1/*
2 * Copyright 2000-2016 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 <openssl/asn1t.h>
13#include <openssl/bn.h>
14
15/*
16 * Custom primitive type for BIGNUM handling. This reads in an ASN1_INTEGER
17 * as a BIGNUM directly. Currently it ignores the sign which isn't a problem
18 * since all BIGNUMs used are non negative and anything that looks negative
19 * is normally due to an encoding error.
20 */
21
22#define BN_SENSITIVE    1
23
24static int bn_new(ASN1_VALUE **pval, const ASN1_ITEM *it);
25static int bn_secure_new(ASN1_VALUE **pval, const ASN1_ITEM *it);
26static void bn_free(ASN1_VALUE **pval, const ASN1_ITEM *it);
27
28static int bn_i2c(const ASN1_VALUE **pval, unsigned char *cont, int *putype,
29                  const ASN1_ITEM *it);
30static int bn_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
31                  int utype, char *free_cont, const ASN1_ITEM *it);
32static int bn_secure_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
33                         int utype, char *free_cont, const ASN1_ITEM *it);
34static int bn_print(BIO *out, const ASN1_VALUE **pval, const ASN1_ITEM *it,
35                    int indent, const ASN1_PCTX *pctx);
36
37static ASN1_PRIMITIVE_FUNCS bignum_pf = {
38    NULL, 0,
39    bn_new,
40    bn_free,
41    0,
42    bn_c2i,
43    bn_i2c,
44    bn_print
45};
46
47static ASN1_PRIMITIVE_FUNCS cbignum_pf = {
48    NULL, 0,
49    bn_secure_new,
50    bn_free,
51    0,
52    bn_secure_c2i,
53    bn_i2c,
54    bn_print
55};
56
57ASN1_ITEM_start(BIGNUM)
58        ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &bignum_pf, 0, "BIGNUM"
59ASN1_ITEM_end(BIGNUM)
60
61ASN1_ITEM_start(CBIGNUM)
62        ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &cbignum_pf, BN_SENSITIVE, "CBIGNUM"
63ASN1_ITEM_end(CBIGNUM)
64
65static int bn_new(ASN1_VALUE **pval, const ASN1_ITEM *it)
66{
67    *pval = (ASN1_VALUE *)BN_new();
68    if (*pval != NULL)
69        return 1;
70    else
71        return 0;
72}
73
74static int bn_secure_new(ASN1_VALUE **pval, const ASN1_ITEM *it)
75{
76    *pval = (ASN1_VALUE *)BN_secure_new();
77    if (*pval != NULL)
78        return 1;
79    else
80        return 0;
81}
82
83static void bn_free(ASN1_VALUE **pval, const ASN1_ITEM *it)
84{
85    if (*pval == NULL)
86        return;
87    if (it->size & BN_SENSITIVE)
88        BN_clear_free((BIGNUM *)*pval);
89    else
90        BN_free((BIGNUM *)*pval);
91    *pval = NULL;
92}
93
94static int bn_i2c(const ASN1_VALUE **pval, unsigned char *cont, int *putype,
95                  const ASN1_ITEM *it)
96{
97    BIGNUM *bn;
98    int pad;
99    if (*pval == NULL)
100        return -1;
101    bn = (BIGNUM *)*pval;
102    /* If MSB set in an octet we need a padding byte */
103    if (BN_num_bits(bn) & 0x7)
104        pad = 0;
105    else
106        pad = 1;
107    if (cont) {
108        if (pad)
109            *cont++ = 0;
110        BN_bn2bin(bn, cont);
111    }
112    return pad + BN_num_bytes(bn);
113}
114
115static int bn_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
116                  int utype, char *free_cont, const ASN1_ITEM *it)
117{
118    BIGNUM *bn;
119
120    if (*pval == NULL && !bn_new(pval, it))
121        return 0;
122    bn = (BIGNUM *)*pval;
123    if (!BN_bin2bn(cont, len, bn)) {
124        bn_free(pval, it);
125        return 0;
126    }
127    return 1;
128}
129
130static int bn_secure_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
131                         int utype, char *free_cont, const ASN1_ITEM *it)
132{
133    int ret;
134    BIGNUM *bn;
135
136    if (*pval == NULL && !bn_secure_new(pval, it))
137        return 0;
138
139    ret = bn_c2i(pval, cont, len, utype, free_cont, it);
140    if (!ret)
141        return 0;
142
143    /* Set constant-time flag for all secure BIGNUMS */
144    bn = (BIGNUM *)*pval;
145    BN_set_flags(bn, BN_FLG_CONSTTIME);
146    return ret;
147}
148
149static int bn_print(BIO *out, const ASN1_VALUE **pval, const ASN1_ITEM *it,
150                    int indent, const ASN1_PCTX *pctx)
151{
152    if (!BN_print(out, *(BIGNUM **)pval))
153        return 0;
154    if (BIO_puts(out, "\n") <= 0)
155        return 0;
156    return 1;
157}
158