Day: February 16, 2024

Compact Cycloidal Drive Lives Inside This Custom Brushless Motor

February 16, 2024 by 7 Comments

With the popularity of robot dogs, many people have gotten on the bandwagon and tried building DIY versions. Most of them end up attaching a gearbox to an off-the-shelf brushless motor and call it a day. Not everyone goes that way, though, which is why this internal cycloidal drive actuator caught our eye.

Taking design cues from the MIT Mini Cheetah, [Aaed Musa] approached his actuator from the inside out, literally. His 3D printed cycloidal gearbox is designed to fit inside the stator of a BLDC motor. And not just any BLDC motor, but one built mostly from scratch using a hand-wound — and unwound, and wound again — stator along with a rotor that started as a printed part but was eventually machined from steel. Apart from its fixed ring, the cycloidal drive was mostly 3D printed, with everything fitting nicely inside the stator.

The video below shows the design and assembly process as well as testing of the finished drive. It seems to do really well with speed and positional accuracy, and it delivers a substantial amount of torque. Maybe a little too much, though; testing it with a heavy weight on the end of an arm got the stator coils hot enough to warp the printed parts within. But no matter; this was only a prototype after all. [Aaed] says improvements are in the works, including replacing all the plastic parts with metal ones.

Need a little background on cycloidal drives? They’re pretty cool.

Continue reading “Compact Cycloidal Drive Lives Inside This Custom Brushless Motor” →

This Week In Security: Filename Not Sanitized, MonikerLink, And Snap Attack!

February 16, 2024 by 6 Comments

Reading through a vulnerability report about ClamAV, I came across a phrase that filled me with dread: “The file name is not sanitized”. It’s a feature, VirusEvent, that can be enabled in the ClamnAV config. And that configuration includes a string formatting function, where the string includes %v and %s, which gets replaced with a detected virus name and the file name from the email. And now you see the problem, I hope: The filename is attacker supplied input.

Where this really gets out of hand is what ClamAV does with this string. execle("/bin/sh", "sh", "-c", buffer_cmd, NULL, env). So let’s talk defensive program design for a minute. When it comes to running a secondary command, there are two general options, system() and the exec*() family of system calls. system() is very simple to use. It pauses execution of the main process and asks the operating system to run a string, just as if the user had typed that command into the shell. While this is very convenient to use, there is a security problem if any of that command string is user-supplied. All it takes is a semicolon or ampersand to break assumptions and inject a command.

To the rescue comes exec(). It’s a bit more complicated to use, requiring the programmer to manually call fork() and wait(). But it’s not running the command via the shell. exec() executes a program directly, totally eliminating the potential for command injection! Except… oops.

Yeah, exec() and related calls don’t offer any security protections when you use them to execute /bin/sh. I suspect the code was written this way to allow running a script without specifying /bin/sh in the config. The official fix was to disable the filename format character, and instead supply it as an environment variable. That certainly works, and that fix is available in 1.0.5, 1.2.2, and 1.3.0.

The real danger here is that we have another case where some hardware appliance manufacturer has used ClamAV for email filtering, and uses this configuration by default. That’s how we get orders from CISA to unplug your hardware, because it’s already compromised. Continue reading “This Week In Security: Filename Not Sanitized, MonikerLink, And Snap Attack!” →

The Latest Windows 11 Release Might Not Work On Your Oldest Machines

February 16, 2024 by 76 Comments

Everybody knows you can’t install Windows XP on a 386, or Windows 95 on an original IBM PC. But for Windows 11, the goalposts seem to be changing with newer releases of the existing OS. As covered by The Register, it appears the latest Windows 11 24H2 update might be incompatible with older machines.

It’s all down to the POPCNT CPU instruction. As shared on Twitter by [TheBobPony], the instruction appears in a number of Windows 11 system files, including kernel and USB XHCI drivers. Thus, it appears that any CPU not able to run this instruction will not be able to boot Windows 11. POPCNT was first included in AMD’s Barcelona architecture in 2007, and Intel’s Core processors in 2008. It’s an instruction for counting set bits in a word.

Ultimately, the effect is that computers with older CPUs will no longer be able to run the latest version of Windows 11. It could be as simple as Microsoft engineers enabling more modern CPU instructions at compilation time. However, given affected hardware is more than 15 years old, it’s perhaps likely that Microsoft is perfectly willing to cut these machines off from using the latest versions of its main operating system. We’ve talked about this phenomenon before, too.

In any case, keep a close eye on Windows update if you’re running super-old hardware. Let us know if you’ll be affected in the comments.

Thanks to [Stephen Walters] for the tip!

All-Sky Camera Checks For Aurora

February 16, 2024 by 4 Comments

The aurora borealis (and its southern equivalent, the aurora australis) is a fleeting and somewhat rare phenomenon that produces vivid curtains of color in the sky at extreme latitudes. It’s a common tourist activity to travel to areas where the aurora is more prevalent in order to catch a glimpse of it. The best opportunities are in the winter though, and since most people don’t want to spend hours outside on a cold night night in high latitudes, an all-sky camera like this one from [Frank] can help notify its users when an aurora is happening.

Because of the extreme temperatures involved, this is a little more involved than simply pointing a camera at the sky and hoping for the best. The enclosure and all electronics need to be able to withstand -50°C and operate at at least -30. For the enclosure, [Frank] is going with PVC tubing with a clear dome glued into a top fits to the end of the pipe, providing a water-resistant enclosure. A Raspberry Pi with a wide-angle lens camera sits on a 3D printed carriage so it can easily slide inside. The electronics use power-over-ethernet (PoE) rather than a battery due to the temperature extremes, which conveniently provides networking capabilities for viewing the images.

This is only part one of this build — in part two [Frank] is planning to build a system which can use this camera assembly to detect the aurora automatically and send out notifications when it sees it. Watching the night sky from the comfort of a warm house or sauna isn’t the only reason for putting an all-sky camera to use, either. They can also be used to observe meteors as they fall and then triangulate the position of the meteorites on the ground.