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path: root/drivers/firmware/efi/libstub/tpm.c
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Diffstat (limited to 'drivers/firmware/efi/libstub/tpm.c')
-rw-r--r--drivers/firmware/efi/libstub/tpm.c167
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 000000000..7acbac16e
--- /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);
+}