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While playing around with this be aware that this it render your system unbootable. You should have the skills to use a GNU/Linux recovery CD to undo the changes you have made before you proceed! | While playing around with this, be aware that it might render your system unbootable. You should have the skills to use a GNU/Linux recovery media to undo the changes you have make before proceeding! |
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$ echo -n "uptime" | md5sum | dd of=keyfile_md1 bs=1 count=32 | $ echo -n "uptime" | md5sum | dd of=/root/install/luks/keyfile_md1 bs=1 count=32 |
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# cryptsetup luksAddKey /dev/md1 keyfile_md1 | # cryptsetup luksAddKey /dev/md1 /root/install/luks/keyfile_md1 |
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Reboot and test. | Congratulations, you have now hosed you security! Reboot and test. |
KVM Host Booting from Luks Encryption
While encrypting your disks is a good idea, it also presents you with the problem that you have to enter the passphrase when booting the system. Running the KVM Host as a headless system with no keyboard attached really introduces a problem. Entering the passphrase is what the security is about, so circumventing this is really hosing you security.
While playing around with this, be aware that it might render your system unbootable. You should have the skills to use a GNU/Linux recovery media to undo the changes you have make before proceeding!
Add a New Luks Key
Find yourself a good passphrase.
$ echo -n "uptime" | md5sum | dd of=/root/install/luks/keyfile_md1 bs=1 count=32
Add the New Key.
# cryptsetup luksAddKey /dev/md1 /root/install/luks/keyfile_md1 Enter any existing passphrase:
Put the Key on an USB Storage Device
Insert your USB storage device, Has to hold 32 bytes, hard to find a device that small. I use a 4GB USB storage device myself. Make the USB storage device look like its just garbage data.
# dd if=/dev/urandom of=/dev/sde
Put the key on it.
# dd if=keyfile_md1 of=/dev/sde
Using the Key
Next we need the initrd image to be able to use that information. Create the following script and make it executeable. This script is not optimized in any way, but it checks all partitions in /proc/partitions until it finds a valid key. Make sure you set SOURCE and TARGET to fit your system.
/root/install/luks/keyscript.sh
1 #!/bin/sh
2
3 SOURCE="/dev/md1"
4 TARGET="md1_crypt"
5
6 while [ ! -e /dev/mapper/${TARGET} ]
7 do
8 while read a b c DEVICE
9 do
10 if [ ! -e /dev/mapper/${TARGET} ]
11 then
12 if [ -e /dev/${DEVICE} ]
13 then
14 #echo -n "$DEVICE "
15 dd if=/dev/${DEVICE} of=proposedkey bs=1 count=32 > /dev/null 2>&1
16 cryptsetup luksOpen ${SOURCE} ${TARGET} --key-file proposedkey > /dev/null 2>&1
17 fi
18 fi
19 done</proc/partitions
20 done
21 cryptsetup luksClose /dev/mapper/${TARGET}
22 cat proposedkey
Add the use of the script to /etc/crypttab.
md1_crypt UUID=72deeb7f-2289-40c5-99c1-52238afb78ef none luks
Becomes
md1_crypt UUID=72deeb7f-2289-40c5-99c1-52238afb78ef none luks,keyscript=/root/install/luks/keyscript.sh
Update initrd image and Grub
# update-initramfs -u # update-grub
Congratulations, you have now hosed you security! Reboot and test.