Archive for the ‘Laptop’ Category

Ubuntu 18.04 and TPM2 encrypted system disk

Monday, May 27th, 2019

*** EDIT *** : An updated version of this post can be found here: https://run.tournament.org.il/ubuntu-20-04-and-tpm2-encrypted-system-disk/

When you encrypt your entire disk, you are required to enter your passphrase every time you boot your computer. The TPM device has a purpose – keeping your secrets secure (available only to your running system), and combined with SecureBoot, which prevents any unknown kernel/disk from booting, and with BIOS password – you should be fully protected against data theft, even when an attacker has a physical access to your computer in the comfort of her home.

It is easier said than done. For the passphrase to work, you need to make sure your initramfs (the initial RAM disk) has the means to extract the passphrase from the TPM, and give it to the encryptFS LUKS mechanism.

I am assuming you are installing an Ubuntu 18 (tested on 18.04) from scratch, you have TPM2 device (Dell Latitude 7490, in my case), and you know your way a bit around Linux. I will not delay on explaining how to edit a file in a restricted location and so on. Also – these steps do not include the hardening of your BIOS settings – passwords and the likes.

Install an Ubuntu 18.04 System

Install an Ubuntu system, and make sure to select ‘encrypt disk’. We aim at full disk encryption. The installer might ask if it should enable SecureBoot – it should, so let it do so. Make sure you remember the passphrases you’ve used in the disk encryption process. We will generate a more complex one later on, but this should do for now. Reboot the system, enter the passphrase, and let’s get to work

Make sure TPM2 works

TPM2 device is /dev/tpm0, in most cases. I did not go into TPM Resource Manager, because it felt overkill for this task. However, you will need to install (using ‘apt’) the package tpm2_tools. Use this opportunity to install ‘perl’.

You can, following that, check that your TPM is working by running the command:

sudo tpm2_nvdefine -x 0x1500016 -a 0x40000001 -s 64 -t 0x2000A -T device

This command will define a 64 byte space at the address 0x1500016, and will not go through the resource manager, but directly to the device.

Generate secret passphrase

To generate your 64bit secret passphrase, you can use the following command (taken from here):

cat /dev/urandom | tr -dc ‘a-zA-Z0-9’ | fold -w 64 | head -n 1 > root.key

Add this key to the LUKS disk

To add this passphrase, you will need to identify the device. Take a look at /etc/crypttab (we will edit it later) and identify the 1nd field – the label, which will relate to the device. Since you have to be in EFI mode, it is most likely /dev/sda3. Note that you will be required to enter the current (and known) passphrase. You can later (when everything’s working fine) remove this passphrase

sudo cryptsetup luksAddKey /dev/sda3 root.key

Save the key inside your TPM slot

Now, we have an additional passphrase, which we will save with the TPM device. Run the following command:

sudo tpm2_nvwrite -x 0x1500016 -a 0x40000001 -f root.key -T device

This will save the key to the slot we have defined earlier. If the command succeeded, remove the root.key file from your system, to prevent easy access to the decryption key.

Create a key recovery script

To read the key from the TPM device, we will need to run a script. The following script would do the trick. Save it to /usr/local/sbin/key and give it execution permissions by root (I used 750, which was excellent, and did not invoke errors later on)

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#!/bin/sh
PREREQ=""
prereqs()
 {
     echo "$PREREQ"
 }
case $1 in
 prereqs)
     prereqs
     exit 0
     ;;
esac
. /usr/share/initramfs-tools/hook-functions
copy_exec /usr/sbin/tpm2_nvread
copy_exec /usr/bin/perl
exit 0

Run the script, and you should get your key printed back, directly from the TPM device.

Adding required commands to initramfs

For the system to be capable of running the script, it needs several commands, and their required libraries and so on. For that, we will use a hook file called /etc/initramfs-tools/hooks/decryptkey

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#!/bin/sh
PREREQ=""
prereqs()
 {
     echo "$PREREQ"
 }
case $1 in
 prereqs)
     prereqs
     exit 0
     ;;
esac
. /usr/share/initramfs-tools/hook-functions
copy_exec /usr/sbin/tpm2_nvread
copy_exec /usr/bin/perl
exit 0

The file has 755 permissions, and is owned by root:root

Crypttab

To combine all of this together, we will need to edit /etc/crypttab and modify the argument (for our relevant LUKS) by appending the directive ‘keyscript=/usr/local/sbin/key’

My file looks like this:

sda3_crypt UUID=d4a5a9a4-a2da-4c2e-a24c-1c1f764a66d2 none luks,discard,keyscript=/usr/local/sbin/key

Of course – make sure to save a copy of this file before changing it.

Combining everything together

We should create a new initramfs file, however, we should make sure we keep the existing one for fault handing, if required to. I suggest you run the following command before anything else, so keep the original initramfs file:

sudo cp /boot/initrd.img-`uname -r` /boot/initrd.img-`uname -r`.orig

If we are required to use the regular mechanism, we should edit our GRUB entry and change the initrd entry, and append ‘.orig’ to its name.

Now comes the time when we create the new initramfs, and make ourselves ready for the big change. Do not do it if the TPM read script failed! If it failed, your system will not boot using this initramfs, and you will have to use the alternate (.orig) one. You should continue only if your whole work so far has been error-free. Be warned!

sudo mkinitramfs -o /boot/initrd.img-`uname -r` `uname -r`

You are now ready to reboot and to test your new automated key pull.

Troubleshooting

Things might not work well. There are a few methods to debug.

Boot the system with the original initramfs

If you discover your system cannot boot, and you want to boot your system as-it-were, use your original initramfs file, by changing GRUB during the initial menu (you might need to press on ‘Esc’ key at a critical point) . Change the initrd.img-<your kernel here> to initrd.img-<your kernel here>.orig and boot the system. It should prompt for the passphrase, where you can enter the passphrase used during installation.

Debug the boot process

By editing your GRUB menu and appending the word ‘debug=vc’ (without the quotes) to the kernel line, as well as removing the ‘quiet’, ‘splash’ and ‘$vt_hansoff’ directives, you will be able to view the boot process on-screen. It could help a lot.

Stop the boot process at a certain stage

The initramfs goes through a series of “steps”, and you can stop it wherever you want. The reasonable “step” would be right before ‘premount’ stage, which should be just right for you. Add to the kernel line in GRUB menu the directive ‘break’ without the quotes, and remove the excessive directives as mentioned above. This flag can work with ‘debug’ mentioned above, and might give you a lot of insight into your problems. You can read more here about initramfs and how to debug it.

Conclusion

These directives should work well for you. TPM2 enabled, SecureBoot enabled, fresh Ubuntu installation – you should be just fine. Please let me know how it works for you, and hope it helps!

i810 dual-pipe issues with power management

Friday, May 9th, 2008

I have had a problem with my IBM X41 – ever since I have started using Ubuntu 7.10 (after a nice upgrade from 7.04), whenever the lid was closed, and reopened – the display would have flickered for a short while (while the lid is up) and then blank completely.

My (ugly) workaround was to force the computer to sleep whenever it happened. It seemed to be a workaround good enough for most cases. On some cases, the laptop would do just the same as it was placed in its docking station.

I have found an Ubuntu bug here, which seems to expose this problem too. It exposed few additional problems as well. The error message I got (through SSH, of course) when viewing the logs it said that the video card detected pipe A to be the active pipe, that it stopped using pipe B (which appeared to be the internal one) and that it decided to disable clone mode. Wow. I just lost my internal LCD. Connecting an external display, I get the whole picture working just fine, however, I cannot use the laptop like that.

After a major struggle with various i810 options, I have looked and found an option to disable Power Management. I have done so, according to the note here, and it solved all my problems in this area – for now.

Dial-up in Israel through Orange 3G

Saturday, May 3rd, 2008

I have set up a small script to allow me to dial-up using my cell to the internet. The speed of the 3G connection is quite amazing, and this information would assist, I’m sure, others as well. I am using Bluetooth to communicate between my cell and my portable computer.

Steps:

1. Create an /etc/wvdial.conf with the following contents:

[Dialer Defaults]
Phone = *99***1#
Username = orange
Password = mobile54
New PPPD = yes
Modem = /dev/rfcomm1
Baud = 460800
Init2 = atz
ISDN = off
Modem Type = Analog Modem
Dial Attempts = 1
Abort on No Dialtone = off
Stupid Mode = on

2. Pair your mobile and your laptop (check it on the net). Get the hardware ID

3. Get the channel for DUN (or Dial-Up Networking)

4. Add this script in /usr/local/sbin/ (I called it “gprs”). Replace the zeros with your own hardware ID, and the number 4 (Nokia N95) with the channel you use:

#!/bin/bash
rfcomm connect 1 00:00:00:00:00:00 4 &
PID_BT=$!
echo $PID_BT
sleep 5
wvdial &
PID_WV=$!
echo $PID_WV
sleep 7
ifconfig
echo “Press on Ctrl+C to disconnect”

trap “{ kill $PID_WV; sleep 1; kill $PID_BT; exit; }” SIGINT

while true; do sleep 10; done

5. You need to run the script under “sudo”. Ctrl+C will exit and disconnect.

Good luck.

Orinoco_pci finally working correctly!

Thursday, March 9th, 2006

After upgrading my laptop to 2.6.15.1 kernel, hibernation worked flawlessly. Running my previous version of kernel – 2.6.14.2, I have had some hibernation instabilities. I’ve had some memory corruptions here and there, which would have required I reboot the machine. So far, and it’s been a while, I’m glad to say I had no reason to "reboot" my laptop, but only to hibernate and awake it. Works like a charm.

In my post here, I have complained of performance issues with Orinoco_pci module. Although I’ve had somewhat below the average speed in my LAN (I’ve got about 800KB/s, give or take, on my 802.11b network), using this line to reach an external server / address or even a web site was disastrous. Degraded performance, up to no connection at all. Ping was correct at all times, just as a simple wget to a rather close server (on my ISP’s server room) got timed-out, and drained to less than 2KB/s… Terrible.

In this kernel version, as I’m happy to say, I have tested the built-in orinoco, and finally it’s working just as it should. I get to use my full internet bandwidth, and I’m happy with it. Normal response times, and all. Now all I’ve got left is to make sure the internal LEDs work. On another day 🙂

Kernel update – 2.6.15.1

Friday, March 3rd, 2006

Alongside a newer kernel, I’m enjoying a newer Software Suspend2 package. I am not crazy about betas, or RCs, so now I’m on the 2.2 stable. I have hibernated only once since I’ve upgraded kernel, but it went just fine on the first try, so I’m rather ok with it without setting a set of cover-it-all tests.

Here’s my kernel config, if anyone’s interested – config-2.6.15.1.txt

Also, you can get the latest swsusp2 and fbsplash from the right places, as described in my post here. It’s good I use this blog – it keeps my memories for me.