Re: [PATCH v12 07/13] HP BIOSCFG driver - string-attributes

[Ilpo Järvinen]

On Fri, 5 May 2023, Jorge Lopez wrote:

> HP BIOS Configuration driver purpose is to provide a driver supporting
> the latest sysfs class firmware attributes framework allowing the user
> to change BIOS settings and security solutions on HP Inc.’s commercial
> notebooks.
> 
> Many features of HP Commercial notebooks can be managed using Windows
> Management Instrumentation (WMI). WMI is an implementation of Web-Based
> Enterprise Management (WBEM) that provides a standards-based interface
> for changing and monitoring system settings. HP BIOSCFG driver provides
> a native Linux solution and the exposed features facilitates the
> migration to Linux environments.
> 
> The Linux security features to be provided in hp-bioscfg driver enables
> managing the BIOS settings and security solutions via sysfs, a virtual
> filesystem that can be used by user-mode applications. The new
> documentation cover HP-specific firmware sysfs attributes such Secure
> Platform Management and Sure Start. Each section provides security
> feature description and identifies sysfs directories and files exposed
> by the driver.
> 
> Many HP Commercial notebooks include a feature called Secure Platform
> Management (SPM), which replaces older password-based BIOS settings
> management with public key cryptography. PC secure product management
> begins when a target system is provisioned with cryptographic keys
> that are used to ensure the integrity of communications between system
> management utilities and the BIOS.
> 
> HP Commercial notebooks have several BIOS settings that control its
> behaviour and capabilities, many of which are related to security.
> To prevent unauthorized changes to these settings, the system can
> be configured to use a cryptographic signature-based authorization
> string that the BIOS will use to verify authorization to modify the
> setting.
> 
> Linux Security components are under development and not published yet.
> The only linux component is the driver (hp bioscfg) at this time.
> Other published security components are under Windows.
> 
> Signed-off-by: Jorge Lopez <jorge.lopez2@xxxxxx>
> 
> ---
> Based on the latest platform-drivers-x86.git/for-next
> ---
>  .../x86/hp/hp-bioscfg/string-attributes.c     | 415 ++++++++++++++++++
>  1 file changed, 415 insertions(+)
>  create mode 100644 drivers/platform/x86/hp/hp-bioscfg/string-attributes.c
> 
> diff --git a/drivers/platform/x86/hp/hp-bioscfg/string-attributes.c b/drivers/platform/x86/hp/hp-bioscfg/string-attributes.c
> new file mode 100644
> index 000000000000..d74ecc973703
> --- /dev/null
> +++ b/drivers/platform/x86/hp/hp-bioscfg/string-attributes.c
> @@ -0,0 +1,415 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Functions corresponding to string type attributes under
> + * HP_WMI_BIOS_STRING_GUID for use with hp-bioscfg driver.
> + *
> + * Copyright (c) 2022 HP Development Company, L.P.
> + */
> +
> +#include "bioscfg.h"
> +
> +#define WMI_STRING_TYPE "HPBIOS_BIOSString"
> +
> +GET_INSTANCE_ID(string);
> +
> +static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> +{
> +	int instance_id = get_string_instance_id(kobj);
> +
> +	if (instance_id < 0)
> +		return -EIO;
> +
> +	return  sysfs_emit(buf, "%s\n",
> +			 bioscfg_drv.string_data[instance_id].current_value);
> +}
> +
> +/*
> + * validate_string_input() -
> + * Validate input of current_value against min and max lengths
> + *
> + * @instance_id: The instance on which input is validated
> + * @buf: Input value
> + */
> +static int validate_string_input(int instance_id, const char *buf)
> +{
> +	int in_len = strlen(buf);
> +	struct string_data *string_data = &bioscfg_drv.string_data[instance_id];
> +
> +	/* BIOS treats it as a read only attribute */
> +	if (string_data->common.is_readonly)
> +		return -EIO;
> +
> +	if (in_len < string_data->min_length ||
> +	    in_len > string_data->max_length)
> +		return -ERANGE;
> +
> +	/*
> +	 * set pending reboot flag depending on
> +	 * "RequiresPhysicalPresence" value
> +	 */
> +	if (string_data->common.requires_physical_presence)
> +		set_reboot_and_signal_event();
> +	return 0;
> +}
> +
> +static void update_string_value(int instance_id, char *attr_value)
> +{
> +	struct string_data *string_data = &bioscfg_drv.string_data[instance_id];
> +
> +	/* Write settings to BIOS */
> +	strscpy(string_data->current_value,
> +		attr_value,
> +		sizeof(string_data->current_value));

Use less lines.

> +}
> +
> +ATTRIBUTE_S_COMMON_PROPERTY_SHOW(display_name_language_code, string);
> +static struct kobj_attribute string_display_langcode =
> +	__ATTR_RO(display_name_language_code);
> +
> +ATTRIBUTE_S_COMMON_PROPERTY_SHOW(display_name, string);
> +static struct kobj_attribute string_display_name =
> +	__ATTR_RO(display_name);
> +
> +ATTRIBUTE_PROPERTY_STORE(current_value, string);
> +static struct kobj_attribute string_current_val =
> +	__ATTR_RW_MODE(current_value, 0644);
> +
> +ATTRIBUTE_N_PROPERTY_SHOW(min_length, string);
> +static struct kobj_attribute string_min_length =
> +	__ATTR_RO(min_length);
> +
> +ATTRIBUTE_N_PROPERTY_SHOW(max_length, string);
> +static struct kobj_attribute string_max_length =
> +	__ATTR_RO(max_length);
> +
> +static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
> +			 char *buf)
> +{
> +	return sysfs_emit(buf, "string\n");
> +}
> +
> +static struct kobj_attribute string_type =
> +	__ATTR_RO(type);
> +
> +static struct attribute *string_attrs[] = {
> +	&string_display_langcode.attr,
> +	&string_display_name.attr,
> +	&string_current_val.attr,
> +	&string_min_length.attr,
> +	&string_max_length.attr,
> +	&string_type.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group string_attr_group = {
> +	.attrs = string_attrs,
> +};
> +
> +int alloc_string_data(void)
> +{
> +	bioscfg_drv.string_instances_count = get_instance_count(HP_WMI_BIOS_STRING_GUID);
> +	bioscfg_drv.string_data = kcalloc(bioscfg_drv.string_instances_count,
> +					  sizeof(struct string_data), GFP_KERNEL);

sizeof(*bioscfg_drv.string_data) ?

> +	if (!bioscfg_drv.string_data) {
> +		bioscfg_drv.string_instances_count = 0;
> +		return -ENOMEM;
> +	}
> +	return 0;
> +}
> +
> +/* Expected Values types associated with each element */
> +static const acpi_object_type expected_string_types[] = {
> +	[NAME] = ACPI_TYPE_STRING,
> +	[VALUE] = ACPI_TYPE_STRING,
> +	[PATH] = ACPI_TYPE_STRING,
> +	[IS_READONLY] = ACPI_TYPE_INTEGER,
> +	[DISPLAY_IN_UI] = ACPI_TYPE_INTEGER,
> +	[REQUIRES_PHYSICAL_PRESENCE] = ACPI_TYPE_INTEGER,
> +	[SEQUENCE] = ACPI_TYPE_INTEGER,
> +	[PREREQUISITES_SIZE] = ACPI_TYPE_INTEGER,
> +	[PREREQUISITES] = ACPI_TYPE_STRING,
> +	[SECURITY_LEVEL] = ACPI_TYPE_INTEGER,
> +	[STR_MIN_LENGTH] = ACPI_TYPE_INTEGER,
> +	[STR_MAX_LENGTH] = ACPI_TYPE_INTEGER,
> +};
> +
> +/*
> + * populate_string_package_data() -
> + * Populate all properties of an instance under string attribute
> + *
> + * @string_obj: ACPI object with string data
> + * @instance_id: The instance to enumerate
> + * @attr_name_kobj: The parent kernel object
> + */
> +int populate_string_package_data(union acpi_object *string_obj,
> +				 int instance_id,
> +				 struct kobject *attr_name_kobj)
> +{
> +	struct string_data *string_data = &bioscfg_drv.string_data[instance_id];
> +
> +	string_data->attr_name_kobj = attr_name_kobj;
> +
> +	populate_string_elements_from_package(string_obj,
> +					      string_obj->package.count,
> +					      instance_id);
> +
> +	update_attribute_permissions(string_data->common.is_readonly,
> +				     &string_current_val);
> +	friendly_user_name_update(string_data->common.path,
> +				  attr_name_kobj->name,
> +				  string_data->common.display_name,
> +				  sizeof(string_data->common.display_name));
> +	return sysfs_create_group(attr_name_kobj, &string_attr_group);
> +}
> +
> +int populate_string_elements_from_package(union acpi_object *string_obj,
> +					  int string_obj_count,
> +					  int instance_id)
> +{
> +	char *str_value = NULL;
> +	int value_len;
> +	int ret = 0;
> +	u32 int_value;
> +	int elem;
> +	int reqs;
> +	int eloc;
> +	struct string_data *string_data = &bioscfg_drv.string_data[instance_id];
> +
> +	if (!string_obj)
> +		return -EINVAL;
> +
> +	strscpy(string_data->common.display_name_language_code,
> +		LANG_CODE_STR,
> +		sizeof(string_data->common.display_name_language_code));
> +
> +	for (elem = 1, eloc = 1; elem < string_obj_count; elem++, eloc++) {
> +		/* ONLY look at the first STRING_ELEM_CNT elements */
> +		if (eloc == STR_ELEM_CNT)
> +			goto exit_string_package;
> +
> +		switch (string_obj[elem].type) {
> +		case ACPI_TYPE_STRING:
> +
> +			if (elem != PREREQUISITES) {
> +				ret = convert_hexstr_to_str(string_obj[elem].string.pointer,
> +							    string_obj[elem].string.length,
> +							    &str_value, &value_len);
> +
> +				if (ret)
> +					continue;
> +			}
> +			break;
> +		case ACPI_TYPE_INTEGER:
> +			int_value = (u32)string_obj[elem].integer.value;
> +			break;
> +		default:
> +			pr_warn("Unsupported object type [%d]\n", string_obj[elem].type);
> +			continue;
> +		}
> +
> +		/* Check that both expected and read object type match */
> +		if (expected_string_types[eloc] != string_obj[elem].type) {
> +			pr_err("Error expected type %d for elem  %d, but got type %d instead\n",
> +			       expected_string_types[eloc], elem, string_obj[elem].type);
> +			return -EIO;
> +		}
> +
> +		/* Assign appropriate element value to corresponding field*/
> +		switch (eloc) {
> +		case VALUE:
> +			strscpy(string_data->current_value,
> +				str_value, sizeof(string_data->current_value));
> +			break;
> +		case PATH:
> +			strscpy(string_data->common.path, str_value,
> +				sizeof(string_data->common.path));
> +			break;
> +		case IS_READONLY:
> +			string_data->common.is_readonly = int_value;
> +			break;
> +		case DISPLAY_IN_UI:
> +			string_data->common.display_in_ui = int_value;
> +			break;
> +		case REQUIRES_PHYSICAL_PRESENCE:
> +			string_data->common.requires_physical_presence = int_value;
> +			break;
> +		case SEQUENCE:
> +			string_data->common.sequence = int_value;
> +			break;
> +		case PREREQUISITES_SIZE:
> +			if (string_data->common.prerequisites_size > MAX_PREREQUISITES_SIZE)
> +				pr_warn("Prerequisites size value exceeded the maximum number of elements supported or data may be malformed\n");
> +			/*
> +			 * This HACK is needed to keep the expected
> +			 * element list pointing to the right obj[elem].type
> +			 * when the size is zero.  PREREQUISITES
> +			 * object is omitted by BIOS when the size is
> +			 * zero.
> +			 */
> +			if (string_data->common.prerequisites_size == 0)
> +				eloc++;
> +			break;
> +		case PREREQUISITES:
> +			for (reqs = 0;
> +			     reqs < string_data->common.prerequisites_size && reqs < MAX_PREREQUISITES_SIZE;
> +			     reqs++) {
> +				if (elem >= string_obj_count) {
> +					pr_err("Error elem-objects package is too small\n");
> +					return -EINVAL;
> +				}
> +
> +				ret = convert_hexstr_to_str(string_obj[elem + reqs].string.pointer,
> +							    string_obj[elem + reqs].string.length,
> +							    &str_value, &value_len);
> +
> +				if (ret)
> +					continue;
> +
> +				strscpy(string_data->common.prerequisites[reqs],
> +					str_value,
> +					sizeof(string_data->common.prerequisites[reqs]));
> +				kfree(str_value);
> +			}
> +			break;
> +
> +		case SECURITY_LEVEL:
> +			string_data->common.security_level = int_value;
> +			break;
> +		case STR_MIN_LENGTH:
> +			string_data->min_length = int_value;
> +			break;
> +		case STR_MAX_LENGTH:
> +			string_data->max_length = int_value;
> +			break;
> +		default:
> +			pr_warn("Invalid element: %d found in String attribute or data may be malformed\n", elem);
> +			break;
> +		}
> +
> +		kfree(str_value);
> +	}
> +
> +exit_string_package:
> +	kfree(str_value);
> +	return 0;
> +}
> +
> +/*
> + * populate_string_data() -
> + * Populate all properties of an instance under string attribute
> + *
> + * @buffer_ptr: Buffer pointer
> + * @buffer_size: Buffer size
> + * @instance_id: The instance to enumerate
> + * @attr_name_kobj: The parent kernel object
> + */
> +int populate_string_buffer_data(u8 *buffer_ptr, u32 *buffer_size,
> +				int instance_id,
> +				struct kobject *attr_name_kobj)
> +{
> +	struct string_data *string_data = &bioscfg_drv.string_data[instance_id];
> +
> +	string_data->attr_name_kobj = attr_name_kobj;
> +
> +	populate_string_elements_from_buffer(buffer_ptr, buffer_size,
> +					     instance_id);
> +
> +	update_attribute_permissions(string_data->common.is_readonly,
> +				     &string_current_val);
> +	friendly_user_name_update(string_data->common.path,
> +				  attr_name_kobj->name,
> +				  string_data->common.display_name,
> +				  sizeof(string_data->common.display_name));
> +
> +	return sysfs_create_group(attr_name_kobj, &string_attr_group);
> +}
> +
> +int populate_string_elements_from_buffer(u8 *buffer_ptr, u32 *buffer_size,
> +					 int instance_id)
> +{
> +	int reqs;
> +	struct string_data *string_data = &bioscfg_drv.string_data[instance_id];
> +
> +	strscpy(string_data->common.display_name_language_code,
> +		LANG_CODE_STR,
> +		sizeof(string_data->common.display_name_language_code));
> +
> +	// VALUE:
> +	get_string_from_buffer(&buffer_ptr, buffer_size, string_data->current_value,
> +			       sizeof(string_data->current_value));
> +
> +	// PATH:
> +	get_string_from_buffer(&buffer_ptr, buffer_size, string_data->common.path,
> +			       sizeof(string_data->common.path));
> +
> +	// IS_READONLY:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->common.is_readonly);
> +
> +	//DISPLAY_IN_UI:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->common.display_in_ui);
> +
> +	// REQUIRES_PHYSICAL_PRESENCE:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->common.requires_physical_presence);
> +
> +	// SEQUENCE:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->common.sequence);
> +
> +	// PREREQUISITES_SIZE:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->common.prerequisites_size);
> +
> +	if (string_data->common.prerequisites_size > MAX_PREREQUISITES_SIZE) {
> +		/* Report a message and limit prerequisite size to maximum value */
> +		pr_warn("String Prerequisites size value exceeded the maximum number of elements supported or data may be malformed\n");
> +		string_data->common.prerequisites_size = MAX_PREREQUISITES_SIZE;
> +	}
> +
> +	// PREREQUISITES:
> +	for (reqs = 0;
> +	     reqs < string_data->common.prerequisites_size && reqs < MAX_PREREQUISITES_SIZE;
> +	     reqs++)
> +		get_string_from_buffer(&buffer_ptr, buffer_size,
> +				       string_data->common.prerequisites[reqs],
> +				       sizeof(string_data->common.prerequisites[reqs]));
> +
> +	// SECURITY_LEVEL:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->common.security_level);
> +
> +	// STR_MIN_LENGTH:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->min_length);
> +
> +	// STR_MAX_LENGTH:
> +	get_integer_from_buffer(&buffer_ptr, buffer_size,
> +				&string_data->max_length);
> +
> +	return 0;
> +}
> +
> +/*
> + * exit_string_attributes() - Clear all attribute data
> + *
> + * Clears all data allocated for this group of attributes
> + */
> +void exit_string_attributes(void)
> +{
> +	int instance_id;
> +
> +	for (instance_id = 0; instance_id < bioscfg_drv.string_instances_count;
> +	     instance_id++) {
> +		struct kobject *attr_name_kobj =
> +			bioscfg_drv.string_data[instance_id].attr_name_kobj;
> +
> +		if (attr_name_kobj)
> +			sysfs_remove_group(attr_name_kobj, &string_attr_group);
> +	}
> +	bioscfg_drv.string_instances_count = 0;
> +
> +	kfree(bioscfg_drv.string_data);
> +	bioscfg_drv.string_data = NULL;
> +}
> 

+ all copy-pasted issues.

-- 
 i.