Re: [RFC][PATCH] ima: add crypto agility support for template-hash algorithm

Mimi Zohar
2023-12-19T20:54:17Z

Hi Enrico,

On Thu, 2023-12-14 at 15:51 +0100, Enrico Bravi wrote:
> The purpose of this patch is to add the possibility to configure the hash
> algorithm to use when calculating the template-hash.

The patch description should be written in the imperative mood. For an
explanation, please refer to "Describe your changes" in
Documentation/process/submitting-patches.rst.

For example:

The second field of the IMA measurement list, the template data hash,
contains a fixed sized SHA1 digest. Add support to replace the SHA1
digest with other hash algorithms. For backwards compatability, only
the new larger digests will be prefixed with ...

> The ima_template_hash command line parameter has been introduced to enable
> this configuration.

The term "ima_template_hash" could be misconstrued to refer to the hash
algorithm used to calculate the file digest. To differentiate between
the hash algorithm used to calculate the file digest, the term
'ima_template_data_hash' is longer, but I think clearer.

> The entry will contain the hash_algo_name before the actual template-hash,
> separated by a colon (:).

This chnage will break existing userspace applications, unless the SHA1
digest isn't prefixed.

> An example of the resulting ima log is the following:
>
> 10 sha256:64326[...]25313 ima-ng sha1:5fc9b[...]974e6 boot_aggregate
> 10 sha256:afd64[...]e3123 ima-ng sha1:5a493[...]f9566 /init
> 10 sha256:99329[...]a6353 ima-ng sha1:8c87d[...]3d8c7 /usr/bin/sh
> 10 sha256:a16ad[...]2ac0e ima-ng sha1:59d4b[...]330b0 /etc/ld.so.cache
>
> This patch has been created starting from the master branch of the main tree:
> <git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git>

With the base-commit included at the end of the cover letter, this
comment is unnessary. Please remove.

thanks,

Mimi

>
> Signed-off-by: Silvia Sisinni <silvia.sisinni@polito.it>
> Signed-off-by: Enrico Bravi <enrico.bravi@polito.it>