| /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved. |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| * |
| * Functions for loading a kernel from disk. |
| * (Firmware portion) |
| */ |
| |
| #include "vboot_kernel.h" |
| |
| #include <inttypes.h> /* For PRIu64 */ |
| #include "boot_device.h" |
| #include "cgptlib.h" |
| #include "load_kernel_fw.h" |
| #include "rollback_index.h" |
| #include "utility.h" |
| #include "vboot_common.h" |
| |
| |
| #define KBUF_SIZE 65536 /* Bytes to read at start of kernel partition */ |
| |
| |
| /* Allocates and reads GPT data from the drive. The sector_bytes and |
| * drive_sectors fields should be filled on input. The primary and |
| * secondary header and entries are filled on output. |
| * |
| * Returns 0 if successful, 1 if error. */ |
| int AllocAndReadGptData(GptData* gptdata) { |
| |
| uint64_t entries_sectors = TOTAL_ENTRIES_SIZE / gptdata->sector_bytes; |
| |
| /* No data to be written yet */ |
| gptdata->modified = 0; |
| |
| /* Allocate all buffers */ |
| gptdata->primary_header = (uint8_t*)Malloc(gptdata->sector_bytes); |
| gptdata->secondary_header = (uint8_t*)Malloc(gptdata->sector_bytes); |
| gptdata->primary_entries = (uint8_t*)Malloc(TOTAL_ENTRIES_SIZE); |
| gptdata->secondary_entries = (uint8_t*)Malloc(TOTAL_ENTRIES_SIZE); |
| |
| if (gptdata->primary_header == NULL || gptdata->secondary_header == NULL || |
| gptdata->primary_entries == NULL || gptdata->secondary_entries == NULL) |
| return 1; |
| |
| /* Read data from the drive, skipping the protective MBR */ |
| if (0 != BootDeviceReadLBA(1, 1, gptdata->primary_header)) |
| return 1; |
| if (0 != BootDeviceReadLBA(2, entries_sectors, gptdata->primary_entries)) |
| return 1; |
| if (0 != BootDeviceReadLBA(gptdata->drive_sectors - entries_sectors - 1, |
| entries_sectors, gptdata->secondary_entries)) |
| return 1; |
| if (0 != BootDeviceReadLBA(gptdata->drive_sectors - 1, |
| 1, gptdata->secondary_header)) |
| return 1; |
| |
| return 0; |
| } |
| |
| |
| /* Writes any changes for the GPT data back to the drive, then frees |
| * the buffers. |
| * |
| * Returns 0 if successful, 1 if error. */ |
| int WriteAndFreeGptData(GptData* gptdata) { |
| |
| uint64_t entries_sectors = TOTAL_ENTRIES_SIZE / gptdata->sector_bytes; |
| |
| if (gptdata->primary_header) { |
| if (gptdata->modified & GPT_MODIFIED_HEADER1) { |
| if (0 != BootDeviceWriteLBA(1, 1, gptdata->primary_header)) |
| return 1; |
| } |
| Free(gptdata->primary_header); |
| } |
| |
| if (gptdata->primary_entries) { |
| if (gptdata->modified & GPT_MODIFIED_ENTRIES1) { |
| if (0 != BootDeviceWriteLBA(2, entries_sectors, |
| gptdata->primary_entries)) |
| return 1; |
| } |
| Free(gptdata->primary_entries); |
| } |
| |
| if (gptdata->secondary_entries) { |
| if (gptdata->modified & GPT_MODIFIED_ENTRIES2) { |
| if (0 != BootDeviceWriteLBA(gptdata->drive_sectors - entries_sectors - 1, |
| entries_sectors, gptdata->secondary_entries)) |
| return 1; |
| } |
| Free(gptdata->secondary_entries); |
| } |
| |
| if (gptdata->secondary_header) { |
| if (gptdata->modified & GPT_MODIFIED_HEADER2) { |
| if (0 != BootDeviceWriteLBA(gptdata->drive_sectors - 1, 1, |
| gptdata->secondary_header)) |
| return 1; |
| } |
| Free(gptdata->secondary_header); |
| } |
| |
| /* Success */ |
| return 0; |
| } |
| |
| |
| int LoadKernel2(LoadKernelParams* params) { |
| |
| VbPublicKey* kernel_subkey = (VbPublicKey*)params->header_sign_key_blob; |
| |
| GptData gpt; |
| uint64_t part_start, part_size; |
| uint64_t blba = params->bytes_per_lba; |
| uint64_t kbuf_sectors = KBUF_SIZE / blba; |
| uint8_t* kbuf = NULL; |
| int found_partitions = 0; |
| int good_partition = -1; |
| uint16_t tpm_key_version = 0; |
| uint16_t tpm_kernel_version = 0; |
| uint64_t lowest_key_version = 0xFFFF; |
| uint64_t lowest_kernel_version = 0xFFFF; |
| int is_dev = ((BOOT_FLAG_DEVELOPER & params->boot_flags) && |
| !(BOOT_FLAG_RECOVERY & params->boot_flags)); |
| int is_normal = (!(BOOT_FLAG_DEVELOPER & params->boot_flags) && |
| !(BOOT_FLAG_RECOVERY & params->boot_flags)); |
| |
| /* Clear output params in case we fail */ |
| params->partition_number = 0; |
| params->bootloader_address = 0; |
| params->bootloader_size = 0; |
| |
| if (is_normal) { |
| /* Read current kernel key index from TPM. Assumes TPM is already |
| * initialized. */ |
| if (0 != GetStoredVersions(KERNEL_VERSIONS, |
| &tpm_key_version, |
| &tpm_kernel_version)) { |
| debug("Unable to get stored version from TPM\n"); |
| return LOAD_KERNEL_RECOVERY; |
| } |
| } else if (is_dev) { |
| /* In developer mode, we ignore the kernel subkey, and just use |
| * the SHA-512 hash to verify the key block. */ |
| kernel_subkey = NULL; |
| } |
| |
| do { |
| /* Read GPT data */ |
| gpt.sector_bytes = blba; |
| gpt.drive_sectors = params->ending_lba + 1; |
| if (0 != AllocAndReadGptData(&gpt)) { |
| debug("Unable to read GPT data\n"); |
| break; |
| } |
| |
| /* Initialize GPT library */ |
| if (GPT_SUCCESS != GptInit(&gpt)) { |
| debug("Error parsing GPT\n"); |
| break; |
| } |
| |
| /* Allocate kernel header buffers */ |
| kbuf = (uint8_t*)Malloc(KBUF_SIZE); |
| if (!kbuf) |
| break; |
| |
| /* Loop over candidate kernel partitions */ |
| while (GPT_SUCCESS == GptNextKernelEntry(&gpt, &part_start, &part_size)) { |
| VbKeyBlockHeader* key_block; |
| VbKernelPreambleHeader* preamble; |
| RSAPublicKey* data_key; |
| uint64_t key_version; |
| uint64_t body_offset; |
| |
| debug("Found kernel entry at %" PRIu64 " size %" PRIu64 "\n", |
| part_start, part_size); |
| |
| /* Found at least one kernel partition. */ |
| found_partitions++; |
| |
| /* Read the first part of the kernel partition */ |
| if (part_size < kbuf_sectors) |
| continue; |
| if (0 != BootDeviceReadLBA(part_start, kbuf_sectors, kbuf)) |
| continue; |
| |
| /* Verify the key block */ |
| key_block = (VbKeyBlockHeader*)kbuf; |
| if ((0 != KeyBlockVerify(key_block, KBUF_SIZE, kernel_subkey))) { |
| debug("Verifying key block failed.\n"); |
| continue; |
| } |
| |
| /* Check the key block flags against the current boot mode */ |
| if (!(key_block->key_block_flags && |
| ((BOOT_FLAG_DEVELOPER & params->boot_flags) ? |
| KEY_BLOCK_FLAG_DEVELOPER_1 : KEY_BLOCK_FLAG_DEVELOPER_0))) { |
| debug("Developer flag mismatch.\n"); |
| continue; |
| } |
| if (!(key_block->key_block_flags && |
| ((BOOT_FLAG_RECOVERY & params->boot_flags) ? |
| KEY_BLOCK_FLAG_RECOVERY_1 : KEY_BLOCK_FLAG_RECOVERY_0))) { |
| debug("Recovery flag mismatch.\n"); |
| continue; |
| } |
| |
| /* Check for rollback of key version. Note this is implicitly |
| * skipped in recovery and developer modes because those set |
| * key_version=0 above. */ |
| key_version = key_block->data_key.key_version; |
| if (key_version < tpm_key_version) { |
| debug("Key version too old.\n"); |
| continue; |
| } |
| |
| /* Get the key for preamble/data verification from the key block */ |
| data_key = PublicKeyToRSA(&key_block->data_key); |
| if (!data_key) |
| continue; |
| |
| /* Verify the preamble, which follows the key block */ |
| preamble = (VbKernelPreambleHeader*)(kbuf + key_block->key_block_size); |
| if ((0 != VerifyKernelPreamble2(preamble, |
| KBUF_SIZE - key_block->key_block_size, |
| data_key))) { |
| debug("Preamble verification failed.\n"); |
| RSAPublicKeyFree(data_key); |
| continue; |
| } |
| |
| /* Check for rollback of kernel version. Note this is implicitly |
| * skipped in recovery and developer modes because those set |
| * key_version=0 and kernel_version=0 above. */ |
| if (key_version == tpm_key_version && |
| preamble->kernel_version < tpm_kernel_version) { |
| debug("Kernel version too low.\n"); |
| RSAPublicKeyFree(data_key); |
| continue; |
| } |
| |
| debug("Kernel preamble is good.\n"); |
| |
| /* Check for lowest key version from a valid header. */ |
| if (lowest_key_version > key_version) { |
| lowest_key_version = key_version; |
| lowest_kernel_version = preamble->kernel_version; |
| } |
| else if (lowest_key_version == key_version && |
| lowest_kernel_version > preamble->kernel_version) { |
| lowest_kernel_version = preamble->kernel_version; |
| } |
| |
| /* If we already have a good kernel, no need to read another |
| * one; we only needed to look at the versions to check for |
| * rollback. */ |
| if (-1 != good_partition) |
| continue; |
| |
| /* Verify body load address matches what we expect */ |
| if ((preamble->body_load_address != (size_t)params->kernel_buffer) && |
| !(params->boot_flags & BOOT_FLAG_SKIP_ADDR_CHECK)) { |
| debug("Wrong body load address.\n"); |
| RSAPublicKeyFree(data_key); |
| continue; |
| } |
| |
| /* Verify kernel body starts at a multiple of the sector size. */ |
| body_offset = key_block->key_block_size + preamble->preamble_size; |
| if (0 != body_offset % blba) { |
| debug("Kernel body not at multiple of sector size.\n"); |
| RSAPublicKeyFree(data_key); |
| continue; |
| } |
| |
| /* Verify kernel body fits in the partition */ |
| if (body_offset + preamble->body_signature.data_size > |
| part_size * blba) { |
| debug("Kernel body doesn't fit in partition.\n"); |
| RSAPublicKeyFree(data_key); |
| continue; |
| } |
| |
| /* Read the kernel data */ |
| if (0 != BootDeviceReadLBA( |
| part_start + (body_offset / blba), |
| (preamble->body_signature.data_size + blba - 1) / blba, |
| params->kernel_buffer)) { |
| debug("Unable to read kernel data.\n"); |
| RSAPublicKeyFree(data_key); |
| continue; |
| } |
| |
| /* Verify kernel data */ |
| if (0 != VerifyData((const uint8_t*)params->kernel_buffer, |
| &preamble->body_signature, data_key)) { |
| debug("Kernel data verification failed.\n"); |
| RSAPublicKeyFree(data_key); |
| continue; |
| } |
| |
| /* Done with the kernel signing key, so can free it now */ |
| RSAPublicKeyFree(data_key); |
| |
| /* If we're still here, the kernel is valid. */ |
| /* Save the first good partition we find; that's the one we'll boot */ |
| debug("Partiton is good.\n"); |
| good_partition = gpt.current_kernel; |
| params->partition_number = gpt.current_kernel; |
| params->bootloader_address = preamble->bootloader_address; |
| params->bootloader_size = preamble->bootloader_size; |
| /* If we're in developer or recovery mode, there's no rollback |
| * protection, so we can stop at the first valid kernel. */ |
| if (!is_normal) |
| break; |
| |
| /* Otherwise, we're in normal boot mode, so we do care about the |
| * key index in the TPM. If the good partition's key version is |
| * the same as the tpm, then the TPM doesn't need updating; we |
| * can stop now. Otherwise, we'll check all the other headers |
| * to see if they contain a newer key. */ |
| if (key_version == tpm_key_version && |
| preamble->kernel_version == tpm_kernel_version) |
| break; |
| } /* while(GptNextKernelEntry) */ |
| } while(0); |
| |
| /* Free kernel buffer */ |
| if (kbuf) |
| Free(kbuf); |
| |
| /* Write and free GPT data */ |
| WriteAndFreeGptData(&gpt); |
| |
| /* Handle finding a good partition */ |
| if (good_partition >= 0) { |
| |
| /* See if we need to update the TPM */ |
| if (is_normal) { |
| /* We only update the TPM in normal boot mode. In developer |
| * mode, the kernel is self-signed by the developer, so we can't |
| * trust the key version and wouldn't want to roll the TPM |
| * forward. In recovery mode, the TPM stays PP-unlocked, so |
| * anything we write gets blown away by the firmware when we go |
| * back to normal mode. */ |
| if ((lowest_key_version > tpm_key_version) || |
| (lowest_key_version == tpm_key_version && |
| lowest_kernel_version > tpm_kernel_version)) { |
| if (0 != WriteStoredVersions(KERNEL_VERSIONS, |
| lowest_key_version, |
| lowest_kernel_version)) |
| return LOAD_KERNEL_RECOVERY; |
| } |
| } |
| |
| if (!(BOOT_FLAG_RECOVERY & params->boot_flags)) { |
| /* We can lock the TPM now, since we've decided which kernel we |
| * like. If we don't find a good kernel, we leave the TPM |
| * unlocked so we can try again on the next boot device. If no |
| * kernels are good, we'll reboot to recovery mode, so it's ok to |
| * leave the TPM unlocked in that case too. |
| * |
| * If we're already in recovery mode, we need to leave PP unlocked, |
| * so don't lock the kernel versions. */ |
| if (0 != LockKernelVersionsByLockingPP()) |
| return LOAD_KERNEL_RECOVERY; |
| } |
| |
| /* Success! */ |
| return LOAD_KERNEL_SUCCESS; |
| } |
| |
| // Handle error cases |
| if (found_partitions) |
| return LOAD_KERNEL_INVALID; |
| else |
| return LOAD_KERNEL_NOT_FOUND; |
| } |