Re: [PATCH v3 2/5] efi_loader: add boot variable measurement

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

On Fri, Aug 06, 2021 at 04:02:12PM +0900, Masahisa Kojima wrote:
> TCG PC Client PFP spec requires to measure "Boot####"
> and "BootOrder" variables, EV_SEPARATOR event prior
> to the Ready to Boot invocation.
> Since u-boot does not implement Ready to Boot event,
> these measurements are performed when efi_start_image() is called.
> 
> TCG spec also requires to measure "Calling EFI Application from
> Boot Option" for each boot attempt, and "Returning from EFI
> Application from Boot Option" if a boot device returns control
> back to the Boot Manager.
> 
> Signed-off-by: Masahisa Kojima <masahisa.kojima@linaro.org>
> ---
> Changes in v3:
> - modify log output
> 
> Changes in v2:
> - use efi_create_indexed_name() for "Boot####" variable
> 
>  include/efi_loader.h          |   4 ++
>  include/tpm-v2.h              |  18 ++++-
>  lib/efi_loader/efi_boottime.c |  20 ++++++
>  lib/efi_loader/efi_tcg2.c     | 121 ++++++++++++++++++++++++++++++++++
>  4 files changed, 162 insertions(+), 1 deletion(-)
> 
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index a120d94431..345cbb72c4 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -499,6 +499,10 @@ efi_status_t efi_run_image(void *source_buffer, efi_uintn_t source_size);
>  efi_status_t efi_init_variables(void);
>  /* Notify ExitBootServices() is called */
>  void efi_variables_boot_exit_notify(void);
> +/* Measure efi application invocation */
> +efi_status_t EFIAPI efi_tcg2_measure_efi_app_invocation(void);
> +/* Measure efi application exit */
> +efi_status_t EFIAPI efi_tcg2_measure_efi_app_exit(void);

I don't think that we need to have EFIAPI specifiers for those functions
as they are not api's.

>  /* Called by bootefi to initialize root node */
>  efi_status_t efi_root_node_register(void);
>  /* Called by bootefi to initialize runtime */
> diff --git a/include/tpm-v2.h b/include/tpm-v2.h
> index 247b386967..325c73006e 100644
> --- a/include/tpm-v2.h
> +++ b/include/tpm-v2.h
> @@ -73,7 +73,7 @@ struct udevice;
>  /*
>   * event types, cf.
>   * "TCG PC Client Platform Firmware Profile Specification", Family "2.0"
> - * rev 1.04, June 3, 2019
> + * Level 00 Version 1.05 Revision 23, May 7, 2021
>   */
>  #define EV_EFI_EVENT_BASE			((u32)0x80000000)
>  #define EV_EFI_VARIABLE_DRIVER_CONFIG		((u32)0x80000001)
> @@ -85,8 +85,24 @@ struct udevice;
>  #define EV_EFI_ACTION				((u32)0x80000007)
>  #define EV_EFI_PLATFORM_FIRMWARE_BLOB		((u32)0x80000008)
>  #define EV_EFI_HANDOFF_TABLES			((u32)0x80000009)
> +#define EV_EFI_PLATFORM_FIRMWARE_BLOB2		((u32)0x8000000A)
> +#define EV_EFI_HANDOFF_TABLES2			((u32)0x8000000B)
> +#define EV_EFI_VARIABLE_BOOT2			((u32)0x8000000C)
>  #define EV_EFI_HCRTM_EVENT			((u32)0x80000010)
>  #define EV_EFI_VARIABLE_AUTHORITY		((u32)0x800000E0)
> +#define EV_EFI_SPDM_FIRMWARE_BLOB		((u32)0x800000E1)
> +#define EV_EFI_SPDM_FIRMWARE_CONFIG		((u32)0x800000E2)
> +
> +#define EFI_CALLING_EFI_APPLICATION         \
> +	"Calling EFI Application from Boot Option"
> +#define EFI_RETURNING_FROM_EFI_APPLICATION  \
> +	"Returning from EFI Application from Boot Option"
> +#define EFI_EXIT_BOOT_SERVICES_INVOCATION   \
> +	"Exit Boot Services Invocation"
> +#define EFI_EXIT_BOOT_SERVICES_FAILED       \
> +	"Exit Boot Services Returned with Failure"
> +#define EFI_EXIT_BOOT_SERVICES_SUCCEEDED    \
> +	"Exit Boot Services Returned with Success"
>  
>  /* TPMS_TAGGED_PROPERTY Structure */
>  struct tpms_tagged_property {
> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> index 0b98e91813..13ab139222 100644
> --- a/lib/efi_loader/efi_boottime.c
> +++ b/lib/efi_loader/efi_boottime.c
> @@ -2994,6 +2994,16 @@ efi_status_t EFIAPI efi_start_image(efi_handle_t image_handle,
>  	image_obj->exit_status = &exit_status;
>  	image_obj->exit_jmp = &exit_jmp;
>  
> +	if (IS_ENABLED(CONFIG_EFI_TCG2_PROTOCOL)) {
> +		if (image_obj->image_type == IMAGE_SUBSYSTEM_EFI_APPLICATION) {
> +			ret = efi_tcg2_measure_efi_app_invocation();
> +			if (ret != EFI_SUCCESS) {
> +				log_warning("tcg2 measurement fails(0x%lx)\n",
> +					    ret);
> +			}
> +		}
> +	}
> +
>  	/* call the image! */
>  	if (setjmp(&exit_jmp)) {
>  		/*
> @@ -3252,6 +3262,16 @@ static efi_status_t EFIAPI efi_exit(efi_handle_t image_handle,
>  	    exit_status != EFI_SUCCESS)
>  		efi_delete_image(image_obj, loaded_image_protocol);
>  
> +	if (IS_ENABLED(CONFIG_EFI_TCG2_PROTOCOL)) {
> +		if (image_obj->image_type == IMAGE_SUBSYSTEM_EFI_APPLICATION) {
> +			ret = efi_tcg2_measure_efi_app_exit();
> +			if (ret != EFI_SUCCESS) {
> +				log_warning("tcg2 measurement fails(0x%lx)\n",
> +					    ret);
> +			}
> +		}
> +	}
> +
>  	/* Make sure entry/exit counts for EFI world cross-overs match */
>  	EFI_EXIT(exit_status);
>  
> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> index a2e9587cd0..7dd30c2bc9 100644
> --- a/lib/efi_loader/efi_tcg2.c
> +++ b/lib/efi_loader/efi_tcg2.c
> @@ -35,6 +35,7 @@ struct event_log_buffer {
>  };
>  
>  static struct event_log_buffer event_log;
> +static bool tcg2_efi_app_invoked;
>  /*
>   * When requesting TPM2_CAP_TPM_PROPERTIES the value is on a standard offset.
>   * Since the current tpm2_get_capability() response buffers starts at
> @@ -1385,6 +1386,126 @@ static efi_status_t tcg2_measure_variable(struct udevice *dev, u32 pcr_index,
>  	return ret;
>  }
>  
> +/**
> + * tcg2_measure_boot_variable() - measure boot variables
> + *
> + * @dev:	TPM device
> + *
> + * Return:	status code
> + */
> +static efi_status_t tcg2_measure_boot_variable(struct udevice *dev)
> +{
> +	u16 *boot_order;
> +	u16 *boot_index;
> +	u16 var_name[] = L"BootOrder";
> +	u16 boot_name[] = L"Boot####";
> +	u8 *bootvar;
> +	efi_uintn_t var_data_size;
> +	u32 count, i;
> +	efi_status_t ret;
> +
> +	boot_order = efi_get_var(var_name, &efi_global_variable_guid,
> +				 &var_data_size);
> +	if (!boot_order) {
> +		ret = EFI_NOT_FOUND;
> +		goto error;
> +	}

What if BootOrder is not defined, but BootNext is defined?

-Takahiro Akashi

> +
> +	ret = tcg2_measure_variable(dev, 1, EV_EFI_VARIABLE_BOOT2, var_name,
> +				    &efi_global_variable_guid, var_data_size,
> +				    (u8 *)boot_order);
> +	if (ret != EFI_SUCCESS)
> +		goto error;
> +
> +	count = var_data_size / sizeof(*boot_order);
> +	boot_index = boot_order;
> +	for (i = 0; i < count; i++) {
> +		efi_create_indexed_name(boot_name, sizeof(boot_name),
> +					"Boot", *boot_index++);
> +
> +		bootvar = efi_get_var(boot_name, &efi_global_variable_guid,
> +				      &var_data_size);
> +
> +		if (!bootvar) {
> +			log_info("%ls not found\n", boot_name);
> +			continue;
> +		}
> +
> +		ret = tcg2_measure_variable(dev, 1, EV_EFI_VARIABLE_BOOT2,
> +					    boot_name,
> +					    &efi_global_variable_guid,
> +					    var_data_size, bootvar);
> +		free(bootvar);
> +		if (ret != EFI_SUCCESS)
> +			goto error;
> +	}
> +
> +error:
> +	free(boot_order);
> +	return ret;
> +}
> +
> +/**
> + * efi_tcg2_measure_efi_app_invocation() - measure efi app invocation
> + *
> + * Return:	status code
> + */
> +efi_status_t EFIAPI efi_tcg2_measure_efi_app_invocation(void)
> +{
> +	efi_status_t ret;
> +	u32 pcr_index;
> +	struct udevice *dev;
> +	u32 event = 0;
> +
> +	if (tcg2_efi_app_invoked)
> +		return EFI_SUCCESS;
> +
> +	ret = platform_get_tpm2_device(&dev);
> +	if (ret != EFI_SUCCESS)
> +		return ret;
> +
> +	ret = tcg2_measure_boot_variable(dev);
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	ret = tcg2_measure_event(dev, 4, EV_EFI_ACTION,
> +				 strlen(EFI_CALLING_EFI_APPLICATION),
> +				 (u8 *)EFI_CALLING_EFI_APPLICATION);
> +	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);
> +		if (ret != EFI_SUCCESS)
> +			goto out;
> +	}
> +
> +	tcg2_efi_app_invoked = true;
> +out:
> +	return ret;
> +}
> +
> +/**
> + * efi_tcg2_measure_efi_app_exit() - measure efi app exit
> + *
> + * Return:	status code
> + */
> +efi_status_t EFIAPI efi_tcg2_measure_efi_app_exit(void)
> +{
> +	efi_status_t ret;
> +	struct udevice *dev;
> +
> +	ret = platform_get_tpm2_device(&dev);
> +	if (ret != EFI_SUCCESS)
> +		return ret;
> +
> +	ret = tcg2_measure_event(dev, 4, EV_EFI_ACTION,
> +				 strlen(EFI_RETURNING_FROM_EFI_APPLICATION),
> +				 (u8 *)EFI_RETURNING_FROM_EFI_APPLICATION);
> +	return ret;
> +}
> +
>  /**
>   * tcg2_measure_secure_boot_variable() - measure secure boot variables
>   *
> -- 
> 2.17.1
>