I got myself an Aranet4 device to monitor CO2 levels in my office. The monitor gives pretty accurate readings and has very low energy demands (due to the e-ink display) (here’s the datasheet). While the intended way to read the measurements is to use the mobile app, it’s always good to be able to access the raw data yourself; you get to store as many readings as you like (otherwise limited to past 7 days) and can analyse them in any way you want. ...
A couple of months ago I built a JavaScript application that allows adding points and labels to locations on a building floorplan. The whole canvas (not HTML <canvas>) is a SVG document inside an HTML document and points/objects/labels/etc. are added to that canvas as native SVG elements. Users can add/move objects on the floorplan but also zoom and pan the floorplan itself. When performing these actions it is important to transform coordinates from the screen or viewport (like the position of your mouse/fingers) into coordinates that make sense in your SVG element’s coordinate system. ...
Let’s say you have a long-running Python script that should run uninterrupted or perform a graceful shutdown should a user decide to terminate it ahead of completion. By default, sending an interrupt (usually by pressing <Control-C>) to a running Python program will raise a KeyboardInterrupt exception. One way of (gracefully or not) handling interrupts is to catch this specific exception. For example like this: while True: try: do_your_thing() except KeyboardInterrupt: clean_up() sys.exit(0) This generally works fine. However, you can still trigger another KeyboardInterrupt while the clean_up is running and thus interrupt the clean-up process. Also, as interrupts might be sent accidentally (ever cancelled the wrong script because you thought you were in a different pane?), it would be nice to let the user confirm that the script should indeed be interrupted. ...
Currently, there’s a lot of hype around the behavior of Python’s tarfile module for extracting archives. In short: tarfile will not sanitize filenames in archives to prevent directory traversal attacks. For example, creating an archive and adding a file with a leading ../ will make the extract* methods create that file in a directory above the current one. This way (or by using an absolute path starting with /), a file can be written to an arbitrary location (given that the user executing the code has the according write privileges). ...
I recently came across an nginx server that had a vulnerable alias configuration which allowed anyone to read files outside the intended directory. In the following post I will describe the misconfiguration and provide demo files so that you can experiment with it yourself. The general issue was originally highlighted a few years ago in a BlackHat presentation (Breaking Parser Logic!, Orange Tsai) and apparantly first shown even earlier. While the linked presentation only has a couple of slides on this particular issue it’s worth checking out in full. The docker setup Let’s say we have a PHP application that should be served through nginx. To quickly get things running we configure our setup via the following docker-compose.yml file: ...