Tiny Open Hardware Linux SBC Hides In Plain Sight

November 2, 2021 by Tom Nardi 20 Comments

There was a time, not quite so long ago, when a computer was a beige box that sat on your desk. Before that, computers were big enough to double as desks, and even farther back, they took up a whole room. Today? Well today it’s complicated. Single-board computers (SBCs) like the Raspberry Pi put a full desktop experience in the palm of your hand, for a price that would have been unfathomable before the smartphone revolution increased demand for high-performance ARM chips.

But compared to the tiny open hardware Linux SBC that lives inside the WiFiWart, even the Raspberry Pi looks massive. Developed by [Walker] as a penetration testing tool, the custom computer is housed in an enclosure designed to make it look like a traditional (if a bit large) USB phone charger. In fact, it doesn’t just look like a USB charger, it actually is one. The internal power supply is not only capable of converting AC into the various DC voltages required to run the miniature Linux box, but also features a USB port where you can plug in your phone to charge it.

For the infosec folks in the audience, the applications for the WiFiWart are obvious. Just plug this thing in somewhere inconspicuous, and you’ve got a foot in the door. The dual WiFi interfaces mean you can connect to a target network on one card and use the second to spin up a fake access point or exfiltrate data. Plus with a quad-core Cortex-A7 ARM processor running at 1.2 GHz and a healthy 1 GB of DDR3, you’ll have enough power to run many security tools locally.

But of course, nothing keeps you from using the WiFiWart for non-security purposes. That’s what has us particularly excited, as you can never have enough open hardware Linux boards. Especially ones this tiny. Removed from its wall charger disguise, the brains of the WiFiWart could be used for all kinds of projects. Plus, not only is the final design open source, but [Walker] made sure to only use free and open source tools to create it. Keeping his entire workflow open means it will be easier for the community to utilize and improve upon his initial design, which in the end, is the whole idea behind the open hardware movement and efforts such as the Hackaday Prize.

IC Shortage Keeps Linux Out Of Phone Charger, For Now

September 29, 2021 by Tom Nardi 21 Comments

We’ve been eagerly following the development of the WiFiWart for some time now, as a quad-core Cortex-A7 USB phone charger with dual WiFi interfaces that runs OpenWrt sounds exactly like the sort of thing we need in our lives. Unfortunately, we’ve just heard from [Walker] that progress on the project has been slowed down indefinitely by crippling chip shortages.

At this point, we’ve all heard how the chip shortage is impacting the big players out there. It makes sense that automakers are feeling the pressure, since they are buying literally millions of components at a clip. But stories like this are a reminder that even an individual’s hobby project can be sidelined by parts that are suddenly 40 times as expensive as they were when you first put them in your bill of materials.

In this particular case, [Walker] explains that a power management chip you could get on DigiKey for $1.20 USD a few months ago is now in such short supply that the best offer he’s found so far is $49.70 a pop from an electronics broker in Shenzhen. It sounds like he’s going to bite the bullet and buy the four of them (ouch) that he needs to build a working prototype, but obviously it’s a no go for production.

Luckily, it’s not all bad news. [Walker] has made some good progress on the power supply board, which will eventually join the diminutive computer inside the USB charger enclosure. Part of the trick is that the device is still supposed to be a functional USB charger, so in addition to 5 VDC for the output port, the power supply also needs to produce 1.1 V, 1.35 V, 2.5 V, 3.0 V, and 3.3 V for the computer. We’re glad to see he’s taking the high road with his mains circuitry, making sure to use UL listed components and maintaining proper isolation.

When we last checked in on the WiFiWart back in July, [Walker] had already managed to boot Linux on his over-sized prototype board. Now he’s got PCBs in hand that look far closer to the final size and shape necessary to tuck them into a phone charger. It’s a shame that the parts shortage is slowing down progress, but we’re confident we’ll at least get to see a one-off version of the WiFiWart powered up before the year is out.

WiFiWart Boots Linux, Moves To Next Design Phase

July 26, 2021 by Tom Nardi 12 Comments

Over the last few months we’ve been keeping an eye on WiFiWart, an ambitious project to develop a Linux single-board computer (SBC) small enough to fit inside a USB wall charger. Developer [Walker] says the goal is to create an easily concealable “drop box” for penetration testing, giving security researchers a valuable foothold inside a target network from which to preform reconnaissance or launch attacks. Of course, we don’t need to tell Hackaday readers that there’s plenty of other things you can do with such a tiny open hardware Linux SBC.

Today we’re happy to report that [Walker] has gotten the first version of the board booted into Linux, though as you might expect given a project of this complexity, there were a few bumps along the way. From the single missing resistor that caused U-Boot to throw up an error to the finer points of compiling the kernel for an embedded board, the latest blog post he’s written up about his progress provides fascinating insight into the little gotchas of bringing up a SBC from scratch.

Once the board was booted into Linux, [Walker] started testing out different aspects of the system. A memory benchmark confirmed the finicky DDR3 RAM was working as expected, and he was able to load the kernel modules for the dual RTL8188 interfaces and connect to a network. While the two WiFi modules are currently hanging off the board’s full-sized USB ports, they will eventually be integrated into the PCB.

Critically, this prototype board is also allowing [Walker] to get an idea of what the energy consumption of the final hardware might be. Even at full tilt, this larger board doesn’t go over 500 mA at 5 VDC; so if he designs the power supply with a maximum output of 1 A, he should have a nice safety margin. As mentioned in the previous post, the plan is currently to put the PSU on its own board, which will allow more effective use of the charger’s internal volume.

With the software and hardware now largely locked in, [Walker] says his attention will be turned towards getting everything small enough to fit into the final form factor. This will certainly be the most challenging aspect of the project, but with a growing community of hackers and engineers lending their expertise to the cause, we’re confident the WiFiWart will soon be a reality.

WiFiWart Linux Pentesting Device Gets First PCBs

July 3, 2021 by Tom Nardi 15 Comments

When we last checked in on the WiFiWart, an ambitious project to scratch-build a Linux powered penetration testing drop box small enough to be disguised as a standard phone charger, it was still in the early planning phases. In fact, the whole thing was little more than an idea. But we had a hunch that [Walker] was tenacious enough see the project through to reality, and now less than two months later, we’re happy to report that not only have the first prototype PCBs been assembled, but a community of like minded individuals is being built up around this exciting open source project.

Now before you get too excited, we should probably say that the prototypes didn’t actually work. Even worse, the precious Magic Smoke was released from the board’s Allwinner A33 ARM SoC when a pin only rated for 2.75 V was inadvertently fed 3.3 V. The culprit? Somehow [Walker] says he mistakenly ordered a 3.3 V regulator even though he had the appropriate 2.5 V model down in the Bill of Materials. A bummer to be sure, but that’s what prototypes are for.

Even though [Walker] wasn’t able to fire the board up, the fact that they even got produced shows just how much progress has been made in a relatively short amount of time. A lot of thought went into how the 1 GB DDR3 RAM would get connected to the A33, which includes a brief overview of how you do automatic trace length matching in KiCad. He’s also locked in component selections, such as the RTL8188CUS WiFi module, that were still being contemplated as of our last update.

Multiple boards make better use of vertical space.

Towards the end of the post, he even discusses the ultimate layout of the board, as the one he’s currently working on is just a functional prototype and would never actually fit inside of a phone charger. It sounds like the plan is to make use of the vertical real estate within the plastic enclosure of the charger, rather than trying to cram everything into a two dimensional design.

Want to get in on the fun, or just stay updated as [Walker] embarks on this epic journey? Perhaps you’d be interested in joining the recently formed Open Source Security Hardware Discord server he’s spun up. Whether you’ve got input on the design, or just want to hang out and watch the WiFiWart get developed, we’re sure he’d be happy to have you stop by.

The first post about this project got quite a response from Hackaday readers, and for good reason. While many in the hacking and making scene only have a passing interest in the security side of things, we all love our little little Linux boards. Especially ones that are being developed in the open.

Putting An Ultra-Tiny Linux Board In A Phone Charger…Eventually

May 6, 2021 by Tom Nardi 67 Comments

Among security professionals, a “drop box” is a device that can be covertly installed at a target location and phone home over the Internet, providing a back door into what might be an otherwise secure network. We’ve seen both commercial and DIY versions of this concept, and as you might expect, one of the main goals is to make the device look as inconspicuous as possible. Which is why [Walker] is hoping to build one into a standard USB wall charger.

This project is still in the early stages, but we like what we see so far. [Walker] aims to make this a 100% free and open source device, starting from the tools he’s using to produce the CAD files all the way up to the firmware the final hardware will run. With none of the currently available single-board computers (SBCs) meeting his list of requirements, the first step is to build a miniature Linux machine that’s got enough processing power to run useful security tools locally. Obviously such a board would be of great interest to the larger hacker and maker community.

The RTL8188CUS is likely to get integrated later on.

So far, [Walker] has decided on his primary components and is working on a larger development board before really going all-in on the miniaturization process. As of right now he’s planning on using the Allwinner A33 to power the board, a sub-$10 USD chipset most commonly seen in low-cost Android tablets.

The A33 boasts a quad-core Cortex-A7 clocked at 1.2 GHz, and offers USB, I2C, and SPI interfaces for expansion. It will be paired with 1 GB of DDR3 RAM, and an SD card to hold the operating system. Naturally a device like this will need WiFi, but until [Walker] can decide on which chip to use, the plan is to just use a USB wireless adapter. The Realtek RTL8188CUS is a strong contender, as the fact that it comes in both USB and module versions should make its eventual integration seamless.

Even if you’re not interested in the idea of hiding security appliances inside of everyday objects, this project is a fascinating glimpse into the process of creating your own custom Linux board. Whether you’re looking to put into a wall wart or a drone, it’s pretty incredible to think we’ve reached the point where an individual can spin up their own miniature SBC.