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Søren Poulsen

Photo of Søren Poulsen Hey folks! I spent a good part of my childhood coding m68k assembler on the legendary A500. It was blessed with a hardware manual and an inspiring community of enthusiasts who loved to hack the Blitter and Copper and share code for realtime 3D and soundtrackers. Well thats a while back but I'm still having fun with computing. Key topics on my blog are Linux, Java and Security. Hope you find something useful here.
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Block IP addresses on Apache HTTP Server 2.4

With the Apache HTTP Server 2.4, clients can be blocked based on an IP number, an IP subnet, a domain or a top level domain.

JAX-WS SOAP Web Service Client For Java 11 With Maven

The JAX-WS API, runtime and tools has been removed from JDK 11. However the exact same implementation, called Eclipse Metro, is available through Maven Central and we can still use a Maven plugin that wraps the wsimport tool to generate a SOAP web service client as we shall see in this post.

Set up SLF4J with logback's AsyncAppender

This post is a quick overview of how to set up the Simple Logging Facade for Java (SLF4J) with logback's AsyncAppender in a Maven project.

Dell XPS 13 9305 with Ubuntu 20.04.2 LTS

I needed to replace an aging Dell XPS 13 with the latest XPS 13 9310 Developer Edition that comes preinstalled with Ubuntu 20.04 LTS, but unfortunately it wasn't for sale in the Nordic countries.

Extend The Range Of A Wireless Network By Turning A Spare Router Into A Simple Wireless Access Point

If you have a spare WiFi router lying around, you can use it to extend the range of your wireless network by turning it into a simple Wireless Access Point, that is wired to your main WiFi router.

Install OpenWRT on Linksys WRT1900ACS

The Linksys WRT1900ACS is a popular router for running the OpenWRT firmware. It has been battle tested by the community and is a very robust platform.

Install OpenWRT on Linksys WRT3200ACM

Hey you with the Linksys router! OEM firmwares are chock-full of security vulnerabilities that never get fixed and blatant factory backdoors. Flash it with the OpenWRT Linux firmware now. Get it done :)

Quick install Tomcat on Ubuntu

Let's grab the default Tomcat and Java APT packages on Ubuntu.

Self Hosted Music Streaming with Airsonic on Ubuntu

Your music library will probably stay with you for life. Streaming providers likely won't. When you have had enough with streaming providers and you are ready to take control of your music library, it's time to self host your music streaming with Airsonic.

Quick Minimal Firewall on Ubuntu With Iptables

Let's create a minimal set of iptables rules and a two-liner script that can restore the rules on restart.

Calculate HMAC-Sha256 with Java

Calculating a Hmac with the Java Cryptographic Architecture is only a few lines of code, despite a bit of complexity added from the API's design goal of being implementation independent and extensible.

Install DNSCrypt-Proxy 2 on Ubuntu 16.04

DNSCrypt-Proxy version 2 implements the DNSCrypt v2, DNSCrypt v1 and DNS-over-HTTP/2 protocols that encrypt and authenticate DNS traffic between the DNS resolver and the user's PC.

Create A Spring Web Service Client With Maven

This description on how to create a Spring web service client is based on a sample Maven project hosted on GitHub. You are welcome to clone the project, it's linked in the bottom section.

Create A JAX-WS Service Client With Maven

With just 4 files we have a full Maven project that can generate a JAX-WS service client and do an automated integration test. The project is available on GitHub and is linked in the last section. This post just adds a bit of prose on how it works.

Mock Services For Maven Integration Tests With The SOAPUI Plugin

SoapUI has this nifty little Maven plugin that is capable of running mock services during Maven's test phase. This enables us to write integration tests that do real network I/O and marshall/unmarshall real XML requests and responses. Not only do we get to exercise more of our integration code during tests but it's also easier - is there anything worse than mocking complex response patterns in code?

Install Apache Tomcat 9 on Ubuntu 16.04 for production

For this production setup we are going with the binary distributions of the Oracle Java Standard Edition version 8 and Apache Tomcat version 9.

Securing a Google Account with the Nitrokey FIDO U2F

Google Accounts can be secured with Google's 2-Step Verification. In this post we will set up a Nitrokey FIDO U2F as a 2nd factor for 2-Step Verification. The Nitrokey distinguishes itself from Yubico's U2F Security Key by having open source hardware and firmware.

Flashing Android firmware on BQ Aquaris M10 Ubuntu Touch FHD

In this post we flash the latest Android firmware available for the BQ Aquaris M10 Ubuntu Touch FHD. Prerequisites is a PC with Ubuntu 16.04 LTS connected to the tablet with a USB cable.

Using OWASP Dependency Check with Maven

Using software components with known security vulnerabilities was ranked at no. 9 on the OWASP Top 10 Security Risks for 2017 and in the recent 2021 update it was promoted to no. 6 with the new title "Vulnerable and outdated components".

DNSCrypt-proxy on Ubuntu 16.04

DNS is the weak link of the Internet. Early versions of the DNS security extension didn't scale with the growth of the Internet and for most users DNS still doesn't offer any security for the "last mile" from the DNS Resolver, typically hosted at the Internet Service Provider, to the user's PC.

Install LEDE on a Linksys WRT1200AC router

The Linksys WRT1200AC is one of the latest successors to the legendary WRT54G that sparked the OpenWRT Linux based router firmware. Linksys claims that the WRT1200AC is "developed for use with OpenWRT", so it seems like a safe bet for anyone who want's to run Linux on their router.

Setting up a Samsung CLP-410 Printer on Ubuntu

Setting up a Samsung's CLP-410 Printer on Ubuntu is a breeze because it supports mDNS whereby the Printer broadcasts its presence on the local network. Ubuntu ships with the Avahi service that detects such mDNS devices and makes the information available to Ubuntu's printing system.

Arquillian with Apache TomEE remote adapter

With Arquillian we can package a JavaEE application together with a JUnit test case, deploy it to a container and run the test case inside the container. Arquillian is able to pull this off in a platform independent manner.

Using a Nitrokey Pro from another computer

Using a Nitrokey Pro from another computer than where it was set up originally, can be as simple as copying the ~/.gnupg folder, except the random seed file, to the new computer. The procedure described in detail in this post however, involves importing the public key from a key server and re-generating the proxy for the private key on the new computer.

IRC through SSH tunnel

IRC servers happily share our IP address with other users on the server. To retain a bit of privacy we can tunnel IRC though SSH, thus only exposing the IP address of the machine running the SSH daemon.

Dell XPS Developer Edition resume WIFI after suspend on Ubuntu 16.04

Dell has been pushing fixes for the Dell XPS Developer Edition to upstream projects to make them available to all new releases of Linux distributions, but one thing that isn't quite working with the latest Ubuntu 16.04 is resuming WIFI after suspend. It's easily fixed with a little Systemd service.

Use a GnuPG Primary key from a USB drive

Following a previous post we moved our primary key off the harddrive onto an encrypted USB flash drive for safe keeping. Occasionally we need to use our primary key, for instance to sign other people's public key. So how do we bring our primary key back "online"?

Nexus 9 file transfer via USB on Ubuntu

The Nexus 9 transfers files via USB using the Media Transfer Protocol (MTP). Ubuntu 16.04 supports this out of the box, whereas with older versions of Ubuntu, we have to set up a virtual filesystem to expose the MTP interface of the Nexus 9. This post covers both Ubuntu 16.04 and Ubuntu 12.04.

Sandboxing Tomcat with a Security Manager

With Java's Security Manager we can sandbox Apache Tomcat to protect the host operating system and to some degree also segregate and protect the various code bases running inside Tomcat.

Install Tomcat 8 on Ubuntu

In this post we go through the installation of Tomcat 8 on Ubuntu 15.10 for production use. When the installation is done, Tomcat will be running as a service that is managed with Systemd.

Install Apache Maven on Ubuntu

Apache Maven is available from Ubuntu's package repository, but it's trailing behind the latest and greatest, so let's download and install Maven directly from https://maven.apache.org

Install Eclipse on Ubuntu

Eclipse is available through Ubuntu's Universe repository, but if you want the latest and greatest then grab a copy directly from www.eclipse.org/downloads.

Install Oracle's Java Development Kit on Ubuntu

Oracle's proprietary Java Development Kit takes a bit of effort to install because it's not available through Ubuntu's official package repositories, but in a commercial setting it's often the preferred JDK.

Securing GnuPG keys on a Nitrokey Pro

A GnuPG key can be secured by storing it on a USB device with OpenPGP Card support such as the Nitrokey Pro.

Protect Gmail with Yubico's U2F Security Key

If your Gmail account matters to you, then Two-factor authentication is a prudent choice.

UTF-8 encoding a JSP with Spring MVC

So how does Spring MVC set the response encoding of a JSP to UTF-8? It's a trick question. The short answer is that it doesn't!

Encrypting a USB flash drive on Ubuntu

Using an encrypted USB flash drive is more or less transparent on Ubuntu. In the Nautilus file manager the drive mounts automatically and looks and works the same as any other drive. The only noticeable difference is that you will be prompted for a passphrase when the drive mounts.

Encryption with GnuPG on Ubuntu

The GnuPG commandline tool can encrypt any data for storage or transport. It uses a hybrid scheme of Public Key Crypto and symmetric encryption.