Re: [PATCH v2 0/3] tpm: retrieve digest size of unknown algorithms from TPM

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Wed, Sep 05, 2018 at 01:41:59PM +0200, Roberto Sassu wrote:
> 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.

I'm sorry. I missed this before checking through the mails. In future,
please add me either to to-field so that they arrive to my inbox and
do not get filtered to linux-integrity folder, which I go through with
time at most once a week.

/Jarkko