On Wed, Nov 9, 2022 at 2:05 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> Hi,
>
> On 11/9/22 21:00, Jorge Lopez wrote:
> > Hi Hans,
> >
> > On Wed, Nov 9, 2022 at 12:10 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> >>
> >> Hi,
> >>
> >> On 11/9/22 18:24, Jorge Lopez wrote:
> >>> HI Hans,
> >>>
> >>> Please see questions and comments below.
> >>>
> >>> On Tue, Nov 8, 2022 at 8:51 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> >>>>
> >>>> Hi Jorge,
> >>>>
> >>>> Review comments inline.
> >>>>
> >>>> On 10/20/22 22:10, Jorge Lopez wrote:
> >>>>> The purpose for this patch is submit HP BIOSCFG driver to be list of
> >>>>> HP Linux kernel drivers. The driver include a total of 12 files
> >>>>> broken in several patches. This is set 1 of 4.
> >>>>>
> >>>>> 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 PC’s 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 BISOCFG 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 features such Secure Platform Management, Sure
> >>>>> Admin, and Sure Start. Each section provides security feature
> >>>>> description and identifies sysfs directories and files exposed by
> >>>>> the driver.
> >>>>>
> >>>>> Many HP Commercial PC’s 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 PC’s 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 Sure Admin cryptographic signature-based authorization string
> >>>>> that the BIOS will use to verify authorization to modify the setting.
> >>>>>
> >>>>> Signed-off-by: Jorge Lopez <jorge.lopez2@xxxxxx>
> >>>>>
> >>>>> ---
> >>>>> Based on the latest platform-drivers-x86.git/for-next
> >>>>> ---
> >>>>> .../x86/hp/hp-bioscfg/biosattr-interface.c | 285 ++++++++
> >>>>> drivers/platform/x86/hp/hp-bioscfg/bioscfg.h | 671 ++++++++++++++++++
> >>>>> .../x86/hp/hp-bioscfg/enum-attributes.c | 521 ++++++++++++++
> >>>>> 3 files changed, 1477 insertions(+)
> >>>>> create mode 100644 drivers/platform/x86/hp/hp-bioscfg/biosattr-interface.c
> >>>>> create mode 100644 drivers/platform/x86/hp/hp-bioscfg/bioscfg.h
> >>>>> create mode 100644 drivers/platform/x86/hp/hp-bioscfg/enum-attributes.c
> >>>>>
> >>>>> diff --git a/drivers/platform/x86/hp/hp-bioscfg/biosattr-interface.c b/drivers/platform/x86/hp/hp-bioscfg/biosattr-interface.c
> >>>>> new file mode 100644
> >>>>> index 000000000000..f0c919bf3ab0
> >>>>> --- /dev/null
> >>>>> +++ b/drivers/platform/x86/hp/hp-bioscfg/biosattr-interface.c
> >>>>> @@ -0,0 +1,285 @@
> >>>>> +// SPDX-License-Identifier: GPL-2.0
> >>>>> +/*
> >>>>> + * Functions corresponding to methods under BIOS interface GUID
> >>>>> + * for use with hp-bioscfg driver.
> >>>>> + *
> >>>>> + * Copyright (c) 2022 Hewlett-Packard Inc.
> >>>>> + */
> >>>>> +
> >>>>> +#include <linux/wmi.h>
> >>>>> +#include "bioscfg.h"
> >>>>> +
> >>>>> +#define SET_DEFAULT_VALUES_METHOD_ID 0x02
> >>>>> +#define SET_BIOS_DEFAULTS_METHOD_ID 0x03
> >>>>> +#define SET_ATTRIBUTE_METHOD_ID 0x04
> >>>>> +
> >>>>> +/*
> >>>>> + * set_attribute() - Update an attribute value
> >>>>> + * @a_name: The attribute name
> >>>>> + * @a_value: The attribute value
> >>>>> + *
> >>>>> + * Sets an attribute to new value
> >>>>> + */
> >>>>> +int hp_set_attribute(const char *a_name, const char *a_value)
> >>>>> +{
> >>>>> + size_t security_area_size;
> >>>>> + size_t a_name_size, a_value_size;
> >>>>> + u16 *buffer = NULL;
> >>>>> + u16 *start = NULL;
> >>>>> + int buffer_size;
> >>>>
> >>>> You have 2 spaces between int and buffer_size here, please drop
> >>>> one.
> >>>>
> >>>>
> >>>>> + int ret;
> >>>>> + int instance;
> >>>>> + char *auth_empty_value = " ";
> >>>>> +
> >>>>> + mutex_lock(&bioscfg_drv.mutex);
> >>>>> + if (!bioscfg_drv.bios_attr_wdev) {
> >>>>> + ret = -ENODEV;
> >>>>> + goto out_set_attribute;
> >>>>> + }
> >>>>> +
> >>>>> + instance = get_password_instance_for_type(SETUP_PASSWD);
> >>>>> + if (instance < 0)
> >>>>> + goto out_set_attribute;
> >>>>> +
> >>>>> + if (strlen(bioscfg_drv.password_data[instance].current_password) == 0)
> >>>>> + strncpy(bioscfg_drv.password_data[instance].current_password,
> >>>>> + auth_empty_value,
> >>>>> + sizeof(bioscfg_drv.password_data[instance].current_password));
> >>>>
> >>>> strncpy does not guarantee 0 termination of the destination buffer,
> >>>> please use strscpy.
> >>>>
> >>>>> +
> >>>>> + a_name_size = calculate_string_buffer(a_name);
> >>>>> + a_value_size = calculate_string_buffer(a_value);
> >>>>> + security_area_size = calculate_security_buffer(bioscfg_drv.password_data[instance].current_password);
> >>>>> + buffer_size = a_name_size + a_value_size + security_area_size;
> >>>>> +
> >>>>> + buffer = kzalloc(buffer_size, GFP_KERNEL);
> >>>>> + if (!buffer) {
> >>>>> + ret = -ENOMEM;
> >>>>> + goto out_set_attribute;
> >>>>> + }
> >>>>> +
> >>>>> + /* build variables to set */
> >>>>> + start = buffer;
> >>>>> + start = ascii_to_utf16_unicode(start, a_name);
> >>>>> + if (!start)
> >>>>> + goto out_set_attribute;
> >>>>> +
> >>>>> + start = ascii_to_utf16_unicode(start, a_value);
> >>>>> + if (!start)
> >>>>> + goto out_set_attribute;
> >>>>> +
> >>>>> + populate_security_buffer(start, bioscfg_drv.password_data[instance].current_password);
> >>>>> + ret = hp_wmi_set_bios_setting(buffer, buffer_size);
> >>>>> +
> >>>>> +
> >>>>> +out_set_attribute:
> >>>>> + kfree(buffer);
> >>>>> + mutex_unlock(&bioscfg_drv.mutex);
> >>>>> + return ret;
> >>>>> +}
> >>>>> +
> >>>>> +/*
> >>>>> + * hp_wmi_perform_query
> >>>>> + *
> >>>>> + * query: The commandtype (enum hp_wmi_commandtype)
> >>>>> + * write: The command (enum hp_wmi_command)
> >>>>> + * buffer: Buffer used as input and/or output
> >>>>> + * insize: Size of input buffer
> >>>>> + * outsize: Size of output buffer
> >>>>> + *
> >>>>> + * returns zero on success
> >>>>> + * an HP WMI query specific error code (which is positive)
> >>>>> + * -EINVAL if the query was not successful at all
> >>>>> + * -EINVAL if the output buffer size exceeds buffersize
> >>>>> + *
> >>>>> + * Note: The buffersize must at least be the maximum of the input and output
> >>>>> + * size. E.g. Battery info query is defined to have 1 byte input
> >>>>> + * and 128 byte output. The caller would do:
> >>>>> + * buffer = kzalloc(128, GFP_KERNEL);
> >>>>> + * ret = hp_wmi_perform_query(HPWMI_BATTERY_QUERY, HPWMI_READ, buffer, 1, 128)
> >>>>> + */
> >>>>> +int hp_wmi_perform_query(int query, enum hp_wmi_command command, void *buffer, int insize, int outsize)
> >>>>> +{
> >>>>> + struct acpi_buffer input, output = { ACPI_ALLOCATE_BUFFER, NULL };
> >>>>> + struct bios_return *bios_return;
> >>>>> + union acpi_object *obj = NULL;
> >>>>> + struct bios_args *args = NULL;
> >>>>> + int mid, actual_insize, actual_outsize;
> >>>>> + size_t bios_args_size;
> >>>>> + int ret;
> >>>>> +
> >>>>> + mid = encode_outsize_for_pvsz(outsize);
> >>>>> + if (WARN_ON(mid < 0))
> >>>>> + return mid;
> >>>>> +
> >>>>> + actual_insize = insize;
> >>>>> + bios_args_size = struct_size(args, data, insize);
> >>>>> + args = kmalloc(bios_args_size, GFP_KERNEL);
> >>>>> + if (!args)
> >>>>> + return -ENOMEM;
> >>>>> +
> >>>>> + input.length = bios_args_size;
> >>>>> + input.pointer = args;
> >>>>> +
> >>>>> + args->signature = 0x55434553;
> >>>>> + args->command = command;
> >>>>> + args->commandtype = query;
> >>>>> + args->datasize = insize;
> >>>>> + memcpy(args->data, buffer, flex_array_size(args, data, insize));
> >>>>> +
> >>>>> + ret = wmi_evaluate_method(HP_WMI_BIOS_GUID, 0, mid, &input, &output);
> >>>>> + bioscfg_drv.last_wmi_status = ret;
> >>>>> + if (ret)
> >>>>> + goto out_free;
> >>>>> +
> >>>>> + obj = output.pointer;
> >>>>> + if (!obj) {
> >>>>> + ret = -EINVAL;
> >>>>> + goto out_free;
> >>>>> + }
> >>>>> +
> >>>>
> >>>> You need to check the type of obj here before dereferencing
> >>>> obj as if it is a buffer.
> >>>>
> >>>>> + bios_return = (struct bios_return *)obj->buffer.pointer;
> >>>>> + ret = bios_return->return_code;
> >>>>> + bioscfg_drv.last_wmi_status = ret;
> >>>>> + if (ret) {
> >>>>> + if (ret != HPWMI_RET_UNKNOWN_COMMAND &&
> >>>>> + ret != HPWMI_RET_UNKNOWN_CMDTYPE)
> >>>>> + pr_warn("query 0x%x returned error 0x%x\n", query, ret);
> >>>>> + goto out_free;
> >>>>> + }
> >>>>> +
> >>>>> + /* Ignore output data of zero size */
> >>>>> + if (!outsize)
> >>>>> + goto out_free;
> >>>>> +
> >>>>> + actual_outsize = min(outsize, (int)(obj->buffer.length - sizeof(*bios_return)));
> >>>>> + memcpy(buffer, obj->buffer.pointer + sizeof(*bios_return), actual_outsize);
> >>>>> + memset(buffer + actual_outsize, 0, outsize - actual_outsize);
> >>>>> +
> >>>>> +out_free:
> >>>>> + kfree(obj);
> >>>>> + kfree(args);
> >>>>> + return ret;
> >>>>> +}
> >>>>> +
> >>>>> +/*
> >>>>> + * ascii_to_utf16_unicode - Convert ascii string to UTF-16 unicode
> >>>>> + *
> >>>>> + * @p: Unicode buffer address
> >>>>> + * @str: string to convert to unicode
> >>>>> + *
> >>>>> + * Returns a void pointer to the buffer containing unicode string
> >>>>> + */
> >>>>> +void *ascii_to_utf16_unicode(u16 *p, const u8 *str)
> >>>>> +{
> >>>>> + int len = strlen(str);
> >>>>> + int ret;
> >>>>> +
> >>>>> + /*
> >>>>> + * Add null character when reading an empty string
> >>>>> + */
> >>>>> + if (len == 0) {
> >>>>> + *p++ = 2;
> >>>>> + *p++ = (u8)0x00;
> >>>>> + return p;
> >>>>
> >>>> This does not match with calculate_string_buffer() which will
> >>>> return 2 for a 0 length string while you are using 4 bytes here.
> >>>>
> >>>> I guess this may also be why you need to use " " for
> >>>> auth_empty_value above, so as to avoid this bug.
> >>>>
> >>> HP BIOS expects 2 characters when an empty string is being converted
> >>> to u16 hence the reason for returning 2 instead of zero. This is an
> >>> intended behavior and needed when allocating a buffer and writing to
> >>> BIOS.
> >>
> >> Right I understand that, it wants 2 characters for the 16 bit length
> >> word, but why not write 0 to that 16 bit length word. Why actually
> >> say the string-buffer length is 2 bytes long / and then write
> >> a 16-bit word with value 0?
> >>
> >> What you are doing now creates a 4 byte buffer like this:
> >>
> >> u8 buf[4] = { 0x02, 0x00, 0x00, 0x00 }
> >>
> >> Why not just create a 2 byte buffer like this:
> >>
> >> u8 buf[2] = { 0x00, 0x00 }
> >>
> >> ?
> >>
> >>
> >> Also I'm wondering why the empty auth string is " " and
> >> not "" ?
> >>
> >>
> >
> > The string returned for an empty string is 4 bytes. The returned
> > string includes two bytes for the string size in bytes and the
> > remaining bytes are the string.
> > Size = 0x02, 0x00
> > String = 0x00, 0x00
> >
> > All strings return include the string size in bytes followed by the u16 string
>
> Right I understand that, but why is the "String = 0x00, 0x00"
> there ? All the non-0-length strings are not 0 terminated,
> why does the zero length string needs to be specified as length 2
> (1 u16) and then have that u16 be a 0 terminator ?
>
It is a specific format required by BIOS for any zero-length strings.
I don't know the reason why BIOS wants that format.
> Have you tried just using Size[2] = 0x00, 0x00 and String[0] for
> an empty string?
>
I tried during the development process and each time the data is
rejected by BIOS.
> ###
>
> Also you did not answer this separate question:
>
> I'm wondering why the empty auth string is " " and not "" ?
>
That was an oversight. It should be '""'. I will make the change
>
> Regards,
>
> Hans
>
>
