linux-kernel - Re: [PATCH 3/3] tpm: move TPM 1.2 code of tpm_pcr_extend() to tpm1_pcr

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Date:   Wed, 3 May 2017 15:49:29 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     tpmdd-devel@...ts.sourceforge.net,
        linux-ima-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] tpm: move TPM 1.2 code of tpm_pcr_extend() to
 tpm1_pcr_extend()

On Tue, May 02, 2017 at 02:31:51PM +0200, Roberto Sassu wrote:
> In preparation of the modifications to tpm_pcr_extend(), which will
> allow callers to supply a digest for each PCR bank of a TPM 2.0,
> the TPM 1.2 specific code has been moved to tpm1_pcr_extend().
> 
> tpm1_pcr_extend() uses tpm_buf_init() to prepare the command buffer,
> which offers protection against buffer overflow. It is called by
> tpm_pcr_extend() and tpm_pm_suspend().
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

/Jarkko

> ---
>  drivers/char/tpm/tpm-interface.c | 46 +++++++++++++++++++++-------------------
>  1 file changed, 24 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 5c2c032..9059f67 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -763,11 +763,25 @@ EXPORT_SYMBOL_GPL(tpm_pcr_read);
>  
>  #define EXTEND_PCR_RESULT_SIZE 34
>  #define EXTEND_PCR_RESULT_BODY_SIZE 20
> -static const struct tpm_input_header pcrextend_header = {
> -	.tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
> -	.length = cpu_to_be32(34),
> -	.ordinal = cpu_to_be32(TPM_ORD_PCREXTEND)
> -};
> +
> +static int tpm1_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash,
> +			   char *log_msg)
> +{
> +	struct tpm_buf buf;
> +	int rc;
> +
> +	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCREXTEND);
> +	if (rc)
> +		return rc;
> +
> +	tpm_buf_append_u32(&buf, pcr_idx);
> +	tpm_buf_append(&buf, hash, TPM_DIGEST_SIZE);
> +
> +	rc = tpm_transmit_cmd(chip, buf.data, EXTEND_PCR_RESULT_SIZE,
> +			      EXTEND_PCR_RESULT_BODY_SIZE, 0, log_msg);
> +	tpm_buf_destroy(&buf);
> +	return rc;
> +}
>  
>  /**
>   * tpm_pcr_extend - extend pcr value with hash
> @@ -781,7 +795,6 @@ static const struct tpm_input_header pcrextend_header = {
>   */
>  int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
>  {
> -	struct tpm_cmd_t cmd;
>  	int rc;
>  	struct tpm_chip *chip;
>  	struct tpm2_digest digest_list[ARRAY_SIZE(chip->active_banks)];
> @@ -807,13 +820,8 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
>  		return rc;
>  	}
>  
> -	cmd.header.in = pcrextend_header;
> -	cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
> -	memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);
> -	rc = tpm_transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE,
> -			      EXTEND_PCR_RESULT_BODY_SIZE, 0,
> -			      "attempting extend a PCR value");
> -
> +	rc = tpm1_pcr_extend(chip, pcr_idx, hash,
> +			     "attempting extend a PCR value");
>  	tpm_put_ops(chip);
>  	return rc;
>  }
> @@ -1011,15 +1019,9 @@ int tpm_pm_suspend(struct device *dev)
>  	}
>  
>  	/* for buggy tpm, flush pcrs with extend to selected dummy */
> -	if (tpm_suspend_pcr) {
> -		cmd.header.in = pcrextend_header;
> -		cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(tpm_suspend_pcr);
> -		memcpy(cmd.params.pcrextend_in.hash, dummy_hash,
> -		       TPM_DIGEST_SIZE);
> -		rc = tpm_transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE,
> -				     EXTEND_PCR_RESULT_BODY_SIZE, 0,
> -				      "extending dummy pcr before suspend");
> -	}
> +	if (tpm_suspend_pcr)
> +		rc = tpm1_pcr_extend(chip, tpm_suspend_pcr, dummy_hash,
> +				     "extending dummy pcr before suspend");
>  
>  	/* now do the actual savestate */
>  	for (try = 0; try < TPM_RETRY; try++) {
> -- 
> 2.9.3
> 
> --
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