Re: [PATCH v3 1/3] efi_loader: add SMBIOS table measurement

On Thu, 21 Oct 2021 at 09:17, Heinrich Schuchardt xypron.glpk@gmx.de wrote:

On 10/1/21 1:18 PM, Masahisa Kojima wrote:

...

TCG PC Client spec requires to measure the SMBIOS

I guess you mean the "TCG PC Client Platform Firmware Profile Specification"? Please, provide the full name in the commit message.

Sorry, I will write full spec name.

...

table that contain static configuration information (e.g. Platform Manufacturer Enterprise Number assigned by IANA, platform model number, Vendor and Device IDs for each SMBIOS table).

The device- and environment-dependent information such as serial number is cleared to zero or space character for the measurement.

This contradicts the spec requiring the device IDs (i.e. the serial number) to be measured. You don't want to get the same measurement when the device is swapped.

In my understanding, the same measurement result is expected among one product. Even if the device is swapped, measurement is the same. If device unique information such as serial number is included in the measurement, attestation process will be very complicated.

...

Existing smbios_string() function returns pointer to the string with const qualifier, but exisintg use case is updating version string and const qualifier must be removed. This commit removes const qualifier from smbios_string() return value and reuses to clear the strings for the measurement.

This commit also fixes the following compiler warning:

lib/smbios-parser.c:59:39: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] const struct smbios_header *header = (struct smbios_header *)entry->struct_table_address;

Signed-off-by: Masahisa Kojima masahisa.kojima@linaro.org

Changes in v3:

• TCG spec says EV_SEPARATOR must be the last, swap the order of measurement

Changes in v2:

• use flexible array for table_entry field

• modify funtion name to find_smbios_table()

• remove unnecessary const qualifier from smbios_string()

• create non-const version of next_header()

  include/efi_loader.h | 2 + include/efi_tcg2.h | 15 ++++ include/smbios.h | 17 +++- lib/efi_loader/Kconfig | 1 + lib/efi_loader/efi_boottime.c | 2 + lib/efi_loader/efi_smbios.c | 2 - lib/efi_loader/efi_tcg2.c | 84 +++++++++++++++++++ lib/smbios-parser.c | 152 +++++++++++++++++++++++++++++++--- 8 files changed, 261 insertions(+), 14 deletions(-)

diff --git a/include/efi_loader.h b/include/efi_loader.h index c440962fe5..13f0c24058 100644 --- a/include/efi_loader.h +++ b/include/efi_loader.h @@ -308,6 +308,8 @@ extern const efi_guid_t efi_guid_capsule_report; extern const efi_guid_t efi_guid_firmware_management_protocol; /* GUID for the ESRT */ extern const efi_guid_t efi_esrt_guid; +/* GUID of the SMBIOS table */ +extern const efi_guid_t smbios_guid;

extern char __efi_runtime_start[], __efi_runtime_stop[]; extern char __efi_runtime_rel_start[], __efi_runtime_rel_stop[]; diff --git a/include/efi_tcg2.h b/include/efi_tcg2.h index 8f02d4fb0b..ca66695b39 100644 --- a/include/efi_tcg2.h +++ b/include/efi_tcg2.h @@ -210,6 +210,21 @@ struct efi_tcg2_uefi_variable_data { u8 variable_data[1]; };

+/**

• • struct tdUEFI_HANDOFF_TABLE_POINTERS2 - event log structure of SMBOIS tables
• • @table_description_size: size of table description
• • @table_description: table description
• • @number_of_tables: number of uefi configuration table
• • @table_entry: uefi configuration table entry
• */

+#define SMBIOS_HANDOFF_TABLE_DESC "SmbiosTable" +struct smbios_handoff_table_pointers2 {

• u8 table_description_size;
  

• u8 table_description[sizeof(SMBIOS_HANDOFF_TABLE_DESC)];
  

• u64 number_of_tables;
  

• struct efi_configuration_table table_entry[];
  

+} __packed;

• 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/include/smbios.h b/include/smbios.h index aa6b6f3849..acfcbfe2ca 100644 --- a/include/smbios.h +++ b/include/smbios.h @@ -260,9 +260,9 @@ const struct smbios_header *smbios_header(const struct smbios_entry *entry, int

• @header: pointer to struct smbios_header
• @index: string index

• • @return: NULL or a valid const char pointer

• • @return: NULL or a valid char pointer
  */

-const char *smbios_string(const struct smbios_header *header, int index); +char *smbios_string(const struct smbios_header *header, int index);

This looks wrong. Your code is changing the actual SMBIOS table that we will pass via an UEFI configuration table. Why would you do this? For instance the serial number is an information that you actually want to see in the operating system. I think you should first copy the string and then manipulate the copy if this is necessary for the measurement.

No, I prepare the copied SMBIOS table and update it for the measurement.

tcg2_measure_smbios(): + smbios_copy = (struct smbios_header *)((uintptr_t)&event->table_entry[0].table); + memcpy(&event->table_entry[0].table, + (void *)((uintptr_t)entry->struct_table_address), + entry->struct_table_length); + + smbios_prepare_measurement(entry, smbios_copy);

I have tested that linux can show the original SMBIOS table by "dmidocode" command.

Thanks, Masahisa Kojima

Best regards

Heinrich

...

/**

• smbios_update_version() - Update the version string

@@ -292,4 +292,17 @@ int smbios_update_version(const char *version); */ int smbios_update_version_full(void *smbios_tab, const char *version);

+/**

• • smbios_prepare_measurement() - Update smbios table for the measurement
• • TCG specification requires to measure static configuration information.
• • This function clear the device dependent parameters such as
• • serial number for the measurement.
• • @entry: pointer to a struct smbios_entry
• • @header: pointer to a struct smbios_header
• */

+void smbios_prepare_measurement(const struct smbios_entry *entry,

•                         struct smbios_header *header);
  

• #endif /* _SMBIOS_H_ */

diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig index f48d9e8b51..e691b1ea96 100644 --- a/lib/efi_loader/Kconfig +++ b/lib/efi_loader/Kconfig @@ -320,6 +320,7 @@ config EFI_TCG2_PROTOCOL select SHA384 select SHA512 select HASH

• select SMBIOS_PARSER
  help
    Provide a EFI_TCG2_PROTOCOL implementation using the TPM hardware
    of the platform.
  

diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c index f0283b539e..701e2212c8 100644 --- a/lib/efi_loader/efi_boottime.c +++ b/lib/efi_loader/efi_boottime.c @@ -86,6 +86,8 @@ const efi_guid_t efi_guid_event_group_reset_system = /* GUIDs of the Load File and Load File2 protocols */ const efi_guid_t efi_guid_load_file_protocol = EFI_LOAD_FILE_PROTOCOL_GUID; const efi_guid_t efi_guid_load_file2_protocol = EFI_LOAD_FILE2_PROTOCOL_GUID; +/* GUID of the SMBIOS table */ +const efi_guid_t smbios_guid = SMBIOS_TABLE_GUID;

static efi_status_t EFIAPI efi_disconnect_controller( efi_handle_t controller_handle, diff --git a/lib/efi_loader/efi_smbios.c b/lib/efi_loader/efi_smbios.c index 2eb4cb1c1a..fc0b23397c 100644 --- a/lib/efi_loader/efi_smbios.c +++ b/lib/efi_loader/efi_smbios.c @@ -13,8 +13,6 @@ #include <mapmem.h> #include <smbios.h>

-static const efi_guid_t smbios_guid = SMBIOS_TABLE_GUID;

• /*
  • Install the SMBIOS table as a configuration table.

diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c index d3b8f93f14..f14d4d6da1 100644 --- a/lib/efi_loader/efi_tcg2.c +++ b/lib/efi_loader/efi_tcg2.c @@ -14,6 +14,7 @@ #include <efi_tcg2.h> #include <log.h> #include <malloc.h> +#include <smbios.h> #include <version.h> #include <tpm-v2.h> #include <u-boot/hash-checksum.h> @@ -1455,6 +1456,81 @@ error: return ret; }

+/**

• • tcg2_measure_smbios() - measure smbios table
• • @dev: TPM device
• • @entry: pointer to the smbios_entry structure
• • Return: status code
• */

+static efi_status_t +tcg2_measure_smbios(struct udevice *dev,

•             const struct smbios_entry *entry)
  

+{

• efi_status_t ret;
  

• struct smbios_header *smbios_copy;
  

• struct smbios_handoff_table_pointers2 *event = NULL;
  

• u32 event_size;
  

• /*
  

•  * TCG PC Client PFP Spec says
  

•  * "SMBIOS structures that contain static configuration information
  

•  * (e.g. Platform Manufacturer Enterprise Number assigned by IANA,
  

•  * platform model number, Vendor and Device IDs for each SMBIOS table)
  

•  * that is relevant to the security of the platform MUST be measured".
  

•  * Device dependent parameters such as serial number are cleared to
  

•  * zero or spaces for the measurement.
  

•  */
  

• event_size = sizeof(struct smbios_handoff_table_pointers2) +
  

•              FIELD_SIZEOF(struct efi_configuration_table, guid) +
  

•              entry->struct_table_length;
  

• event = calloc(1, event_size);
  

• if (!event) {
  

•         ret = EFI_OUT_OF_RESOURCES;
  

•         goto out;
  

• }
  

• event->table_description_size = sizeof(SMBIOS_HANDOFF_TABLE_DESC);
  

• memcpy(event->table_description, SMBIOS_HANDOFF_TABLE_DESC,
  

•        sizeof(SMBIOS_HANDOFF_TABLE_DESC));
  

• put_unaligned_le64(1, &event->number_of_tables);
  

• guidcpy(&event->table_entry[0].guid, &smbios_guid);
  

• smbios_copy = (struct smbios_header *)((uintptr_t)&event->table_entry[0].table);
  

• memcpy(&event->table_entry[0].table,
  

•        (void *)((uintptr_t)entry->struct_table_address),
  

•        entry->struct_table_length);
  

• smbios_prepare_measurement(entry, smbios_copy);
  

• ret = tcg2_measure_event(dev, 1, EV_EFI_HANDOFF_TABLES2, event_size,
  

•                          (u8 *)event);
  

• if (ret != EFI_SUCCESS)
  

•         goto out;
  

+out:

• free(event);
  

• return ret;
  

+}

+/**

• • find_smbios_table() - find smbios table
• • Return: pointer to the smbios table
• */

+static void *find_smbios_table(void) +{

• u32 i;
  

• for (i = 0; i < systab.nr_tables; i++) {
  

•         if (!guidcmp(&smbios_guid, &systab.tables[i].guid))
  

•                 return systab.tables[i].table;
  

• }
  

• return NULL;
  

+}

• /**
  • efi_tcg2_measure_efi_app_invocation() - measure efi app invocation

@@ -1466,6 +1542,7 @@ efi_status_t efi_tcg2_measure_efi_app_invocation(void) u32 pcr_index; struct udevice *dev; u32 event = 0;

• struct smbios_entry *entry;
  
  if (tcg2_efi_app_invoked)
          return EFI_SUCCESS;
  

@@ -1484,6 +1561,13 @@ efi_status_t efi_tcg2_measure_efi_app_invocation(void) if (ret != EFI_SUCCESS) goto out;

• entry = (struct smbios_entry *)find_smbios_table();
  

• if (entry) {
  

•         ret = tcg2_measure_smbios(dev, entry);
  

•         if (ret != EFI_SUCCESS)
  

•                 goto out;
  

• }
  

• for (pcr_index = 0; pcr_index <= 7; pcr_index++) {
          ret = tcg2_measure_event(dev, pcr_index, EV_SEPARATOR,
                                   sizeof(event), (u8 *)&event);
  

diff --git a/lib/smbios-parser.c b/lib/smbios-parser.c index 34203f952c..596a967302 100644 --- a/lib/smbios-parser.c +++ b/lib/smbios-parser.c @@ -39,10 +39,8 @@ const struct smbios_entry *smbios_entry(u64 address, u32 size) return entry; }

-static const struct smbios_header *next_header(const struct smbios_header *curr) +static u8 *find_next_header(u8 *pos) {

• u8 *pos = ((u8 *)curr) + curr->length;
  

• /* search for _double_ NULL bytes */
  while (!((*pos == 0) && (*(pos + 1) == 0)))
          pos++;
  

@@ -50,13 +48,27 @@ static const struct smbios_header *next_header(const struct smbios_header *curr) /* step behind the double NULL bytes */ pos += 2;

• return (struct smbios_header *)pos;
  

• return pos;
  

+}

+static struct smbios_header *get_next_header(struct smbios_header *curr) +{

• u8 *pos = ((u8 *)curr) + curr->length;
  

• return (struct smbios_header *)find_next_header(pos);
  

+}

+static const struct smbios_header *next_header(const struct smbios_header *curr) +{

• u8 *pos = ((u8 *)curr) + curr->length;
  

• return (struct smbios_header *)find_next_header(pos);
  

  }

  const struct smbios_header *smbios_header(const struct smbios_entry *entry, int type) { const unsigned int num_header = entry->struct_count;

• const struct smbios_header *header = (struct smbios_header *)entry->struct_table_address;
  

• const struct smbios_header *header = (struct smbios_header *)((uintptr_t)entry->struct_table_address);
  
  for (unsigned int i = 0; i < num_header; i++) {
          if (header->type == type)
  

@@ -68,8 +80,8 @@ const struct smbios_header *smbios_header(const struct smbios_entry *entry, int return NULL; }

-static const char *string_from_smbios_table(const struct smbios_header *header,

•                                       int idx)
  

+static char *string_from_smbios_table(const struct smbios_header *header,

•                               int idx)
  

  { unsigned int i = 1; u8 *pos;

@@ -86,10 +98,10 @@ static const char *string_from_smbios_table(const struct smbios_header *header, pos++; }

• return (const char *)pos;
  

• return (char *)pos;
  

  }

-const char *smbios_string(const struct smbios_header *header, int index) +char *smbios_string(const struct smbios_header *header, int index) { if (!header) return NULL; @@ -109,7 +121,7 @@ int smbios_update_version_full(void *smbios_tab, const char *version) if (!hdr) return log_msg_ret("tab", -ENOENT); bios = (struct smbios_type0 *)hdr;

• ptr = (char *)smbios_string(hdr, bios->bios_ver);
  

• ptr = smbios_string(hdr, bios->bios_ver);
  if (!ptr)
          return log_msg_ret("str", -ENOMEDIUM);
  
  

@@ -132,3 +144,123 @@ int smbios_update_version_full(void *smbios_tab, const char *version)

  return 0;

}

+struct smbios_filter_param {

• u32 offset;
  

• u32 size;
  

• bool is_string;
  

+};

+struct smbios_filter_table {

• int type;
  

• struct smbios_filter_param *params;
  

• u32 count;
  

+};

+struct smbios_filter_param smbios_type1_filter_params[] = {

• {offsetof(struct smbios_type1, serial_number),
  

•  FIELD_SIZEOF(struct smbios_type1, serial_number), true},
  

• {offsetof(struct smbios_type1, uuid),
  

•  FIELD_SIZEOF(struct smbios_type1, uuid), false},
  

• {offsetof(struct smbios_type1, wakeup_type),
  

•  FIELD_SIZEOF(struct smbios_type1, wakeup_type), false},
  

+};

+struct smbios_filter_param smbios_type2_filter_params[] = {

• {offsetof(struct smbios_type2, serial_number),
  

•  FIELD_SIZEOF(struct smbios_type2, serial_number), true},
  

• {offsetof(struct smbios_type2, chassis_location),
  

•  FIELD_SIZEOF(struct smbios_type2, chassis_location), false},
  

+};

+struct smbios_filter_param smbios_type3_filter_params[] = {

• {offsetof(struct smbios_type3, serial_number),
  

•  FIELD_SIZEOF(struct smbios_type3, serial_number), true},
  

• {offsetof(struct smbios_type3, asset_tag_number),
  

•  FIELD_SIZEOF(struct smbios_type3, asset_tag_number), true},
  

+};

+struct smbios_filter_param smbios_type4_filter_params[] = {

• {offsetof(struct smbios_type4, serial_number),
  

•  FIELD_SIZEOF(struct smbios_type4, serial_number), true},
  

• {offsetof(struct smbios_type4, asset_tag),
  

•  FIELD_SIZEOF(struct smbios_type4, asset_tag), true},
  

• {offsetof(struct smbios_type4, part_number),
  

•  FIELD_SIZEOF(struct smbios_type4, part_number), true},
  

• {offsetof(struct smbios_type4, core_count),
  

•  FIELD_SIZEOF(struct smbios_type4, core_count), false},
  

• {offsetof(struct smbios_type4, core_enabled),
  

•  FIELD_SIZEOF(struct smbios_type4, core_enabled), false},
  

• {offsetof(struct smbios_type4, thread_count),
  

•  FIELD_SIZEOF(struct smbios_type4, thread_count), false},
  

• {offsetof(struct smbios_type4, core_count2),
  

•  FIELD_SIZEOF(struct smbios_type4, core_count2), false},
  

• {offsetof(struct smbios_type4, core_enabled2),
  

•  FIELD_SIZEOF(struct smbios_type4, core_enabled2), false},
  

• {offsetof(struct smbios_type4, thread_count),
  

•  FIELD_SIZEOF(struct smbios_type4, thread_count2), false},
  

• {offsetof(struct smbios_type4, voltage),
  

•  FIELD_SIZEOF(struct smbios_type4, voltage), false},
  

+};

+struct smbios_filter_table smbios_filter_tables[] = {

• {SMBIOS_SYSTEM_INFORMATION, smbios_type1_filter_params,
  

•  ARRAY_SIZE(smbios_type1_filter_params)},
  

• {SMBIOS_BOARD_INFORMATION, smbios_type2_filter_params,
  

•  ARRAY_SIZE(smbios_type2_filter_params)},
  

• {SMBIOS_SYSTEM_ENCLOSURE, smbios_type3_filter_params,
  

•  ARRAY_SIZE(smbios_type3_filter_params)},
  

• {SMBIOS_PROCESSOR_INFORMATION, smbios_type4_filter_params,
  

•  ARRAY_SIZE(smbios_type4_filter_params)},
  

+};

+static void clear_smbios_table(struct smbios_header *header,

•                        struct smbios_filter_param *filter,
  

•                        u32 count)
  

+{

• u32 i;
  

• char *str;
  

• u8 string_id;
  

• for (i = 0; i < count; i++) {
  

•         if (filter[i].is_string) {
  

•                 string_id = *((u8 *)header + filter[i].offset);
  

•                 if (string_id == 0) /* string is empty */
  

•                         continue;
  

•                 str = smbios_string(header, string_id);
  

•                 if (!str)
  

•                         continue;
  

•                 /* string is cleared to space, keep '\0' terminator */
  

•                 memset(str, ' ', strlen(str));
  

•         } else {
  

•                 memset((void *)((u8 *)header + filter[i].offset),
  

•                        0, filter[i].size);
  

•         }
  

• }
  

+}

+void smbios_prepare_measurement(const struct smbios_entry *entry,

•                         struct smbios_header *smbios_copy)
  

+{

• u32 i, j;
  

• struct smbios_header *header;
  

• for (i = 0; i < ARRAY_SIZE(smbios_filter_tables); i++) {
  

•         header = smbios_copy;
  

•         for (j = 0; j < entry->struct_count; j++) {
  

•                 if (header->type == smbios_filter_tables[i].type)
  

•                         break;
  

•                 header = get_next_header(header);
  

•         }
  

•         if (j >= entry->struct_count)
  

•                 continue;
  

•         clear_smbios_table(header,
  

•                            smbios_filter_tables[i].params,
  

•                            smbios_filter_tables[i].count);
  

• }
  

+}