Setting up a laptop: Difference between revisions
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== Full disk encryption with with cryptsetup-luks volumes == | == Full disk encryption with with cryptsetup-luks volumes == | ||
Revision as of 16:21, 13 March 2018
 Do not follow instructions here until this notice is removed. |
This guide is about a project to create a secured laptop. For this project we take in consideration ways to extend battery life. It covers tools and daemons that are must haves for a laptop setup.
Guide features
- Deniable full disk encryption
- Two factor authentication (physical (USB key), mind)
- Encrypted swap and hibernation
- Encrypted home on top of encrypted drive
- Memory sanitation
- Dynamic power modes
- Feature keys support
Rubberhose Attack
Just a reminder that all attacks are subjected to the Rubberhose Attack dilemma, you either give up your encryption keys or be tortured with a rubberhose with the possibly of death. See Wikipedia article. We try to present deniable encryption (Wikipedia) to avoid a rubberhose attack scenario. In this article we use the words plausible deniability interchangeably with deniable encryption. To achieve this we use a facade and require no metadata fingerprints to expose or hint of encrypted or hidden containers or hint as in detect of existence of an encrypted disk. The keys should be stored using steganography where we dilute the randomness into the facade. It also requires you not to brag about encryption or mention it because that is an invitation for the attacker to torture the victim. Deniable encryption requires you not put encrypted as an entry title to your bootloader. There shouldn't be an entry for your facade bootloader to the encrypted drive.
Why full disk?
The full disk encryption provides sort of some plausible deniability or a valid alibi that you didn't encrypt it. Is the drive just random noise, broken, or is it really encrypted? The other reason is that it implies that everything is protected.
But there could be problems if not done right. For example, cryptsetup does leave a plaintext marking or some hints by default that it has been encrypted when using luks/luks2 mode if a detached header with option --header <path> is not presented.[1][2] To gain credibility that we didn't really do the encryption, you have to wipe the +3 MiB region based on the number of key slots used; or store the headers on an external device.
If you did deniable encryption incorrectly, it is possible to erase and restore the header. This presents an opportunity to improve obfuscation. When you pull out the USB key, it should erase the header but store it on the USB key atomically as in completely. If you plug in the USB key, it will restore back the header. cryptsetup has luks actions luksHeaderBackup and luksHeaderRestore to do this.
Starting at the beginning
Grab a USB thumb drive with Alpine. Set it up as usual but don't let it touch your drive yet. Then, install all the tools into memory ramdisk but not in the hard drive yet. The hard drive will be obliterated.
You will then install Alpine using the steps:
First you need WiFi, to get it run do the command below but say no or skip the hard drive setup stuff:
setup-alpine
Then, you need to install some tools into RAM temporarly:
apk add e2fsprogs grub grub-bios grub-efi mkinitfs nano
Randomizing the drive with pseudorandom urandom entropy
The first part is to erase the drive with random noise but in practical time. There are many techniques to do this but should be done in one day or two minimum.
You can use shred or dd to accomplish this depending on your needs and the availability of entropy. Some techniques take longer. Cryptologist Bruce Schneier recommended 7 times with specified pattern. See Wikipedia Article. For practical purposes, we just do it random in one pass.
To list the drives on the system do fdisk -l.
IMPORTANT: make sure you wipe the right specific drive.
To wipe the disk with random entropy do:
dd if=/dev/urandom of=/dev/sda
Creating GPG keys
As of this time, Alpine's mkinitfs does only one factor authentication with passphrase. You need to manually edit the initramfs-init.in in mkinitfs to support two factor authentication using cryptsetup.
After you have scrambled the drive, you want to create your GPG keys. You will use these keys to set the password(s) for your cryptsetup-luks partitions. These keys should be stored on a USB thumb drive or other memory device but should not be on the USB boot thumb drive or on the encrypted drive. The key should be a random 128 bit key wrapped in GPG and protected with a password.
If you are using x, you need to do sudo apk add pinentry-gtk to display password prompt properly for the next step.
To install openssl and gpg do:
apk add openssl gnupg
Then, to generate a key:
openssl rand -base64 128 | gpg --symmetric --cipher-algo aes --armor > /mnt/usb/2a667ec72774b0d5
(Make sure your usb is mounted on /mnt/usb first.)
The long file name comes from openssl rand 8 -hex so that we enhance plausible deniability. The attacker cannot determine the purpose of the key. Is it used for GitHub? for Email?
The first part will produce 128 random bytes in wrap it in base64. The random data will be piped to gpg which will wrap it in AES as ciphertext which again gets wrapped in base64 ascii armor. For every partition including swap in some cases, you should create more gpg keys and store them in your USB thumb drives. After you have produced your gpg keys, you will then use them as a password for cryptsetup/luks.
You can replace aes above with the ones listed in gpg --version.
There should be a password generated for the swap. This is to resume for your hibernate. If you don't want to hibernate, then password is not required and all you need to do is to create/format the partition each time you boot without a password or with a one time random password.
Hiding the full disk encryption keys using steganography
WARNING: This section is considered experimental. It requires the tools to be placed on another USB separate from the key files, the bootloaders, and encrypted disks. The tool and dependencies need to be packaged together. We decentralize these components so that the attacker doesn't connect the dots easily or immediately jumps to the conclusion for the requirements to decrypt.
Fortunately, Alpine has a package for steganography called steghide. To install steghide do:
apk add steghide
You will place the keyfile in an image file. The facade image file should be large enough that there is no apparent discernible difference between the original and the modified. Do not use a small image with a small filesize.
There are two basic commands to use with steghide embed and extract,
To embed do:
steghide embed -ef key.gpg -cf image.jpg
To extract do
steghide extract -xf key.gpg -sf image.jpg
Full disk encryption with with cryptsetup-luks volumes
Partitioning scheme
This section presents a conceptual layout. It should not be a knee-jerk approval to automatically use the partition tool which would compromise your plausible deniability.
For the facade, we use an Ubuntu Live CD (or less skilled distro) to present the impression that we are not sophisticated or tech savvy enough to implement encryption. Windows is also acceptable even better. The immutable Live CD and immutable partition ensures that you are not compromised by a third party attacker that implants evidence.
There could be possibly two bootloaders, one for the facade and the other to the encrypted drive stored on a external device.
Luks
Plausible deniability only works if you can demonstrate no existence of partitions 2, 3, 4 and no fingerprints/plaintext introduced by cfdisk and cryptsetup-luks. Use something like TestDisk, fdisk -l, or gparted and a disk editor (hex editor for disks).
| # | Name | Mount point | Notes |
|---|---|---|---|
| 1 | facade | / | (optional) The facade partition contains a pristine normal operating system or Ubuntu Live CD image to lure the attacker in attempt to boost the confidence of the attacker convincing them that there is no encryption on the device. |
| 2 | swap | It should be the same size as your ram for x86_64. Rationale: it should contain the whole ram image. | |
| 3 | root | / | |
| 4 | rescue | / | This should contain the Alpine image. |
Plain dm-crypt
Plausible deniability only works if you are able to present #2 as being unused space or untampered. To check use something like TestDisk, gparted and a disk editor (hex editor for disks).
| # | Name | Mount point | Notes |
|---|---|---|---|
| 1 | facade | / | (optional) The facade partition contains a pristine normal operating system or Ubuntu Live CD image to lure the attacker in attempt to boost the confidence of the attacker convincing them that there is no encryption on the device. |
| 2 | vgroot | ||
| 2_1 | vgroot-root | / | |
| 2_2 | vgroot-swap | It should be the same size as your ram for x86_64. Rationale: it should contain the whole ram image. | |
| 2_3 | vgroot-rescue | / | This should contain the Alpine image. |
Installing cryptsetup
To install cryptsetup you need the package below
apk add cryptsetup
Choosing ciphers
When you create your luks drives, you need to decide on the type of ciphers and hashing techniques to use. The ciphers that you want to use are ones are up to you, but it should be one that is hasn't been cracked yet or has not suffered a lot of cryptanalysis attacks. The ones that you might want to use is AES which is hardware accelerated in some Intel CPUs that have the AES-NI cpuflag which you can check by cat /proc/cpuinfo. Also consider the ciphers that are SIMD optimized such as serpent and twofish that are available in the Linux kernel. Also consider ciphers that are unpopular but known to be secure such as Blowfish (which Wikipedia claims to be attacked and the author recommended Twofish).[3] If it is hardware accelerated, it will save battery life and minimize CPU usage.
For some ciphers weakness also see Cipher security summary (Wikipedia).
For some hash function weaknesses also see Hash function security summary (Wikipedia).
Generally speaking, the swap partition should use a fast cipher. You want to lower the latency or delay of the memory subsystem as a consequence of being encrypted.
IMPORTANT: Please read the Important notes section for details about the problems with AES encryption.
If you don't trust AES shills and endorsed by the NSA, you can try another different one. Another advantage of using a public vetted cipher is that it provides confidence that it works.
Something like KHAZAD wouldn't work on cryptsetup benchmark. KHAZAD itself is insecure. Wikipedia reported 5 out of 8 rounds been cracked.[4]
For AES-128 7 out of 10, AES-192 8 out of 12, AES-256-bit 9 out 14 rounds have been cracked according to Wikipedia.[5]
IMPORTANT: Do not use sha1 as the hashing algorithm. It already has already been compromised.
Getting the available ciphers
To check the availability of a cipher or hash function use:
find $(find /lib/modules -name "crypto" -type d) -type f -name "*.ko" | sort
To check if a cipher is loaded and passed its own tests use:
cat /proc/crypto
To test some popular ciphers and hashes do:
cryptsetup benchmark
The top set is associated with the hashing algorithms. The bottom set are the ciphers. Use the commands below but replace the cipher and/or hash algorithm with your preferences.
cryptsetup benchmark actually doesn't show all the ciphers like Anubis. The cipher should also have CBC and/or XTS block cipher mode of operation to encrypt larger block sizes. AES for example has a block size of 128.
To test if the unpopular but uncracked cipher works use sometime like:
cryptsetup benchmark --cipher anubis
General steps for cryptsetup
Original method with fdisk with no plausible deniability
In this method --type luks is implied which generates metadata.
If you want plausible deniability for luks, you need to pass --header <path> to all the luks commands, where <path> is a unix path like /mnt/usb/d6ae10eda66704c8. The random name comes from openssl rand -hex 8. The header is transferred to the external device (but no mention of the key slot area but ciphertext being transferred) in the man page. The information in that file should be obfuscated with encryption if there is plaintext or fingerprint in it just in case. Then, it should be decrypted when reused.
You need to install cfdisk if you prefer the interactive ncurses console method:
apk add cfdisk
| # | Step | Command |
|---|---|---|
| 1 | Use cfdisk to create partitions. Make two partitions--a system partition and a swap partition | cfdisk
|
| 2 | Create and format the luks device | cryptsetup --cipher aes-cbc-essiv:sha256 --key-size 256 luksFormat /dev/sda1 /mnt/usb/2a667ec72774b0d5
|
| 3 | Open the luks device | cryptsetup --key-file /mnt/usb/2a667ec72774b0d5 luksOpen /dev/sda1 root
|
| 4 | Format the decrypted drive with filesystem | mkfs.ext4 /dev/mapper/root
|
| 5 | Create the mount point | mkdir -p /mnt/root
|
| 6 | Mount the root partition | mount /dev/mapper/root /mnt/root
|
| 7 | Create swap | cryptsetup -c blowfish -h sha256 -d /dev/urandom --key-file /mnt/usb/59022506d9f4a714 create swap /dev/sda2 |
| 8 | Use swap | mkswap /dev/mapper/swap && swapon /dev/mapper/swap |
Improved method with plausible deniability
This method requires lvm2. To install:
apk add lvm2
| # | Step | Command |
|---|---|---|
| 1 | Open the plain dm-crypt device generating no metadata | cryptsetup open --type plain --cipher aes-cbc-essiv:sha256 --key-size 256 --key-file /mnt/usb/2a667ec72774b0d5 /dev/sda root
|
| 2 | Physical volume create with LVM | pvcreate /dev/mapper/pvroot
|
| 3 | Volume group create with LVM | vgcreate vgroot /dev/mapper/pvroot
|
| 4 | Logical volume create the swap volume with LVM | lvcreate -L 4G vgroot -n swap
|
| 5 | Logical volume create the root volume with LVM | lvcreate -L 2T vgroot -n root
|
| 6 | Logical volume create the rescue volume with LVM | lvcreate -L 110M vgroot -n rescue
|
| 7 | Format the root volume with filesystem | mkfs.ext4 /dev/mapper/vgroot-root
|
| 8 | Format the swap volume and activate it | mkswap /dev/mapper/vgroot-swap && swapon /dev/mapper/vgroot-swap
|
| 9 | Format the rescue volume with filesystem | mkfs.ext4 /dev/mapper/vgroot-rescue
|
| 10 | Create mount point for root volume | mkdir -p /mnt/root
|
| 11 | Mount the root volume | mount /dev/mapper/vgroot-root /mnt/root
|
Configuring OpenRC dmcrypt and setting up fstab
You need to tell OpenRC init scripts to decrypt the volumes. See /etc/conf.d/dmcrypt.
You need to add the service to boot well because it needs to decrypt the root volume before OpenRC starts running commands from it. So you need to do:
rc-update add dmcrypt boot
/etc/init.d/dmcrypt
The dmcrypt OpenRC service will attempt to decrypt the drive using information provided in /etc/conf.d/dmcrypt.
For luks:
Contents of /etc/conf.d/dmcrypt
For plain dm-crypt:
Contents of /etc/conf.d/dmcrypt
dm-crypt will just mount the encrypted plain dm-crypt drive or the luks partition. What you need to do next is set up fstab located at /etc/fstab. Examples are shown below.
/etc/fstab
To mount plain dm-crypt device with fstab:
Contents of /etc/fstab
To mount lvm volumes with fstab:
Contents of /etc/fstab
How to recover from a bad setup
Many times you will not get it right perfectly the first try. To recover from this situation, you need to reopen the plain dm-crypt drive or the luks drive and then remount everything back.
To recover from luks:
cryptsetup --key-file /mnt/usb/2a667ec72774b0d5 luksOpen /dev/sda1 root mkdir -p /mnt/root mount /dev/mapper/root /mnt/root
To recover from the plain dm-crypt:
cryptsetup open --type plain --cipher aes-cbc-essiv:sha256 --key-size 256 --key-file /mnt/usb/2a667ec72774b0d5 /dev/sda root vgchange -ay vgroot lvchange -ay vgroot/root mkdir -p /mnt/root mount /dev/mapper/vgroot-swap /mnt/root
Next step: Full blown Alpine installation
We will setup the /mnt/root encrypted partition:
apk add --root=/mnt/root --initdb $(cat /etc/apk/world)
Then, enable edge repositories in both files including community and testing:
nano /etc/apk/repositories /mnt/root/etc/apk/repositories
Then, copy the necessary files:
cp /etc/resolv.conf /mnt/root/etc
Then, install the basic utils:
apk add --root=/mnt/root dhcpcd chrony networkmanager wireless-tools wpa_supplicant apk add --root=/mnt/root grub mkinitfs e2fsprogs grub-bios grub-efi apk add --root=/mnt/root sudo nano apk add --root=/mnt/root linux-hardened
Then, you need to mount your usb on to /boot:
mount /dev/sdb /boot
Edit grub:
nano /boot/grub/grub.cfg
Then, install grub on the usb:
grub-install --force /dev/sdb
Then, prepare chroot:
mount --bind /dev /mnt/root/dev mount --bind /sys /mnt/root/sys cp /etc/reslov.conf /mnt/root/etc
Then, chroot:
chroot /mnt/root /bin/sh
Set the root administrator password:
passwd
The root password should be very difficult to deter you from using it and force you to use sudo
Edit sudo so that wheel group has administrative :
EDITOR=nano visudo
Set:
## Uncomment to allow members of group wheel to execute any command %wheel ALL=(ALL) ALL
Then, add wheel (administrator) user:
useradd -m myname usermod -a -G video,audio,wheel myname
log in that user:
su myname
Then, update and upgrade it
sudo apk update sudo apk upgrade
Then, setup xorg:
sudo setup-xorg-base sudo apk search xf86-video | sort # pick your video driver sudo apk add xf86-video-adi # pick your opengl driver sudo apk search mesa-dri* | sort sudo apk add mesa-dri-ati
Then, keep piling on:
sudo apk add firefox dwm xfce4-terminal alsa-utils keepassx xfce4 xchat sudo apk add font-noto-emoji terminus-font leafpad xsetroot # See Emojis to complete installation sudo apk add xf86-input-mouse xf86-input-keyboard
Then, set the desktop:
nano .xinitrc
Put both but comment with a # one of them if you don't want it,
#while true; do xsetroot -name "$( date +"%a %b %d %I:%M:%S %Y" )" ; sleep 1; done & #exec dwm exec xfce4-session
For the above xsetroot statement used to provide information in the statusbar for dwm, consider adding information about the battery level. This information can be found in sysfs at /sys/class/power_supply/BAT0/.
sync sudo reboot
Hacking mkinitfs to support cryptsetup with GPG keys
You may want to hack the mkinitfs init script and rebuild the package depending on what methods you use. You could possibly have a complex way to hide your GPG keys (again enhancing plausible deniability) with steganography or extend it with three-factor authentication which adds biometrics along side with mind and physical.
See https://github.com/alpinelinux/mkinitfs/tree/master, in particular mkinitfs.in and nlplug-findfs.c.
You will modify /usr/share/mkinitfs/initramfs-init to add cryptsetup-gpg support. Then, you reinstall your kernel and it should automatically place the init script to your boot device. Also save a backup of this script in case a new version destroys it. It is recommended that your boot scripts do not directly refer to the key to preserve plausible deniability which can be achieved by additional prompts and regular expression and possibly store the key on another USB thumb drive or alternative device separate from the bootloader to have true two factor authentication. You don't want to give hint that this random data which some might jump to conclusion to as being key is associated with the boot process just because many people have duplicated the instructions in adding full disk encryption. You will manually call the cryptsetup command possibly or the renamed version of it. Once you present a password prompt immediately at the boot process, it invites the rubberhoser.
The encrypted bootloader or init scripts could possibly be designed to immediately boot to the facade partition but then special secret unique boot selection keypresses to present the special menu go redirect towards the encrypted partition but not explicitly saying that it is encrypted.
Also, you may want to rename dm-crypt, cryptroot, cryptdm to alias to an identifier facade and possibly rename the modules and folders and cryptsetup (which may require a recompile). Again, we do not want to present hints to motivate the attacker of the possibility that such an encrypted device exists to avoid the rubberhose attack.
If your device uses plain dm-crypt, it needs the initscript modified near the nlplug-findfs commands. The line could be found in initramfs-init.in at line 392 (on GitHub), or call it manually.
Encrypted hibernate also needs GPG key support. Maybe change initramfs-init.in at line 403 (on GitHub), or call it manually.
Install the bootloader in the USB thumb drive
To install grub, you need to install grub on the ramdisk first on the host.
apk add grub
To get a list of partitions
fdisk -l
Mount the boot partition in /boot
mount /dev/sdb /boot
Make changes to grub's configuration
nano /boot/grub/grub.cfg
You need to customize the initramfs in order to use GPG keys since there is no support from it. The steps here below assumes that these custom initramfs features have been implemented.
The following are just examples to just get it working but should be modified so that it doesn't hint to the rubberhoser of a hidden partition or encrypted partitions.
The entry should look like:
For 'luks'
Contents of /boot/grub/grub.cfg
For 'plain dm-crypt':
The stock mkinitfs may not support plain dm-crypt. It looks like it only supports luks. Customization of the initramfs is required.
Contents of /boot/grub/grub.cfg
The source code of grub could possibly be modified and recompiled to use other non-standard keys. See [6]. Ideally, it should be not so obvious or accessible for the attacker.
The above grub.cfg is applied to the USB bootloader. For the facade bootloader, you just want the Windows 10 or Ubuntu entry, nothing more.
For the modules parameter, you need to add your crypto modules.
Use find /lib/modules/ -name "*aes*" where aes is the basename for your cipher or hash algorithm
Use blkid to obtain the UUID of your device
Install it to your USB thumb drive
grub-install /dev/sdb
Home mounting with eCryptfs
We use eCryptfs to encrypt home. The rationale for having another encrypted file system is that if you leave your laptop unattended on break or accidentally leave your USB key in, your data will not be accessible. The other rationale is that if another person wants to use your computer, you can just log off and the data will be kept hidden and encrypted. When you log off due to inactivity, your home directory will be unmounted and encrypted. eCryptfs will encrypt/decrypt the filename and the contents and will sit on top of ext4 which sits on top of luks.
To install ecryptfs-utils:
sudo apk add ecryptfs-utils
This does one factor authentication mostly with just the password, but it should be modified to use the USB key too. You need to reconfigure pam with the pam_usb.so which is not in Alpine aports.
You need to use the pam_ecryptfs PAM module.
Locking it down
Many times you will leave your laptop behind with people you trust. The following tools will help lock down the system.
physlock
This will auto lock the tty and when you return will prompt for password.
To install physlock:
sudo apk add physlock
It is currently bugged. See [7]. physlock likely doesn't do two-factor authentication but it should.
You need to create custom script that will monitor idle time in TTY then call physlock. You load this script when you log on.
xscreensaver
This will lock you out of xserver
To install xscreensaver:
sudo apk add xscreensaver
USB key udev rule
You need to add a new udev rule that will suspend-to-ram or hibernate and log off once you pull the USB key. When you come back on, you should do 2 factor authentication to restore back everything. Hibernation and suspend-to-ram might mitigate cold-boot attack (but unlikely see notes at the bottom of the page) to extract plaintext private data and encryption keys in memory.
To find out the details of your USB do:
udevadm monitor --udev -p
The output should look like:
UDEV [181762.722853] add /devices/pci0000:00/0000:00:13.2/usb2/2-5/2-5:1.0/host6/target6:0:0/6:0:0:0/block/sdc (block) ACTION=add DEVLINKS=/dev/disk/by-id/usb-Kingston_MSFT_NORB_MSFTLAKDA300EB3021790009-0:0 /dev/disk/by-path/pci-0000:00:13.2-usb-0:5:1.0-scsi-0:0:0:0 /dev/disk/by-uuid/5A96-03E4 DEVNAME=/dev/sdc DEVPATH=/devices/pci0000:00/0000:00:13.2/usb2/2-5/2-5:1.0/host6/target6:0:0/6:0:0:0/block/sdc DEVTYPE=disk ID_BUS=usb ID_FS_TYPE=vfat ID_FS_USAGE=filesystem ID_FS_UUID=5A96-03E4 ID_FS_UUID_ENC=5A96-03E4 ID_FS_VERSION=FAT32 ID_INSTANCE=0:0 ID_MODEL=MSFT_NORB ID_MODEL_ENC=MSFT\x20NORB\x20\x20\x20\x20\x20\x20\x20 ID_MODEL_ID=1645 ID_PATH=pci-0000:00:13.2-usb-0:5:1.0-scsi-0:0:0:0 ID_PATH_TAG=pci-0000_00_13_2-usb-0_5_1_0-scsi-0_0_0_0 ID_REVISION=PMAP ID_SERIAL=Kingston_MSFT_NORB_MSFTLAKDA300EB3021790009-0:0 ID_SERIAL_SHORT=MSFTLAKDA300EB3021790009 ID_TYPE=disk ID_USB_DRIVER=usb-storage ID_USB_INTERFACES=:080650: ID_USB_INTERFACE_NUM=00 ID_VENDOR=Kingston ID_VENDOR_ENC=Kingston ID_VENDOR_ID=0951 MAJOR=8 MINOR=32 SEQNUM=2027 SUBSYSTEM=block USEC_INITIALIZED=1762722168
You want to extract the ID_SERIAL_SHORT=MSFTLAKDA300EB3021790009 or whatever is associated with your USB thumb drive.
You need pm-utils for ps-suspend. So to install it do:
sudo apk add pm-utils
You will create a udev rules so that when you pull out the USB, it will suspend-to-ram or you can use your own script. To do that create a file with the following contents:
Contents of /etc/udev/rules.d/50-usb-thumb-drive.rules
Extending battery life
ACPI
ACPI is a good daemon to use to execute certain scripts when laptop events are triggered.
To install ACPI do:
apk add acpi
The events to pay attention to are:
| Event | ACPI Event | What your script should do |
|---|---|---|
| lid close | log off ttys and suspend-to-ram. ALSA should either set the volume to 0 for the sound card or the sound driver be unloaded. It might be a good idea to kill or mute any music or movie players if the sound loops loudly after lid open. | |
| lid open | lock all ttys and all xservers should be locked, possibly reinitialize ALSA and the sound system. | |
| tapped power button | lock all ttys and suspend-to-ram | |
| held power button | hibernate | |
| unplugged power | should switch to 'conservative' cpufreq governor at above 25% power ; 'powersave' governor at 25%. set hdparam spindown rate lower. | |
| plugged power | should switch to 'performance' governor. disable hdparam spindown. |
The purpose of the power governor is to regulate the running frequency (GHz) of the processor.
Certain event handlers are are managed through laptop-mode-tools. If you don't want the dependency, then you could write ACPI handler scripts.
acpi_listen can be used to retrieve the event name.
TODO: put scripts below
Adjusting the backlight dynamically
The backlight may be controlled using sysfs. The setting is a descendant of /sys/class/backlight/. The feature may allow you to echo a value to it. Use trial and error to discover the values.
The adjustment of the backlight should be function of battery life. So if it is like 33% battery life, you want to run it near lowest settings but readable. For 50 percent battery energy maybe 40% light. For 90% battery maybe 75% light.
hdparm
To install hdparam do:
sudo apk add hdparm
The settings that laptop-mode-tools messes with is the -S or the spindown timeout. It was also hinted that acoustic setting -M is associated with the speed meaning that louder is faster and quieter is slower which could contribute to the amount of energy used or reduced.
Again you want something like laptop-mode-tools or ACPI to dynamically adjust the settings based on ACPI events.
laptop-mode-tools
This is currently not in aports but worthy mentioning. It should really be packaged. This is a set of scripts to define a power policies. You can manage all the settings in one place here like the hard drive idle spindown time, CPU governor control, dynamic LCD backlight behavior based on running on battery or AC power supply.
cpufreqd
This is a useful daemon for regulating power.
To install cpufreqd do:
sudo apk add cpufreqd
Make sure you add the service:
sudo rc-update add cpufreqd
LCD screen refresh rate
The refresh rate sets the maximum framerate. The more frames pushed the more energy consumed on the battery. You want this adjusted dynamically per certain events. For gaming, you want it to be the highest as possible for the laptop and vsync off. For battery use and traveling, you want it capped at 60 FPS/60 Hz or lower but dynamically adjust when you plug in the AC power supply. You can adjust the framerate with xrandr. For movies and YouTube, you want 60FPS and vsync on.
Hacking the kernel
You should refer to the Custom Kernel page for details.
Hibernation
See Hibernation to prevent data loss.
WiFi management
Since you are using WiFi, you need a better WiFi management to quickly find open access WiFi access points. We don't have all day to debug complexities of WiFi settings while away from home.
To install NetworkManager do:
sudo apk add networkmanager
To find WiFi access points use the nmtui ncurses interface.
You also need other programs so install them as well:
apk add wpa-supplicant dhcpcd chrony macchanger wireless-tools iputils
What these programs do:
- wpa-supplicant -- for WPA encryption
- dhcpcd -- for getting a dynamic IP address
- chrony -- for fixing the time with the atomic clock
- wireless-tools -- for additional information
- macchanger -- for protecting against WiFi access discrimination or increased anonymity. (optional)
- iputils -- for the ping command (optional)
You also need to add those services:
rc-update add chrony rc-update add wpa-supplicant rc-update add dhcpcd rc-update add networkmanager
To start the services manually (or just reboot):
/etc/init.d/chrony start /etc/init.d/wpa-supplicant start /etc/init.d/dhcpcd start /etc/init.d networkmanager start
Additional tools
actkbd
To control the sound with fn function keys, you need this daemon. It is currently not in aports. You could override the design and meaning of those keys with your own scripts and utilities. This daemon gives you that freedom.
If your laptop contains a brightness key, you want to set that up with this program. See also Adjusting the backlight dynamically.
secure-delete
Want to prevent cold-boot attack or decrypted keys in memory falling in the wrong hands? This maybe could work who knows?
To install secure-delete do:
sudo apk add secure-delete
smem only works for unused ram.[8] If you use the vanilla kernel, this may work. If you use grsecurity, it will automatically sanitize memory [unconfirmed if enabled] when the memory page is freed.[9]
Close all important programs then call smem.
You call smem in your shutdown script or auto-logoff script.
You can call create a OpenRC shutdown script to run smem when most programs and services are closed. This will erase all your sensitive plaintext private data just in case.
You may want to create a wrapper script to call smem after your program closes.
You need to write a custom script that does the following:
* kill all running processes associated with your user account * auto logoff terminals * for the last terminal closed including all idle xservers, unmount your user home * (optional) use smem to wipe all your plaintext private data in memory after all closed programs in case of cold boot attack
Sharing presentations over HDMI
If you want to use your laptop to share presentation over HDMI connection, you need libxinerama and xrandr.
To install libxinerama and xrandr do:
sudo apk add libxinerama xrandr
Important notes
If you lose or break your USB key, that is it and you cannot decrypt your drive. It would be wise to make a backup of it.
I don't know if suspend-to-ram or hibernate sufficiently clear the AES encryption keys off ram in those phases which would invite a cold boot attack. This has been covered by the TRESOR kernel patch.[10][11] This patch hasn't been updated since the 4.x kernel series.[12]. This patch currently only works on 32-bit x86 Linux with SSE and MMX, and on processors with the AES-NI instruction set for x86_64 Linux. TRESOR doesn't work with DMA attack. The 32-bit version of TRESOR has only a key size of 128. The AES-NI version of TRESOR has a largest key size of 256 bit. See Choosing ciphers for the number of rounds cracked.
Loop-Amnesia works with LoopAES and is only for 64 bit Linux and only supports 128 bit keys but can result in data loss if their recommendations are not followed. [13]
Please read the Wikipedia article on Cold Boot Attack especially the mitigation section.[14] Full disk encryption will not protect your data especially for older hardware if you do not have the proper mitigation (implying not full proof) prerequisites such as a patched kernel, memory scrambling, permanent memory module mounting for example.