1 /*
2 * Copyright (c) 2015-2022, Arm Limited and Contributors. All rights reserved.
3 *
4 * SPDX-License-Identifier: BSD-3-Clause
5 */
6
7 #include <assert.h>
8 #include <stddef.h>
9 #include <string.h>
10
11 /* mbed TLS headers */
12 #include <mbedtls/gcm.h>
13 #include <mbedtls/md.h>
14 #include <mbedtls/memory_buffer_alloc.h>
15 #include <mbedtls/oid.h>
16 #include <mbedtls/platform.h>
17 #include <mbedtls/x509.h>
18
19 #include <common/debug.h>
20 #include <drivers/auth/crypto_mod.h>
21 #include <drivers/auth/mbedtls/mbedtls_common.h>
22 #include <drivers/auth/mbedtls/mbedtls_config.h>
23 #include <plat/common/platform.h>
24
25 #define LIB_NAME "mbed TLS"
26
27 #if CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \
28 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC
29 /*
30 * CRYPTO_MD_MAX_SIZE value is as per current stronger algorithm available
31 * so make sure that mbed TLS MD maximum size must be lesser than this.
32 */
33 CASSERT(CRYPTO_MD_MAX_SIZE >= MBEDTLS_MD_MAX_SIZE,
34 assert_mbedtls_md_size_overflow);
35
36 #endif /* CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \
37 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC */
38
39 /*
40 * AlgorithmIdentifier ::= SEQUENCE {
41 * algorithm OBJECT IDENTIFIER,
42 * parameters ANY DEFINED BY algorithm OPTIONAL
43 * }
44 *
45 * SubjectPublicKeyInfo ::= SEQUENCE {
46 * algorithm AlgorithmIdentifier,
47 * subjectPublicKey BIT STRING
48 * }
49 *
50 * DigestInfo ::= SEQUENCE {
51 * digestAlgorithm AlgorithmIdentifier,
52 * digest OCTET STRING
53 * }
54 */
55
56 /*
57 * Initialize the library and export the descriptor
58 */
init(void)59 static void init(void)
60 {
61 /* Initialize mbed TLS */
62 mbedtls_init();
63 }
64
65 #if CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY || \
66 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC
67 /*
68 * Verify a signature.
69 *
70 * Parameters are passed using the DER encoding format following the ASN.1
71 * structures detailed above.
72 */
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)73 static int verify_signature(void *data_ptr, unsigned int data_len,
74 void *sig_ptr, unsigned int sig_len,
75 void *sig_alg, unsigned int sig_alg_len,
76 void *pk_ptr, unsigned int pk_len)
77 {
78 mbedtls_asn1_buf sig_oid, sig_params;
79 mbedtls_asn1_buf signature;
80 mbedtls_md_type_t md_alg;
81 mbedtls_pk_type_t pk_alg;
82 mbedtls_pk_context pk = {0};
83 int rc;
84 void *sig_opts = NULL;
85 const mbedtls_md_info_t *md_info;
86 unsigned char *p, *end;
87 unsigned char hash[MBEDTLS_MD_MAX_SIZE];
88
89 /* Get pointers to signature OID and parameters */
90 p = (unsigned char *)sig_alg;
91 end = (unsigned char *)(p + sig_alg_len);
92 rc = mbedtls_asn1_get_alg(&p, end, &sig_oid, &sig_params);
93 if (rc != 0) {
94 return CRYPTO_ERR_SIGNATURE;
95 }
96
97 /* Get the actual signature algorithm (MD + PK) */
98 rc = mbedtls_x509_get_sig_alg(&sig_oid, &sig_params, &md_alg, &pk_alg, &sig_opts);
99 if (rc != 0) {
100 return CRYPTO_ERR_SIGNATURE;
101 }
102
103 /* Parse the public key */
104 mbedtls_pk_init(&pk);
105 p = (unsigned char *)pk_ptr;
106 end = (unsigned char *)(p + pk_len);
107 rc = mbedtls_pk_parse_subpubkey(&p, end, &pk);
108 if (rc != 0) {
109 rc = CRYPTO_ERR_SIGNATURE;
110 goto end2;
111 }
112
113 /* Get the signature (bitstring) */
114 p = (unsigned char *)sig_ptr;
115 end = (unsigned char *)(p + sig_len);
116 signature.tag = *p;
117 rc = mbedtls_asn1_get_bitstring_null(&p, end, &signature.len);
118 if (rc != 0) {
119 rc = CRYPTO_ERR_SIGNATURE;
120 goto end1;
121 }
122 signature.p = p;
123
124 /* Calculate the hash of the data */
125 md_info = mbedtls_md_info_from_type(md_alg);
126 if (md_info == NULL) {
127 rc = CRYPTO_ERR_SIGNATURE;
128 goto end1;
129 }
130 p = (unsigned char *)data_ptr;
131 rc = mbedtls_md(md_info, p, data_len, hash);
132 if (rc != 0) {
133 rc = CRYPTO_ERR_SIGNATURE;
134 goto end1;
135 }
136
137 /* Verify the signature */
138 rc = mbedtls_pk_verify_ext(pk_alg, sig_opts, &pk, md_alg, hash,
139 mbedtls_md_get_size(md_info),
140 signature.p, signature.len);
141 if (rc != 0) {
142 rc = CRYPTO_ERR_SIGNATURE;
143 goto end1;
144 }
145
146 /* Signature verification success */
147 rc = CRYPTO_SUCCESS;
148
149 end1:
150 mbedtls_pk_free(&pk);
151 end2:
152 mbedtls_free(sig_opts);
153 return rc;
154 }
155
156 /*
157 * Match a hash
158 *
159 * Digest info is passed in DER format following the ASN.1 structure detailed
160 * above.
161 */
verify_hash(void * data_ptr,unsigned int data_len,void * digest_info_ptr,unsigned int digest_info_len)162 static int verify_hash(void *data_ptr, unsigned int data_len,
163 void *digest_info_ptr, unsigned int digest_info_len)
164 {
165 mbedtls_asn1_buf hash_oid, params;
166 mbedtls_md_type_t md_alg;
167 const mbedtls_md_info_t *md_info;
168 unsigned char *p, *end, *hash;
169 unsigned char data_hash[MBEDTLS_MD_MAX_SIZE];
170 size_t len;
171 int rc;
172
173 /* Digest info should be an MBEDTLS_ASN1_SEQUENCE */
174 p = (unsigned char *)digest_info_ptr;
175 end = p + digest_info_len;
176 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_CONSTRUCTED |
177 MBEDTLS_ASN1_SEQUENCE);
178 if (rc != 0) {
179 return CRYPTO_ERR_HASH;
180 }
181
182 /* Get the hash algorithm */
183 rc = mbedtls_asn1_get_alg(&p, end, &hash_oid, ¶ms);
184 if (rc != 0) {
185 return CRYPTO_ERR_HASH;
186 }
187
188 rc = mbedtls_oid_get_md_alg(&hash_oid, &md_alg);
189 if (rc != 0) {
190 return CRYPTO_ERR_HASH;
191 }
192
193 md_info = mbedtls_md_info_from_type(md_alg);
194 if (md_info == NULL) {
195 return CRYPTO_ERR_HASH;
196 }
197
198 /* Hash should be octet string type */
199 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING);
200 if (rc != 0) {
201 return CRYPTO_ERR_HASH;
202 }
203
204 /* Length of hash must match the algorithm's size */
205 if (len != mbedtls_md_get_size(md_info)) {
206 return CRYPTO_ERR_HASH;
207 }
208 hash = p;
209
210 /* Calculate the hash of the data */
211 p = (unsigned char *)data_ptr;
212 rc = mbedtls_md(md_info, p, data_len, data_hash);
213 if (rc != 0) {
214 return CRYPTO_ERR_HASH;
215 }
216
217 /* Compare values */
218 rc = memcmp(data_hash, hash, mbedtls_md_get_size(md_info));
219 if (rc != 0) {
220 return CRYPTO_ERR_HASH;
221 }
222
223 return CRYPTO_SUCCESS;
224 }
225 #endif /* CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY || \
226 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC */
227
228 #if CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \
229 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC
230 /*
231 * Map a generic crypto message digest algorithm to the corresponding macro used
232 * by Mbed TLS.
233 */
md_type(enum crypto_md_algo algo)234 static inline mbedtls_md_type_t md_type(enum crypto_md_algo algo)
235 {
236 switch (algo) {
237 case CRYPTO_MD_SHA512:
238 return MBEDTLS_MD_SHA512;
239 case CRYPTO_MD_SHA384:
240 return MBEDTLS_MD_SHA384;
241 case CRYPTO_MD_SHA256:
242 return MBEDTLS_MD_SHA256;
243 default:
244 /* Invalid hash algorithm. */
245 return MBEDTLS_MD_NONE;
246 }
247 }
248
249 /*
250 * Calculate a hash
251 *
252 * output points to the computed hash
253 */
calc_hash(enum crypto_md_algo md_algo,void * data_ptr,unsigned int data_len,unsigned char output[CRYPTO_MD_MAX_SIZE])254 static int calc_hash(enum crypto_md_algo md_algo, void *data_ptr,
255 unsigned int data_len,
256 unsigned char output[CRYPTO_MD_MAX_SIZE])
257 {
258 const mbedtls_md_info_t *md_info;
259
260 md_info = mbedtls_md_info_from_type(md_type(md_algo));
261 if (md_info == NULL) {
262 return CRYPTO_ERR_HASH;
263 }
264
265 /*
266 * Calculate the hash of the data, it is safe to pass the
267 * 'output' hash buffer pointer considering its size is always
268 * bigger than or equal to MBEDTLS_MD_MAX_SIZE.
269 */
270 return mbedtls_md(md_info, data_ptr, data_len, output);
271 }
272 #endif /* CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \
273 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC */
274
275 #if TF_MBEDTLS_USE_AES_GCM
276 /*
277 * Stack based buffer allocation for decryption operation. It could
278 * be configured to balance stack usage vs execution speed.
279 */
280 #define DEC_OP_BUF_SIZE 128
281
aes_gcm_decrypt(void * data_ptr,size_t len,const void * key,unsigned int key_len,const void * iv,unsigned int iv_len,const void * tag,unsigned int tag_len)282 static int aes_gcm_decrypt(void *data_ptr, size_t len, const void *key,
283 unsigned int key_len, const void *iv,
284 unsigned int iv_len, const void *tag,
285 unsigned int tag_len)
286 {
287 mbedtls_gcm_context ctx;
288 mbedtls_cipher_id_t cipher = MBEDTLS_CIPHER_ID_AES;
289 unsigned char buf[DEC_OP_BUF_SIZE];
290 unsigned char tag_buf[CRYPTO_MAX_TAG_SIZE];
291 unsigned char *pt = data_ptr;
292 size_t dec_len;
293 int diff, i, rc;
294
295 mbedtls_gcm_init(&ctx);
296
297 rc = mbedtls_gcm_setkey(&ctx, cipher, key, key_len * 8);
298 if (rc != 0) {
299 rc = CRYPTO_ERR_DECRYPTION;
300 goto exit_gcm;
301 }
302
303 rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len, NULL, 0);
304 if (rc != 0) {
305 rc = CRYPTO_ERR_DECRYPTION;
306 goto exit_gcm;
307 }
308
309 while (len > 0) {
310 dec_len = MIN(sizeof(buf), len);
311
312 rc = mbedtls_gcm_update(&ctx, dec_len, pt, buf);
313 if (rc != 0) {
314 rc = CRYPTO_ERR_DECRYPTION;
315 goto exit_gcm;
316 }
317
318 memcpy(pt, buf, dec_len);
319 pt += dec_len;
320 len -= dec_len;
321 }
322
323 rc = mbedtls_gcm_finish(&ctx, tag_buf, sizeof(tag_buf));
324 if (rc != 0) {
325 rc = CRYPTO_ERR_DECRYPTION;
326 goto exit_gcm;
327 }
328
329 /* Check tag in "constant-time" */
330 for (diff = 0, i = 0; i < tag_len; i++)
331 diff |= ((const unsigned char *)tag)[i] ^ tag_buf[i];
332
333 if (diff != 0) {
334 rc = CRYPTO_ERR_DECRYPTION;
335 goto exit_gcm;
336 }
337
338 /* GCM decryption success */
339 rc = CRYPTO_SUCCESS;
340
341 exit_gcm:
342 mbedtls_gcm_free(&ctx);
343 return rc;
344 }
345
346 /*
347 * Authenticated decryption of an image
348 */
auth_decrypt(enum crypto_dec_algo dec_algo,void * data_ptr,size_t len,const void * key,unsigned int key_len,unsigned int key_flags,const void * iv,unsigned int iv_len,const void * tag,unsigned int tag_len)349 static int auth_decrypt(enum crypto_dec_algo dec_algo, void *data_ptr,
350 size_t len, const void *key, unsigned int key_len,
351 unsigned int key_flags, const void *iv,
352 unsigned int iv_len, const void *tag,
353 unsigned int tag_len)
354 {
355 int rc;
356
357 assert((key_flags & ENC_KEY_IS_IDENTIFIER) == 0);
358
359 switch (dec_algo) {
360 case CRYPTO_GCM_DECRYPT:
361 rc = aes_gcm_decrypt(data_ptr, len, key, key_len, iv, iv_len,
362 tag, tag_len);
363 if (rc != 0)
364 return rc;
365 break;
366 default:
367 return CRYPTO_ERR_DECRYPTION;
368 }
369
370 return CRYPTO_SUCCESS;
371 }
372 #endif /* TF_MBEDTLS_USE_AES_GCM */
373
374 /*
375 * Register crypto library descriptor
376 */
377 #if CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC
378 #if TF_MBEDTLS_USE_AES_GCM
379 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash,
380 auth_decrypt);
381 #else
382 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash,
383 NULL);
384 #endif
385 #elif CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY
386 #if TF_MBEDTLS_USE_AES_GCM
387 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash,
388 auth_decrypt);
389 #else
390 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL);
391 #endif
392 #elif CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY
393 REGISTER_CRYPTO_LIB(LIB_NAME, init, calc_hash);
394 #endif /* CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC */
395