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Add in support for using a preshared key
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Update documentation and initcpio scripts.
Move to MAJOR.MINOR.COMMITS for versioning.

-=david=-

closes #4
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dharrigan committed Jul 23, 2023
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252 changes: 192 additions & 60 deletions README.adoc
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= mkinitcpio Wireguard hook
= mkinitcpio WireGuard hook
:author: David Harrigan
:email: <dharrigan [@] gmail [dot] com>
:docinfo: true
Expand All @@ -22,17 +22,35 @@ endif::[]

== ChangeLog

IMPORTANT: Until this package has stabilised and until it has reached a 1.0.0
release, *please be very careful* to examine the version changes listed below
as the package requirements and instructions can change to reflect a better
[IMPORTANT]
====
This project follows the version scheme **MAJOR.MINOR.COMMITS** where
**MAJOR** and **MINOR** provide some relative indication of the size of the
change, but do **NOT** follow semantic versioning. In general, all changes
endeavour to be non-breaking (by moving to new names rather than by breaking
existing names). **COMMITS** is an ever-increasing counter of commits since
the beginning of this repository.
====

[IMPORTANT]
====
Until this package has stabilised and until it has reached a 1.0.0 release,
*please be very careful* to examine the version changes listed below as the
package requirements and instructions can change to reflect a better
understanding of the problem domain. *DO NOT ASSUME THAT ANYTHING UNTIL AT
LEAST A 1.0.0 RELEASE*

WARNING: Read the warning above.
====

|===
|Version | Note

| *0.5.11*
a|
* Added in support for using WireGuard a preshared key (closes #4).
* Improved the documentation.
* Improved the initcpio support files.
* Change versioning to be MAJOR.MINOR.COMMITS.

| *0.4.10*
a|
* Improved documentation. No functional changes.
Expand Down Expand Up @@ -63,49 +81,58 @@ a|

== Rationale

Firstly, encryption. Encrypt all the things.
**Firstly**, encryption. **Encrypt all the things!**

Secondly, I think https://www.wireguard.io[Wireguard] is pretty awesome. It's
**Secondly**, I think https://www.wireguard.io[Wireguard] is pretty awesome. It's
really easy to setup and use and works flawlessly (at least for me 😄).

Thirdly, the ability to remotely unlock encrypted partitions is extremely
**Thirdly**, the ability to remotely unlock encrypted partitions is extremely
useful. However, a limitation is that in order to remotely unlock the
partition via SSH, you normally need to be on the same network (or at least
routeable) to the computer that needs unlocking.

As far as I could tell, there was nothing available in
https://aur.archlinux.org[AUR] that provided a Wireguard hook for
`mkinitcpio`. Creating a hook should allow a basic Wireguard interface to be
https://aur.archlinux.org[AUR] that provided a WireGuard hook for
`mkinitcpio`. Creating a hook should allow a basic WireGuard interface to be
established so that - via a secure network - you could gain access to the
remote machine. This is my small attempt to achieve that aim.
remote computer. This is my small attempt to achieve that aim.

IMPORTANT: I developed this little hook for myself and I'm releasing it into
[IMPORTANT]
====
I developed this little hook for myself and I'm releasing it into
the general community in the (probably misguided) hope that others may find it
useful too. As usual, no warranty implied or otherwise is given towards the
fitness of this software in meeting *YOUR* needs. Please refer to the included
https://unlicense.org[Unlicense] license file for more information. That said,
I find this little hook useful - perhaps you may too - so please enjoy! Oh,
and please be be awesome to each other!
====

WARNING: Ensure you have read the Arch wiki section on
[WARNING]
====
Ensure you have read the Arch wiki section on
https://wiki.archlinux.org/index.php/Dm-crypt/Specialties#Remote_unlocking_of_the_root_(or_other)_partition[remote
unlocking]. It's a *very* good idea to get remote unlocking working *first* on
your local network - proving that it works for you (this includes using either
*tinyssh* or *dropbear* to authenticate and unlock successfully)
- *before* attempting to setup this mkinitcpio Wireguard hook for remote
- *before* attempting to setup this mkinitcpio WireGuard hook for remote
unlocking.
====

IMPORTANT: It is also *strongly* recommend that a *separate* Wireguard network
[IMPORTANT]
====
It is also *strongly* recommend that a *separate* WireGuard network
is setup and configured *just* for unlocking. You see, a private key (and a
public key) and a configuration file are written to the ramdisk (which
typically lives in an unencrypted boot partition). It's super trivially easy
for anyone to copy this ramdisk, extract out the contents and use the private
key and Wireguard configuration found therein to connect to your Wireguard
key and WireGuard configuration found therein to connect to your WireGuard
network. As a minimum, you could disable (on the remote peer *nominally called
the `server`*) the ability for the target machine (the `client` - the one on
the `server`*) the ability for the target computer (the `client` - the one on
which you are remotely unlocking partitions) to connect and authenticate -
only enabling connection *when* and *if* required. Please be careful and think
this through! Safety first!
====

== OS Installation

Expand All @@ -117,10 +144,12 @@ https://github.com/Jguer/yay[yay] package manager to install the utility.
Please refer to your favourite package manager's documentation in learn how to
install it for you 😄

NOTE: Obviously, you must also install Wireguard! Choose either manual
installation (using git and compiling it yourself), or using
`wireguard-tools`. Life is short, so personally I just roll with
`wireguard-tools`.
[NOTE]
====
Obviously, you must also install WireGuard! Choose either manual installation
(using git and compiling it yourself), or using `wireguard-tools`. Life is
short, so personally I just roll with `wireguard-tools`.
====

== Additional Requirements

Expand All @@ -129,14 +158,14 @@ This software requires a few necessary additions:
* `mkinitcpio-utils`
* `mkinitcpio-netconf`

These packages provide the means to configure the network interface
via passed in kernel parameters and the ability to ssh to the machine
remotely. Basic instructions follow:
These packages provide the means to configure the network interface via passed
in kernel parameters and the ability to ssh to a remote computer. Basic
instructions follow.

You will need to choose been `mkinitcpio-tinyssh` or
`mkinitcpio-dropbear` and install one or the other. This documentation
describes only `mkinitcpio-tinyssh` as it supports ed25519 and I quite
like it.
like it (both ed25519 and tinyssh).

* `mkinitcpio-tinyssh`
* `mkinitcpio-dropbear`
Expand All @@ -153,75 +182,164 @@ below on `Hook Installation` for the module ordering for
This package sets up the interfaces just immediately after booting the
kernel based upon the IP parameters passed into the kernel via GRUB.
This is very important as this sets thing up in order for tinyssh (or
dropbear) and wireguard to function. For example, in your
dropbear) and WireGuard to function. For example, in your
`/etc/default/grub` file, the `GRUB_CMDLINE_LINUX` line may look like
this:

```
GRUB_CMDLINE_LINUX="cryptdevice=UUID=35fbb65a-eeb9-4a6a-7b13-a05d9b0fcf6f:cryptroot root=/dev/mapper/cryptroot ip=192.168.1.10:192.168.1.1:255.255.255.0::eth0::"
GRUB_CMDLINE_LINUX="cryptdevice=UUID=35fbb65a-eeb9-4a6a-7b13-a05d9b0fcf6f:cryptroot root=/dev/mapper/cryptroot ip=192.168.1.10::192.168.1.1:255.255.255.0::eth0::"
```

This says to use the cryptdevice defined by the UUID, which will map
itself to `cryptoroot` after successful unlocking and also set the IP
parameters on the kernel, i.e., host = 192.168.1.10, gateway =
192.168.1.1, netmask = 255.255.255.0, and kernel network interface
eth0.
This says to use the cryptdevice defined by the UUID, which will map itself to
`cryptoroot` after successful unlocking and also set the IP parameters on the
kernel, i.e., `host=192.168.1.10`, `gateway=192.168.1.1`, `netmask =
255.255.255.0`, and kernel network interface `eth0`.

Further information on the ip kernel parameter can be found
https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/nfs/nfsroot.rst[here].

IMPORTANT: Use the **kernel** device name, i.e., **eth0**, and not the
well known predictable name, such as **enp0s31f6**.
[WARNING]
====
Use the **kernel** device name, i.e., **eth0**, and not the well known
predictable name, such as **enp0s31f6**.
====

=== mkinitcpio-tinyssh (or mkinitcpio-dropbear)

This package installs `tinyssh` to allow SSH connections. It's small
enough to fit into the daemon into the early userspace and allows for
the use of ed25519 keys (which are great!)

The steps here are:
[TIP]
====
Please refer to the Arch wiki on
https://wiki.archlinux.org/title/Dm-crypt/Specialties#Remote_unlocking_of_root_(or_other)_partition[remote
unlocking] for additional background reading.
====

. Create an ed25519 keypair using openssh, i.e., `ssh-keygen -t ed25519`
. Copy the public key to `/etc/tinyssh/root_key`
[NOTE]
====
The following steps assume you are on the computer which is encrypted and you'll want to remote boot
and that you are currently the `root` user.
====

== Configuration
The steps are:

* Create an `ed25519` keypair using openssh, i.e., `ssh-keygen -t ed25519`

[NOTE]
====
Any name will do, but we'll assume `server` as the keypair name (thus `server`
and `server.pub` `ed25519` keyfiles are created)
====

* Copy the `server.pub` keyfile to `/etc/tinyssh/root_key` (file)
* Remove the existing `/etc/tinyssh/sshkeydir` directory, i.e., `rm -rf /etc/tinyssh/sshkeydir`
* Generate a tinyssh compatible private key using `tinyssh-convert /etc/tinyssh/sshkeydir < server`

[NOTE]
====
The `server` file is the *private* `ed25519` keyfile that was generated a moment ago
====

* Don't forget to copy the `ed25519` private key to the local computer from which you want to ssh *from*!
** i.e., copy the `server` private keyfile to your local computer, perhaps put it in your `$HOME/.ssh` directory
* It may be useful to add an entry to your personal `$HOME/.ssh/config` along the lines of:

----
host server
hostname ip-address-of-the-remote-encrypted-computer-wireguard-interface
user root
IdentityFile ~/.ssh/ed25519_private_key_of_the_remote_encrypted_computer
----

For example, based upon the example `wireguard_config` file in this repository:

----
host server
hostname 10.0.200.21
user root
IdentityFile ~/.ssh/server
----

IMPORTANT: The setup and running of `mkinitcpio-wireguard` is *very* basic and
makes *lots* of assumptions. *This is intentional!* This hook is simple
because it is designed to get a minimal Wireguard up and running so that you
can remotely unlock encrypted partitions. The script does not attempt to do
anything else. This script will never be super fancy or clever.
== Configuration

WARNING: Please read and familiarise yourself with how Wireguard works. In
particular, please refer to the *numerous* examples online of how to setup and
configure Wireguard. It is *strongly* suggested you get Wireguard up and
running first. A few examples of where to find documentation are listed below:
[IMPORTANT]
====
The setup and running of `mkinitcpio-wireguard` is *very* basic and makes
*lots* of assumptions. *This is intentional!* This hook is simple because it
is designed to get a minimal WireGuard up and running so that you can remotely
unlock encrypted partitions. The script does not attempt to do anything else.
This script will never be super fancy or clever.
====

[WARNING]
====
Please read and familiarise yourself with how WireGuard works. In particular,
please refer to the *numerous* examples online of how to setup and configure
WireGuard. It is *strongly* suggested you get WireGuard up and running first.
A few examples of where to find documentation are listed below.
====

* https://wiki.archlinux.org/index.php/WireGuard
* https://www.wireguard.com/quickstart/
* https://git.zx2c4.com/WireGuard/about/src/tools/man/wg.8

After installing `mkinitcpio-wireguard`, an example configuration file will be
written to `/etc/wireguard/initcpio/unlock`. You *MUST* edit this file to suit
your particular Wireguard requirements. The file is really simple and
your particular WireGuard requirements. The file is really simple and
therefore should be pretty self-explanatory.

NOTE: If you have an existing `wg0.conf` in your `/etc/wireguard` directory,
[NOTE]
====
If you have an existing `wg0.conf` in your `/etc/wireguard` directory,
you can use the contents of that file as a reference. Please be aware of the
warning above concerning the recommended use of a separate network for remote
unlocking.
====

=== Configuration Keys

The current configuration keys found in the configuration file are:

|===
|Key | Description

|**INTERFACE**| Specifies the name of the WireGuard interface (usually wg0).
|**INTERFACE_ADDR**|Specifies the IP address that the WireGuard interface will use. Please ensure you specify the IP address in CIDR format.
|**PEER_PUBLIC_KEY**|This is the public key of the peer (usually the WireGuard server).
|**PEER_ENDPOINT**|This is normally the external public-facing IP address and port of the peer (usually the WireGuard server), but it may also be an internal IP address and port of a peer if you wish!
|**PRIVATE_KEYFILE**|This is your private key previously setup to establish connection to the peer (usually the WireGuard server).
|**PRESHARED_KEYFILE**|**OPTIONAL**
This is the preshared key to be used. Don't forget to populate the preshared
keyfile using something like:

`umask 077 && wg genpsk > /etc/wireguard/initcpio/presharedkey`

and that the preshared key matches on the other peer too!
|**PERSISTENT_KEEPALIVES**|If you're behind a NAT, a ping of 25 seconds is useful to keep the connection alive between the peers.
|**ALLOWED_IPS**|The IP range that will be allowed to flow across the wg0 interface.

|===

== Hook Installation

After you have edited the `/etc/wireguard/initcpio/unlock` file to suit your
needs, ensure that you've added the `wireguard` hook to the *HOOKS* array of
`/etc/mkinitcpio.conf`. Shown below is an example that also includes the use
of `netconf`, `tinyssh` and `encryptssh`.
needs, the next step is ensure that you've added the `wireguard` hook to the
*HOOKS* array of `/etc/mkinitcpio.conf`. Shown below is an example that also
includes the use of `netconf`, `tinyssh` and `encryptssh`

----
HOOKS=(base udev autodetect keyboard keymap modconf block netconf wireguard tinyssh encryptssh filesystems fsck)
----

[NOTE]
====
Your particular original `/etc/mkinitcpio.conf` file may be slightly different
in the hooks already present (and the ordering in which they are presented).
====


== Final Steps

Lastly, run (still as root):
Expand All @@ -230,18 +348,32 @@ Lastly, run (still as root):
mkinitcpio -P
----

This will regenerate the ramdisk with your Wireguard configuration.
This will regenerate the initramfs ramdisk with your WireGuard configuration.
You can safely ignore all the warnings about possibly missing firmware
modules.

You should now be able to reboot your machine and after the interface has come
up be able to ping it via your Wireguard network! You should now also be able
to SSH to the machine (you did remember to set that all up before doing this,
right?) and unlock any encrypted partitions and thus enable the continuation
of your boot process! FTW!
You should now be able to reboot your remote computer and after the interface
has come up be able to ping it via your WireGuard network!

NOTE: It could take a minute or two for your Wireguard interface to
NOTE: It could take a minute or two for your WireGuard interface to
authenticate and be recognised by the remote peer. Please be patient and hang
on in there!

Once you can ping the remote computer, you should now also be able to SSH to
it (you did remember to set that all up before doing this, right?).

After establishing a SSH connection to the remote computer, a prompt should
appear asking for the LUKS passphrase to unlock the encrypted partition. Once
the LUKS passphrase has been keyed in, the partition should unlock and the
continuation of the boot process will continue! FTW!

== Updating the configuration

If you make changes to the `/etc/wireguard/initcpio/unlock` file, or if you
change your private key (and/or optionally the preshared key) don't forget to
regenerate the initramfs ramdisk using `mkinitcpio -P`, otherwise your new
settings won't be picked up!

== Unlicensed

Find the full unlicense in the UNLICENSE file, but here's a snippet.
Expand Down
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