Terminal

Wireguard VPN networking

Mon, 09 Nov 2026 00:00:00 +0000

Background

As easier or ad-hoc VPN solution to openvpn, wireguard provides user space tools for point-to-point networking with roaming clients.

One static public host is needed.

Network topology

Server

Any publicly reachable host with optional DNS name.

It also has private address 172.16.0.1 for WG interface.

Roaming peer 1

Using any network anywhere. WG address is 172.16.0.2

Package setup for all hosts

sudo apt install wireguard-tools

Key generation

Server

wg genkey >/root/wg/srv.key
wg pubkey </root/wg/srv.key >/root/wg/srv.pub

Peer 1

wg genkey >/root/wg/stinky.key
wg pubkey </root/wg/stinky.key >/root/wg/stinky.pub

Server setup

Allow traffic at udp/12345

ufw allow udp/12345 comment 'wireguard'

Public server config

The peer key below is stinky.pub contents

Dump your own L3 CDM

Thu, 22 Oct 2026 00:00:00 +0000

Sometimes you need widevine keys/device for whatever reason, like dumping content from your streaming service.

Install android studio by whatever means necessary

Prepare a virtual device

create new device in device manager
choose Pixel 4 XL
install API 34 and select Google APIs Intel x86_64 Atom System Image

Prepare host and host software

mkdir keydive && cd keydive
python3 -m venv .venv keydive && .venv/bin/activate
pip install frida frida-tools keydive

Download or build frida server apk

git checkout https://github.com/frida/frida.git
wget https://github.com/frida/frida/releases/download/17.24.3/frida-server-17.24.3-android-x86_64.xz

Launch the android virtual device from studio

Check that emulator is visible to adb

adb devices

Run frida-server on virtual device

adb root
adb push frida-server-17.24.3-android-x86_64 /data/local/tmp/
adb shell
cd /data/local/tmp/
chmod 750 frida*
./frida-server-17.24.3-android-x86_64

Run keydumper in python venv (keydive)

keydive -kw -a player

Proper startup looks like this:

What, why?

Mon, 12 Oct 2026 00:00:00 +0000

Can’t remember shit and I’m tired of (re)learning same same but same all the time.

So there.

NVRAM/efivarfs is full

Mon, 03 Aug 2026 00:00:00 +0000

Efivars are stored in motherboard NVRAM and sometimes there can be too many entries making firmware updates impossible.

Efivarfs is the linux sysfs interface for this data.

Check out current NVRAM entries

sudo efibootmgr

If you want to remove some useless entry (for example USB CD)

sudo efibootmgr -b 1c -B

Clean up duplicate boot order entries

sudo efibootmgr -D

Hopefully this will free up enough space for updates

Writing bootable ISO images to USB media

Mon, 26 Jan 2026 00:00:00 +0000

Iinterweb instructions are often overly complex, using all kinds of “image burning” applications.

You need nothing special.

If the image is bootable, it will show as such:

$ file image.iso
image.iso: ISO 9660 CD-ROM filesystem data (DOS/MBR boot sector) 'FOOBAR_1.0' (bootable)

Writing image to USB media

Always check and confirm your target device with lsblk.

Umount old fs before doing anything.

Option 1: cat

Writes directly to block device

cat image.iso >/dev/sdb

Option 2: dd

Possibility to specify more efficient block size and get some progress info

Convert android screenshots to AVIF

Fri, 05 Dec 2025 00:00:00 +0000

Jpeg or png based phone screenshots are huge, we dont want that. AVIF is excellent free and open image format for many purposes. AVIF image is basically a singular AV1 video frame in a HEIF container.

Install tools

Imagemagick is bad with multithreading so we use GNU parallel to utilize all CPU cores. Otherwise excellent graphicsmagick doesn’t know how to write avif at the time of writing, so we are stuck with IM.

Profiling android battery usage

Sun, 20 Jul 2025 00:00:00 +0000

ADB shell access is needed so enable developer mode and allow ADB in developer settings. ADB over tcp can be useful, but USB3 is much faster.

Initiate logging

Lets start measuring and logging, preferably with almost empty battery.

Connect phone to computer with USB and reset battery stats.

adb shell dumpsys batterystats --reset

Charge the phone to 100%. Then use the phone normally until something interesting happens, like severe battery drain.

Test ethernet cables with two local interfaces

Thu, 29 May 2025 00:00:00 +0000

Connect (usb) ethernet adapters and some cable between them
Disable both interfaces from network settings / network manager

Check interface visibility

# ip a | grep enx
enx7cc2c6448e83: <BROADCAST,MULTICAST,UP,LOWER_UP>
enx60a4b7ddea36: <BROADCAST,MULTICAST,UP,LOWER_UP>

Setup first interface

# add IP address to 1st interface
ip a add 10.10.10.10/24 dev enx7cc2c6448e83

Setup new network namespace and second interface

# create new network namespace
ip netns add lan2

# move 2nd interface to new namespace
ip link set enx60a4b7ddea36 netns lan2

# bring up 2nd interface
ip netns exec lan2 ip link set dev enx60a4b7ddea36 up

# add IP address to 2nd interface
ip netns exec lan2 ip a add 10.10.10.11/24 dev enx60a4b7ddea36

Test connection between interfaces

# ping 10.10.10.11

PING 10.10.10.11 (10.10.10.11) 56(84) bytes of data.
64 bytes from 10.10.10.11: icmp_seq=1 ttl=64 time=0.755 ms
64 bytes from 10.10.10.11: icmp_seq=2 ttl=64 time=0.743 ms
64 bytes from 10.10.10.11: icmp_seq=3 ttl=64 time=1.03 ms

3 packets transmitted, 3 received, 0% packet loss, time 2087ms

Android <-> PC notepad style file editor/sync

Wed, 30 Apr 2025 00:00:00 +0000

General info

Mobile and PC can be in any different networks, ssh is used for comms. OpenVPN is used for handy and secure access bridging any networks.

Android setup

install “Simple SSHD” from play market, it is dropbear sshd daemon
- inject your public key into phone sshd
- configure port etc
- create sshd shortcut on home screen
install fossify notepad from play market
- configure new txt file with export to sd option
- make the file /sdcard/000notepad.txt

Linux setup

working ssh client and some network required
openvpn client is required

Place editor script into PC ~/bin/memo

#!/bin/bash
MNT=$(mktemp -d); sshfs phone:/sdcard/ $MNT && vi $MNT/000notepad.txt && umount $MNT && rmdir $MNT

SSH client config setup with LAN/VPN aliasing

# phone in VPN network
Match originalhost op10 localnetwork 172.16.10.0/24
Hostname 172.16.10.2

# phone in home LAN
Host op10
HostName 192.168.1.44
Port 2222

Usage

Run memo command in any network while phone sshd is running and you can view/edit the file from anywhere

OpenVPN networking

Thu, 03 Apr 2025 00:00:00 +0000

Package setup for building files at any host computer

sudo apt install easy-rsa openssl openvpn

Package setup for OpenVPN server

sudo apt install openvpn

Create directory for building and keeping keyfiles

mkdir ~/vpn_repo
cd ~/vpn_repo

* From here on, everything happens at ~/vpn_repo !!! *

Fetch & prepare easy-tls

wget https://raw.githubusercontent.com/TinCanTech/easy-tls/refs/heads/master/easytls
chmod 750 easytls

For creating all the needed OpenVPN server files

cat >server.sh

#!/bin/bash

# cert & ca expiry 10 years
export EASYRSA_KEY_SIZE=2048
export EASYRSA_CA_EXPIRE=3650
export EASYRSA_CERT_EXPIRE=3650

TARGET=$1
USER=$2
PASS=$3

if [ -z $TARGET ]
then
 echo "Give servername as arg"
 exit
fi

make-cadir $TARGET
if [ $? -eq 0 ]
 then
 cd $TARGET

 # build server cert package
 ./easyrsa init-pki
 echo $TARGET | ./easyrsa build-ca nopass
 ./easyrsa gen-dh
 echo yes | ./easyrsa build-server-full $TARGET nopass

 # prepare tls-auth key
 if [[ ! -d pki/easytls ]]
 then
 ../easytls init-tls
 ../easytls build-tls-auth
 fi

 cd ..
 mkdir -p out
 # symlink all files needed on server side
 ln -srf $TARGET/pki/private/$TARGET.key out/
 ln -srf $TARGET/pki/ca.crt out/${TARGET}_ca.crt
 ln -srf $TARGET/pki/easytls/tls-auth.key out/${TARGET}_tls-auth.key
 ln -srf $TARGET/pki/dh.pem out/${TARGET}_dh.pem
 ln -srf $TARGET/pki/issued/$TARGET.crt out/

 echo "#### OpenVPN server files"
 find out | tail +2
 echo "####"
 echo "Copy these files to server /etc/openvpn/server/"
fi

For creating client profiles

cat >gen_user.sh

LUKS basics

Mon, 24 Mar 2025 00:00:00 +0000

Prepare storage device from zero

cryptsetup luksFormat /dev/sdx
cryptsetup luksOpen /dev/sdx cryptoblob
mkfs.ext4 /dev/mapper/cryptoblob

Test slot/passphrase

cryptsetup --verbose open --test-passphrase /dev/sdx

Change volume password

cryptsetup luksChangeKey -S 0 /dev/sdx

Update old LUKS KDF for safer one

Older LUKS volumes can have unsafe/poor key derivation function in use.

cryptsetup luksHeaderBackup /dev/sdx --header-backup-file /tmp/luksheader

cryptsetup luksDump /dev/sdx

# If type 1 (old):
cryptsetup convert /dev/sdx --type luks2
cryptsetup luksConvertKey /dev/sdx --pbkdf argon2id

# If goofen uppen, restore old header:
cryptsetup luksHeaderRestore /dev/sdx --header-backup-file /tmp/luksheader

Thunderbolt networking

Mon, 24 Mar 2025 00:00:00 +0000

Setup

Connect USB4/TB cable between computers. Stay vigilant, most cables are not USB4/TB capable.

Host A:

modprobe thunderbolt-net
ip a add 10.10.10.10/24 dev thunderbolt0

Host B:

ip a add 10.10.10.11/24 dev thunderbolt0

Test network

# Host A:
iperf -s

# Host B:
iperf -i 10 -c 10.10.10.10

Results

------------------------------------------------------------
Client connecting to 10.10.10.10, TCP port 5001
TCP window size: 16.0 KByte (default)
------------------------------------------------------------
[ 1] local 10.10.10.11 port 53846 connected with 10.10.10.10
[ ID] Interval Transfer Bandwidth
[ 1] 0.0000-10.0000 sec 21.8 GBytes 18.7 Gbits/sec
[ 1] 0.0000-10.0019 sec 21.8 GBytes 18.7 Gbits/sec

Usage

Use the interfaces as any other network over ssh, rsync, netcat, scp etc

Terminal

Wireguard VPN networking

Background

Network topology

Server

Roaming peer 1

Package setup for all hosts

Key generation

Server

Peer 1

Server setup

Allow traffic at udp/12345

Public server config

Dump your own L3 CDM

Install android studio by whatever means necessary

Prepare a virtual device

Prepare host and host software

Download or build frida server apk

Launch the android virtual device from studio

Check that emulator is visible to adb

Run frida-server on virtual device

Run keydumper in python venv (keydive)

What, why?

Can’t remember shit and I’m tired of (re)learning same same but same all the time.

NVRAM/efivarfs is full

Check out current NVRAM entries

If you want to remove some useless entry (for example USB CD)

Clean up duplicate boot order entries

Writing bootable ISO images to USB media

Writing image to USB media

Option 1: cat

Option 2: dd

Convert android screenshots to AVIF

Install tools

Profiling android battery usage

Initiate logging

Test ethernet cables with two local interfaces

Android <-> PC notepad style file editor/sync

General info

Android setup

Linux setup

Place editor script into PC ~/bin/memo

SSH client config setup with LAN/VPN aliasing

Usage

OpenVPN networking

Package setup for building files at any host computer

Package setup for OpenVPN server

Create directory for building and keeping keyfiles

*** From here on, everything happens at ~/vpn_repo !!! ***

Fetch & prepare easy-tls

For creating all the needed OpenVPN server files

For creating client profiles

LUKS basics

Prepare storage device from zero

Test slot/passphrase

Change volume password

Update old LUKS KDF for safer one

Thunderbolt networking

Setup

Test network

Results

Usage

* From here on, everything happens at ~/vpn_repo !!! *