Full root filesystem encryption on an Armbian system (NEW, replaces 2017 tutorial on this topic)


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Full root filesystem encryption on an Armbian system

(new, fully rewritten, replaces my earlier tutorial on this topic)

 

MMGen (https://github.com/mmgen)

 

This tutorial provides detailed, step-by-step instructions for setting up full root filesystem encryption on an Armbian system.  The disk can be unlocked remotely via SSH, permitting unattended bootup.

 

Note that unlike my earlier tutorial all steps are performed within a running Armbian system.

 

The tutorial has been tested with Debian Buster mainline and Ubuntu Bionic and Focal legacy images on the Orange Pi PC2 and RockPi 4.  However, it should should work for most Armbian images and Armbian-supported boards.

 

An automated script that performs the same steps, saving you much time and effort, can be found at https://github.com/mmgen/mmgen-geek-tools

 

Requirements:

  • A SoC with a running, upgradeable and Internet-connected Armbian system
  • A blank Micro-SD card and USB card reader, or, alternatively, a blank eMMC installed on the board
  • The ability to edit text files and do simple administrative tasks on the Linux command line

 

Step 1 - Preliminaries

 

All steps in this tutorial are performed as root user on a running Armbian system (the “host”).

 

The encrypted system (the “target”) will be created on a blank micro-SD card.  If your board has an eMMC not currently in use, the system can be created on it instead.

 

Architecture of host and target (e.g. 64-bit or 32-bit ARM) must be the same.

 

For best results, the host and target hardware should also be identical or similar.  Building on a host with more memory than the target, for example, may lead to disk unlocking failure on the target.

 

If you’re building the target system for the currently running board and with the currently running image, which is the recommended approach, the two preceding points will be a non-issue.

 

Packages will be installed using APT, so the host machine must be Internet-connected and its clock correctly set.

 

 

Step 2 - Upgrade your system and install the cryptsetup-bin package

 

# apt update && apt upgrade
# apt install cryptsetup-bin

 

 

Step 3 - Get and unpack the latest Armbian image for your board

 

Create your build directory:

# mkdir armbenc-build && cd armbenc-build

 

Download the Armbian image of your choice for your board, place it in this directory and unpack:

# xz -dv *.img.xz

 

 

Step 4 - Create mount directories and set up the loop mount

 

Create the mount directories:

# mkdir -p mnt boot root

 

Determine your first free loop device:

# losetup -f

 

Associate the image file with the loop device name displayed by the previous command.  This will be '/dev/loop0' in most cases, but if your output was different, substitute that for '/dev/loop0' in the following steps.

# losetup -P /dev/loop0 *.img

 

Examine the disk image using fdisk on the loop device:

# fdisk -l /dev/loop0

 

The output should look something like this:

Device       Boot Start     End Sectors  Size Id Type
/dev/loop0p1      32768 3489791 3457024  1.7G 83 Linux

 

Make a note of the start sector (32768 in this case).  You’ll need this value in the steps below.

 

Now mount the loop device:

# mount /dev/loop0p1 mnt

 

 

Step 5 - Copy the boot loader to the SD card

 

Insert the blank micro-SD card and card reader into a USB port.

 

Determine the SD card’s device name using 'dmesg' or 'lsblk'.  We’ll assume it to be '/dev/sda', since that’s the most likely case.  If your device name is different, substitute it for '/dev/sda' in the the following steps.  For an eMMC, the device name will probably be '/dev/mmcblk1'.

 

WARNING: if '/dev/sda' refers to some other storage device, running the following commands unchanged will destroy data on that device, so always remember to substitute the correct device name!!!  The best way to eliminate this danger is to disconnect all unused storage devices on the board before proceeding further.

 

Copy the image’s boot loader to the SD card, using the Start sector value from Step 4 as the argument for 'count':

# dd if=$(echo *.img) of=/dev/sda bs=512 count=32768

 

 

Step 6 - Partition the SD card

 

# fdisk /dev/sda

 

At the fdisk prompt, create a new DOS disk label with the 'o' command.  Use the 'n' command to create a primary partition of size +200M beginning at the same Start sector as the disk image.  Type 'p' to view the partition table, which should now look something like this:

Device      Boot  Start      End  Sectors  Size Id Type
/dev/sda1         32768   442367   409600  200M 83 Linux

 

Use 'n' again to create another primary partition beginning one sector after the first partition’s end sector and filling the remainder of the card.  Type 'p' once more to view the partition table:

Device      Boot  Start      End  Sectors  Size Id Type
/dev/sda1         32768   442367   409600  200M 83 Linux
/dev/sda2        442368 30636031 30193664 14.4G 83 Linux

 

Ensure that the first partition’s Start sector matches that of the disk image (32768 in this example) and that the second partition’s Start sector is one greater than the End sector of the first (442368 and 442367, respectively, in this example).  If you’ve made a mistake, use 'd' to delete a partition and start again.


Once everything looks correct, type 'w' to write the partition table to disk.

 

 

Step 7 - Copy the system to the SD card

 

The following commands will create a filesystem on the SD card’s boot partition and copy the boot partition data from the image file to it.  Don’t forget to substitute the correct device name if necessary.  If you’re building the system on an eMMC, the boot partition device is likely to be '/dev/mmcblk1p1' instead of '/dev/sda1'.

 # mkfs.ext4 /dev/sda1            # or '/dev/mmcblk1p1', for an eMMC target
 # e2label /dev/sda1 CRYPTO_BOOT
 # mount /dev/sda1 boot
 # cp -av mnt/boot/* boot
 # (cd boot; ln -s . boot)

 

Create the encrypted root partition.  When prompted for a passphrase, it’s advisable to choose an easy one like 'abc' for now.  The passphrase can be changed later with the 'cryptsetup luksChangeKey' command (type 'man cryptsetup' for details) once your encrypted system is up and running.

# cryptsetup luksFormat /dev/sda2 # or '/dev/mmcblk1p2', for an eMMC target

 

Activate the encrypted root partition and create a filesystem on it:

# cryptsetup luksOpen /dev/sda2 rootfs  # enter your passphrase from above
# mkfs.ext4 /dev/mapper/rootfs

 

Mount the encrypted root partition and copy the system to it:

# mount /dev/mapper/rootfs root
# (cd mnt && rsync -a --info=progress2 --exclude=boot * ../root)
# sync # be patient, this could take a while
# mkdir root/boot
# touch root/root/.no_rootfs_resize

 

Unmount the boot partition and image and free the loop device:

# umount mnt boot
# losetup -d /dev/loop0

 

 

Step 8 - Prepare the target system chroot

 

# BOOT_PART=($(lsblk -l -o NAME,LABEL | grep CRYPTO_BOOT))
# ROOT_PART=${BOOT_PART%1}2
# ROOT_UUID="$(lsblk --nodeps --noheadings --output=UUID /dev/$ROOT_PART)"
# BOOT_UUID="$(lsblk --noheadings --output=UUID /dev/$BOOT_PART)"

# cd root
# mount /dev/$BOOT_PART boot
# mount -o rbind /dev dev
# mount -t proc proc proc
# mount -t sysfs sys sys

 

Copy '/etc/resolv.conf' and '/etc/hosts' so you’ll have a working Internet connection within the chroot:

# cat /etc/resolv.conf > etc/resolv.conf
# cat /etc/hosts > etc/hosts

 

If you’re using non-default APT repositories, you may need to copy their configuration files as well so that 'apt update' and 'apt install' will use them inside the chroot.  Note that you can only do this if the host and target systems have the same distro/version.  If that’s not the case, you’ll have to edit the target files by hand.

# cat /etc/apt/sources.list > etc/apt/sources.list
# cat /etc/apt/sources.list.d/armbian.list > etc/apt/sources.list.d/armbian.list

 

If you’re using an apt proxy, then copy its configuration file too:

# cp /etc/apt/apt.conf.d/*proxy etc/apt/apt.conf.d/

 

 

Step 9 - Edit or create required configuration files in the target system

 

Perform the editing steps below using a text editor of your choice:

 

  1. Edit 'boot/boot.cmd', deleting the lines beginning with 'setenv rootdev', 'setenv console' and 'setenv bootlogo'.
  2. Edit 'boot/armbianEnv.txt' so that the 'rootdev', 'console' and 'bootlogo' lines read as follows:

    rootdev=/dev/mapper/rootfs
    console=display
    bootlogo=false
    
  3. Edit 'etc/initramfs-tools/initramfs.conf'.  If your board will have a statically configured IP, add the following line to the end of the file, substituting the correct IP in place of 192.168.0.88:

    IP=192.168.0.88:::255.255.255.0::eth0:off
    

    If the board will be configured via DHCP, then edit the DEVICE line as follows:

    DEVICE=eth0
    
  4. If host and target systems are both Debian buster, you may wish add some key modules to the initramfs to avoid a blank display at bootup time.  The easiest way to do this is to add all currently loaded modules as follows:
    # lsmod | cut -d ' ' -f1 | tail -n+2 > etc/initramfs-tools/modules
    
  5. Retrieve the SSH public key from the remote unlocking host and copy it to the target:

    # mkdir -p etc/dropbear-initramfs
    # rsync yourusername@remote_machine:.ssh/id_*.pub etc/dropbear-initramfs/authorized_keys
    

    If you want to unlock the disk from more than one host, then edit the authorized_keys file by hand, adding the required additional keys.

  6. Create 'etc/crypttab':

    # echo "rootfs UUID=$ROOT_UUID none initramfs,luks" > etc/crypttab
    
  7. Create 'etc/fstab':

    # echo '/dev/mapper/rootfs / ext4 defaults,noatime,nodiratime,commit=600,errors=remount-ro 0 1' > etc/fstab
    # echo "UUID=$BOOT_UUID /boot ext4 defaults,noatime,nodiratime,commit=600,errors=remount-ro 0 2" >> etc/fstab
    # echo 'tmpfs /tmp tmpfs defaults,nosuid 0 0' >> etc/fstab
    
  8. Create the dropbear configuration file:

    # echo 'DROPBEAR_OPTIONS="-p 2222"' > etc/dropbear-initramfs/config
    # echo 'DROPBEAR=y' >> etc/dropbear-initramfs/config
    
  9. If the target is Ubuntu bionic, then a deprecated environment variable must be set as follows:

    # echo 'export CRYPTSETUP=y' > etc/initramfs-tools/conf.d/cryptsetup
    

 

Step 10 - Chroot into the target system, install packages and configure

 

Now chroot into the encrypted system.  All remaining steps will be performed inside the chroot:

# chroot .

 

Recompile the uboot configuration file:

# mkimage -C none -A arm -T script -d /boot/boot.cmd /boot/boot.scr

 

Install the cryptsetup package and the dropbear SSH server:

# apt update
# echo 'force-confdef' > /root/.dpkg.cfg
# apt --yes install cryptsetup-initramfs dropbear-initramfs # for a buster or focal image
# apt --yes install cryptsetup dropbear-initramfs           # for a bionic image
# rm /root/.dpkg.cfg

 

Make sure everything was included in the initramfs (all three commands should produce output):

# lsinitramfs /boot/initrd.img* | grep 'usr.*cryptsetup'
# lsinitramfs /boot/initrd.img* | grep dropbear
# lsinitramfs /boot/initrd.img* | grep authorized_keys

 

Your work is finished! Exit the chroot and shut down the board:

# exit
# halt -p

 

Insert your freshly written SD card into the board’s main SD slot (or, if the target is an eMMC, just remove the SD card from that slot) and reboot.


Unlock the disk by executing the following command on your remote unlocking machine, substituting the correct password and IP address if necessary:

$ ssh -p 2222 -x root@192.168.0.88 'echo -n abc > /lib/cryptsetup/passfifo'

 

You may also unlock the disk from the target board’s console if you wish.  Note, however, that certain disk images (RockPi 4 buster mainline, for example) might give you a blank display at startup, so you’ll have to enter your disk password “blindly”.  This bug will hopefully be fixed in the future.


If all went well, your root-filesystem encrypted Armbian system is now up and running!

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Armbian is a community driven open source project. Do you like to contribute your code?

Thanks for pointing that out!

 

As far as overlap goes, I think this tutorial (and the automated script) has a clear use case, as it creates encrypted Armbian systems without building or compiling anything, which is much easier for most users (the automated script can create a fully configured system on your SD card or eMMC in a matter of minutes).

 

Secondly, the tutorial can be a valuable learning experience for those interested in better understanding disk partitioning, loop devices, LUKS encryption, uBoot, the Linux bootup process, basic administrative commands, etc.

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I am wondering if this script would break nand-sata-install since the base Armbian images are single partition while the new encrypted image on SD card is having a separate Boot and Root partition. 

 

If this is the case then how can we move the image to eMMC from SD?

 

-R

 

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Thanks for the post.
I test the script with Orange Pi zero with the latest Ubuntu Focal image.

Armbian 20.08.1 Focal with Linux 5.8.5-sunxi

After writing to the SD, at booting phase, following error occurs.

 

Starting kernel ...

Uncompressing Linux... done, booting the kernel.

Error: invalid dtb and unrecognized/unsupported machine ID
  r1=0x00001029, r2=0x40000100
  r2[]=05 00 00 00 01 00 41 54 00 00 00 00 00 00 00 00
Available machine support:

ID (hex)        NAME
ffffffff        Generic DT based system
ffffffff        Allwinner suniv Family
ffffffff        Allwinner sun9i Family
ffffffff        Allwinner A83t board
ffffffff        Allwinner sun8i Family
ffffffff        Allwinner sun7i (A20) Family
ffffffff        Allwinner sun6i (A31) Family
ffffffff        Allwinner sun4i/sun5i Families

Please check your kernel config and/or bootloader.

@MMGen anything I need to do additionally to support Orange Pi Zero?

 

Thanks.

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9 hours ago, DevShanky said:

I am wondering if this script would break nand-sata-install since the base Armbian images are single partition while the new encrypted image on SD card is having a separate Boot and Root partition. 

 

If this is the case then how can we move the image to eMMC from SD?

 

-R

 

You don't need nand-sata-install, because the tutorial (and script) create the encrypted system directly on the eMMC. This has been tested successfully on the RockPi 4. Would like to hear from users how it works on other boards.

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4 hours ago, sunzone said:

Thanks for the post.
I test the script with Orange Pi zero with the latest Ubuntu Focal image.

Armbian 20.08.1 Focal with Linux 5.8.5-sunxi

After writing to the SD, at booting phase, following error occurs.

...SNIP....

@MMGen anything I need to do additionally to support Orange Pi Zero?

 

Thanks.

This is not the kind of error I would expect to see. Are you sure you performed all the steps correctly, didn't omit anything? Is the SD card itself in working order? I'll take a look at the Focal Orange Pi Zero image to see if there's anything there that might be causing this error, but I don't have that board to test on, unfortunately.

 

UPDATE: I looked at your image. Some things you might want to check:

 

1) Make sure you're editing armbianEnv.txt correctly. After performing the edits, the file should look like this:

verbosity=1
bootlogo=false
console=display
disp_mode=1920x1080p60
overlay_prefix=sun8i-h3
overlays=usbhost2 usbhost3
rootdev=/dev/mapper/rootfs
rootfstype=ext4

2) In boot.cmd there are two lines beginning with 'setenv rootdev'. Make sure you're deleting the first one.

 

If that doesn't work, there are other things you might try and see whether you get the same or similar error at bootup:

 

1) Use the automated script instead of the tutorial.

2) Try the Buster image instead of Focal.

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20 hours ago, MMGen said:

This is not the kind of error I would expect to see. Are you sure you performed all the steps correctly, didn't omit anything? Is the SD card itself in working order? I'll take a look at the Focal Orange Pi Zero image to see if there's anything there that might be causing this error, but I don't have that board to test on, unfortunately.

 

UPDATE: I looked at your image. Some things you might want to check:

 

1) Make sure you're editing armbianEnv.txt correctly. After performing the edits, the file should look like this:


verbosity=1
bootlogo=false
console=display
disp_mode=1920x1080p60
overlay_prefix=sun8i-h3
overlays=usbhost2 usbhost3
rootdev=/dev/mapper/rootfs
rootfstype=ext4

2) In boot.cmd there are two lines beginning with 'setenv rootdev'. Make sure you're deleting the first one.

 

If that doesn't work, there are other things you might try and see whether you get the same or similar error at bootup:

 

1) Use the automated script instead of the tutorial.

2) Try the Buster image instead of Focal.

 

1) Checked

2) Applied

Still the same error..

1) Used automated script

2) Used Buster image
Still the same error....

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31 minutes ago, sunzone said:

Also tried with an Opi Zero Plus I had since it is 64bit, following the steps and also using the script.

Boot hangs after 




Starting kernel ...

 

Sorry to hear that. I'm afraid I've run out of options, since I don't have an Opi Zero for testing. If you really need root fs encryption, then you might try building Armbian with the CRYPTROOT_ENABLE option mentioned by @DevShankyin the post above.

 

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On 10/21/2020 at 6:10 PM, MMGen said:

Sorry to hear that. I'm afraid I've run out of options, since I don't have an Opi Zero for testing. If you really need root fs encryption, then you might try building Armbian with the CRYPTROOT_ENABLE option mentioned by @DevShankyin the post above.

 

I will look into that.
Thanks.

Edit: building Armbian with the CRYPTROOT_ENABLE option works :)

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