Hi And apologies for late review. On Mon, Sep 25, 2017 at 01:19:47PM +0200, Roberto Sassu wrote: > This patch set derives from a larger patch set which modifies the TPM > driver API in order to extend a PCR with multiple digests. It can be > retrieved at the URL: > > https://sourceforge.net/p/tpmdd/mailman/message/35905412/ A patch set should be able to live on its own. Please remove this link. I don't care about that patch set at this point and I'm not going to give any distant promises. > 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. This part makes sense to me. /Jarkko
