From patchwork Mon Feb 28 11:42:54 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dov Murik X-Patchwork-Id: 12763066 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 B63FCC433FE for ; Mon, 28 Feb 2022 11:43:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235986AbiB1LoY (ORCPT ); Mon, 28 Feb 2022 06:44:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48232 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234562AbiB1LoT (ORCPT ); Mon, 28 Feb 2022 06:44:19 -0500 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 823F94248F; Mon, 28 Feb 2022 03:43:39 -0800 (PST) Received: from pps.filterd (m0187473.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 21SAF4En036329; Mon, 28 Feb 2022 11:43:06 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : content-transfer-encoding : mime-version; s=pp1; bh=2oSiORtt5a9QwiuhXxdU0VsQ+I8NwUBoWpk6NI0GnpI=; b=tNKeBreuQH20raqshNBorvptrAB5Zuf/8pbdXLlJsbN2zzwMUCDRL+E6ccoJvakGal3G 3cwXfIruHsft59bQHSB6PNh4vxWQeg4LDAObwYx89A2lTnwbPDkzChb7pKAMMTXRgLDG SigDT3vZsSt6HohaPv1pb/8k/ykuAdJfw0k/UfmX54hqy8q9wqbGC5xxXdb0GamGLJhR zgp+R2lZ3baHaiN+wbQJu2aanFNtaS5xnAMgersUHTy83lV5i5edNV5Vp50oiI+urMjo opOiCGt7JqdnGP2PdFGXvBGrdzZABZ6pb6lK55r0c3KDmhHvtywPIPOMm/4wdqgfUITG BQ== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3egvfs9ysa-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 28 Feb 2022 11:43:06 +0000 Received: from m0187473.ppops.net (m0187473.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 21SAwTX7035846; Mon, 28 Feb 2022 11:43:05 GMT Received: from ppma01dal.us.ibm.com (83.d6.3fa9.ip4.static.sl-reverse.com [169.63.214.131]) by mx0a-001b2d01.pphosted.com with ESMTP id 3egvfs9yrq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 28 Feb 2022 11:43:05 +0000 Received: from pps.filterd (ppma01dal.us.ibm.com [127.0.0.1]) by ppma01dal.us.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 21SBXEWF017806; Mon, 28 Feb 2022 11:43:04 GMT Received: from b01cxnp22036.gho.pok.ibm.com (b01cxnp22036.gho.pok.ibm.com [9.57.198.26]) by ppma01dal.us.ibm.com with ESMTP id 3efbua0ft7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 28 Feb 2022 11:43:04 +0000 Received: from b01ledav004.gho.pok.ibm.com (b01ledav004.gho.pok.ibm.com [9.57.199.109]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 21SBh0FQ10683000 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 28 Feb 2022 11:43:00 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 29E77112061; Mon, 28 Feb 2022 11:43:00 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D4A5D11206B; Mon, 28 Feb 2022 11:42:59 +0000 (GMT) Received: from amdrome3.watson.ibm.com (unknown [9.2.130.16]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 28 Feb 2022 11:42:59 +0000 (GMT) From: Dov Murik To: linux-efi@vger.kernel.org Cc: Dov Murik , Gerd Hoffmann , Borislav Petkov , Ashish Kalra , Brijesh Singh , Tom Lendacky , Ard Biesheuvel , James Morris , "Serge E. Hallyn" , Andi Kleen , Greg KH , Andrew Scull , Dave Hansen , "Dr. David Alan Gilbert" , Lenny Szubowicz , Peter Gonda , Matthew Garrett , James Bottomley , Tobin Feldman-Fitzthum , Jim Cadden , Daniele Buono , linux-coco@lists.linux.dev, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v8 4/4] docs: security: Add secrets/coco documentation Date: Mon, 28 Feb 2022 11:42:54 +0000 Message-Id: <20220228114254.1099945-5-dovmurik@linux.ibm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220228114254.1099945-1-dovmurik@linux.ibm.com> References: <20220228114254.1099945-1-dovmurik@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: xoKGQU-TyteUFoJb6x1qg-TePv6SOUOR X-Proofpoint-GUID: OTm78mls2nGSdP-K5SrDUvu55w9L78Qu X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-02-28_04,2022-02-26_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxscore=0 clxscore=1015 suspectscore=0 bulkscore=0 spamscore=0 phishscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 mlxlogscore=999 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2202280065 Precedence: bulk List-ID: Add documentation for the efi_secret module which allows access to Confidential Computing injected secrets. Signed-off-by: Dov Murik Reviewed-by: Gerd Hoffmann --- Documentation/security/index.rst | 1 + Documentation/security/secrets/coco.rst | 103 ++++++++++++++++++++ Documentation/security/secrets/index.rst | 9 ++ 3 files changed, 113 insertions(+) diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst index 16335de04e8c..6ed8d2fa6f9e 100644 --- a/Documentation/security/index.rst +++ b/Documentation/security/index.rst @@ -17,3 +17,4 @@ Security Documentation tpm/index digsig landlock + secrets/index diff --git a/Documentation/security/secrets/coco.rst b/Documentation/security/secrets/coco.rst new file mode 100644 index 000000000000..262e7abb1b24 --- /dev/null +++ b/Documentation/security/secrets/coco.rst @@ -0,0 +1,103 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================== +Confidential Computing secrets +============================== + +This document describes how Confidential Computing secret injection is handled +from the firmware to the operating system, in the EFI driver and the efi_secret +kernel module. + + +Introduction +============ + +Confidential Computing (coco) hardware such as AMD SEV (Secure Encrypted +Virtualization) allows guest owners to inject secrets into the VMs +memory without the host/hypervisor being able to read them. In SEV, +secret injection is performed early in the VM launch process, before the +guest starts running. + +The efi_secret kernel module allows userspace applications to access these +secrets via securityfs. + + +Secret data flow +================ + +The guest firmware may reserve a designated memory area for secret injection, +and publish its location (base GPA and length) in the EFI configuration table +under a ``LINUX_EFI_COCO_SECRET_AREA_GUID`` entry +(``adf956ad-e98c-484c-ae11-b51c7d336447``). This memory area should be marked +by the firmware as ``EFI_RESERVED_TYPE``, and therefore the kernel should not +be use it for its own purposes. + +During the VM's launch, the virtual machine manager may inject a secret to that +area. In AMD SEV and SEV-ES this is performed using the +``KVM_SEV_LAUNCH_SECRET`` command (see [sev]_). The strucutre of the injected +Guest Owner secret data should be a GUIDed table of secret values; the binary +format is described in ``drivers/virt/coco/efi_secret/efi_secret.c`` under +"Structure of the EFI secret area". + +On kernel start, the kernel's EFI driver saves the location of the secret area +(taken from the EFI configuration table) in the ``efi.coco_secret`` field. +Later it checks if the secret area is populated: it maps the area and checks +whether its content begins with ``EFI_SECRET_TABLE_HEADER_GUID`` +(``1e74f542-71dd-4d66-963e-ef4287ff173b``). If the secret area is populated, +the EFI driver will autoload the efi_secret kernel module, which exposes the +secrets to userspace applications via securityfs. The details of the +efi_secret filesystem interface are in [secrets-coco-abi]_. + + +Application usage example +========================= + +Consider a guest performing computations on encrypted files. The Guest Owner +provides the decryption key (= secret) using the secret injection mechanism. +The guest application reads the secret from the efi_secret filesystem and +proceeds to decrypt the files into memory and then performs the needed +computations on the content. + +In this example, the host can't read the files from the disk image +because they are encrypted. Host can't read the decryption key because +it is passed using the secret injection mechanism (= secure channel). +Host can't read the decrypted content from memory because it's a +confidential (memory-encrypted) guest. + +Here is a simple example for usage of the efi_secret module in a guest +to which an EFI secret area with 4 secrets was injected during launch:: + + # ls -la /sys/kernel/security/secrets/coco + total 0 + drwxr-xr-x 2 root root 0 Jun 28 11:54 . + drwxr-xr-x 3 root root 0 Jun 28 11:54 .. + -r--r----- 1 root root 0 Jun 28 11:54 736870e5-84f0-4973-92ec-06879ce3da0b + -r--r----- 1 root root 0 Jun 28 11:54 83c83f7f-1356-4975-8b7e-d3a0b54312c6 + -r--r----- 1 root root 0 Jun 28 11:54 9553f55d-3da2-43ee-ab5d-ff17f78864d2 + -r--r----- 1 root root 0 Jun 28 11:54 e6f5a162-d67f-4750-a67c-5d065f2a9910 + + # hd /sys/kernel/security/secrets/coco/e6f5a162-d67f-4750-a67c-5d065f2a9910 + 00000000 74 68 65 73 65 2d 61 72 65 2d 74 68 65 2d 6b 61 |these-are-the-ka| + 00000010 74 61 2d 73 65 63 72 65 74 73 00 01 02 03 04 05 |ta-secrets......| + 00000020 06 07 |..| + 00000022 + + # rm /sys/kernel/security/secrets/coco/e6f5a162-d67f-4750-a67c-5d065f2a9910 + + # ls -la /sys/kernel/security/secrets/coco + total 0 + drwxr-xr-x 2 root root 0 Jun 28 11:55 . + drwxr-xr-x 3 root root 0 Jun 28 11:54 .. + -r--r----- 1 root root 0 Jun 28 11:54 736870e5-84f0-4973-92ec-06879ce3da0b + -r--r----- 1 root root 0 Jun 28 11:54 83c83f7f-1356-4975-8b7e-d3a0b54312c6 + -r--r----- 1 root root 0 Jun 28 11:54 9553f55d-3da2-43ee-ab5d-ff17f78864d2 + + +References +========== + +See [sev-api-spec]_ for more info regarding SEV ``LAUNCH_SECRET`` operation. + +.. [sev] Documentation/virt/kvm/amd-memory-encryption.rst +.. [secrets-coco-abi] Documentation/ABI/testing/securityfs-secrets-coco +.. [sev-api-spec] https://www.amd.com/system/files/TechDocs/55766_SEV-KM_API_Specification.pdf diff --git a/Documentation/security/secrets/index.rst b/Documentation/security/secrets/index.rst new file mode 100644 index 000000000000..ced34e9c43bd --- /dev/null +++ b/Documentation/security/secrets/index.rst @@ -0,0 +1,9 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +Secrets documentation +===================== + +.. toctree:: + + coco