My name is Philipp C. Heckel and I write about nerdy things.
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Blog


  • Dec 04 / 2015
  • 4
Administration, Code Snippets, Linux, Scripting, Security

Snippet 0x0D: Let’s Encrypt – 5 min guide to set up cronjob based certificate renewal

Let’s Encrypt was officially released to the open public today. That means the Internet can finally get free, trusted SSL/TLS certificates. This quick guide shows how to set up Let’s Encrypt with auto-renewal through a cronjob — using the simp_le client, an alternative client developed by one of the same authors who develop the official client.

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  • Oct 18 / 2015
  • 8
Administration

How-To: Create a Debian package and a Debian repository

Debian packages and repositories are everywhere, yet many people don’t understand that creating them is actually pretty easy. While there are dozens of tutorials out there, none of them seemed to really show a good step-by-step. This is a quick tutorial on how to create a Debian package from scratch, and how to create a simple Debian repository.

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  • Aug 22 / 2015
  • 1
Code Snippets, Programming

Snippet 0x0C: Load multiple composer.json files at runtime

Remember the times when we copied PHP “libraries” into our project folder, or we copy and pasted code from some random site into our project? Those times are over. Composer and Packagist are the modern way to manage PHP dependencies. They are great. Almost as good as The Maven repos and their build tools in the Java world. However, while Composer is really good at managing the dependencies of a single project, i.e. one composer.json file, it does not play well if you want to plug different projects together at runtime. And by “does not play well” I mean it simply doesn’t work if you have two or more composer.json files. This quick post demonstrates a way around this limitation. Quick and dirty. Just like the foundations of PHP :-)

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  • May 04 / 2015
  • 3
Linux, Programming, Security

OpenSSH ‘AuthorizedKeysCommand’ with ‘fingerprint’ argument (Patch for OpenSSH 6.6p1)

Many of us developers or system administrators use OpenSSH’s public key authentication (aka password-less login) on a daily basis. The mechanism works based on public key cryptography: By adding a RSA/DSA public key to the authorized_keys file, the user with the matching private key can login without a password. The mechanism works great for a couple of hundred, thousands and even 100k thousand users (tested, login takes ~2sec).

But what if there are more keypairs, say, a million users, or a more flexible approach is desired? Maybe with an LDAP or a database backend? Think of GitHub and how they do their ssh git@github.com ... login! This blog post shows you how to do that by patching OpenSSH’s AuthorizedKeysCommand option to support an additional fingerprint argument.

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  • Mar 24 / 2015
  • 2
Code Snippets, Linux, Scripting

Snippet 0x0B: Bash completion with sub-commands and dynamic options

Every system administrator, most programmers and countless of command line surfing Linux/Mac users use it every day without thinking twice. Hitting the tab key twice, [TAB][TAB], has become the most common thing in the world. Bash completion is the magic behind the tab key. It’s easy to use, but it’s a pain to write. This tiny post demonstrates how to write scripts for bash completion, with sub-commands and dynamic parameters. A working script is embedded in my open source file sync software Syncany.

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  • Mar 22 / 2015
  • 2
Linux, Scripting, Security

Circumvent Internet blockages/filters/censorship with socksproxy and netcat

These days, ISPs are often forced to block the access to certain sites, because their government considers these sites dangerous and/or illegal. While one could certainly discuss the usefulness of such measures in great detail, this tiny post focuses on the more interesting subject of how to circumvent these blockages. It’s not a lenghty post, and it doesn’t show all the ways there are, but I’ll show two simple ways to circumvent Internet non-DNS-based filters.

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  • Jan 24 / 2015
Code Snippets, Programming

Snippet 0x09: Reading a ZIP/JAR file with PHP (here: a JAR manifest)

For my open source file sync software Syncany, I have integrated the automatic plugin build process (we provide plugin repository and an easy plugin API to download plugins) with an upload to the Syncany API server. Plugins (JAR files) are uploaded by Travis (example: Samba plugin) to the Syncany server. To serve meta data on through the plugin API, I need to parse the plugins’ MANIFEST.MF files and store them in a database.

This tiny blog post shows you how to read a ZIP/JAR file entry with PHP, and parse JAR manifest (MANIFEST.MF) file. That’s it. Nothing fancy.

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  • Oct 30 / 2014
  • 1
Code Snippets, Programming

Snippet 0x08: HTTP Basic Auth for secure WebSocket connections (with Undertow)

For my open source file sync software Syncany, I use the embedded web server and web socket server Undertow to provide a websocket and REST based interface by the Syncany daemon. Syncany clients (such as the GUI, or potentially a web interface) connect to this daemon, send requests and receive asynchronous events. Syncany’s GUI client also uses the Undertow websocket client to connect to the above mentioned daemon.

To authenticate the websocket client with the daemon, the simple HTTP basic authentication mechanism over HTTPS is used. This tiny post shows you how to authenticate against a websocket server with HTTP basic auth using the Undertow websocket client.

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