gnuboot/site/docs/gnulinux/encrypted_debian.md

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title: Encrypted Debian GNU+Linux
x-toc-enable: true
...

This guide is written for the Debian distribution, but it should also
work for Devuan with the net installer. Other Debian based GNU+Linux
distributions may also work, using these instructions.

This guide assumes that you are using the GNU GRUB bootloader as a coreboot
payload. In this configuration, GNU GRUB runs on *bare metal* instead of
relying on BIOS or UEFI. GNU GRUB has support for directly reading LUKS volumes
and it can directly boot your Linux kernel this way. With GRUB already in the
boot flash, this means that your `/boot/` directory (containing your Linux
kernel) can be fully encrypted. The same cannot be said for most other systems,
and no other coreboot payload provides this functionality.

If booting in text mode
=======================

Libreboot ROM images are provided, which will either boot the system in classic
text mode, or with a framebuffer implemented by coreboot for video display
initialization (not to be confused with int10h VGA modes).

*Text mode* is the default video mode on *most* x86 platforms, using `INT 10H`
functions. It's an interrupt service that text-mode applications use, a hangover
from the days of CS/M and DOS. In this mode, no framebuffer exists and Libreboot
currently does not implement VGA modes. The Debian net installer will attempt
to use VGA modes that most implementations of INT 10H provide. Therefore, you
must force Debian's installation program to operate in text mode.

To boot the Debian net installer, make sure to specify `fb=false` on the linux
kernel parameters in GRUB. This will boot the installer in text mode instead
of using a framebuffer. By default, the netinstaller will try to switch to a
high resolution framebuffer. Due to lack of INT10H video BIOS services and mode
switching support in `libgfxinit`, this will fail.

In *some* setups, you don't need this. For example, if you're using an add-on
PCIe GPU on a desktop/server board (e.g. ASUS KGPE-D16/KCMA-D8, Gigabyte
GA-G41M-ES2L), you would use SeaBIOS payload with text-mode startup, but the
Video BIOS *option ROM* in your add-on graphics card would be executed, and it
would presumably handle INT10H VGA modes.

Boot the installer
==================

Libreboot on x86 can use the GNU GRUB bootloader as a bare metal coreboot
[payload](http://www.coreboot.org/Payloads#GRUB_2) if you wish, which
means that the GRUB configuration file (where your GRUB menu comes from)
is stored directly alongside Libreboot and its GRUB payload executable,
inside the flash chip. In context, this means that installing
distributions and managing them is handled slightly differently compared
to traditional BIOS or UEFI systems.

On most systems, the `/boot/` partition has to be left unencrypted while
the others are encrypted. This is so that GRUB, and therefore the
kernel, can be loaded and executed since the firmware can't open a LUKS
volume. Not so with Libreboot! Since GRUB is already included directly
as a payload, even `/boot/` can be encrypted. This protects /boot from
tampering by someone with physical access to the system.

This guide is written for Debian net installer. You can download the ISO
from the homepage on [debian.org](https://www.debian.org/). Use this on
the GRUB terminal to boot it from USB (for 64-bit Intel or AMD):

    set root='usb0'
    linux /install.amd/vmlinuz
    initrd /install.amd/initrd.gz
    boot
    
If you are on a 32-bit system (e.g. X60):

    set root='usb0'
    linux /install.386/vmlinuz
    initrd /install.386/initrd.gz
    boot
    
[This guide](grub_boot_installer.md) shows how to create a boot USB
drive with the Debian ISO image.

*This guide is only for the GRUB payload. If you use the depthcharge payload,
ignore this section entirely.*

Note: on some thinkpads, a faulty DVD drive can cause the cryptomount -a step
during boot to fail. If this happens to you, try removing the drive.

Set a strong user password (lots of lowercase/uppercase, numbers and symbols).

Use of the *diceware method* is recommended, for generating secure passphrases
(instead of passwords).

When the installer asks you to set up encryption (ecryptfs) for your home
directory, select 'Yes' if you want to: *LUKS is already secure and performs
well. Having ecryptfs on top of it will add noticeable performance penalty, for
little security gain in most use cases. This is therefore optional, and not
recommended. Choose 'no'.*

*Your user password should be different from the LUKS password which
you will set later on. Your LUKS password should, like the user
password, be secure.*

Partitioning
============

Choose 'Manual' partitioning:

-   Select drive and create new partition table
-   Single large partition. The following are mostly defaults:
    -   Use as: physical volume for encryption
    -   Encryption: aes
    -   key size: whatever default is given to you
    -   IV algorithm: whatever default is given to you
    -   Encryption key: passphrase
    -   erase data: Yes (only choose 'No' if it's a new drive that
        doesn't contain your private data)

-   Select 'configure encrypted volumes'
    -   Create encrypted volumes
    -   Select your partition
    -   Finish
    -   Really erase: Yes
    -   (erase will take a long time. be patient)
    -   (if your old system was encrypted, just let this run for about a
        minute to make sure that the LUKS header is wiped out)
-   Select encrypted space:
    -   use as: physical volume for LVM
    -   Choose 'done setting up the partition'
-   Configure the logical volume manager:
    -   Keep settings: Yes
-   Create volume group:
    -   Name: `matrix` (use this exact name)
    -   Select crypto partition
-   Create logical volume
    -   select `matrix` (use this exact name)
    -   name: `rootvol` (use this exact name)
    -   size: default, minus 2048 MB
-   Create logical volume
    -   select `matrix` (use this exact name)
    -   name: `swap` (user this exact name)
    -   size: press enter

Further partitioning
====================

Now you are back at the main partitioning screen. You will simply set
mountpoints and filesystems to use.

-   LVM LV rootvol
    -   use as: btrfs
    -   mount point: /
    -   done setting up partition
-   LVM LV swap
    -   use as: swap area
    -   done setting up partition
-   Now you select 'Finished partitioning and write changes to disk'.

Kernel
======

Installation will ask what kernel you want to use. linux-generic is
fine, but you can choose whatever you want here.

Tasksel
=======

For Debian, use the *MATE* option, or one of the others if you want. The
Libreboot project recommends MATE, unless you're saavy enough to choose
something else.

If you want debian-testing, then you should only select barebones
options here and change the entries in /etc/apt/sources.list after
install to point to the new distro, and then run `apt-get update` and
`apt-get dist-upgrade` as root, then reboot and run `tasksel` as
root. This is to avoid downloading large packages twice.

NOTE: If you want the latest up to date version of the Linux kernel,
Debian's kernel is sometimes outdated, even in the testing distro. You
might consider using [this repository](https://jxself.org/linux-libre/)
instead, which contains the most up to date versions of the Linux
kernel. These kernels are also deblobbed, like Debian's kernels, so you
can be sure that no binary blobs are present.

Postfix configuration
=====================

If asked, choose `No Configuration` here (or maybe you want to
select something else. It's up to you.)

Install the GRUB boot loader to the master boot record
======================================================

Choose `No`, and then it will still ask you what HDD to install GRUB on. Select
your HDD/SSD from the automatically generated list.

The installer will provide GRUB on your HDD/SSD, but not try to install it to
an MBR section. However, the `/boot/grub/grub.cfg` on your system will be
maintained automatically by `apt-get` when handling kernel packages.

Clock UTC
=========

Just say 'Yes'.

**At this point, your Debian system is installed. Shut down when the installer
tells you to.**

Booting your system
===================

If you didn't install GRUB during the net installation process, don't worry.
You can boot your installed system manually, using the *terminal* in GRUB on
your boot flash (the version that Libreboot gives you).

At this point, you will have finished the installation. At your GRUB
payload, press C to get to reach the GRUB terminal and enter these commands:

    cryptomount -a
    set root='lvm/matrix-rootvol'
    linux /vmlinuz root=/dev/mapper/matrix-rootvol cryptdevice=/dev/mapper/matrix-rootvol:root
    initrd /initrd.img
    boot

**If you did install GRUB, ignore the above. Just select the default `Load
Operating System` menu option and it should fully boot into your system.**

When you type your encryption passphrase in GRUB, it will seem like the process
has stalled. The same will be true when you load your linux kernel in Debian.
Just be patient and it will boot. If you see errors, just press enter to skip
them until you see the Debian GRUB menu.

ecryptfs
========

If you didn't encrypt your home directory, then you can safely ignore
this section.

Immediately after logging in, do that:

    sudo ecryptfs-unwrap-passphrase

This will be needed in the future if you ever need to recover your home
directory from another system, so write it down and keep the note
somewhere secret. Ideally, you should memorize it and then burn the note
(or not even write it down, and memorize it still)>

LUKSv2
======

LUKSv2 is fully supported nowadays, in recent Libreboot releases. The old
Libreboot release, version 20160907 (and earlier releases), did not support
LUKSv2 in GNU GRUB. By default, modern Debian distributions will use LUKSv2.

You do not need to downgrade LUKSv2 to v1, but you shouldn't use any of the
special features that LUKSv2 offers. Basically, the partitioning should be
done exactly the same way as with LUKSv1 (but with newer encryption/hashing
algorithms used by LUKSv2 partitions). This is because of limitations in the
implementation of LUKSv2 in GNU GRUB. GRUB uses its own custom implementation,
instead of directly adapting the Linux kernel implementation.

Generate distro's grub.cfg
==========================

**If `/boot/grub/grub.cfg` already exists, ignore this step.**

Now you need to set it up so that the system will automatically boot,
without having to type a bunch of commands.

Install grub-coreboot if not already installed:

    apt-get install grub-coreboot

Modify or add following lines to /etc/default/grub

    GRUB_CMDLINE_LINUX="cryptdevice=/dev/mapper/matrix-rootvol:root"
    GRUB_ENABLE_CRYPTODISK=y

Copy fonts/backgrounds to /boot/grub and
generate grub.cfg using following command:

    grub-install --target=i386-coreboot

[Refer to this guide](grub_hardening.md) for further guidance on
hardening your GRUB configuration, for security purposes.

Troubleshooting
===============

A user reported issues when booting with a docking station attached on
an X200, while decrypting the disk in GRUB. The error `AHCI transfer
timed out` was observed. The workaround was to remove the docking
station or remove the CD/DVD drive.

Here is the information on that DVD drive, which said user had:

    "sudo wodim -prcap" shows information about the drive:
    Device was not specified. Trying to find an appropriate drive...
    Detected CD-R drive: /dev/sr0
    Using /dev/cdrom of unknown capabilities
    Device type    : Removable CD-ROM
    Version        : 5
    Response Format: 2
    Capabilities   : 
    Vendor_info    : 'HL-DT-ST'
    Identification : 'DVDRAM GU10N    '
    Revision       : 'MX05'
    Device seems to be: Generic mmc2 DVD-R/DVD-RW.

    Drive capabilities, per MMC-3 page 2A:

      Does read CD-R media
      Does write CD-R media
      Does read CD-RW media
      Does write CD-RW media
      Does read DVD-ROM media
      Does read DVD-R media
      Does write DVD-R media
      Does read DVD-RAM media
      Does write DVD-RAM media
      Does support test writing

      Does read Mode 2 Form 1 blocks
      Does read Mode 2 Form 2 blocks
      Does read digital audio blocks
      Does restart non-streamed digital audio reads accurately
      Does support Buffer-Underrun-Free recording
      Does read multi-session CDs
      Does read fixed-packet CD media using Method 2
      Does not read CD bar code
      Does not read R-W subcode information
      Does read raw P-W subcode data from lead in
      Does return CD media catalog number
      Does return CD ISRC information
      Does support C2 error pointers
      Does not deliver composite A/V data

      Does play audio CDs
      Number of volume control levels: 256
      Does support individual volume control setting for each channel
      Does support independent mute setting for each channel
      Does not support digital output on port 1
      Does not support digital output on port 2

      Loading mechanism type: tray
      Does support ejection of CD via START/STOP command
      Does not lock media on power up via prevent jumper
      Does allow media to be locked in the drive via PREVENT/ALLOW command
      Is not currently in a media-locked state
      Does not support changing side of disk
      Does not have load-empty-slot-in-changer feature
      Does not support Individual Disk Present feature

      Maximum read  speed:  4234 kB/s (CD  24x, DVD  3x)
      Current read  speed:  4234 kB/s (CD  24x, DVD  3x)
      Maximum write speed:  4234 kB/s (CD  24x, DVD  3x)
      Current write speed:  4234 kB/s (CD  24x, DVD  3x)
      Rotational control selected: CLV/PCAV
      Buffer size in KB: 1024
      Copy management revision supported: 1
      Number of supported write speeds: 4
      Write speed # 0:  4234 kB/s CLV/PCAV (CD  24x, DVD  3x)
      Write speed # 1:  2822 kB/s CLV/PCAV (CD  16x, DVD  2x)
      Write speed # 2:  1764 kB/s CLV/PCAV (CD  10x, DVD  1x)
      Write speed # 3:   706 kB/s CLV/PCAV (CD   4x, DVD  0x)

    Supported CD-RW media types according to MMC-4 feature 0x37:
      Does write multi speed       CD-RW media
      Does write high  speed       CD-RW media
      Does write ultra high speed  CD-RW media
      Does not write ultra high speed+ CD-RW media