Let's encrypt it all

David Runge — Thu, 29 Sep 2016 18:00:00 GMT

For a couple of months now I have been using Let's Encrypt to generate free and valid certificates for all the services I run.
In many places the free Certificate Authority (short CA) has spread like wild-fire. From small to large scale services, many adopted it and the amount of issued certificates has grown over 1 million in just four months.
As a visitor to this website you have probably noticed the small green lock sign next to the address bar. The certificate used for this website is accepted to be valid by your browser (and also by your operating system).
If you're up for some background knowledge, just read on. If you're up for some hands-on technical stuff, jump right on to the howto.
Just note: This is a veeeeeeery long article in any case.

SSH tunnel with single hop, using systemd-networkd and autossh

David Runge — Sun, 01 Feb 2015 18:00:00 GMT

Recently I had the pleasure of setting up a SSH tunnel between two virtual machines that share no route and are located in two different subnets.
They can however reach each other via SSH, hopping their host.
Let's assume the following setup:

client1 (Arch Linux) has 10.0.5.2/24
client2 (Arch Linux) has 10.0.6.2/24
host (Debian) is 10.0.5.1/24 to client1 and 10.0.6.1/24 to client2

As I needed the two clients to be able to send mail to each other and reach each others' services, I did some digging and opted for a SSH connection using TUN devices (aka. "poor man's VPN").

The following is needed to set this up:

root access on both virtual machines (client1 & client2)
a user account on the host system
SSH (OpenSSH assumed) installed on all three machines

SleepMap (Posts about postfix)

Let's encrypt it all

SSH tunnel with single hop, using systemd-networkd and autossh