1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
/*
* Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <crypto_mod.h>
#include <debug.h>
#include <mbedtls_common.h>
#include <mbedtls_config.h>
#include <stddef.h>
#include <string.h>
/* mbed TLS headers */
#include <mbedtls/md.h>
#include <mbedtls/memory_buffer_alloc.h>
#include <mbedtls/oid.h>
#include <mbedtls/platform.h>
#define LIB_NAME "mbed TLS"
/*
* AlgorithmIdentifier ::= SEQUENCE {
* algorithm OBJECT IDENTIFIER,
* parameters ANY DEFINED BY algorithm OPTIONAL
* }
*
* SubjectPublicKeyInfo ::= SEQUENCE {
* algorithm AlgorithmIdentifier,
* subjectPublicKey BIT STRING
* }
*
* DigestInfo ::= SEQUENCE {
* digestAlgorithm AlgorithmIdentifier,
* digest OCTET STRING
* }
*/
/*
* Initialize the library and export the descriptor
*/
static void init(void)
{
/* Initialize mbed TLS */
mbedtls_init();
}
/*
* Verify a signature.
*
* Parameters are passed using the DER encoding format following the ASN.1
* structures detailed above.
*/
static int verify_signature(void *data_ptr, unsigned int data_len,
void *sig_ptr, unsigned int sig_len,
void *sig_alg, unsigned int sig_alg_len,
void *pk_ptr, unsigned int pk_len)
{
mbedtls_asn1_buf sig_oid, sig_params;
mbedtls_asn1_buf signature;
mbedtls_md_type_t md_alg;
mbedtls_pk_type_t pk_alg;
mbedtls_pk_context pk = {0};
int rc;
void *sig_opts = NULL;
const mbedtls_md_info_t *md_info;
unsigned char *p, *end;
unsigned char hash[MBEDTLS_MD_MAX_SIZE];
/* Get pointers to signature OID and parameters */
p = (unsigned char *)sig_alg;
end = (unsigned char *)(p + sig_alg_len);
rc = mbedtls_asn1_get_alg(&p, end, &sig_oid, &sig_params);
if (rc != 0) {
return CRYPTO_ERR_SIGNATURE;
}
/* Get the actual signature algorithm (MD + PK) */
rc = mbedtls_x509_get_sig_alg(&sig_oid, &sig_params, &md_alg, &pk_alg, &sig_opts);
if (rc != 0) {
return CRYPTO_ERR_SIGNATURE;
}
/* Parse the public key */
mbedtls_pk_init(&pk);
p = (unsigned char *)pk_ptr;
end = (unsigned char *)(p + pk_len);
rc = mbedtls_pk_parse_subpubkey(&p, end, &pk);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end2;
}
/* Get the signature (bitstring) */
p = (unsigned char *)sig_ptr;
end = (unsigned char *)(p + sig_len);
signature.tag = *p;
rc = mbedtls_asn1_get_bitstring_null(&p, end, &signature.len);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
signature.p = p;
/* Calculate the hash of the data */
md_info = mbedtls_md_info_from_type(md_alg);
if (md_info == NULL) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
p = (unsigned char *)data_ptr;
rc = mbedtls_md(md_info, p, data_len, hash);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
/* Verify the signature */
rc = mbedtls_pk_verify_ext(pk_alg, sig_opts, &pk, md_alg, hash,
mbedtls_md_get_size(md_info),
signature.p, signature.len);
if (rc != 0) {
rc = CRYPTO_ERR_SIGNATURE;
goto end1;
}
/* Signature verification success */
rc = CRYPTO_SUCCESS;
end1:
mbedtls_pk_free(&pk);
end2:
mbedtls_free(sig_opts);
return rc;
}
/*
* Match a hash
*
* Digest info is passed in DER format following the ASN.1 structure detailed
* above.
*/
static int verify_hash(void *data_ptr, unsigned int data_len,
void *digest_info_ptr, unsigned int digest_info_len)
{
mbedtls_asn1_buf hash_oid, params;
mbedtls_md_type_t md_alg;
const mbedtls_md_info_t *md_info;
unsigned char *p, *end, *hash;
unsigned char data_hash[MBEDTLS_MD_MAX_SIZE];
size_t len;
int rc;
/* Digest info should be an MBEDTLS_ASN1_SEQUENCE */
p = (unsigned char *)digest_info_ptr;
end = p + digest_info_len;
rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_CONSTRUCTED |
MBEDTLS_ASN1_SEQUENCE);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
/* Get the hash algorithm */
rc = mbedtls_asn1_get_alg(&p, end, &hash_oid, ¶ms);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
rc = mbedtls_oid_get_md_alg(&hash_oid, &md_alg);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
md_info = mbedtls_md_info_from_type(md_alg);
if (md_info == NULL) {
return CRYPTO_ERR_HASH;
}
/* Hash should be octet string type */
rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
/* Length of hash must match the algorithm's size */
if (len != mbedtls_md_get_size(md_info)) {
return CRYPTO_ERR_HASH;
}
hash = p;
/* Calculate the hash of the data */
p = (unsigned char *)data_ptr;
rc = mbedtls_md(md_info, p, data_len, data_hash);
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
/* Compare values */
rc = memcmp(data_hash, hash, mbedtls_md_get_size(md_info));
if (rc != 0) {
return CRYPTO_ERR_HASH;
}
return CRYPTO_SUCCESS;
}
/*
* Register crypto library descriptor
*/
REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash);
|
