crypto/bn/bn_mpi.c

   1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   2  * All rights reserved.
   3  *
   4  * This package is an SSL implementation written
   5  * by Eric Young (eay@cryptsoft.com).
   6  * The implementation was written so as to conform with Netscapes SSL.
   7  *
   8  * This library is free for commercial and non-commercial use as long as
   9  * the following conditions are aheared to.  The following conditions
  10  * apply to all code found in this distribution, be it the RC4, RSA,
  11  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  12  * included with this distribution is covered by the same copyright terms
  13  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  14  *
  15  * Copyright remains Eric Young's, and as such any Copyright notices in
  16  * the code are not to be removed.
  17  * If this package is used in a product, Eric Young should be given attribution
  18  * as the author of the parts of the library used.
  19  * This can be in the form of a textual message at program startup or
  20  * in documentation (online or textual) provided with the package.
  21  *
  22  * Redistribution and use in source and binary forms, with or without
  23  * modification, are permitted provided that the following conditions
  24  * are met:
  25  * 1. Redistributions of source code must retain the copyright
  26  *    notice, this list of conditions and the following disclaimer.
  27  * 2. Redistributions in binary form must reproduce the above copyright
  28  *    notice, this list of conditions and the following disclaimer in the
  29  *    documentation and/or other materials provided with the distribution.
  30  * 3. All advertising materials mentioning features or use of this software
  31  *    must display the following acknowledgement:
  32  *    "This product includes cryptographic software written by
  33  *     Eric Young (eay@cryptsoft.com)"
  34  *    The word 'cryptographic' can be left out if the rouines from the library
  35  *    being used are not cryptographic related :-).
  36  * 4. If you include any Windows specific code (or a derivative thereof) from
  37  *    the apps directory (application code) you must include an acknowledgement:
  38  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  39  *
  40  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  41  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  43  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  44  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  45  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  46  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  48  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  49  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  50  * SUCH DAMAGE.
  51  *
  52  * The licence and distribution terms for any publically available version or
  53  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  54  * copied and put under another distribution licence
  55  * [including the GNU Public Licence.]
  56  */
  57
  58 #include <stdio.h>
  59 #include "internal/cryptlib.h"
  60 #include "bn_lcl.h"
  61
  62 int BN_bn2mpi(const BIGNUM *a, unsigned char *d)
  63 {
  64     int bits;
  65     int num = 0;
  66     int ext = 0;
  67     long l;
  68
  69     bits = BN_num_bits(a);
  70     num = (bits + 7) / 8;
  71     if (bits > 0) {
  72         ext = ((bits & 0x07) == 0);
  73     }
  74     if (d == NULL)
  75         return (num + 4 + ext);
  76
  77     l = num + ext;
  78     d[0] = (unsigned char)(l >> 24) & 0xff;
  79     d[1] = (unsigned char)(l >> 16) & 0xff;
  80     d[2] = (unsigned char)(l >> 8) & 0xff;
  81     d[3] = (unsigned char)(l) & 0xff;
  82     if (ext)
  83         d[4] = 0;
  84     num = BN_bn2bin(a, &(d[4 + ext]));
  85     if (a->neg)
  86         d[4] |= 0x80;
  87     return (num + 4 + ext);
  88 }
  89
  90 BIGNUM *BN_mpi2bn(const unsigned char *d, int n, BIGNUM *a)
  91 {
  92     long len;
  93     int neg = 0;
  94
  95     if (n < 4) {
  96         BNerr(BN_F_BN_MPI2BN, BN_R_INVALID_LENGTH);
  97         return NULL;
  98     }
  99     len = ((long)d[0] << 24) | ((long)d[1] << 16) | ((int)d[2] << 8) | (int)
 100         d[3];
 101     if ((len + 4) != n) {
 102         BNerr(BN_F_BN_MPI2BN, BN_R_ENCODING_ERROR);
 103         return NULL;
 104     }
 105
 106     if (a == NULL)
 107         a = BN_new();
 108     if (a == NULL)
 109         return NULL;
 110
 111     if (len == 0) {
 112         a->neg = 0;
 113         a->top = 0;
 114         return a;
 115     }
 116     d += 4;
 117     if ((*d) & 0x80)
 118         neg = 1;
 119     if (BN_bin2bn(d, (int)len, a) == NULL) {
 120         BN_free(a);
 121         return NULL;
 122     }
 123     a->neg = neg;
 124     if (neg) {
 125         BN_clear_bit(a, BN_num_bits(a) - 1);
 126     }
 127     bn_check_top(a);
 128     return a;
 129 }