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 * Verify a signature. 110 * 111 * Parameters are passed using the DER encoding format following the ASN.1 112 * structures detailed above. 113 */ 114 static int verify_signature(void *data_ptr, unsigned int data_len, 115 void *sig_ptr, unsigned int sig_len, 116 void *sig_alg, unsigned int sig_alg_len, 117 void *pk_ptr, unsigned int pk_len) 118 { 119 mbedtls_asn1_buf sig_oid, sig_params; 120 mbedtls_asn1_buf signature; 121 mbedtls_md_type_t md_alg; 122 mbedtls_pk_type_t pk_alg; 123 mbedtls_pk_context pk = {0}; 124 int rc; 125 void *sig_opts = NULL; 126 const mbedtls_md_info_t *md_info; 127 unsigned char *p, *end; 128 unsigned char hash[MBEDTLS_MD_MAX_SIZE]; 129 130 /* Get pointers to signature OID and parameters */ 131 p = (unsigned char *)sig_alg; 132 end = (unsigned char *)(p + sig_alg_len); 133 rc = mbedtls_asn1_get_alg(&p, end, &sig_oid, &sig_params); 134 if (rc != 0) { 135 return CRYPTO_ERR_SIGNATURE; 136 } 137 138 /* Get the actual signature algorithm (MD + PK) */ 139 rc = mbedtls_x509_get_sig_alg(&sig_oid, &sig_params, &md_alg, &pk_alg, &sig_opts); 140 if (rc != 0) { 141 return CRYPTO_ERR_SIGNATURE; 142 } 143 144 /* Parse the public key */ 145 mbedtls_pk_init(&pk); 146 p = (unsigned char *)pk_ptr; 147 end = (unsigned char *)(p + pk_len); 148 rc = mbedtls_pk_parse_subpubkey(&p, end, &pk); 149 if (rc != 0) { 150 rc = CRYPTO_ERR_SIGNATURE; 151 goto end2; 152 } 153 154 /* Get the signature (bitstring) */ 155 p = (unsigned char *)sig_ptr; 156 end = (unsigned char *)(p + sig_len); 157 signature.tag = *p; 158 rc = mbedtls_asn1_get_bitstring_null(&p, end, &signature.len); 159 if ((rc != 0) || ((size_t)(end - p) != signature.len)) { 160 rc = CRYPTO_ERR_SIGNATURE; 161 goto end1; 162 } 163 signature.p = p; 164 165 /* Calculate the hash of the data */ 166 md_info = mbedtls_md_info_from_type(md_alg); 167 if (md_info == NULL) { 168 rc = CRYPTO_ERR_SIGNATURE; 169 goto end1; 170 } 171 p = (unsigned char *)data_ptr; 172 rc = mbedtls_md(md_info, p, data_len, hash); 173 if (rc != 0) { 174 rc = CRYPTO_ERR_SIGNATURE; 175 goto end1; 176 } 177 178 /* Verify the signature */ 179 rc = mbedtls_pk_verify_ext(pk_alg, sig_opts, &pk, md_alg, hash, 180 mbedtls_md_get_size(md_info), 181 signature.p, signature.len); 182 if (rc != 0) { 183 rc = CRYPTO_ERR_SIGNATURE; 184 goto end1; 185 } 186 187 /* Signature verification success */ 188 rc = CRYPTO_SUCCESS; 189 190 end1: 191 mbedtls_pk_free(&pk); 192 end2: 193 mbedtls_free(sig_opts); 194 return rc; 195 } 196 197 /* 198 * Match a hash 199 * 200 * Digest info is passed in DER format following the ASN.1 structure detailed 201 * above. 202 */ 203 static int verify_hash(void *data_ptr, unsigned int data_len, 204 void *digest_info_ptr, unsigned int digest_info_len) 205 { 206 mbedtls_asn1_buf hash_oid, params; 207 mbedtls_md_type_t md_alg; 208 unsigned char *p, *end, *hash; 209 size_t len; 210 int rc; 211 psa_status_t status; 212 psa_algorithm_t psa_md_alg; 213 214 /* 215 * Digest info should be an MBEDTLS_ASN1_SEQUENCE, but padding after 216 * it is allowed. This is necessary to support multiple hash 217 * algorithms. 218 */ 219 p = (unsigned char *)digest_info_ptr; 220 end = p + digest_info_len; 221 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_CONSTRUCTED | 222 MBEDTLS_ASN1_SEQUENCE); 223 if (rc != 0) { 224 return CRYPTO_ERR_HASH; 225 } 226 227 end = p + len; 228 229 /* Get the hash algorithm */ 230 rc = mbedtls_asn1_get_alg(&p, end, &hash_oid, ¶ms); 231 if (rc != 0) { 232 return CRYPTO_ERR_HASH; 233 } 234 235 /* Hash should be octet string type and consume all bytes */ 236 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING); 237 if ((rc != 0) || ((size_t)(end - p) != len)) { 238 return CRYPTO_ERR_HASH; 239 } 240 hash = p; 241 242 rc = mbedtls_oid_get_md_alg(&hash_oid, &md_alg); 243 if (rc != 0) { 244 return CRYPTO_ERR_HASH; 245 } 246 247 /* convert the md_alg to psa_algo */ 248 psa_md_alg = mbedtls_md_psa_alg_from_type(md_alg); 249 250 /* Length of hash must match the algorithm's size */ 251 if (len != PSA_HASH_LENGTH(psa_md_alg)) { 252 return CRYPTO_ERR_HASH; 253 } 254 255 /* 256 * Calculate Hash and compare it against the retrieved hash from 257 * the certificate (one shot API). 258 */ 259 status = psa_hash_compare(psa_md_alg, 260 data_ptr, (size_t)data_len, 261 (const uint8_t *)hash, len); 262 263 if (status != PSA_SUCCESS) { 264 return CRYPTO_ERR_HASH; 265 } 266 267 return CRYPTO_SUCCESS; 268 } 269 #endif /* 270 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY || \ 271 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 272 */ 273 274 #if CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 275 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 276 /* 277 * Map a generic crypto message digest algorithm to the corresponding macro used 278 * by Mbed TLS. 279 */ 280 static inline mbedtls_md_type_t md_type(enum crypto_md_algo algo) 281 { 282 switch (algo) { 283 case CRYPTO_MD_SHA512: 284 return MBEDTLS_MD_SHA512; 285 case CRYPTO_MD_SHA384: 286 return MBEDTLS_MD_SHA384; 287 case CRYPTO_MD_SHA256: 288 return MBEDTLS_MD_SHA256; 289 default: 290 /* Invalid hash algorithm. */ 291 return MBEDTLS_MD_NONE; 292 } 293 } 294 295 /* 296 * Calculate a hash 297 * 298 * output points to the computed hash 299 */ 300 static int calc_hash(enum crypto_md_algo md_algo, void *data_ptr, 301 unsigned int data_len, 302 unsigned char output[CRYPTO_MD_MAX_SIZE]) 303 { 304 const mbedtls_md_info_t *md_info; 305 306 md_info = mbedtls_md_info_from_type(md_type(md_algo)); 307 if (md_info == NULL) { 308 return CRYPTO_ERR_HASH; 309 } 310 311 /* 312 * Calculate the hash of the data, it is safe to pass the 313 * 'output' hash buffer pointer considering its size is always 314 * bigger than or equal to MBEDTLS_MD_MAX_SIZE. 315 */ 316 return mbedtls_md(md_info, data_ptr, data_len, output); 317 } 318 #endif /* 319 * CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 320 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 321 */ 322 323 #if TF_MBEDTLS_USE_AES_GCM 324 /* 325 * Stack based buffer allocation for decryption operation. It could 326 * be configured to balance stack usage vs execution speed. 327 */ 328 #define DEC_OP_BUF_SIZE 128 329 330 static int aes_gcm_decrypt(void *data_ptr, size_t len, const void *key, 331 unsigned int key_len, const void *iv, 332 unsigned int iv_len, const void *tag, 333 unsigned int tag_len) 334 { 335 mbedtls_gcm_context ctx; 336 mbedtls_cipher_id_t cipher = MBEDTLS_CIPHER_ID_AES; 337 unsigned char buf[DEC_OP_BUF_SIZE]; 338 unsigned char tag_buf[CRYPTO_MAX_TAG_SIZE]; 339 unsigned char *pt = data_ptr; 340 size_t dec_len; 341 int diff, i, rc; 342 size_t output_length __unused; 343 344 mbedtls_gcm_init(&ctx); 345 346 rc = mbedtls_gcm_setkey(&ctx, cipher, key, key_len * 8); 347 if (rc != 0) { 348 rc = CRYPTO_ERR_DECRYPTION; 349 goto exit_gcm; 350 } 351 352 #if (MBEDTLS_VERSION_MAJOR < 3) 353 rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len, NULL, 0); 354 #else 355 rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len); 356 #endif 357 if (rc != 0) { 358 rc = CRYPTO_ERR_DECRYPTION; 359 goto exit_gcm; 360 } 361 362 while (len > 0) { 363 dec_len = MIN(sizeof(buf), len); 364 365 #if (MBEDTLS_VERSION_MAJOR < 3) 366 rc = mbedtls_gcm_update(&ctx, dec_len, pt, buf); 367 #else 368 rc = mbedtls_gcm_update(&ctx, pt, dec_len, buf, sizeof(buf), &output_length); 369 #endif 370 371 if (rc != 0) { 372 rc = CRYPTO_ERR_DECRYPTION; 373 goto exit_gcm; 374 } 375 376 memcpy(pt, buf, dec_len); 377 pt += dec_len; 378 len -= dec_len; 379 } 380 381 #if (MBEDTLS_VERSION_MAJOR < 3) 382 rc = mbedtls_gcm_finish(&ctx, tag_buf, sizeof(tag_buf)); 383 #else 384 rc = mbedtls_gcm_finish(&ctx, NULL, 0, &output_length, tag_buf, sizeof(tag_buf)); 385 #endif 386 387 if (rc != 0) { 388 rc = CRYPTO_ERR_DECRYPTION; 389 goto exit_gcm; 390 } 391 392 /* Check tag in "constant-time" */ 393 for (diff = 0, i = 0; i < tag_len; i++) 394 diff |= ((const unsigned char *)tag)[i] ^ tag_buf[i]; 395 396 if (diff != 0) { 397 rc = CRYPTO_ERR_DECRYPTION; 398 goto exit_gcm; 399 } 400 401 /* GCM decryption success */ 402 rc = CRYPTO_SUCCESS; 403 404 exit_gcm: 405 mbedtls_gcm_free(&ctx); 406 return rc; 407 } 408 409 /* 410 * Authenticated decryption of an image 411 */ 412 static int auth_decrypt(enum crypto_dec_algo dec_algo, void *data_ptr, 413 size_t len, const void *key, unsigned int key_len, 414 unsigned int key_flags, const void *iv, 415 unsigned int iv_len, const void *tag, 416 unsigned int tag_len) 417 { 418 int rc; 419 420 assert((key_flags & ENC_KEY_IS_IDENTIFIER) == 0); 421 422 switch (dec_algo) { 423 case CRYPTO_GCM_DECRYPT: 424 rc = aes_gcm_decrypt(data_ptr, len, key, key_len, iv, iv_len, 425 tag, tag_len); 426 if (rc != 0) 427 return rc; 428 break; 429 default: 430 return CRYPTO_ERR_DECRYPTION; 431 } 432 433 return CRYPTO_SUCCESS; 434 } 435 #endif /* TF_MBEDTLS_USE_AES_GCM */ 436 437 /* 438 * Register crypto library descriptor 439 */ 440 #if CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 441 #if TF_MBEDTLS_USE_AES_GCM 442 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash, 443 auth_decrypt, NULL); 444 #else 445 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash, 446 NULL, NULL); 447 #endif 448 #elif CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY 449 #if TF_MBEDTLS_USE_AES_GCM 450 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL, 451 auth_decrypt, NULL); 452 #else 453 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL, 454 NULL, NULL); 455 #endif 456 #elif CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY 457 REGISTER_CRYPTO_LIB(LIB_NAME, init, NULL, NULL, calc_hash, NULL, NULL); 458 #endif /* CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC */ 459