linux-kernel - Re: [PATCH v2 5/8] ima: Switch to dynamically allocated buffer for template digests

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Date:   Thu, 06 Feb 2020 11:08:04 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>,
        James.Bottomley@...senPartnership.com,
        jarkko.sakkinen@...ux.intel.com
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, silviu.vlasceanu@...wei.com
Subject: Re: [PATCH v2 5/8] ima: Switch to dynamically allocated buffer for
 template digests

Hi Roberto,

On Wed, 2020-02-05 at 11:33 +0100, Roberto Sassu wrote:
> This patch dynamically allocates the array of tpm_digest structures in
> ima_alloc_init_template() and ima_restore_template_data(). The size of the
> array, stored in ima_num_template_digests, is initially equal to 1 (SHA1)
> and will be determined in the upcoming patches depending on the allocated
> PCR banks and the chosen default IMA algorithm.
> 
> Calculating the SHA1 digest is mandatory, as SHA1 still remains the default
> hash algorithm for the measurement list. When IMA will support the Crypto
> Agile format, remaining digests will be also provided.
> 
> The position in the array of the SHA1 digest is stored in the ima_sha1_idx
> global variable and it is determined at IMA initialization time.
> 
> Changelog
> 
> v1:
> - move ima_sha1_idx to ima_crypto.c
> - introduce ima_num_template_digests (suggested by Mimi)

Instead of hardcoding "nr_allocated_banks + 1" or nr_allocated_banks +
2", I suggested defining "nr_allocated_banks + extra", where "extra"
could be 0, 1, or 2.

The rest of the code would remain exactly the same as you had.

Mimi