[PATCH v2 1/7] tpm: Require a digest source when extending the PCR

[Heinrich Schuchardt]

On 8/13/22 21:56, Simon Glass 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>
> ---
>
> Changes in v2:
> - Drop limits on the TPM hash size
> - Update commit message
>
>   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..0869b707757 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, "test");

The value "test" seems inadequate in this context. Should this be a
command line argument? Or how about "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"));

Here the string "test" is adequate.

>   	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..3c8e48bc255 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		additional info about where the digest comes from

This does not indicate the usage and if the argument will be stored on
the TPM. I would prefer:

"digest source used for log output"

Best regards

Heinrich

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