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

[Roberto Sassu <roberto.sassu@xxxxxxxxxx>]

On 9/16/2018 2:37 PM, Jarkko Sakkinen wrote:
> 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@xxxxxxxxxx>
> > ---
> >   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?

Hi Jarkko

sorry, I didn't understand this comment. Did you refer to the code
below (chip->active_banks[0] ...)?


> >   			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.

This code has the same behavior of tpm2_get_pcr_allocation(). If some
banks are not used, set the algorithm of the first unused to
TPM_ALG_ERROR.


> > +
> >   	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?

It derived from chip->active_banks. I will rename the structure.

Thanks

Roberto