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
BN_bn2mpi(const BIGNUM * a,unsigned char * d)14 int 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
BN_mpi2bn(const unsigned char * d,int n,BIGNUM * ain)42 BIGNUM *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
