Re: [PATCH v2, RESEND 2/3] tpm: modify tpm_pcr_read() definition to pass TPM hash algorithms

[Jarkko Sakkinen]

On Mon, 2018-09-17 at 11:38 +0200, Roberto Sassu wrote:
> Currently the TPM driver allows other kernel subsystems to read only the
> SHA1 PCR bank. This patch modifies the parameters of tpm_pcr_read() and
> tpm2_pcr_read() to pass an array of tpm_digest structures, which contains
> the desired hash algorithms. Initially, the array size is limited to 1.
> 
> Due to the API change, IMA functions have been modified.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> ---
>  drivers/char/tpm/tpm-interface.c    | 13 +++++++++----
>  drivers/char/tpm/tpm.h              |  3 ++-
>  drivers/char/tpm/tpm2-cmd.c         | 17 +++++++++++------
>  include/linux/tpm.h                 |  6 ++++--
>  security/integrity/ima/ima_crypto.c | 10 +++++-----
>  5 files changed, 31 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-
> interface.c
> index 645c9aa7677a..81872880b5f1 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -976,21 +976,26 @@ EXPORT_SYMBOL_GPL(tpm_is_tpm2);
>   * tpm_pcr_read - read a PCR value from SHA1 bank
>   * @chip:	a &struct tpm_chip instance, %NULL for the default chip
>   * @pcr_idx:	the PCR to be retrieved
> - * @res_buf:	the value of the PCR
> + * @count:	number of digests passed
> + * @digests:	list of pcr banks and buffers current PCR values are
> written to
>   *
>   * Return: same as with tpm_transmit_cmd()
>   */
> -int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
> +int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
> +		 struct tpm_digest *digests)
>  {
>  	int rc;
>  
> +	if (count != 1)
> +		return -EINVAL;
> +
>  	chip = tpm_find_get_ops(chip);
>  	if (!chip)
>  		return -ENODEV;
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> -		rc = tpm2_pcr_read(chip, pcr_idx, res_buf);
> +		rc = tpm2_pcr_read(chip, pcr_idx, count, digests);
>  	else
> -		rc = tpm_pcr_read_dev(chip, pcr_idx, res_buf);
> +		rc = tpm_pcr_read_dev(chip, pcr_idx, digests[0].digest);
>  	tpm_put_ops(chip);
>  	return rc;
>  }
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index b928ba44d864..9479e1ae1b4c 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -564,7 +564,8 @@ static inline u32 tpm2_rc_value(u32 rc)
>  	return (rc & BIT(7)) ? rc & 0xff : rc;
>  }
>  
> -int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
> +int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
> +		  struct tpm_digest *digests);
>  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 2d7397b8a0d1..601d67c76c1e 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -179,11 +179,13 @@ struct tpm2_pcr_read_out {
>   * tpm2_pcr_read() - read a PCR value
>   * @chip:	TPM chip to use.
>   * @pcr_idx:	index of the PCR to read.
> - * @res_buf:	buffer to store the resulting hash.
> + * @count:	number of digests passed.
> + * @digests:	list of pcr banks and buffers current PCR values are
> written to.
>   *
>   * Return: Same as with tpm_transmit_cmd.
>   */
> -int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
> +int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
> +		  struct tpm_digest *digests)
>  {
>  	int rc;
>  	struct tpm_buf buf;
> @@ -192,6 +194,8 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8
> *res_buf)
>  
>  	if (pcr_idx >= TPM2_PLATFORM_PCR)
>  		return -EINVAL;
> +	if (count > 1)
> +		return -EINVAL;
>  
>  	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
>  	if (rc)
> @@ -200,16 +204,17 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8
> *res_buf)
>  	pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7);
>  
>  	tpm_buf_append_u32(&buf, 1);
> -	tpm_buf_append_u16(&buf, TPM_ALG_SHA1);
> +	tpm_buf_append_u16(&buf, count ? digests[0].alg_id : TPM_ALG_SHA1);
>  	tpm_buf_append_u8(&buf, TPM2_PCR_SELECT_MIN);
>  	tpm_buf_append(&buf, (const unsigned char *)pcr_select,
>  		       sizeof(pcr_select));
>  
>  	rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0,
> -			res_buf ? "attempting to read a pcr value" : NULL);
> -	if (rc == 0 && res_buf) {
> +			      count ? "attempting to read a pcr value" :
> NULL);
> +	if (rc == 0 && count) {
>  		out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
> -		memcpy(res_buf, out->digest, SHA1_DIGEST_SIZE);
> +		memcpy(digests[0].digest, out->digest,
> +		       be16_to_cpu(out->digest_size));
>  	}
>  
>  	tpm_buf_destroy(&buf);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 71d7bbf5f690..ac9fc47f4494 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -71,7 +71,8 @@ struct tpm_class_ops {
>  #if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
>  
>  extern int tpm_is_tpm2(struct tpm_chip *chip);
> -extern int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
> +extern int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
> +			struct tpm_digest *digests);
>  extern int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8
> *hash);
>  extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen);
>  extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
> @@ -87,7 +88,8 @@ static inline int tpm_is_tpm2(struct tpm_chip *chip)
>  {
>  	return -ENODEV;
>  }
> -static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8
> *res_buf)
> +static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
> +			       struct tpm_digest *digests)
>  {
>  	return -ENODEV;
>  }
> diff --git a/security/integrity/ima/ima_crypto.c
> b/security/integrity/ima/ima_crypto.c
> index 7e7e7e7c250a..4c94cf810d15 100644
> --- a/security/integrity/ima/ima_crypto.c
> +++ b/security/integrity/ima/ima_crypto.c
> @@ -629,12 +629,12 @@ int ima_calc_buffer_hash(const void *buf, loff_t len,
>  	return calc_buffer_shash(buf, len, hash);
>  }
>  
> -static void __init ima_pcrread(int idx, u8 *pcr)
> +static void __init ima_pcrread(int idx, struct tpm_digest *d)
>  {
>  	if (!ima_tpm_chip)
>  		return;
>  
> -	if (tpm_pcr_read(ima_tpm_chip, idx, pcr) != 0)
> +	if (tpm_pcr_read(ima_tpm_chip, idx, 1, d) != 0)
>  		pr_err("Error Communicating to TPM chip\n");
>  }
>  
> @@ -644,7 +644,7 @@ static void __init ima_pcrread(int idx, u8 *pcr)
>  static int __init ima_calc_boot_aggregate_tfm(char *digest,
>  					      struct crypto_shash *tfm)
>  {
> -	u8 pcr_i[TPM_DIGEST_SIZE];
> +	struct tpm_digest d = {.alg_id = TPM_ALG_SHA1};
>  	int rc, i;
>  	SHASH_DESC_ON_STACK(shash, tfm);
>  
> @@ -657,9 +657,9 @@ static int __init ima_calc_boot_aggregate_tfm(char
> *digest,
>  
>  	/* cumulative sha1 over tpm registers 0-7 */
>  	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
> -		ima_pcrread(i, pcr_i);
> +		ima_pcrread(i, &d);
>  		/* now accumulate with current aggregate */
> -		rc = crypto_shash_update(shash, pcr_i, TPM_DIGEST_SIZE);
> +		rc = crypto_shash_update(shash, d.digest, TPM_DIGEST_SIZE);
>  	}
>  	if (!rc)
>  		crypto_shash_final(shash, digest);

The change would be good if there was a patch in the series that would
use arrays larger than one. The principle is that something added only
at the point when it is taken use of. You should remove @count for now.

/Jarkko