On Fri, 2022-04-08 at 21:59 +0000, Eric Snowberg wrote:
> > On Apr 8, 2022, at 12:49 PM, Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote:
> >
> > On Fri, 2022-04-08 at 17:34 +0000, Eric Snowberg wrote:
> >>
> >>> On Apr 8, 2022, at 10:55 AM, Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote:
> >>>
> >>> On Fri, 2022-04-08 at 15:27 +0000, Eric Snowberg wrote:
> >>>>
> >>>>> On Apr 8, 2022, at 8:40 AM, Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote:
> >>>>>
> >>>>> On Tue, 2022-04-05 at 21:53 -0400, Eric Snowberg wrote:
> >>>>>>
> >>>>>> The first type of key to use this is X.509. When a X.509 certificate
> >>>>>> is self signed, has the kernCertSign Key Usage set and contains the
> >>>>>> CA bit set this new flag is set.
> >>>>>>
> >>>>>> Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
> >>>>>>
> >>>>>> diff --git a/include/linux/key.h b/include/linux/key.h
> >>>>>> index 7febc4881363..97f6a1f86a27 100644
> >>>>>> --- a/include/linux/key.h
> >>>>>> +++ b/include/linux/key.h
> >>>>>> @@ -230,6 +230,7 @@ struct key {
> >>>>>> #define KEY_FLAG_ROOT_CAN_INVAL 7 /* set if key can be invalidated by root without permission */
> >>>>>> #define KEY_FLAG_KEEP 8 /* set if key should not be removed */
> >>>>>> #define KEY_FLAG_UID_KEYRING 9 /* set if key is a user or user session keyring */
> >>>>>> +#define KEY_FLAG_BUILTIN_ROT 10 /* set if key is a builtin Root of Trust key */
> >>>>>>
> >>>>>> /* the key type and key description string
> >>>>>> * - the desc is used to match a key against search criteria
> >>>>>> @@ -290,6 +291,7 @@ extern struct key *key_alloc(struct key_type *type,
> >>>>>> #define KEY_ALLOC_BYPASS_RESTRICTION 0x0008 /* Override the check on restricted keyrings */
> >>>>>> #define KEY_ALLOC_UID_KEYRING 0x0010 /* allocating a user or user session keyring */
> >>>>>> #define KEY_ALLOC_SET_KEEP 0x0020 /* Set the KEEP flag on the key/keyring */
> >>>>>> +#define KEY_ALLOC_BUILT_IN_ROT 0x0040 /* Add builtin root of trust key */
> >>>>>
> >>>>> Since the concept of root of trust is not generic, but limited to
> >>>>> specific keyrings, the root CA certificate signing keys on the
> >>>>> "machine" keyring need to be identified. Similar to the
> >>>>> KEY_ALLOC_BUILT_IN/KEY_FLAG_BUILTIN, new flags
> >>>>> KEY_ALLOC_MACHINE/KEY_FLAG_MACHINE should be defined instead.
> >>>>
> >>>> I’m open to renaming these, however this name change seems confusing to me.
> >>>> This flag gets set when the X.509 certificate contains the three CA requirements
> >>>> identified above. The remaining keys in the machine keyring can be used for
> >>>> anything else.
> >>>
> >>> Renaming the flag to KEY_ALLOC_MACHINE/KEY_FLAG_MACHINE differentiates
> >>> between the "builtin" keys from the "machine" keys. The trust models
> >>> are very different.
> >>
> >> Isn’t the trust model the same for machine and secondary keys? Both are supplied by
> >> the end-user. That is why I’m confused by naming something _MACHINE when it applies
> >> to more than one keyring.
> >
> > True both are supplied by the end-user, but the trust models are
> > different.
>
> I think I need more information here, I’m not seeing how they are different trust
> models.
In order to discuss trust models, we need to understand the different
use-cases that are being discussed here without ever having been
explicitly stated. Here are a few:
- Allow users to sign their own kernel modules.
- Allow users to selectively authorize 3rd party certificates to verify
kernel modules.
- From an IMA perspective, allow users to sign files within their own
software packages.
Each of the above use-cases needs to be independently configurable,
thoroughly explained, and enforced.
thanks,
Mimi
>
> > In one case the certificates are coming indirectly from
> > firmware,
