The saying “time and tide wait for no man” is usually used as a verbal kick in the pants, a reminder that sometimes an opportunity must be seized quickly before it passes by. But it can also be interpreted as a warning about the perpetual march of time and how it impacts the world around us. In that case, we would do well to add cellular technology to the list of proverbial things that wait for no one. Do you need 5G? No. Do you want it? Probably not. But it’s here, so be a good consumer and dump all your 4G hardware in the name of technical progress.
This line of logic may explain how the Verizon-branded Netgear AC791L 4G “Jetpack” hotspot you see here, despite being in perfect working order, found itself in the trash. The onset of 5G must have been particularly quick for the previous owner, since they didn’t even bother to wipe their configuration information from the device. In the name of journalistic integrity I won’t divulge the previous owner’s identity; but I will say that their endearing choice of WPA2 key, iluvphysics, makes for a nice fit with our publication.
A quick check of eBay shows these devices, and ones like it, are in ample supply. At the time of this writing, there were more than 1,500 auctions matching the search term “Verizon jetpack”, with most of them going for between $20 and $50 USD. We like cheap and easily obtainable gadgets that can be hacked, but is there anything inside one of these hotspots that we can actually use? Let’s find out.
You’ve got a machine hooked up to the Internet via a shiny new cellular modem, which you plan to administer remotely. You do a quick check on the external IP, and try and log in from another PC. Try as you might, SSH simply won’t connect. What gives?
The reality of the modern internet is that most clients no longer get their own unique IPv4 address. There simply aren’t enough to go around anymore. Instead, most telecommunications operators use Carrier Grade Network Address Translation which allows a single external address to be shared by many customers. This can get in the way of direct connection attempts from the outside world. Even if that’s not the case, most cellular operators tend to block inbound connections by default. However, there is a way around this quandary – using a VPN. Continue reading “Basics Of Remote Cellular Access: Connecting Via VPN”→
These days, we’re blessed with cellular data networks that span great swathes of the Earth. By and large, they’re used to watch TV shows and argue with strangers online. However, they’re also a great tool to use to interact with hardware in remote locations, particularly mobile ones where a wired connection is impractical.
In this series, we’re taking a look at tips and tricks for doing remote cellular admin the right way. First things first, you’ll need a data connection – so let’s look at choosing a modem.
Options Abound
When shopping around for cellular data modems, it can be difficult to wade through the variety of options out there and find something fit for purpose. Modems in this space are often marketed for very specific use cases; at the consumer level, many are designed to be a no-fuss home broadband solution, while in the commercial space, they’re aimed primarily to provide free WiFi for restaurants and cafes. For use in remote admin, the presence of certain features can be critical, so it pays to do your research before spending your hard earned money. We’ve laid out some of the common options below.
Consumer Models
The Sierra Aircard 320U is ancient now, with limited frequency bands available. Its flimsy flexible connector is also a drawback. However, its ease of configuration with Linux systems makes it a dream to use in remote access situations. Unlike many others, it acts as a Direct IP connection, not appearing as a separate router.
Many telecommunications providers around the world sell cheap USB dongles for connecting to the Internet, with these first becoming popular with the rise of 3G. They’re somewhat less common now in the 5G era, with the market shifting more towards WiFi-enabled devices that share internet among several users. These devices can often be had for under $50, and used on prepaid and contract data plans.
These devices are often the first stop for the budding enthusiast building a project that needs remote admin over the cellular network. However, they come with certain caveats that can make them less attractive for this use. Aimed at home users, they are often heavily locked down with firmware that provides minimal configuration options. They’re generally unable to be set up for port forwarding, even if you can convince your telco to give you a real IP instead of carrier-grade NAT. Worse, many appear to the host computer as a router themselves, adding another layer of NAT that can further complicate things. Perhaps most frustratingly, with these telco-delivered modems, the model number printed on the box is often not a great guide as to what you’re getting.
A perfect example is the Huawei E8327. This comes in a huge number of sub-models, with various versions of the modem operating in different routing modes, on different bands, and some even omitting major features like external antenna connectors. Often, it’s impossible to know exactly what features the device has until you open the box and strip the cover off, at which point you’re unable to return the device for your money back.
All is not lost, however. The use of VPNs can help get around NAT issues, and for the more adventurous, some models even have custom firmware available on the deeper, darker forums on the web. For the truly cash strapped, they’re a viable option for those willing to deal with the inevitable headaches. There are generally some modems that stand out over others in this space for configurability and ease of use. This writer has had great success with a now-aging Sierra Aircard 320U, while others have found luck with the Huawei E3372-607. As per earlier warnings though, you don’t want to accidentally end up with an E3372-608 – thar be dragons.
SIM cards are all around us, and with the continuing growth of the Internet of Things, spawning technologies like NB-IoT, this might as well be very literal soon. But what do we really know about them, their internal structure, and their communication protocols? And by extension, their security? To shine some light on these questions, open source and mobile device titan [LaForge] gave an introductory talk about SIM card technologies at the 36C3 in Leipzig, Germany.
Starting with a brief history lesson on the early days of cellular networks based on the German C-Netz, and the origin of the SIM card itself, [LaForge] goes through the main specification and technology parts of each following generation from 2G to 5G. Covering the physical basics, I/O interfaces, communication protocols, and the file system located on the SIM card, you’ll get the answer to “what on Earth is PIN2 for?” along the way.
Of course, a talk like this, on a CCC event, wouldn’t be complete without a deep and critical look at the security side as well. Considering how over-the-air updates on both software and — thanks to mostly running Java nowadays — feature side are more and more common, there certainly is something to look at.
Many moons ago, in the shadowy darkness of the 1990s, a young Lewin visited his elder cousin. An adept AMOS programmer, he had managed to get his Amiga 500 to control an RC car, with little more than a large pile of relays and guile. Everything worked well, but there was just one problem — once the car left the room, there was no way to see what was going on.
Why don’t you put a camera on it? Then you can drive it anywhere!
—Lewin
This would go on to inspire the TKIRV project approximately 20 years later. The goal of the project is to build a rover outfitted with a camera, which is controllable over cellular data networks from anywhere on Earth. For its upcoming major expedition, the vehicle is to receive solar panels to enable it to remain operable in distant lands for extended periods without having to return to base to recharge.
The project continues to inch towards this goal, but as the rover nears completion, the temptation to take it out for a spin grew ever greater. What initially began as an exciting jaunt actually netted plenty of useful knowledge for the rover’s further development.
When 3G was developed, long ago now, spoofing cell towers was expensive and difficult enough that the phone’s International Mobile Subscriber Identity (IMSI) was transmitted unencrypted. For 5G, a more secure version based on a asymmetric encryption and a challenge-reponse protocol that uses sequential numbers (SQNs) to prevent replay attacks. This hack against the AKA protocol sidesteps the IMSI, which remains encrypted and secure under 5G, and tracks you using the SQN.
The vulnerability exploits the AKA’s use of XOR to learn something about the SQN by repeating a challenge. Since the SQNs increment by one each time you use the phone, the authors can assume that if they see an SQN higher than a previous one by a reasonable number when you re-attach to their rogue cell tower, that it’s the same phone again. Since the SQNs are 48-bit numbers, their guess is very likely to be correct. What’s more, the difference in the SQN will reveal something about your phone usage while you’re away from the evil cell.
A sign of the times, the authors propose that this exploit could be used by repressive governments to track journalists, or by advertisers to better target ads. Which of these two dystopian nightmares is worse is left as comment fodder. Either way, it looks like 5G networks aren’t going to provide the location privacy that they promise.
Oh, boy. You know what’s happening next weekend?The Midwest RepRap Festival. The greatest 3D printing festival on the planet is going down next Friday afternoon until Sunday afternoon in beautiful Goshen, Indiana. Why should you go? Check this one out. To recap from last year, E3D released a new extruder, open source filaments will be a thing, true color filament printing in CMYKW is awesome, and we got the world’s first look at the infinite build volume printer. This year, The Part Daddy, a 20-foot-tall delta bot will be there once again. It’s awesome and you should come.
We launched the 2018 Hackaday Prize this week. Why should you care? Because we’re giving away $200,000 in prizes. There are five challenges: the Open Hardware Design Challenge, Robotics Module, Power Harvesting, Human-Computer Interface, and Musical Instrument Challenge. That last one is something I’m especially interested in for one very specific reason. This is a guitorgan.
Building a computer soon? Buy your SSD now. Someone fell asleep on the e-stop at a Samsung fab, and now 3.5% of global NAND production for March has been lost.
Need to put an Arduino in the cloud? Here’s a shield for that. It’s a shield for SIMCom’s SIM7000-series module, providing LTE for a microcontroller. Why would you ever need this? Because 2G is dead, for various values of ‘dead’. 3G is eventually going to go the same way.
A bridge collapsed in Florida this week. A pedestrian walkway at Florida International University collapsed this week, killing several. The engineering efforts are still underway to determine the cause of the accident, but some guy from Canukistan posted a pair of informative videos discussing I-beams and pre-tensioned concrete. It’s going to be months until the fault (and responsibility) will be determined, but until then we have the best footage yet of this collapse. It’s dash cam footage from a truck that rolled up to the red light just before the collapse. This is one that’s going to go down in engineering history along with the Hyatt Regency collapse.
