AMD 安全加密虚拟化 (AMD-SEV) 指南 #
AMD 的安全加密虚拟化 (SEV) 可让您加密虚拟机的内存。SEV with Encrypted State (SEV-ES) 更进一步,能够加密虚拟机的 CPU 寄存器内容。这些技术提高了系统安全性,非常适合云计算等多租户环境。它们可以防范各种跨 VM 和基于超级管理程序的攻击。举例来说,某个恶意 VM 即使逃脱了超级管理程序强制实施的限制,能够读取任意内存,它仍无法从 SEV 或 SEV-ES VM 窃取敏感数据。
本文旨在提供 SEV 和 SEV-ES 的工作原理以及如何启用和配置这些功能的基本知识。文中还涉及了与非加密虚拟化相比使用 SEV 和 SEV-ES 的某些限制。
1 SEV 简介 #
对磁盘上存储的计算机数据进行加密这项功能已得到广泛部署,但 RAM 中存储的数据并未加密。这可能会导致这些数据暴露给通过软件或硬件嗅探入侵主机系统的攻击者,在有许多租户共享物理资源的云计算环境中更是如此。假设某个恶意租户的虚拟机利用超级管理程序 Bug 逃离了沙箱,并在内存中搜索敏感数据。
AMD 的 SEV(安全加密虚拟化)技术通过独有的密钥以透明方式加密每个 VM 的内存,可以保护 Linux KVM 虚拟机。SEV 还可计算出内存内容的签名,该签名可发送给 VM 的所有者,作为固件已正确加密内存的证明。SEV 特别适用于云计算环境,在此环境中,VM 托管在远程服务器上,并不在 VM 所有者的控制之下。SEV 可以减少需要置于超级管理程序及其主机系统管理员控制之下的可信 VM 的数量。
当虚拟机正在处理敏感数据时,它可以存在于 CPU 寄存器以及内存中。如果处理出于某种原因(例如需要提供中断或与其他进程共享时间)而停止,虚拟机的 CPU 寄存器内容将会保存到超级管理程序内存中。超级管理程序可以读取此内存,即使启用了 SEV 也是如此。SEV-ES 可以防范这种情况,它会在虚拟机的处理停止时对所有 CPU 寄存器内容进行加密。SEV-ES 在 SEV 的基础上构建而成,能够为在多租户环境中运行的虚拟机缩小受攻击面。
2 VM 主机要求 #
VM 主机硬件必须支持 AMD 的 SEV 技术。要检测主机硬件是否支持 SEV,请检查 libvirt 的功能中是否包含 sev
属性,并且该属性的值是否设置恰当:
<domainCapabilities> ... <features> ... <sev supported='yes'/> ... </sev> </features> </domainCapabilities>
此外,请确保已为 kvm_amd 内核模块启用 sev 参数:
/sys/module/kvm_amd/parameters/sev = 1
3 VM 要求 #
VM 必须为新型 Q35
计算机类型且必须使用 UEFI 固件。可以让 libvirt
自动选择启用了 SEV 或 SEV-ES 的适当 UEFI 固件,也可以手动指定。目前,唯一受支持的固件为 /usr/share/qemu/ovmf-x86_64-code.bin
和 /usr/share/qemu/ovmf-x86_64-4m-code.bin
。有关如何使用 UEFI 固件以及自动选择功能的更多细节,请参见Book “虚拟化指南”, Chapter 6 “安装虚拟化组件”, Section 6.3 “安装 UEFI 支持”。
Q35 计算机类型没有 IDE 控制器,不支持 IDE 磁盘。
所有 virtio-net
设备都需要配置为禁用 iPXE 选项 ROM。iPXE 目前与 SEV 和 SEV-ES 不兼容。必须锁定对 VM 使用的所有内存区域的直接内存访问 (DMA),以防发生交换。其中包括 VM 的内存以及 QEMU 为支持 VM 运行而分配的任何内存区域,例如用于固件和变量存储的 UEFI pflash,视频 RAM 等。
4 VM 配置 #
例如,配置了 4 GB 内存的 SEV 加密 VM 将包含以下 XML 配置:
<domain type='kvm'> <memory unit='KiB'>4194304</memory> <currentMemory unit='KiB'>4194304</currentMemory> <memoryBacking> <locked/> 1 </memoryBacking> <os> <type arch='x86_64' machine='pc-q35-2.11'>hvm</type> <loader readonly='yes' type='pflash'>/usr/share/qemu/ovmf-x86_64-ms-4m-code.bin</loader> <nvram>/var/lib/libvirt/qemu/nvram/sles15-sev-guest_VARS.fd</nvram> <boot dev='hd'/> </os> <launchSecurity 2 type='sev'> <cbitpos>47</cbitpos> 3 <reducedPhysBits>1</reducedPhysBits> 4 <policy>0x0033</policy> 5 <dhCert>AAAABBBB=CCCCCDDDDD</dhCert> 6 <session>AAAABBBB=EEEEEFFFFF</session> 7 </launchSecurity> <devices> <interface type='bridge'> <source bridge='br0'/> <model type='virtio'/> <rom enabled='no'/> 8 </interface> ... </devices> ... </domain>
使用 | |
| |
启用内存加密后,如果某个内存页受保护,会使用其中一个物理地址位(也称为“C 位”)进行标记。必要元素 | |
启用内存加密后,我们会丢失物理地址空间的某些位。必要元素 | |
必要元素 | |
可选元素 | |
可选元素 | |
除了 |
Guest 策略是定义如下的 4 个无符号字节:
位 |
定义 |
---|---|
0 |
如果设置,则不允许调试 Guest |
1 |
如果设置,则不允许与其他 Guest 共享密钥 |
2 |
如果设置,则需要 SEV-ES |
3 |
如果设置,则不允许将 Guest 发送到其他平台 |
4 |
如果设置,则不得将 Guest 传送到不属于该域的其他平台 |
5 |
如果设置,则不得将 Guest 传送到不支持 SEV 的其他平台 |
6-15 |
保留 |
16-32 |
不得将 Guest 传送到固件版本更低的其他平台 |
5 VM 安装 #
virt-install
支持安装 SEV 和 SEV-ES 虚拟机。除了标准安装参数以外,还需要为 virt-install
提供用于满足 VM 要求的选项以及 --launchSecurity
选项。
下面的示例会启动通过 SEV-ES 提供保护的 SLES 15 SP4 虚拟机的网络安装。
virt-install --name sles15sp4-sev-es --location http://192.168.0.1/install/sles15sp4/x86_64 --disk size=20 --network=bridge=br0,model=virtio,rom.bar=off 1 --vcpus 4 --memory 4096 --noautoconsole --events on_reboot=destroy --machine q35 --memtune hard_limit=4563402 --launchSecurity sev,policy=0x07 2 --boot firmware=efi 3 --vnc --serial pty
iPXE 选项 ROM 与 SEV 加密的 VM 不兼容,必须在所有 virtio-net 设备上将其禁用。 | |
| |
|
6 VM 证明 #
VM 证明是校验可信软件组件是否在可信计算平台上正确实例化的过程。该过程通常涉及启动处于暂停状态的 VM,检索已实例化软件组件的启动度量,校验该度量,然后提供磁盘口令或其他密钥来解锁 VM 并恢复已暂停的引导过程。启动度量包括 VM 拥有者提供的加密项目,其中的加密信任根是 AMD SEV 平台。一旦启动度量得到校验,VM 拥有者就可以确认其软件组件未受到侵害并在可信平台上运行。
整个证明过程相当复杂,并且很可能会发生错误。必须小心确保该过程本身是安全的。例如,安全证明过程不能直接在运行 VM 的超级管理程序上执行,因为目标是证明超级管理程序不存在恶意行为,并且不会污染 VM。
SLES 15 SP4 中提供了用于证明的所有信息和 API,而 SLES 15 SP5 则引入了一个名为 virt-qemu-sev-validate
的简单实用程序,可用于满足多种证明用例的需要。例如,用于质量保证的自动化测试,以及不受大型商业管理堆栈管理的小规模 libvirt
+KVM 部署。
virt-qemu-sev-vailidate
包含在 libvirt-client-qemu
软件包中,支持脱机和联机证明模式。virt-qemu-sev-validate
要求以命令行参数的形式为证明提供输入。如果在可信计算机上调用该实用程序,则可以信任 virt-qemu-sev-validate
的结果,因为不会从不可信的来源检索任何信息。联机模式不太安全,尤其是直接在运行 VM 的超级管理程序上执行时。
无论采用哪种模式,libvirt
+KVM VM 的证明过程首先都会创建 VM 或来宾拥有者 (GO) 证书和会话 Blob,每次启动 VM 时,该证书和会话 Blob 都是唯一的。可以使用 sevctl
软件包中提供的 sevctl
实用程序创建该证书和 Blob。以下示例说明如何使用 sevctl session
命令创建所有与预启动 SEV 相关的项目。NAME 参数是可选的,允许为项目文件名指定前缀。使用 VM 名称作为前缀可便于稍后将项目与 VM 进行匹配。平台 Diffie-Hellman (DH) 证书的路径和所需的 SEV 策略是必需参数。
#
sevctl session --name test-sev /data/sev/pdh.cert 7
sevctl session
命令生成四个文件:tick.bin、take.bin、godh.b64 和 session.b64。如果使用可选的 NAME 参数,则文件将以指定的值作为前缀。传输完整性密钥 (tik.bin) 和传输加密密钥 (tek.bin) 用于证明过程的校验阶段。在启动 VM 之前,来宾拥有者 Diffie-Hellman 密钥 (godh.b64) 和会话 Blob (session.b64) 将复制到 VM XML 配置中。有关更多细节,请参见 VM 配置部分中 launchSecurity
元素的 dhCert
和 session
子元素。
创建 VM 会话项目并更新 VM XML 配置后,可以在暂停状态下启动 VM,例如:
#
virsh -c qemu+ssh://USER_NAME@HOST_NAME/system create --paused /path/to/vm.xml
在暂停状态下创建 VM 可以从超级管理程序检索启动度量,并将其与使用可信输入在可信主机上计算的度量进行比较。如果这些度量相同,则 VM 拥有者可以确信 VM 已在超级管理程序上正确实例化,并且可以安全地启动执行。以下命令演示如何使用 virsh
domlaunchsecinfo
命令从宿主超级管理程序检索已暂停 VM 的启动度量和其他 SEV 相关信息。
#
virsh -c qemu+ssh://username@hostname/system domlaunchsecinfo sevtest
sev-measurement: VZjxMSlu+UuYkWHN2mAxDVVYXRmL3wqTu84kwk+5QS+4OMii7hs6cMAmXNpmmyS/
sev-api-major : 1
sev-api-minor : 51
sev-build-id : 3
sev-policy : 7
然后,可以将检索到的启动度量提供给 virt-qemu-sev-validate
,以校验 VM 是否已安全实例化。以下示例演示度量的完整脱机证明。
#
virt-qemu-sev-validate --api-major 1 --api-minor 51 --build-id 3 --policy 7 \
--firmware /usr/share/qemu/ovmf-x86_64-4m.bin --tik sevtest_tik.bin --tek sevtest_tek.bin --num-cpus 4 \
--cpu-family 25 --cpu-model 1 --cpu-stepping 1 \
--measurement QJ0oDpFmWj+bGZzFoMPbAxTuC6QD44W5w88x/hQM8toVsB75ci7V1YDfYoI9GTk
还可以在联机模式下使用 virt-qemu-sev-validate
,在此模式下,将从宿主超级管理程序检索执行 VM 证明所需的信息。以下示例演示 VM 的联机证明,在此模式下,仅指定了宿主超级管理程序 URI、VM 名称以及关联的 TIK 和 TEK。virt-qemu-sev-validate
从宿主超级管理程序检索其余的信息,包括度量本身:
#
virt-qemu-sev-validate --tik sevtest_tik.bin --tek sevtest_tek.bin \
--connect qemu+ssh://USER_NAME@HOST_NAME/system --domain sevtest
校验 VM 启动度量后,VM 拥有者可以选择在 VM 中注入机密并恢复 VM 执行。注入机密的示例是提供一个密钥来解锁已加密的根磁盘。
#
virsh -c qemu+ssh://USER_NAME@HOST_NAME/system domsetlaunchsecstate sevtest \ --secrethdr hdr-str --secret secret-str#
virsh -c qemu+ssh://USER_NAME@HOST_NAME/system resume sevtest
7 SEV 与 KubeVirt #
KubeVirt 从版本 0.49.0
开始支持运行 SEV Guest。该功能可通过启用 WorkloadEncryptionSEV
功能门控来激活:
>
kubectl edit kubevirt kubevirt -n kubevirt
[...]
spec:
configuration:
developerConfiguration:
featureGates:
- WorkloadEncryptionSEV
[...]
要运行 SEV 加密的 Guest,必须在虚拟机规范中的 launchSecurity
域元素下包含 sev: {}
项。此外,您需要配置 firmware/bootloader
参数,以便在将 secureBoot
标志设置为 disabled
的情况下使用 efi
选项。相应的 YAML 代码段如下所示:
[...] spec: domain: firmware: bootloader: efi: secureBoot: false launchSecurity: sev: {} [...]
8 当前限制 #
SUSE 不建议在第一代 AMD EPYC™ 7000 系列处理器(代号 Naples)上将 SEV 和 SEV-ES 功能与 SUSE Linux 产品搭配使用。建议至少使用第二代 7002 系列处理器(代号 Rome)。此外,SEV 和 SEV-ES VM 还存在以下限制。
在 SEV 加密的 VM 内运行的 Guest 操作系统必须包含 SEV 支持。SUSE Linux Enterprise Server 12 SP4 及更高版本以及所有 SUSE Linux Enterprise Server 15 版本都支持 SEV。
当前不支持涉及保存及恢复实例的内存和状态的任何操作。这意味着 SEV 加密的 VM 无法从快照恢复,也无法保存/恢复或实时迁移。加密的 VM 可照常在其他主机上关闭和重启动。
SEV 加密的 VM 无法包含可直接访问的主机设备(即 PCI 直通)。
SEV 加密的 VM 与安全引导不兼容。包含安全引导支持的 UEFI 固件不适用于 SEV 或 SEV-ES VM。
SEV-ES VM 无法使用
reboot
、shutdown -r now
等命令重引导。必须通过关闭 VM 并再次启动来进行重引导。此限制不适用于 SEV VM,仅适用于 SEV-ES VM。
未来,当硬件、固件和特定软件层具有新的功能时,将会去除这些限制。
9 更多信息 #
10 法律声明 #
版权所有 © 2006–2024 SUSE LLC 和贡献者。保留所有权利。
根据 GNU 自由文档许可 (GNU Free Documentation License) 版本 1.2 或(根据您的选择)版本 1.3 中的条款,在此授予您复制、分发和/或修改本文档的权限;本版权声明和许可附带不可变部分。许可版本 1.2 的副本包含在题为“GNU Free Documentation License”的部分。
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本指南力求涵盖所有细节,但这不能确保本指南准确无误。SUSE LLC 及其关联公司、作者和译者对于可能出现的错误或由此造成的后果皆不承担责任。
11 GNU Free Documentation License #
Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc. 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
0. PREAMBLE #
The purpose of this License is to make a manual, textbook, or other functional and useful document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or non-commercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.
We have designed this License to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.
1. APPLICABILITY AND DEFINITIONS #
This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you". You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.
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Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
Include an unaltered copy of this License.
Preserve the section Entitled "History", Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
For any section Entitled "Acknowledgements" or "Dedications", Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version.
Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section.
Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.
You may add a section Entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.
5. COMBINING DOCUMENTS #
You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled "History" in the various original documents, forming one section Entitled "History"; likewise combine any sections Entitled "Acknowledgements", and any sections Entitled "Dedications". You must delete all sections Entitled "Endorsements".
6. COLLECTIONS OF DOCUMENTS #
You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.
7. AGGREGATION WITH INDEPENDENT WORKS #
A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an "aggregate" if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.
8. TRANSLATION #
Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.
If a section in the Document is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.
9. TERMINATION #
You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
10. FUTURE REVISIONS OF THIS LICENSE #
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.
ADDENDUM: How to use this License for your documents #
Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:
with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.