[PATCH v2] efi_loader: Add a locality event on the eventlog

[Ilias Apalodimas]

Responding to myself here, but after re-reading the spec, I realized
this is only required, if the startup locality was set to '3'.
So Heinrich please ignore this for now, I'll repost it once we have a
way to read the startup locality properly

Cheers
/Ilias


On Wed, 24 Mar 2021 at 09:43, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> We are currently not adding any events on the eventlog apart from the
> SpecID event.  The locality event is mandatory and must be logged before
> extending PCR[0].
>
> The spec description is
> "The Startup Locality event should be placed in the log before any event which
> extends PCR[0]. This allows software which needs to parse the TCG Event Log to
> initialize its internal PCR[0] state correctly".
>
> So let's add a locality even during the EventLog creation, right after
> our SpecID event.
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
> changes since v1:
> - v1 was missing the required headers changes
> - exit on tcg2_create_digest() failure
>  include/efi_tcg2.h        | 13 ++++++++++
>  lib/efi_loader/efi_tcg2.c | 52 +++++++++++++++++++++++++++++----------
>  2 files changed, 52 insertions(+), 13 deletions(-)
>
> diff --git a/include/efi_tcg2.h b/include/efi_tcg2.h
> index 40e241ce315c..eac76774d7ff 100644
> --- a/include/efi_tcg2.h
> +++ b/include/efi_tcg2.h
> @@ -72,6 +72,7 @@ struct efi_tcg2_boot_service_capability {
>         offsetof(struct efi_tcg2_boot_service_capability, number_of_pcr_banks)
>
>  #define TCG_EFI_SPEC_ID_EVENT_SIGNATURE_03 "Spec ID Event03"
> +#define TCG_EFI_STARTUP_LOCALITY_SIGNATURE "StartupLocality"
>  #define TCG_EFI_SPEC_ID_EVENT_SPEC_VERSION_MAJOR_TPM2 2
>  #define TCG_EFI_SPEC_ID_EVENT_SPEC_VERSION_MINOR_TPM2 0
>  #define TCG_EFI_SPEC_ID_EVENT_SPEC_VERSION_ERRATA_TPM2 2
> @@ -120,6 +121,18 @@ struct tcg_efi_spec_id_event {
>         u8 vendor_info[];
>  } __packed;
>
> +/**
> + * struct tdTCG_EfiStartupLocalityEvent
> + *
> + * @signature:         The NUL-terminated ASCII string "StartupLocality"
> + * @startup_locality:  The Locality Indicator which sent the TPM2_Startup
> + *                     command
> + */
> +struct tcg_efi_startup_locality_event {
> +       u8 signature[16];
> +       u8 startup_locality;
> +} __packed;
> +
>  /**
>   * struct tdEFI_TCG2_FINAL_EVENTS_TABLE
>   * @version:           version number for this structure
> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> index 797d6eb134f6..31c80b21d8b5 100644
> --- a/lib/efi_loader/efi_tcg2.c
> +++ b/lib/efi_loader/efi_tcg2.c
> @@ -513,7 +513,7 @@ static efi_status_t tcg2_create_digest(const u8 *input, u32 length,
>         sha1_context ctx;
>         sha256_context ctx_256;
>         sha512_context ctx_512;
> -       u8 final[TPM2_ALG_SHA512];
> +       u8 final[TPM2_ALG_SHA512] = { 0 };
>         efi_status_t ret;
>         u32 active;
>         int i;
> @@ -530,27 +530,35 @@ static efi_status_t tcg2_create_digest(const u8 *input, u32 length,
>                         continue;
>                 switch (hash_alg) {
>                 case TPM2_ALG_SHA1:
> -                       sha1_starts(&ctx);
> -                       sha1_update(&ctx, input, length);
> -                       sha1_finish(&ctx, final);
> +                       if (input) {
> +                               sha1_starts(&ctx);
> +                               sha1_update(&ctx, input, length);
> +                               sha1_finish(&ctx, final);
> +                       }
>                         digest_list->count++;
>                         break;
>                 case TPM2_ALG_SHA256:
> -                       sha256_starts(&ctx_256);
> -                       sha256_update(&ctx_256, input, length);
> -                       sha256_finish(&ctx_256, final);
> +                       if (input) {
> +                               sha256_starts(&ctx_256);
> +                               sha256_update(&ctx_256, input, length);
> +                               sha256_finish(&ctx_256, final);
> +                       }
>                         digest_list->count++;
>                         break;
>                 case TPM2_ALG_SHA384:
> -                       sha384_starts(&ctx_512);
> -                       sha384_update(&ctx_512, input, length);
> -                       sha384_finish(&ctx_512, final);
> +                       if (input) {
> +                               sha384_starts(&ctx_512);
> +                               sha384_update(&ctx_512, input, length);
> +                               sha384_finish(&ctx_512, final);
> +                       }
>                         digest_list->count++;
>                         break;
>                 case TPM2_ALG_SHA512:
> -                       sha512_starts(&ctx_512);
> -                       sha512_update(&ctx_512, input, length);
> -                       sha512_finish(&ctx_512, final);
> +                       if (input) {
> +                               sha512_starts(&ctx_512);
> +                               sha512_update(&ctx_512, input, length);
> +                               sha512_finish(&ctx_512, final);
> +                       }
>                         digest_list->count++;
>                         break;
>                 default:
> @@ -1004,6 +1012,8 @@ static efi_status_t efi_init_event_log(void)
>         struct udevice *dev;
>         size_t spec_event_size;
>         efi_status_t ret;
> +       struct tcg_efi_startup_locality_event locality_event;
> +       struct tpml_digest_values digest_list;
>
>         ret = platform_get_tpm2_device(&dev);
>         if (ret != EFI_SUCCESS)
> @@ -1040,6 +1050,22 @@ static efi_status_t efi_init_event_log(void)
>         event_log.pos = spec_event_size + sizeof(*event_header);
>         event_log.last_event_size = event_log.pos;
>
> +       /* Add a locality event before PCR[0] changes */
> +       memcpy(locality_event.signature, TCG_EFI_STARTUP_LOCALITY_SIGNATURE,
> +              sizeof(locality_event.signature));
> +       /*
> +        * Locality 0 is designated as the default Locality. This is usually
> +        * the platform’s boot firmware, OS and applications.
> +        */
> +       locality_event.startup_locality = 0;
> +       ret = tcg2_create_digest(NULL, 0, &digest_list);
> +       if (ret != EFI_SUCCESS)
> +               goto out;
> +       ret = tcg2_agile_log_append(0, EV_NO_ACTION, &digest_list,
> +                                   sizeof(locality_event), (u8*)&locality_event);
> +       if (ret != EFI_SUCCESS)
> +               goto out;
> +
>         ret = create_final_event();
>
>  out:
> --
> 2.31.0
>