[PATCH 4/5] efi_loader: add ExitBootServices() measurement

[Heinrich Schuchardt]

On 7/7/21 3:36 PM, Masahisa Kojima wrote:
> TCG PC Client PFP spec requires to measure
> "Exit Boot Services Invocation" if ExitBootServices() is invoked.
> Depending upon the return code from the ExitBootServices() call,
> "Exit Boot Services Returned with Success" or "Exit Boot Services
> Returned with Failure" is also measured.
>
> Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
> ---
>   include/efi_loader.h          |  1 +
>   lib/efi_loader/efi_boottime.c |  5 +++
>   lib/efi_loader/efi_tcg2.c     | 70 +++++++++++++++++++++++++++++++++++
>   3 files changed, 76 insertions(+)
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 281ffff30f..e9bd1aac08 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -407,6 +407,7 @@ 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);
> +efi_status_t efi_tcg2_notify_exit_boot_services_failed(void);
>   /* Measure efi application invocation */
>   efi_status_t EFIAPI efi_tcg2_measure_efi_app_invocation(void);
>   /* Measure efi application exit */
> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> index 2914800c56..6e07ef65bc 100644
> --- a/lib/efi_loader/efi_boottime.c
> +++ b/lib/efi_loader/efi_boottime.c
> @@ -2181,6 +2181,11 @@ static efi_status_t EFIAPI efi_exit_boot_services(efi_handle_t image_handle,
>   	efi_set_watchdog(0);
>   	WATCHDOG_RESET();
>   out:
> +	if (ret != EFI_SUCCESS) {
> +		if (IS_ENABLED(CONFIG_EFI_TCG2_PROTOCOL))
> +			efi_tcg2_notify_exit_boot_services_failed();
> +	}
> +
>   	return EFI_EXIT(ret);
>   }
>
> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> index 6e903e3cb3..823abd8217 100644
> --- a/lib/efi_loader/efi_tcg2.c
> +++ b/lib/efi_loader/efi_tcg2.c
> @@ -1506,6 +1506,67 @@ efi_status_t EFIAPI efi_tcg2_measure_efi_app_exit(void)
>   	return ret;
>   }
>
> +/**
> + * efi_tcg2_notify_exit_boot_services() - ExitBootService callback
> + *
> + * @event:	callback event
> + * @context:	callback context
> + */
> +static void EFIAPI
> +efi_tcg2_notify_exit_boot_services(struct efi_event *event, void *context)
> +{
> +	efi_status_t ret;
> +	struct udevice *dev;
> +
> +	EFI_ENTRY("%p, %p", event, context);
> +
> +	ret = platform_get_tpm2_device(&dev);
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	ret = tcg2_measure_event(dev, 5, EV_EFI_ACTION,
> +				 strlen(EFI_EXIT_BOOT_SERVICES_INVOCATION),
> +				 (u8 *)EFI_EXIT_BOOT_SERVICES_INVOCATION);
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	ret = tcg2_measure_event(dev, 5, EV_EFI_ACTION,
> +				 strlen(EFI_EXIT_BOOT_SERVICES_SUCCEEDED),
> +				 (u8 *)EFI_EXIT_BOOT_SERVICES_SUCCEEDED);
> +
> +out:
> +	EFI_EXIT(ret);
> +}
> +
> +/**
> + * efi_tcg2_notify_exit_boot_services_failed()
> + *  - notify ExitBootServices() is failed
> + *
> + * Return:	status code
> + */
> +efi_status_t efi_tcg2_notify_exit_boot_services_failed(void)
> +{
> +	struct udevice *dev;
> +	efi_status_t ret;
> +
> +	ret = platform_get_tpm2_device(&dev);
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	ret = tcg2_measure_event(dev, 5, EV_EFI_ACTION,
> +				 sizeof(EFI_EXIT_BOOT_SERVICES_INVOCATION),
> +				 (u8 *)EFI_EXIT_BOOT_SERVICES_INVOCATION);
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
> +	ret = tcg2_measure_event(dev, 5, EV_EFI_ACTION,
> +				 sizeof(EFI_EXIT_BOOT_SERVICES_FAILED),
> +				 (u8 *)EFI_EXIT_BOOT_SERVICES_FAILED);
> +
> +out:
> +	return ret;
> +}

We must keep out code small. Please, carve out a function to which pass
a the event type and an u8 string and use it where applicable.

Best regards

Heinrich

> +
>   /**
>    * tcg2_measure_secure_boot_variable() - measure secure boot variables
>    *
> @@ -1556,6 +1617,7 @@ efi_status_t efi_tcg2_register(void)
>   {
>   	efi_status_t ret = EFI_SUCCESS;
>   	struct udevice *dev;
> +	struct efi_event *event;
>
>   	ret = platform_get_tpm2_device(&dev);
>   	if (ret != EFI_SUCCESS) {
> @@ -1580,6 +1642,14 @@ efi_status_t efi_tcg2_register(void)
>   		goto fail;
>   	}
>
> +	ret = efi_create_event(EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,
> +			       efi_tcg2_notify_exit_boot_services, NULL,
> +			       NULL, &event);
> +	if (ret != EFI_SUCCESS) {
> +		tcg2_uninit();
> +		goto fail;
> +	}
> +
>   	ret = tcg2_measure_secure_boot_variable(dev);
>   	if (ret != EFI_SUCCESS) {
>   		tcg2_uninit();
>