goto err;
 161     }
 162     if ((buf = OPENSSL_malloc(buflen)) == NULL) {
 163         ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
 164         goto err;
 165     }
 166
 167     memset(buf, 0, buflen - len);
 168     if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) {
 169         ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, ERR_R_BN_LIB);
 170         goto err;
 171     }
 172
 173     if (KDF != 0) {
 174         if (KDF(buf, buflen, out, &outlen) == NULL) {
 175             ECerr(EC_F_OSSL_ECDH_COMPUTE_KEY, EC_R_KDF_FAILED);
 176             goto err;
 177         }
 178         ret = outlen;
 179     } else {
 180         /* no KDF, just copy as much as we can */
 181         if (outlen > buflen)
 182             outlen = buflen;
 183         memcpy(out, buf, outlen);
 184         ret = outlen;
 185     }
 186
 187  err:
 188     EC_POINT_free(tmp);
 189     if (ctx)
 190         BN_CTX_end(ctx);
 191     BN_CTX_free(ctx);
 192     OPENSSL_free(buf);
 193     return (ret);
 194 }