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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
	Mimi Zohar <zohar@linux.ibm.com>,
	linux-integrity@vger.kernel.org
Subject: Re: ima_tpm_chip is queried and saved only at IMA init, but never later
Date: Tue, 24 Sep 2019 18:37:04 -0400	[thread overview]
Message-ID: <1569364624.5364.23.camel@HansenPartnership.com> (raw)
In-Reply-To: <d9c28fc6-bd5e-95ae-6386-84e87125c41d@linux.microsoft.com>

On Tue, 2019-09-24 at 15:31 -0700, Lakshmi Ramasubramanian wrote:
[...]
> In one configuration I am testing, I see the TPM appear post IMA
> Init. Likely this is rare, but I was wondering if there was a reason
> why TPM  information is only queried during IMA init, but never
> updated at a later point.

IMA involves a chain of custody attested through the TPM.  If the TPM
isn't present on IMA init then that custody chain is broken and the
measurements can't be relied upon.  For this reason to use the TPM, it
must be present when IMA is initialized ... so the drivers all need
building in to the kernel.

There has been some discussion that we could, for UEFI systems, use the
UEFI runtime drivers for the TPM until the actual driver is inserted
but no-one's looked into doing that.

James


  reply	other threads:[~2019-09-24 22:37 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-24 22:31 ima_tpm_chip is queried and saved only at IMA init, but never later Lakshmi Ramasubramanian
2019-09-24 22:37 ` James Bottomley [this message]
2019-10-03 15:40   ` Lakshmi Ramasubramanian
2019-10-03 15:49     ` Mimi Zohar
2019-10-04  0:39       ` Lakshmi Ramasubramanian
2019-10-03 15:58     ` James Bottomley

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