RE: [PATCH 6/8] ima: calculate and extend PCR with digests in ima_template_entry

Roberto Sassu
2020-01-27T17:29:39Z

> -----Original Message-----
> From: Roberto Sassu
> Sent: Monday, January 27, 2020 6:05 PM
> To: zohar@linux.ibm.com; jarkko.sakkinen@linux.intel.com;
> james.bottomley@hansenpartnership.com; linux-integrity@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org; linux-kernel@vger.kernel.org;
> Silviu Vlasceanu <Silviu.Vlasceanu@huawei.com>; Roberto Sassu
> <roberto.sassu@huawei.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@huawei.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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