Software Hacks

912 Articles

Proof That find + mkdir Are Turing-Complete

August 5, 2024 by 10 Comments

Data manipulation is at the heart of computation, and a system is said to be Turing-complete if it can be configured to manipulate data in a way that makes implementing arbitrary computation possible. [Keigo Oka] shared a proof that find and mkdir together are Turing-complete, which is to say, a system with only GNU’s find and mkdir has access to enough functionality to satisfy the requirements of Turing completeness, which ignores questions of efficiency or speed.

[Keigo Oka]’s first attempt at a proof worked to implement Rule 110, an elementary cellular automata configuration that has been shown to be Turing-complete, or ‘universal’, but has been updated to implement a tag system as it’s proof, and you can see it in action for yourself.

Seeing basic utilities leveraged in such a way illustrates how computation is all around us, and not always in expected places. We’ve also seen Turing-complete origami and computation in cellular automata.

LightBurn Turns Back The Clock, Bails On Linux Users

July 31, 2024 by 219 Comments

Angry Birds, flash mobs, Russell Brand, fidget spinners. All of these were virtually unavoidable in the previous decade, and yet, like so many popular trends, have now largely faded into obscurity. But in a recent announcement, the developers of LightBurn have brought back a relic of the past that we thought was all but buried along with Harambe — popular software not supporting Linux.

But this isn’t a case of the developers not wanting to bring their software to Linux. LightBurn, the defacto tool for controlling hobbyist laser cutters and engravers, was already multi-platform. Looking forward, however, the developers claim that too much of their time is spent supporting and packaging the software for Linux relative to the size of the user base. In an announcement email sent out to users, they reached even deeper into the mid-2000s bag of excuses, and cited the number of Linux distributions as a further challenge:

The segmentation of Linux distributions complicates these burdens further — we’ve had to provide three separate packages for the versions of Linux we officially support, and still encounter frequent compatibility issues on those distributions (or closely related distributions), to say nothing of the many distributions we have been asked to support.

We’re not sure how much of their time could possibly be taken up by responding to requests for supporting additional distributions (especially when the answer is no), but apparently, it was enough that they finally had to put their foot down — the upcoming 1.7.00 release of LightBurn will be the last to run on Linux.

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Reverse Engineering A Soundsystem’s API

July 31, 2024 by 12 Comments

We’ve all been stymied by a smart thermostat, coffee maker, or other device which would work fine on its own but ultimately seems to be worse off for having an Internet connection —  so when something actually pulls off this feat it’s quite noteworthy. [James] has a powerful set of connected speakers and while they don’t have all of the functionality he needed built-in, an included web API at least allowed him to build in the features he wanted.

The major problem with these speakers isn’t that they’re incredibly loud (although they are), but rather that the wide range of available volumes for such a loud soundsystem doesn’t leave a lot of fine adjustment in the range where [James] typically uses these speakers. To tackle the problem, he first found the web interface the speakers present and then discovered a somewhat hidden application programming interface (API) within that allows for some manual control. He built a second website which serves as a volume slider within the range he wants, and the web server sends this volume to the speakers via this API which allows much finer control than the built-in user interface.

Having a usable API included with Internet-connected devices is not always the case, although it’s a great model for any company wanting to allow their customers better control of the products they buy. If you need to roll out your own API for connected devices that don’t have one already, take a look at [Sean Boyce]’s guide from 2019.

Getting Linux Process List Without Forking Using Just A Bash Script

July 29, 2024 by 16 Comments

The ps command is extremely useful when you want to get some quick information on active system processes (hence the name), especially followed by piping it into grep and kin for some filtering. One gotcha is of course that ps doesn’t run in the current shell process, but is forked off into its own process, so what if everything goes wrong and you absolutely need to run ps aux on a system that is completely and utterly out of fresh process IDs to hand out? In that scenario, you fortunately can write a shell script that does the same, but all within the same shell, as [Isabella Bosia] did, with a Bash shell script.

The how and why is mostly covered in the shell script itself, using detailed comments. Initially the hope was to just read out and parse the contents of /proc/<pid>/status, but that doesn’t have details like CPU%. The result is a bit more parsing to get the desired result, as well as a significant amount of cussing in the comments. Even if it’s not entirely practical, as the odds of ending up on a system with zero free PIDs are probably between zero and NaN, but as an ‘entertaining’ job interview question and example of all the fun things one can do with shell scripting it’s definitely highly recommended.

A 64-bit X86 Bootloader From Scratch

July 14, 2024 by 20 Comments

For most people, you turn on your computer, and it starts the operating system. However, the reality is much more complex as [Thasso] discovered. Even modern x86 chips start in 16-bit real mode and there is a bit of fancy footwork required to shift to modern protected mode with full 64-bit support. Want to see how? [Thasso] shows us the ropes.

Nowadays, it is handy to develop such things because you don’t have to use real hardware. An emulator like QEMU will suffice. If you know assembly language, the process is surprisingly simple, although there is a lot of nuance and subtlety. The biggest task is setting up appropriate paging tables to control the memory mapping. In real mode, segments have access to fixed 64 K blocks of memory unless you use some tricks. But in protected mode, segments define blocks of memory that can be very small or cover the entire address space. These segments define areas of memory even though it is possible to set segments to cover all memory and — sort of — ignore them. You still have to define them for the switch to protected mode.

In the bad old days, you had more reason to worry about this if you were writing a DOS Extender or using some tricks to get access to more memory. But still good to know if you are rolling your own operating system. Why do the processors still boot into real mode? Good question.

Ask Hackaday: Has Firefox Finally Gone Too Far?

July 14, 2024 by 119 Comments

In a world where so much of our lives depend on the use of online services, the web browser used to access those services becomes of crucial importance. It becomes a question of whether we trust the huge corporate interests which control this software with such access to our daily lives, and it is vital that the browser world remains a playing field with many players in the game.

The mantle has traditionally fallen upon Mozilla’s Firefox browser to represent freedom from corporate ownership, but over the last couple of years even they have edged away from their open source ethos and morphed into an advertising company that happens to have a browser. We’re asking you: can we still trust Mozilla’s Firefox, when the latest version turns on ad measurement by default?

Such has been the dominance of Google’s Chromium in the browser world, that it becomes difficult to find alternatives which aren’t based on it. We can see the attraction for developers, instead of pursuing the extremely hard task of developing a new browser engine, just use one off-the-shelf upon which someone else has already done the work. As a result, once you have discounted browsers such as the venerable Netsurf or Dillo which are cool as heck but relatively useless for modern websites, the choices quickly descend into the esoteric. There are Ladybird and Servo which are both promising but still too rough around the edges for everyday use, so what’s left? Probably LibreWolf represents the best option, a version of Firefox with a focus on privacy and security.

We’re interested in your views on this topic, because we know you’ll have a lot to say about it. Meanwhile if you’re a Firefox user who’s upgraded to version 128 and you’re not sure what to do, don’t panic. Find the settings page, go to “Privacy and Security”, and un-check the “Website Advertising Preferences” checkbox.

Ticketmaster SafeTix Reverse-Engineered

July 11, 2024 by 49 Comments

Ticketmaster is having a rough time lately. Recently, a hacker named [Conduition] managed to reverse-engineer their new “safe” electronic ticket system. Of course, they also had the recent breach where more than half a billion accounts had personal and financial data leaked without any indication of whether or not the data was fully encrypted. But we’re going to focus on the former, as it’s more technically interesting.

Ticketmaster’s stated goals for the new SafeTix system — which requires the use of a smartphone app — was to reduce fraud and ticket scalping. Essentially, you purchase a ticket using their app, and some data is downloaded to your phone which generates a rotating barcode every 15 seconds. When [Conduition] arrived at the venue, cell and WiFi service was totally swamped by everyone trying to load their barcode tickets. After many worried minutes (and presumably a few choice words) [Conduition] managed to get a cell signal long enough to update the barcode, and was able to enter, albeit with a large contingent of similarly annoyed fans trying to enter with their legally purchased tickets.

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