From patchwork Wed Aug 4 16:18:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Cameron X-Patchwork-Id: 1513568 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4GfxpB6C5xz9sT6 for ; Thu, 5 Aug 2021 02:21:54 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236925AbhHDQWF (ORCPT ); Wed, 4 Aug 2021 12:22:05 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:3577 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236889AbhHDQWF (ORCPT ); Wed, 4 Aug 2021 12:22:05 -0400 Received: from fraeml736-chm.china.huawei.com (unknown [172.18.147.201]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Gfxnr30Q0z6DJ3x; Thu, 5 Aug 2021 00:21:36 +0800 (CST) Received: from lhreml710-chm.china.huawei.com (10.201.108.61) by fraeml736-chm.china.huawei.com (10.206.15.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 4 Aug 2021 18:21:50 +0200 Received: from localhost.localdomain (10.123.41.22) by lhreml710-chm.china.huawei.com (10.201.108.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 4 Aug 2021 17:21:49 +0100 From: Jonathan Cameron To: , CC: , , Chris Browy , , Lorenzo Pieralisi , Bjorn Helgaas , Jeremy Kerr , Jonathan Cameron Subject: [RFC PATCH 0/4] PCI/CMA and SPDM library Date: Thu, 5 Aug 2021 00:18:35 +0800 Message-ID: <20210804161839.3492053-1-Jonathan.Cameron@huawei.com> X-Mailer: git-send-email 2.19.1 MIME-Version: 1.0 X-Originating-IP: [10.123.41.22] X-ClientProxiedBy: lhreml754-chm.china.huawei.com (10.201.108.204) To lhreml710-chm.china.huawei.com (10.201.108.61) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org This is an RFC to start discussions about how we support the Component Measurement and Authentication (CMA) ECN (pcisig.com) CMA provides an adaptation of the data objects and underlying protocol defined in the DMTF SPDM specification to be used to authenticate and conduct run-time measurements of the state of PCI devices (kind of like IMA for devices / firmware). This is done using a Data Object Exchange (DOE) protocol described in the ECN. The CMA ECN is available from the PCI SIG and SPDM can be found at https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_1.1.1.pdf CMA/SPDM is focused on establishing trust of the device by: 1) Negotiate algorithms supported. 2) Retrieve and check the certificate chain from the device against a suitable signing certificate on the host. 3) Issue a challenge to the device to verify it can sign with the private key associated with the leaf certificate. 4) (Request a measurement of device state) 5) (Establish a secure channel for further measurements or other uses) 6) (Mutual authentication) This RFC only does steps 1-3 Testing of this patch set has been conducted against QEMU emulation of the device backed by openSPDM emulation of the SPDM protocol. https://lore.kernel.org/qemu-devel/1624665723-5169-1-git-send-email-cbrowy@avery-design.com/ Open questions are called out in the individual patches but the big ones are probably: 1) Certificate management. Current code uses a _cma keyring created by the kernel, into which a suitable root certificate can be inserted from userspace. A=$(keyctl search %:_cma keyring _cma) evmctl import ecdsaca.cert.der $A Is this an acceptable way to load the root certificates for this purpose? The root of the device provided certificate chain is then checked against certificates on this keychain, but is itself (with the other certificates in the chain) loaded into an SPDM instance specific keychain. Currently there is no safe cleanup of this which will need to be fixed. Using the keychain mechanism provides a very convenient way to manage these certificates and to allow userspace to read them for debug purpose etc, but is this the right use model? Finally the leaf certificate of this chain is used to check signatures of the rest of the communications with the device. 2) ASNL1 encoder for ECDSA signature It seems from the openSPDM implementation that for these signatures, the format is a simple pair of raw values. The kernel implementation of ECDSA signature verification assumes ASN1 encoding as seems to be used in x509 certificates. Currently I work around that by encoding the signatures so that the ECDSA code can un-encode them again and use them. This seems slightly silly, but it is minimum impact on current code. Other suggestions welcome. 3) Interface to present to drivers. Currently I'm providing just one exposed function that wraps up all the exhanges until a challenge authentication response from the device. This is done using one possible sequence. I don't think it makes sense to expose the low level components due to the underlying spdm_state updates and there only being a fixed set of valid orderings. Future patches will raise questions around management of the measurements, but I'll leave those until I have some sort of implementation to shoot at. The 'on probe' use in the CXL driver is only one likely time when authentication would be needed. Note I'm new to a bunch of the areas of the kernel this touches, so have probably done things that are totally wrong. CC list is best effort to identify those who 'might' care. Please share with anyone I've missed. Thanks, Jonathan Jonathan Cameron (4): lib/asn1_encoder: Add a function to encode many byte integer values. spdm: Introduce a library for DMTF SPDM PCI/CMA: Initial support for Component Measurement and Authentication ECN cxl/pci: Add really basic CMA authentication support. drivers/cxl/Kconfig | 1 + drivers/cxl/mem.h | 2 + drivers/cxl/pci.c | 13 +- drivers/pci/Kconfig | 9 + drivers/pci/Makefile | 1 + drivers/pci/doe.c | 2 - include/linux/asn1_encoder.h | 3 + include/linux/pci-doe.h | 2 + lib/Kconfig | 3 + lib/Makefile | 2 + lib/asn1_encoder.c | 54 ++ lib/spdm.c | 1196 ++++++++++++++++++++++++++++++++++ 12 files changed, 1285 insertions(+), 3 deletions(-) create mode 100644 lib/spdm.c