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

[Masahisa Kojima]

On Fri, 9 Jul 2021 at 02:40, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> 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.

I'm not sure I understand your comment correctly.
pcr_index is also required for carved out function because pcr_index
to extend PCR is different for each EV_EFI_ACTION event.
So the interface of carved out function is almost same as tcg2_measure_event().

I meant to create tcg2_measure_event() as a common sub-function.
to reduce the number of code.

Thanks,
Masahisa Kojima

>
> 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();
> >
>