137 lines
3.9 KiB
C
137 lines
3.9 KiB
C
/*
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* TPM handling.
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*
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* Copyright (C) 2016 CoreOS, Inc
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* Copyright (C) 2017 Google, Inc.
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* Matthew Garrett <mjg59@google.com>
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* Thiebaud Weksteen <tweek@google.com>
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*
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* This file is part of the Linux kernel, and is made available under the
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* terms of the GNU General Public License version 2.
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*/
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#include <linux/efi.h>
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#include <linux/tpm_eventlog.h>
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#include <asm/efi.h>
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#include "efistub.h"
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#ifdef CONFIG_RESET_ATTACK_MITIGATION
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static const efi_char16_t efi_MemoryOverWriteRequest_name[] =
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L"MemoryOverwriteRequestControl";
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#define MEMORY_ONLY_RESET_CONTROL_GUID \
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EFI_GUID(0xe20939be, 0x32d4, 0x41be, 0xa1, 0x50, 0x89, 0x7f, 0x85, 0xd4, 0x98, 0x29)
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#define get_efi_var(name, vendor, ...) \
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efi_call_runtime(get_variable, \
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(efi_char16_t *)(name), (efi_guid_t *)(vendor), \
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__VA_ARGS__)
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#define set_efi_var(name, vendor, ...) \
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efi_call_runtime(set_variable, \
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(efi_char16_t *)(name), (efi_guid_t *)(vendor), \
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__VA_ARGS__)
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/*
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* Enable reboot attack mitigation. This requests that the firmware clear the
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* RAM on next reboot before proceeding with boot, ensuring that any secrets
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* are cleared. If userland has ensured that all secrets have been removed
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* from RAM before reboot it can simply reset this variable.
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*/
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void efi_enable_reset_attack_mitigation(efi_system_table_t *sys_table_arg)
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{
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u8 val = 1;
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efi_guid_t var_guid = MEMORY_ONLY_RESET_CONTROL_GUID;
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efi_status_t status;
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unsigned long datasize = 0;
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status = get_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
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NULL, &datasize, NULL);
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if (status == EFI_NOT_FOUND)
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return;
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set_efi_var(efi_MemoryOverWriteRequest_name, &var_guid,
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EFI_VARIABLE_NON_VOLATILE |
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EFI_VARIABLE_BOOTSERVICE_ACCESS |
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EFI_VARIABLE_RUNTIME_ACCESS, sizeof(val), &val);
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}
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#endif
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static void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
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{
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efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
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efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
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efi_status_t status;
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efi_physical_addr_t log_location = 0, log_last_entry = 0;
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struct linux_efi_tpm_eventlog *log_tbl = NULL;
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unsigned long first_entry_addr, last_entry_addr;
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size_t log_size, last_entry_size;
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efi_bool_t truncated;
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void *tcg2_protocol = NULL;
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status = efi_call_early(locate_protocol, &tcg2_guid, NULL,
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&tcg2_protocol);
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if (status != EFI_SUCCESS)
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return;
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status = efi_call_proto(efi_tcg2_protocol, get_event_log, tcg2_protocol,
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EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2,
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&log_location, &log_last_entry, &truncated);
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if (status != EFI_SUCCESS)
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return;
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if (!log_location)
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return;
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first_entry_addr = (unsigned long) log_location;
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/*
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* We populate the EFI table even if the logs are empty.
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*/
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if (!log_last_entry) {
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log_size = 0;
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} else {
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last_entry_addr = (unsigned long) log_last_entry;
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/*
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* get_event_log only returns the address of the last entry.
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* We need to calculate its size to deduce the full size of
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* the logs.
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*/
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last_entry_size = sizeof(struct tcpa_event) +
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((struct tcpa_event *) last_entry_addr)->event_size;
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log_size = log_last_entry - log_location + last_entry_size;
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}
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/* Allocate space for the logs and copy them. */
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status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
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sizeof(*log_tbl) + log_size,
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(void **) &log_tbl);
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if (status != EFI_SUCCESS) {
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efi_printk(sys_table_arg,
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"Unable to allocate memory for event log\n");
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return;
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}
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memset(log_tbl, 0, sizeof(*log_tbl) + log_size);
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log_tbl->size = log_size;
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log_tbl->version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2;
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memcpy(log_tbl->log, (void *) first_entry_addr, log_size);
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status = efi_call_early(install_configuration_table,
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&linux_eventlog_guid, log_tbl);
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if (status != EFI_SUCCESS)
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goto err_free;
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return;
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err_free:
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efi_call_early(free_pool, log_tbl);
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}
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void efi_retrieve_tpm2_eventlog(efi_system_table_t *sys_table_arg)
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{
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/* Only try to retrieve the logs in 1.2 format. */
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efi_retrieve_tpm2_eventlog_1_2(sys_table_arg);
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}
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