lib/libcrypto/bn/bn_mpi.c

   1 /* $OpenBSD: bn_mpi.c,v 1.8 2017/01/29 17:49:22 beck Exp $ */
   2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   3  * All rights reserved.
   4  *
   5  * This package is an SSL implementation written
   6  * by Eric Young (eay@cryptsoft.com).
   7  * The implementation was written so as to conform with Netscapes SSL.
   8  *
   9  * This library is free for commercial and non-commercial use as long as
  10  * the following conditions are aheared to.  The following conditions
  11  * apply to all code found in this distribution, be it the RC4, RSA,
  12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  13  * included with this distribution is covered by the same copyright terms
  14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  15  *
  16  * Copyright remains Eric Young's, and as such any Copyright notices in
  17  * the code are not to be removed.
  18  * If this package is used in a product, Eric Young should be given attribution
  19  * as the author of the parts of the library used.
  20  * This can be in the form of a textual message at program startup or
  21  * in documentation (online or textual) provided with the package.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 3. All advertising materials mentioning features or use of this software
  32  *    must display the following acknowledgement:
  33  *    "This product includes cryptographic software written by
  34  *     Eric Young (eay@cryptsoft.com)"
  35  *    The word 'cryptographic' can be left out if the rouines from the library
  36  *    being used are not cryptographic related :-).
  37  * 4. If you include any Windows specific code (or a derivative thereof) from
  38  *    the apps directory (application code) you must include an acknowledgement:
  39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  * The licence and distribution terms for any publically available version or
  54  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  55  * copied and put under another distribution licence
  56  * [including the GNU Public Licence.]
  57  */
  58
  59 #include <stdio.h>
  60
  61 #include <openssl/err.h>
  62
  63 #include "bn_lcl.h"
  64
  65 int
  66 BN_bn2mpi(const BIGNUM *a, unsigned char *d)
  67 {
  68         int bits;
  69         int num = 0;
  70         int ext = 0;
  71         long l;
  72
  73         bits = BN_num_bits(a);
  74         num = (bits + 7) / 8;
  75         if (bits > 0) {
  76                 ext = ((bits & 0x07) == 0);
  77         }
  78         if (d == NULL)
  79                 return (num + 4 + ext);
  80
  81         l = num + ext;
  82         d[0] = (unsigned char)(l >> 24) & 0xff;
  83         d[1] = (unsigned char)(l >> 16) & 0xff;
  84         d[2] = (unsigned char)(l >> 8) & 0xff;
  85         d[3] = (unsigned char)(l) & 0xff;
  86         if (ext)
  87                 d[4] = 0;
  88         num = BN_bn2bin(a, &(d[4 + ext]));
  89         if (a->neg)
  90                 d[4] |= 0x80;
  91         return (num + 4 + ext);
  92 }
  93
  94 BIGNUM *
  95 BN_mpi2bn(const unsigned char *d, int n, BIGNUM *a)
  96 {
  97         long len;
  98         int neg = 0;
  99
 100         if (n < 4) {
 101                 BNerror(BN_R_INVALID_LENGTH);
 102                 return (NULL);
 103         }
 104         len = ((long)d[0] << 24) | ((long)d[1] << 16) | ((int)d[2] << 8) |
 105             (int)d[3];
 106         if ((len + 4) != n) {
 107                 BNerror(BN_R_ENCODING_ERROR);
 108                 return (NULL);
 109         }
 110
 111         if (a == NULL)
 112                 a = BN_new();
 113         if (a == NULL)
 114                 return (NULL);
 115
 116         if (len == 0) {
 117                 a->neg = 0;
 118                 a->top = 0;
 119                 return (a);
 120         }
 121         d += 4;
 122         if ((*d) & 0x80)
 123                 neg = 1;
 124         if (BN_bin2bn(d, (int)len, a) == NULL)
 125                 return (NULL);
 126         a->neg = neg;
 127         if (neg) {
 128                 BN_clear_bit(a, BN_num_bits(a) - 1);
 129         }
 130         bn_check_top(a);
 131         return (a);
 132 }