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