[PATCH] lsm: drop LSM_ID_IMA

[Roberto Sassu]

On 10/23/2023 5:48 PM, Casey Schaufler wrote:
> On 10/23/2023 8:20 AM, Roberto Sassu wrote:
>> On 10/20/2023 11:56 PM, Casey Schaufler wrote:
>>> On 10/19/2023 1:08 AM, Roberto Sassu wrote:
>>>> On Wed, 2023-10-18 at 17:50 -0400, Paul Moore wrote:
>>>>> When IMA becomes a proper LSM we will reintroduce an appropriate
>>>>> LSM ID, but drop it from the userspace API for now in an effort
>>>>> to put an end to debates around the naming of the LSM ID macro.
>>>>>
>>>>> Signed-off-by: Paul Moore <paul at paul-moore.com>
>>>> Reviewed-by: Roberto Sassu <roberto.sassu at huawei.com>
>>>>
>>>> This makes sense according to the new goal of making 'ima' and 'evm' as
>>>> standalone LSMs.
>>>>
>>>> Otherwise, if we took existing LSMs, we should have defined
>>>> LSM_ID_INTEGRITY, associated to DEFINE_LSM(integrity).
>>>>
>>>> If we proceed with the new direction, I will add the new LSM IDs as
>>>> soon as IMA and EVM become LSMs.
>>>
>>> This seems right to me. Thank You.
>>
>> Perfect! Is it fine to assign an LSM ID to 'ima' and 'evm' and keep
>> the 'integrity' LSM to reserve space in the security blob without LSM
>> ID (as long as it does not register any hook)?
> 
> That will work, although it makes me wonder if all the data in the 'integrity' blob
> is used by both IMA and EVM. If these are going to be separate LSMs they should probably
> have their own security blobs. If there is data in common then an 'integrity' blob can
> still makes sense.

Question, it might be better to ensure that 'evm' is after 'ima' like 
when function calls were hardcoded.

I'm enforcing 'ima' and 'evm' to be the last.

In this case, since we have:

         /* LSM_ORDER_LAST is always last. */
         for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
                 if (lsm->order == LSM_ORDER_LAST)
                         append_ordered_lsm(lsm, "   last");
         }

and:

obj-$(CONFIG_IMA)                       += ima/
obj-$(CONFIG_EVM)                       += evm/

in the integrity Makefile, can I assume that the order will always be 
'ima', 'evm'?

I tried to invert obj-, and indeed the order is inverted. They are not 
mutable LSMs, their order should not depend on the kernel command line. 
Right?

Thanks

Roberto