linux-kernel - RE: [PATCH 6/8] ima: calculate and extend PCR with digests in ima_template

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Date:   Mon, 27 Jan 2020 17:29:35 +0000
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     "zohar@...ux.ibm.com" <zohar@...ux.ibm.com>,
        "jarkko.sakkinen@...ux.intel.com" <jarkko.sakkinen@...ux.intel.com>,
        "james.bottomley@...senpartnership.com" 
        <james.bottomley@...senpartnership.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>
CC:     "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Silviu Vlasceanu <Silviu.Vlasceanu@...wei.com>
Subject: RE: [PATCH 6/8] ima: calculate and extend PCR with digests in
 ima_template_entry

> -----Original Message-----
> From: Roberto Sassu
> Sent: Monday, January 27, 2020 6:05 PM
> To: zohar@...ux.ibm.com; jarkko.sakkinen@...ux.intel.com;
> james.bottomley@...senpartnership.com; linux-integrity@...r.kernel.org
> Cc: linux-security-module@...r.kernel.org; linux-kernel@...r.kernel.org;
> Silviu Vlasceanu <Silviu.Vlasceanu@...wei.com>; Roberto Sassu
> <roberto.sassu@...wei.com>
> Subject: [PATCH 6/8] ima: calculate and extend PCR with digests in
> ima_template_entry
> 
> This patch modifies ima_calc_field_array_hash() to calculate a template
> digest for each allocated PCR bank and SHA1. It also passes the tpm_digest
> array of the template entry to ima_pcr_extend() or in case of a violation,
> the pre-initialized digests array filled with 0xff.
> 
> Padding with zeros is still done if the mapping between TPM algorithm ID
> and crypto ID is unknown.
> 
> This patch calculates again the template digest when a measurement list is
> restored. Copying only the SHA1 digest (due to the limitation of the
> current measurement list format) is not sufficient, as hash collision
> detection will be done on the digest calculated with the default IMA hash
> algorithm.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
>  security/integrity/ima/ima_crypto.c   | 26 ++++++++++++++++++++++-
>  security/integrity/ima/ima_queue.c    | 30 ++++++++++++++++-----------
>  security/integrity/ima/ima_template.c | 14 +++++++++++--
>  3 files changed, 55 insertions(+), 15 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_crypto.c
> b/security/integrity/ima/ima_crypto.c
> index 63fb4bdf80b0..786340feebbb 100644
> --- a/security/integrity/ima/ima_crypto.c
> +++ b/security/integrity/ima/ima_crypto.c
> @@ -610,9 +610,33 @@ static int ima_calc_field_array_hash_tfm(struct
> ima_field_data *field_data,
>  int ima_calc_field_array_hash(struct ima_field_data *field_data,
>  			      struct ima_template_entry *entry)
>  {
> -	int rc;
> +	u16 alg_id;
> +	int rc, i;
> 
>  	rc = ima_calc_field_array_hash_tfm(field_data, entry,
> ima_sha1_idx);
> +	if (rc)
> +		return rc;
> +
> +	entry->digests[ima_sha1_idx].alg_id = TPM_ALG_SHA1;
> +
> +	for (i = 0; i < ima_tpm_chip->nr_allocated_banks + 1; i++) {
> +		if (i == ima_sha1_idx)
> +			continue;
> +
> +		alg_id = ima_tpm_chip->allocated_banks[i].alg_id;

The line above should be executed for i < ima_tpm_chip->nr_allocated_banks.

I will fix in the next version of the patch set.

Roberto

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