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
  71 #include <string.h>
  72 #include <limits.h>
  73
  74 #include "cryptlib.h"
  75
  76 #include <openssl/ecdh.h>
  77 #include <openssl/err.h>
  78 #include <openssl/sha.h>
  79 #include <openssl/obj_mac.h>
  80 #include <openssl/bn.h>
  81
  82 static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key, EC_KEY *ecdh,
  83                             void *(*KDF)(void *in, size_t inlen, void *out, size_t outlen));
  84
  85 static ECDH_METHOD openssl_ecdh_meth = {
  86         "OpenSSL ECDH method",
  87         ecdh_compute_key,
  88 #if 0
  89         NULL, /* init     */
  90         NULL, /* finish   */
  91 #endif
  92         0,    /* flags    */
  93         NULL  /* app_data */
  94 };
  95
  96 const ECDH_METHOD *ECDH_OpenSSL(void)
  97         {
  98         return &openssl_ecdh_meth;
  99         }
 100
 101
 102 /* This implementation is based on the following primitives in the IEEE 1363 standard:
 103  *  - ECKAS-DH1
 104  *  - ECSVDP-DH
 105  * Finally an optional KDF is applied.
 106  */
 107 static int ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key, EC_KEY *ecdh,
 108                             void *(*KDF)(void *in, size_t inlen, void *out, size_t outlen))
 109         {
 110         BN_CTX *ctx;
 111         EC_POINT *tmp=NULL;
 112         BIGNUM *x=NULL, *y=NULL;
 113         int ret= -1;
 114         size_t buflen, len;
 115         unsigned char *buf=NULL;
 116
 117         if (outlen > INT_MAX)
 118                 {
 119                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE); /* sort of, anyway */
 120                 return -1;
 121                 }
 122
 123         if ((ctx = BN_CTX_new()) == NULL) goto err;
 124         BN_CTX_start(ctx);
 125         x = BN_CTX_get(ctx);
 126         y = BN_CTX_get(ctx);
 127
 128         if (ecdh->priv_key == NULL)
 129                 {
 130                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_NO_PRIVATE_VALUE);
 131                 goto err;
 132                 }
 133
 134         if ((tmp=EC_POINT_new(ecdh->group)) == NULL)
 135                 {
 136                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE);
 137                 goto err;
 138                 }
 139
 140         if (!EC_POINT_mul(ecdh->group, tmp, NULL, pub_key, ecdh->priv_key, ctx))
 141                 {
 142                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
 143                 goto err;
 144                 }
 145
 146         if (EC_METHOD_get_field_type(EC_GROUP_method_of(ecdh->group)) == NID_X9_62_prime_field)
 147                 {
 148                 if (!EC_POINT_get_affine_coordinates_GFp(ecdh->group, tmp, x, y, ctx))
 149                         {
 150                         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
 151                         goto err;
 152                         }
 153                 }
 154         else
 155                 {
 156                 if (!EC_POINT_get_affine_coordinates_GF2m(ecdh->group, tmp, x, y, ctx))
 157                         {
 158                         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
 159                         goto err;
 160                         }
 161                 }
 162
 163         buflen = (EC_GROUP_get_degree(ecdh->group) + 7)/8;
 164         len = BN_num_bytes(x);
 165         if (len > buflen)
 166                 {
 167                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_INTERNAL_ERROR);
 168                 goto err;
 169                 }
 170         if ((buf = OPENSSL_malloc(buflen)) == NULL)
 171                 {
 172                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE);
 173                 goto err;
 174                 }
 175
 176         memset(buf, 0, buflen - len);
 177         if (len != (size_t)BN_bn2bin(x, buf + buflen - len))
 178                 {
 179                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_BN_LIB);
 180                 goto err;
 181                 }
 182
 183         if (KDF != 0)
 184                 {
 185                 if (KDF(buf, buflen, out, outlen) == NULL)
 186                         {
 187                         ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_KDF_FAILED);
 188                         goto err;
 189                         }
 190                 ret = outlen;
 191                 }
 192         else
 193                 {
 194                 /* no KDF, just copy as much as we can */
 195                 if (outlen > buflen)
 196                         outlen = buflen;
 197                 memcpy(out, buf, outlen);
 198                 ret = outlen;
 199                 }
 200
 201 err:
 202         if (tmp) EC_POINT_free(tmp);
 203         if (ctx) BN_CTX_end(ctx);
 204         if (ctx) BN_CTX_free(ctx);
 205         if (buf) OPENSSL_free(buf);
 206         return(ret);
 207         }