diff options
Diffstat (limited to 'drivers/firmware/efi/libstub/tpm.c')
| -rw-r--r-- | drivers/firmware/efi/libstub/tpm.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c new file mode 100644 index 0000000000..7acbac16ea --- /dev/null +++ b/drivers/firmware/efi/libstub/tpm.c @@ -0,0 +1,167 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * TPM handling. + * + * Copyright (C) 2016 CoreOS, Inc + * Copyright (C) 2017 Google, Inc. + * Matthew Garrett <mjg59@google.com> + * Thiebaud Weksteen <tweek@google.com> + */ +#include <linux/efi.h> +#include <linux/tpm_eventlog.h> +#include <asm/efi.h> + +#include "efistub.h" + +#ifdef CONFIG_RESET_ATTACK_MITIGATION +static const efi_char16_t efi_MemoryOverWriteRequest_name[] = + L"MemoryOverwriteRequestControl"; + +#define MEMORY_ONLY_RESET_CONTROL_GUID \ + EFI_GUID(0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29) + +/* + * Enable reboot attack mitigation. This requests that the firmware clear the + * RAM on next reboot before proceeding with boot, ensuring that any secrets + * are cleared. If userland has ensured that all secrets have been removed + * from RAM before reboot it can simply reset this variable. + */ +void efi_enable_reset_attack_mitigation(void) +{ + u8 val = 1; + efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID; + efi_status_t status; + unsigned long datasize = 0; + + status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid, + NULL, &datasize, NULL); + + if (status == EFI_NOT_FOUND) + return; + + set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid, + EFI_VARIABLE_NON_VOLATILE | + EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val); +} + +#endif + +void efi_retrieve_tpm2_eventlog(void) +{ + efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID; + efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID; + efi_status_t status; + efi_physical_addr_t log_location = 0, log_last_entry = 0; + struct linux_efi_tpm_eventlog *log_tbl = NULL; + struct efi_tcg2_final_events_table *final_events_table = NULL; + unsigned long first_entry_addr, last_entry_addr; + size_t log_size, last_entry_size; + efi_bool_t truncated; + int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2; + efi_tcg2_protocol_t *tcg2_protocol = NULL; + int final_events_size = 0; + + status = efi_bs_call(locate_protocol, &tcg2_guid, NULL, + (void **)&tcg2_protocol); + if (status != EFI_SUCCESS) + return; + + status = efi_call_proto(tcg2_protocol, get_event_log, version, + &log_location, &log_last_entry, &truncated); + + if (status != EFI_SUCCESS || !log_location) { + version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2; + status = efi_call_proto(tcg2_protocol, get_event_log, version, + &log_location, &log_last_entry, + &truncated); + if (status != EFI_SUCCESS || !log_location) + return; + + } + + first_entry_addr = (unsigned long) log_location; + + /* + * We populate the EFI table even if the logs are empty. + */ + if (!log_last_entry) { + log_size = 0; + } else { + last_entry_addr = (unsigned long) log_last_entry; + /* + * get_event_log only returns the address of the last entry. + * We need to calculate its size to deduce the full size of + * the logs. + */ + if (version == EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) { + /* + * The TCG2 log format has variable length entries, + * and the information to decode the hash algorithms + * back into a size is contained in the first entry - + * pass a pointer to the final entry (to calculate its + * size) and the first entry (so we know how long each + * digest is) + */ + last_entry_size = + __calc_tpm2_event_size((void *)last_entry_addr, + (void *)(long)log_location, + false); + } else { + last_entry_size = sizeof(struct tcpa_event) + + ((struct tcpa_event *) last_entry_addr)->event_size; + } + log_size = log_last_entry - log_location + last_entry_size; + } + + /* Allocate space for the logs and copy them. */ + status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, + sizeof(*log_tbl) + log_size, (void **)&log_tbl); + + if (status != EFI_SUCCESS) { + efi_err("Unable to allocate memory for event log\n"); + return; + } + + /* + * Figure out whether any events have already been logged to the + * final events structure, and if so how much space they take up + */ + if (version == EFI_TCG2_EVENT_LOG_FORMAT_TCG_2) + final_events_table = get_efi_config_table(LINUX_EFI_TPM_FINAL_LOG_GUID); + if (final_events_table && final_events_table->nr_events) { + struct tcg_pcr_event2_head *header; + int offset; + void *data; + int event_size; + int i = final_events_table->nr_events; + + data = (void *)final_events_table; + offset = sizeof(final_events_table->version) + + sizeof(final_events_table->nr_events); + + while (i > 0) { + header = data + offset + final_events_size; + event_size = __calc_tpm2_event_size(header, + (void *)(long)log_location, + false); + final_events_size += event_size; + i--; + } + } + + memset(log_tbl, 0, sizeof(*log_tbl) + log_size); + log_tbl->size = log_size; + log_tbl->final_events_preboot_size = final_events_size; + log_tbl->version = version; + memcpy(log_tbl->log, (void *) first_entry_addr, log_size); + + status = efi_bs_call(install_configuration_table, + &linux_eventlog_guid, log_tbl); + if (status != EFI_SUCCESS) + goto err_free; + return; + +err_free: + efi_bs_call(free_pool, log_tbl); +} |