From patchwork Thu Sep 8 00:27:22 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuppuswamy Sathyanarayanan X-Patchwork-Id: 12969525 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70AEAECAAD3 for ; Thu, 8 Sep 2022 00:27:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229978AbiIHA1x (ORCPT ); Wed, 7 Sep 2022 20:27:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36694 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229967AbiIHA1v (ORCPT ); Wed, 7 Sep 2022 20:27:51 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C8A5D021B; Wed, 7 Sep 2022 17:27:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1662596870; x=1694132870; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=gWcX42VVm+IGeOaSGWSpSN4x1dFMPM6iK64tZSfvgbs=; b=KQM3CSuH85pUo7Dq2EaJP+Gd04jUgrZNPQPRi91ctGGQU8NwB8ibElCq 1gR5YPubCmwAbyTWQCmHz3V+hr9SX1Dkm6W1PoGpTVNjV4Is8ln11Qzao 0D/BBNa+7wpDigDCcpb4idA1gDaWTe757RDFXRjs3rZwd3bx9UdYa8fUN TaKgCs0qJ5Px921TeJPp8wbAtAQSMZ6a0JvxuexUoVLLZBmcftfc5nghn OvfaCKSt3D0inFmnDLY8SqaIJcGpYEdwpjSi87pAeqjBh0jowLNMYuGAP U5uPJu6wKsiZdvmFEQrPR5/Zl7NLIUHVaTRKz/EG2K0i7x6XlPKc2BJg0 A==; X-IronPort-AV: E=McAfee;i="6500,9779,10463"; a="360993124" X-IronPort-AV: E=Sophos;i="5.93,298,1654585200"; d="scan'208";a="360993124" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Sep 2022 17:27:50 -0700 X-IronPort-AV: E=Sophos;i="5.93,298,1654585200"; d="scan'208";a="676440358" Received: from pbarrios-mobl1.amr.corp.intel.com (HELO skuppusw-desk1.amr.corp.intel.com) ([10.252.133.9]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Sep 2022 17:27:49 -0700 From: Kuppuswamy Sathyanarayanan To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Shuah Khan Cc: "H . Peter Anvin" , Greg Kroah-Hartman , Kuppuswamy Sathyanarayanan , "Kirill A . Shutemov" , Tony Luck , Andi Kleen , Kai Huang , Wander Lairson Costa , Isaku Yamahata , marcelo.cerri@canonical.com, tim.gardner@canonical.com, khalid.elmously@canonical.com, philip.cox@canonical.com, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org Subject: [PATCH v12 3/3] Documentation/x86: Document TDX attestation process Date: Wed, 7 Sep 2022 17:27:22 -0700 Message-Id: <20220908002723.923241-4-sathyanarayanan.kuppuswamy@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220908002723.923241-1-sathyanarayanan.kuppuswamy@linux.intel.com> References: <20220908002723.923241-1-sathyanarayanan.kuppuswamy@linux.intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Document details about TDX attestation process and related user API support. Attestation details can be found in Guest-Host-Communication Interface (GHCI) for Intel Trust Domain Extensions (TDX), section titled "TD attestation". [Bagas Sanjaya fixed htmldocs warning] Signed-off-by: Kuppuswamy Sathyanarayanan Reviewed-by: Bagas Sanjaya --- Changes since v11: * Fixed htmldocs warnings. Documentation/x86/tdx.rst | 75 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) diff --git a/Documentation/x86/tdx.rst b/Documentation/x86/tdx.rst index b8fa4329e1a5..c9e3ecf86e0b 100644 --- a/Documentation/x86/tdx.rst +++ b/Documentation/x86/tdx.rst @@ -210,6 +210,81 @@ converted to shared on boot. For coherent DMA allocation, the DMA buffer gets converted on the allocation. Check force_dma_unencrypted() for details. +Attestation +=========== + +Attestation is used to verify the TDX guest trustworthiness to other +entities before provisioning secrets to the guest. For example, a key +server may request for attestation before releasing the encryption keys +to mount the encrypted rootfs or secondary drive. + +TDX module records the state of the TDX guest in various stages of guest +boot process using build time measurement register (MRTD) and runtime +measurement registers (RTMR). Measurements related to guest initial +configuration and firmware image is recorded in the MRTD register. +Measurements related to initial state, kernel image, firmware image, +command line options, initrd, ACPI tables, etc are recorded in RTMR +registers. For more details, please refer to TDX Virtual Firmware design +specification, sec titled "TD Measurement". + +At TDX guest runtime, the Intel TDX module reuses the Intel SGX attestation +infrastructure to provide support for attesting to these measurements as +described below. + +The attestation process consists of two steps: TDREPORT generation and +Quote generation. + +TDX guest uses TDCALL[TDG.MR.REPORT] to get the TDREPORT (TDREPORT_STRUCT) +from the TDX module. TDREPORT is a fixed-size data structure generated by +the TDX module which contains guest-specific information (such as build +and boot measurements), platform security version, and the MAC to protect +the integrity of the TDREPORT. + +After getting the TDREPORT, the second step of the attestation process +is to send it to the QE to generate the Quote. TDREPORT by design can only +be verified on local platform as the MAC key is bound to the platform. To +support remote verification of the TDREPORT, TDX leverages Intel SGX Quote +Enclave (QE) to verify the TDREPORT locally and convert it to a remote +verifiable Quote. Method of sending TDREPORT to QE is implemenentation +specific. Attestation software can choose whatever communication channel +available (i.e. vsock or hypercall) to send the TDREPORT to QE and receive +the Quote. + +To allow userspace attestation agent get the TDREPORT, TDX guest driver +exposes an IOCTL (TDX_CMD_GET_REPORT) interface via /dev/tdx-guest misc +device. + +TDX Guest driver +================ + +The TDX guest driver exposes IOCTL interfaces via /dev/tdx-guest misc +device to allow user space to get certain TDX guest specific details +(like attestation report, attestation quote or storage keys, etc). + +In this section, for each supported IOCTL, following information is +provided along with generic description. + +:Input parameters: Parameters passed to the IOCTL and related details. +:Output: Details about output data and return value (with details + about the non common error values). + +TDX_CMD_GET_REPORT +------------------ + +:Input parameters: struct tdx_report_req +:Output: Upon successful execution, TDREPORT data is copied to + tdx_report_req.tdreport and returns 0 or returns + -EIO on TDCALL failure and standard error number on + other common failures. + +The TDX_CMD_GET_REPORT IOCTL can be used by the attestation software to +get the TDX guest measurements data (with few other info) in the format +of TDREPORT_STRUCT. It uses TDCALL[TDG.MR.REPORT] to get the TDREPORT +from the TDX Module. + +Format of TDREPORT_STRUCT can be found in TDX 1.0 Module specification, +sec titled "TDREPORT_STRUCT". + References ==========