1 /* 2 * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved. 3 * 4 * SPDX-License-Identifier: BSD-3-Clause 5 */ 6 7 #include <assert.h> 8 #include <stdint.h> 9 #include <string.h> 10 11 #include <platform_def.h> 12 13 #include <common/debug.h> 14 #include <common/tbbr/cot_def.h> 15 #include <drivers/auth/auth_common.h> 16 #include <drivers/auth/auth_mod.h> 17 #include <drivers/auth/crypto_mod.h> 18 #include <drivers/auth/img_parser_mod.h> 19 #include <plat/common/platform.h> 20 21 /* ASN.1 tags */ 22 #define ASN1_INTEGER 0x02 23 24 #define return_if_error(rc) \ 25 do { \ 26 if (rc != 0) { \ 27 return rc; \ 28 } \ 29 } while (0) 30 31 #pragma weak plat_set_nv_ctr2 32 33 static int cmp_auth_param_type_desc(const auth_param_type_desc_t *a, 34 const auth_param_type_desc_t *b) 35 { 36 if ((a->type == b->type) && (a->cookie == b->cookie)) { 37 return 0; 38 } 39 return 1; 40 } 41 42 /* 43 * This function obtains the requested authentication parameter data from the 44 * information extracted from the parent image after its authentication. 45 */ 46 static int auth_get_param(const auth_param_type_desc_t *param_type_desc, 47 const auth_img_desc_t *img_desc, 48 void **param, unsigned int *len) 49 { 50 int i; 51 52 for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) { 53 if (0 == cmp_auth_param_type_desc(param_type_desc, 54 img_desc->authenticated_data[i].type_desc)) { 55 *param = img_desc->authenticated_data[i].data.ptr; 56 *len = img_desc->authenticated_data[i].data.len; 57 return 0; 58 } 59 } 60 61 return 1; 62 } 63 64 /* 65 * Authenticate an image by matching the data hash 66 * 67 * This function implements 'AUTH_METHOD_HASH'. To authenticate an image using 68 * this method, the image must contain: 69 * 70 * - The data to calculate the hash from 71 * 72 * The parent image must contain: 73 * 74 * - The hash to be matched with (including hash algorithm) 75 * 76 * For a successful authentication, both hashes must match. The function calls 77 * the crypto-module to check this matching. 78 * 79 * Parameters: 80 * param: parameters to perform the hash authentication 81 * img_desc: pointer to image descriptor so we can know the image type 82 * and parent image 83 * img: pointer to image in memory 84 * img_len: length of image (in bytes) 85 * 86 * Return: 87 * 0 = success, Otherwise = error 88 */ 89 static int auth_hash(const auth_method_param_hash_t *param, 90 const auth_img_desc_t *img_desc, 91 void *img, unsigned int img_len) 92 { 93 void *data_ptr, *hash_der_ptr; 94 unsigned int data_len, hash_der_len; 95 int rc = 0; 96 97 /* Get the hash from the parent image. This hash will be DER encoded 98 * and contain the hash algorithm */ 99 rc = auth_get_param(param->hash, img_desc->parent, 100 &hash_der_ptr, &hash_der_len); 101 return_if_error(rc); 102 103 /* Get the data to be hashed from the current image */ 104 rc = img_parser_get_auth_param(img_desc->img_type, param->data, 105 img, img_len, &data_ptr, &data_len); 106 return_if_error(rc); 107 108 /* Ask the crypto module to verify this hash */ 109 rc = crypto_mod_verify_hash(data_ptr, data_len, 110 hash_der_ptr, hash_der_len); 111 112 return rc; 113 } 114 115 /* 116 * Authenticate by digital signature 117 * 118 * This function implements 'AUTH_METHOD_SIG'. To authenticate an image using 119 * this method, the image must contain: 120 * 121 * - Data to be signed 122 * - Signature 123 * - Signature algorithm 124 * 125 * We rely on the image parser module to extract this data from the image. 126 * The parent image must contain: 127 * 128 * - Public key (or a hash of it) 129 * 130 * If the parent image contains only a hash of the key, we will try to obtain 131 * the public key from the image itself (i.e. self-signed certificates). In that 132 * case, the signature verification is considered just an integrity check and 133 * the authentication is established by calculating the hash of the key and 134 * comparing it with the hash obtained from the parent. 135 * 136 * If the image has no parent (NULL), it means it has to be authenticated using 137 * the ROTPK stored in the platform. Again, this ROTPK could be the key itself 138 * or a hash of it. 139 * 140 * Return: 0 = success, Otherwise = error 141 */ 142 static int auth_signature(const auth_method_param_sig_t *param, 143 const auth_img_desc_t *img_desc, 144 void *img, unsigned int img_len) 145 { 146 void *data_ptr, *pk_ptr, *pk_hash_ptr, *sig_ptr, *sig_alg_ptr; 147 unsigned int data_len, pk_len, pk_hash_len, sig_len, sig_alg_len; 148 unsigned int flags = 0; 149 int rc = 0; 150 151 /* Get the data to be signed from current image */ 152 rc = img_parser_get_auth_param(img_desc->img_type, param->data, 153 img, img_len, &data_ptr, &data_len); 154 return_if_error(rc); 155 156 /* Get the signature from current image */ 157 rc = img_parser_get_auth_param(img_desc->img_type, param->sig, 158 img, img_len, &sig_ptr, &sig_len); 159 return_if_error(rc); 160 161 /* Get the signature algorithm from current image */ 162 rc = img_parser_get_auth_param(img_desc->img_type, param->alg, 163 img, img_len, &sig_alg_ptr, &sig_alg_len); 164 return_if_error(rc); 165 166 /* Get the public key from the parent. If there is no parent (NULL), 167 * the certificate has been signed with the ROTPK, so we have to get 168 * the PK from the platform */ 169 if (img_desc->parent) { 170 rc = auth_get_param(param->pk, img_desc->parent, 171 &pk_ptr, &pk_len); 172 } else { 173 rc = plat_get_rotpk_info(param->pk->cookie, &pk_ptr, &pk_len, 174 &flags); 175 } 176 return_if_error(rc); 177 178 if (flags & (ROTPK_IS_HASH | ROTPK_NOT_DEPLOYED)) { 179 /* If the PK is a hash of the key or if the ROTPK is not 180 deployed on the platform, retrieve the key from the image */ 181 pk_hash_ptr = pk_ptr; 182 pk_hash_len = pk_len; 183 rc = img_parser_get_auth_param(img_desc->img_type, 184 param->pk, img, img_len, 185 &pk_ptr, &pk_len); 186 return_if_error(rc); 187 188 /* Ask the crypto module to verify the signature */ 189 rc = crypto_mod_verify_signature(data_ptr, data_len, 190 sig_ptr, sig_len, 191 sig_alg_ptr, sig_alg_len, 192 pk_ptr, pk_len); 193 return_if_error(rc); 194 195 if (flags & ROTPK_NOT_DEPLOYED) { 196 NOTICE("ROTPK is not deployed on platform. " 197 "Skipping ROTPK verification.\n"); 198 } else { 199 /* Ask the crypto-module to verify the key hash */ 200 rc = crypto_mod_verify_hash(pk_ptr, pk_len, 201 pk_hash_ptr, pk_hash_len); 202 } 203 } else { 204 /* Ask the crypto module to verify the signature */ 205 rc = crypto_mod_verify_signature(data_ptr, data_len, 206 sig_ptr, sig_len, 207 sig_alg_ptr, sig_alg_len, 208 pk_ptr, pk_len); 209 } 210 211 return rc; 212 } 213 214 /* 215 * Authenticate by Non-Volatile counter 216 * 217 * To protect the system against rollback, the platform includes a non-volatile 218 * counter whose value can only be increased. All certificates include a counter 219 * value that should not be lower than the value stored in the platform. If the 220 * value is larger, the counter in the platform must be updated to the new 221 * value. 222 * 223 * Return: 0 = success, Otherwise = error 224 */ 225 static int auth_nvctr(const auth_method_param_nv_ctr_t *param, 226 const auth_img_desc_t *img_desc, 227 void *img, unsigned int img_len) 228 { 229 char *p; 230 void *data_ptr = NULL; 231 unsigned int data_len, len, i; 232 unsigned int cert_nv_ctr, plat_nv_ctr; 233 int rc = 0; 234 235 /* Get the counter value from current image. The AM expects the IPM 236 * to return the counter value as a DER encoded integer */ 237 rc = img_parser_get_auth_param(img_desc->img_type, param->cert_nv_ctr, 238 img, img_len, &data_ptr, &data_len); 239 return_if_error(rc); 240 241 /* Parse the DER encoded integer */ 242 assert(data_ptr); 243 p = (char *)data_ptr; 244 if (*p != ASN1_INTEGER) { 245 /* Invalid ASN.1 integer */ 246 return 1; 247 } 248 p++; 249 250 /* NV-counters are unsigned integers up to 32-bit */ 251 len = (unsigned int)(*p & 0x7f); 252 if ((*p & 0x80) || (len > 4)) { 253 return 1; 254 } 255 p++; 256 257 /* Check the number is not negative */ 258 if (*p & 0x80) { 259 return 1; 260 } 261 262 /* Convert to unsigned int. This code is for a little-endian CPU */ 263 cert_nv_ctr = 0; 264 for (i = 0; i < len; i++) { 265 cert_nv_ctr = (cert_nv_ctr << 8) | *p++; 266 } 267 268 /* Get the counter from the platform */ 269 rc = plat_get_nv_ctr(param->plat_nv_ctr->cookie, &plat_nv_ctr); 270 return_if_error(rc); 271 272 if (cert_nv_ctr < plat_nv_ctr) { 273 /* Invalid NV-counter */ 274 return 1; 275 } else if (cert_nv_ctr > plat_nv_ctr) { 276 rc = plat_set_nv_ctr2(param->plat_nv_ctr->cookie, 277 img_desc, cert_nv_ctr); 278 return_if_error(rc); 279 } 280 281 return 0; 282 } 283 284 int plat_set_nv_ctr2(void *cookie, const auth_img_desc_t *img_desc __unused, 285 unsigned int nv_ctr) 286 { 287 return plat_set_nv_ctr(cookie, nv_ctr); 288 } 289 290 /* 291 * Return the parent id in the output parameter '*parent_id' 292 * 293 * Return value: 294 * 0 = Image has parent, 1 = Image has no parent or parent is authenticated 295 */ 296 int auth_mod_get_parent_id(unsigned int img_id, unsigned int *parent_id) 297 { 298 const auth_img_desc_t *img_desc = NULL; 299 300 assert(parent_id != NULL); 301 302 /* Get the image descriptor */ 303 img_desc = &cot_desc_ptr[img_id]; 304 305 /* Check if the image has no parent (ROT) */ 306 if (img_desc->parent == NULL) { 307 *parent_id = 0; 308 return 1; 309 } 310 311 /* Check if the parent has already been authenticated */ 312 if (auth_img_flags[img_desc->parent->img_id] & IMG_FLAG_AUTHENTICATED) { 313 *parent_id = 0; 314 return 1; 315 } 316 317 *parent_id = img_desc->parent->img_id; 318 return 0; 319 } 320 321 /* 322 * Initialize the different modules in the authentication framework 323 */ 324 void auth_mod_init(void) 325 { 326 /* Check we have a valid CoT registered */ 327 assert(cot_desc_ptr != NULL); 328 329 /* Crypto module */ 330 crypto_mod_init(); 331 332 /* Image parser module */ 333 img_parser_init(); 334 } 335 336 /* 337 * Authenticate a certificate/image 338 * 339 * Return: 0 = success, Otherwise = error 340 */ 341 int auth_mod_verify_img(unsigned int img_id, 342 void *img_ptr, 343 unsigned int img_len) 344 { 345 const auth_img_desc_t *img_desc = NULL; 346 const auth_method_desc_t *auth_method = NULL; 347 void *param_ptr; 348 unsigned int param_len; 349 int rc, i; 350 351 /* Get the image descriptor from the chain of trust */ 352 img_desc = &cot_desc_ptr[img_id]; 353 354 /* Ask the parser to check the image integrity */ 355 rc = img_parser_check_integrity(img_desc->img_type, img_ptr, img_len); 356 return_if_error(rc); 357 358 /* Authenticate the image using the methods indicated in the image 359 * descriptor. */ 360 for (i = 0 ; i < AUTH_METHOD_NUM ; i++) { 361 auth_method = &img_desc->img_auth_methods[i]; 362 switch (auth_method->type) { 363 case AUTH_METHOD_NONE: 364 rc = 0; 365 break; 366 case AUTH_METHOD_HASH: 367 rc = auth_hash(&auth_method->param.hash, 368 img_desc, img_ptr, img_len); 369 break; 370 case AUTH_METHOD_SIG: 371 rc = auth_signature(&auth_method->param.sig, 372 img_desc, img_ptr, img_len); 373 break; 374 case AUTH_METHOD_NV_CTR: 375 rc = auth_nvctr(&auth_method->param.nv_ctr, 376 img_desc, img_ptr, img_len); 377 break; 378 default: 379 /* Unknown authentication method */ 380 rc = 1; 381 break; 382 } 383 return_if_error(rc); 384 } 385 386 /* Extract the parameters indicated in the image descriptor to 387 * authenticate the children images. */ 388 for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) { 389 if (img_desc->authenticated_data[i].type_desc == NULL) { 390 continue; 391 } 392 393 /* Get the parameter from the image parser module */ 394 rc = img_parser_get_auth_param(img_desc->img_type, 395 img_desc->authenticated_data[i].type_desc, 396 img_ptr, img_len, ¶m_ptr, ¶m_len); 397 return_if_error(rc); 398 399 /* Check parameter size */ 400 if (param_len > img_desc->authenticated_data[i].data.len) { 401 return 1; 402 } 403 404 /* Copy the parameter for later use */ 405 memcpy((void *)img_desc->authenticated_data[i].data.ptr, 406 (void *)param_ptr, param_len); 407 } 408 409 /* Mark image as authenticated */ 410 auth_img_flags[img_desc->img_id] |= IMG_FLAG_AUTHENTICATED; 411 412 return 0; 413 } 414