[PATCH v4 6/6] integrity: machine keyring CA configuration

[Eric Snowberg]

> On Feb 13, 2023, at 12:54 AM, Jarkko Sakkinen <jarkko at kernel.org> wrote:
> 
> On Fri, Feb 10, 2023 at 08:05:22AM -0500, Mimi Zohar wrote:
>> Hi Eric,
>> 
>> On Mon, 2023-02-06 at 21:59 -0500, Eric Snowberg wrote:
>>> Add a machine keyring CA restriction menu option to control the type of
>>> keys that may be added to it. The options include none, min and max
>>> restrictions.
>>> 
>>> When no restrictions are selected, all Machine Owner Keys (MOK) are added
>>> to the machine keyring.  When CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MIN is
>>> selected, the CA bit must be true.  Also the key usage must contain
>>> keyCertSign, any other usage field may be set as well.
>>> 
>>> When CONFIG_INTEGRITY_CA_MACHINE_KEYRING_MAX is selected, the CA bit must
>>> be true. Also the key usage must contain keyCertSign and the
>>> digitialSignature usage may not be set.
>>> 
>>> Signed-off-by: Eric Snowberg <eric.snowberg at oracle.com>
>> 
>> Missing from the patch description is the motivation for this change.  
>> The choices none, min, max implies a progression, which is good, and
>> the technical differences between the choices, but not the reason.
>> 
>> The motivation, at least from my perspective, is separation of
>> certificate signing from code signing keys, where "none" is no
>> separation and "max" being total separation of keys based on usage.
>> 
>> Subsequent work, as discussed in the cover letter thread, will limit
>> certificates being loaded onto the IMA keyring to code signing keys
>> used for signature verification.
> 
> 
> It would be more robust just to have two binary options for CA bit and
> keyCertSign. You can use "select" for setting keyCertSign, when CA bit
> option is selected.

Ok, I will make that change in the next round, thanks.