xref: /openssl/crypto/asn1/x_bignum.c (revision 12a765a5)
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 
24 static int bn_new(ASN1_VALUE **pval, const ASN1_ITEM *it);
25 static int bn_secure_new(ASN1_VALUE **pval, const ASN1_ITEM *it);
26 static void bn_free(ASN1_VALUE **pval, const ASN1_ITEM *it);
27 
28 static int bn_i2c(const ASN1_VALUE **pval, unsigned char *cont, int *putype,
29                   const ASN1_ITEM *it);
30 static int bn_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
31                   int utype, char *free_cont, const ASN1_ITEM *it);
32 static int bn_secure_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
33                          int utype, char *free_cont, const ASN1_ITEM *it);
34 static int bn_print(BIO *out, const ASN1_VALUE **pval, const ASN1_ITEM *it,
35                     int indent, const ASN1_PCTX *pctx);
36 
37 static 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 
47 static 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 
ASN1_ITEM_start(BIGNUM)57 ASN1_ITEM_start(BIGNUM)
58         ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &bignum_pf, 0, "BIGNUM"
59 ASN1_ITEM_end(BIGNUM)
60 
61 ASN1_ITEM_start(CBIGNUM)
62         ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &cbignum_pf, BN_SENSITIVE, "CBIGNUM"
63 ASN1_ITEM_end(CBIGNUM)
64 
65 static 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 
bn_secure_new(ASN1_VALUE ** pval,const ASN1_ITEM * it)74 static 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 
bn_free(ASN1_VALUE ** pval,const ASN1_ITEM * it)83 static 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 
bn_i2c(const ASN1_VALUE ** pval,unsigned char * cont,int * putype,const ASN1_ITEM * it)94 static 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 
bn_c2i(ASN1_VALUE ** pval,const unsigned char * cont,int len,int utype,char * free_cont,const ASN1_ITEM * it)115 static 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 
bn_secure_c2i(ASN1_VALUE ** pval,const unsigned char * cont,int len,int utype,char * free_cont,const ASN1_ITEM * it)130 static 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 
bn_print(BIO * out,const ASN1_VALUE ** pval,const ASN1_ITEM * it,int indent,const ASN1_PCTX * pctx)149 static 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