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 20 #include <common/debug.h> 21 #include <drivers/auth/crypto_mod.h> 22 #include <drivers/auth/mbedtls/mbedtls_common.h> 23 24 #include <plat/common/platform.h> 25 26 #define LIB_NAME "mbed TLS PSA" 27 28 #if CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 29 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 30 /* 31 * CRYPTO_MD_MAX_SIZE value is as per current stronger algorithm available 32 * so make sure that mbed TLS MD maximum size must be lesser than this. 33 */ 34 CASSERT(CRYPTO_MD_MAX_SIZE >= MBEDTLS_MD_MAX_SIZE, 35 assert_mbedtls_md_size_overflow); 36 37 #endif /* 38 * CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 39 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 40 */ 41 42 /* 43 * AlgorithmIdentifier ::= SEQUENCE { 44 * algorithm OBJECT IDENTIFIER, 45 * parameters ANY DEFINED BY algorithm OPTIONAL 46 * } 47 * 48 * SubjectPublicKeyInfo ::= SEQUENCE { 49 * algorithm AlgorithmIdentifier, 50 * subjectPublicKey BIT STRING 51 * } 52 * 53 * DigestInfo ::= SEQUENCE { 54 * digestAlgorithm AlgorithmIdentifier, 55 * digest OCTET STRING 56 * } 57 */ 58 59 /* 60 * Initialize the library and export the descriptor 61 */ 62 static void init(void) 63 { 64 /* Initialize mbed TLS */ 65 mbedtls_init(); 66 } 67 68 #if CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY || \ 69 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 70 /* 71 * Verify a signature. 72 * 73 * Parameters are passed using the DER encoding format following the ASN.1 74 * structures detailed above. 75 */ 76 static int verify_signature(void *data_ptr, unsigned int data_len, 77 void *sig_ptr, unsigned int sig_len, 78 void *sig_alg, unsigned int sig_alg_len, 79 void *pk_ptr, unsigned int pk_len) 80 { 81 mbedtls_asn1_buf sig_oid, sig_params; 82 mbedtls_asn1_buf signature; 83 mbedtls_md_type_t md_alg; 84 mbedtls_pk_type_t pk_alg; 85 mbedtls_pk_context pk = {0}; 86 int rc; 87 void *sig_opts = NULL; 88 const mbedtls_md_info_t *md_info; 89 unsigned char *p, *end; 90 unsigned char hash[MBEDTLS_MD_MAX_SIZE]; 91 92 /* Get pointers to signature OID and parameters */ 93 p = (unsigned char *)sig_alg; 94 end = (unsigned char *)(p + sig_alg_len); 95 rc = mbedtls_asn1_get_alg(&p, end, &sig_oid, &sig_params); 96 if (rc != 0) { 97 return CRYPTO_ERR_SIGNATURE; 98 } 99 100 /* Get the actual signature algorithm (MD + PK) */ 101 rc = mbedtls_x509_get_sig_alg(&sig_oid, &sig_params, &md_alg, &pk_alg, &sig_opts); 102 if (rc != 0) { 103 return CRYPTO_ERR_SIGNATURE; 104 } 105 106 /* Parse the public key */ 107 mbedtls_pk_init(&pk); 108 p = (unsigned char *)pk_ptr; 109 end = (unsigned char *)(p + pk_len); 110 rc = mbedtls_pk_parse_subpubkey(&p, end, &pk); 111 if (rc != 0) { 112 rc = CRYPTO_ERR_SIGNATURE; 113 goto end2; 114 } 115 116 /* Get the signature (bitstring) */ 117 p = (unsigned char *)sig_ptr; 118 end = (unsigned char *)(p + sig_len); 119 signature.tag = *p; 120 rc = mbedtls_asn1_get_bitstring_null(&p, end, &signature.len); 121 if ((rc != 0) || ((size_t)(end - p) != signature.len)) { 122 rc = CRYPTO_ERR_SIGNATURE; 123 goto end1; 124 } 125 signature.p = p; 126 127 /* Calculate the hash of the data */ 128 md_info = mbedtls_md_info_from_type(md_alg); 129 if (md_info == NULL) { 130 rc = CRYPTO_ERR_SIGNATURE; 131 goto end1; 132 } 133 p = (unsigned char *)data_ptr; 134 rc = mbedtls_md(md_info, p, data_len, hash); 135 if (rc != 0) { 136 rc = CRYPTO_ERR_SIGNATURE; 137 goto end1; 138 } 139 140 /* Verify the signature */ 141 rc = mbedtls_pk_verify_ext(pk_alg, sig_opts, &pk, md_alg, hash, 142 mbedtls_md_get_size(md_info), 143 signature.p, signature.len); 144 if (rc != 0) { 145 rc = CRYPTO_ERR_SIGNATURE; 146 goto end1; 147 } 148 149 /* Signature verification success */ 150 rc = CRYPTO_SUCCESS; 151 152 end1: 153 mbedtls_pk_free(&pk); 154 end2: 155 mbedtls_free(sig_opts); 156 return rc; 157 } 158 159 /* 160 * Match a hash 161 * 162 * Digest info is passed in DER format following the ASN.1 structure detailed 163 * above. 164 */ 165 static int verify_hash(void *data_ptr, unsigned int data_len, 166 void *digest_info_ptr, unsigned int digest_info_len) 167 { 168 mbedtls_asn1_buf hash_oid, params; 169 mbedtls_md_type_t md_alg; 170 const mbedtls_md_info_t *md_info; 171 unsigned char *p, *end, *hash; 172 unsigned char data_hash[MBEDTLS_MD_MAX_SIZE]; 173 size_t len; 174 int rc; 175 176 /* 177 * Digest info should be an MBEDTLS_ASN1_SEQUENCE, but padding after 178 * it is allowed. This is necessary to support multiple hash 179 * algorithms. 180 */ 181 p = (unsigned char *)digest_info_ptr; 182 end = p + digest_info_len; 183 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_CONSTRUCTED | 184 MBEDTLS_ASN1_SEQUENCE); 185 if (rc != 0) { 186 return CRYPTO_ERR_HASH; 187 } 188 189 end = p + len; 190 191 /* Get the hash algorithm */ 192 rc = mbedtls_asn1_get_alg(&p, end, &hash_oid, ¶ms); 193 if (rc != 0) { 194 return CRYPTO_ERR_HASH; 195 } 196 197 rc = mbedtls_oid_get_md_alg(&hash_oid, &md_alg); 198 if (rc != 0) { 199 return CRYPTO_ERR_HASH; 200 } 201 202 md_info = mbedtls_md_info_from_type(md_alg); 203 if (md_info == NULL) { 204 return CRYPTO_ERR_HASH; 205 } 206 207 /* Hash should be octet string type and consume all bytes */ 208 rc = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING); 209 if ((rc != 0) || ((size_t)(end - p) != len)) { 210 return CRYPTO_ERR_HASH; 211 } 212 213 /* Length of hash must match the algorithm's size */ 214 if (len != mbedtls_md_get_size(md_info)) { 215 return CRYPTO_ERR_HASH; 216 } 217 hash = p; 218 219 /* Calculate the hash of the data */ 220 p = (unsigned char *)data_ptr; 221 rc = mbedtls_md(md_info, p, data_len, data_hash); 222 if (rc != 0) { 223 return CRYPTO_ERR_HASH; 224 } 225 226 /* Compare values */ 227 rc = memcmp(data_hash, hash, mbedtls_md_get_size(md_info)); 228 if (rc != 0) { 229 return CRYPTO_ERR_HASH; 230 } 231 232 return CRYPTO_SUCCESS; 233 } 234 #endif /* 235 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY || \ 236 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 237 */ 238 239 #if CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 240 CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 241 /* 242 * Map a generic crypto message digest algorithm to the corresponding macro used 243 * by Mbed TLS. 244 */ 245 static inline mbedtls_md_type_t md_type(enum crypto_md_algo algo) 246 { 247 switch (algo) { 248 case CRYPTO_MD_SHA512: 249 return MBEDTLS_MD_SHA512; 250 case CRYPTO_MD_SHA384: 251 return MBEDTLS_MD_SHA384; 252 case CRYPTO_MD_SHA256: 253 return MBEDTLS_MD_SHA256; 254 default: 255 /* Invalid hash algorithm. */ 256 return MBEDTLS_MD_NONE; 257 } 258 } 259 260 /* 261 * Calculate a hash 262 * 263 * output points to the computed hash 264 */ 265 static int calc_hash(enum crypto_md_algo md_algo, void *data_ptr, 266 unsigned int data_len, 267 unsigned char output[CRYPTO_MD_MAX_SIZE]) 268 { 269 const mbedtls_md_info_t *md_info; 270 271 md_info = mbedtls_md_info_from_type(md_type(md_algo)); 272 if (md_info == NULL) { 273 return CRYPTO_ERR_HASH; 274 } 275 276 /* 277 * Calculate the hash of the data, it is safe to pass the 278 * 'output' hash buffer pointer considering its size is always 279 * bigger than or equal to MBEDTLS_MD_MAX_SIZE. 280 */ 281 return mbedtls_md(md_info, data_ptr, data_len, output); 282 } 283 #endif /* 284 * CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY || \ 285 * CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 286 */ 287 288 #if TF_MBEDTLS_USE_AES_GCM 289 /* 290 * Stack based buffer allocation for decryption operation. It could 291 * be configured to balance stack usage vs execution speed. 292 */ 293 #define DEC_OP_BUF_SIZE 128 294 295 static int aes_gcm_decrypt(void *data_ptr, size_t len, const void *key, 296 unsigned int key_len, const void *iv, 297 unsigned int iv_len, const void *tag, 298 unsigned int tag_len) 299 { 300 mbedtls_gcm_context ctx; 301 mbedtls_cipher_id_t cipher = MBEDTLS_CIPHER_ID_AES; 302 unsigned char buf[DEC_OP_BUF_SIZE]; 303 unsigned char tag_buf[CRYPTO_MAX_TAG_SIZE]; 304 unsigned char *pt = data_ptr; 305 size_t dec_len; 306 int diff, i, rc; 307 size_t output_length __unused; 308 309 mbedtls_gcm_init(&ctx); 310 311 rc = mbedtls_gcm_setkey(&ctx, cipher, key, key_len * 8); 312 if (rc != 0) { 313 rc = CRYPTO_ERR_DECRYPTION; 314 goto exit_gcm; 315 } 316 317 #if (MBEDTLS_VERSION_MAJOR < 3) 318 rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len, NULL, 0); 319 #else 320 rc = mbedtls_gcm_starts(&ctx, MBEDTLS_GCM_DECRYPT, iv, iv_len); 321 #endif 322 if (rc != 0) { 323 rc = CRYPTO_ERR_DECRYPTION; 324 goto exit_gcm; 325 } 326 327 while (len > 0) { 328 dec_len = MIN(sizeof(buf), len); 329 330 #if (MBEDTLS_VERSION_MAJOR < 3) 331 rc = mbedtls_gcm_update(&ctx, dec_len, pt, buf); 332 #else 333 rc = mbedtls_gcm_update(&ctx, pt, dec_len, buf, sizeof(buf), &output_length); 334 #endif 335 336 if (rc != 0) { 337 rc = CRYPTO_ERR_DECRYPTION; 338 goto exit_gcm; 339 } 340 341 memcpy(pt, buf, dec_len); 342 pt += dec_len; 343 len -= dec_len; 344 } 345 346 #if (MBEDTLS_VERSION_MAJOR < 3) 347 rc = mbedtls_gcm_finish(&ctx, tag_buf, sizeof(tag_buf)); 348 #else 349 rc = mbedtls_gcm_finish(&ctx, NULL, 0, &output_length, tag_buf, sizeof(tag_buf)); 350 #endif 351 352 if (rc != 0) { 353 rc = CRYPTO_ERR_DECRYPTION; 354 goto exit_gcm; 355 } 356 357 /* Check tag in "constant-time" */ 358 for (diff = 0, i = 0; i < tag_len; i++) 359 diff |= ((const unsigned char *)tag)[i] ^ tag_buf[i]; 360 361 if (diff != 0) { 362 rc = CRYPTO_ERR_DECRYPTION; 363 goto exit_gcm; 364 } 365 366 /* GCM decryption success */ 367 rc = CRYPTO_SUCCESS; 368 369 exit_gcm: 370 mbedtls_gcm_free(&ctx); 371 return rc; 372 } 373 374 /* 375 * Authenticated decryption of an image 376 */ 377 static int auth_decrypt(enum crypto_dec_algo dec_algo, void *data_ptr, 378 size_t len, const void *key, unsigned int key_len, 379 unsigned int key_flags, const void *iv, 380 unsigned int iv_len, const void *tag, 381 unsigned int tag_len) 382 { 383 int rc; 384 385 assert((key_flags & ENC_KEY_IS_IDENTIFIER) == 0); 386 387 switch (dec_algo) { 388 case CRYPTO_GCM_DECRYPT: 389 rc = aes_gcm_decrypt(data_ptr, len, key, key_len, iv, iv_len, 390 tag, tag_len); 391 if (rc != 0) 392 return rc; 393 break; 394 default: 395 return CRYPTO_ERR_DECRYPTION; 396 } 397 398 return CRYPTO_SUCCESS; 399 } 400 #endif /* TF_MBEDTLS_USE_AES_GCM */ 401 402 /* 403 * Register crypto library descriptor 404 */ 405 #if CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC 406 #if TF_MBEDTLS_USE_AES_GCM 407 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash, 408 auth_decrypt, NULL); 409 #else 410 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, calc_hash, 411 NULL, NULL); 412 #endif 413 #elif CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_ONLY 414 #if TF_MBEDTLS_USE_AES_GCM 415 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL, 416 auth_decrypt, NULL); 417 #else 418 REGISTER_CRYPTO_LIB(LIB_NAME, init, verify_signature, verify_hash, NULL, 419 NULL, NULL); 420 #endif 421 #elif CRYPTO_SUPPORT == CRYPTO_HASH_CALC_ONLY 422 REGISTER_CRYPTO_LIB(LIB_NAME, init, NULL, NULL, calc_hash, NULL, NULL); 423 #endif /* CRYPTO_SUPPORT == CRYPTO_AUTH_VERIFY_AND_HASH_CALC */ 424