blob: 23ea913663b5051f847f8b6241cdf4fd592f10fe [file] [log] [blame]
/* 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 "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) {
VBDEBUG(("Updating GPT header 1\n"));
if (0 != BootDeviceWriteLBA(1, 1, gptdata->primary_header))
return 1;
}
Free(gptdata->primary_header);
}
if (gptdata->primary_entries) {
if (gptdata->modified & GPT_MODIFIED_ENTRIES1) {
VBDEBUG(("Updating GPT entries 1\n"));
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) {
VBDEBUG(("Updating GPT header 2\n"));
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) {
VBDEBUG(("Updating GPT entries 2\n"));
if (0 != BootDeviceWriteLBA(gptdata->drive_sectors - 1, 1,
gptdata->secondary_header))
return 1;
}
Free(gptdata->secondary_header);
}
/* Success */
return 0;
}
/* disable MSVC warning on const logical expression (as in } while(0);) */
__pragma(warning(disable: 4127))
int LoadKernel(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 ? 1 : 0);
int is_rec = (BOOT_FLAG_RECOVERY & params->boot_flags ? 1 : 0);
int is_normal = (!is_dev && !is_rec);
/* Clear output params in case we fail */
params->partition_number = 0;
params->bootloader_address = 0;
params->bootloader_size = 0;
/* Let the TPM know if we're in recovery mode */
if (is_rec) {
if (0 != RollbackKernelRecovery(is_dev ? 1 : 0)) {
VBDEBUG(("Error setting up TPM for recovery kernel\n"));
/* Ignore return code, since we need to boot recovery mode to
* fix the TPM. */
}
}
if (is_normal) {
/* Read current kernel key index from TPM. Assumes TPM is already
* initialized. */
if (0 != RollbackKernelRead(&tpm_key_version, &tpm_kernel_version)) {
VBDEBUG(("Unable to get kernel versions from TPM\n"));
return LOAD_KERNEL_RECOVERY;
}
} else if (is_dev && !is_rec) {
/* 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 = (uint32_t)blba;
gpt.drive_sectors = params->ending_lba + 1;
if (0 != AllocAndReadGptData(&gpt)) {
VBDEBUG(("Unable to read GPT data\n"));
break;
}
/* Initialize GPT library */
if (GPT_SUCCESS != GptInit(&gpt)) {
VBDEBUG(("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;
VBDEBUG(("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))) {
VBDEBUG(("Verifying key block failed.\n"));
continue;
}
/* Check the key block flags against the current boot mode */
if (!(key_block->key_block_flags &
(is_dev ? KEY_BLOCK_FLAG_DEVELOPER_1 :
KEY_BLOCK_FLAG_DEVELOPER_0))) {
VBDEBUG(("Developer flag mismatch.\n"));
continue;
}
if (!(key_block->key_block_flags &
(is_rec ? KEY_BLOCK_FLAG_RECOVERY_1 :
KEY_BLOCK_FLAG_RECOVERY_0))) {
VBDEBUG(("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) {
VBDEBUG(("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))) {
VBDEBUG(("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) {
VBDEBUG(("Kernel version too low.\n"));
RSAPublicKeyFree(data_key);
continue;
}
VBDEBUG(("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)) {
VBDEBUG(("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) {
VBDEBUG(("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) {
VBDEBUG(("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)) {
VBDEBUG(("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)) {
VBDEBUG(("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 */
VBDEBUG(("Partiton is good.\n"));
/* TODO: GPT partitions start at 1, but cgptlib starts them at 0.
* Adjust here, until cgptlib is fixed. */
good_partition = gpt.current_kernel + 1;
params->partition_number = gpt.current_kernel + 1;
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) {
VBDEBUG(("Boot_flags = !is_normal\n"));
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) {
VBDEBUG(("Same key version\n"));
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) {
VBDEBUG(("Good_partition >= 0\n"));
/* 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. */
VBDEBUG(("Boot_flags = is_normal\n"));
if ((lowest_key_version > tpm_key_version) ||
(lowest_key_version == tpm_key_version &&
lowest_kernel_version > tpm_kernel_version)) {
if (0 != RollbackKernelWrite((uint16_t)lowest_key_version,
(uint16_t)lowest_kernel_version)) {
VBDEBUG(("Error writing kernel versions to TPM.\n"));
return LOAD_KERNEL_RECOVERY;
}
}
}
/* Lock the kernel versions */
if (0 != RollbackKernelLock()) {
VBDEBUG(("Error locking kernel versions.\n"));
/* Don't reboot to recovery mode if we're already there */
if (!is_rec)
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;
}