From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B5757C433F5 for ; Tue, 5 Apr 2022 09:24:04 +0000 (UTC) Received: from localhost ([::1]:58856 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nbfPv-0000Wx-KT for qemu-devel@archiver.kernel.org; Tue, 05 Apr 2022 05:24:03 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41058) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nbfMS-0006pz-GV for qemu-devel@nongnu.org; Tue, 05 Apr 2022 05:20:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:35345) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nbfMN-0001s1-Hw for qemu-devel@nongnu.org; Tue, 05 Apr 2022 05:20:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649150422; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MSIIupJkNjNuDdJLmggJgcRZoBsx2nog8emsWpZU8tE=; b=FuC80AvHICRZWhNhaeLU6fsTW4U+1GfCMHbfAWd4crWmAzsMVGeEWQslWn6+MtM5puOKII lnPbEI0qUWpyDQGwJhUJSIhMNRKjlUlrqvoqQmy5htXzwArwmcKy+ZSAPAXsVu01pwmsoq RaZWwJQ8FR5DquMqGdRU/LU0nlaWI+M= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-377-pMfRKna5OaOgOUqnWcxDwA-1; Tue, 05 Apr 2022 05:20:19 -0400 X-MC-Unique: pMfRKna5OaOgOUqnWcxDwA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B2DCC3800509; Tue, 5 Apr 2022 09:20:18 +0000 (UTC) Received: from avogadro.mxp.redhat.com (unknown [10.32.181.87]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 87A0B2167D9B; Tue, 5 Apr 2022 09:20:14 +0000 (UTC) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 3/3] docs/system/i386: Add measurement calculation details to amd-memory-encryption Date: Tue, 5 Apr 2022 11:20:01 +0200 Message-Id: <20220405092001.104507-4-pbonzini@redhat.com> In-Reply-To: <20220405092001.104507-1-pbonzini@redhat.com> References: <20220405092001.104507-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Dov Murik , =?UTF-8?q?Daniel=20P=20=2E=20Berrang=C3=A9?= , "Dr . David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Dov Murik Add a section explaining how the Guest Owner should calculate the expected guest launch measurement for SEV and SEV-ES. Also update the name and links to the SEV API Spec document. Signed-off-by: Dov Murik Suggested-by: Daniel P. Berrangé Reviewed-by: Dr. David Alan Gilbert Message-Id: <20220217110059.2320497-1-dovmurik@linux.ibm.com> Signed-off-by: Paolo Bonzini --- docs/system/i386/amd-memory-encryption.rst | 54 ++++++++++++++++++++-- 1 file changed, 50 insertions(+), 4 deletions(-) diff --git a/docs/system/i386/amd-memory-encryption.rst b/docs/system/i386/amd-memory-encryption.rst index 215946f813..dcf4add0e7 100644 --- a/docs/system/i386/amd-memory-encryption.rst +++ b/docs/system/i386/amd-memory-encryption.rst @@ -47,7 +47,7 @@ The guest policy is passed as plaintext. A hypervisor may choose to read it, but should not modify it (any modification of the policy bits will result in bad measurement). The guest policy is a 4-byte data structure containing several flags that restricts what can be done on a running SEV guest. -See KM Spec section 3 and 6.2 for more details. +See SEV API Spec ([SEVAPI]_) section 3 and 6.2 for more details. The guest policy can be provided via the ``policy`` property:: @@ -92,7 +92,7 @@ expects. ``LAUNCH_FINISH`` finalizes the guest launch and destroys the cryptographic context. -See SEV KM API Spec ([SEVKM]_) 'Launching a guest' usage flow (Appendix A) for the +See SEV API Spec ([SEVAPI]_) 'Launching a guest' usage flow (Appendix A) for the complete flow chart. To launch a SEV guest:: @@ -118,6 +118,49 @@ a SEV-ES guest: - Requires in-kernel irqchip - the burden is placed on the hypervisor to manage booting APs. +Calculating expected guest launch measurement +--------------------------------------------- + +In order to verify the guest launch measurement, The Guest Owner must compute +it in the exact same way as it is calculated by the AMD-SP. SEV API Spec +([SEVAPI]_) section 6.5.1 describes the AMD-SP operations: + + GCTX.LD is finalized, producing the hash digest of all plaintext data + imported into the guest. + + The launch measurement is calculated as: + + HMAC(0x04 || API_MAJOR || API_MINOR || BUILD || GCTX.POLICY || GCTX.LD || MNONCE; GCTX.TIK) + + where "||" represents concatenation. + +The values of API_MAJOR, API_MINOR, BUILD, and GCTX.POLICY can be obtained +from the ``query-sev`` qmp command. + +The value of MNONCE is part of the response of ``query-sev-launch-measure``: it +is the last 16 bytes of the base64-decoded data field (see SEV API Spec +([SEVAPI]_) section 6.5.2 Table 52: LAUNCH_MEASURE Measurement Buffer). + +The value of GCTX.LD is +``SHA256(firmware_blob || kernel_hashes_blob || vmsas_blob)``, where: + +* ``firmware_blob`` is the content of the entire firmware flash file (for + example, ``OVMF.fd``). Note that you must build a stateless firmware file + which doesn't use an NVRAM store, because the NVRAM area is not measured, and + therefore it is not secure to use a firmware which uses state from an NVRAM + store. +* if kernel is used, and ``kernel-hashes=on``, then ``kernel_hashes_blob`` is + the content of PaddedSevHashTable (including the zero padding), which itself + includes the hashes of kernel, initrd, and cmdline that are passed to the + guest. The PaddedSevHashTable struct is defined in ``target/i386/sev.c``. +* if SEV-ES is enabled (``policy & 0x4 != 0``), ``vmsas_blob`` is the + concatenation of all VMSAs of the guest vcpus. Each VMSA is 4096 bytes long; + its content is defined inside Linux kernel code as ``struct vmcb_save_area``, + or in AMD APM Volume 2 ([APMVOL2]_) Table B-2: VMCB Layout, State Save Area. + +If kernel hashes are not used, or SEV-ES is disabled, use empty blobs for +``kernel_hashes_blob`` and ``vmsas_blob`` as needed. + Debugging --------- @@ -142,8 +185,11 @@ References `AMD Memory Encryption whitepaper `_ -.. [SEVKM] `Secure Encrypted Virtualization Key Management - `_ +.. [SEVAPI] `Secure Encrypted Virtualization API + `_ + +.. [APMVOL2] `AMD64 Architecture Programmer's Manual Volume 2: System Programming + `_ KVM Forum slides: -- 2.35.1