[PATCH v4 1/5] efi_loader: add secure boot variable measurement
Masahisa Kojima
masahisa.kojima at linaro.org
Fri Aug 13 09:12:39 CEST 2021
TCG PC Client PFP spec requires to measure the secure
boot policy before validating the UEFI image.
This commit adds the secure boot variable measurement
of "SecureBoot", "PK", "KEK", "db", "dbx", "dbt", and "dbr".
Note that this implementation assumes that secure boot
variables are pre-configured and not be set/updated in runtime.
Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
---
Changes in v4:
- remove unnecessary EFIAPI specifier
- modify wrong guid for dbt and dbr
Changes in v3:
- add "dbt" and "dbr" measurement
- accept empty variable measurement for "SecureBoot", "PK",
"KEK", "db" and "dbx" as TCG2 spec requires
- fix comment format
Changes in v2:
- missing null check for getting variable data
- some minor fix for readability
include/efi_tcg2.h | 20 +++++
lib/efi_loader/efi_tcg2.c | 165 ++++++++++++++++++++++++++++++++++++++
2 files changed, 185 insertions(+)
diff --git a/include/efi_tcg2.h b/include/efi_tcg2.h
index bcfb98168a..497ba3ce94 100644
--- a/include/efi_tcg2.h
+++ b/include/efi_tcg2.h
@@ -142,6 +142,26 @@ struct efi_tcg2_final_events_table {
struct tcg_pcr_event2 event[];
};
+/**
+ * struct tdUEFI_VARIABLE_DATA - event log structure of UEFI variable
+ * @variable_name: The vendorGUID parameter in the
+ * GetVariable() API.
+ * @unicode_name_length: The length in CHAR16 of the Unicode name of
+ * the variable.
+ * @variable_data_length: The size of the variable data.
+ * @unicode_name: The CHAR16 unicode name of the variable
+ * without NULL-terminator.
+ * @variable_data: The data parameter of the efi variable
+ * in the GetVariable() API.
+ */
+struct efi_tcg2_uefi_variable_data {
+ efi_guid_t variable_name;
+ u64 unicode_name_length;
+ u64 variable_data_length;
+ u16 unicode_name[1];
+ u8 variable_data[1];
+};
+
struct efi_tcg2_protocol {
efi_status_t (EFIAPI * get_capability)(struct efi_tcg2_protocol *this,
struct efi_tcg2_boot_service_capability *capability);
diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index 1319a8b378..db3d6d7586 100644
--- a/lib/efi_loader/efi_tcg2.c
+++ b/lib/efi_loader/efi_tcg2.c
@@ -78,6 +78,19 @@ static const struct digest_info hash_algo_list[] = {
},
};
+struct variable_info {
+ u16 *name;
+ const efi_guid_t *guid;
+};
+
+static struct variable_info secure_variables[] = {
+ {L"SecureBoot", &efi_global_variable_guid},
+ {L"PK", &efi_global_variable_guid},
+ {L"KEK", &efi_global_variable_guid},
+ {L"db", &efi_guid_image_security_database},
+ {L"dbx", &efi_guid_image_security_database},
+};
+
#define MAX_HASH_COUNT ARRAY_SIZE(hash_algo_list)
/**
@@ -1264,6 +1277,39 @@ free_pool:
return ret;
}
+/**
+ * tcg2_measure_event() - common function to add event log and extend PCR
+ *
+ * @dev: TPM device
+ * @pcr_index: PCR index
+ * @event_type: type of event added
+ * @size: event size
+ * @event: event data
+ *
+ * Return: status code
+ */
+static efi_status_t
+tcg2_measure_event(struct udevice *dev, u32 pcr_index, u32 event_type,
+ u32 size, u8 event[])
+{
+ struct tpml_digest_values digest_list;
+ efi_status_t ret;
+
+ ret = tcg2_create_digest(event, size, &digest_list);
+ if (ret != EFI_SUCCESS)
+ goto out;
+
+ ret = tcg2_pcr_extend(dev, pcr_index, &digest_list);
+ if (ret != EFI_SUCCESS)
+ goto out;
+
+ ret = tcg2_agile_log_append(pcr_index, event_type, &digest_list,
+ size, event);
+
+out:
+ return ret;
+}
+
/**
* efi_append_scrtm_version - Append an S-CRTM EV_S_CRTM_VERSION event on the
* eventlog and extend the PCRs
@@ -1294,6 +1340,118 @@ out:
return ret;
}
+/**
+ * tcg2_measure_variable() - add variable event log and extend PCR
+ *
+ * @dev: TPM device
+ * @pcr_index: PCR index
+ * @event_type: type of event added
+ * @var_name: variable name
+ * @guid: guid
+ * @data_size: variable data size
+ * @data: variable data
+ *
+ * Return: status code
+ */
+static efi_status_t tcg2_measure_variable(struct udevice *dev, u32 pcr_index,
+ u32 event_type, u16 *var_name,
+ const efi_guid_t *guid,
+ efi_uintn_t data_size, u8 *data)
+{
+ u32 event_size;
+ efi_status_t ret;
+ struct efi_tcg2_uefi_variable_data *event;
+
+ event_size = sizeof(event->variable_name) +
+ sizeof(event->unicode_name_length) +
+ sizeof(event->variable_data_length) +
+ (u16_strlen(var_name) * sizeof(u16)) + data_size;
+ event = malloc(event_size);
+ if (!event)
+ return EFI_OUT_OF_RESOURCES;
+
+ guidcpy(&event->variable_name, guid);
+ event->unicode_name_length = u16_strlen(var_name);
+ event->variable_data_length = data_size;
+ memcpy(event->unicode_name, var_name,
+ (event->unicode_name_length * sizeof(u16)));
+ if (data) {
+ memcpy((u16 *)event->unicode_name + event->unicode_name_length,
+ data, data_size);
+ }
+ ret = tcg2_measure_event(dev, pcr_index, event_type, event_size,
+ (u8 *)event);
+ free(event);
+ return ret;
+}
+
+/**
+ * tcg2_measure_secure_boot_variable() - measure secure boot variables
+ *
+ * @dev: TPM device
+ *
+ * Return: status code
+ */
+static efi_status_t tcg2_measure_secure_boot_variable(struct udevice *dev)
+{
+ u8 *data;
+ efi_uintn_t data_size;
+ u32 count, i;
+ efi_status_t ret;
+
+ count = ARRAY_SIZE(secure_variables);
+ for (i = 0; i < count; i++) {
+ /*
+ * According to the TCG2 PC Client PFP spec, "SecureBoot",
+ * "PK", "KEK", "db" and "dbx" variables must be measured
+ * even if they are empty.
+ */
+ data = efi_get_var(secure_variables[i].name,
+ secure_variables[i].guid,
+ &data_size);
+
+ ret = tcg2_measure_variable(dev, 7,
+ EV_EFI_VARIABLE_DRIVER_CONFIG,
+ secure_variables[i].name,
+ secure_variables[i].guid,
+ data_size, data);
+ free(data);
+ if (ret != EFI_SUCCESS)
+ goto error;
+ }
+
+ /*
+ * TCG2 PC Client PFP spec says "dbt" and "dbr" are
+ * measured if present and not empty.
+ */
+ data = efi_get_var(L"dbt",
+ &efi_guid_image_security_database,
+ &data_size);
+ if (data) {
+ ret = tcg2_measure_variable(dev, 7,
+ EV_EFI_VARIABLE_DRIVER_CONFIG,
+ L"dbt",
+ &efi_guid_image_security_database,
+ data_size, data);
+ free(data);
+ }
+
+ data = efi_get_var(L"dbr",
+ &efi_guid_image_security_database,
+ &data_size);
+ if (data) {
+ ret = tcg2_measure_variable(dev, 7,
+ EV_EFI_VARIABLE_DRIVER_CONFIG,
+ L"dbr",
+ &efi_guid_image_security_database,
+ data_size, data);
+ free(data);
+ }
+
+error:
+ return ret;
+}
+
/**
* efi_tcg2_register() - register EFI_TCG2_PROTOCOL
*
@@ -1328,6 +1486,13 @@ efi_status_t efi_tcg2_register(void)
tcg2_uninit();
goto fail;
}
+
+ ret = tcg2_measure_secure_boot_variable(dev);
+ if (ret != EFI_SUCCESS) {
+ tcg2_uninit();
+ goto fail;
+ }
+
return ret;
fail:
--
2.17.1
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