LUKS

Tips#

  • Linux Unified Key Setup
  • admin-guide/device-mapper/dm-crypt
  • 注意
    • 每个块设备密码独立
      • 可以考虑使用 keyfile 然后使用 crypttab 挂载
  • 加密方案
    • ROOT 加密
    • 非 ROOT 加密
  • kernel
    • AlpineLinux 配置方式 cryptroot=UUID=<UUID> cryptdm=cryptroot
    • cryptdevice=UUID=<UUID>:cryptroot
    • root=UUID={unencrypted} rw cryptdevice=/dev/disk/by-uuid/{encrypted}:root quiet nomodeset quiet rootfstype=ext4 cryptroot=UUID=3cb7aacf-4975-466b-bb6d-92a13ad60496 cryptdm=rootCrypt cryptdiscards cryptkey
  • 参考
apk add cryptsetup util-linux
# userspace DM 管理
# dmsetup dmstats
apk add device-mapper
blkid -t TYPE=crypto_LUKS
# 修改密码
cryptsetup luksChangeKey /dev/sdb2
uuidgen | tr -d '\n' > new-key.txt
cryptsetup luksAddKey /dev/sdb2 new-key.txt -d key.txt
# 查看上级设备
dmsetup deps -o devname /dev/mapper/decrypted

密钥管理#

# 所有 slot
cryptsetup luksDump /dev/sdb2
# 判断 slot
# 一个个尝试
cryptsetup open --test-passphrase --key-slot 0 /dev/sda2
# 测试密码
# --verbose 会显示 key slot 信息
cryptsetup open --verbose --test-passphrase /dev/sda2
cryptsetup open --verbose --test-passphrase /dev/sda2 -d key
# 移除未知的 key slot
cryptsetup -v luksKillSlot /dev/sdb2 1
# 查看当前的 DM
dmsetup table --showkeys
# 导出 master key
cryptsetup luksDump --dump-master-key /dev/loop0p2 -d key.txt
xxd -r -p masker-key.txt masker-key.bin
# 使用 master key 则不需要密码
cryptsetup luksAddKey /dev/sdb1 --master-key-file <(cat masker-key.bin)
cryptsetup luksAddKey /dev/sdb2 -d key.txt < new-key.txt

Root 分区加密安装#

apk add cryptsetup util-linux
# 分区
dev=/dev/sdb
boot_dev=${dev}1
root_dev=${dev}2
# +128M - boot
# rest - root
cat <<CONF | sfdisk --wipe always ${dev}
label: dos
unit: sectors
sector-size: 512
/dev/sdb1 : size=+128M, type=83, bootable
/dev/sdb2 : type=83
CONF
# 初始化
# ======
# 格式化 - 设置密码
# 设置密码文件 - 或者使用 cryptsetup 生成
uuidgen > key.txt
yes | cryptsetup -y -v luksFormat $root_dev -d key.txt
# 打开 - 挂载为 mapper
cryptsetup open $root_dev cryptroot -d key.txt
# 格式化 fs
mkfs.ext4 /dev/mapper/cryptroot
# 挂载到目录
mount /dev/mapper/cryptroot /mnt
# 卸载再次挂载确保生效
umount /mnt
cryptsetup close cryptroot
# format bootfs
mkfs.ext4 $boot_dev
# root
cryptsetup open $root_dev cryptroot -d key.txt
mount /dev/mapper/cryptroot /mnt
# boot
mkdir -p /mnt/boot
mount $boot_dev /mnt/boot
# install system
setup-disk -m sys -o sysfs.apkvol.tar.gz -s 0 -v -k virt $/mnt
apk --root /mnt add syslinux
# setup luks support
apk --root /mnt add cryptsetup util-linux
echo 'features="ata base ide scsi usb virtio ext4 cryptsetup cryptkey"' > /mnt/etc/mkinitfs/mkinitfs.conf
mkinitfs -c /mnt/etc/mkinitfs/mkinitfs.conf -b /mnt/ $(ls /mnt/lib/modules/)
# add cryptroot
# cryptroot=UUID=<UUID> cryptdm=cryptroot
# other options - https://github.com/alpinelinux/mkinitfs/blob/961726b6aeb8e12176009675f22ed0ffc2b26e14/initramfs-init.in#L443-L482
sed -i -r "s/^(default_kernel_opts)=\"([^\"]*)\"/\1=\"\2 cryptroot=UUID=$(blkid ${ROOT_DEV} -o value | head -n 1) cryptdm=cryptroot\"/" /mnt/etc/update-extlinux.conf
chroot /mnt update-extlinux
# done - close
umount -R /mnt
cryptsetup close cryptroot

FAQ#

WARNING: Locking directory /run/cryptsetup is missing!#

LUKS vs LUKS2#

  • LUKS2

    • Full disk authenticated (FDA) 提供数据 confidentiality 和 data integrity protection
      • Integrity cannot prevent a replay attack
    • cryptsetup luksFormat --type luks2 <device>
    • 新的格式,与 LUKS1 不兼容
    • sector 级别完整性校验 - Linux 4.12 - dm-integrity
      • integritysetup - 命令
    • veritysetup 支持设备 FEC(Forward Error Correction) - 安装 Linux 4.5 已有在使用
    • sector 最大支持 4096
      • 确保硬件使用相同大小,如果硬件 sector 更小可能导致数据损坏 - 部分 sector 写入
    • 使用 Argon2i 和 Argon2id 作为 PBKDF
      • memory-hard - 增加内存使用 - 是的 GPU 攻击更难 - 因为 GPU 内存成本高
      • 赢得 Password Hashing Competition 的算法
    • 默认 Argon2i (data independent variant) - 内存 cost 128MB,时间 cost 800ms,并行取决于 CPU <= 4
      • 单独配置 --pbkdf, --pbkdf-memory, --pbkdf-parallel, --iter-time
      • 迭代周期 --pbkdf-force-iterations
    • 使用 Token 独立抽象 cryptsetup 硬件部分
    • --persistent - 持久打开,之后打开不需要密钥
    • Linux kernel keyring
    • Keyslot priorities
      • normal,prefer,ignore
      • cryptsetup config <device> --key-slot 1 --priority prefer
    • LUKS2 label and subsystem
      • cryptsetup config <device> --label my_device --subsystem ""
    • 支持转换
      • cryptsetup convert <device> --type luks2
      • cryptsetup convert <device> --type luks1
      • 验证 cryptsetup luksDump <device>
  • LUKS1

    • Full disk encryption (FDE)
    • 保留长度加密 - length-preserving - encryption - 明文密文长度相同
      • 提供数据可信 (confidentiality),但不保证数据完整性
    • 使用 PBKDF (Password-Based Key Derivation Function) 增加攻击者耗时
    • PBKDF2 增加迭代次数
      • 目前 GPU 已经可以并行执行
  • 参考

# aes-xts-plain64 + hmac-sha256 / hmac-sha512 作为 authentication tag - IEEE 1619.1
# (Common FDE mode + independent authentication tag. Authentication key for HMAC is independently generated. This mode is very slow.)
cryptsetup luksFormat --type luks2 <device> --cipher aes-xts-plain64 --integrity hmac-sha256
# aes-gcm-random (native AEAD mode) - IEEE 1619.1
# 不要用于生产 - GCM 使用 96-bit nonce - GCM 硬件支持好 - AES-NI - 可以用于性能测试
cryptsetup luksFormat --type luks2 <device> --cipher aes-gcm-random --integrity aead
# ChaCha20 with Poly1305 authenticator (according to RFC7539)
cryptsetup luksFormat --type luks2 <device> --cipher chacha20-random --integrity poly1305
# LUKS2 Token
# 添加 Token
cryptsetup token add --key-description "my_token" <device>
# 添加密码到 keyring user sessing
echo -n <passphrase> | keyctl padd user my_token @u
# 如果找到了密码则自动会打开
cryptsetup open <device> <name>

调整分区大小#

apk add util-linux
# 确保 luks 分区已经填满
echo -e 'd\n\nn\n\n\n\n\n\np\nw\n' | fdisk /dev/sdb
# 调整大小
cryptsetup open /dev/sdb2 root
cryptsetup resize root
# 扩展文件系统
apk add e2fsprogs-extra
resize2fs /dev/mapper/root

help#

actiondesc
open <device> [--type <type>][<name>]打开设备,映射为 <name>
close <name>关闭设备,移除映射
resize <name>resize active device
status <name>show device status
benchmark [--cipher <cipher>]压测编码解码性能
repair <device>修复元数据
reencrypt <device>LUKS2 从新加密
erase <device>擦除所有 key,移除加密密钥
convert <device>LUKS、LUKS2 格式转换
config <device>LUKS2 配置
luksFormat <device> [<new key file>]LUKS 格式化
luksAddKey <device> [<new key file>]添加密钥
luksRemoveKey <device> [<key file>]移除密钥
luksChangeKey <device> [<key file>]修改密钥
luksConvertKey <device> [<key file>]修改密钥为新的 pbkdf 参数
luksKillSlot <device> <key slot>移除 key
luksUUID <device>UUID
isLuks <device>检测 luks 分区头
luksDump <device>分区信息
tcryptDump <device>TCRYPT 信息
bitlkDump <device>BITLK 信息
luksSuspend <device>停止 LUKS 设备,移除 key,终止所有 IO
luksResume <device>恢复
luksHeaderBackup <device>备份头
luksHeaderRestore <device>恢复头
token `<addremove
$ cryptsetup --help
cryptsetup 2.3.2
Usage: cryptsetup [OPTION...] <action> <action-specific>
-v, --verbose Shows more detailed error messages
--debug Show debug messages
--debug-json Show debug messages including JSON metadata
-c, --cipher=STRING The cipher used to encrypt the disk (see /proc/crypto)
-h, --hash=STRING The hash used to create the encryption key from the passphrase
-y, --verify-passphrase Verifies the passphrase by asking for it twice
-d, --key-file=STRING Read the key from a file
--master-key-file=STRING Read the volume (master) key from file.
--dump-master-key Dump volume (master) key instead of keyslots info
-s, --key-size=BITS The size of the encryption key
-l, --keyfile-size=bytes Limits the read from keyfile
--keyfile-offset=bytes Number of bytes to skip in keyfile
--new-keyfile-size=bytes Limits the read from newly added keyfile
--new-keyfile-offset=bytes Number of bytes to skip in newly added keyfile
-S, --key-slot=INT Slot number for new key (default is first free)
-b, --size=SECTORS The size of the device
--device-size=bytes Use only specified device size (ignore rest of device). DANGEROUS!
-o, --offset=SECTORS The start offset in the backend device
-p, --skip=SECTORS How many sectors of the encrypted data to skip at the beginning
-r, --readonly Create a readonly mapping
-q, --batch-mode Do not ask for confirmation
-t, --timeout=secs Timeout for interactive passphrase prompt (in seconds)
--progress-frequency=secs Progress line update (in seconds)
-T, --tries=INT How often the input of the passphrase can be retried
--align-payload=SECTORS Align payload at <n> sector boundaries - for luksFormat
--header-backup-file=STRING File with LUKS header and keyslots backup
--use-random Use /dev/random for generating volume key
--use-urandom Use /dev/urandom for generating volume key
--shared Share device with another non-overlapping crypt segment
--uuid=STRING UUID for device to use
--allow-discards Allow discards (aka TRIM) requests for device
--header=STRING Device or file with separated LUKS header
--test-passphrase Do not activate device, just check passphrase
--tcrypt-hidden Use hidden header (hidden TCRYPT device)
--tcrypt-system Device is system TCRYPT drive (with bootloader)
--tcrypt-backup Use backup (secondary) TCRYPT header
--veracrypt Scan also for VeraCrypt compatible device
--veracrypt-pim=INT Personal Iteration Multiplier for VeraCrypt compatible device
--veracrypt-query-pim Query Personal Iteration Multiplier for VeraCrypt compatible device
-M, --type=STRING Type of device metadata: luks, luks1, luks2, plain, loopaes, tcrypt,
bitlk
--force-password Disable password quality check (if enabled)
--perf-same_cpu_crypt Use dm-crypt same_cpu_crypt performance compatibility option
--perf-submit_from_crypt_cpus Use dm-crypt submit_from_crypt_cpus performance compatibility option
--deferred Device removal is deferred until the last user closes it
--serialize-memory-hard-pbkdf Use global lock to serialize memory hard PBKDF (OOM workaround)
-i, --iter-time=msecs PBKDF iteration time for LUKS (in ms)
--pbkdf=STRING PBKDF algorithm (for LUKS2): argon2i, argon2id, pbkdf2
--pbkdf-memory=kilobytes PBKDF memory cost limit
--pbkdf-parallel=threads PBKDF parallel cost
--pbkdf-force-iterations=LONG PBKDF iterations cost (forced, disables benchmark)
--priority=STRING Keyslot priority: ignore, normal, prefer
--disable-locks Disable locking of on-disk metadata
--disable-keyring Disable loading volume keys via kernel keyring
-I, --integrity=STRING Data integrity algorithm (LUKS2 only)
--integrity-no-journal Disable journal for integrity device
--integrity-no-wipe Do not wipe device after format
--integrity-legacy-padding Use inefficient legacy padding (old kernels)
--token-only Do not ask for passphrase if activation by token fails
--token-id=INT Token number (default: any)
--key-description=STRING Key description
--sector-size=INT Encryption sector size (default: 512 bytes)
--persistent Set activation flags persistent for device
--label=STRING Set label for the LUKS2 device
--subsystem=STRING Set subsystem label for the LUKS2 device
--unbound Create or dump unbound (no assigned data segment) LUKS2 keyslot
--json-file=STRING Read or write the json from or to a file
--luks2-metadata-size=bytes LUKS2 header metadata area size
--luks2-keyslots-size=bytes LUKS2 header keyslots area size
--refresh Refresh (reactivate) device with new parameters
--keyslot-key-size=BITS LUKS2 keyslot: The size of the encryption key
--keyslot-cipher=STRING LUKS2 keyslot: The cipher used for keyslot encryption
--encrypt Encrypt LUKS2 device (in-place encryption).
--decrypt Decrypt LUKS2 device (remove encryption).
--init-only Initialize LUKS2 reencryption in metadata only.
--resume-only Resume initialized LUKS2 reencryption only.
--reduce-device-size=bytes Reduce data device size (move data offset). DANGEROUS!
--hotzone-size=bytes Maximal reencryption hotzone size.
--resilience=STRING Reencryption hotzone resilience type (checksum,journal,none)
--resilience-hash=STRING Reencryption hotzone checksums hash
--active-name=STRING Override device autodetection of dm device to be reencrypted
Help options:
-?, --help Show this help message
--usage Display brief usage
-V, --version Print package version
<action> is one of:
open <device> [--type <type>] [<name>] - open device as <name>
close <name> - close device (remove mapping)
resize <name> - resize active device
status <name> - show device status
benchmark [--cipher <cipher>] - benchmark cipher
repair <device> - try to repair on-disk metadata
reencrypt <device> - reencrypt LUKS2 device
erase <device> - erase all keyslots (remove encryption key)
convert <device> - convert LUKS from/to LUKS2 format
config <device> - set permanent configuration options for LUKS2
luksFormat <device> [<new key file>] - formats a LUKS device
luksAddKey <device> [<new key file>] - add key to LUKS device
luksRemoveKey <device> [<key file>] - removes supplied key or key file from LUKS device
luksChangeKey <device> [<key file>] - changes supplied key or key file of LUKS device
luksConvertKey <device> [<key file>] - converts a key to new pbkdf parameters
luksKillSlot <device> <key slot> - wipes key with number <key slot> from LUKS device
luksUUID <device> - print UUID of LUKS device
isLuks <device> - tests <device> for LUKS partition header
luksDump <device> - dump LUKS partition information
tcryptDump <device> - dump TCRYPT device information
bitlkDump <device> - dump BITLK device information
luksSuspend <device> - Suspend LUKS device and wipe key (all IOs are frozen)
luksResume <device> - Resume suspended LUKS device
luksHeaderBackup <device> - Backup LUKS device header and keyslots
luksHeaderRestore <device> - Restore LUKS device header and keyslots
token <add|remove|import|export> <device> - Manipulate LUKS2 tokens
You can also use old <action> syntax aliases:
open: create (plainOpen), luksOpen, loopaesOpen, tcryptOpen, bitlkOpen
close: remove (plainClose), luksClose, loopaesClose, tcryptClose, bitlkClose
<name> is the device to create under /dev/mapper
<device> is the encrypted device
<key slot> is the LUKS key slot number to modify
<key file> optional key file for the new key for luksAddKey action
Default compiled-in metadata format is LUKS2 (for luksFormat action).
Default compiled-in key and passphrase parameters:
Maximum keyfile size: 8192kB, Maximum interactive passphrase length 512 (characters)
Default PBKDF for LUKS1: pbkdf2, iteration time: 2000 (ms)
Default PBKDF for LUKS2: argon2i
Iteration time: 2000, Memory required: 1048576kB, Parallel threads: 4
Default compiled-in device cipher parameters:
loop-AES: aes, Key 256 bits
plain: aes-cbc-essiv:sha256, Key: 256 bits, Password hashing: ripemd160
LUKS: aes-xts-plain64, Key: 256 bits, LUKS header hashing: sha256, RNG: /dev/urandom
LUKS: Default keysize with XTS mode (two internal keys) will be doubled.