bn_mpi.c revision 296465 
1/* crypto/bn/bn_mpi.c */
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#include "cryptlib.h"
61#include "bn_lcl.h"
62
63int BN_bn2mpi(const BIGNUM *a, unsigned char *d)
64{
65    int bits;
66    int num = 0;
67    int ext = 0;
68    long l;
69
70    bits = BN_num_bits(a);
71    num = (bits + 7) / 8;
72    if (bits > 0) {
73        ext = ((bits & 0x07) == 0);
74    }
75    if (d == NULL)
76        return (num + 4 + ext);
77
78    l = num + ext;
79    d[0] = (unsigned char)(l >> 24) & 0xff;
80    d[1] = (unsigned char)(l >> 16) & 0xff;
81    d[2] = (unsigned char)(l >> 8) & 0xff;
82    d[3] = (unsigned char)(l) & 0xff;
83    if (ext)
84        d[4] = 0;
85    num = BN_bn2bin(a, &(d[4 + ext]));
86    if (a->neg)
87        d[4] |= 0x80;
88    return (num + 4 + ext);
89}
90
91BIGNUM *BN_mpi2bn(const unsigned char *d, int n, BIGNUM *a)
92{
93    long len;
94    int neg = 0;
95
96    if (n < 4) {
97        BNerr(BN_F_BN_MPI2BN, BN_R_INVALID_LENGTH);
98        return (NULL);
99    }
100    len = ((long)d[0] << 24) | ((long)d[1] << 16) | ((int)d[2] << 8) | (int)
101        d[3];
102    if ((len + 4) != n) {
103        BNerr(BN_F_BN_MPI2BN, BN_R_ENCODING_ERROR);
104        return (NULL);
105    }
106
107    if (a == NULL)
108        a = BN_new();
109    if (a == NULL)
110        return (NULL);
111
112    if (len == 0) {
113        a->neg = 0;
114        a->top = 0;
115        return (a);
116    }
117    d += 4;
118    if ((*d) & 0x80)
119        neg = 1;
120    if (BN_bin2bn(d, (int)len, a) == NULL)
121        return (NULL);
122    a->neg = neg;
123    if (neg) {
124        BN_clear_bit(a, BN_num_bits(a) - 1);
125    }
126    bn_check_top(a);
127    return (a);
128}
129