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ecs_ossl.c

/* crypto/ecdsa/ecs_ossl.c */
/*
 * Written by Nils Larsch for the OpenSSL project
 */
/* ====================================================================
 * Copyright (c) 1998-2004 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 "ecs_locl.h"
#include <openssl/err.h>
#include <openssl/obj_mac.h>
#include <openssl/bn.h>

static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen, 
            const BIGNUM *, const BIGNUM *, EC_KEY *eckey);
static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, 
            BIGNUM **rp);
static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len, 
            const ECDSA_SIG *sig, EC_KEY *eckey);

static ECDSA_METHOD openssl_ecdsa_meth = {
      "OpenSSL ECDSA method",
      ecdsa_do_sign,
      ecdsa_sign_setup,
      ecdsa_do_verify,
#if 0
      NULL, /* init     */
      NULL, /* finish   */
#endif
      0,    /* flags    */
      NULL  /* app_data */
};

const ECDSA_METHOD *ECDSA_OpenSSL(void)
{
      return &openssl_ecdsa_meth;
}

static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
            BIGNUM **rp)
{
      BN_CTX   *ctx = NULL;
      BIGNUM       *k = NULL, *r = NULL, *order = NULL, *X = NULL;
      EC_POINT *tmp_point=NULL;
      const EC_GROUP *group;
      int    ret = 0;

      if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL)
      {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
            return 0;
      }

      if (ctx_in == NULL) 
      {
            if ((ctx = BN_CTX_new()) == NULL)
            {
                  ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,ERR_R_MALLOC_FAILURE);
                  return 0;
            }
      }
      else
            ctx = ctx_in;

      k     = BN_new(); /* this value is later returned in *kinvp */
      r     = BN_new(); /* this value is later returned in *rp    */
      order = BN_new();
      X     = BN_new();
      if (!k || !r || !order || !X)
      {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
            goto err;
      }
      if ((tmp_point = EC_POINT_new(group)) == NULL)
      {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
            goto err;
      }
      if (!EC_GROUP_get_order(group, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
            goto err;
      }
      
      do
      {
            /* get random k */      
            do
                  if (!BN_rand_range(k, order))
                  {
                        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,
                         ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);      
                        goto err;
                  }
            while (BN_is_zero(k));

            /* We do not want timing information to leak the length of k,
             * so we compute G*k using an equivalent scalar of fixed
             * bit-length. */

            if (!BN_add(k, k, order)) goto err;
            if (BN_num_bits(k) <= BN_num_bits(order))
                  if (!BN_add(k, k, order)) goto err;

            /* compute r the x-coordinate of generator * k */
            if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx))
            {
                  ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
                  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_point, X, NULL, ctx))
                  {
                        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,ERR_R_EC_LIB);
                        goto err;
                  }
            }
            else /* NID_X9_62_characteristic_two_field */
            {
                  if (!EC_POINT_get_affine_coordinates_GF2m(group,
                        tmp_point, X, NULL, ctx))
                  {
                        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,ERR_R_EC_LIB);
                        goto err;
                  }
            }
            if (!BN_nnmod(r, X, order, ctx))
            {
                  ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
                  goto err;
            }
      }
      while (BN_is_zero(r));

      /* compute the inverse of k */
      if (!BN_mod_inverse(k, k, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
            goto err;   
      }
      /* clear old values if necessary */
      if (*rp != NULL)
            BN_clear_free(*rp);
      if (*kinvp != NULL) 
            BN_clear_free(*kinvp);
      /* save the pre-computed values  */
      *rp    = r;
      *kinvp = k;
      ret = 1;
err:
      if (!ret)
      {
            if (k != NULL) BN_clear_free(k);
            if (r != NULL) BN_clear_free(r);
      }
      if (ctx_in == NULL) 
            BN_CTX_free(ctx);
      if (order != NULL)
            BN_free(order);
      if (tmp_point != NULL) 
            EC_POINT_free(tmp_point);
      if (X)
            BN_clear_free(X);
      return(ret);
}


static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len, 
            const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey)
{
      int     ok = 0, i;
      BIGNUM *kinv=NULL, *s, *m=NULL,*tmp=NULL,*order=NULL;
      const BIGNUM *ckinv;
      BN_CTX     *ctx = NULL;
      const EC_GROUP   *group;
      ECDSA_SIG  *ret;
      ECDSA_DATA *ecdsa;
      const BIGNUM *priv_key;

      ecdsa    = ecdsa_check(eckey);
      group    = EC_KEY_get0_group(eckey);
      priv_key = EC_KEY_get0_private_key(eckey);
      
      if (group == NULL || priv_key == NULL || ecdsa == NULL)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);
            return NULL;
      }

      ret = ECDSA_SIG_new();
      if (!ret)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
            return NULL;
      }
      s = ret->s;

      if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
            (tmp = BN_new()) == NULL || (m = BN_new()) == NULL)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
            goto err;
      }

      if (!EC_GROUP_get_order(group, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
            goto err;
      }
      i = BN_num_bits(order);
      /* Need to truncate digest if it is too long: first truncate whole
       * bytes.
       */
      if (8 * dgst_len > i)
            dgst_len = (i + 7)/8;
      if (!BN_bin2bn(dgst, dgst_len, m))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
            goto err;
      }
      /* If still too long truncate remaining bits with a shift */
      if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
            goto err;
      }
      do
      {
            if (in_kinv == NULL || in_r == NULL)
            {
                  if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r))
                  {
                        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,ERR_R_ECDSA_LIB);
                        goto err;
                  }
                  ckinv = kinv;
            }
            else
            {
                  ckinv  = in_kinv;
                  if (BN_copy(ret->r, in_r) == NULL)
                  {
                        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
                        goto err;
                  }
            }

            if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx))
            {
                  ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
                  goto err;
            }
            if (!BN_mod_add_quick(s, tmp, m, order))
            {
                  ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
                  goto err;
            }
            if (!BN_mod_mul(s, s, ckinv, order, ctx))
            {
                  ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
                  goto err;
            }
            if (BN_is_zero(s))
            {
                  /* if kinv and r have been supplied by the caller
                   * don't to generate new kinv and r values */
                  if (in_kinv != NULL && in_r != NULL)
                  {
                        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ECDSA_R_NEED_NEW_SETUP_VALUES);
                        goto err;
                  }
            }
            else
                  /* s != 0 => we have a valid signature */
                  break;
      }
      while (1);

      ok = 1;
err:
      if (!ok)
      {
            ECDSA_SIG_free(ret);
            ret = NULL;
      }
      if (ctx)
            BN_CTX_free(ctx);
      if (m)
            BN_clear_free(m);
      if (tmp)
            BN_clear_free(tmp);
      if (order)
            BN_free(order);
      if (kinv)
            BN_clear_free(kinv);
      return ret;
}

static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
            const ECDSA_SIG *sig, EC_KEY *eckey)
{
      int ret = -1, i;
      BN_CTX   *ctx;
      BIGNUM   *order, *u1, *u2, *m, *X;
      EC_POINT *point = NULL;
      const EC_GROUP *group;
      const EC_POINT *pub_key;

      /* check input values */
      if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
          (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);
            return -1;
      }

      ctx = BN_CTX_new();
      if (!ctx)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
            return -1;
      }
      BN_CTX_start(ctx);
      order = BN_CTX_get(ctx);      
      u1    = BN_CTX_get(ctx);
      u2    = BN_CTX_get(ctx);
      m     = BN_CTX_get(ctx);
      X     = BN_CTX_get(ctx);
      if (!X)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
            goto err;
      }
      
      if (!EC_GROUP_get_order(group, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
            goto err;
      }

      if (BN_is_zero(sig->r)          || BN_is_negative(sig->r) || 
          BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s)  ||
          BN_is_negative(sig->s)      || BN_ucmp(sig->s, order) >= 0)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);
            ret = 0;    /* signature is invalid */
            goto err;
      }
      /* calculate tmp1 = inv(S) mod order */
      if (!BN_mod_inverse(u2, sig->s, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
            goto err;
      }
      /* digest -> m */
      i = BN_num_bits(order);
      /* Need to truncate digest if it is too long: first truncate whole
       * bytes.
       */
      if (8 * dgst_len > i)
            dgst_len = (i + 7)/8;
      if (!BN_bin2bn(dgst, dgst_len, m))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
            goto err;
      }
      /* If still too long truncate remaining bits with a shift */
      if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
            goto err;
      }
      /* u1 = m * tmp mod order */
      if (!BN_mod_mul(u1, m, u2, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
            goto err;
      }
      /* u2 = r * w mod q */
      if (!BN_mod_mul(u2, sig->r, u2, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
            goto err;
      }

      if ((point = EC_POINT_new(group)) == NULL)
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
            goto err;
      }
      if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
            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,
                  point, X, NULL, ctx))
            {
                  ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
                  goto err;
            }
      }
      else /* NID_X9_62_characteristic_two_field */
      {
            if (!EC_POINT_get_affine_coordinates_GF2m(group,
                  point, X, NULL, ctx))
            {
                  ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
                  goto err;
            }
      }
      
      if (!BN_nnmod(u1, X, order, ctx))
      {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
            goto err;
      }
      /*  if the signature is correct u1 is equal to sig->r */
      ret = (BN_ucmp(u1, sig->r) == 0);
err:
      BN_CTX_end(ctx);
      BN_CTX_free(ctx);
      if (point)
            EC_POINT_free(point);
      return ret;
}

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