现代设备加密实践 [2/3]

使用 BitLocker / LUKS 闷声发大财

March 24, 2026

本页大概是 cheatsheet 一类的东西，留个简单记录备查不算坏。

LUKS setup (with systemd) #

以 Arch Linux 为例，其它发行版思路基本一致：使用 systemd-ukify 生成并签名 UKI

Partitioning #

fdisk

 1> fdisk /dev/nvme0n1
 2m
 3g
 4n
 5
 6
 7
 8+700M
 9n
10
11
12
13
14t
151
16L
171
18p
19w
20> mkfs.fat -F32 /dev/nvme0n1p1

1cryptsetup luksFormat /dev/nvme0n1p2
2cryptsetup open /dev/nvme0n1p2 arch_root
3cryptsetup --perf-no_read_workqueue --perf-no_write_workqueue --allow-discards --persistent refresh arch_root
4mkfs.ext4 /dev/mapper/arch_root
5mount /dev/mapper/arch_root /mnt
6mkdir -p /mnt/boot
7mount /dev/nvme0n1p1 /mnt/boot

archinstall #

Note: 完整安装需要做更多事情，比如改密码、加用户、启用 NetworkManager 等

1pacstrap -K /mnt base linux linux-firmware efibootmgr systemd-ukify vim intel-ucode #amd-ucode
2genfstab -U /mnt >> /mnt/etc/fstab
3arch-chroot /mnt
4ln -sf /usr/share/zoneinfo/Asia/Shanghai /etc/localtime && hwclock --systohc
5sed -i 's/#en_US.UTF-8/en-US.UTF-8/' /etc/locale.gen && locale-gen
6echo "LANG=en_US.UTF-8" > /etc/locale.conf
7echo "localhost" > /etc/hostname
8touch /etc/vconsole.conf
9bootctl install

postinstall #

查看 blkid 得到：

/dev/nvme0n1p2: UUID="f6aa37ef-1537-4610-ae99-95262aed4a36" TYPE="crypto_LUKS" ...
/dev/mapper/arch_root: UUID="8ac7c8ed-31ec-48ce-8b58-cd61d9b0260a" BLOCK_SIZE="4096" TYPE="ext4"

相应地，写入 /etc/crypttab.initramfs 并 chmod 为 0600

# Configuration for encrypted block devices.
# See crypttab(5) for details.

# <name>       <device>                                     <password>              <options>
arch_root UUID=f6aa37ef-1537-4610-ae99-95262aed4a36 - luks,discard#,tpm2-device=auto,tpm2-measure-pcr=yes,fido2-device=auto

写入 /etc/kernel/cmdline

root=UUID=8ac7c8ed-31ec-48ce-8b58-cd61d9b0260a rw

修改 /etc/mkinitcpio.d/linux.preset

11,12c11,12
< default_image="/boot/initramfs-linux.img"
< #default_uki="/efi/EFI/Linux/arch-linux.efi"
---
> #default_image="/boot/initramfs-linux.img"
> default_uki="/boot/EFI/Linux/arch-linux.efi"

修改 /etc/mkinitcpio.conf，增加 sd-encrypt hook 并关闭 initramfs 压缩。

--- a/mkinitcpio.conf
+++ b/mkinitcpio.conf
@@ -52,7 +52,7 @@
 #
 ##   NOTE: If you have /usr on a separate partition, you MUST include the
 #    usr and fsck hooks.
-HOOKS=(base systemd autodetect microcode modconf kms keyboard keymap sd-vconsole block filesystems fsck)
+HOOKS=(base systemd autodetect microcode modconf kms keyboard sd-vconsole sd-encrypt block filesystems fsck)

 # COMPRESSION
 # Use this to compress the initramfs image. By default, zstd compression
@@ -65,6 +65,7 @@
 #COMPRESSION="xz"
 #COMPRESSION="lzop"
 #COMPRESSION="lz4"
+COMPRESSION="cat"

 # COMPRESSION_OPTIONS
 # Additional options for the compressor

执行 mkinitcpio -P，重启进入系统

Secure Boot #

Foxboron/sbctl

TPM2 enrollment #

生成用于 PCR 签名的公私钥

ukify genkey \
    --pcr-private-key=/etc/systemd/tpm2-pcr-private-key.pem \
    --pcr-public-key=/etc/systemd/tpm2-pcr-public-key.pem

写入 /etc/kernel/uki.conf

 1[UKI]
 2PCRBanks=sha256
 3PCRPKey=/etc/systemd/tpm2-pcr-public-key.pem
 4
 5[PCRSignature:initrd]
 6Phases=enter-initrd
 7PCRPrivateKey=/etc/systemd/tpm2-pcr-private-key.pem
 8PCRPublicKey=/etc/systemd/tpm2-pcr-public-key.pem
 9
10[PCRSignature:system]
11Phases=enter-initrd:leave-initrd enter-initrd:leave-initrd:sysinit
12       enter-initrd:leave-initrd:sysinit:ready
13PCRPrivateKey=/etc/systemd/tpm2-pcr-private-key.pem
14PCRPublicKey=/etc/systemd/tpm2-pcr-public-key.pem

增加 tpm2 slot

systemd-cryptenroll \
  --wipe-slot=tpm2 \
  --tpm2-device=auto \
  --tpm2-pcrs=7+15:sha256=0000000000000000000000000000000000000000000000000000000000000000 \
# --tpm2-public-key=/etc/systemd/tpm2-pcr-public-key.pem \
# --tpm2-public-key-pcrs=11:sha256 \
  --tpm2-with-pin=yes \
  /dev/nvme0n1p2

修改 /etc/crypttab.initramfs 取消 discard 标志后的注释，执行 mkinitcpio -P

FIDO2 enrollment #

> sudo systemd-cryptenroll --fido2-device=list
PATH         MANUFACTURER PRODUCT        COMPATIBLE RK CLIENTPIN UP UV ALWAYSUV
/dev/hidraw8 canokeys.org CanoKey Pigeon ✓          ✓  ✓         ✓  ✗  ✗

Legend: RK        → Resident key
        CLIENTPIN → PIN request
        UP        → User presence
        UV        → User verification
        AlwaysUV  → User verification Required

> systemd-cryptenroll /dev/nvme0n1p2 --fido2-device=auto --fido2-credential-algorithm=eddsa

更换 passphrase #

cryptsetup luksChangeKey /dev/nvme0n1p2

Note: 由于启用了 PCR 15，--unlock-tpm2-device 不会工作，因此绝对不可以直接使用 systemd-cryptenroll --wipe-slot=password

Special: LUKS + Opal #

需要 sedutil

首先使用 sedutil-cli --PSIDrevert 指令 take ownership

并在设置 LUKS 分区时，cryptsetup luksFormat 指令携带 --hw-opal-only 参数

Special: 设置 TPM lockout #

需要 tpm2-tools，见 man page [1] [2]

Measured Boot 是如何工作的 #

观察以下指令输出：

mkinitcpio

> mkinitcpio -p linux
==> Building image from preset: /etc/mkinitcpio.d/linux.preset: 'default'
==> Using default configuration file: '/etc/mkinitcpio.conf'
  -> -k /boot/vmlinuz-linux -U /boot/EFI/Linux/arch-linux.efi
// ..snip..
==> Initcpio image generation successful
==> Creating unified kernel image: '/boot/EFI/Linux/arch-linux.efi'
  -> Using ukify to build UKI
Using config file: /etc/kernel/uki.conf
+ /usr/lib/systemd/systemd-measure sign --osrel= --cmdline= --uname= --pcrpkey=/etc/systemd/tpm2-pcr-public-key.pem --linux=/boot/vmlinuz-linux --initrd= --sbat= --bank=sha256 --private-key=/etc/systemd/tpm2-pcr-private-key.pem --public-key=/etc/systemd/tpm2-pcr-public-key.pem --phase=enter-initrd
+ /usr/lib/systemd/systemd-measure sign --osrel= --cmdline= --uname= --pcrpkey=/etc/systemd/tpm2-pcr-public-key.pem --linux=/boot/vmlinuz-linux --initrd= --sbat= --bank=sha256 --private-key=/etc/systemd/tpm2-pcr-private-key.pem --public-key=/etc/systemd/tpm2-pcr-public-key.pem --phase=enter-initrd:leave-initrd --phase=enter-initrd:leave-initrd:sysinit --phase=enter-initrd:leave-initrd:sysinit:ready
Wrote unsigned /boot/EFI/Linux/arch-linux.efi
==> Unified kernel image generation successful
==> Running post hooks
  -> Running post hook: [sbctl]
Signing /boot/EFI/Linux/arch-linux.efi
✓ Signed /boot/EFI/Linux/arch-linux.efi
==> Post processing done

ukify inspect

> ukify inspect /boot/EFI/Linux/arch-linux.efi
.sbat:
  size: 323 bytes
  sha256:
  text:
    sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
    systemd-stub,1,The systemd Developers,systemd,260,https://systemd.io/
    systemd-stub.arch,1,Arch Linux,systemd,260,https://archlinux.org/packages/core/x86_64/systemd/
    uki,1,UKI,uki,1,https://uapi-group.org/specifications/specs/unified_kernel_image/
.osrel:
  size: 408 bytes
  sha256: 1c6bb63999d11ef6714d9f182b3b008315677df4d0386928fb5a00918a055890
  text:
    VERSION_ID=6.19.9-arch1-1
    NAME="Arch Linux"
    PRETTY_NAME="Arch Linux"
    ID=arch
    BUILD_ID=rolling
    ANSI_COLOR="38;2;23;147;209"
    HOME_URL="https://archlinux.org/"
    DOCUMENTATION_URL="https://wiki.archlinux.org/"
    SUPPORT_URL="https://bbs.archlinux.org/"
    BUG_REPORT_URL="https://gitlab.archlinux.org/groups/archlinux/-/issues"
    PRIVACY_POLICY_URL="https://terms.archlinux.org/docs/privacy-policy/"
    LOGO=archlinux-logo
.cmdline:
  size: 202 bytes
  sha256: 4975e8e961a40b6ea2db275e364ce49363fd24e471db3d8c37f6383b3552ac25
  text:
.uname:
  size: 14 bytes
  sha256: 8a46ec6bd08e4a101ab8e7928c033f38b2c55789fbd9237b4ba474795ffc7e44
  text:
    6.19.9-arch1-1
.pcrpkey:
  size: 451 bytes
  sha256:
  text:
.linux:
  size: 16468624 bytes
  sha256:
.initrd:
  size: 155852800 bytes
  sha256:
.pcrsig:
  size: 2100 bytes
  sha256:
  text:

有如下结论：

mkinitcpio 首先打包 initramfs 镜像，随后调用 ukify 生成 UKI，最后 sbctl 对生成的 EFI PE 文件做安全启动签名
ukify 调用了 systemd-measure，计算 PCR 11 的预期值并对其签名，输出结果对应 PE sections 中的 .pcrsig
/run/systemd/tpm2-pcr-signature.json 结构与 .pcrsig 一致
/{run,etc}/systemd/tpm2-pcr-public-key.pem 内容与 .pcrpkey 相同

实际流程为：

sd-stub 将 .pcr{sig,pkey} 内容注入到 /.extra 下，进入 initrd 后再由 sd-tmpfiles 拷到 /run/systemd (mkinitcpio !404, !414)
sd-measure 根据定义的 phase (enter-initrd/leave-initrd/sysinit) 推算 PCR 11 预期值，sd-pcrphase* 在指定时机 extend PCR 11，这也是为什么注册时 PCR 11 不直接作为 --tpm2-pcrs 参数，因为会在系统启动的各阶段被更新
sd-cryptenroll 生成 secret 写入 LUKS keyslot 和 TPM，使用 PCR 和 user PIN 保护
sd-cryptsetup 询问用户 PIN，验证 PCR 11 的度量值，满足条件再基于前述 policy 从 TPM 中取出 secret

BitLocker setup #

根据上次设置 BitLocker 的印象在虚拟机里截了几张图，不一定对，仅供参考。

在计算机配置 > 管理模板 > Windows 组件 > BitLocker Drive Encryption 下，启用

Disable new DMA devices when this computer is locked

点开 OS Drives 目录，分别启用

Require additional authentication at startup
Enable use of BitLocker authentication requiring preboot keyboard input on slates
（因为 PBA 界面没法用屏幕键盘）
Allow enhanced PINs for startup

其中「Require additional authentication at startup」的设置如下所示，此处以 Pre-boot PIN 为例。仅保留一项解锁方式，否则 BitLocker 的图形向导会提示组策略冲突。

上述配置下默认使用 PCR 7+11 测量。禁用 Secure Boot，然后 PBA 随便输个错误密码：

BitLocker Recovery Screen with Secure Boot disabled

禁用 TPM 后直接跳恢复界面：

BitLocker Recovery Screen with TPM disabled

最后一部分大概是现代 Android 的 Keystore 实现，虽然之前也算个半吊子 dev 但是退版本太久了，计划之后抽空翻一遍源码，搞清楚再写 ^^