The TP-Link TL-WR841N isn’t a particularly impressive piece of hardware, but since it works decently well and sells for under $20 USD, it’s one of the most popular consumer routers on Amazon. Now, thanks to [TrendyTofu] of the Zero Day Initiative, we now have a concise step-by-step guide on how to hack your way into the newer versions of the hardware and take full control over this bargain WiFi device. This work was initially done to help test out reported vulnerabilities in the router’s firmware, but we’re sure the readers of Hackaday can come up with all sorts of potential uses for this information.
The story starts, as so many before it have, with a serial port. Finding the UART pads on the PCB and wiring up a level shifter was no problem, but [TrendyTofu] found it was only working one-way. Some troubleshooting and an oscilloscope later, the culprit was found to be a 1kΩ pull down resistor connected to the RX line that was keeping the voltage from peaking high enough to be recognized.
Once two-way communication was established, proper poking around inside the router’s Linux operating system could begin. It wasn’t a huge surprise to find the kernel was ancient (version 2.6.36, from 2010) and that the system utilities had been stripped to the absolute bare minimum to save space. Replacing the firmware entirely would of course be ideal, but unfortunately OpenWRT has dropped support for the newer hardware revisions of the TL-WR841N.
To teach this barebones build of Linux some new tricks, [TrendyTofu] used the mount command to find a partition on the system that actually had write-access, and used that to stash a pre-compiled build of BusyBox for MIPS. With a more complete set of tools, the real fun could begin: using GDB to debug TP-Link’s binaries and look for chinks in the armor. But feel free to insert your own brand of mayhem here.
Large machine tools are often built to last a very long time, so it is not uncommon to find a lathe made in the 19th century still providing faithful service. The fundamental job of a lathe has not changed significantly in the intervening years, even though a modern lathe will have more features than its hundred-year-old equivalent.
This is not the case for CNC machine tools. When computer numerical control was wedded with old iron machine tools, the control hardware was doomed to quickly become antique or vintage. From the user interfaces to the control circuitry, in the world of electronics new features quickly become obsolete. [Evan] has a ShopBot CNC wood router from the mid 1990s that he describes as an antique, and his tale of its restoration is both a fascinating look at the changes in small-scale CNC control over two decades as well as something of a primer for anyone considering a similar upgrade.
The controller is a pair of beige-box PC cases that scream “I love the 90’s!”. One contains a socket-7 PC running Windows 95, and the other houses the ShopBot controller; an 80c32 dev board with ShopBot firmware, coupled to a set of motor controller boards, which unlike today’s controllers expect raw quadrature inputs. His aim was to replace the vintage hardware with a modern alternative. An Arduino Mega running grbl to talks to the ShopBot controllers by way of a small piece of electronics to condition quadrature data from the step and direction lines it provided. The result may not be as good as a router from 2019, but it did save this aging tool from retirement.
Whether it’s wood, metal, plastic, or otherwise, when it comes to obtaining materials for your builds, you have two choices: buy new stock, or scrounge what you can. Fresh virgin materials are often easier to work with, but it’s satisfying to get useful stock from unexpected sources.
This CNC router for PVC pipe is a great example of harvesting materials from an unusual source. [Christophe Machet] undertook his “Pipeline Project” specifically to explore what can be made from large-diameter PVC pipe, of the type commonly used for sewers and other drains. It’s basically a standard – albeit large-format – three-axis CNC router with one axis wrapped into a cylinder. The pipe is slipped around a sacrificial mandrel and loaded into the machine, where it rotates under what looks like a piece of truss from an antenna tower. The spindle seems a bit small, but it obviously gets the job done; luckily the truss has the strength and stiffness to carry a much bigger spindle if that becomes necessary in the future.
The video below shows the machine carving up parts for some lovely chairs. [Christophe] tells us that some manual post-forming with a heat gun is required for features like the arms of the chairs, but we could see automating that step too. We like the look of the pieces that come off this machine, and how [Christophe] saw a way to adapt one axis for cylindrical work. He submitted this project for the 2019 Hackaday Prize; have you submitted your entry yet?
We’ve seen plenty of plywood 3D printers before; after all, many early hobbyist machines were made from laser-cut plywood. But this plywood 3D-printer isn’t made from plywood – it prints plywood. Well, sort of.
Yes, we know – that’s not plywood the printer is using, but rather particleboard, the same material that fills the flatpack warehouse of every IKEA store. And calling it a printer is a bit of a stretch, too. This creation, by [Shane Whigton] and his Formlabs Hackathon team, is more of a hybrid additive-subtractive CNC machine. A gantry-mounted router carves each layer of the print from a fresh square of material – which could just as easily be plywood as particleboard. Once a layer is cut, the gantry applies glue to it, puts a fresh sheet of material on top, and clamps it down tight. The router then carves the next layer, and so on up the stack. The layer height is limited to the thickness of the material – a nominal 3/4″ (19 mm) in this case – and there’s a remarkable amount of waste, but that’s not really the point. Check out the printer in action and the resulting giant Benchy in the video below.
Do you know what your router is doing? We have two stories of the embedded devices misbehaving. First, Linksys “Smart” routers keep track of every device that connects to its network. Right, so does every other router. These routers, however, also helpfully expose that stored data over JNAP/HNAP.
Some background is needed here. First, HNAP is the Home Network Administration Protocol, designed to manage routers and network devices. Originally designed by Pure Networks, HNAP is a SOAP based protocol, and has been part of securityproblems in the past. You may also see the term JNAP. It seems that JNAP is the JSON Network Administration Protocol, identical to HNAP except for using JSON instead of SOAP.
The odd part is that this is an old problem. CVE-2014-8244 was disclosed and fixed in 2014. According to the writeup at Badpackets.net, the problem was re-discovered as a result of observing active network attacks targeting JNAP. When Linksys was informed of the rediscovered problem, they responded that the problem was fixed in 2014, and devices with updated firmware and default settings are not accessible from the public internet. The presence of over 20,000 devices leaking data casts doubt on their response. Continue reading “This Week In Security: Zombieload, And Is Your Router Leaking?”→
Before Wolfram Alpha, before the Internet, before even PCs, calculations more complex than what could be accomplished with a “four banger” required some kind of programmable calculator. There were many to choose from, if you had the means, and as time passed they became more and more sophisticated. Some even added offline storage so your painstakingly written and tediously entered programs didn’t evaporate when the calculator was turned off.
One such programmable calculator, a Casio PRO fx-1 with magnetic card storage, came across [amen]’s bench recently. Sadly, it didn’t come with any cards, so [amen] reverse engineered the card reader and brought the machine back to its 1970s glory. The oddball mag cards for it are no longer available, so [amen] had to make do with. He found some blank cards of approximately the right size for cheap, but somehow had to replicate the band of vertical stripes adjacent to the magnetic strip on the card. Reasoning that they provide an optical synchronization signal, he decided to use a CNC router to cut a series of fine-pitched slots in the plastic card. It took a little effort to get working, including tapping the optical sensor and reading the signal on an oscilloscope, but as the video below shows, the hacked cards work fine with the vintage calculator.
If you’re looking at CNC machines, or machine tools in general, heavier is better. That old drill press or mill made of a few hundred pounds of cast iron isn’t just better because it’s stood the test of time for a hundred years — greater mass equals less vibration. Thanks to modern epoxy resins, we now have a replacement for tons and tons of iron. Epoxy granite, or chips of granite bound together with epoxy resin, is a viable and very good base for CNC machines, mills, and other tools that are served well with a ton of mass. [Joerg Beigang] is building his own CNC router, and he’s building the base out of epoxy granite. Here’s how he’s doing it.
Before you pour epoxy into a mold, you’ll need to figure out how you’re going to attach your ways, linear rails, and ball screws. [Joreg] is bolting these parts to pieces of aluminum he cut on his home made panel saw before carefully drilling and tapping them to accept the linear rails. These aluminum plates were then mounted to the bottom panel of the mold, in this case melamine-coated plywood.
As you would expect, the most intricate part of this build isn’t globbing up a mold with epoxy resin. No, the real trick here is making sure the rails of the CNC are aligned perfectly before the epoxy goes in. This was done by bolting the linear rails to the mold box and checking everything with a dial indicator. Once that was done it was time to pour.
The bed itself is made of 18kg of epoxy granite, with the entire pour done in four batches. The best way to settle a big pour of epoxy granite is through vibration, just like concrete, but it looks as though [Joreg] is getting some good results by tamping it down with a few sticks. You can check out the first part of this build series below.