Re: [PATCH AUTOSEL 5.7 03/30] ima: extend boot_aggregate with kernel measurements

Sasha Levin
2020-07-09T01:27:37Z

On Wed, Jul 08, 2020 at 12:13:13PM -0400, Mimi Zohar wrote:
>Hi Sasha,
>
>On Wed, 2020-07-08 at 11:40 -0400, Sasha Levin wrote:
>> From: Maurizio Drocco <maurizio.drocco@ibm.com>
>>
>> [ Upstream commit 20c59ce010f84300f6c655d32db2610d3433f85c ]
>>
>> Registers 8-9 are used to store measurements of the kernel and its
>> command line (e.g., grub2 bootloader with tpm module enabled). IMA
>> should include them in the boot aggregate. Registers 8-9 should be
>> only included in non-SHA1 digests to avoid ambiguity.
>
>Prior to Linux 5.8, the SHA1 template data hashes were padded before
>being extended into the TPM.  Support for calculating and extending
>the per TPM bank template data digests is only being upstreamed in
>Linux 5.8.
>
>How will attestation servers know whether to include PCRs 8 & 9 in the
>the boot_aggregate calculation?  Now, there is a direct relationship
>between the template data SHA1 padded digest not including PCRs 8 & 9,
>and the new per TPM bank template data digest including them.

Got it, I'll drop it then, thank you!

--
Thanks,
Sasha