Kubuntu Focus - Security Tools

Full Disk Encryption

Change Password

The first-run wizard will encourage your to change your disk encryption passphrase on the first sign-in if the passphrase matched the default. Whenever you change the password, type it carefully and keep a copy somewhere safe because THERE IS NO WAY TO RECOVER THE DISK IF THE PASSPHRASE IS LOST!

# /dev/nvme0n1p3 is used as an example. # The actual device may vary. sudo cryptsetup luksChangeKey /dev/nvme0n1p3; #> Enter passphrase to be changed: #> Enter new passphrase: #> Verify passphrase:

View Key Slots

Only one key is used for normal encryption, and two if using a YubiKey. You may see the used slots by entering the following command:

sudo cryptsetup luksDump /dev/nvme0n1p3; #> ...

Remove a Passphrase (Carefully!)

If you see more keys than expected, you may remove them. Do this carefully and make sure your data is backed-up before proceeding! In the example below, we remove a key from slot 2.

sudo cryptsetup luksKillSlot /dev/nvme0n1p3 2; #> Enter any remaining passphrase:

Use the luksDump command as shown above to ensure the slot has been removed.

Add a New Passphrase

Use the following command to add a new key:

sudo cryptsetup luksAddKey /dev/nvme0n1p3

YubiKey

If you purchased a pre-configured YubiKey you won’t need this except to change your password. The YubiKey documentation may be found at here.

1. Setup

# Become the root user sudo -i; # Confirm the encrypted partition ls /dev/nvme0n1p3; # Find an open LUKS key slot # Slots 1-7 show as open cryptsetup luksDump /dev/nvme0n1p3;

2. Install Necessary Packages

apt install yubikey-luks

3. Configure YubiKey

Insert the YubiKey into a USB slot. The center LED should flash once. It will not stay illuminated. As you use the key, the LED will flash under other circumstances.

ykpersonalize -2 -ochal-resp \ -ochal-hmac -ohmac-lt64 -oserial-api-visible; #> #> Firmware version 5.2.4 Touch level 1283 Program sequence 3 #> #> Configuration data to be written to key configuration 1: #> #> fixed: m: #> uid: n/a #> key: h:50d779456fb7325fd91f2c543092b5178c4174cd #> acc_code: h:000000000000 #> OATH IMF: h:0 #> ticket_flags: CHAL_RESP #> config_flags: CHAL_HMAC|HMAC_LT64 #> extended_flags: SERIAL_API_VISIBLE # #> Commit? (y/n) [n]: y

4. Create Config File (Optional)

The default /etc/ykluks.cfg file should be fine. However, you may customize it as you see fit.

5. Save LUKS Config to Key Slot

# Enroll to slot. If slot is taken, try the next with -s 2 yubikey-luks-enroll -d /dev/nvme0n1p3 -s 1; #> setting disk to /dev/nvme0n1p3. #> setting slot to 1. #> This script will utilize slot 1 on drive /dev/nvme0n1p3. If this is not what you intended, exit now! #> Adding yubikey to initrd #> Please insert a yubikey and enter a new password. This is the password that will only work while your yubikey is installed in your computer. **************** #> Please enter the yubikey password again: **************** #> You may now be prompted for an existing passphrase. This is NOT the passphrase you just entered, this is the passphrase that you currently use to unlock your LUKS encrypted drive. #> Enter any existing passphrase:

Enter your passphrase.

6. Modify Crypt Table

Modify /etc/crypttab to include the keyscript option as shown. IMPORTANT! THE DISK UUID YOU SEE WILL BE DIFFERENT - DO NOT CHANGE IT! Also make sure the entry is on a single line in the file, even if it wraps in the codeblock below.

nvme0n1p3_crypt UUID=98cfc3a4-dfd8-4cb4-8016-a3a62649d5a0 none luks,keyscript=/usr/share/yubikey-luks/ykluks-keyscript,discard

You can verify or recover the UUID by using lsblk --fs |grep 'crypto_LUKS' and then using the uuid of the correct volume. The partion for standard installations is typically /dev/nvme0n1p3.

7. Update System RAM Disk

# update the initial Ramdisk update-initramfs -u; # Append `-k all` to update all kernels.

8. Reboot and Test

Reboot and insert Yubikey on the initial passphrase screen to test your password. You should be able to use your YubiKey passphrase or your regular passphrase. We suggest you always keep the first passphrase but ensure it is long and complex. This provides a method to use the system even if you lose your Yubikey. As always, store your passphrases safely.

Kleopatra

Kleopatra is a certificate manager and a universal crypto GUI. It supports managing X.509 and OpenPGP certificates in the GpgSM keybox and retrieving certificates from LDAP servers.

Connect with Secure Shell and OpenVPN

Secure Shell (SSH) is a versatile tool. One can use it for remote access, port forwarding, tunneling, and secure file transfers. Many graphical tools support SSH. For example, the Dolphin file manager, can use SFTP for secure file transfers.

A default configuration is provided and annotated in .ssh/config for all new users. You may study it to see how to maintain constant connection and add shortcuts for specific hosts.

OpenVPN is installed to ease connection to Virtual Private Networks used by many organizations. There are also many other VPN clients which are available.

Troubleshooting

Content will be added as needed.

Revisions

This is a partial revision history. See the git repository for all entries.

2022-07-25 37da0b4f Enhance Yubikey directions
2021-10-10 5728326e Reformat to 2-column
2021-09-22 dc862884 Update link and headline colors
2021-08-23 681261b4 Review and update codeblocks
2021-08-20 ca2282bf Add Yubikey details
2021-03-13 e0214298 Update Yubikey; Add autoremove advice
2020-06-10 c4ed9299 Restructure layout
2020-06-08 a963ce3f First publication

Disclaimer

We try hard to provide a useful solution validated by professionals. However, we cannot anticipate every situation, and therefore cannot guarantee this procedure will work for your needs. Always backup your data and test the solution to determine the correct procedure for you.

THIS SOLUTION IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOLUTION, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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