/* Copyright (c) 2011 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 "cgptlib_internal.h" #include "gbb_header.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 */ #define LOWEST_TPM_VERSION 0xffffffff typedef enum BootMode { kBootNormal, /* Normal firmware */ kBootDev, /* Dev firmware AND dev switch is on */ kBootRecovery /* Recovery firmware, regardless of dev switch position */ } BootMode; /* 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) { VbSharedDataHeader* shared = (VbSharedDataHeader*)params->shared_data_blob; VbNvContext* vnc = params->nv_context; GoogleBinaryBlockHeader* gbb = (GoogleBinaryBlockHeader*)params->gbb_data; VbPublicKey* kernel_subkey; GptData gpt; uint64_t part_start, part_size; uint64_t blba; uint64_t kbuf_sectors; uint8_t* kbuf = NULL; int found_partitions = 0; int good_partition = -1; int good_partition_key_block_valid = 0; uint32_t tpm_version = 0; uint64_t lowest_version = LOWEST_TPM_VERSION; int rec_switch, dev_switch; BootMode boot_mode; uint32_t test_err = 0; uint32_t status; int retval = LOAD_KERNEL_RECOVERY; int recovery = VBNV_RECOVERY_RO_UNSPECIFIED; /* Setup NV storage */ VbNvSetup(vnc); /* Sanity Checks */ if (!params || !params->bytes_per_lba || !params->ending_lba || !params->kernel_buffer || !params->kernel_buffer_size) { VBDEBUG(("LoadKernel() called with invalid params\n")); goto LoadKernelExit; } /* Handle test errors */ VbNvGet(vnc, VBNV_TEST_ERROR_FUNC, &test_err); if (VBNV_TEST_ERROR_LOAD_KERNEL == test_err) { /* Get error code */ VbNvGet(vnc, VBNV_TEST_ERROR_NUM, &test_err); /* Clear test params so we don't repeat the error */ VbNvSet(vnc, VBNV_TEST_ERROR_FUNC, 0); VbNvSet(vnc, VBNV_TEST_ERROR_NUM, 0); /* Handle error codes */ switch (test_err) { case LOAD_KERNEL_RECOVERY: recovery = VBNV_RECOVERY_RW_TEST_LK; goto LoadKernelExit; case LOAD_KERNEL_NOT_FOUND: case LOAD_KERNEL_INVALID: case LOAD_KERNEL_REBOOT: retval = test_err; goto LoadKernelExit; default: break; } } /* Initialization */ blba = params->bytes_per_lba; kbuf_sectors = KBUF_SIZE / blba; if (0 == kbuf_sectors) { VBDEBUG(("LoadKernel() called with sector size > KBUF_SIZE\n")); goto LoadKernelExit; } rec_switch = (BOOT_FLAG_RECOVERY & params->boot_flags ? 1 : 0); dev_switch = (BOOT_FLAG_DEVELOPER & params->boot_flags ? 1 : 0); if (rec_switch) boot_mode = kBootRecovery; else if (BOOT_FLAG_DEV_FIRMWARE & params->boot_flags) { if (!dev_switch) { /* Dev firmware should be signed such that it never boots with the dev * switch is off; so something is terribly wrong. */ VBDEBUG(("LoadKernel() called with dev firmware but dev switch off\n")); recovery = VBNV_RECOVERY_RW_DEV_MISMATCH; goto LoadKernelExit; } boot_mode = kBootDev; } else { /* Normal firmware */ boot_mode = kBootNormal; dev_switch = 0; /* Always do a fully verified boot */ } /* Clear output params in case we fail */ params->partition_number = 0; params->bootloader_address = 0; params->bootloader_size = 0; if (kBootRecovery == boot_mode) { /* Initialize the shared data structure, since LoadFirmware() didn't do it * for us. */ if (0 != VbSharedDataInit(shared, params->shared_data_size)) { /* Error initializing the shared data, but we can keep going. We just * can't use the shared data. */ VBDEBUG(("Shared data init error\n")); params->shared_data_size = 0; shared = NULL; } /* Use the recovery key to verify the kernel */ kernel_subkey = (VbPublicKey*)((uint8_t*)gbb + gbb->recovery_key_offset); /* Let the TPM know if we're in recovery mode */ if (0 != RollbackKernelRecovery(dev_switch)) { VBDEBUG(("Error setting up TPM for recovery kernel\n")); /* Ignore return code, since we need to boot recovery mode to * fix the TPM. */ } } else { /* Use the kernel subkey passed from LoadFirmware(). */ kernel_subkey = &shared->kernel_subkey; /* Read current kernel key index from TPM. Assumes TPM is already * initialized. */ status = RollbackKernelRead(&tpm_version); if (0 != status) { VBDEBUG(("Unable to get kernel versions from TPM\n")); if (status == TPM_E_MUST_REBOOT) retval = LOAD_KERNEL_REBOOT; else recovery = VBNV_RECOVERY_RW_TPM_ERROR; goto LoadKernelExit; } } 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 = NULL; uint64_t key_version; uint64_t combined_version; uint64_t body_offset; uint64_t body_offset_sectors; uint64_t body_sectors; int key_block_valid = 1; 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) { VBDEBUG(("Partition too small to hold kernel.\n")); goto bad_kernel; } if (0 != BootDeviceReadLBA(part_start, kbuf_sectors, kbuf)) { VBDEBUG(("Unable to read start of partition.\n")); goto bad_kernel; } /* Verify the key block. */ key_block = (VbKeyBlockHeader*)kbuf; if (0 != KeyBlockVerify(key_block, KBUF_SIZE, kernel_subkey, 0)) { VBDEBUG(("Verifying key block signature failed.\n")); key_block_valid = 0; /* If we're not in developer mode, this kernel is bad. */ if (kBootDev != boot_mode) goto bad_kernel; /* In developer mode, we can continue if the SHA-512 hash of the key * block is valid. */ if (0 != KeyBlockVerify(key_block, KBUF_SIZE, kernel_subkey, 1)) { VBDEBUG(("Verifying key block hash failed.\n")); goto bad_kernel; } } /* Check the key block flags against the current boot mode. */ if (!(key_block->key_block_flags & (dev_switch ? KEY_BLOCK_FLAG_DEVELOPER_1 : KEY_BLOCK_FLAG_DEVELOPER_0))) { VBDEBUG(("Key block developer flag mismatch.\n")); key_block_valid = 0; } if (!(key_block->key_block_flags & (rec_switch ? KEY_BLOCK_FLAG_RECOVERY_1 : KEY_BLOCK_FLAG_RECOVERY_0))) { VBDEBUG(("Key block recovery flag mismatch.\n")); key_block_valid = 0; } /* Check for rollback of key version except in recovery mode. */ key_version = key_block->data_key.key_version; if (kBootRecovery != boot_mode) { if (key_version < (tpm_version >> 16)) { VBDEBUG(("Key version too old.\n")); key_block_valid = 0; } } /* If we're not in developer mode, require the key block to be valid. */ if (kBootDev != boot_mode && !key_block_valid) { VBDEBUG(("Key block is invalid.\n")); goto bad_kernel; } /* Get the key for preamble/data verification from the key block. */ data_key = PublicKeyToRSA(&key_block->data_key); if (!data_key) { VBDEBUG(("Data key bad.\n")); goto bad_kernel; } /* Verify the preamble, which follows the key block */ preamble = (VbKernelPreambleHeader*)(kbuf + key_block->key_block_size); if ((0 != VerifyKernelPreamble(preamble, KBUF_SIZE - key_block->key_block_size, data_key))) { VBDEBUG(("Preamble verification failed.\n")); goto bad_kernel; } /* If the key block is valid and we're not in recovery mode, check for * rollback of the kernel version. */ combined_version = ((key_version << 16) | (preamble->kernel_version & 0xFFFF)); if (key_block_valid && kBootRecovery != boot_mode) { if (combined_version < tpm_version) { VBDEBUG(("Kernel version too low.\n")); /* If we're not in developer mode, kernel version must be valid. */ if (kBootDev != boot_mode) goto bad_kernel; } } VBDEBUG(("Kernel preamble is good.\n")); /* Check for lowest version from a valid header. */ if (key_block_valid && lowest_version > combined_version) lowest_version = combined_version; else { VBDEBUG(("Key block valid: %d\n", key_block_valid)); VBDEBUG(("Combined version: %" PRIu64 "\n", combined_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. So skip to the next kernel preamble. */ 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")); goto bad_kernel; } /* 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")); goto bad_kernel; } body_offset_sectors = body_offset / blba; /* Verify kernel body fits in the buffer */ body_sectors = (preamble->body_signature.data_size + blba - 1) / blba; if (body_sectors * blba > params->kernel_buffer_size) { VBDEBUG(("Kernel body doesn't fit in memory.\n")); goto bad_kernel; } /* Verify kernel body fits in the partition */ if (body_offset_sectors + body_sectors > part_size) { VBDEBUG(("Kernel body doesn't fit in partition.\n")); goto bad_kernel; } /* Read the kernel data */ VBPERFSTART("VB_RKD"); if (0 != BootDeviceReadLBA(part_start + body_offset_sectors, body_sectors, params->kernel_buffer)) { VBDEBUG(("Unable to read kernel data.\n")); VBPERFEND("VB_RKD"); goto bad_kernel; } VBPERFEND("VB_RKD"); /* Verify kernel data */ if (0 != VerifyData((const uint8_t*)params->kernel_buffer, params->kernel_buffer_size, &preamble->body_signature, data_key)) { VBDEBUG(("Kernel data verification failed.\n")); goto bad_kernel; } /* Done with the kernel signing key, so can free it now */ RSAPublicKeyFree(data_key); data_key = NULL; /* If we're still here, the kernel is valid. */ /* Save the first good partition we find; that's the one we'll boot */ VBDEBUG(("Partition is good.\n")); good_partition_key_block_valid = key_block_valid; /* 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; GetCurrentKernelUniqueGuid(&gpt, ¶ms->partition_guid); /* TODO: GetCurrentKernelUniqueGuid() should take a destination size, or * the dest should be a struct, so we know it's big enough. */ params->bootloader_address = preamble->bootloader_address; params->bootloader_size = preamble->bootloader_size; /* Update GPT to note this is the kernel we're trying */ GptUpdateKernelEntry(&gpt, GPT_UPDATE_ENTRY_TRY); /* If we're in recovery mode or we're about to boot a dev-signed kernel, * there's no rollback protection, so we can stop at the first valid * kernel. */ if (kBootRecovery == boot_mode || !key_block_valid) { VBDEBUG(("In recovery mode or dev-signed kernel\n")); break; } /* Otherwise, 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 (combined_version == tpm_version) { VBDEBUG(("Same kernel version\n")); break; } /* Continue, so that we skip the error handling code below */ continue; bad_kernel: /* Handle errors parsing this kernel */ if (NULL != data_key) RSAPublicKeyFree(data_key); VBDEBUG(("Marking kernel as invalid.\n")); GptUpdateKernelEntry(&gpt, GPT_UPDATE_ENTRY_BAD); } /* 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 (kBootRecovery != boot_mode && good_partition_key_block_valid) { /* We only update the TPM in normal and developer boot modes. In * developer mode, we only advanced lowest_version for kernels with valid * key blocks, and didn't count self-signed key blocks. 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 = not recovery\n")); if ((lowest_version > tpm_version) && (lowest_version != LOWEST_TPM_VERSION)) { status = RollbackKernelWrite((uint32_t)lowest_version); if (0 != status) { VBDEBUG(("Error writing kernel versions to TPM.\n")); if (status == TPM_E_MUST_REBOOT) retval = LOAD_KERNEL_REBOOT; else recovery = VBNV_RECOVERY_RW_TPM_ERROR; goto LoadKernelExit; } } } /* Lock the kernel versions */ status = RollbackKernelLock(); if (0 != status) { VBDEBUG(("Error locking kernel versions.\n")); /* Don't reboot to recovery mode if we're already there */ if (kBootRecovery != boot_mode) { if (status == TPM_E_MUST_REBOOT) retval = LOAD_KERNEL_REBOOT; else recovery = VBNV_RECOVERY_RW_TPM_ERROR; goto LoadKernelExit; } } /* Success! */ retval = LOAD_KERNEL_SUCCESS; } else { /* TODO: differentiate between finding an invalid kernel * (found_partitions>0) and not finding one at all. Right now we * treat them the same, and return LOAD_KERNEL_INVALID for both. */ retval = LOAD_KERNEL_INVALID; } LoadKernelExit: /* Save whether the good partition's key block was fully verified */ VbNvSet(vnc, VBNV_FW_VERIFIED_KERNEL_KEY, good_partition_key_block_valid); /* Store recovery request, if any, then tear down non-volatile storage */ VbNvSet(vnc, VBNV_RECOVERY_REQUEST, LOAD_KERNEL_RECOVERY == retval ? recovery : VBNV_RECOVERY_NOT_REQUESTED); VbNvTeardown(vnc); /* Store how much shared data we used, if any */ if (shared) params->shared_data_size = shared->data_used; return retval; }