1/*
2 * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License").  You may not use
5 * this file except in compliance with the License.  You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include <stdio.h>
11#include "internal/cryptlib.h"
12#include "bn_local.h"
13
14int BN_bn2mpi(const BIGNUM *a, unsigned char *d)
15{
16    int bits;
17    int num = 0;
18    int ext = 0;
19    long l;
20
21    bits = BN_num_bits(a);
22    num = (bits + 7) / 8;
23    if (bits > 0) {
24        ext = ((bits & 0x07) == 0);
25    }
26    if (d == NULL)
27        return (num + 4 + ext);
28
29    l = num + ext;
30    d[0] = (unsigned char)(l >> 24) & 0xff;
31    d[1] = (unsigned char)(l >> 16) & 0xff;
32    d[2] = (unsigned char)(l >> 8) & 0xff;
33    d[3] = (unsigned char)(l) & 0xff;
34    if (ext)
35        d[4] = 0;
36    num = BN_bn2bin(a, &(d[4 + ext]));
37    if (a->neg)
38        d[4] |= 0x80;
39    return (num + 4 + ext);
40}
41
42BIGNUM *BN_mpi2bn(const unsigned char *d, int n, BIGNUM *ain)
43{
44    long len;
45    int neg = 0;
46    BIGNUM *a = NULL;
47
48    if (n < 4 || (d[0] & 0x80) != 0) {
49        ERR_raise(ERR_LIB_BN, BN_R_INVALID_LENGTH);
50        return NULL;
51    }
52    len = ((long)d[0] << 24) | ((long)d[1] << 16) | ((int)d[2] << 8) | (int)
53        d[3];
54    if ((len + 4) != n) {
55        ERR_raise(ERR_LIB_BN, BN_R_ENCODING_ERROR);
56        return NULL;
57    }
58
59    if (ain == NULL)
60        a = BN_new();
61    else
62        a = ain;
63
64    if (a == NULL)
65        return NULL;
66
67    if (len == 0) {
68        a->neg = 0;
69        a->top = 0;
70        return a;
71    }
72    d += 4;
73    if ((*d) & 0x80)
74        neg = 1;
75    if (BN_bin2bn(d, (int)len, a) == NULL) {
76        if (ain == NULL)
77            BN_free(a);
78        return NULL;
79    }
80    a->neg = neg;
81    if (neg) {
82        BN_clear_bit(a, BN_num_bits(a) - 1);
83    }
84    bn_check_top(a);
85    return a;
86}
87