/*

 * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <stdio.h>

#include "internal/cryptlib.h"

#include "bn_local.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 *ain)

{

    long len;

    int neg = 0;

    BIGNUM *a = NULL;

    if (n < 4 || (d[0] & 0x80) != 0) {

        ERR_raise(ERR_LIB_BN, 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) {

        ERR_raise(ERR_LIB_BN, BN_R_ENCODING_ERROR);

        return NULL;

    }

    if (ain == NULL)

        a = BN_new();

    else

        a = ain;

    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) {

        if (ain == NULL)

            BN_free(a);

        return NULL;

    }

    a->neg = neg;

    if (neg) {

        BN_clear_bit(a, BN_num_bits(a) - 1);

    }

    bn_check_top(a);

    return a;

}