Lock Up Your Raspberry Pi with Google Authenticator

Raspberry Pi boards (or any of the many similar boards) are handy to leave at odd places to talk to the network and collect data, control things, or do whatever other tasks you need a tiny fanless computer to do. Of course, any time you have a computer on a network, you are inviting hackers (and not our kind of hackers) to break in.

We recently looked at how to tunnel ssh using a reverse proxy via Pagekite so you can connect to a Pi even through firewalls and at dynamic IP addresses. How do you stop a bad guy from trying to log in repeatedly until they have access? This can work on any Linux machine, but for this tutorial I’ll use Raspberry Pi as the example device. In all cases, knowing how to set up adequate ssh security is paramount for anything you drop onto a network.

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Apple Aftermath: Senate Entertains A New Encryption Bill

If you recall, there was a recent standoff between Apple and the U. S. Government regarding unlocking an iPhone. Senators Richard Burr and Dianne Feinstein have a “discussion draft” of a bill that appears to require companies to allow the government to court order decryption.

Here at Hackaday, we aren’t lawyers, so maybe we aren’t the best source of legislative commentary. However, on the face of it, this seems a bit overreaching. The first part of the proposed bill is simple enough: any “covered entity” that receives a court order for information must provide it in intelligible form or provide the technical assistance necessary to get the information in intelligible form. The problem, of course, is what if you can’t? A covered entity, by the way, is anyone from a manufacturer, to a software developer, a communications service, or a provider of remote computing or storage.

There are dozens of services (backup comes to mind) where only you have the decryption keys and there is nothing reasonable the provider can do to get your data if you lose your keys. That’s actually a selling point for their service. You might not be anxious to backup your hard drive if you knew the vendor could browse your data when they wanted to do so.

The proposed bill has some other issues, too. One section states that nothing in the document is meant to require or prohibit a specific design or operating system. However, another clause requires that covered entities provide products and services that are capable of complying with the rule.

A broad reading of this is troubling. If this were law, entire systems that don’t allow the provider or vendor to decrypt your data could be illegal in the U. S. Whole classes of cybersecurity techniques could become illegal, too. For example, many cryptography systems use the property of forward secrecy by generating unrecorded session keys. For example, consider an SSH session. If someone learns your SSH key, they can listen in or interfere with your SSH sessions. However, they can’t take recordings of your previous sessions and decode them. The mechanism is a little different between SSHv1 (which you shouldn’t be using) and SSHv2. If you are interested in the gory details for SSHv2, have a look at section 9.3.7 of RFC 4251.

In all fairness, this isn’t a bill yet. It is a draft and given some of the definitions in section 4, perhaps they plan to expand it so that it makes more sense, or – at least – is more practical. If not, then it seems to be an indication that we need legislators that understand our increasingly technical world and have some understanding of how the new economy works. After all, we’ve seen this before, right? Many countries are all too happy to enact and enforce tight banking privacy laws to encourage deposits from people who want to hide their money. What makes you think that if the U. S. weakens the ability of domestic companies to make data private, that the business of concealing data won’t just move offshore, too?

If you were living under a rock and missed the whole Apple and FBI controversy, [Elliot] can catch you up. Or, you can see what [Brian] thought about Apple’s response to the FBI’s demand.

How The NSA Can Read Your Emails

Since [Snowden]’s release of thousands of classified documents in 2013, one question has tugged at the minds of security researchers: how, exactly, did the NSA apparently intercept VPN traffic, and decrypt SSH and HTTP, allowing the NSA to read millions of personal, private emails from persons around the globe? Every guess is invariably speculation, but a paper presented at the ACM Conference on Computer and Communications Security might shed some light on how the NSA appears to have broken some of the most widespread encryption used on the Internet (PDF).

The relevant encryption discussed in the paper is Diffie–Hellman key exchange (D-H), the encryption used for HTTPS, SSH, and VPN. D-H relies on a shared very large prime number. By performing many, many computations, an attacker could pre-compute a ‘crack’ on an individual prime number, then apply a relatively small computation to decrypt any individual message that uses that prime number. If all applications used a different prime number, this wouldn’t be a problem. This is the difference between cryptography theory and practice; 92% of the top 1 Million Alexa HTTPS domains use the same two prime numbers for D-H. An attacker could pre-compute a crack on those two prime numbers and consequently be able to read nearly all Internet traffic through those servers.

This sort of attack was discussed last spring by the usual security researchers, and in that time the researchers behind the paper have been hard at work. The earlier discussion focused on 512-bit D-H primes and the LogJam exploit. Since then, the researchers have focused on the possibility of cracking longer 768- and 1024-bit D-H primes. They conclude that someone with the resources of cracking a single 1024-bit prime would allow an attacker to decrypt 66% of IPsec VPNs and 26% of SSH servers.

There is a bright side to this revelation: the ability to pre-compute the ‘crack’ on these longer primes is a capability that can only be attained by nation states as it’s on a scale that has been compared to cracking Enigma during WWII. The hardware alone to accomplish this would cost millions of dollars, and although this computation could be done faster with dedicated ASICs or other specialized hardware, this too would require an enormous outlay of cash. The downside to this observation is, of course, the capability to decrypt the most prevalent encryption protocols may be in the hands of our governments. This includes the NSA, China, and anyone else with hundreds of millions of dollars to throw at a black project.

Raspberry Pi and Kindle Together Again

We’ve seen a lot of projects recently that take advantage of the Raspberry Pi 2’s augmented abilities. With the increased processor power and double the memory, it puts a lot more utility in the user’s hands. The latest project that takes advantage of this is the Pi-nk, which combines a Pi with a Kindle for some text-based awesomeness.

[Guillaume] has put together this detailed how-to which, unlike other builds we’ve seen in the past, uses wireless instead of USB for almost all of the connections, including the keyboard. Granted, this isn’t a new idea, but he’s presenting the way that he did it. To that end, all of the commands you’ll need to use are extremely well documented on the project page if you want to build your own. When everything is said and done, you’ll be SSHing into the Pi from the Kindle and using the popular “screen” program to get the Pi to use the Kindle as its display.

Additionally, [Guillaume] has posted some schematics for custom enclosures for the Pi-Kindle pair if you’re more ambitious. He points out that the e-ink display is great if the Pi is being run in text or command-line mode, and we’d have to agree. This is a very clean pairing of these devices and puts the strengths of both to great use!

Hackaday Links: February 8, 2015

[CNLohr] is famous for his extremely strange projects, including something that does something with Minecraft that even he can’t describe. Over the years, he’s built up a vast collection of projects that have been both incredible fails and successes. Here’s a video tour of all those projects.

For this week’s edition “Kickstarter is going insane”, you only need to look at the title of the campaign: Tesla Coils for North Korea.

Last week, a few slow scan TV signals were received from the International Space Station. Here’s the reddit thread.

The worst thing about using an Arduino in a semi-professional environment is the IDE. Here’s cuwire, a better IDE.

Wanna see something insane? How about an SSH library written in x64 assembly?

Radio Shack is in its death throes, and since you haven’t gone in the last few years, you might as well head out one last time and pick up some items on clearance. Here’s the list of store closings (PDF) and all 1,784 stores slated to be closed plotted on Google Maps.

War Gaming for Security Cred

Maybe you are an elite hax0r. But probably not. Maybe you feel like you should know more about how systems are compromised, and we’re all about that. You can’t keep the black hats out if you have no idea how they go about breaking in in the first place. That’s why war-gaming sites sprouted up in the first place. We find this one in particular to be delightfully engaging. OverTheWire’s Wargames teach you a little about security while the uninitiated also learn about simple concepts like SSH and, well… Linux!

On-the-job training is the best way to learn, and this is pretty close to it. Instead of providing an artificial avenue of learning the creators of OverTheWire have used the real thing to illustrate poor online security. You don’t “play the game” on an artificial web interface, you do it on legitimate platforms. The very first level (appropriately named Level 0) starts by figuring out how to connect to a system using Secure Shell (aka SSH). From there you’re prompted to use Linux command line tools to figure out where to go next.

Even veteran Linux/Security users should find this offering entertaining. The early stages are both quick and simple to navigate as an experienced admin while providing a welcoming learning platform for those who aren’t quite there yet. Work your way through a few different “servers” and before long your own knowledge will be tested. This isn’t a new platform, mentions of the site in Hackaday comments go back to 2010. But if you haven’t given it a try, Wargames is well worth adding to your weekend entertainment list.

[Thanks NightPhoenix]

A Better Way To Hack The Wink

If you’re looking for Home Automation appliances, you might want to check out the Wink Hub. It’s fifty bucks, and has six radios on board: WiFi, Bluetooth, Z-Wave, Zigbee, and 433MHz Lutron and Kidde. That’s an insane amount of connectivity in a very cheap package. It’s been pwnzor3d before, but dinnovative has a much better solution for getting root on this device.

Earlier methods of rooting the Wink involved passing commands via URLs – something that’s not exactly secure. The new method leverages what’s already installed on the Wink, specifically Dropbear, to generate public keys on the Wink hub and getting that key onto another computer securely. The complete exploit is just a few lines in a terminal, but once that’s done you’ll have a rooted Wink hub.

Even though the Wink hub has been rooted a few times before, we haven’t seen anything that leverages the capabilities of this hardware. There isn’t another device with a bunch of IoT radios on the market for $50, and we’re dying to see what people can come up with. If you’ve done something with your Wink, send it in on the tip line.