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ech_ossl.c

/* crypto/ecdh/ech_ossl.c */
/* ====================================================================
 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
 *
 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included
 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed
 * to the OpenSSL project.
 *
 * The ECC Code is licensed pursuant to the OpenSSL open source
 * license provided below.
 *
 * The ECDH software is originally written by Douglas Stebila of
 * Sun Microsystems Laboratories.
 *
 */
/* ====================================================================
 * Copyright (c) 1998-2003 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */


#include <string.h>
#include <limits.h>

#include "cryptlib.h"

#include "ech_locl.h"
#include <openssl/err.h>
#include <openssl/sha.h>
#include <openssl/obj_mac.h>
#include <openssl/bn.h>

static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key,
      EC_KEY *ecdh, 
      void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen));

static ECDH_METHOD openssl_ecdh_meth = {
      "OpenSSL ECDH method",
      ecdh_compute_key,
#if 0
      NULL, /* init     */
      NULL, /* finish   */
#endif
      0,    /* flags    */
      NULL  /* app_data */
};

const ECDH_METHOD *ECDH_OpenSSL(void)
      {
      return &openssl_ecdh_meth;
      }


/* This implementation is based on the following primitives in the IEEE 1363 standard:
 *  - ECKAS-DH1
 *  - ECSVDP-DH
 * Finally an optional KDF is applied.
 */
static int ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
      EC_KEY *ecdh,
      void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen))
      {
      BN_CTX *ctx;
      EC_POINT *tmp=NULL;
      BIGNUM *x=NULL, *y=NULL;
      const BIGNUM *priv_key;
      const EC_GROUP* group;
      int ret= -1;
      size_t buflen, len;
      unsigned char *buf=NULL;

      if (outlen > INT_MAX)
            {
            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE); /* sort of, anyway */
            return -1;
            }

      if ((ctx = BN_CTX_new()) == NULL) goto err;
      BN_CTX_start(ctx);
      x = BN_CTX_get(ctx);
      y = BN_CTX_get(ctx);
      
      priv_key = EC_KEY_get0_private_key(ecdh);
      if (priv_key == NULL)
            {
            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_NO_PRIVATE_VALUE);
            goto err;
            }

      group = EC_KEY_get0_group(ecdh);
      if ((tmp=EC_POINT_new(group)) == NULL)
            {
            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE);
            goto err;
            }

      if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) 
            {
            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
            goto err;
            }
            
      if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == NID_X9_62_prime_field) 
            {
            if (!EC_POINT_get_affine_coordinates_GFp(group, tmp, x, y, ctx)) 
                  {
                  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
                  goto err;
                  }
            }
      else
            {
            if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) 
                  {
                  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_POINT_ARITHMETIC_FAILURE);
                  goto err;
                  }
            }

      buflen = (EC_GROUP_get_degree(group) + 7)/8;
      len = BN_num_bytes(x);
      if (len > buflen)
            {
            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_INTERNAL_ERROR);
            goto err;
            }
      if ((buf = OPENSSL_malloc(buflen)) == NULL)
            {
            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE);
            goto err;
            }
      
      memset(buf, 0, buflen - len);
      if (len != (size_t)BN_bn2bin(x, buf + buflen - len))
            {
            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_BN_LIB);
            goto err;
            }

      if (KDF != 0)
            {
            if (KDF(buf, buflen, out, &outlen) == NULL)
                  {
                  ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ECDH_R_KDF_FAILED);
                  goto err;
                  }
            ret = outlen;
            }
      else
            {
            /* no KDF, just copy as much as we can */
            if (outlen > buflen)
                  outlen = buflen;
            memcpy(out, buf, outlen);
            ret = outlen;
            }
      
err:
      if (tmp) EC_POINT_free(tmp);
      if (ctx) BN_CTX_end(ctx);
      if (ctx) BN_CTX_free(ctx);
      if (buf) OPENSSL_free(buf);
      return(ret);
      }

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