[PATCH v4 1/7] tpm: Require a digest source when extending the PCR

[Ilias Apalodimas]

On Tue, 23 Aug 2022 at 20:12, Simon Glass <sjg at chromium.org> wrote:
>
> This feature is used for measured boot, so we can add a log entry to the
> TCPA with some information about where the digest comes from. It is not
> currently supported in the TPM drivers, but add it to the API so that
> code which expects it can signal its request.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
> (no changes since v3)
>
> Changes in v3:
> - Drop limits on the TPM hash size
> - Update commit message
>
> Changes in v2:
> - Use "cmd" for the digest type in the tpm command
> - Update comment for tpm_pcr_extend() 'name' parameter
>
>  cmd/tpm-v1.c      |  3 ++-
>  cmd/tpm_test.c    |  5 +++--
>  include/tpm_api.h |  8 +++++---
>  lib/tpm-v2.c      |  2 ++
>  lib/tpm_api.c     | 10 ++++++----
>  5 files changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/cmd/tpm-v1.c b/cmd/tpm-v1.c
> index bf238a9f2e3..0efb079b0a9 100644
> --- a/cmd/tpm-v1.c
> +++ b/cmd/tpm-v1.c
> @@ -131,7 +131,8 @@ static int do_tpm_extend(struct cmd_tbl *cmdtp, int flag, int argc,
>                 return CMD_RET_FAILURE;
>         }
>
> -       rc = tpm_pcr_extend(dev, index, in_digest, out_digest);
> +       rc = tpm_pcr_extend(dev, index, in_digest, sizeof(in_digest),
> +                           out_digest, "cmd");
>         if (!rc) {
>                 puts("PCR value after execution of the command:\n");
>                 print_byte_string(out_digest, sizeof(out_digest));
> diff --git a/cmd/tpm_test.c b/cmd/tpm_test.c
> index a3ccb12f53a..b35eae81dc3 100644
> --- a/cmd/tpm_test.c
> +++ b/cmd/tpm_test.c
> @@ -91,7 +91,8 @@ static int test_early_extend(struct udevice *dev)
>         tpm_init(dev);
>         TPM_CHECK(tpm_startup(dev, TPM_ST_CLEAR));
>         TPM_CHECK(tpm_continue_self_test(dev));
> -       TPM_CHECK(tpm_pcr_extend(dev, 1, value_in, value_out));
> +       TPM_CHECK(tpm_pcr_extend(dev, 1, value_in, sizeof(value_in), value_out,
> +                                "test"));
>         printf("done\n");
>         return 0;
>  }
> @@ -438,7 +439,7 @@ static int test_timing(struct udevice *dev)
>                    100);
>         TTPM_CHECK(tpm_nv_read_value(dev, INDEX0, (uint8_t *)&x, sizeof(x)),
>                    100);
> -       TTPM_CHECK(tpm_pcr_extend(dev, 0, in, out), 200);
> +       TTPM_CHECK(tpm_pcr_extend(dev, 0, in, sizeof(in), out, "test"), 200);
>         TTPM_CHECK(tpm_set_global_lock(dev), 50);
>         TTPM_CHECK(tpm_tsc_physical_presence(dev, PHYS_PRESENCE), 100);
>         printf("done\n");
> diff --git a/include/tpm_api.h b/include/tpm_api.h
> index 11aa14eb793..8979d9d6df7 100644
> --- a/include/tpm_api.h
> +++ b/include/tpm_api.h
> @@ -81,14 +81,16 @@ u32 tpm_nv_write_value(struct udevice *dev, u32 index, const void *data,
>   *
>   * @param dev          TPM device
>   * @param index                index of the PCR
> - * @param in_digest    160-bit value representing the event to be
> + * @param in_digest    160/256-bit value representing the event to be
>   *                     recorded
> - * @param out_digest   160-bit PCR value after execution of the
> + * @param size         size of digest in bytes
> + * @param out_digest   160/256-bit PCR value after execution of the
>   *                     command
> + * @param name         digest source, used for log output
>   * Return: return code of the operation
>   */
>  u32 tpm_pcr_extend(struct udevice *dev, u32 index, const void *in_digest,
> -                  void *out_digest);
> +                  uint size, void *out_digest, const char *name);
>
>  /**
>   * Issue a TPM_PCRRead command.
> diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
> index 1bf627853af..6058f2e1e4f 100644
> --- a/lib/tpm-v2.c
> +++ b/lib/tpm-v2.c
> @@ -157,6 +157,8 @@ u32 tpm2_pcr_extend(struct udevice *dev, u32 index, u32 algorithm,
>         };
>         int ret;
>
> +       if (!digest)
> +               return -EINVAL;
>         /*
>          * Fill the command structure starting from the first buffer:
>          *     - the digest
> diff --git a/lib/tpm_api.c b/lib/tpm_api.c
> index 032f383ca04..aa4a9fd406c 100644
> --- a/lib/tpm_api.c
> +++ b/lib/tpm_api.c
> @@ -140,15 +140,17 @@ u32 tpm_write_lock(struct udevice *dev, u32 index)
>  }
>
>  u32 tpm_pcr_extend(struct udevice *dev, u32 index, const void *in_digest,
> -                  void *out_digest)
> +                  uint size, void *out_digest, const char *name)
>  {
> -       if (tpm_is_v1(dev))
> +       if (tpm_is_v1(dev)) {
>                 return tpm1_extend(dev, index, in_digest, out_digest);
> -       else if (tpm_is_v2(dev))
> +       } else if (tpm_is_v2(dev)) {
>                 return tpm2_pcr_extend(dev, index, TPM2_ALG_SHA256, in_digest,
>                                        TPM2_DIGEST_LEN);
> -       else
> +               /* @name is ignored as we do not support measured boot */

This is a bit misleading, since with EFI boot, measured boot is
supported.  I can change that while merging, any alternative
suggestions?

> +       } else {
>                 return -ENOSYS;
> +       }
>  }
>
>  u32 tpm_pcr_read(struct udevice *dev, u32 index, void *data, size_t count)
> --
> 2.37.2.609.g9ff673ca1a-goog
>

Reviewed-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>