diff options
Diffstat (limited to 'drivers/firmware/efi/libstub/tpm.c')
| -rw-r--r-- | drivers/firmware/efi/libstub/tpm.c | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c new file mode 100644 index 000000000..a90b0b8fc --- /dev/null +++ b/drivers/firmware/efi/libstub/tpm.c @@ -0,0 +1,136 @@ +/* + * TPM handling. + * + * Copyright (C) 2016 CoreOS, Inc + * Copyright (C) 2017 Google, Inc. + * Matthew Garrett <mjg59@google.com> + * Thiebaud Weksteen <tweek@google.com> + * + * This file is part of the Linux kernel, and is made available under the + * terms of the GNU General Public License version 2. + */ +#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) + +#define get_efi_var(name, vendor, ...) \ + efi_call_runtime(get_variable, \ + (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ + __VA_ARGS__) + +#define set_efi_var(name, vendor, ...) \ + efi_call_runtime(set_variable, \ + (efi_char16_t *)(name), (efi_guid_t *)(vendor), \ + __VA_ARGS__) + +/* + * 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(efi_system_table_t *sys_table_arg) +{ + 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 + +static void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg) +{ + 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; + unsigned long first_entry_addr, last_entry_addr; + size_t log_size, last_entry_size; + efi_bool_t truncated; + void *tcg2_protocol = NULL; + + status = efi_call_early(locate_protocol, &tcg2_guid, NULL, + &tcg2_protocol); + if (status != EFI_SUCCESS) + return; + + status = efi_call_proto(efi_tcg2_protocol, get_event_log, tcg2_protocol, + EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2, + &log_location, &log_last_entry, &truncated); + if (status != EFI_SUCCESS) + return; + + if (!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. + */ + 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_call_early(allocate_pool, EFI_LOADER_DATA, + sizeof(*log_tbl) + log_size, + (void **) &log_tbl); + + if (status != EFI_SUCCESS) { + efi_printk(sys_table_arg, + "Unable to allocate memory for event log\n"); + return; + } + + memset(log_tbl, 0, sizeof(*log_tbl) + log_size); + log_tbl->size = log_size; + log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2; + memcpy(log_tbl->log, (void *) first_entry_addr, log_size); + + status = efi_call_early(install_configuration_table, + &linux_eventlog_guid, log_tbl); + if (status != EFI_SUCCESS) + goto err_free; + return; + +err_free: + efi_call_early(free_pool, log_tbl); +} + +void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg) +{ + /* Only try to retrieve the logs in 1.2 format. */ + efi_retrieve_tpm2_eventlog_1_2(sys_table_arg); +} |