This Week In Security: Hide Yo SSH, Polyfill, And Packing It Up

July 5, 2024 by 9 Comments

The big news this week was that OpenSSH has an unauthorized Remote Code Execution exploit. Or more precisely, it had one that was fixed in 2006, that was unintentionally re-introduced in version 8.5p1 from 2021. The flaw is a signal handler race condition, where async-unsafe code gets called from within the SIGALARM handler. What does that mean?
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Toyota Heater Switches Learn New Tricks

July 5, 2024 by 32 Comments

The look, the feel, the sound — there are few things more satisfying in this world than a nice switch. If you’re putting together a device that you plan on using frequently, outfitting it with high-quality switches is one of those things that’s worth the extra cost and effort.

So we understand completely why [STR-Alorman] went to such great lengths to get the aftermarket seat heaters he purchased working with the gorgeous switches Toyota used in the 2006 4Runner. That might not sound like the kind of thing that would involve reverse engineering hardware, creating a custom PCB, or writing a bit of code to tie it all together. But of course, when working on even a halfway modern automobile, it seems nothing is ever easy.

The process started with opening up the original Toyota switches and figuring out how they work. The six-pin units have a lot going on internally, with a toggle, a rheostat, and multiple lights packed into each one. Toyota has some pretty good documentation, but it still took some practical testing to distill it down into something a bit more manageable. The resulting KiCad symbol for the switch helps explain what’s happening inside, and [STR-Alorman] has provided a chart that attributes each detent on the knob with the measured resistance.

But understanding how the switches worked was only half the battle. The aftermarket seat heaters were only designed to work with simple toggles, so [STR-Alorman] had to develop a controller that could interface with the Toyota switches and convince the heaters to produce the desired result. The custom PCB hosts a Teensy 3.2 that reads the information from both the left and right seat switches, and uses that to control a pair of beefy MOSFETs. An interesting note here is the use of very slow pulse-width modulation (PWM) used to flip the state of the MOSFET due to the thermal inertia of the heater modules.

We love the effort [STR-Alorman] put into documenting this project, going as far as providing the Toyota part numbers for the switches and the appropriate center-console panel with the appropriate openings to accept them. It’s an excellent resource if you happen to own a 4Runner from this era, and a fascinating read for the rest of us.

How To Turn Cheap Speakers Into Something A Little Better

July 5, 2024 by 25 Comments

[Adam Francis] bought some cheap speaker drivers from AliExpress. Are they any good? Difficult to tell without a set of enclosures for them, so he made a set of transmission line cabinets. The resulting video proves that a decent sounding set of speakers shouldn’t have to cost the earth, and is quite entertaining to watch.

The design he’s going for is a transmission line, in effect a folded half-wave resonant tube terminated at one end and open at the other, with the speaker close to half way along. There is a lot of nuance to perfecting a speaker cabinet, but this basic recipe doesn’t have to be optimum to give a good result.

So after having some MDF cut to shape and glueing it all together, he ends up with some semi decent speakers for not a lot of money. The video is entertaining, with plenty of Britishisms, but the underlying project is sound. We’d have a pair on our bench.

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Useless Robot Gets Cute, Has Personality

July 4, 2024 by 4 Comments

Useless robots (or useless machines) are devices that, when switched on, exist only to turn themselves back off. They are fun and fairly simple builds that are easy to personify, and really invite customization by their creators. Even so, [tobychui]’s Kawaii Useless Robot goes above and beyond in that regard. Not only will his creation dutifully turn itself off, but if the user persists in engaging it, Kawaii Useless Robot grows progressively (and adorably) upset which ultimately culminates in scooting about and trying to run away.

If anything, it gets cuter when upset.

This is actually a ground-up re-imagining of an original work [tobychui] saw from a Japanese maker twelve years ago. That original Kawaii Useless Robot did not have any design details, so [tobychui] decided to re-create his own.

Behind the laser-cut front panel is a dot matrix LED display made up of eight smaller units, and inside are a total of four motors, an ESP32 development board, and supporting electronics. A neat touch is the ability to allow connections over Wi-Fi for debugging or remote control. The project page has some nice photos of the interior that are worth checking out. It’s a very compact and efficient build!

Watch it in action in the video (embedded below) which also includes a tour of the internals and a thorough description of the functions.

Inspired to make your own useless machine? Don’t be afraid to re-invent the whole concept. For example, we loved the one that physically spins the switch and the clock that falls to the floor when it detects someone looking at it. That last one is a close relative of the clock that displays the wrong time if and only if someone is looking.

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Cavity Filters, The Black Art You Have A Chance Of Pursuing

July 4, 2024 by 12 Comments

A tuned circuit formed by a capacitor and an inductor is a familiar enough circuit, and it’s understood that it will resonate at a particular frequency. As that frequency increases, so the size of the capacitor and inductor decrease, and there comes a point at which they can become the characteristic capacitance and inductance of a transmission line. These tuned circuits can be placed in an enclosure, at which they can be designed for an extremely high Q factor, a measure of quality, and thus a very narrow resonant point. They are frequently used as filters for that reason, and [Fesz] is here with a video explaining some of their operation and configurations.

Some of the mathematics behind RF design can be enough to faze any engineer, but he manages to steer a path away from that rabbit hole and explain cavity filters in a way that’s very accessible. We learn how to look at tuned circuits as transmission lines, and the properties of the various different coupling methods. Above all it reveals that making tuned cavities is within reach.

They’re a little rare these days, but there was a time when almost every TV set contained a set of these cavities which were ready-made for experimentation.

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Shapeways Files For Bankruptcy

July 4, 2024 by 37 Comments

One of the earliest hobbyist-friendly on-demand 3D printing and fabrication shops, Shapeways, is filing for bankruptcy. As these financial arrangements always go, this may or may not mean the end of the service, but it’s a sure sign that their business wasn’t running as well as you’d hope.

One of the standout features of Shapeways was always that they made metal printing affordable to the home gamer. Whether it was something frivolous like a custom gear-shifter knob, or something all-too functional like a prototype rocket engine, it was neat to have the alternative workflow of iterative design at home and then shipping out for manufacturing.

We don’t want to speculate too much, but we’d be surprised if the rise of similar services in China wasn’t part of the reason for the bankruptcy. The market landscape just isn’t what it was way back in 2013. (Sadly, the video linked in this article isn’t around any more. If anyone can find a copy, post up in the comments?) So while Shapeways may or may not be gone, it’s not like we can’t get metal parts made anymore.

Still, we’re spilling a little for the OG.

Thanks [Aaron Eiche] for the breaking news tip!