1 /* Copyright (c) 2013 The Chromium OS Authors. All rights reserved. 2 * Use of this source code is governed by a BSD-style license that can be 3 * found in the LICENSE file. 4 * 5 * Functions for loading a kernel from disk. 6 * (Firmware portion) 7 */ 8 9 #include "sysincludes.h" 10 11 #include "cgptlib.h" 12 #include "cgptlib_internal.h" 13 #include "region.h" 14 #include "gbb_access.h" 15 #include "gbb_header.h" 16 #include "gpt_misc.h" 17 #include "load_kernel_fw.h" 18 #include "utility.h" 19 #include "vboot_api.h" 20 #include "vboot_common.h" 21 #include "vboot_kernel.h" 22 23 #define KBUF_SIZE 65536 /* Bytes to read at start of kernel partition */ 24 #define LOWEST_TPM_VERSION 0xffffffff 25 26 typedef enum BootMode { 27 kBootRecovery = 0, /* Recovery firmware, any dev switch position */ 28 kBootNormal = 1, /* Normal boot - kernel must be verified */ 29 kBootDev = 2 /* Developer boot - self-signed kernel ok */ 30 } BootMode; 31 32 VbError_t LoadKernel(LoadKernelParams *params, VbCommonParams *cparams) 33 { 34 VbSharedDataHeader *shared = 35 (VbSharedDataHeader *)params->shared_data_blob; 36 VbSharedDataKernelCall *shcall = NULL; 37 VbNvContext* vnc = params->nv_context; 38 VbPublicKey* kernel_subkey = NULL; 39 int free_kernel_subkey = 0; 40 GptData gpt; 41 uint64_t part_start, part_size; 42 uint64_t blba; 43 uint64_t kbuf_sectors; 44 uint8_t* kbuf = NULL; 45 int found_partitions = 0; 46 int good_partition = -1; 47 int good_partition_key_block_valid = 0; 48 uint32_t lowest_version = LOWEST_TPM_VERSION; 49 int rec_switch, dev_switch; 50 BootMode boot_mode; 51 uint32_t require_official_os = 0; 52 uint32_t body_toread; 53 uint8_t *body_readptr; 54 55 VbError_t retval = VBERROR_UNKNOWN; 56 int recovery = VBNV_RECOVERY_LK_UNSPECIFIED; 57 58 /* Sanity Checks */ 59 if (!params->bytes_per_lba || 60 !params->streaming_lba_count) { 61 VBDEBUG(("LoadKernel() called with invalid params\n")); 62 retval = VBERROR_INVALID_PARAMETER; 63 goto LoadKernelExit; 64 } 65 66 /* Clear output params in case we fail */ 67 params->partition_number = 0; 68 params->bootloader_address = 0; 69 params->bootloader_size = 0; 70 params->flags = 0; 71 72 /* Calculate switch positions and boot mode */ 73 rec_switch = (BOOT_FLAG_RECOVERY & params->boot_flags ? 1 : 0); 74 dev_switch = (BOOT_FLAG_DEVELOPER & params->boot_flags ? 1 : 0); 75 if (rec_switch) { 76 boot_mode = kBootRecovery; 77 } else if (dev_switch) { 78 boot_mode = kBootDev; 79 VbNvGet(vnc, VBNV_DEV_BOOT_SIGNED_ONLY, &require_official_os); 80 } else { 81 boot_mode = kBootNormal; 82 } 83 84 /* 85 * Set up tracking for this call. This wraps around if called many 86 * times, so we need to initialize the call entry each time. 87 */ 88 shcall = shared->lk_calls + (shared->lk_call_count 89 & (VBSD_MAX_KERNEL_CALLS - 1)); 90 Memset(shcall, 0, sizeof(VbSharedDataKernelCall)); 91 shcall->boot_flags = (uint32_t)params->boot_flags; 92 shcall->boot_mode = boot_mode; 93 shcall->sector_size = (uint32_t)params->bytes_per_lba; 94 shcall->sector_count = params->streaming_lba_count; 95 shared->lk_call_count++; 96 97 /* Initialization */ 98 blba = params->bytes_per_lba; 99 kbuf_sectors = KBUF_SIZE / blba; 100 if (0 == kbuf_sectors) { 101 VBDEBUG(("LoadKernel() called with sector size > KBUF_SIZE\n")); 102 retval = VBERROR_INVALID_PARAMETER; 103 goto LoadKernelExit; 104 } 105 106 if (kBootRecovery == boot_mode) { 107 /* Use the recovery key to verify the kernel */ 108 retval = VbGbbReadRecoveryKey(cparams, &kernel_subkey); 109 if (VBERROR_SUCCESS != retval) 110 goto LoadKernelExit; 111 free_kernel_subkey = 1; 112 } else { 113 /* Use the kernel subkey passed from LoadFirmware(). */ 114 kernel_subkey = &shared->kernel_subkey; 115 } 116 117 /* Read GPT data */ 118 gpt.sector_bytes = (uint32_t)blba; 119 gpt.streaming_drive_sectors = params->streaming_lba_count; 120 gpt.gpt_drive_sectors = params->gpt_lba_count; 121 gpt.flags = params->boot_flags & BOOT_FLAG_EXTERNAL_GPT 122 ? GPT_FLAG_EXTERNAL : 0; 123 if (0 != AllocAndReadGptData(params->disk_handle, &gpt)) { 124 VBDEBUG(("Unable to read GPT data\n")); 125 shcall->check_result = VBSD_LKC_CHECK_GPT_READ_ERROR; 126 goto bad_gpt; 127 } 128 129 /* Initialize GPT library */ 130 if (GPT_SUCCESS != GptInit(&gpt)) { 131 VBDEBUG(("Error parsing GPT\n")); 132 shcall->check_result = VBSD_LKC_CHECK_GPT_PARSE_ERROR; 133 goto bad_gpt; 134 } 135 136 /* Allocate kernel header buffers */ 137 kbuf = (uint8_t*)VbExMalloc(KBUF_SIZE); 138 if (!kbuf) 139 goto bad_gpt; 140 141 /* Loop over candidate kernel partitions */ 142 while (GPT_SUCCESS == 143 GptNextKernelEntry(&gpt, &part_start, &part_size)) { 144 VbSharedDataKernelPart *shpart = NULL; 145 VbKeyBlockHeader *key_block; 146 VbKernelPreambleHeader *preamble; 147 RSAPublicKey *data_key = NULL; 148 VbExStream_t stream = NULL; 149 uint64_t key_version; 150 uint32_t combined_version; 151 uint64_t body_offset; 152 int key_block_valid = 1; 153 154 VBDEBUG(("Found kernel entry at %" PRIu64 " size %" PRIu64 "\n", 155 part_start, part_size)); 156 157 /* 158 * Set up tracking for this partition. This wraps around if 159 * called many times, so initialize the partition entry each 160 * time. 161 */ 162 shpart = shcall->parts + (shcall->kernel_parts_found 163 & (VBSD_MAX_KERNEL_PARTS - 1)); 164 Memset(shpart, 0, sizeof(VbSharedDataKernelPart)); 165 shpart->sector_start = part_start; 166 shpart->sector_count = part_size; 167 /* 168 * TODO: GPT partitions start at 1, but cgptlib starts them at 169 * 0. Adjust here, until cgptlib is fixed. 170 */ 171 shpart->gpt_index = (uint8_t)(gpt.current_kernel + 1); 172 shcall->kernel_parts_found++; 173 174 /* Found at least one kernel partition. */ 175 found_partitions++; 176 177 /* Set up the stream */ 178 if (VbExStreamOpen(params->disk_handle, 179 part_start, part_size, &stream)) { 180 VBDEBUG(("Partition error getting stream.\n")); 181 shpart->check_result = VBSD_LKP_CHECK_TOO_SMALL; 182 goto bad_kernel; 183 } 184 185 if (0 != VbExStreamRead(stream, KBUF_SIZE, kbuf)) { 186 VBDEBUG(("Unable to read start of partition.\n")); 187 shpart->check_result = VBSD_LKP_CHECK_READ_START; 188 goto bad_kernel; 189 } 190 191 /* Verify the key block. */ 192 key_block = (VbKeyBlockHeader*)kbuf; 193 if (0 != KeyBlockVerify(key_block, KBUF_SIZE, 194 kernel_subkey, 0)) { 195 VBDEBUG(("Verifying key block signature failed.\n")); 196 shpart->check_result = VBSD_LKP_CHECK_KEY_BLOCK_SIG; 197 key_block_valid = 0; 198 199 /* If not in developer mode, this kernel is bad. */ 200 if (kBootDev != boot_mode) 201 goto bad_kernel; 202 203 /* 204 * In developer mode, we can explictly disallow 205 * self-signed kernels 206 */ 207 if (require_official_os) { 208 VBDEBUG(("Self-signed kernels not enabled.\n")); 209 shpart->check_result = 210 VBSD_LKP_CHECK_SELF_SIGNED; 211 goto bad_kernel; 212 } 213 214 /* 215 * Allow the kernel if the SHA-512 hash of the key 216 * block is valid. 217 */ 218 if (0 != KeyBlockVerify(key_block, KBUF_SIZE, 219 kernel_subkey, 1)) { 220 VBDEBUG(("Verifying key block hash failed.\n")); 221 shpart->check_result = 222 VBSD_LKP_CHECK_KEY_BLOCK_HASH; 223 goto bad_kernel; 224 } 225 } 226 227 /* Check the key block flags against the current boot mode. */ 228 if (!(key_block->key_block_flags & 229 (dev_switch ? KEY_BLOCK_FLAG_DEVELOPER_1 : 230 KEY_BLOCK_FLAG_DEVELOPER_0))) { 231 VBDEBUG(("Key block developer flag mismatch.\n")); 232 shpart->check_result = VBSD_LKP_CHECK_DEV_MISMATCH; 233 key_block_valid = 0; 234 } 235 if (!(key_block->key_block_flags & 236 (rec_switch ? KEY_BLOCK_FLAG_RECOVERY_1 : 237 KEY_BLOCK_FLAG_RECOVERY_0))) { 238 VBDEBUG(("Key block recovery flag mismatch.\n")); 239 shpart->check_result = VBSD_LKP_CHECK_REC_MISMATCH; 240 key_block_valid = 0; 241 } 242 243 /* Check for rollback of key version except in recovery mode. */ 244 key_version = key_block->data_key.key_version; 245 if (kBootRecovery != boot_mode) { 246 if (key_version < (shared->kernel_version_tpm >> 16)) { 247 VBDEBUG(("Key version too old.\n")); 248 shpart->check_result = 249 VBSD_LKP_CHECK_KEY_ROLLBACK; 250 key_block_valid = 0; 251 } 252 if (key_version > 0xFFFF) { 253 /* 254 * Key version is stored in 16 bits in the TPM, 255 * so key versions greater than 0xFFFF can't be 256 * stored properly. 257 */ 258 VBDEBUG(("Key version > 0xFFFF.\n")); 259 shpart->check_result = 260 VBSD_LKP_CHECK_KEY_ROLLBACK; 261 key_block_valid = 0; 262 } 263 } 264 265 /* If not in developer mode, key block required to be valid. */ 266 if (kBootDev != boot_mode && !key_block_valid) { 267 VBDEBUG(("Key block is invalid.\n")); 268 goto bad_kernel; 269 } 270 271 /* Get key for preamble/data verification from the key block. */ 272 data_key = PublicKeyToRSA(&key_block->data_key); 273 if (!data_key) { 274 VBDEBUG(("Data key bad.\n")); 275 shpart->check_result = VBSD_LKP_CHECK_DATA_KEY_PARSE; 276 goto bad_kernel; 277 } 278 279 /* Verify the preamble, which follows the key block */ 280 preamble = (VbKernelPreambleHeader *) 281 (kbuf + key_block->key_block_size); 282 if ((0 != VerifyKernelPreamble( 283 preamble, 284 KBUF_SIZE - key_block->key_block_size, 285 data_key))) { 286 VBDEBUG(("Preamble verification failed.\n")); 287 shpart->check_result = VBSD_LKP_CHECK_VERIFY_PREAMBLE; 288 goto bad_kernel; 289 } 290 291 /* 292 * If the key block is valid and we're not in recovery mode, 293 * check for rollback of the kernel version. 294 */ 295 combined_version = (uint32_t)( 296 (key_version << 16) | 297 (preamble->kernel_version & 0xFFFF)); 298 shpart->combined_version = combined_version; 299 if (key_block_valid && kBootRecovery != boot_mode) { 300 if (combined_version < shared->kernel_version_tpm) { 301 VBDEBUG(("Kernel version too low.\n")); 302 shpart->check_result = 303 VBSD_LKP_CHECK_KERNEL_ROLLBACK; 304 /* 305 * If not in developer mode, kernel version 306 * must be valid. 307 */ 308 if (kBootDev != boot_mode) 309 goto bad_kernel; 310 } 311 } 312 313 VBDEBUG(("Kernel preamble is good.\n")); 314 shpart->check_result = VBSD_LKP_CHECK_PREAMBLE_VALID; 315 316 /* Check for lowest version from a valid header. */ 317 if (key_block_valid && lowest_version > combined_version) 318 lowest_version = combined_version; 319 else { 320 VBDEBUG(("Key block valid: %d\n", key_block_valid)); 321 VBDEBUG(("Combined version: %u\n", 322 (unsigned) combined_version)); 323 } 324 325 /* 326 * If we already have a good kernel, no need to read another 327 * one; we only needed to look at the versions to check for 328 * rollback. So skip to the next kernel preamble. 329 */ 330 if (-1 != good_partition) { 331 VbExStreamClose(stream); 332 stream = NULL; 333 continue; 334 } 335 336 body_offset = key_block->key_block_size + 337 preamble->preamble_size; 338 339 /* 340 * Make sure the kernel starts at or before what we already 341 * read into kbuf. 342 * 343 * We could deal with a larger offset by reading and discarding 344 * the data in between the vblock and the kernel data. 345 */ 346 if (body_offset > KBUF_SIZE) { 347 shpart->check_result = VBSD_LKP_CHECK_BODY_OFFSET; 348 VBDEBUG(("Kernel body offset is %d > 64KB.\n", 349 (int)body_offset)); 350 goto bad_kernel; 351 } 352 353 if (!params->kernel_buffer) { 354 /* Get kernel load address and size from the header. */ 355 params->kernel_buffer = 356 (void *)((long)preamble->body_load_address); 357 params->kernel_buffer_size = 358 preamble->body_signature.data_size; 359 } else if (preamble->body_signature.data_size > 360 params->kernel_buffer_size) { 361 VBDEBUG(("Kernel body doesn't fit in memory.\n")); 362 shpart->check_result = VBSD_LKP_CHECK_BODY_EXCEEDS_MEM; 363 goto bad_kernel; 364 } 365 366 /* 367 * Body signature data size is 64 bit and toread is 32 bit so 368 * this could technically cause us to read less data. That's 369 * fine, because a 4 GB kernel is implausible, and if we did 370 * have one that big, we'd simply read too little data and fail 371 * to verify it. 372 */ 373 body_toread = preamble->body_signature.data_size; 374 body_readptr = params->kernel_buffer; 375 376 /* 377 * If we've already read part of the kernel, copy that to the 378 * beginning of the kernel buffer. 379 */ 380 if (body_offset < KBUF_SIZE) { 381 uint32_t body_copied = KBUF_SIZE - body_offset; 382 383 /* If the kernel is tiny, don't over-copy */ 384 if (body_copied > body_toread) 385 body_copied = body_toread; 386 387 Memcpy(body_readptr, kbuf + body_offset, body_copied); 388 body_toread -= body_copied; 389 body_readptr += body_copied; 390 } 391 392 /* Read the kernel data */ 393 if (body_toread && 394 0 != VbExStreamRead(stream, body_toread, body_readptr)) { 395 VBDEBUG(("Unable to read kernel data.\n")); 396 shpart->check_result = VBSD_LKP_CHECK_READ_DATA; 397 goto bad_kernel; 398 } 399 400 /* Close the stream; we're done with it */ 401 VbExStreamClose(stream); 402 stream = NULL; 403 404 /* Verify kernel data */ 405 if (0 != VerifyData((const uint8_t *)params->kernel_buffer, 406 params->kernel_buffer_size, 407 &preamble->body_signature, data_key)) { 408 VBDEBUG(("Kernel data verification failed.\n")); 409 shpart->check_result = VBSD_LKP_CHECK_VERIFY_DATA; 410 goto bad_kernel; 411 } 412 413 /* Done with the kernel signing key, so can free it now */ 414 RSAPublicKeyFree(data_key); 415 data_key = NULL; 416 417 /* 418 * If we're still here, the kernel is valid. Save the first 419 * good partition we find; that's the one we'll boot. 420 */ 421 VBDEBUG(("Partition is good.\n")); 422 shpart->check_result = VBSD_LKP_CHECK_KERNEL_GOOD; 423 if (key_block_valid) 424 shpart->flags |= VBSD_LKP_FLAG_KEY_BLOCK_VALID; 425 426 good_partition_key_block_valid = key_block_valid; 427 /* 428 * TODO: GPT partitions start at 1, but cgptlib starts them at 429 * 0. Adjust here, until cgptlib is fixed. 430 */ 431 good_partition = gpt.current_kernel + 1; 432 params->partition_number = gpt.current_kernel + 1; 433 GetCurrentKernelUniqueGuid(&gpt, ¶ms->partition_guid); 434 /* 435 * TODO: GetCurrentKernelUniqueGuid() should take a destination 436 * size, or the dest should be a struct, so we know it's big 437 * enough. 438 */ 439 params->bootloader_address = preamble->bootloader_address; 440 params->bootloader_size = preamble->bootloader_size; 441 if (VbKernelHasFlags(preamble) == VBOOT_SUCCESS) 442 params->flags = preamble->flags; 443 444 /* Update GPT to note this is the kernel we're trying */ 445 GptUpdateKernelEntry(&gpt, GPT_UPDATE_ENTRY_TRY); 446 447 /* 448 * If we're in recovery mode or we're about to boot a 449 * dev-signed kernel, there's no rollback protection, so we can 450 * stop at the first valid kernel. 451 */ 452 if (kBootRecovery == boot_mode || !key_block_valid) { 453 VBDEBUG(("In recovery mode or dev-signed kernel\n")); 454 break; 455 } 456 457 /* 458 * Otherwise, we do care about the key index in the TPM. If 459 * the good partition's key version is the same as the tpm, 460 * then the TPM doesn't need updating; we can stop now. 461 * Otherwise, we'll check all the other headers to see if they 462 * contain a newer key. 463 */ 464 if (combined_version == shared->kernel_version_tpm) { 465 VBDEBUG(("Same kernel version\n")); 466 break; 467 } 468 469 /* Continue, so that we skip the error handling code below */ 470 continue; 471 472 bad_kernel: 473 /* Handle errors parsing this kernel */ 474 if (NULL != stream) 475 VbExStreamClose(stream); 476 if (NULL != data_key) 477 RSAPublicKeyFree(data_key); 478 479 VBDEBUG(("Marking kernel as invalid.\n")); 480 GptUpdateKernelEntry(&gpt, GPT_UPDATE_ENTRY_BAD); 481 482 483 } /* while(GptNextKernelEntry) */ 484 485 bad_gpt: 486 487 /* Free kernel buffer */ 488 if (kbuf) 489 VbExFree(kbuf); 490 491 /* Write and free GPT data */ 492 WriteAndFreeGptData(params->disk_handle, &gpt); 493 494 /* Handle finding a good partition */ 495 if (good_partition >= 0) { 496 VBDEBUG(("Good_partition >= 0\n")); 497 shcall->check_result = VBSD_LKC_CHECK_GOOD_PARTITION; 498 shared->kernel_version_lowest = lowest_version; 499 /* 500 * Sanity check - only store a new TPM version if we found one. 501 * If lowest_version is still at its initial value, we didn't 502 * find one; for example, we're in developer mode and just 503 * didn't look. 504 */ 505 if (lowest_version != LOWEST_TPM_VERSION && 506 lowest_version > shared->kernel_version_tpm) 507 shared->kernel_version_tpm = lowest_version; 508 509 /* Success! */ 510 retval = VBERROR_SUCCESS; 511 } else if (found_partitions > 0) { 512 shcall->check_result = VBSD_LKC_CHECK_INVALID_PARTITIONS; 513 recovery = VBNV_RECOVERY_RW_INVALID_OS; 514 retval = VBERROR_INVALID_KERNEL_FOUND; 515 } else { 516 shcall->check_result = VBSD_LKC_CHECK_NO_PARTITIONS; 517 recovery = VBNV_RECOVERY_RW_NO_OS; 518 retval = VBERROR_NO_KERNEL_FOUND; 519 } 520 521 LoadKernelExit: 522 523 /* Store recovery request, if any */ 524 VbNvSet(vnc, VBNV_RECOVERY_REQUEST, VBERROR_SUCCESS != retval ? 525 recovery : VBNV_RECOVERY_NOT_REQUESTED); 526 527 /* 528 * If LoadKernel() was called with bad parameters, shcall may not be 529 * initialized. 530 */ 531 if (shcall) 532 shcall->return_code = (uint8_t)retval; 533 534 /* Save whether the good partition's key block was fully verified */ 535 if (good_partition_key_block_valid) 536 shared->flags |= VBSD_KERNEL_KEY_VERIFIED; 537 538 /* Store how much shared data we used, if any */ 539 params->shared_data_size = shared->data_used; 540 541 if (free_kernel_subkey) 542 VbExFree(kernel_subkey); 543 544 return retval; 545 } 546
