openssl/crypto/bn/bn_mpi.c

/* crypto/bn/bn_mpi.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * 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 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 acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS 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 AUTHOR OR 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.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <stdio.h>
#include "internal/cryptlib.h"
#include "bn_lcl.h"

int BN_bn2mpi(const BIGNUM *a, unsigned char *d)
{
    int bits;
    int num = 0;
    int ext = 0;
    long l;

    bits = BN_num_bits(a);
    num = (bits + 7) / 8;
    if (bits > 0) {
        ext = ((bits & 0x07) == 0);
    }
    if (d == NULL)
        return (num + 4 + ext);

    l = num + ext;
    d[0] = (unsigned char)(l >> 24) & 0xff;
    d[1] = (unsigned char)(l >> 16) & 0xff;
    d[2] = (unsigned char)(l >> 8) & 0xff;
    d[3] = (unsigned char)(l) & 0xff;
    if (ext)
        d[4] = 0;
    num = BN_bn2bin(a, &(d[4 + ext]));
    if (a->neg)
        d[4] |= 0x80;
    return (num + 4 + ext);
}

BIGNUM *BN_mpi2bn(const unsigned char *d, int n, BIGNUM *a)
{
    long len;
    int neg = 0;

    if (n < 4) {
        BNerr(BN_F_BN_MPI2BN, BN_R_INVALID_LENGTH);
        return (NULL);
    }
    len = ((long)d[0] << 24) | ((long)d[1] << 16) | ((int)d[2] << 8) | (int)
        d[3];
    if ((len + 4) != n) {
        BNerr(BN_F_BN_MPI2BN, BN_R_ENCODING_ERROR);
        return (NULL);
    }

    if (a == NULL)
        a = BN_new();
    if (a == NULL)
        return (NULL);

    if (len == 0) {
        a->neg = 0;
        a->top = 0;
        return (a);
    }
    d += 4;
    if ((*d) & 0x80)
        neg = 1;
    if (BN_bin2bn(d, (int)len, a) == NULL)
        return (NULL);
    a->neg = neg;
    if (neg) {
        BN_clear_bit(a, BN_num_bits(a) - 1);
    }
    bn_check_top(a);
    return (a);
}