Re: [PATCH 0/3] KEXEC_SIG with appended signature

Nayna
2021-11-11T22:24:00Z

On 11/5/21 09:14, Michal Suchánek wrote:
> On Fri, Nov 05, 2021 at 09:55:52PM +1100, Daniel Axtens wrote:
>> Michal Suchanek <msuchanek@suse.de> writes:
>>
>>> S390 uses appended signature for kernel but implements the check
>>> separately from module loader.
>>>
>>> Support for secure boot on powerpc with appended signature is planned -
>>> grub patches submitted upstream but not yet merged.
>> Power Non-Virtualised / OpenPower already supports secure boot via kexec
>> with signature verification via IMA. I think you have now sent a
>> follow-up series that merges some of the IMA implementation, I just
>> wanted to make sure it was clear that we actually already have support
> So is IMA_KEXEC and KEXEC_SIG redundant?
>
> I see some architectures have both. I also see there is a lot of overlap
> between the IMA framework and the KEXEC_SIG and MODULE_SIg.

Originally, KEXEC_SIG was meant for PECOFF based signatures, while
IMA_KEXEC mainly supported xattr based signatures.

Power (Non-virtualized/OpenPOWER) doesn't support PECOFF. Extended
attributes based signature verification doesn't work with netboot.
That's when appended signature support was added to IMA.

Using IMA_KEXEC has the benefit of being able to enable both signature
verification and measurement of the kernel image.

Thanks & Regards,

- Nayna