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