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docs: rewrite quickstart

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# How to get started with Lanzaboote-based SecureBoot?
# Quick Start: NixOS Secure Boot
**Requirements** :
This document attempts to guide users into setting up UEFI Secure Boot
for their NixOS system using a custom key chain. The audience are
experienced NixOS users.
- Using `systemd-boot`
- Either the private certificate to sign files or control over your SecureBoot keys to insert your own, read the section on how to enroll your keys
This guide has been tested on a Lenovo Thinkpad and is expected to
work on other Thinkpads without change. On other systems, certain
steps may be different.
**Disclaimer** : This project bring its own UEFI stub to circumvent the difficulty introduced by UKI model where everything has to baked in.
The authors are aware of the concept of "extending" initrds through <https://github.com/systemd/systemd/blob/main/src/boot/efi/stub.c#L23>.
We are exploring this avenue to minimize our dependency on this custom stub, but, we want to explore the full needs of the NixOS usecases first.
## ⚠ Disclaimers ⚠
## Enrolling your own keys
Secure Boot for NixOS is still in development and has some sharp
edges. There may be cases where you end up with a system that does not
boot.
**Disclaimer** : Some device firmware, e.g. GPU (so-called [OpROMs](https://en.wikipedia.org/wiki/Option_ROM)) get executed at boot, replacing your platform keys
with your own, can cause them to not run anymore under SecureBoot, as they are signed using [Microsoft Corporation UEFI CA 2011 certificate], aka the Microsoft 3rd Party UEFI CA certificate.
To know about *limited* mitigations regarding this, **read** the "keeping Microsoft keys" subsection.
**We only recommend this to NixOS users that are comfortable using
recovery tools to restore their system or have a backup ready.**
**Disclaimer** : TPMs interaction are out of scope for this project, please read more about TPM eventlog, but note that Lanzastub do not implement any TPM event logging for now.
## Requirements
### Entering into Setup Mode
To be able to setup Secure Boot on your device, NixOS needs to be
installed in UEFI mode and
[`systemd-boot`](https://www.freedesktop.org/wiki/Software/systemd/systemd-boot/)
must be used as a boot loader.
Depending on your machine, you need:
- either, to reset your keys to enter into Setup Mode (removing your Microsoft keys!)
- either, to allow changes to your keys from your running system (**possibly**, keeping your Microsoft keys)
These instructions varies on your BIOS, see <https://www.rodsbooks.com/efi-bootloaders/controlling-sb.html#setuputil> for an example.
You can confirm to be in Setup Mode using `bootctl status`, reading `Secure Boot` line, which should show a line similar to: `Secure Boot: no (setup mode)`.
In this context, **note that** `/sys/firmware/efi/efivars/` becomes writeable from your Linux system.
**Bricking your machine in a bad way can happen if this location gets overwritten by a strange command / program.** ^[I already `rm'd -rf` this location once, it was very not funny.]
### Installing your keys
#### Easy way: `sbctl`
`sbctl` has static locations for keys, in nixpkgs, `sbctl` writes to `/etc/secureboot`, so prepare a directory for this location with the **right permissions**.
- Creating keys is: `sbctl create-keys`
- Rotating keys is: `sbctl rotate-keys` (with `sbctl` ≥ 0.10)
For enrollment, first, read the next subsection:
##### Keeping Microsoft keys
If you want to keep Microsoft keys, run:
These prerequisites can be checked via `bootctl status`:
```console
$ sbctl enroll-keys --microsoft
$ bootctl status
System:
Firmware: UEFI 2.70 (Lenovo 0.4720)
Secure Boot: disabled (disabled)
TPM2 Support: yes
Boot into FW: supported
Current Boot Loader:
Product: systemd-boot 251.7
...
```
It will include Microsoft Corporation UEFI CA 2011 certificate.
In the `bootctl` output, the firmware needs to be `UEFI` and the
current boot loader needs to be `systemd-boot`. If this is the case,
you are all set to continue.
It does not guarantee that everything will work out of the box, it may be the case you have other certificates that should be included from your OEM which are not distributed in `sbctl`.
## Part 1: Preparing Your System
Therefore, please double check everything until this project can provide better guarantees.
In the first part, we will prepare everything on the software side of
things. At the end of this part, you will have your own Secure Boot
keys and a NixOS that has signed boot binaries.
##### Ignoring Microsoft keys
### Finding the UEFI System Partition (ESP)
If you want to **remove** Microsoft keys, you have very good reasons to do so (i.e. not trusting Microsoft to not give a valid certificate to OEM which could pose risk to your threat model), run:
The UEFI boot process revolves around a special partition on the
disk. This partition is called _ESP_, the (U)EFI System
Partition. This partition is by convention mounted at `/boot` on NixOS
and the rest of this document assumes this.
```
$ sbctl enroll-keys --yes-this-might-brick-my-machine
You can verify that `/boot` is the ESP by looking for `ESP:` in
`bootctl status` output.
### Creating Your Keys
To create Secure Boot keys, we use `sbctl`, a popular Secure Boot Key
Manager. `sbctl` is available in
[Nixpkgs](https://github.com/NixOS/nixpkgs) as `pkgs.sbctl`.
Once you have installed sbctl (or entered a Nix shell), creating your
Secure Boot keys requires this command:
```console
$ sudo sbctl create-keys
[sudo] password for julian:
Created Owner UUID 8ec4b2c3-dc7f-4362-b9a3-0cc17e5a34cd
Creating secure boot keys...✓
Secure boot keys created!
```
The authors of this project declines all responsibility for running this command and bricking your machine, this is **experimental** SecureBoot.
This takes a couple of seconds. When it is done, your Secure Boot keys
are located in `/etc/secureboot`. `sbctl` sets the permissions of the
secret key so that only root can read it.
#### Harder ways: follow the Archlinux Wiki
### Switching to bootspec
Read about this on <https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot#Enrolling_keys_in_firmware>.
Lanzatool currently doesn't handle
non-[bootspec](https://github.com/grahamc/rfcs/blob/bootspec/rfcs/0125-bootspec.md)
generations well
([#55](https://github.com/nix-community/lanzaboote/issues/55)). As
such, we need to switch to bootspec and get rid of all previous
generations before we can continue.
## Using the `Lanzaboote` project in your NixOS configuration
Bootspec is currently available as preview in nixpkgs unstable. To
enable bootspec, set `boot.bootspec.enable = true;` in your system
configuration, rebuild and reboot.
**Disclaimer** : `Lanzaboote` requires [RFC-0125 aka bootspec](https://github.com/NixOS/rfcs/pull/125) on your system, this is automatically enabled on your behalf.
When everything is working, you can garbage collect your old
non-bootspec generations: `nix-collect-garbage -d`.
**Warning** : `Lanzaboote` is compatible only with `systemd-boot` for now, also, it replaces `boot.loader.systemd-boot` and has no feature parity with this NixOS module.
🔪 **Sharp edge:** 🔪 This will leave old boot entries lying around in
the ESP. `systemd-boot` will display these during boot. This can be
confusing during boot. **After you made a backup of your ESP**, you
may delete these entries in `/boot/loader/entries`.
Use your favorite way to import this project in your configuration, i.e. Flakes or [niv](https://github.com/nmattia/niv) or `fetchFromGitHub`:
### Configuring NixOS (with Flakes)
### `fetchFromGitHub`
Below is a fragment of a NixOS configuration that enables the Secure
Boot stack.
```
{ pkgs, config, lib, ... }:
{
imports = [
(pkgs.fetchFromGitHub {
owner = "nix-community";
repo = "lanzaboote";
rev = "relevant-revision";
sha256 = lib.fakeHash;
})
];
}
```
```nix
nixosConfigurations = {
yourHost = nixpkgs.lib.nixosSystem {
system = "x86_64-linux";
---
modules = [
# ... other modules ...
Now, assuming the NixOS module is imported, you only need to have:
lanzaboote.nixosModules.lanzaboote
```
{ pkgs, config, lib, ... }: {
boot.lanzaboote = {
enable = true;
publicKeyFile = "/etc/secureboot/keys/db/db.pem"; # DB public key
privateKeyFile = "/etc/secureboot/keys/db/db.key"; # DB private key
({ config, pkgs, lib, ... }: {
# This should already be here from switching to bootspec earlier.
# It's not required anymore, but also doesn't do any harm.
boot.bootspec.enable = true;
environment.systemPackages = [
# For debugging and troubleshooting Secure Boot.
pkgs.sbctl
];
# Lanzaboote currently replaces the sytemd-boot module.
# This setting is usually set to true in configuration.nix
# generated at installation time. So we force it to false
# for now.
boot.loader.systemd-boot.enable = lib.mkForce false;
boot.lanzaboote = {
enable = true;
pkiBundle = "/etc/secureboot";
};
})
];
};
}
```
Different options can be added:
After you rebuild your system, check `sbctl verify` output:
- `boot.lanzaboote.pkiBundle`: provide the whole PKI bundle generated by `sbctl create-keys`, useful when you want to automate key enrollment, **security warning**: those will be copied at system activation in `/tmp/pki` to perform the enrollment because `sbctl` do not support dynamic arbitrary paths for now.
- `boot.lanzaboote.enrollKeys`: perform automatic enrollment key, if needed, at each rebuild
```console
$ sudo sbctl verify
Verifying file database and EFI images in /boot...
✓ /boot/EFI/BOOT/BOOTX64.EFI is signed
✓ /boot/EFI/Linux/nixos-generation-355.efi is signed
✓ /boot/EFI/Linux/nixos-generation-356.efi is signed
✓ /boot/EFI/nixos/0n01vj3mq06pc31i2yhxndvhv4kwl2vp-linux-6.1.3-bzImage.efi is signed
✓ /boot/EFI/systemd/systemd-bootx64.efi is signed
```
## Known limitations
🔪 **Sharp edge:** 🔪 In case something is **not** signed in the
`sbctl verify` output, you have hit a bug
([#39](https://github.com/nix-community/lanzaboote/issues/39)). You
**have to fix this** to avoid ending up with an unbootable system
([#58](https://github.com/nix-community/lanzaboote/issues/58)). The
way to solve this is **deleting** the unsigned files indicated by
`sbctl` and switching to the configuration again. This will copy and
sign the missing files.
- Generations are shown improperly because `/etc/os-release` induces the wrong name in the `systemd-boot` menu according to this algorithm: <>
- `$esp/nixos` is a hardcoded path to store initrds & kernels
- The lifecycle between disabling Lanzaboote and getting back into Lanzaboote is not clear
- No TPM event logging & measurements is taking place
- Alternative Nix store locations are not supported
- PKCS#11 engine support is not available
## Part 2: Enabling Secure Boot
Now that NixOS is ready for Secure Boot, we will setup the
firmware. At the end of this section, Secure Boot will be enabled on
your system and your firmware will only boot binaries that are signed
with your keys.
These instructions are specific to Thinkpads and may need to be
adapted on other systems.
### Entering Secure Boot Setup Mode
The UEFI firmware allows enrolling Secure Boot keys when it is in
_Setup Mode_.
On a Thinkpad enter the BIOS menu using the "Reboot into Firmware"
entry in the systemd-boot boot menu. Once you are in the BIOS menu:
1. Select the "Security" tab.
2. Select the "Secure Boot" entry.
3. Set "Secure Boot" to enabled.
4. Select "Reset to Setup Mode".
5. Select "Clear All Secure Boot Keys".
When you are done, press F10 to save and exit.
You can see these steps as a video [here](https://www.youtube.com/watch?v=aLuCAh7UzzQ).
### Enrolling Keys
Once you've booted your system into NixOS again, you have to enroll
your keys to activate Secure Boot. We include Microsoft keys here to
avoid boot issues.
```console
$ sudo sbctl enroll-keys --microsoft
Enrolling keys to EFI variables...
With vendor keys from microsoft...✓
Enrolled keys to the EFI variables!
```
You can now reboot your system. After you've booted, Secure Boot is
activated:
```console
$ bootctl status
System:
Firmware: UEFI 2.70 (Lenovo 0.4720)
Firmware Arch: x64
Secure Boot: enabled (user)
TPM2 Support: yes
Boot into FW: supported
```
That's all! 🥳
## Disabling Secure Boot and Lanzaboote
When you want to get back to a system without the Secure Boot stack,
**first** disable Secure Boot in your firmware settings. Then you can
disable the Lanzaboote related settings in the NixOS configuration and
rebuild.
You may need to clean up the `EFI/Linux` directory in the ESP manually
to get rid of stale boot entries. **Please backup your ESP, before you
delete any files** in case something goes wrong.
## Alternatives
The [ArchLinux wiki](https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot)
contains alternatives to handling your keys, in case `sbctl` is not
flexible enough.