1 files changed, 196 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/tpm.c b/drivers/firmware/efi/libstub/tpm.c
new file mode 100644
index 000000000000..a5c6c4f163fc
--- /dev/null
+++ b/drivers/firmware/efi/libstub/tpm.c
@@ -0,0 +1,196 @@
+// 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
+
+static void efi_retrieve_tcg2_eventlog(int version, efi_physical_addr_t log_location,
+				       efi_physical_addr_t log_last_entry,
+				       efi_bool_t truncated,
+				       struct efi_tcg2_final_events_table *final_events_table)
+{
+	efi_guid_t linux_eventlog_guid = LINUX_EFI_TPM_EVENT_LOG_GUID;
+	efi_status_t status;
+	struct linux_efi_tpm_eventlog *log_tbl = NULL;
+	unsigned long first_entry_addr, last_entry_addr;
+	size_t log_size, last_entry_size;
+	u32 final_events_size = 0;
+
+	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.
+		 *
+		 * CC Event log also uses TCG2 format, handle it same as TPM2.
+		 */
+		if (version > EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_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_ACPI_RECLAIM_MEMORY,
+			     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 (final_events_table && final_events_table->nr_events) {
+		struct tcg_pcr_event2_head *header;
+		u32 offset;
+		void *data;
+		u32 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);
+			/* If calc fails this is a malformed log */
+			if (!event_size)
+				break;
+			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);
+}
+
+void efi_retrieve_eventlog(void)
+{
+	struct efi_tcg2_final_events_table *final_events_table = NULL;
+	efi_physical_addr_t log_location = 0, log_last_entry = 0;
+	efi_guid_t tpm2_guid = EFI_TCG2_PROTOCOL_GUID;
+	int version = EFI_TCG2_EVENT_LOG_FORMAT_TCG_2;
+	efi_tcg2_protocol_t *tpm2 = NULL;
+	efi_bool_t truncated;
+	efi_status_t status;
+
+	status = efi_bs_call(locate_protocol, &tpm2_guid, NULL, (void **)&tpm2);
+	if (status == EFI_SUCCESS) {
+		status = efi_call_proto(tpm2, 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(tpm2, get_event_log, version,
+						&log_location, &log_last_entry,
+						&truncated);
+		} else {
+			final_events_table =
+				get_efi_config_table(EFI_TCG2_FINAL_EVENTS_TABLE_GUID);
+		}
+	} else {
+		efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID;
+		efi_cc_protocol_t *cc = NULL;
+
+		status = efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc);
+		if (status != EFI_SUCCESS)
+			return;
+
+		version = EFI_CC_EVENT_LOG_FORMAT_TCG_2;
+		status = efi_call_proto(cc, get_event_log, version, &log_location,
+					&log_last_entry, &truncated);
+
+		final_events_table =
+			get_efi_config_table(EFI_CC_FINAL_EVENTS_TABLE_GUID);
+	}
+
+	if (status != EFI_SUCCESS || !log_location)
+		return;
+
+	efi_retrieve_tcg2_eventlog(version, log_location, log_last_entry,
+				   truncated, final_events_table);
+}