1 /* 2 * Copyright (c) 2015-2016, ARM Limited and Contributors. All rights reserved. 3 * 4 * SPDX-License-Identifier: BSD-3-Clause 5 */ 6 7 #include <assert.h> 8 #include <auth_common.h> 9 #include <auth_mod.h> 10 #include <cot_def.h> 11 #include <crypto_mod.h> 12 #include <debug.h> 13 #include <img_parser_mod.h> 14 #include <platform.h> 15 #include <platform_def.h> 16 #include <stdint.h> 17 #include <string.h> 18 19 /* ASN.1 tags */ 20 #define ASN1_INTEGER 0x02 21 22 #define return_if_error(rc) \ 23 do { \ 24 if (rc != 0) { \ 25 return rc; \ 26 } \ 27 } while (0) 28 29 #pragma weak plat_set_nv_ctr2 30 31 /* Pointer to CoT */ 32 extern const auth_img_desc_t *const cot_desc_ptr; 33 extern unsigned int auth_img_flags[]; 34 35 static int cmp_auth_param_type_desc(const auth_param_type_desc_t *a, 36 const auth_param_type_desc_t *b) 37 { 38 if ((a->type == b->type) && (a->cookie == b->cookie)) { 39 return 0; 40 } 41 return 1; 42 } 43 44 /* 45 * This function obtains the requested authentication parameter data from the 46 * information extracted from the parent image after its authentication. 47 */ 48 static int auth_get_param(const auth_param_type_desc_t *param_type_desc, 49 const auth_img_desc_t *img_desc, 50 void **param, unsigned int *len) 51 { 52 int i; 53 54 for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) { 55 if (0 == cmp_auth_param_type_desc(param_type_desc, 56 img_desc->authenticated_data[i].type_desc)) { 57 *param = img_desc->authenticated_data[i].data.ptr; 58 *len = img_desc->authenticated_data[i].data.len; 59 return 0; 60 } 61 } 62 63 return 1; 64 } 65 66 /* 67 * Authenticate an image by matching the data hash 68 * 69 * This function implements 'AUTH_METHOD_HASH'. To authenticate an image using 70 * this method, the image must contain: 71 * 72 * - The data to calculate the hash from 73 * 74 * The parent image must contain: 75 * 76 * - The hash to be matched with (including hash algorithm) 77 * 78 * For a successful authentication, both hashes must match. The function calls 79 * the crypto-module to check this matching. 80 * 81 * Parameters: 82 * param: parameters to perform the hash authentication 83 * img_desc: pointer to image descriptor so we can know the image type 84 * and parent image 85 * img: pointer to image in memory 86 * img_len: length of image (in bytes) 87 * 88 * Return: 89 * 0 = success, Otherwise = error 90 */ 91 static int auth_hash(const auth_method_param_hash_t *param, 92 const auth_img_desc_t *img_desc, 93 void *img, unsigned int img_len) 94 { 95 void *data_ptr, *hash_der_ptr; 96 unsigned int data_len, hash_der_len; 97 int rc = 0; 98 99 /* Get the hash from the parent image. This hash will be DER encoded 100 * and contain the hash algorithm */ 101 rc = auth_get_param(param->hash, img_desc->parent, 102 &hash_der_ptr, &hash_der_len); 103 return_if_error(rc); 104 105 /* Get the data to be hashed from the current image */ 106 rc = img_parser_get_auth_param(img_desc->img_type, param->data, 107 img, img_len, &data_ptr, &data_len); 108 return_if_error(rc); 109 110 /* Ask the crypto module to verify this hash */ 111 rc = crypto_mod_verify_hash(data_ptr, data_len, 112 hash_der_ptr, hash_der_len); 113 114 return rc; 115 } 116 117 /* 118 * Authenticate by digital signature 119 * 120 * This function implements 'AUTH_METHOD_SIG'. To authenticate an image using 121 * this method, the image must contain: 122 * 123 * - Data to be signed 124 * - Signature 125 * - Signature algorithm 126 * 127 * We rely on the image parser module to extract this data from the image. 128 * The parent image must contain: 129 * 130 * - Public key (or a hash of it) 131 * 132 * If the parent image contains only a hash of the key, we will try to obtain 133 * the public key from the image itself (i.e. self-signed certificates). In that 134 * case, the signature verification is considered just an integrity check and 135 * the authentication is established by calculating the hash of the key and 136 * comparing it with the hash obtained from the parent. 137 * 138 * If the image has no parent (NULL), it means it has to be authenticated using 139 * the ROTPK stored in the platform. Again, this ROTPK could be the key itself 140 * or a hash of it. 141 * 142 * Return: 0 = success, Otherwise = error 143 */ 144 static int auth_signature(const auth_method_param_sig_t *param, 145 const auth_img_desc_t *img_desc, 146 void *img, unsigned int img_len) 147 { 148 void *data_ptr, *pk_ptr, *pk_hash_ptr, *sig_ptr, *sig_alg_ptr; 149 unsigned int data_len, pk_len, pk_hash_len, sig_len, sig_alg_len; 150 unsigned int flags = 0; 151 int rc = 0; 152 153 /* Get the data to be signed from current image */ 154 rc = img_parser_get_auth_param(img_desc->img_type, param->data, 155 img, img_len, &data_ptr, &data_len); 156 return_if_error(rc); 157 158 /* Get the signature from current image */ 159 rc = img_parser_get_auth_param(img_desc->img_type, param->sig, 160 img, img_len, &sig_ptr, &sig_len); 161 return_if_error(rc); 162 163 /* Get the signature algorithm from current image */ 164 rc = img_parser_get_auth_param(img_desc->img_type, param->alg, 165 img, img_len, &sig_alg_ptr, &sig_alg_len); 166 return_if_error(rc); 167 168 /* Get the public key from the parent. If there is no parent (NULL), 169 * the certificate has been signed with the ROTPK, so we have to get 170 * the PK from the platform */ 171 if (img_desc->parent) { 172 rc = auth_get_param(param->pk, img_desc->parent, 173 &pk_ptr, &pk_len); 174 } else { 175 rc = plat_get_rotpk_info(param->pk->cookie, &pk_ptr, &pk_len, 176 &flags); 177 } 178 return_if_error(rc); 179 180 if (flags & (ROTPK_IS_HASH | ROTPK_NOT_DEPLOYED)) { 181 /* If the PK is a hash of the key or if the ROTPK is not 182 deployed on the platform, retrieve the key from the image */ 183 pk_hash_ptr = pk_ptr; 184 pk_hash_len = pk_len; 185 rc = img_parser_get_auth_param(img_desc->img_type, 186 param->pk, img, img_len, 187 &pk_ptr, &pk_len); 188 return_if_error(rc); 189 190 /* Ask the crypto module to verify the signature */ 191 rc = crypto_mod_verify_signature(data_ptr, data_len, 192 sig_ptr, sig_len, 193 sig_alg_ptr, sig_alg_len, 194 pk_ptr, pk_len); 195 return_if_error(rc); 196 197 if (flags & ROTPK_NOT_DEPLOYED) { 198 NOTICE("ROTPK is not deployed on platform. " 199 "Skipping ROTPK verification.\n"); 200 } else { 201 /* Ask the crypto-module to verify the key hash */ 202 rc = crypto_mod_verify_hash(pk_ptr, pk_len, 203 pk_hash_ptr, pk_hash_len); 204 } 205 } else { 206 /* Ask the crypto module to verify the signature */ 207 rc = crypto_mod_verify_signature(data_ptr, data_len, 208 sig_ptr, sig_len, 209 sig_alg_ptr, sig_alg_len, 210 pk_ptr, pk_len); 211 } 212 213 return rc; 214 } 215 216 /* 217 * Authenticate by Non-Volatile counter 218 * 219 * To protect the system against rollback, the platform includes a non-volatile 220 * counter whose value can only be increased. All certificates include a counter 221 * value that should not be lower than the value stored in the platform. If the 222 * value is larger, the counter in the platform must be updated to the new 223 * value. 224 * 225 * Return: 0 = success, Otherwise = error 226 */ 227 static int auth_nvctr(const auth_method_param_nv_ctr_t *param, 228 const auth_img_desc_t *img_desc, 229 void *img, unsigned int img_len) 230 { 231 char *p; 232 void *data_ptr = NULL; 233 unsigned int data_len, len, i; 234 unsigned int cert_nv_ctr, plat_nv_ctr; 235 int rc = 0; 236 237 /* Get the counter value from current image. The AM expects the IPM 238 * to return the counter value as a DER encoded integer */ 239 rc = img_parser_get_auth_param(img_desc->img_type, param->cert_nv_ctr, 240 img, img_len, &data_ptr, &data_len); 241 return_if_error(rc); 242 243 /* Parse the DER encoded integer */ 244 assert(data_ptr); 245 p = (char *)data_ptr; 246 if (*p != ASN1_INTEGER) { 247 /* Invalid ASN.1 integer */ 248 return 1; 249 } 250 p++; 251 252 /* NV-counters are unsigned integers up to 32-bit */ 253 len = (unsigned int)(*p & 0x7f); 254 if ((*p & 0x80) || (len > 4)) { 255 return 1; 256 } 257 p++; 258 259 /* Check the number is not negative */ 260 if (*p & 0x80) { 261 return 1; 262 } 263 264 /* Convert to unsigned int. This code is for a little-endian CPU */ 265 cert_nv_ctr = 0; 266 for (i = 0; i < len; i++) { 267 cert_nv_ctr = (cert_nv_ctr << 8) | *p++; 268 } 269 270 /* Get the counter from the platform */ 271 rc = plat_get_nv_ctr(param->plat_nv_ctr->cookie, &plat_nv_ctr); 272 return_if_error(rc); 273 274 if (cert_nv_ctr < plat_nv_ctr) { 275 /* Invalid NV-counter */ 276 return 1; 277 } else if (cert_nv_ctr > plat_nv_ctr) { 278 rc = plat_set_nv_ctr2(param->plat_nv_ctr->cookie, 279 img_desc, cert_nv_ctr); 280 return_if_error(rc); 281 } 282 283 return 0; 284 } 285 286 int plat_set_nv_ctr2(void *cookie, const auth_img_desc_t *img_desc __unused, 287 unsigned int nv_ctr) 288 { 289 return plat_set_nv_ctr(cookie, nv_ctr); 290 } 291 292 /* 293 * Return the parent id in the output parameter '*parent_id' 294 * 295 * Return value: 296 * 0 = Image has parent, 1 = Image has no parent or parent is authenticated 297 */ 298 int auth_mod_get_parent_id(unsigned int img_id, unsigned int *parent_id) 299 { 300 const auth_img_desc_t *img_desc = NULL; 301 302 assert(parent_id != NULL); 303 304 /* Get the image descriptor */ 305 img_desc = &cot_desc_ptr[img_id]; 306 307 /* Check if the image has no parent (ROT) */ 308 if (img_desc->parent == NULL) { 309 *parent_id = 0; 310 return 1; 311 } 312 313 /* Check if the parent has already been authenticated */ 314 if (auth_img_flags[img_desc->parent->img_id] & IMG_FLAG_AUTHENTICATED) { 315 *parent_id = 0; 316 return 1; 317 } 318 319 *parent_id = img_desc->parent->img_id; 320 return 0; 321 } 322 323 /* 324 * Initialize the different modules in the authentication framework 325 */ 326 void auth_mod_init(void) 327 { 328 /* Check we have a valid CoT registered */ 329 assert(cot_desc_ptr != NULL); 330 331 /* Crypto module */ 332 crypto_mod_init(); 333 334 /* Image parser module */ 335 img_parser_init(); 336 } 337 338 /* 339 * Authenticate a certificate/image 340 * 341 * Return: 0 = success, Otherwise = error 342 */ 343 int auth_mod_verify_img(unsigned int img_id, 344 void *img_ptr, 345 unsigned int img_len) 346 { 347 const auth_img_desc_t *img_desc = NULL; 348 const auth_method_desc_t *auth_method = NULL; 349 void *param_ptr; 350 unsigned int param_len; 351 int rc, i; 352 353 /* Get the image descriptor from the chain of trust */ 354 img_desc = &cot_desc_ptr[img_id]; 355 356 /* Ask the parser to check the image integrity */ 357 rc = img_parser_check_integrity(img_desc->img_type, img_ptr, img_len); 358 return_if_error(rc); 359 360 /* Authenticate the image using the methods indicated in the image 361 * descriptor. */ 362 for (i = 0 ; i < AUTH_METHOD_NUM ; i++) { 363 auth_method = &img_desc->img_auth_methods[i]; 364 switch (auth_method->type) { 365 case AUTH_METHOD_NONE: 366 rc = 0; 367 break; 368 case AUTH_METHOD_HASH: 369 rc = auth_hash(&auth_method->param.hash, 370 img_desc, img_ptr, img_len); 371 break; 372 case AUTH_METHOD_SIG: 373 rc = auth_signature(&auth_method->param.sig, 374 img_desc, img_ptr, img_len); 375 break; 376 case AUTH_METHOD_NV_CTR: 377 rc = auth_nvctr(&auth_method->param.nv_ctr, 378 img_desc, img_ptr, img_len); 379 break; 380 default: 381 /* Unknown authentication method */ 382 rc = 1; 383 break; 384 } 385 return_if_error(rc); 386 } 387 388 /* Extract the parameters indicated in the image descriptor to 389 * authenticate the children images. */ 390 for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) { 391 if (img_desc->authenticated_data[i].type_desc == NULL) { 392 continue; 393 } 394 395 /* Get the parameter from the image parser module */ 396 rc = img_parser_get_auth_param(img_desc->img_type, 397 img_desc->authenticated_data[i].type_desc, 398 img_ptr, img_len, ¶m_ptr, ¶m_len); 399 return_if_error(rc); 400 401 /* Check parameter size */ 402 if (param_len > img_desc->authenticated_data[i].data.len) { 403 return 1; 404 } 405 406 /* Copy the parameter for later use */ 407 memcpy((void *)img_desc->authenticated_data[i].data.ptr, 408 (void *)param_ptr, param_len); 409 } 410 411 /* Mark image as authenticated */ 412 auth_img_flags[img_desc->img_id] |= IMG_FLAG_AUTHENTICATED; 413 414 return 0; 415 } 416
