## Use Python to Generate Discord Invite ULRs en masse

When creating invitations to Discord servers – or "guilds" how they seem to called internally – you can configure some limits. For example, you can limit the number of times a link can be used to join a server or you can configure an expiry date. The default setting for the time limit is 7 days btw, which is why most links are expired when you come back to them after some time. I was in the situation that I wanted to invite a limited number of people to a Discord server and each should only receive a link that can only be used once. So in some sense, I wanted to create personalized invite links, which doesn't seem to be a use case that's supported out of the box. So let's use Python!

## Machine Learning for Language Detection in Python with scikit-learn

I recently played around with scraping public Telegram channels and finally want to do something with the data. In particular, I wanted to play around with Named Entity Recognition (NER) and Sentiment Analysis on the content of the Telegram posts. I think this will probably work much better when you do it for each language separately. So before we answer the question "what's this post about?" or "how angry is the person in the post?", let's answer the question "what language is the post in?" first. And we'll do it while warming up with that hole machine learning (ML) topic. Be aware: I have no idea what I'm doing. Do you want to know more?

## VoiceMeeter for Audio Routing on Windows

This blog post will cover my audio setup on Windows. It's core component is called VoiceMeeter which is a virtual audio mixer for Windows developed by Vincent Burel under the company label "VB-Audio". This blog post will focus on the fact that it makes virtual microphones and virtual speakers available which in turn can be used by all program running on your computer. Do you want to know more?

## Using Windows Sandbox for Malware Analysis

**Disclaimer:** If you are not running Windows on your host, you might not get anything out of this post. Sorry Tux. I am convinced that the Windows Sandbox is one of the best virtualization solutions to do dynamic malware analysis (for Windows malware, at least). The reason is quite simple: Distinguishing a Windows 10 Sandbox instance from the actual underlying Windows 10 install should be very difficult for malware. Specifically if the host is running on HyperV with Guarded Host enabled, my current understanding is that there are little to no differences between the two, but they are neatly isolated from one another. The configuration options are limited, but you can easily cook up a config that launches a WindowsSandbox instance that has all the tools you need for some basic unpacking & dynamic analysis. This is what my malware analysis sandbox looks like at launch: I have successfully executed a number of samples that evade execution in other virtualized environments. That's a far cry from rigorous testing, so take my praise with a grain of salt. Still, it might be worth a try, the setup is really easy. Do you want to see my config?

## FrOSCon 2021 Vortrag – Der Cyber-Bankraub von Bangladesch

(English-only readers can safely ignore this post) I'll be talking at FrOSCon this year again and try to take a stab at a topic that does not _only_ involve technical topics but will also tell the story of a bank heist. This heist wasn't supported by getaway cars and pistols but was solely carried out through cyber-means. The talk is in German though. * Source Code of LaTex Presentation: https://github.com/larsborn/FrOSCon2021-Ghidra-Bangladesh-Talk * Handout PDF: FrOSConTalk2021-Ghidra-Bangladesh * FrOSCon schedule entry: https://programm.froscon.de/2021/events/2670.html * Recording on media.ccc: https://media.ccc.de/v/froscon2021-2670-der_cyber-bankraub_von_bangladesch

## Install Ghidra 10.0.1 on Ubuntu 20

I idly googled for the title and couldn't find code that I can insipidly paste into a console window. So I prepared it here for fellow travelers (and my future self):
wget 'https://github.com/NationalSecurityAgency/ghidra/releases/download/Ghidra_10.0.1_build/ghidra_10.0.1_PUBLIC_20210708.zip'
unzip ghidra_10.0.1_PUBLIC_20210708.zip
sudo apt install default-jdk
./ghidra/ghidraRun


## Prettier Struct Definitions for Python CTypes

I was writing some Python code that uses [ctypes][] for interfacing with the [Windows ToolHelp API](https://docs.microsoft.com/en-us/windows/win32/api/_toolhelp/). Specifically, I had to [define a Python equivalent][structs] for the [PROCESSENTRY32](https://docs.microsoft.com/en-us/windows/win32/api/tlhelp32/ns-tlhelp32-processentry32) struct. Now, the [ctypes][] [struct definitions][structs] are a little annoying because they do not give you type hints. You can add the type hints _on top_ of the _fields_ attribute but that looks a little silly because you _literally_ [write everything twice][wet]. In Python 3.7+1, you can solve this using a metaclass, and one stigma of metaclasses is that they have very few applications, so I decided to blog about this one:
class FieldsFromTypeHints(type(ctypes.Structure)):
def __new__(cls, name, bases, namespace):
from typing import get_type_hints
class AnnotationDummy:
__annotations__ = namespace.get('__annotations__', {})
annotations = get_type_hints(AnnotationDummy)
namespace['_fields_'] = list(annotations.items())
return type(ctypes.Structure).__new__(cls, name, bases, namespace)

and now you can write:
class PROCESSENTRY32(ctypes.Structure, metaclass=FieldsFromTypeHints):
dwSize              : ctypes.c_uint32
cntUsage            : ctypes.c_uint32
th32ProcessID       : ctypes.c_uint32
th32DefaultHeapID   : ctypes.POINTER(ctypes.c_ulong)
th32ModuleID        : ctypes.c_uint32
th32ParentProcessID : ctypes.c_uint32
pcPriClassBase      : ctypes.c_long
dwFlags             : ctypes.c_uint32
szExeFile           : ctypes.c_char * 260

The metaclass simply deduces the _fields_ attribute of the new class for you before the class is _even created_. It might make sense to think of metaclasses as "class creation hooks", i.e. you get to modify what you have written before the class is actually being defined. The following bit is just to be compatible with [PEP-563](https://www.python.org/dev/peps/pep-0563/):
        from typing import get_type_hints
class AnnotationDummy:
__annotations__ = namespace.get('__annotations__', {})
annotations = get_type_hints(AnnotationDummy)

And then, the following is the actual magic line:
        namespace['_fields_'] = list(annotations.items())

This adds the attribute _fields_ before the class is created. [ctypes]: https://docs.python.org/3/library/ctypes.html [structs]: https://docs.python.org/3/library/ctypes.html#structures-and-unions [wet]: https://en.wikipedia.org/wiki/Don%27t_repeat_yourself Do you want to know what I was coding?
1. Starting in Python 3.7, dictionaries keep the insertion order. []

## Zabbix: Use Low-Level Discovery for Software Update Notifications

Assume you have an already running Zabbix instance that is able to send notifications – via e-Mail or Signal for example. The goal of this post is, to use such an instance to get notified whenever there is a new release for a software you may have installed on some of your machines. Do you want to know more?

## WordPress Child Themes for the Working Human

Create a new directory in wp-content/themes — let's call it danktheme in this example. Create two files in that directory: style.css and functions.php with the following contents:
/*
Template:     twentytwentyone
Version:      1.0.0
*/

and
<?php
function my_theme_enqueue_styles()
{
wp_enqueue_style('danktheme', get_stylesheet_uri());
}

That's it: now you can select "Your Themename" in the admin interface. If you don't want to use twentytwentyone as the parent theme — because it's not the most recent one when you read this, for example — replace it in the style.css. Yes, in the stylesheet, I'm not making this up, rules are rules.

## 3D Modeling for 3D Printing for Total Noobs

I was always fascinated with the idea of turning ideas into data within a computer and then turning this data into a physical object. With this, I'm probably not alone given that 3D printing is all the rage in nerd world. After some googeling around and buying a printer on Amazon Prime day, I devised the following plan to learn 3D printing as a skill: 1. print sample shape shipped with the printer 2. print model from the internet 3. modify existing model 4. create a model from scratch The intention behind this plan was to spread out different problems and technologies involves as much as possible. So it's never a daunting task. Show the steps!

## Do Not Enforce Email Address During CTFd Registration

CTFd is a Python-based open-source Capture The Flag (CTF) web app. I wanted to use it in a context where I didn't want to collect email addresses of the registering users. To archive this, I decided to take the easy way and hack myself around the problem: just hide the email-field in the registration form and generate a random address for every registration. Show me the code!

## Raspberry Pi Camera for Sourdough Monitoring

All right, the last step to complete the great Sourdough Monitoring Project (SMP): capturing actual footage. We don't need a real video but just a sequence of still images. The goal is to collect enough of those on disk to later be able to assemble them into a time-laps video of the dough growing. First I'll show you how to enable camera support in software, then how to attach the camera, and finally finally how to capture images to disk. As a bonus, I'll share a PHP script you can use to receive images on a server on the internet so you can look at your dough from the other side of the world. Take a peek.

## Temperature Measurement on Raspberry Pi

This is me again, having no idea about electronics and trying to get a Raspberry Pi to record the temperature of its surroundings in order to better control the environment of the previously mentioned sourdough. Get bakin'!