1 /* 2 * Copyright (c) 2023, Arm Limited. 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/version.h> 18 #include <mbedtls/x509.h> 19 #include <psa/crypto.h> 20 #include <psa/crypto_platform.h> 21 #include <psa/crypto_types.h> 22 #include <psa/crypto_values.h> 23 24 #include <common/debug.h> 25 #include <drivers/auth/crypto_mod.h> 26 #include <drivers/auth/mbedtls/mbedtls_common.h> 27 #include <plat/common/platform.h> 28 29 #define LIB_NAME "mbed TLS PSA" 30 31 #if CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 32 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 33 /* 34 * CRYPTO_MD_MAX_SIZE value is as per current stronger algorithm available 35 * so make sure that mbed TLS MD maximum size must be lesser than this. 36 */ 37 CASSERT(CRYPTO_MD_MAX_SIZE >= MBEDTLS_MD_MAX_SIZE, 38 assert_mbedtls_md_size_overflow); 39 40 #endif /* 41 * CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 42 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 43 */ 44 45 static inline psa_algorithm_t mbedtls_md_psa_alg_from_type( 46 mbedtls_md_type_t md_type) 47 { 48 assert((md_type == MBEDTLS_MD_SHA256) || 49 (md_type == MBEDTLS_MD_SHA384) || 50 (md_type == MBEDTLS_MD_SHA512)); 51 52 return PSA_ALG_CATEGORY_HASH | (psa_algorithm_t) (md_type + 0x5); 53 } 54 55 /* 56 * AlgorithmIdentifier ::= SEQUENCE { 57 * algorithm OBJECT IDENTIFIER, 58 * parameters ANY DEFINED BY algorithm OPTIONAL 59 * } 60 * 61 * SubjectPublicKeyInfo ::= SEQUENCE { 62 * algorithm AlgorithmIdentifier, 63 * subjectPublicKey BIT STRING 64 * } 65 * 66 * DigestInfo ::= SEQUENCE { 67 * digestAlgorithm AlgorithmIdentifier, 68 * digest OCTET STRING 69 * } 70 */ 71 72 /* 73 * We pretend using an external RNG (through MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG 74 * mbedTLS config option) so we need to provide an implementation of 75 * mbedtls_psa_external_get_random(). Provide a fake one, since we do not 76 * actually have any external RNG and TF-A itself doesn't engage in 77 * cryptographic operations that demands randomness. 78 */ 79 psa_status_t mbedtls_psa_external_get_random( 80 mbedtls_psa_external_random_context_t *context, 81 uint8_t *output, size_t output_size, 82 size_t *output_length) 83 { 84 return PSA_ERROR_INSUFFICIENT_ENTROPY; 85 } 86 87 /* 88 * Initialize the library and export the descriptor 89 */ 90 static void init(void) 91 { 92 /* Initialize mbed TLS */ 93 mbedtls_init(); 94 95 /* Initialise PSA mbedTLS */ 96 psa_status_t status = psa_crypto_init(); 97 98 if (status != PSA_SUCCESS) { 99 ERROR("Failed to initialize %s crypto (%d).\n", LIB_NAME, status); 100 panic(); 101 } 102 103 INFO("PSA crypto initialized successfully!\n"); 104 } 105 106 #if CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY || \ 107 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 108 109 static void construct_psa_key_alg_and_type(mbedtls_pk_type_t pk_alg, 110 mbedtls_md_type_t md_alg, 111 psa_algorithm_t *psa_alg, 112 psa_key_type_t *psa_key_type) 113 { 114 psa_algorithm_t psa_md_alg = mbedtls_md_psa_alg_from_type(md_alg); 115 116 switch (pk_alg) { 117 case MBEDTLS_PK_RSASSA_PSS: 118 *psa_alg = PSA_ALG_RSA_PSS(psa_md_alg); 119 *psa_key_type = PSA_KEY_TYPE_RSA_PUBLIC_KEY; 120 break; 121 default: 122 *psa_alg = PSA_ALG_NONE; 123 *psa_key_type = PSA_KEY_TYPE_NONE; 124 break; 125 } 126 } 127 128 /* 129 * Verify a signature. 130 * 131 * Parameters are passed using the DER encoding format following the ASN.1 132 * structures detailed above. 133 */ 134 static int verify_signature(void *data_ptr, unsigned int data_len, 135 void *sig_ptr, unsigned int sig_len, 136 void *sig_alg, unsigned int sig_alg_len, 137 void *pk_ptr, unsigned int pk_len) 138 { 139 mbedtls_asn1_buf sig_oid, sig_params; 140 mbedtls_asn1_buf signature; 141 mbedtls_md_type_t md_alg; 142 mbedtls_pk_type_t pk_alg; 143 int rc; 144 void *sig_opts = NULL; 145 unsigned char *p, *end; 146 147 /* construct PSA key algo and type */ 148 psa_status_t status = PSA_SUCCESS; 149 psa_key_attributes_t psa_key_attr = PSA_KEY_ATTRIBUTES_INIT; 150 psa_key_id_t psa_key_id = PSA_KEY_ID_NULL; 151 psa_key_type_t psa_key_type; 152 psa_algorithm_t psa_alg; 153 154 /* Get pointers to signature OID and parameters */ 155 p = (unsigned char *)sig_alg; 156 end = (unsigned char *)(p + sig_alg_len); 157 rc = mbedtls_asn1_get_alg(&p, end, &sig_oid, &sig_params); 158 if (rc != 0) { 159 return CRYPTO_ERR_SIGNATURE; 160 } 161 162 /* Get the actual signature algorithm (MD + PK) */ 163 rc = mbedtls_x509_get_sig_alg(&sig_oid, &sig_params, &md_alg, &pk_alg, &sig_opts); 164 if (rc != 0) { 165 return CRYPTO_ERR_SIGNATURE; 166 } 167 168 /* Get the signature (bitstring) */ 169 p = (unsigned char *)sig_ptr; 170 end = (unsigned char *)(p + sig_len); 171 signature.tag = *p; 172 rc = mbedtls_asn1_get_bitstring_null(&p, end, &signature.len); 173 if ((rc != 0) || ((size_t)(end - p) != signature.len)) { 174 rc = CRYPTO_ERR_SIGNATURE; 175 goto end2; 176 } 177 signature.p = p; 178 179 /* Convert this pk_alg and md_alg to PSA key type and key algorithm */ 180 construct_psa_key_alg_and_type(pk_alg, md_alg, 181 &psa_alg, &psa_key_type); 182 183 184 if ((psa_alg == PSA_ALG_NONE) || (psa_key_type == PSA_KEY_TYPE_NONE)) { 185 rc = CRYPTO_ERR_SIGNATURE; 186 goto end2; 187 } 188 189 /* filled-in key_attributes */ 190 psa_set_key_algorithm(&psa_key_attr, psa_alg); 191 psa_set_key_type(&psa_key_attr, psa_key_type); 192 psa_set_key_usage_flags(&psa_key_attr, PSA_KEY_USAGE_VERIFY_MESSAGE); 193 194 /* Get the key_id using import API */ 195 status = psa_import_key(&psa_key_attr, 196 pk_ptr, 197 (size_t)pk_len, 198 &psa_key_id); 199 200 if (status != PSA_SUCCESS) { 201 rc = CRYPTO_ERR_SIGNATURE; 202 goto end2; 203 } 204 205 /* 206 * Hash calculation and Signature verification of the given data payload 207 * is wrapped under the psa_verify_message function. 208 */ 209 status = psa_verify_message(psa_key_id, psa_alg, 210 data_ptr, data_len, 211 signature.p, signature.len); 212 213 if (status != PSA_SUCCESS) { 214 rc = CRYPTO_ERR_SIGNATURE; 215 goto end1; 216 } 217 218 /* Signature verification success */ 219 rc = CRYPTO_SUCCESS; 220 221 end1: 222 /* 223 * Destroy the key if it is created successfully 224 */ 225 psa_destroy_key(psa_key_id); 226 end2: 227 mbedtls_free(sig_opts); 228 return rc; 229 } 230 231 /* 232 * Match a hash 233 * 234 * Digest info is passed in DER format following the ASN.1 structure detailed 235 * above. 236 */ 237 static int verify_hash(void *data_ptr, unsigned int data_len, 238 void *digest_info_ptr, unsigned int digest_info_len) 239 { 240 mbedtls_asn1_buf hash_oid, params; 241 mbedtls_md_type_t md_alg; 242 unsigned char *p, *end, *hash; 243 size_t len; 244 int rc; 245 psa_status_t status; 246 psa_algorithm_t psa_md_alg; 247 248 /* 249 * Digest info should be an MBEDTLS_ASN1_SEQUENCE, but padding after 250 * it is allowed. This is necessary to support multiple hash 251 * algorithms. 252 */ 253 p = (unsigned char *)digest_info_ptr; 254 end = p + digest_info_len; 255 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_CONSTRUCTED | 256 MBEDTLS_ASN1_SEQUENCE); 257 if (rc != 0) { 258 return CRYPTO_ERR_HASH; 259 } 260 261 end = p + len; 262 263 /* Get the hash algorithm */ 264 rc = mbedtls_asn1_get_alg(&p, end, &hash_oid, ¶ms); 265 if (rc != 0) { 266 return CRYPTO_ERR_HASH; 267 } 268 269 /* Hash should be octet string type and consume all bytes */ 270 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING); 271 if ((rc != 0) || ((size_t)(end - p) != len)) { 272 return CRYPTO_ERR_HASH; 273 } 274 hash = p; 275 276 rc = mbedtls_oid_get_md_alg(&hash_oid, &md_alg); 277 if (rc != 0) { 278 return CRYPTO_ERR_HASH; 279 } 280 281 /* convert the md_alg to psa_algo */ 282 psa_md_alg = mbedtls_md_psa_alg_from_type(md_alg); 283 284 /* Length of hash must match the algorithm's size */ 285 if (len != PSA_HASH_LENGTH(psa_md_alg)) { 286 return CRYPTO_ERR_HASH; 287 } 288 289 /* 290 * Calculate Hash and compare it against the retrieved hash from 291 * the certificate (one shot API). 292 */ 293 status = psa_hash_compare(psa_md_alg, 294 data_ptr, (size_t)data_len, 295 (const uint8_t *)hash, len); 296 297 if (status != PSA_SUCCESS) { 298 return CRYPTO_ERR_HASH; 299 } 300 301 return CRYPTO_SUCCESS; 302 } 303 #endif /* 304 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY || \ 305 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 306 */ 307 308 #if CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 309 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 310 /* 311 * Map a generic crypto message digest algorithm to the corresponding macro used 312 * by Mbed TLS. 313 */ 314 static inline mbedtls_md_type_t md_type(enum crypto_md_algo algo) 315 { 316 switch (algo) { 317 case CRYPTO_MD_SHA512: 318 return MBEDTLS_MD_SHA512; 319 case CRYPTO_MD_SHA384: 320 return MBEDTLS_MD_SHA384; 321 case CRYPTO_MD_SHA256: 322 return MBEDTLS_MD_SHA256; 323 default: 324 /* Invalid hash algorithm. */ 325 return MBEDTLS_MD_NONE; 326 } 327 } 328 329 /* 330 * Calculate a hash 331 * 332 * output points to the computed hash 333 */ 334 static int calc_hash(enum crypto_md_algo md_algo, void *data_ptr, 335 unsigned int data_len, 336 unsigned char output[CRYPTO_MD_MAX_SIZE]) 337 { 338 size_t hash_length; 339 psa_status_t status; 340 psa_algorithm_t psa_md_alg; 341 342 /* convert the md_alg to psa_algo */ 343 psa_md_alg = mbedtls_md_psa_alg_from_type(md_type(md_algo)); 344 345 /* 346 * Calculate the hash of the data, it is safe to pass the 347 * 'output' hash buffer pointer considering its size is always 348 * bigger than or equal to MBEDTLS_MD_MAX_SIZE. 349 */ 350 status = psa_hash_compute(psa_md_alg, data_ptr, (size_t)data_len, 351 (uint8_t *)output, CRYPTO_MD_MAX_SIZE, 352 &hash_length); 353 if (status != PSA_SUCCESS) { 354 return CRYPTO_ERR_HASH; 355 } 356 357 return CRYPTO_SUCCESS; 358 } 359 #endif /* 360 * CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 361 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 362 */ 363 364 #if TF_MBEDTLS_USE_AES_GCM 365 /* 366 * Stack based buffer allocation for decryption operation. It could 367 * be configured to balance stack usage vs execution speed. 368 */ 369 #define DEC_OP_BUF_SIZE 128 370 371 static int aes_gcm_decrypt(void *data_ptr, size_t len, const void *key, 372 unsigned int key_len, const void *iv, 373 unsigned int iv_len, const void *tag, 374 unsigned int tag_len) 375 { 376 mbedtls_gcm_context ctx; 377 mbedtls_cipher_id_t cipher = MBEDTLS_CIPHER_ID_AES; 378 unsigned char buf[DEC_OP_BUF_SIZE]; 379 unsigned char tag_buf[CRYPTO_MAX_TAG_SIZE]; 380 unsigned char *pt = data_ptr; 381 size_t dec_len; 382 int diff, i, rc; 383 size_t output_length __unused; 384 385 mbedtls_gcm_init(&ctx); 386 387 rc = mbedtls_gcm_setkey(&ctx, cipher, key, key_len * 8); 388 if (rc != 0) { 389 rc = CRYPTO_ERR_DECRYPTION; 390 goto exit_gcm; 391 } 392 393 #if (MBEDTLS_VERSION_MAJOR < 3) 394 rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len, NULL, 0); 395 #else 396 rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len); 397 #endif 398 if (rc != 0) { 399 rc = CRYPTO_ERR_DECRYPTION; 400 goto exit_gcm; 401 } 402 403 while (len > 0) { 404 dec_len = MIN(sizeof(buf), len); 405 406 #if (MBEDTLS_VERSION_MAJOR < 3) 407 rc = mbedtls_gcm_update(&ctx, dec_len, pt, buf); 408 #else 409 rc = mbedtls_gcm_update(&ctx, pt, dec_len, buf, sizeof(buf), &output_length); 410 #endif 411 412 if (rc != 0) { 413 rc = CRYPTO_ERR_DECRYPTION; 414 goto exit_gcm; 415 } 416 417 memcpy(pt, buf, dec_len); 418 pt += dec_len; 419 len -= dec_len; 420 } 421 422 #if (MBEDTLS_VERSION_MAJOR < 3) 423 rc = mbedtls_gcm_finish(&ctx, tag_buf, sizeof(tag_buf)); 424 #else 425 rc = mbedtls_gcm_finish(&ctx, NULL, 0, &output_length, tag_buf, sizeof(tag_buf)); 426 #endif 427 428 if (rc != 0) { 429 rc = CRYPTO_ERR_DECRYPTION; 430 goto exit_gcm; 431 } 432 433 /* Check tag in "constant-time" */ 434 for (diff = 0, i = 0; i < tag_len; i++) 435 diff |= ((const unsigned char *)tag)[i] ^ tag_buf[i]; 436 437 if (diff != 0) { 438 rc = CRYPTO_ERR_DECRYPTION; 439 goto exit_gcm; 440 } 441 442 /* GCM decryption success */ 443 rc = CRYPTO_SUCCESS; 444 445 exit_gcm: 446 mbedtls_gcm_free(&ctx); 447 return rc; 448 } 449 450 /* 451 * Authenticated decryption of an image 452 */ 453 static int auth_decrypt(enum crypto_dec_algo dec_algo, void *data_ptr, 454 size_t len, const void *key, unsigned int key_len, 455 unsigned int key_flags, const void *iv, 456 unsigned int iv_len, const void *tag, 457 unsigned int tag_len) 458 { 459 int rc; 460 461 assert((key_flags & ENC_KEY_IS_IDENTIFIER) == 0); 462 463 switch (dec_algo) { 464 case CRYPTO_GCM_DECRYPT: 465 rc = aes_gcm_decrypt(data_ptr, len, key, key_len, iv, iv_len, 466 tag, tag_len); 467 if (rc != 0) 468 return rc; 469 break; 470 default: 471 return CRYPTO_ERR_DECRYPTION; 472 } 473 474 return CRYPTO_SUCCESS; 475 } 476 #endif /* TF_MBEDTLS_USE_AES_GCM */ 477 478 /* 479 * Register crypto library descriptor 480 */ 481 #if CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 482 #if TF_MBEDTLS_USE_AES_GCM 483 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash, 484 auth_decrypt, NULL); 485 #else 486 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash, 487 NULL, NULL); 488 #endif 489 #elif CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY 490 #if TF_MBEDTLS_USE_AES_GCM 491 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL, 492 auth_decrypt, NULL); 493 #else 494 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL, 495 NULL, NULL); 496 #endif 497 #elif CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY 498 REGISTER_CRYPTO_LIB(LIB_NAME, init, NULL, NULL, calc_hash, NULL, NULL); 499 #endif /* CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC */ 500