On 9/26/2018 8:03 PM, Mimi Zohar wrote:
On Wed, 2018-09-26 at 10:40 -0400, Mimi Zohar wrote:
On Mon, 2018-09-17 at 11:38 +0200, Roberto Sassu wrote:
Resending to maintainer with correct mailing lists in CC.
The TPM driver currently relies on the crypto subsystem to determine the
digest size of supported TPM algorithms. In the future, TPM vendors might
implement new algorithms in their chips, and those algorithms might not
be supported by the crypto subsystem.
Usually, vendors provide patches for the new hardware, and likely
the crypto subsystem will be updated before the new algorithm is
introduced. However, old kernels might be updated later, after patches
are included in the mainline kernel. This would leave the opportunity
for attackers to misuse PCRs, as PCR banks with an unknown algorithm
are not extended.
This patch set provides a long term solution for this issue. If a TPM
algorithm is not known by the crypto subsystem, the TPM driver retrieves
the digest size from the TPM with a PCR read. All the PCR banks are
extended, even if the algorithm is not yet supported by the crypto
subsystem.
Other than checking the digest size before copying the pcrread buffer,
the patches look good. Please add my Ack on all 3 patches.
(New address) Acked-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
I've reviewed, and am currently running with these patches.
Even if the IMA changes were in a separate patch, we wouldn't be able
to break up the patch set anyway. Jarkko, I'd appreciate your
carrying the entire patch set.
Roberto, a similar change needs to be made for tpm_pcr_extend. Are
you planning on posting those changes as well?
Yes, I was planning to send the patch after this patch set is accepted.
Roberto
