Unionize Your Variables – An Introduction To Advanced Data Types In C

March 2, 2018 by Sven Gregori 61 Comments

Programming C without variables is like, well, programming C without variables. They are so essential to the language that it doesn’t even require an analogy here. We can declare and use them as wildly as we please, but it often makes sense to have a little bit more structure, and combine data that belongs together in a common collection. Arrays are a good start to bundle data of the same type, especially when there is no specific meaning of the array’s index other than the value’s position, but as soon as you want a more meaningful association of each value, arrays will become limiting. And they’re useless if you want to combine different data types together. Luckily, C provides us with proper alternatives out of the box.

This write-up will introduce structures and unions in C, how to declare and use them, and how unions can be (ab)used as an alternative approach for pointer and bitwise operations.

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QuickBASIC Lives On With QB64

February 22, 2018 by Tom Nardi 190 Comments

When I got my first computer, a second hand 386 running MS-DOS 6.22, I didn’t have an Internet connection. But I did have QuickBASIC installed and a stack of programming magazines the local library was throwing out, so I had plenty to keep myself busy. At the time, I thought QuickBASIC was more or less indistinguishable from magic. I could write simple code and compile it into an .exe, put it on a floppy, and give it to somebody else to run on their own machine. It seemed too good to be true, how could this technology possibly be improved upon?

Of course, that was many years ago, and things are very different now. The programming languages du jour are worlds more capable than the plodding BASIC variants of the 80’s and 90’s. But still, when I found a floppy full of programs I wrote decades ago, I couldn’t help but wonder about getting them running again. With something like DOSBox I reasoned I should be able to install the QuickBASIC IDE and run them like I was back on my trusty 386.

Unfortunately, that was not to be. Maybe I’m just not well versed enough in DOSBox, but I couldn’t get the IDE to actually run any of the source code I pulled off the floppy. This was disappointing, but then it occured to me that modern BASIC interpreters are probably being developed in some corner of the Internet, and perhaps I could find a way to run my nearly 30 year old code without having to rely on 30 year old software to do it. Continue reading “QuickBASIC Lives On With QB64” →

Stepping Up Your Python Printf Debugging Game

February 12, 2018 by Sven Gregori 4 Comments

Debuggers come in all shapes and sizes, offering a variety of options to track down your software problems and inspecting internal states at any given time. Yet some developers have a hard time breaking the habit of simply adding print statements into their code instead, performing manual work their tools could do for them. We say, to each their own — the best tools won’t be of much help if they are out of your comfort zone or work against your natural flow. Sometimes, a retrospective analysis using your custom-tailored debug output is just what you need to tackle an issue.

If the last part sounds familiar and your language of choice happens to be Python, [Alex Hall] created the Bird’s Eye Python debugger that records every expression inside a function and displays them interactively in a web browser. Every result, both partial and completed, and every value can then be inspected at any point inside each individual function call, turning this debugger into an educational tool along the way.

With a little bit of tweaking, the web interface can be made remote accessible, and for example, analyze code running on a Raspberry Pi. However, taking it further and using Bird’s Eye with MicroPython or CircuitPython would require more than just a little bit of tweaking, assuming there will be enough memory for it. Although it wouldn’t be first time that someone got creative and ran Python on a memory limited microcontroller.

Voice User Interface Design Practices

February 8, 2018 by Al Williams 20 Comments

Websites used to be uglier than they are now. Sure, you can still find a few disasters, but back in the early days of the Web you’d have found blinking banners, spinning text, music backgrounds, and bizarre navigation themes. Practices evolve, and now there’s much less variation between professionally-designed sites.

In a mirror of the world of hypertext, the same thing is going to happen with voice user interfaces (or VUIs). As products like Google Home and Amazon Echo get more users, developing VUIs will become a big deal. We are also starting to see hacker projects that use VUIs either by leveraging the big guys, using local code on a Raspberry Pi, or even using dedicated speech hardware. So what are the best practices for a VUI? [Frederik Goossens] shares his thoughts on the subject in a recent post.

Truthfully, a lot of the design process [Frederik] suggests mimics conventional user interface design in defining the use case and mapping out the flow. However, there are some unique issues surrounding usable voice interactions.

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Debugging An Arduino With An Arduino

February 7, 2018 by Tom Nardi 15 Comments

As every Hackaday reader knows, and tells us at every opportunity in the comments, adding an Arduino to your project instantly makes it twice as cool. But what if, in the course of adding an Arduino to your project, you run into a problem and need to debug the code? What if you could use a second Arduino to debug the first? That would bring your project up to two Arduinos, instantly making it four times as awesome as before you started! Who could say no to such exponential gains?

Not [Wayne Holder], that’s for sure. He writes in to let us know about a project he’s been working on for a while that allows you to debug the execution of code on an Arduino with a second Arduino. In fact, the target chip could even be another AVR series microcontroller such as a the ATTiny85. With his software you can single-step through the code, view and modify values in memory, set breakpoints, and even disassemble the code. Not everything is working fully yet, but what he has so far is very impressive.

The trick is exploiting a feature known as “debugWIRE” that’s included in many AVR microcontrollers. Unfortunately documentation on this feature is hard to come by, but with some work [Wayne] has managed to figure out how most of it works and create an Arduino Sketch that lets the user interact with the target chip using a simple menu system over the serial monitor, similar to the Bus Pirate.

[Wayne] goes into plenty of detail on his site and in the video included after the break, showing many of the functions he’s got working so far in his software against an ATTiny85. If you spend a lot of time working on AVR projects, this looks like something you might want to keep installed on an Arduino in your tool bag for the future.

Debugging microcontroller projects can be a huge time saver when your code starts running on real hardware, but often takes some hacking to get working.

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Easier End-User Setup For ESP32 Projects

January 23, 2018 by Tom Nardi 10 Comments

As hackers, we occasionally forget that not everyone is enamored with the same nerdy minutia that we are. Configuring hardware by changing some lines in the code and compiling a new firmware doesn’t sound like that big of a deal to those of us who’ve been around the block a few times, but might as well be ancient Sanskrit to the average person. As long as your projects are for personal use this isn’t really a concern, but what if you plan on distributing the code for a project or perhaps even selling finished products? Shipping it out with hard-coded variables simply isn’t an option.

Code for loading configuration file from SPIFFS

In a recent video, [Proto G] shows a clever way to use WiFiManager to make configuring your ESP32 project easier for end-users. Not only can you use the captive portal system to configure the ESP32’s WiFi against a nearby access point, but it can allow users to enter in configuration data which can be picked up in your code by using SPI Flash File System (SPIFSS).

With the setup demonstrated in the video below by [Proto G], you don’t need anything more exotic than a web browser to configure the device. The end user simply searches for the device’s WiFi network, connects to it, and is presented with an easy to understand dialog which has them select a WiFi network to configure against along with some fields to enter in custom variables. All this information is then stored to a file on the SPI flash. When the ESP32 reboots, it reads the configuration from the saved file and applies the requested settings.

This is very similar to how many consumer devices are now configured, and even the less technically-inclined recipients of such a device should be able to work through the setup with a bit of hand-holding. If you plan on handing one of your ESP32 projects to John Q. Public, this is the kind of configuration you should be aiming for.

We’ve covered using WiFiManager to make ESP32 projects easier to manage, but the addition of arbitrary variables to the captive portal opens up a lot of possibilities. Just the kind of thing you need when you start considering the leap to commercial product.

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Learn To Reverse Engineer X86_64 Binaries

January 6, 2018 by Sven Gregori 16 Comments

Opening up things, see how they work, and make them do what you want are just the basic needs of the average hacker. In some cases, a screwdriver and multimeter will do the job, but in other cases a binary blob of random software is all we have to work with. Trying to understand an unknown binary executable is an exciting way to discover a system’s internal functionality.

While the basic principles of software reverse engineering are universal across most platforms, the details can naturally vary for different architectures. In the case of the x86 architecture, [Leonora Tindall] felt that most tutorials on the subject focus mostly on 32-bit and not so much on the 64-bit specifics. Determined to change that, she ended up with an extensive introduction tutorial for reverse engineering x86_64 binaries starting at the very basics, then gradually moving forward using crackme examples. Covering simple string analysis and digging through disassembled binaries to circumvent fictional security, the tutorial later introduces the Radare2 framework.

All example source code is provided in the accompanying GitHub repository, although it is advised to avoid looking at them to keep it more interesting and challenging. And in case you are looking for more challenges later on, or generally prefer a closer connection to the hardware, these MSP430 based capture the flag online challenges might be worth to look at next.