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x_bignum.c
/* x_bignum.c */
/* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
 * project 2000.
 */
/* ====================================================================
 * Copyright (c) 2000 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
 *    licensing@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 <stdio.h>
#include "cryptlib.h"
#include <openssl/asn1t.h>
#include <openssl/bn.h>

/* Custom primitive type for BIGNUM handling. This reads in an ASN1_INTEGER as a
 * BIGNUM directly. Currently it ignores the sign which isn't a problem since all
 * BIGNUMs used are non negative and anything that looks negative is normally due
 * to an encoding error.
 */

#define BN_SENSITIVE    1

static int bn_new(ASN1_VALUE **pval, const ASN1_ITEM *it);
static void bn_free(ASN1_VALUE **pval, const ASN1_ITEM *it);

static int bn_i2c(ASN1_VALUE **pval, unsigned char *cont, int *putype, const ASN1_ITEM *it);
static int bn_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len, int utype, char *free_cont, const ASN1_ITEM *it);

static ASN1_PRIMITIVE_FUNCS bignum_pf = {
      NULL, 0,
      bn_new,
      bn_free,
      0,
      bn_c2i,
      bn_i2c
};

ASN1_ITEM_start(BIGNUM)
      ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &bignum_pf, 0, "BIGNUM"
ASN1_ITEM_end(BIGNUM)

ASN1_ITEM_start(CBIGNUM)
      ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &bignum_pf, BN_SENSITIVE, "BIGNUM"
ASN1_ITEM_end(CBIGNUM)

static int bn_new(ASN1_VALUE **pval, const ASN1_ITEM *it)
{
      *pval = (ASN1_VALUE *)BN_new();
      if(*pval) return 1;
      else return 0;
}

static void bn_free(ASN1_VALUE **pval, const ASN1_ITEM *it)
{
      if(!*pval) return;
      if(it->size & BN_SENSITIVE) BN_clear_free((BIGNUM *)*pval);
      else BN_free((BIGNUM *)*pval);
      *pval = NULL;
}

static int bn_i2c(ASN1_VALUE **pval, unsigned char *cont, int *putype, const ASN1_ITEM *it)
{
      BIGNUM *bn;
      int pad;
      if(!*pval) return -1;
      bn = (BIGNUM *)*pval;
      /* If MSB set in an octet we need a padding byte */
      if(BN_num_bits(bn) & 0x7) pad = 0;
      else pad = 1;
      if(cont) {
            if(pad) *cont++ = 0;
            BN_bn2bin(bn, cont);
      }
      return pad + BN_num_bytes(bn);
}

static int bn_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
              int utype, char *free_cont, const ASN1_ITEM *it)
{
      BIGNUM *bn;
      if(!*pval) bn_new(pval, it);
      bn  = (BIGNUM *)*pval;
      if(!BN_bin2bn(cont, len, bn)) {
            bn_free(pval, it);
            return 0;
      }
      return 1;
}



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