End-to-End Encryption of Data-at-Rest for Linux on IBM Z and LinuxONE

Transcription

1 End-to-End Encryption of Data-at-Rest for Linux on IBM Z and LinuxONE Reinhard Buendgen -- buendgen@de.ibm.com Product Owner Security for Linux on Z IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation

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3 Contents 1. What is end-to-end data-at-rest encryption? 2. Data-at-rest-encryption in Linux on Z 3. Linux Unified Key Setup 4. CPACF protected key crypto 5. dm-crypt with protected keys 6. Best practices for using dm-crypt IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 3

4 What is End-to-End Data-at-Rest Encryption? IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 4

5 Attack Points to Data Storage server Server VS application cache adapter Attack points storage server SAN Server / HV /VS insider / outsider SAN OS-kernel HV adapter Questions Where is data decrypted/encrypted? Who generates keys? Who owns (can access) the keys? Backups? Data migration? 2017 IBM Corporation 5

6 Data Encryption on Storage Subsystem Storage server Server VS application cache SAN OS-kernel HV adapter Attack points storage server -- (secured) SAN not secure Server / HV not secure VS insider / outsider not secure adapter Questions Where is data decrypted/encrypted? storage server Who generates keys? storage/os Who owns (can access) the keys? storage/os admin 2017 IBM Corporation 6

7 SAN Encryption Storage server Server VS application cache SAN OS-kernel HV adapter adapter Attack points Questions storage server -- not secured Where is data decrypted/encrypted? adapter SAN -- secured Who generates keys? system admin Server / HV -- not secured Who owns (can access) the keys? system admin VS insider / outsider not secured 2017 IBM Corporation 7

8 NAS Network Encryption NAS Server VS application cache Intranet /Internet OS-kernel HV adapter adapter Attack points Questions NAS -- not secured Where is data decrypted/encrypted? OS-Kernel & NAS Network -- secured Who generates keys? OS admin Server / HV (secured) Who owns (can access) the keys? OS admin, NAS VS insider / outsider not secured 2017 IBM Corporation 8

9 End-to-end Data Encryption Storage server Server VS application cache SAN OS-kernel HV adapter adapter Attack points Questions storage server -- secured Where is data decrypted/encrypted? applikation or kernel SAN -- secured Who generates keys? app or OS admin Server / HV (secured) Who owns (can access) the keys? app or OS admin VS insider / outsider -- not secured 2017 IBM Corporation 9

10 End-to-end Data Encryption from an SSC Storage server Server SSC application cache SAN OS-kernel HV (= secure LPAR) adapter adapter Attack points Questions storage server -- secured Where is data decrypted/encrypted? application or kernel SAN -- secured Who generates keys? app or OS admin Server / HV secured Who owns (can access) the keys? app or OS admin VS insider / outsider -- hardened 2017 IBM Corporation 10

11 Data-at-Rest Encryption in Linux on Z IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 11

12 network encryption e2e encryption Linux (on Z) Encryption of Data at Rest dm-crypt: block device / full volume encryption uses kernel crypto granularity: disk partition / logical volume ext4 with encryption option: file system encryption uses kernel crypto granularity: file, directory, symbolic link Spectrum Scale (GPFS) with encryption option: file encryption uses GSKit or Clic crypto libraries granularity: file DB2 native encryption: data base encryption uses GSKit crypto library NFS v4 with encrytion option: encryption of file transport uses kernel crypto SMB v3.1: encryption of file transport uses kernel crypto kernel crypto automatically uses CPACF for AES if the module aes_s390 is loaded GSKit and latest versions of Clic use CPACF for AES 2017 IBM Corporation 12

13 dm-crypt Overview dm-crypt a mechanism for end-to-end data encryption data only appears in the clear when in program Linux application kernel component that transparently for a whole block device (partition or LV) file system encrypts all data written to disk decrypts all data read from disk FS dm-crypt How it works: on opening a volume block device driver Linux kernel dm crypt is told which key and cipher to use SAN dm-crypt module uses in kernel-crypto can use z System HW if aes_s390 module loaded AES-CBC on z14 XTS-AES is vey fast vdisk disk XTS-AES (recommended) 13

14 Linux File System Stack direct I/O (bypassing page cache) direct I/O to device (e.g. swap) application virtual file system file system (e.g. ext4) logical block DD logical block DD physical block DD... page cache physical block DD kernel I/O system call (open, read, write) standard I/O (through page cache) layers of logical device drivers: logical volumes, RAID, multipath disk disk 14

15 Linux File System Stack with dm-crypt encrypted clear text direct I/O (bypassing page cache) direct I/O to device (e.g. swap) disk application virtual file system file system (e.g. ext4) logical block DD logical block DD physical block DD dm-crypt page cache physical block DD disk kernel I/O system call (open, read, write) standard I/O (through page cache) layers of logical device drivers: logical volumes, RAID, multipath + dm-crypt 15

16 What Volumes can be Encrypted by dm-crypt? YES: block devices Disks: SCSI disks Partitions of ECKD DASDs NO: full ECKD DASDs network file systems like NFS you can create a loopback device based on a file in a network file system SCSI disks muti-path devices (LVM2) logical volumes loop back devices

17 How to Set-up a dm-crypt Plain Format Volume once 1: generate key and store it in safe location dd if=/dev/random of=keyfile 2: open dm-crypt volume and assign it a virtual volume name associate key with volume! with every boot business as usual cryptsetup open type plain raw volume, virtual volume name, keyfile, key length, cipher creates virtual volume in /dev/mapper 3: use virtual volume mkfs (or mkswap) mount (or swapon) /dev/dasdb1 /dev/mapper/ sec_dev for each virtual dm-crypt volume, the kernel maintains raw volume and encryption info any kind of standard I/O /mount_point do not use raw volmue directly IBM Corporation

18 Linux Unified Key Setup IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 18

19 The LUKS Format Goal: provide a self containd volume format that associates a volume contents with an encryption key a cipher LUKS2: a dm-crypt sector size Protect encryption key with a password Goody: allow sharing of encryption key by up to 8 password holders Provide tooling to format volume open volume accrding to its format The result of dm-crypt data enyption depends on the sector size IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 19

20 On CPACF Performance CPACF performance depends on the size of buffers being en-/decrypted the larger the buffer the better the performance best performance with 4kB buffers dm-crypt always used 512 byte buffers starting with LUKS2 (kernel 4.12 and cryptsetup 2.0): dm-crypt can use 4kB buffers (= sectors) both for LUKS2 and plain format 512b 4kB z z relative AES GCM/XTS in memory performance IBM Corporation

21 How to Set-up a dm-crypt LUKS Volume once with every boot business as usual 1: format raw volume as dm-crypt volume cryptsetup luksformat cipher, key length, hash, pass phrase writes dm-crypt superblock to disk 2: open dm-crypt volume and assign it a virtual volume name cryptsetup luksopen dm-crypt volume, virtual volume, pass phrase creates virtual volume in /dev/mapper 3: use virtual volume mkfs (or mkswap) mount (or swapon) any kind of standard I/O do not use raw volmue directly /dev/dasdb1 /dev/mapper/ sec_dev 2 1 kernel stores raw and encryption info for virtual volume kernel translates I/O to virtual volume into I/O to raw volume and performs decryption/encryption superblock contains wrapped key IBM Corporation

22 Example setting up a dm-crypt LUKS volume format a partition as encrypted volume -- only required once # cryptsetup luksformat -c aes-xts-plain64 -s 512 /dev/dasdb1 password to encrypt (random) key must be supplied open encrypted volume as a device mapper volume # cryptsetup luksopen /dev/dasdb1 sec_dev password must be entered new virtual volume /dev/mapper/sec_dev will be created create file system -- only required once # mkfs.ext4 /dev/mapper/sec_dev mount virtual device mapper volume # mkdir /home/mysecdir # mount /dev/mapper/sec_dev /home/mysecdir use it, e.g.: # echo what is secret > /home/mysecdir/mysecret # ls /home/mysecdir # cat /home/mysecdir/mysecret luksopen mount 22

23 The LUKS(2) Format LUKS = Linux Unified Key Setup Describes format of disk superblock = initial sector(s): magic, version LUKS2 supports for 4K dm-crypt sectors cipher, mode of operation, key length, IV generation used to wrap (= encrypt) dm-crypt master keys used for data encryption hash, salt, iteration used when generating key from password (via PBKDF2) used to compute dm-crypt master key digest dm-crypt master key digest uuid 8 key descriptions Allows for up to 8 passwords to wrap the dmcrypt master key sections containing wrapped enflated keys

24 CPACF Protected Key Crypto IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 25

25 Clear Key vs. Secure Key Cryptography do not confuse secure und secret keys hardware security module (HSM) -- tamper proof E.g. Crypto Express Adapter secure key master key clear key = plain text key clear key crypto secure key crypto IBM Corporation

26 CPACF Protected Keys IBM Z function of the CPU (CPACF) each virtual server (LPAR or guest) has a hidden master key not accessible from operating system in LPAR or guest protected key: a key wrapped by the hidden LPAR/guest master protected key tokens can be generated from secure keys using CEX Adapter (secure) IBM Z CPU can compute symmetric encryption for protected keys pro no clear keys in operating system memory fast, encryption/decryption at CPU/CPACF speed, no I/O needed cons hiding of master key not as good as in HSM (not tamper proof) not certified as HSM the LPAR/guest master key is not persistent need to store (secure) key to derive protected key from memory not accessible by OS master key CPU/FW protected key IBM Corporation

27 Kernel Support for Protected Keys pkey kernel modules uses zcrypt device driver (ap) generates secure keys transfroms secure keys into protected keys cipher paes implements protected key AES paes_s390 kernel module takes secure key as argument generates and caches equivalent protected key on opening the dm-crypt volume with paes cipher: transform secure key into equivalent protected key protected key encryption/decryption at CPACF speed 28

28 dm-crypt with Protected Keys IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 29

29 End-to-End Data at Rest Encryption with Protected Key dm-crypt E2E data encryption The complete I/O path outside the kernel is encrypted: HV, adapters, links, switches, disks dm-crypt a mechanism for end-to-end data encryption data only appears in the clear in application Linux kernel component that transparently for all applications for a whole block device (partition or LV) encrypts all data written to disk decrypts all data read from disk How it works: uses in kernel-crypto can use IBM Z CPACF Protected KeyCrypto: XTS-PAES encrypted volumes must be opened before usage opening provides encryption key to kernel establishes virtual volume in /dev/mapper Linux PAES application file system dm-crypt SAN vdisk FS block device driver Linux kernel disk PKEY IBM Corporation

30 Using the PAES with dm-crypt Plain Format once with every boot BAU generate a file with a secure key # zkey generate seckey.bin xts requires access to CEX[5 6]C adapter open block device as device mapper volume # cryptsetup open --type plain --key-file seckey.bin \\ --key-size cipher paes-xts-plain64/dev/dasdb1 \\ plain_enc new virtual device mapper volume /dev/mapper/plain_enc will be created requires access to CEX[5 6]C adapter use new device mapper volume (only once) create file system: # mkfs.ext4 /dev/mapper/plain_enc mount: # mount /dev/mapper/plain_enc /mount_point access: # echo hello world > /mount_point/myfile seckey.bin /dev/dasb1 /dev/mapper/ plain_enc /mount_point IBM Corporation

31 Using the PAES with dm-crypt LUKS Format once once with every boot business as usual 0: insert new kernel modules during boot requires access to CEX5C or CEX6C adapter 1: format raw volume as dm-crypt volume cryptsetup luksformat cipher, key length, hash, password use paes instead of aes writes dm-crypt header to disk 2: open dm-crypt volume and assign it a virtual volume name cryptsetup luksopen dm-crypt volume, virtual volume, passphrase (needs not be protected) creates virtual volume in /dev/mapper 3: use virtual volume mkfs (or mkswap) mount (or swapon) any kind of standard I/O do not use raw volmue directly /dev/dasdb1 /dev/mapper/ sec_dev 2 kernel translates I/O to virtual volume into I/O to raw volume and performs decryption/encryption 1 kernel stores raw and encryption info for virtual volume header contains wrapped secure key modification of cryptsetup submitted upstream but not yet accepted IBM Corporation

32 LUKS/dm-crypt with Protected Keys - Components IBM Corporation

33 Best Practices for Using dm-crypt IBM Z / ZSP03160-USEN-38 / July 17, 2017 / 2017 IBM Corporation 35

34 Best Practices with (Protected Key) dm-crypt use /etc/cryptsetup to configure automated opening of volumes use dm-crypt volumes as LVM physical volumes allows transparent data migration protection against data loss to deal with LUKS superblock corruption back-up dm-crypt superblock to deal with HSM loss make sure you have a back-up adapter with common master key or - generate secure key from clear key in clean room environment - and store clear key in safe IBM Corporation

35 /etc/crypttab configuration file to describe how dm-crypt volumes are to be opened will be read and interpreted before /etc/fstab format each line decribes a dm-crypt volume: <dm-crypt volume> <path of block-device> <password file> none [options] options may be set to describe volatile swap and tmp volumes example lines sec_dev /dev/dasdb1 /root/pws/sec_dev.pw sec_swap /dev/dasdb2 none cipher=aes-xts-plain64,size=512,hash=sha512,swap plain_vol /dev/dasdd1 /root/seckey.bin plain,cipher=paes-xts-plain64,\\ hash=plain,size=

36 Good/Best Practice: Logical Volumes Use logical volumes: allows multi-pathing, striping, SW-RAID dynamic growth of volumes LV1 LV2 How to build logical volume? turn block device into LVM physical volume # pvcreate <device> create a volume group # vgcreate <volume group> <physical volume> add further physical volumes to volume group as needed # vgextend <volume group> <physical volume> create logical volume # lvcreate -L <size> <volume group> <logical volume> logical volume can now be accessed as /dev/<volume group>/<logical volume> VG PV1 PV2 PV3 V1 V2 V3 38

37 Using dm-crypt Volumes as Physical Volumes Use virtual dm-crypt devices as input to vgcreate Migrate data from unencrypted volume to dm-crypt volume 1: add dm-crypt based physical volume to volume group: LV1 LV2 # vgextend VG DMV VG 2: migrate data from V1 to DMV: # pvmove V1 DMV LV1 LV2 VG PV1 PV2 PV3 PV1 1 PV2 DM V1 DM V2 DM V3 V1 V2 V3 works transparently while applications access LVs V1 2 DMV V2 39

38 Back-ups of Encrypted Data Back-ups at file system level e.g. with tar back-up is plain text encryption depends on how back up is stored Raw disk image e.g. from /dev/dasdb1 back up both LUKS header & production data back-up is encrypted exactly as original disk self-contained as it contains LUKS header Do not forget: plain format: always back-up key file LUKS: back-up of the LUKS header mount luksopen cryptsetup luksdump tar dd cp/tar encrypt 40

39 Questions? 2017 IBM Corporation 41

40 Backup 2017 IBM Corporation 42

41 LUKS/dm-crypt with Protected Keys - Components Components new pkey kernel module for protected key management generate secure key cryptsetup modified zkey tansform secure key into protected key new paes kernel module to perform protected key encryption-decryption dm-crypt paes pkey new Linux kernel new introduces paes cipher dm-crypt kernel module (unchanged) extended dm-crypt management tool cryptsetup recognizes paes cipher paes CPU CEX5C stores secure key into LUKS header new zkey tool to IBM Corporation

42 LUKS/dm-crypt Protected Keys - Processing 1. format volume write secure key and paes cipher in volume header 2. open volume password not security relevant fetch secure key from volume header cryptsetup b) store sec key into LUKS header zkey a) generate secure key Linux kernel dm-crypt paes pkey pass secure key to dm-crypt let paes transfrom secure key into protected key paes CPU CEX5C 3. read/write data dm-crypt uses paes with protected key to decrypt/encypt data IBM Corporation

43 LUKS/dm-crypt Protected Keys - Processing 1. format volume write secure key and paes cipher in volume header 2. open volume password not security relevant fetch secure key from volume header cryptsetup a) fetch sec key from LUKS header b) provide sec key to dm-crypt dm-crypt paes pkey c) transform sec key into prot key Linux kernel pass secure key to dm-crypt let paes transfrom secure key into protected key 3. read/write data dm-crypt uses paes with protected key to decrypt/encypt data paes CPU CEX5C IBM Corporation

44 LUKS/dm-crypt Protected Keys - Processing 1. format volume write secure key and paes cipher in volume header 2. open volume password not security relevant cryptsetup Linux kernel dm-crypt paes pkey fetch secure key from volume header pass secure key to dm-crypt let paes transfrom secure key into protected key 3. read/write data paes read/write: en/decrypt data CPU CEX5C dm-crypt uses paes with protected key to decrypt/encypt data IBM Corporation