linux-kernel - Re: [PATCH v2] ima_evm_utils: extended calc_bootaggr to PCRs 8

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Message-ID: <20200623181357.GC4983@glitch>
Date:   Tue, 23 Jun 2020 15:13:57 -0300
From:   Bruno Meneguele <bmeneg@...hat.com>
To:     Maurizio Drocco <maurizio.drocco@....com>
Cc:     zohar@...ux.ibm.com, Silviu.Vlasceanu@...wei.com,
        dmitry.kasatkin@...il.com, jejb@...ux.ibm.com, jmorris@...ei.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, mdrocco@...ux.vnet.ibm.com,
        roberto.sassu@...wei.com, serge@...lyn.com
Subject: Re: [PATCH v2] ima_evm_utils: extended calc_bootaggr to PCRs 8 - 9

On Tue, Jun 23, 2020 at 02:01:22PM -0400, Maurizio Drocco wrote:
> From: Maurizio <maurizio.drocco@....com>
> 
> If PCRs 8 - 9 are set (i.e. not all-zeros), cal_bootaggr should include
> them into the digest.
> 
> Signed-off-by: Maurizio Drocco <maurizio.drocco@....com>
> ---
> Changelog:
> v2:
> - Always include PCRs 8 & 9 to non-sha1 hashes
> v1:
> - Include non-zero PCRs 8 & 9 to boot aggregates 
> 
>  src/evmctl.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/src/evmctl.c b/src/evmctl.c
> index 1d065ce..46b7092 100644
> --- a/src/evmctl.c
> +++ b/src/evmctl.c
> @@ -1930,6 +1930,16 @@ static void calc_bootaggr(struct tpm_bank_info *bank)
>  		}
>  	}
>  
> +	if (strcmp(bank->algo_name, "sha1") != 0) {
> +		for (i = 8; i < 10; i++) {
> +			err = EVP_DigestUpdate(pctx, bank->pcr[i], bank->digest_size);
> +			if (!err) {
> +				log_err("EVP_DigestUpdate() failed\n");
> +				return;
> +			}
> +		}
> +	}
> +
>  	err = EVP_DigestFinal(pctx, bank->digest, &mdlen);
>  	if (!err) {
>  		log_err("EVP_DigestFinal() failed\n");
> @@ -1972,8 +1982,9 @@ static int append_bootaggr(char *bootaggr, struct tpm_bank_info *tpm_banks)
>  /*
>   * The IMA measurement list boot_aggregate is the link between the preboot
>   * event log and the IMA measurement list.  Read and calculate all the
> - * possible per TPM bank boot_aggregate digests based on the existing
> - * PCRs 0 - 7 to validate against the IMA boot_aggregate record.
> + * possible per TPM bank boot_aggregate digests based on the existing PCRs
> + * 0 - 9 to validate against the IMA boot_aggregate record. If the digest
> + * algorithm is SHA1, only PCRs 0 - 7 are considered to avoid ambiguity.
>   */
>  static int cmd_ima_bootaggr(struct command *cmd)
>  {
> -- 
> 2.17.1
> 

Reviewed-by: Bruno Meneguele <bmeneg@...hat.com>

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