Unified Extensible Firmware Interface (简体中文)/Secure Boot (简体中文)

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Secure BootUEFI 标准中的一项安全功能, 旨在为 pre-boot process添加一层保护: 通过维护被授权或禁止的在启动时运行的经过加密签名的二进制文件列表 , 它有助于使得核心引导组件(引导管理器、内核、initramfs)不被篡改.

因此,它可以被视为对个人使用环境的 securing 所做努力的延续或补充, 减少其他软件安全解决方案(如 系统加密 )无法轻易 覆盖 的攻击面,同时完全不同且不依赖于它们。 安全启动只是作为当前安全实践的一个组成部分独立存在,具有自己的一套优 缺点

注意: 为了更深入地了解 Linux 中的安全启动 , 见 Rodsbooks' Secure Bootother online resources. 文章重点介绍了如何在 Arch Linux 中设置安全启动.

检查安全启动状态

在启动操作系统之前

此时,必须查看固件设置。 如果机器已启动并正在运行,则在大多数情况下必须重新启动。

您可以在引导过程中通过按特殊键来访问固件配置。 使用的特殊键取决于固件. 它通常是 Esc, F2, Del 或者 Fn 键中的一个. 有时在启动过程中特殊键的名称会显示一小段时间 . 主板说明书往往有关于此的记载 . 如果你想要按下特殊键,请在启动机器后立即按下该键,甚至是在屏幕实际显示任何内容之前 .

进入固件设置后,请注意不要擅自更改任何设置。 通常在每个设置的底部都会有导航说明和设置的简短帮助.设置本身可能由几个页面组成,您必须导航到正确的位置.有一些安全启动设置可能简单地表示为安全启动选项,可以将其设置为打开或关闭 .

在启动操作系统之后

使用 systemd 检查系统上的安全启动状态的一种简单方法是使用 systemd-boot:

注意: 没有必要使用 systemd-boot 作为你的引导管理器来运行这个命令,它更类似于其他 *ctl systemd 实用程序(localectl、timedatectl ...)并且不会影响你的配置。
$ bootctl status
System:
     Firmware: UEFI 2.70 (American Megatrends 5.15)
  Secure Boot: enabled
   Setup Mode: user
 Boot into FW: supported
...

在这里,我们看到 Secure Boot 已启用并强制执行; 其他值是 disabled 用于安全启动和 setup 用于设置模式[1].

注意: 即使启用了安全引导,此命令也可能显示超过五位。

检查机器是否使用安全启动的另一种方法是使用以下命令:

$ od --address-radix=n --format=u1 /sys/firmware/efi/efivars/SecureBoot*

如果启用了安全启动,此命令将返回 1 作为五个列表中的最后一个整数,例如:

6  0  0  0  1

但是请注意,如果使用了功能缺失的引导加载程序,内核可能不知道安全引导(即使它在固件中启用)。 这可以通过在系统启动后不久检查内核消息来验证:

# dmesg | grep -i secure
[    0.013442] Secure boot disabled
[    0.013442] Secure boot could not be determined

The kernel messages will otherwise read Secure boot enabled.

引导安装介质

注意: 官方安装镜像不支持安全启动 (FS#53864)。 要成功启动安装介质,您需要 disable Secure Boot[损坏的链接:无效的章节].

安全启动支持最初是在 archlinux-2013.07.01-dual.iso 中添加的,后来在 archlinux-2016.06.01-dual.iso 中被删除。 当时 prebootloader 被替换为 efitools,即使后者使用未签名的 EFI 二进制文件。 从那以后,官方安装介质中就不再支持 Secure Boot。

禁用安全启动

可以通过 UEFI 固件接口禁用安全启动功能。如何访问固件配置请访问 #在启动操作系统之前.

如果使用热键不起作用并且您可以启动 Windows,您可以通过以下方式强制重新启动到固件配置(对于 Windows 10):设置 > 更新和安全 > 恢复 > 高级启动(立即重新启动)> 故障排除 > 高级选项 > UEFI 固件设置 > 重启

请注意,某些主板(Packard Bell 笔记本电脑就是这种情况)只有在您设置了管理员密码(之后可以删除)时才允许禁用安全启动。 另请参阅 Rod Smith 的禁用安全启动

Remastering the installation image

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One might want to remaster the Install ISO in a way described by previous topics of this article. For example, the signed EFI applications PreLoader.efi and HashTool.efi from #PreLoader can be adopted to here. Another option would be to borrow the BOOTx64.EFI (shim) and grubx64.efi from installation media of another GNU+Linux distribution that supports Secure Boot and modify the GRUB configuration to one's needs. In this case, the authentication chain of Secure Boot in said distribution's installation media should end to the grubx64.efi ( for example Ubuntu) so that GRUB would boot the unsigned kernel and initramfs from archiso. Note that up to this point, the article assumed one can access the ESP of the machine. But when installing a machine that never had an OS before, there is no ESP present. You should explore other articles, for example Unified Extensible Firmware Interface#Create UEFI bootable USB from ISO, to learn how this situation should be handled.

Implementing Secure Boot

There are certain conditions making for an ideal setup of Secure boot:

  1. UEFI considered mostly trusted (despite having some well known criticisms and vulnerabilities[2]) and necessarily protected by a strong password
  2. Default manufacturer/third party keys aren't in use, as they have been shown to weaken the security model of Secure Boot by a great margin[3]
  3. UEFI directly loads a user-signed EFISTUB combined kernel image (no boot manager), including microcode (if applicable) and initramfs so as to maintain throughout the boot process the chain of trust established by Secure Boot and reduce the attack surface
  4. Use of full drive encryption, so that the tools and files involved in the kernel image creation and signing process cannot be accessed and tampered with by someone having physical access to the machine.
  5. Some further improvements may be obtained by using a TPM, although tooling and support makes this harder to implement.

A simple and fully self-reliant setup is described in #Using your own keys, while #Using a signed boot loader makes use of intermediate tools signed by a third-party.

Using your own keys

警告: Replacing the platform keys with your own can end up bricking hardware on some machines, including laptops, making it impossible to get into the UEFI/BIOS settings to rectify the situation. This is due to the fact that some device (e.g GPU) firmware (OpROMs), that get executed during boot, are signed using Microsoft's key.

Secure Boot implementations use these keys:

Platform Key (PK)
Top-level key.
Key Exchange Key (KEK)
Keys used to sign Signatures Database and Forbidden Signatures Database updates.
Signature Database (db)
Contains keys and/or hashes of allowed EFI binaries.
Forbidden Signatures Database (dbx)
Contains keys and/or hashes of denylisted EFI binaries.

See The Meaning of all the UEFI Keys for a more detailed explanation.

To use Secure Boot you need at least PK, KEK and db keys. While you can add multiple KEK, db and dbx certificates, only one Platform Key is allowed.

Once Secure Boot is in "User Mode" keys can only be updated by signing the update (using sign-efi-sig-list) with a higher level key. Platform key can be signed by itself.

Install efitools

Nearly all of the following sections require you to install the efitools package.

Backing up current variables

Before creating new keys and modifying EFI variables, it is advisable to backup the current variables, so that they may be restored in case of error.

Run the following commands to backup all four of the principal Secure Boot variables:

$ efi-readvar -v PK -o old_PK.esl
$ efi-readvar -v KEK -o old_KEK.esl
$ efi-readvar -v db -o old_db.esl
$ efi-readvar -v dbx -o old_dbx.esl

If you perform these commands on a new computer or motherboard, the variables you extract will most likely be the ones provided by Microsoft.

Creating keys

Manual process

To generate keys, perform the following steps.

You will need private keys and certificates in multiple formats:

.key
PEM format private keys for EFI binary and EFI signature list signing.
.crt
PEM format certificates for sbsign(1), sbvarsign(1) and sign-efi-sig-list(1).
.cer
DER format certificates for firmware.
.esl
Certificates in an EFI Signature List for sbvarsign(1), efi-updatevar(1), KeyTool and firmware.
.auth
Certificates in an EFI Signature List with an authentication header (i.e. a signed certificate update file) for efi-updatevar(1), sbkeysync, KeyTool and firmware.

Create a GUID for owner identification:

$ uuidgen --random > GUID.txt

Platform key:

$ openssl req -newkey rsa:4096 -nodes -keyout PK.key -new -x509 -sha256 -days 3650 -subj "/CN=my Platform Key/" -out PK.crt
$ openssl x509 -outform DER -in PK.crt -out PK.cer
$ cert-to-efi-sig-list -g "$(< GUID.txt)" PK.crt PK.esl
$ sign-efi-sig-list -g "$(< GUID.txt)" -k PK.key -c PK.crt PK PK.esl PK.auth

Sign an empty file to allow removing Platform Key when in "User Mode":

$ sign-efi-sig-list -g "$(< GUID.txt)" -c PK.crt -k PK.key PK /dev/null rm_PK.auth

Key Exchange Key:

$ openssl req -newkey rsa:4096 -nodes -keyout KEK.key -new -x509 -sha256 -days 3650 -subj "/CN=my Key Exchange Key/" -out KEK.crt
$ openssl x509 -outform DER -in KEK.crt -out KEK.cer
$ cert-to-efi-sig-list -g "$(< GUID.txt)" KEK.crt KEK.esl
$ sign-efi-sig-list -g "$(< GUID.txt)" -k PK.key -c PK.crt KEK KEK.esl KEK.auth

Signature Database key:

$ openssl req -newkey rsa:4096 -nodes -keyout db.key -new -x509 -sha256 -days 3650 -subj "/CN=my Signature Database key/" -out db.crt
$ openssl x509 -outform DER -in db.crt -out db.cer
$ cert-to-efi-sig-list -g "$(< GUID.txt)" db.crt db.esl
$ sign-efi-sig-list -g "$(< GUID.txt)" -k KEK.key -c KEK.crt db db.esl db.auth
Helper scripts

A helper/convenience script is offered by the author of the reference page on this topic[4] (requires python). A mildly edited version is also packaged as sbkeysAUR.

In order to use it, simply create a folder in a secure location (e.g. /etc/efi-keys/ if later use of sbupdate-gitAUR to automate unified kernel image creation and signing is planned) and run it:

# mkdir /etc/efi-keys
# cd !$
# curl -L -O https://www.rodsbooks.com/efi-bootloaders/mkkeys.sh
# chmod +x mkkeys.sh
# ./mkkeys.sh
<Enter a Common Name to embed in the keys, e.g. "Secure Boot">

This will produce the required files in different formats.

Updating keys

Once Secure Boot is in "User Mode" any changes to KEK, db and dbx need to be signed with a higher level key.

For example, if you wanted to replace your db key with a new one:

  1. Create the new key,
  2. Convert it to EFI Signature List,
  3. Sign the EFI Signature List,
  4. Enroll the signed certificate update file.
$ cert-to-efi-sig-list -g "$(< GUID.txt)" new_db.crt new_db.esl
$ sign-efi-sig-list -g "$(< GUID.txt)" -k KEK.key -c KEK.crt db new_db.esl new_db.auth

If instead of replacing your db key, you want to add another one to the Signature Database, you need to use the option -a (see sign-efi-sig-list(1)):

$ sign-efi-sig-list -a -g "$(< GUID.txt)" -k KEK.key -c KEK.crt db new_db.esl new_db.auth

When new_db.auth is created, enroll it.

Signing EFI binaries

When Secure Boot is active (i.e. in "User Mode"), only signed EFI binaries (e.g. applications, drivers, unified kernel images) can be launched.

Manually with sbsigntools

Install sbsigntools to sign EFI binaries with sbsign(1).

提示:
  • To check if a binary is signed and list its signatures use sbverify --list /path/to/binary.
  • The rEFInd boot manager's refind-install script can sign rEFInd EFI binaries and copy them together with the db certificates to the ESP. See rEFInd#Using your own keys for instructions.
注意: If running sbsign without --output the resulting file will be filename.signed. See sbsign(1) for more information.

To sign your kernel and boot manager use sbsign, e.g.:

# sbsign --key db.key --cert db.crt --output /boot/vmlinuz-linux /boot/vmlinuz-linux
# sbsign --key db.key --cert db.crt --output esp/EFI/BOOT/BOOTx64.EFI esp/EFI/BOOT/BOOTx64.EFI
警告: Signing kernel only will not protect the initramfs from tampering. See Unified kernel image to know how to produce a combined image that you can then manually sign with sbsign.
Signing the kernel with a pacman hook

You can also use mkinitcpio's pacman hook to sign the kernel on install and updates.

Copy /usr/share/libalpm/hooks/90-mkinitcpio-install.hook to /etc/pacman.d/hooks/90-mkinitcpio-install.hook and /usr/share/libalpm/scripts/mkinitcpio-install to /usr/local/share/libalpm/scripts/mkinitcpio-install.

In /etc/pacman.d/hooks/90-mkinitcpio-install.hook, replace:

Exec = /usr/share/libalpm/scripts/mkinitcpio-install

with:

Exec = /usr/local/share/libalpm/scripts/mkinitcpio-install

In /usr/local/share/libalpm/scripts/mkinitcpio-install, replace:

install -Dm644 "${line}" "/boot/vmlinuz-${pkgbase}"

with:

sbsign --key /path/to/db.key --cert /path/to/db.crt --output "/boot/vmlinuz-${pkgbase}" "${line}"

If you are using systemd-boot, there is a dedicated pacman hook doing this task semi-automatically.

Fully automated unified kernel generation and signing with sbupdate

sbupdate is a tool made specifically to automate unified kernel image generation and signing on Arch Linux. It handles installation, removal and updates of kernels through pacman hooks.

Install sbupdate-gitAUR and configure it following the instructions given on the project's homepage.[5]

提示: If using systemd-boot, set OUT_DIR="EFI/Linux" to get your signed kernel images directly recognized without needing configuration. See systemd-boot(7) § FILES and Systemd-boot#Adding loaders.

Once configured, simply run sbupdate as root for first-time image generation.

注意: sbupdate output often contains errors such as warning: data remaining[26413568 vs 26423180]: gaps between PE/COFF sections?. Those are harmless and can be safely ignored.[6]

Putting firmware in "Setup Mode"

Secure Boot is in Setup Mode when the Platform Key is removed. To put firmware in Setup Mode, enter firmware setup utility and find an option to delete or clear certificates. How to enter the setup utility is described in #在启动操作系统之前.

Enrolling keys in firmware

Use one of the following methods to enroll db, KEK and PK certificates.

提示: As the dbx (forbidden signatures db) is empty, it can be safely left out in the following instructions.
警告: Enrolling Platform Key sets Secure Boot in "User Mode", leaving "Setup Mode", so it should be enrolled last in sequence.
Using sbkeysync

Install sbsigntools. Create a directory /etc/secureboot/keys with the following directory structure -

/etc/secureboot/keys
├── db
├── dbx
├── KEK
└── PK

For example using:

# mkdir -p /etc/secureboot/keys/{db,dbx,KEK,PK}

Then copy each of the .auth files that were generated earlier into their respective locations (for example, PK.auth into /etc/secureboot/keys/PK and so on).

See what changes will sbkeysync shall do to your system's UEFI keystore.

# sbkeysync --pk --dry-run --verbose

Finally, use sbkeysync to enroll your keys.

# sbkeysync --verbose
# sbkeysync --verbose --pk
提示: If using sbkeysync returns write errors, first run chattr -i /sys/firmware/efi/efivars/{PK,KEK,db}* immediately prior to issuing commands with sbkeysync to temporarily change file attributes, enabling writing of the efi keys within the efivars directory. See chattr(1).

On next boot the UEFI should be back in User Mode and enforcing Secure Boot policy.

Using firmware setup utility

Copy all *.cer, *.esl, *.auth to a FAT formatted file system (you can use EFI system partition).

Launch firmware setup utility and enroll db, KEK and PK certificates. Firmwares have various different interfaces, see Replacing Keys Using Your Firmware's Setup Utility for example how to enroll keys.

If the used tool supports it prefer using .auth and .esl over .cer.

Using KeyTool

KeyTool.efi is in efitools package, copy it to ESP. To use it after enrolling keys, sign it with sbsign.

# sbsign --key db.key --cert db.crt --output esp/KeyTool-signed.efi /usr/share/efitools/efi/KeyTool.efi

Launch KeyTool-signed.efi using firmware setup utility, boot loader or UEFI Shell and enroll keys.

See Replacing Keys Using KeyTool for explanation of KeyTool menu options.

Dual booting with other operating systems

Microsoft Windows

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To dual boot with Windows, you would need to add Microsoft's certificates to the Signature Database. Microsoft has two db certificates:

Create EFI Signature Lists from Microsoft's DER format certificates using Microsoft's GUID (77fa9abd-0359-4d32-bd60-28f4e78f784b) and combine them in one file for simplicity:

$ sbsiglist --owner 77fa9abd-0359-4d32-bd60-28f4e78f784b --type x509 --output MS_Win_db.esl MicWinProPCA2011_2011-10-19.crt
$ sbsiglist --owner 77fa9abd-0359-4d32-bd60-28f4e78f784b --type x509 --output MS_UEFI_db.esl MicCorUEFCA2011_2011-06-27.crt
$ cat MS_Win_db.esl MS_UEFI_db.esl > MS_db.esl

Sign a db update with your KEK. Use sign-efi-sig-list with option -a to add not replace a db certificate:

$ sign-efi-sig-list -a -g 77fa9abd-0359-4d32-bd60-28f4e78f784b -k KEK.key -c KEK.crt db MS_db.esl add_MS_db.auth

Follow #Enrolling keys in firmware to add add_MS_db.auth to Signature Database.

Using a signed boot loader

Using a signed boot loader means using a boot loader signed with Microsoft's key. There are two known signed boot loaders: PreLoader and shim. Their purpose is to chainload other EFI binaries (usually boot loaders). Since Microsoft would never sign a boot loader that automatically launches any unsigned binary, PreLoader and shim use an allowlist called Machine Owner Key list, abbreviated MokList. If the SHA256 hash of the binary (Preloader and shim) or key the binary is signed with (shim) is in the MokList they execute it, if not they launch a key management utility which allows enrolling the hash or key.

PreLoader

When run, PreLoader tries to launch loader.efi. If the hash of loader.efi is not in MokList, PreLoader will launch HashTool.efi. In HashTool you must enroll the hash of the EFI binaries you want to launch, that means your boot loader (loader.efi) and kernel.

注意: Each time you update any of the binaries (e.g. boot loader or kernel) you will need to enroll their new hash.
提示: The rEFInd boot manager's refind-install script can copy the rEFInd and PreLoader EFI binaries to the ESP. See rEFInd#Using PreLoader for instructions.
Set up PreLoader
注意: PreLoader.efi and HashTool.efi in efitools package are not signed, so their usefulness is limited. You can get a signed PreLoader.efi and HashTool.efi from preloader-signedAUR or download them manually.

Install preloader-signedAUR and copy PreLoader.efi and HashTool.efi to the boot loader directory; for systemd-boot use:

# cp /usr/share/preloader-signed/{PreLoader,HashTool}.efi esp/EFI/systemd

Now copy over the boot loader binary and rename it to loader.efi; for systemd-boot use:

# cp esp/EFI/systemd/systemd-bootx64.efi esp/EFI/systemd/loader.efi

Finally, create a new NVRAM entry to boot PreLoader.efi:

# efibootmgr --verbose --disk /dev/sdX --part Y --create --label "PreLoader" --loader /EFI/systemd/PreLoader.efi

Replace X with the drive letter and replace Y with the partition number of the EFI system partition.

This entry should be added to the list as the first to boot; check with the efibootmgr command and adjust the boot-order if necessary.

Fallback

If there are problems booting the custom NVRAM entry, copy HashTool.efi and loader.efi to the default loader location booted automatically by UEFI systems:

# cp /usr/share/preloader-signed/HashTool.efi esp/EFI/BOOT/
# cp esp/EFI/systemd/systemd-bootx64.efi esp/EFI/BOOT/loader.efi

Copy over PreLoader.efi and rename it:

# cp /usr/share/preloader-signed/PreLoader.efi esp/EFI/BOOT/BOOTx64.EFI

For particularly intransigent UEFI implementations, copy PreLoader.efi to the default loader location used by Windows systems:

# mkdir -p esp/EFI/Microsoft/Boot
# cp /usr/share/preloader-signed/PreLoader.efi esp/EFI/Microsoft/Boot/bootmgfw.efi
注意: If dual-booting with Windows, backup the original bootmgfw.efi first as replacing it may cause problems with Windows updates.

As before, copy HashTool.efi and loader.efi to esp/EFI/Microsoft/Boot/.

When the system starts with Secure Boot enabled, follow the steps above to enroll loader.efi and /vmlinuz-linux (or whichever kernel image is being used).

How to use while booting?

A message will show up that says Failed to Start loader... I will now execute HashTool. To use HashTool for enrolling the hash of loader.efi and vmlinuz.efi, follow these steps. These steps assume titles for a remastered archiso installation media. The exact titles you will get depends on your boot loader setup.

  • Select OK
  • In the HashTool main menu, select Enroll Hash, choose \loader.efi and confirm with Yes. Again, select Enroll Hash and archiso to enter the archiso directory, then select vmlinuz.efi and confirm with Yes. Then choose Exit to return to the boot device selection menu.
  • In the boot device selection menu choose Arch Linux archiso x86_64 UEFI CD
Remove PreLoader
注意: Since you are going to remove stuff, is a good idea to backup it.

Uninstall preloader-signedAUR and simply remove the copied files and revert configuration; for systemd-boot use:

# rm esp/EFI/systemd/{PreLoader,HashTool}.efi
# rm esp/EFI/systemd/loader.efi
# efibootmgr --verbose --bootnum N --delete-bootnum
# bootctl update

Where N is the NVRAM boot entry created for booting PreLoader.efi. Check with the efibootmgr command and adjust the boot-order if necessary.

注意: The above commands cover the easiest case; if you have created, copied, renamed or edited further files probably you have to handle with them, too. If PreLoader was your operational boot entry, you obviously also need to #Disabling Secure Boot[损坏的链接:无效的章节].

shim

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When run, shim tries to launch grubx64.efi. If MokList does not contain the hash of grubx64.efi or the key it is signed with, shim will launch MokManager (mmx64.efi). In MokManager you must enroll the hash of the EFI binaries you want to launch (your boot loader (grubx64.efi) and kernel) or enroll the key they are signed with.

注意:
  • If you use #shim with hash, each time you update any of the binaries (e.g. boot loader or kernel) you will need to enroll their new hash.
  • Since version 15.3, shim will not launch EFI binaries without a valid .sbat section. Run objdump -j .sbat -s /path/to/binary.efi to verify if an EFI binary has it. See the SBAT documentation for details.
Set up shim
提示: The rEFInd boot manager's refind-install script can sign rEFInd EFI binaries and copy them along with shim and the MOK certificates to the ESP. See rEFInd#Using shim for instructions.

Install shim-signedAUR.

Rename your current boot loader to grubx64.efi

# mv esp/EFI/BOOT/BOOTx64.EFI esp/EFI/BOOT/grubx64.efi

Copy shim and MokManager to your boot loader directory on ESP; use previous filename of your boot loader as as the filename for shimx64.efi:

# cp /usr/share/shim-signed/shimx64.efi esp/EFI/BOOT/BOOTx64.EFI
# cp /usr/share/shim-signed/mmx64.efi esp/EFI/BOOT/

Finally, create a new NVRAM entry to boot BOOTx64.EFI:

# efibootmgr --verbose --disk /dev/sdX --part Y --create --label "Shim" --loader /EFI/BOOT/BOOTx64.EFI

shim can authenticate binaries by Machine Owner Key or hash stored in MokList.

Machine Owner Key (MOK)
A key that a user generates and uses to sign EFI binaries.
hash
A SHA256 hash of an EFI binary.

Using hash is simpler, but each time you update your boot loader or kernel you will need to add their hashes in MokManager. With MOK you only need to add the key once, but you will have to sign the boot loader and kernel each time it updates.

shim with hash

If shim does not find the SHA256 hash of grubx64.efi in MokList it will launch MokManager (mmx64.efi).

In MokManager select Enroll hash from disk, find grubx64.efi and add it to MokList. Repeat the steps and add your kernel vmlinuz-linux. When done select Continue boot and your boot loader will launch and it will be capable launching the kernel.

shim with key

Install sbsigntools.

You will need:

.key
PEM format private key for EFI binary signing.
.crt
PEM format certificate for sbsign.
.cer
DER format certificate for MokManager.

Create a Machine Owner Key:

$ openssl req -newkey rsa:4096 -nodes -keyout MOK.key -new -x509 -sha256 -days 3650 -subj "/CN=my Machine Owner Key/" -out MOK.crt
$ openssl x509 -outform DER -in MOK.crt -out MOK.cer

Sign your boot loader (named grubx64.efi) and kernel:

# sbsign --key MOK.key --cert MOK.crt --output /boot/vmlinuz-linux /boot/vmlinuz-linux
# sbsign --key MOK.key --cert MOK.crt --output esp/EFI/BOOT/grubx64.efi esp/EFI/BOOT/grubx64.efi

You will need to do this each time they are updated. You can automate the kernel signing with a pacman hook, e.g.:

/etc/pacman.d/hooks/999-sign_kernel_for_secureboot.hook
[Trigger]
Operation = Install
Operation = Upgrade
Type = Package
Target = linux
Target = linux-lts
Target = linux-hardened
Target = linux-zen

[Action]
Description = Signing kernel with Machine Owner Key for Secure Boot
When = PostTransaction
Exec = /usr/bin/find /boot/ -maxdepth 1 -name 'vmlinuz-*' -exec /usr/bin/sh -c 'if ! /usr/bin/sbverify --list {} 2>/dev/null | /usr/bin/grep -q "signature certificates"; then /usr/bin/sbsign --key MOK.key --cert MOK.crt --output {} {}; fi' ;
Depends = sbsigntools
Depends = findutils
Depends = grep

Copy MOK.cer to a FAT formatted file system (you can use EFI system partition).

Reboot and enable Secure Boot. If shim does not find the certificate grubx64.efi is signed with in MokList it will launch MokManager (mmx64.efi).

In MokManager select Enroll key from disk, find MOK.cer and add it to MokList. When done select Continue boot and your boot loader will launch and it will be capable launching any binary signed with your Machine Owner Key.

shim with key and GRUB

Tango-edit-clear.pngThis article or section needs language, wiki syntax or style improvements. See Help:Style for reference.Tango-edit-clear.png

Reason: Too long, written like a blog post. Also many formatting issues, see Help:Style. (Discuss in Talk:Unified Extensible Firmware Interface (简体中文)/Secure Boot (简体中文))
警告: With secureboot active GRUB can't chainload EFI binaries even if they are signed.

For signing you can for example use the grub2-signing extension.

There is also a package in the AUR: grub2-signing-extensionAUR.

Run gpg --gen-key as root to create a keypair.

If you get a permission denied error try:

# chown root:root $(tty)
# export GPG_TTY"="$(tty)

Activate the gpg-agent:

/root/.gnupg/gpg.conf
use-agent
/root/.gnupg/gpg-agent.conf 
pinentry-program /usr/bin/pinentry
no-grab
default-cache-ttl 1800

Export your public key:

# gpg --export -o /root/pubkey

Mount your boot partition. (Re)install GRUB2:

# grub-install --target=x86_64-efi --efi-directory=esp --bootloader-id=GRUB -k /root/pubkey --modules="gcry_sha256 gcry_dsa gcry_rsa"

Copy your publickey to your boot partiton:

# cp /root/pubkey /boot/pubkey

Edit your GRUB custom configuration and add:

/etc/grub.d/40_Custom
insmod verify
insmod gcry_sha256
insmod gcry_dsa gcry_rsa
set check_signatures=enforce
trust (crypto0)/pubkey
insmod shim_lock
提示: (crypt0) is the name of the partition in GRUB.

Rebuild your GRUB configuration:

grub-mkconfig > /boot/grub/grub.cfg

Ensure that you created MOK.key and signed your kernel and grubx64.efi like described in shim with key.

Sign the GRUB files with grub-sign.

Run grub-verify and check if there are errors.

Here is a simple unsign hook:

/etc/pacman.d/hooks/10-unsign-grub-before-update.hook
[Trigger]
Operation = Install
Operation = Upgrade
Operation = Remove
Type = Package
Target = linux
Target = linux-lts
Target = linux-zen
Target = grub
Target = intel-ucode
Target = amd-ucode

[Action]
Description = Unsigning GRUB
When = PreTransaction
Exec = /usr/bin/grub-unsign

And a bash script you can use to sign again after the update:

 .bashrc
function sign-update () {
   /usr/bin/grub-unsign
   if [ $? -ne 0 ]; then return 1; fi
   /usr/bin/find /boot/ -maxdepth 1 -name 'vmlinuz-*' -not -name "*.sig" -exec /usr/bin/sh -c \
   'if ! /usr/bin/sbverify --list {} 2>/dev/null | /usr/bin/grep -q "signature certificates"; \
   then echo "Signing with sbsign."; /usr/bin/sbsign --key MOK.key --cert MOK.crt --output {} {}; fi' \;
   /usr/bin/grub-sign
   /usr/bin/find /boot/ -maxdepth 1 -name 'vmlinuz-*' -not -name "*.sig" -exec /usr/bin/sh -c \
   'echo ""; echo {}; /usr/bin/sbverify --list {};' \;
}
Remove shim

Uninstall shim-signedAUR, remove the copied shim and MokManager files and rename back your boot loader.

Protecting Secure Boot

The only way to prevent anyone with physical access to disable Secure Boot is to set a user/administrator password in the firmware.

Most UEFI provide such feature, usually listed under the "Security" section.

另见