VerityBook/README.md

FedoraBook

Let's put all the fancy features together, we developed in the last years:

• Combined kernel+initramfs EFI binaries
• Secure Boot
• clevis with TPM2
• LUKS2
• dm-verity + squashfs root
• Flatpak
• flickerless boot

and build a Chromebook like Fedorabook, where you can install all software via Flatpak.

This is WIP. Please test and report issues, comments or missing components on https://pagure.io/Fedorabook/issues

Goals

• secure boot to the login screen
• immutable base OS
• ensured integrity to the login screen
• encrypted volatile data
• A/B boot switching for updates
• Flatpak
• basic desktop
• optional: bind encrypted data partition to TPM2
• optional: frequent reencryption of the data partition

Non-Goals

• can't secure against a remote attacker writing anything to disk
• can't secure against a remote attacker scraping secret keys from the kernel

FAQ

Isn't encrypting everything enough?

If a remote attacker modifies your binaries in /usr/bin, you cannot be sure of a secure boot to the login screen anymore.

Why readonly /etc?

A remote attacker modifying /etc can completely change your boot sequence and you cannot be sure of a secure boot to the login screen anymore.

All configurable files have been whitelisted and moved to /cfg.

TODO

• merge mkimage.sh and clonedisk
• move all quirks from prepare-root.sh to quirks directory
• source all quirks depending on package installation on command line options
• change partition UUIDs for /data
  • UUID for TPM LUKS
  • UUID for LUKS
  • UUID for unencrypted xfs
• ensure /data to be on same disk as root
• add "load=" to kernel command line via efi stub
• add admin LUKS key via public key
• sssd
• support more clevis pins and mixed pins
• firmware update
• option to always clean data disk on boot
• instead of gpg use:

$ openssl dgst -sha256 -sign ../DB.key -out sha512sum.txt.sig sha512sum.txt
$ openssl dgst -sha256 -verify  <(openssl x509 -in ../DB.crt -pubkey -noout) -signature sha512sum.txt.sig sha512sum.txt

Complete / What works already?

• boot from single efi binary
• dm_verity + squashfs immutable, integrity checked root
• passwd + shadow + group + gshadow decoupled from system in /var
• bind LUKS2 with tpm2 to machine
• swap on LUKS2 with tpm2 (no password for resume from disk??)
• /home /cfg and /var on single data partition
• Secure Boot
• selinux

Known Failures

• no kernel command line on DELL ( you need a newer systemd https://github.com/systemd/systemd/pull/10001 ) cp linuxx64.efi.stub to this git repo dir from a compiled upstream systemd
• gnome-software: can't update firmware repo
• systemd: failed to umount /var
• needs a ´´´restorecond -FmvR /cfg /var /home´´´ after first boot, because systemd-tmpfiles does not seem to restore all context
• vga switcheroo is not accessible for lockdown=1, because the kernel does not allow access to /sys/kernel/debug

Create

Export your GPG Key

$ gpg2 --export --export-options export-minimal <KEYNAME> > FedoraBook.gpg

Prepare the Image

$ sudo ./prepare-root.sh \
  --pkglist pkglist.txt \
  --excludelist excludelist.txt \
  --name FedoraBook \
  --logo logo.bmp \
  --reposd <REPOSDIR> \
  --releasever 29

This will create the following files and directories:

• FedoraBook - keep this directory around for updates (includes needed passwd/group history)
• FedoraBook-29.<datetime> - the resulting
• FedoraBook-latest.json - a metadata file for the update server

or download a prebuilt image, unpack and use this as <IMGDIR>.

Sign the release

Get efitools. Compile and create your keys. Copy LockDown.efi DB.key DB.crt from efitools to the fedorabook directory.

Optionally copy Shell.efi (might be /usr/share/edk2/ovmf/Shell.efi) to the fedorabook directory.

$ sudo ./mkrelease.sh FedoraBook-latest.json

then upload to your update server:

$ TARBALL="$(jq -r '.name' FedoraBook-latest.json)-$(jq -r '.version' FedoraBook-latest.json)".tgz
$ scp "$TARBALL" FedoraBook-latest.json <DESTINATION> 

QEMU disk image

$ sudo ./mkimage.sh <IMGDIR> image.raw 

or with the json file:

$ sudo ./mkimage.sh FedoraBook-latest.json image.raw 

USB stick

$ sudo ./mkimage.sh <IMGDIR> /dev/disk/by-path/pci-…-usb…

or with the json file:

$ sudo ./mkimage.sh FedoraBook-latest.json /dev/disk/by-path/pci-…-usb…

Install from USB stick

Warning: This will wipe the entire target disk

Preparation

• Enter BIOS
  • turn on UEFI boot
  • turn on TPM2
  • set a BIOS admin password
• Enter BIOS boot menu
• Select USB stick
• Login (user: admin, pw: admin)
• Start gnome-terminal

Installation

If you can encrypt your disk via the BIOS, do so.

If you cannot:

• use the option --crypttpm2, if you have a TPM2 chip
• use the option --crypt otherwise

$ sudo clonedisk <options> <usb stick device> <harddisk device>

Post

• reboot
• remove stick

The first boot takes longer as the system tries to bind the LUKS to the TPM2 on the machine. It also populates /var with the missing directories.

You can always clear the data partition via:

# wipefs --all --force /dev/<disk partition 5>

and then either make a xfs

# mkfs.xfs -L data /dev/<disk partition 5>

or LUKS

# echo -n "zero key" | cryptsetup luksFormat --type luks2 /dev/<disk partition 4> /dev/stdin
# echo -n "zero key" | cryptsetup luksFormat --type luks2 /dev/<disk partition 5> /dev/stdin

On the media created with mkimage.sh, this is partition number 3.

Post Boot

Persistent journal

$ sudo mkdir /var/log/journal

LUKS

Set a new LUKS password, if you installed with --crypt or --crypttpm2. The initial password is zero key.

Updating

# systemd-inhibit update <UPDATE-URL>

Secure Boot

Warning: This will wipe all the secure boot keys. Make sure the BIOS contains an option to restore the default keys.

• Enter BIOS
  • turn on Secure Boot
  • turn on Setup Mode
• Boot from stick with Shell.efi and LockDown.efi
• Execute LockDown.efi
• reset
• Secure Boot into signed FedoraBook release