> 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.
>> Plus this flag can be set for keys loaded into the secondary trusted
>> keyring (6th patch in the series). When an intermediate CA gets loaded into the
>> secondary, the flag is set as well.
>
> Please include a full explanation with the motivation in the patch
> description as to why support for intermediary CAs is required for the
> "end-user" use case.
Ok, I can add it. I thought this was an expectation, based on the help section of
IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY:
" Intermediate keys between those the kernel has compiled in and the
IMA keys to be added may be added to the system secondary keyring,
provided they are validly signed by a key already resident in the
built-in or secondary trusted keyrings."
