This Week In Security: Blast-RADIUS, Gitlab, And Plormbing

July 12, 2024 by Jonathan Bennett 6 Comments

The RADIUS authentication scheme, short for “Remote Authentication Dial-In User Service”, has been widely deployed for user authentication in all sorts of scenarios. It’s a bit odd, in that individual users authenticate to a “RADIUS Client”, sometimes called a Network Access Server (NAS). In response to an authentication request, a NAS packages up the authentication details, and sends it to a central RADIUS server for verification. The server then sends back a judgement on the authentication request, and if successful the user is authenticated to the NAS/client.

The scheme was updated to its current form in 1994, back when MD5 was considered a cryptographically good hash. It’s been demonstrated that MD5 has problems, most notably a chosen-prefix collision attack demonstrated in 2007. The basis of this collision attack is that given two arbitrary messages, it is possible to find a pair of values that, when appended to the end of those messages, result in matching md5 hashes for each combined message. It turns out this is directly applicable to RADIUS.
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DIY Spacer Increases FDM Flow Rate For Faster, Better Printing

July 12, 2024 by Dan Maloney 8 Comments

The host of problems to deal with when you’re feeling the need for FDM speed are many and varied, but high on the list is figuring out how to melt filament fast enough to accommodate high flow rates. Plus, the filament must be melted completely; a melty outside and a crunchy inside might be good for snacks, but not for 3D printing. Luckily, budget-minded hobbyists can build a drop-in booster to increase volumetric flow using only basic tools and materials.

[aamott]’s booster, which started life as a copper screw, is designed to replace the standard spacer in an extruder, with a bore that narrows as the filament gets closer to the nozzle to ensure that the core of the filament melts completely. Rather than a lathe, [aamott]’s main tool is a drill press, which he used to drill a 0.7 mm bore through the screw using a PCB drill bit. The hole was reamed out with a 10° CNC engraving bit, generating the required taper. After cutting off the head of the screw and cleaning up the faces, he cut radial slots into the body of the booster by threading the blade of a jeweler’s saw into the bore. The result was a bore wide enough to accept the filament on one end, narrowing to a (roughly) cross-shaped profile at the other.

Stacked up with a couple of knock-off Bondtech CHT nozzles, the effect of the booster was impressive — a 50% increase in flow rate. It’s not bad for a prototype made with simple tools, and it looks a little easier to build than [Stefan]’s take on the same idea.

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Making SD Cards More Nostalgic With More Cartridge-ness

July 12, 2024 by Maya Posch 11 Comments

As practical SD cards are, they lack much of what made floppy disks and cartridges so awesome: room for art and a list of contents, as well as the ability to not be lost in shaggy carpet or down a pet’s gullet. In a fit of righteous nostalgia, [Abe] decided that he’d turn SD cards into cartridges in the best way possible, and amazingly managed to not only finish the project after two years, but also make it look snazzy enough to have come straight out of the 1980s. The resulting cartridges come both with fixed (256 MB) and removable micro SD card storage, which are mounted on a PCB that passively connects to pogo pins in the custom, 3D printed reader.

Front of an SD-card-turned-cartridge with adn without decal. (Credit: Abe's Projects, YouTube) — Front of an SD-card-turned-cartridge with and without decal. (Credit: Abe’s Projects, YouTube)

The inspiration for this project kicked in while [Abe] was working on a floppy drive conversion project called the Floppy8, which crammed an MCU into an external floppy drive along with a rough version of these SD card-based cartridges that used the physical card’s edge connector to connect with a micro SD slot inside the converted floppy drive. The problem with this setup was that alignment was terrible, and micro SD cards would break, along with a range of other quality of life issues.

Next, the SD card was put into a slot on the carrier PCB that featured its own edge connector. This improved matters, but the overly complicated (moving) read head in the reader turned out to be very unreliable, in addition to FDM printed parts having general tolerance and durability issues. Eventually a simplified design which takes these limitations in mind was created that so far seems to work just fine.

Although SD cards in cartridges are not a new idea, using them purely as a data carrier is far less common. One could argue about the practicality of turning a fingernail-sized micro SD card into something much larger, but in terms of aesthetics and handleability it definitely gets an A+.

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