Installer og opsæt CentOS 7 for at fjernlåse LVM på LUKS diskkryptering ved hjælp af SSH

LUKS (Linux Unified Key Setup) er et af de forskellige diskkrypteringsformater, der er tilgængelige for Linux, og som er platformagnostisk. Denne vejledning vil give dig root- og swap-partitioner inde i en LVM (Linux Volume Manager)-volumen indeholdt i en krypteret LUKS-partition. Denne vejledning giver dig også mulighed for at låse LUKS-partitionen op på afstand ved hjælp af en forenklet SSH-server-dæmon ved hjælp af et hvilket som helst kompatibelt SSH-klientprogram.

Forudsætninger

• En CentOS 7 x64 Minimal ISO Library-serverinstans.
• En sudo- bruger.
• SSH offentlige nøgle(r) .
• Dracut-Crypt-SSH .

Trin 1: Miljøopsætning

På siden Implementer servere skal du gøre følgende:

• Vælg din serverplacering i Server Locationsektionen.
• Vælg CentOS7under ISO Libraryfanen i Server Typesektionen.
• Vælg de hardwarespecifikationer, du har brug for, i Server Sizeafsnittet.
• Klik på Deploy Nowknappen.

Brug View Consolemuligheden for at få adgang til VPS-instansen via noVNC-konsollen.

Trin 2: Start CentOS 7 Text Mode Installer

Vælg Install CentOS Linux 7indstillingen.

Tryk på Tabtasten.

Indtast textefter vmlinuz initrd=initrd.img inst.stage2=hd:LABEL=CentOS\x207\x20\86_64 quietså det ser sådan ud vmlinuz initrd=initrd.img inst.stage2=hd:LABEL=CentOS\x207\x20\86_64 quiet textog tryk på Entertasten.

VPS'en starter nu op i teksttilstand CentOS-installationsprogrammet. Du vil se en skærm i noVNC-konsollen som vist på billedet nedenfor.

Trin 3: Konfigurer LVM på LUKS fuld diskkryptering

Brug Alt + Right Arrow Keykombinationen til at navigere til TTY2-konsollen for at skrive kommandoer på kommandolinjen.

Indtast følgende kommandoer nedenfor for at oprette en partition til at indeholde GRUB2-startindlæseren, en ukrypteret /bootpartition og en primær partition, der skal indeholde LUKS-partitionen.

parted -a opt -s /dev/vda mklabel gpt
parted -s /dev/vda unit mb
parted -s /dev/vda mkpart primary 1 3
parted -s /dev/vda name 1 grub
parted -s /dev/vda set 1 bios_grub on
parted -s /dev/vda mkpart primary 3 259
parted -s /dev/vda name 2 boot
parted -s /dev/vda mkpart primary 259 100%
parted -s /dev/vda name 3 root

Indtast følgende kommando for at vise partitionslayoutet.

parted -s /dev/vda print

Fyld derefter den navngivne rootfspartition med pseudo-tilfældige data. Dette vil tage lidt over en halv time at gennemføre.

dd if=/dev/urandom of=/dev/vda3 bs=1M status=progress

På CentOS 7 cryptsetupbruger kommandoerne standardkrypteringen aes-xts-plain64, standardnøglestørrelsen på 256 bit og standardhashen for SHA1. I stedet vil LUKS-partitionen blive oprettet med den mere sikre Serpent-chiffer, med en nøglestørrelse på 512 bit og med Whirlpool-hash.

cryptsetup luksFormat /dev/vda3 -c serpent-xts-plain64 -h whirlpool -s 512

Indtast svarene, når du bliver bedt om det med følgende forespørgsler, tryk derefter på Entertasten:

• Er du sikker? (Skriv store bogstaver ja):YES
• Indtast adgangssætning: strong-password
• Bekræft adgangssætning: strong-password

Valgfrit: Sikkerhedskopier LUKS-partitionshovedet

Advarsel Dette vil tillade root-login og kopiering uden en adgangskodeprompt. Dræb denne SSH-server efter du har hentet /tmp/luks-header-backup.imgfilen.

Gem en kopi af LUKS-partitionshovedet for sikker opbevaring. Dette sikrer, at hvis headeren på din LUKS-partition på en eller anden måde er beskadiget, kan den gendannes. Hvis headeren er beskadiget uden en fungerende sikkerhedskopi, går dine data tabt for altid.

cryptsetup luksHeaderBackup /dev/vda3 --header-backup-file /tmp/luks-header-backup.img

For at kopiere /tmp/luks-header-backup.imgfilen fra serveren skal en SSH-server startes midlertidigt ved at bruge den sikre kopi-eksekverbare scppå en klientvært for at hente den.

Indtast følgende kommando nedenfor for at generere SSH-værtsnøglerne.

sshd-keygen

Indtast følgende kommando nedenfor for at oprette /etc/ssh/sshd_configfilen.

cp /etc/ssh/sshd_config.anaconda /etc/ssh/sshd_config

Indtast følgende kommando nedenfor for at redigere /etc/ssh/sshd_configfilen.

vi /etc/ssh/sshd_config

For at redigere filen skal du trykke på Inserttasten og bruge piletasterne til at navigere til sektioner af filen, der skal redigeres.

I linje et skal du ændre tallet Port 22fra standardværdien af 22til et tilfældigt tal efter dit valg mellem 1025og 65535. (Eksempel: port 25782)

Rul ned til linje nummer tretten, tryk på Endtasten og tryk på Entertasten.

På den næste linje skal du tilføje HostKey /etc/ssh/ssh_host_ed25519_keyog trykke på Entertasten.

På den næste linje skal du tilføje HostKey /etc/ssh/ssh_host_rsa_keyog trykke på Entertasten.

Tryk på Esctasten, skriv :wqog tryk på Entertasten for at gemme filen.

Standardnetværksgrænsefladen eth0skal have en IP-adresse. Indtast følgende kommando nedenfor for at tildele den angivne IP-adresse for din instans til eth0netværksgrænsefladen.

dhclient

Indtast følgende kommando for at få vist den tildelte IP-adresse. IP-adressen vil blive vist umiddelbart efter inetog før netmask. (Eksempel: inet 192.0.2.1netmaske)

ifconfig eth0

Indtast følgende kommando for at starte SSH-serveren.

/usr/sbin/sshd

Hvis du bruger scpkommandoen fra en kommandolinje på en klientmaskine, skal du bruge følgende kommando nedenfor som en skabelon til at hente /tmp/luks-header-backup.imgfilen. Erstat 25782med det faktiske portnummer, der er tildelt i /etc/ssh/sshd_config. Erstat 192.0.2.1med den faktisk tildelte IP-adresse.

scp -P 25782 [email protected]:/tmp/luks-header-backup.img .

Efter hentning af luks-header-backup.imgfilen skal du straks dræbe SSH-serveren ved at skrive kommandoen nedenfor i noVNC-konsolvinduet.

killall sshd

Åbn LUKS-partitionen for at konfigurere den fysiske LVM-volumen, der skal ligge indeni.

cryptsetup luksOpen /dev/vda3 centos

Indtast den tidligere oprettede adgangssætning for at åbne LUKS-partitionen, når du bliver bedt om det, og tryk derefter på Entertasten.

Indtast adgangssætning for /dev/vda3:strong-password

Indtast følgende kommando nedenfor:

ls /dev/mapper

Det vil indeholde følgende filer med navnet centos, control, live-baseog live-rw. Det centoser LUKS-partitionen.

Indtast følgende kommando nedenfor for at oprette den fysiske LVM-diskenhed.

pvcreate /dev/mapper/centos

Når det lykkes, vil du modtage følgende besked:

Physical volume "/dev/mapper/centos" successfully created

Indtast følgende kommando nedenfor for at oprette LVM-volumengruppen.

vgcreate ssd /dev/mapper/centos

Når det lykkes, vil du modtage følgende besked:

Volume group "ssd" successfully created

Indtast følgende kommando nedenfor for at oprette en LVM logisk volumen til en swap-partition. Brug sund bedømmelse til at oprette en swap-partition af den nødvendige størrelse (-L = størrelsen på lydstyrken), baseret på din VPS-instans.

lvcreate -L 1G -n swap ssd

Når det lykkes, vil du modtage følgende besked:

Logical volume "swap" created

Type the following command below to create a LVM logical volume for the root partition. This will use the remaining free space while reserving five percent (5%) to contain LVM snapshots of your logical volumes if you so choose.

lvcreate -l 95%FREE -n root ssd

When successful, you will receive the following message:

Logical volume "root" created

Display the LVM physical volume.

pvdisplay

You will see text in the noVNC console similar to what is pictured in the image below.

Display the LVM volume group.

vgdisplay

You will see text in the noVNC console similar to what is pictured in the image below.

Display the LVM logical volume(s).

lvdisplay

You will see text in the noVNC console similar to what is pictured in the image below.

Type the following command below to deactivate the LVM volume group. This must be completed in order to allow cryptsetup to close the LUKS partition in the next step.

vgchange -a n

When successful, you will receive the following message:

0 logical volume(s) in volume group "ssd" now active

Close the LUKS volume.

cryptsetup luksClose centos

Type the following command below:

ls /dev/mapper

It will contain the following files named control, live-base and live-rw. The centos file, containing the LUKS partition, will be missing to ensure that that it was closed properly.

Type reboot and press the Enter key to reboot.

Step 4: Start The CentOS 7 GUI Mode Installer

Select the Install CentOS Linux 7 option and press the Enter key.

The VPS will now boot into the GUI mode CentOS installer. You will see a screen in the noVNC console like pictured in the image below. Select Install CentOS 7 (1) and press the Enter key.

On the WELCOME TO CENTOS 7 screen, click the blue Continue button (1).

Attention If you're not using the default language of English and the locale of the United States, input your language in the search bar (1). Click on the language (2) and the appropriate locale (3) associated with it. When satisfied, click the blue Continue button (4).

On the INSTALLATION SUMMARY screen, click on INSTALLATION DESTINATION (Automatic partitioning selected) (1) under SYSTEM.

On the INSTALLATION DESTINATION screen, select the I will configure partitioning (1) option under Other Storage Options (Partitioning) and click the blue Done button (2) at the top left of the screen.

On the MANUAL PARTITIONING screen, click on the Unknown expandable accordion (1). It will reveal three partitions named BIOS Boot (vda1), Unknown (vda2) and Encrypted (LUKS) (vda3).

With the BIOS Boot partition highlighted in blue (1), select the checkbox option of Reformat (2) next to the File System: accordion and click the Update Settings button (3).

Click on the Unknown partition (1) so that it is highlighted in blue. Select the checkbox option of Reformat (2) next to the File System: accordion. Select ext2 in the File System: accordion (3), enter /boot in the text field (4) under Mount Point:, enter boot in the text field (5) under Label: and click the Update Settings button (6).

Click on the Encrypted (LUKS) partition (1) so that it is highlighted in blue. Enter the passphrase you created for LUKS partition in Step 3: Setup LVM On LUKS Full Disk Encryption in the Passphrase: text field (2) and click the Unlock button (3).

A new Unknown expandable accordion (1) will appear. It will reveal two partitions named Unknown (ssd-root) and Unknown (ssd-swap).

With the Unknown (ssd-root) partition (1) highlighted in blue, select the checkbox option of Reformat (2) next to the File System: accordion. Select xfs in the File System: accordion (3), enter / in the text field (4) under Mount Point:, enter root in the text field (5) under Label: and click the Update Settings button (6).

Click on the Unknown (ssd-swap) (1) partition so that it is highlighted in blue. Select the checkbox option of Reformat (2) next to the File System: accordion. Select swap in the File System: accordion (3), enter swap in the text field (4) under Label: and click the Update Settings button (5).

Click the blue Done button (1) at the top left of the screen.

A box named SUMMARY OF CHANGES will pop up. Click the Accept Changes button (1). This will bring you back to the WELCOME TO CENTOS 7 screen.

Click on NETWORK & HOST NAME (Not connected) (1) under SYSTEM.

On the NETWORK & HOST NAME screen, move the slider (1), next to the right of Ethernet(eth0) field, from the OFF position to the ON position. If you want to use a custom hostname instead of the default (192.0.2.1.vultr.com) in the Host name: text box (2), change it. Click the blue Done button (3) at the top left of the screen. This will bring you back to the WELCOME TO CENTOS 7 screen.

When you are satisfied with the options on the WELCOME TO CENTOS 7 screen, click the blue Begin Installation button (1).

On the CONFIGURATION screen, click on ROOT PASSWORD (Root password is not set) (1) under USER SETTINGS.

On the ROOT PASSWORD screen, enter a strong password in both the Root Password: (1) and Confirm: (2) text fields. Click the blue Done button (3) at the top left of the screen. This will bring you back to the CONFIGURATION screen.

On the CONFIGURATION screen, click on USER CREATION (No user will be created) (1) under USER SETTINGS.

On the CREATE USER screen, enter your full name in the Full name text field (1), an username in the User name text field (2), a strong password in both the Password (3) and Confirm password (4) text fields. Click on the Advanced... button (5).

A box named ADVANCED USER CONFIGURATION will pop up. In the Add user to the following groups: text field (1) under Group Membership, enter wheel and click the Save Changes button (2).

Click the blue Done button (1) at the top left of the screen.

The post-installation process will now commence. It will take a few minutes to complete. When it is finished, click on the blue Reboot button (1) to reboot your VPS instance.

Navigate back to the VULTR Server Management Screen. Click on the Settings link at the top. Click on Custom ISO on the menu on the left side. On the Custom ISO page, click on the Remove ISO button to unmount the ISO and reboot into your CentOS 7 VPS instance. Click the OK button when prompted and the VPS instance will reboot.

Navigate back to the View Console window to access the VPS instance via the noVNC console. Refresh the window if noVNC has disconnected.

You will be prompted to enter the passphrase (Example: Please enter passphrase for disk primary (luks-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)!:) you created for LUKS partition in Step 3: Setup LVM On LUKS Full Disk Encryption. Enter the passphrase and press the Enter key.

You will then be presented with the console login prompt. You can now close the noVNC console window.

Step 5: Update The System

Log in via SSH with a regular user and update the system as follows.

sudo yum install epel-release -y
sudo yum clean all && sudo yum update -y

Step 6: Install Dracut-Crypt-SSH

While still logged in as a regular user, type the following commands below to install dracut-crypt-ssh.

sudo yum install wget -y
sudo wget -O /etc/yum.repos.d/rbu-dracut-crypt-ssh-epel-7.repo https://copr.fedorainfracloud.org/coprs/rbu/dracut-crypt-ssh/repo/epel-7/rbu-dracut-crypt-ssh-epel-7.repo
sudo yum install dracut-crypt-ssh -y

Type the following command below to install the nano editor to ease editing of files.

sudo yum install nano -y

You will need to edit the default grub file located in /etc/default/grub.

sudo nano /etc/default/grub

Insert rd.neednet=1 ip=dhcp between GRUB_CMDLINE_LINUX="crashkernel=auto and rd.luks.uuid=luks-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.

Save the file by entering the following keyboard combinations. Press the Ctrl + x keys, press the y key and press the Enter key.

Regenerate you GRUB configuration file by type the command below.

sudo grub2-mkconfig -o /etc/grub2.cfg 

Backup the original /etc/dracut.conf.d/crypt-ssh.conf by typing the following command below.

sudo mv /etc/dracut.conf.d/crypt-ssh.conf /etc/dracut.conf.d/crypt-ssh.conf.orig

Create a new /etc/dracut.conf.d/crypt-ssh.conf file by typing the following command below.

sudo nano /etc/dracut.conf.d/crypt-ssh.conf

Copy and paste the following text below into the nano editor.

dropbear_acl="/etc/dropbear/keys/authorized_keys"
dropbear_ecdsa_key="/etc/dropbear/keys/ssh_ecdsa_key"
dropbear_rsa_key="/etc/dropbear/keys/ssh_rsa_key"

Create the directory keys under /etc/dropbear/, with the necessary directory permissions, that will hold the authorized_keys, ssh_ecdsa_key and ssh_rsa_key files.

sudo mkdir /etc/dropbear/keys/; sudo chmod /etc/dropbear/keys/

Generate the ssh_ecdsa_key and ssh_rsa_key files with the ssh_keygen program by typing the following commands below. Press the Enter key twice, for each command, when prompted for passphrases.

sudo ssh-keygen -t ecdsa -f /etc/dropbear/keys/ssh_ecdsa_key
sudo ssh-keygen -t rsa -f /etc/dropbear/keys/ssh_rsa_key

Change the file permissions on ssh_ecdsa_key, ssh_ecdsa_key.pub, ssh_rsa_key and ssh_rsa_key.pub by typing the command below.

sudo chmod 400 /etc/dropbear/keys/*_key; sudo chmod 444 /etc/dropbear/keys/*.pub

Generate public keys using the How Do I Generate SSH Keys? tutorial, found at the beginning of the tutorial under Prerequisites, for your prospective client operating system.

Copy and paste all the text in the public key into the /etc/dropbear/keys/authorized_keys file using the nano program by typing the command below.

sudo nano /etc/dropbear/keys/authorized_keys

You must first build the initramfs and any subsequent update of the dracut-crypt-ssh configuration. Type the following command below for the initial build of the initramfs.

sudo dracut -f

Once that's complete, your CentOS 7 install is set up to listen for your SSH client to connect and allow you to unlock the LUKS partition using your passphrase. You may now reboot your CentOS 7 instance by typing the command below.

sudo reboot

På dine klientsystemer, se sektioner 3.3. Unlocking the volumes interactivelyog 3.4. Unlocking using thelås op commandpå Dracut-Crypt-SSH GitHub-siden for enten at tvinge en adgangssætningsprompt eller bruge unlockkommandoen til at åbne din LUKS-partition fra din SSH-klient.