Re: [PATCH v2 3/3] tpm: retrieve digest size of unknown algorithms with PCR read

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Wed, Sep 05, 2018 at 01:42:02PM +0200, Roberto Sassu wrote:
> Currently, the TPM driver retrieves the digest size from a table mapping
> TPM algorithms identifiers to identifiers defined by the crypto subsystem.
> If the algorithm is not defined by the latter, the digest size can be
> retrieved from the output of the PCR read command.
> 
> The patch retrieves at TPM startup the digest sizes for each PCR bank and
> stores them in the new structure tpm_active_bank_info, member of tpm_chip,
> so that the information can be passed to other kernel subsystems.
> 
> tpm_active_bank_info contains: the TPM algorithm identifier, necessary to
> generate the event log as defined by Trusted Computing Group (TCG); the
> digest size, to pad/truncate a digest calculated with a different
> algorithm; the crypto subsystem identifier, to calculate the digest of
> event data.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>  drivers/char/tpm/tpm-interface.c | 11 +++++++---
>  drivers/char/tpm/tpm.h           |  4 ++--
>  drivers/char/tpm/tpm2-cmd.c      | 47 ++++++++++++++++++++++++++++++----------
>  include/linux/tpm.h              |  6 +++++
>  4 files changed, 51 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 81872880b5f1..02dcdcda5a3c 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -993,7 +993,7 @@ int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
>  	if (!chip)
>  		return -ENODEV;
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> -		rc = tpm2_pcr_read(chip, pcr_idx, count, digests);
> +		rc = tpm2_pcr_read(chip, pcr_idx, count, digests, NULL);
>  	else
>  		rc = tpm_pcr_read_dev(chip, pcr_idx, digests[0].digest);
>  	tpm_put_ops(chip);
> @@ -1056,8 +1056,8 @@ int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
>  		memset(digest_list, 0, sizeof(digest_list));
>  
>  		for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
> -			    chip->active_banks[i] != TPM_ALG_ERROR; i++) {
> -			digest_list[i].alg_id = chip->active_banks[i];
> +		     chip->active_banks[i].alg_id != TPM_ALG_ERROR; i++) {
> +			digest_list[i].alg_id = chip->active_banks[i].alg_id;

Why not just zero?

>  			memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
>  			count++;
>  		}
> @@ -1158,6 +1158,11 @@ int tpm1_auto_startup(struct tpm_chip *chip)
>  		goto out;
>  	}
>  
> +	chip->active_banks[0].alg_id = TPM_ALG_SHA1;
> +	chip->active_banks[0].digest_size = hash_digest_size[HASH_ALGO_SHA1];
> +	chip->active_banks[0].crypto_id = HASH_ALGO_SHA1;
> +	chip->active_banks[1].alg_id = TPM_ALG_ERROR;

Then you could drop the last line here.

> +
>  	return rc;
>  out:
>  	if (rc > 0)
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 9479e1ae1b4c..385843b49c17 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -237,7 +237,7 @@ struct tpm_chip {
>  	const struct attribute_group *groups[3];
>  	unsigned int groups_cnt;
>  
> -	u16 active_banks[7];
> +	struct tpm_active_bank_info active_banks[7];
>  #ifdef CONFIG_ACPI
>  	acpi_handle acpi_dev_handle;
>  	char ppi_version[TPM_PPI_VERSION_LEN + 1];
> @@ -565,7 +565,7 @@ static inline u32 tpm2_rc_value(u32 rc)
>  }
>  
>  int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
> -		  struct tpm_digest *digests);
> +		  struct tpm_digest *digests, u16 *sizes);
>  int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>  		    struct tpm_digest *digests);
>  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 601d67c76c1e..51d2454c5329 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -181,11 +181,12 @@ struct tpm2_pcr_read_out {
>   * @pcr_idx:	index of the PCR to read.
>   * @count:	number of digests passed.
>   * @digests:	list of pcr banks and buffers current PCR values are written to.
> + * @sizes:	list of digest sizes.
>   *
>   * Return: Same as with tpm_transmit_cmd.
>   */
>  int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
> -		  struct tpm_digest *digests)
> +		  struct tpm_digest *digests, u16 *sizes)
>  {
>  	int rc;
>  	struct tpm_buf buf;
> @@ -215,6 +216,9 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
>  		out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
>  		memcpy(digests[0].digest, out->digest,
>  		       be16_to_cpu(out->digest_size));
> +
> +		if (sizes)
> +			sizes[0] = be16_to_cpu(out->digest_size);
>  	}
>  
>  	tpm_buf_destroy(&buf);
> @@ -245,7 +249,6 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>  	struct tpm2_null_auth_area auth_area;
>  	int rc;
>  	int i;
> -	int j;
>  
>  	if (count > ARRAY_SIZE(chip->active_banks))
>  		return -EINVAL;
> @@ -267,14 +270,9 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>  	tpm_buf_append_u32(&buf, count);
>  
>  	for (i = 0; i < count; i++) {
> -		for (j = 0; j < ARRAY_SIZE(tpm2_hash_map); j++) {
> -			if (digests[i].alg_id != tpm2_hash_map[j].tpm_id)
> -				continue;
> -			tpm_buf_append_u16(&buf, digests[i].alg_id);
> -			tpm_buf_append(&buf, (const unsigned char
> -					      *)&digests[i].digest,
> -			       hash_digest_size[tpm2_hash_map[j].crypto_id]);
> -		}
> +		tpm_buf_append_u16(&buf, digests[i].alg_id);
> +		tpm_buf_append(&buf, (const unsigned char *)&digests[i].digest,
> +			       chip->active_banks[i].digest_size);
>  	}
>  
>  	rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0,
> @@ -851,6 +849,26 @@ int tpm2_probe(struct tpm_chip *chip)
>  }
>  EXPORT_SYMBOL_GPL(tpm2_probe);
>  
> +static int tpm2_init_active_bank_info(struct tpm_chip *chip,
> +				      struct tpm_active_bank_info *active_bank)
> +{
> +	struct tpm_digest digest = {.alg_id = active_bank->alg_id};
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
> +		enum hash_algo crypto_algo = tpm2_hash_map[i].crypto_id;
> +
> +		if (active_bank->alg_id != tpm2_hash_map[i].tpm_id)
> +			continue;
> +
> +		active_bank->digest_size = hash_digest_size[crypto_algo];
> +		active_bank->crypto_id = crypto_algo;
> +		return 0;
> +	}
> +
> +	return tpm2_pcr_read(chip, 0, 1, &digest, &active_bank->digest_size);
> +}
> +
>  struct tpm2_pcr_selection {
>  	__be16  hash_alg;
>  	u8  size_of_select;
> @@ -905,7 +923,12 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  		}
>  
>  		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
> -		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
> +		chip->active_banks[i].alg_id =
> +			be16_to_cpu(pcr_selection.hash_alg);
> +		rc =  tpm2_init_active_bank_info(chip, &chip->active_banks[i]);
> +		if (rc)
> +			break;
> +
>  		sizeof_pcr_selection = sizeof(pcr_selection.hash_alg) +
>  			sizeof(pcr_selection.size_of_select) +
>  			pcr_selection.size_of_select;
> @@ -914,7 +937,7 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  
>  out:
>  	if (i < ARRAY_SIZE(chip->active_banks))
> -		chip->active_banks[i] = TPM_ALG_ERROR;
> +		chip->active_banks[i].alg_id = TPM_ALG_ERROR;
>  
>  	tpm_buf_destroy(&buf);
>  
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index ac9fc47f4494..c8372ff582c3 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -46,6 +46,12 @@ struct tpm_digest {
>  	u8 digest[SHA512_DIGEST_SIZE];
>  } __packed;
>  
> +struct tpm_active_bank_info {
> +	u16 alg_id;
> +	u16 digest_size;
> +	u16 crypto_id;
> +};

Why not just tpm_bank_info? Will there be also tpm_inactive_bank_info
at some point?

> +
>  enum TPM_OPS_FLAGS {
>  	TPM_OPS_AUTO_STARTUP = BIT(0),
>  };
> -- 
> 2.14.1
> 

/Jarkko