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

[Eric Snowberg]

> On Feb 10, 2023, at 6:05 AM, Mimi Zohar <zohar at linux.ibm.com> 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.

I will include this in the next round too, thanks.