From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga18.intel.com ([134.134.136.126]:56251 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726603AbeIJXic (ORCPT ); Mon, 10 Sep 2018 19:38:32 -0400 Date: Mon, 10 Sep 2018 21:42:44 +0300 From: Jarkko Sakkinen To: Roberto Sassu Cc: linux-integrity@vger.kernel.org Subject: Re: [PATCH v2 0/3] tpm: retrieve digest size of unknown algorithms from TPM Message-ID: <20180910184244.GC20225@linux.intel.com> References: <20180905114202.7757-1-roberto.sassu@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180905114202.7757-1-roberto.sassu@huawei.com> Sender: linux-integrity-owner@vger.kernel.org List-ID: 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