mirror of
https://github.com/QubesOS/qubes-doc.git
synced 2024-12-26 07:49:34 -05:00
249 lines
8.9 KiB
Markdown
249 lines
8.9 KiB
Markdown
---
|
|
lang: en
|
|
layout: doc
|
|
permalink: /doc/yubikey/
|
|
redirect_from:
|
|
- /doc/yubi-key/
|
|
- /en/doc/yubi-key/
|
|
- /doc/YubiKey/
|
|
ref: 169
|
|
title: YubiKey
|
|
---
|
|
|
|
"The YubiKey is a hardware authentication device manufactured by Yubico to
|
|
protect access to computers, networks, and online services that supports
|
|
one-time passwords (OTP), public-key cryptography, and authentication, and the
|
|
Universal 2nd Factor (U2F) and FIDO2 protocols[1] developed by the FIDO
|
|
Alliance." ([Wikipedia](https://en.wikipedia.org/wiki/YubiKey))
|
|
|
|
## General usage in Qubes OS
|
|
|
|
Most use cases for the YubiKey can be achieved exactly as described by the
|
|
manufacturer or other instructions found online. One usually just needs to
|
|
attach the YubiKey to the corresponding app qube to get the same result (see the
|
|
documentation on how to use [USB devices](/doc/how-to-use-usb-devices/) in Qubes
|
|
OS accordingly). The recommended way for using U2F in Qubes is described
|
|
[here](https://www.qubes-os.org/doc/u2f-proxy/).
|
|
|
|
## Multi-factor login for Qubes OS
|
|
|
|
You can use a YubiKey to enhance the user authentication in Qubes. The following
|
|
instructions explain how to setup the YubiKey as an *additional* way to login.
|
|
|
|
After setting it up, you can login by providing both - a password typed in via
|
|
keyboard *and* the YubiKey plugged in. Someone eavesdropping your login attempt
|
|
would not be able to login by only observing and remembering your password.
|
|
Stealing your YubiKey would not suffice to login either. Only if an attacker has
|
|
both, the password and the Yubikey, it would be possible to login (it is thus
|
|
called [Multi-factor
|
|
authentication](https://en.wikipedia.org/wiki/Multi-factor_authentication)).
|
|
|
|
The following instructions keep your current login password untouched and
|
|
recommends to define a new, additional password that is used in combination with
|
|
the YubiKey only. This ensures that you a) do not accidentally lock yourself out
|
|
during setup and b) you do not need to fear [shoulder
|
|
surfing](https://en.wikipedia.org/wiki/Shoulder_surfing_(computer_security)) so
|
|
much (i.e. by not using your standard login password in public).
|
|
|
|
### Setup login with YubiKey
|
|
|
|
To use the YubiKey for multi-factor authentication you need to
|
|
|
|
* install software for the YubiKey,
|
|
* configure the YubiKey for the
|
|
[Challenge-Response](https://en.wikipedia.org/wiki/Challenge%E2%80%93response_authentication)
|
|
mode,
|
|
* store the password for YubiKey Login and the Challenge-Response secret in
|
|
dom0,
|
|
* enable YubiKey authentication for every service you want to use it for.
|
|
|
|
All these requirements are described below, step by step.
|
|
|
|
1. Install YubiKey software in the template on which your USB VM is based.
|
|
Without this software the challenge-response mechanism is not working.
|
|
|
|
For Fedora.
|
|
|
|
```
|
|
sudo dnf install ykpers
|
|
```
|
|
|
|
For Debian.
|
|
|
|
```
|
|
sudo apt-get install yubikey-personalization
|
|
```
|
|
|
|
Shut down your template. Then, either reboot your USB VM (so changes inside
|
|
the template take effect in your USB app qube) or install the packages inside
|
|
your USB VM as well if you would like to avoid rebooting it.
|
|
|
|
2. Install [qubes-app-yubikey](https://github.com/QubesOS/qubes-app-yubikey) in
|
|
dom0. This provides the program to authenticate with password and YubiKey.
|
|
|
|
```
|
|
sudo qubes-dom0-update qubes-yubikey-dom0
|
|
```
|
|
|
|
3. Configure your YubiKey for challenge-response `HMAC-SHA1` mode. This can be
|
|
done on any qube, e.g. a disposable (you need to [attach the
|
|
YubiKey](https://www.qubes-os.org/doc/how-to-use-usb-devices/) to this app qube
|
|
though) or directly on the sys-usb vm.
|
|
|
|
You need to (temporarily) install the package "yubikey-personalization-gui" and
|
|
run it by typing `yubikey-personalization-gui` in the command line.
|
|
|
|
- In the program go to `Challenge-Response`,
|
|
- select `HMAC-SHA1`,
|
|
- choose `Configuration Slot 2`,
|
|
- optional: enable `Require user input (button press)` (recommended),
|
|
- use `fixed 64 bit input` for `HMAC-SHA1 mode`,
|
|
- insert the YubiKey (if not done already) and make sure that it is attached
|
|
to the vm,
|
|
- press `Write Configuration` once you are ready.
|
|
|
|
We will refer the `Secret Key (20 bytes hex)` as `AESKEY`.
|
|
|
|
- It is recommended to keep a backup of your `AESKEY` in an offline VM used as a vault.
|
|
- Consider keeping a backup of your `AESKEY` on paper and storing it in a safe place.
|
|
- If you have multiple YubiKeys for backup purposes (in case a yubikey gets
|
|
lost, stolen or breaks) you can write the same settings into other
|
|
YubiKeys. You can choose "Program multiple YubiKeys" in the program, make sure
|
|
to select `Same secret for all keys` in this case.
|
|
|
|
4. Paste your `AESKEY` into `/etc/qubes/yk-keys/yk-secret-key.hex` in dom0.
|
|
|
|
5. As mentioned before, you need to define a new password that is only used in
|
|
combination with the YubiKey. You can write this password in plain text into
|
|
`/etc/qubes/yk-keys/yk-login-pass` in dom0. This is considered safe as dom0 is
|
|
ultimately trusted anyway.
|
|
|
|
However, if you prefer you can paste a hashed password instead into
|
|
`/etc/qubes/yk-keys/yk-login-pass-hashed.hex` in dom0.
|
|
|
|
You can calculate your hashed password using the following two commands.
|
|
First run the following command to store your password in a temporary variable `password`.
|
|
(This way your password will not leak to the terminal command history file.)
|
|
|
|
```
|
|
read -r password
|
|
```
|
|
|
|
Now run the following command to calculate your hashed password.
|
|
|
|
```
|
|
echo -n "$password" | openssl dgst -sha1 | cut -f2 -d ' '
|
|
```
|
|
|
|
6. To enable multi-factor authentication for a service, you need to add
|
|
|
|
```
|
|
auth include yubikey
|
|
```
|
|
|
|
to the corresponding service file in `/etc/pam.d/` in dom0. This means, if
|
|
you want to enable the login via YubiKey for xscreensaver (the default screen
|
|
lock program), you add the line at the beginning of `/etc/pam.d/xscreensaver`.
|
|
If you want to use the login for a tty shell, add it to `/etc/pam.d/login`. Add
|
|
it to `/etc/pam.d/lightdm` if you want to enable the login for the default
|
|
display manager and so on.
|
|
|
|
It is important, that `auth include yubikey` is added at the beginning of
|
|
these files, otherwise it will most likely not work.
|
|
|
|
7. Adjust the USB VM name in case you are using something other than the default
|
|
`sys-usb` by editing `/etc/qubes/yk-keys/yk-vm` in dom0.
|
|
|
|
### Usage
|
|
|
|
When you want to authenticate
|
|
|
|
1. plug your YubiKey into an USB slot,
|
|
2. enter the password associated with the YubiKey,
|
|
3. press Enter and
|
|
4. press the button of the YubiKey, if you configured the confirmation (it will
|
|
blink).
|
|
|
|
When everything is ok, your screen will be unlocked.
|
|
|
|
In any case you can still use your normal login password, but do it in a secure
|
|
location where no one can snoop your password.
|
|
|
|
### Optional: Enforce YubiKey Login
|
|
|
|
Edit `/etc/pam.d/yubikey` (or appropriate file if you are using other screen locker program) and remove `default=ignore` so the line looks like this.
|
|
|
|
```
|
|
auth [success=done] pam_exec.so expose_authtok quiet /usr/bin/yk-auth
|
|
```
|
|
|
|
### Optional: Locking the screen when YubiKey is removed
|
|
|
|
Look into it
|
|
You can setup your system to automatically lock the screen when you unplug your YubiKey.
|
|
This will require creating a simple qrexec service which will expose the ability to lock the screen to your USB VM, and then adding a udev hook to actually call that service.
|
|
|
|
In dom0:
|
|
|
|
1. First configure the qrexec service.
|
|
Create `/etc/qubes-rpc/custom.LockScreen` with a simple command to lock the screen.
|
|
In the case of xscreensaver (used in Xfce) it would be:
|
|
|
|
```
|
|
DISPLAY=:0 xscreensaver-command -lock
|
|
```
|
|
|
|
2. Then make `/etc/qubes-rpc/custom.LockScreen` executable.
|
|
|
|
```
|
|
sudo chmod +x /etc/qubes-rpc/custom.LockScreen
|
|
```
|
|
|
|
3. Allow your USB VM to call that service.
|
|
Assuming that it's named `sys-usb` it would require creating `/etc/qubes-rpc/policy/custom.LockScreen` with:
|
|
|
|
```
|
|
sys-usb dom0 allow
|
|
```
|
|
|
|
In your USB VM:
|
|
|
|
3. Create udev hook.
|
|
Store it in `/rw/config` to have it persist across VM restarts.
|
|
For example name the file `/rw/config/yubikey.rules`.
|
|
Add the following line:
|
|
|
|
```
|
|
ACTION=="remove", SUBSYSTEM=="usb", ENV{ID_SECURITY_TOKEN}=="1", RUN+="/usr/bin/qrexec-client-vm dom0 custom.LockScreen"
|
|
```
|
|
|
|
4. Ensure that the udev hook is placed in the right place after VM restart.
|
|
Append to `/rw/config/rc.local`:
|
|
|
|
```
|
|
ln -s /rw/config/yubikey.rules /etc/udev/rules.d/
|
|
udevadm control --reload
|
|
```
|
|
|
|
5. Then make `/rw/config/rc.local` executable.
|
|
|
|
```
|
|
sudo chmod +x /rw/config/rc.local
|
|
```
|
|
|
|
6. For changes to take effect, you need to call this script manually for the first time.
|
|
|
|
```
|
|
sudo /rw/config/rc.local
|
|
```
|
|
|
|
If you use KDE, the command(s) in first step would be different:
|
|
|
|
```
|
|
# In the case of USB VM being autostarted, it will not have direct access to D-Bus
|
|
# session bus, so find its address manually:
|
|
kde_pid=`pidof kdeinit4`
|
|
export `cat /proc/$kde_pid/environ|grep -ao 'DBUS_SESSION_BUS_ADDRESS=[[:graph:]]*'`
|
|
qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock
|
|
```
|