“Borrow” Payment Cards with NFC Proxy Hardware

Contactless payments are growing in popularity. Often the term will bring to mind the ability to pay by holding your phone over a reader, but the system can also use NFC tags embedded in credit cards, ID card, passports, and the like. NFC is a reasonably secure method of validating payments as it employs encryption and the functional distance between client and reader is in the tens of centimeters, and often much less. [Haoqi Shan] and the Unicorn team have reduced the security of the distance component by using a hardware proxy to relay NFC interactions over longer distances.

The talk, give on Sunday at DEF CON, outlined some incredibly simple hardware: an NFC antenna connected to a PN7462AU, an NRF24L01 wireless transceiver, and some power regulation. The exploit works by using a pair of these hardware modules. A master interfaces with the NFC reader, and a slave reads the card. The scenario goes something like this: a victim NFC card is placed near the slave hardware. The master hardware is placed over a payment kiosk as if making a normal payment. As the payment kiosk reader begins the process to read an NFC card, all of the communications between it and the actual card are forwarded over the 24L01 wireless connection.

The demo video during the talk showed a fast-food purchase made on the Apple Pay network while the card was still at a table out in the dining area (resting on the slave hardware module). The card used was a QuickPass contactless payment card from China UnionPay. According to a 2016 press release from the company, over two billion of these cards had been issued at the time. With that kind of adoption rate there is a huge incentive to find and patch any vulnerabilities in the system.

The hardware components in this build aren’t really anything special. We’ve seen these Nordic wireless modules used in numerous projects over they years, and the NXP chip is just NFC build around an ARM core. The leaps that tie this together are the speed-ups to make it work. NFC has tight timing and a delay between the master and slave would invalidate the handshake and subsequent interactions. The Unicorn team found some speedups by ensuring the chip was waking from suspend mode (150 µS) and not a deeper sleep. Furthermore, [Haoqi] mentioned they are only transmitting “I/S/R Block Data” and not the entirety of the interaction to save on time transmitting over the 24L01 wireless link. He didn’t expand on that so if you have details about what those blocks actually consist of please let us know in the comments below.

To the card reader, the emulated payment card is valid and the payment goes through. But one caveat to the system is that [Haoqi] was unable to alter the UID of the emulator — it doesn’t spoof the UID of the payment card being exploited. Current readers don’t check the UID and this could be one possible defense against this exploit. But to be honest, since you need close physical proximity of the master to the reader and the slave to the payment card simultaneously, we don’t see mayhem in the future. It’s more likely that we’ll see hacker cred when someone builds a long-range link that lets you leave your NFC cards at home and take one emulator with you for wireless door access or contactless payments in a single device. If you want to get working on this, check out the talk slides for program flow and some sourcecode hints.

Looking Forward To SHA2017

We’re at the start of August, which can only mean one thing. Europe’s hackers and makers are about to converge in a field somewhere for a long weekend of sitting around drinking beer and Club-Mate, eating unhealthy street food, being assaulted by some of the most underground chiptune electronic dance music on the planet, sharing the fruits of their labours with their peers, and gazing lovingly upon other people’s hacks. This year it’s the turn of the Netherlands, for over the first full weekend in August that country will host the SHA2017 outdoor hacker camp in a scouting camp on the polders. It promises to be quite an event, with just short of 4000 attendees spread over several fields, arenas, and social areas, and we’re going to be there. Tent and power lead with Schuko plug sorted, massive pile of stickers secured, DECT phone charged, emergency supplies of PG Tips packed.

There is so much to take in at these events that it can sometimes be difficult to catch everything. One can do the rounds as diligently as possible and still miss some of the cool stuff, so this is where you come in. Are you going to SHA? Are you bringing anything you consider cool to the event? Tell us about it in the comments, we’d love to hear about it as would we’re sure the rest of our readers.

Meanwhile, if you think you’ve missed the boat, don’t panic! At the time of writing, there are about 180 tickets still unsold, but they’ll be going fast! Head over to the SHA2017 tickets site to get yours.

(The stripey header, in case you were wondering, is SHA2017’s branding using as you might have guessed, the SHA algorithm to generate HTML colours. What you see are the colours for “Hackaday”.)

Michael Ossmann Pulls DSSS Out of Nowhere

[Michael Ossmann] spoke on Friday to a packed house in the wireless hacking village at DEF CON 25. There’s still a day and a half of talks remaining but it will be hard for anything to unseat his Reverse Engineering Direct Sequence Spread Spectrum (DSSS) talk as my favorite of the con.

DSSS is a technique used to transmit reliable data where low signal strength and high noise are likely. It’s used in GPS communications where the signal received from a satellite is often far too small for you to detect visually on a waterfall display. Yet we know that data is being received and decoded by every cell phone on the planet. It is also used for WiFi management packets, ZigBee, and found in proprietary systems especially any dealing with satellite communications.

[Michael] really pulled a rabbit out of a hat with his demos which detected the DSSS signal parameters in what appeared to be nothing but noise. You can see below the signal with and without noise; the latter is completely indiscernible as a signal at all to the eye, but can be detected using his techniques.

Detecting DSSS with Simple Math

[Michael] mentioned simple math tricks, and he wasn’t kidding. It’s easy to assume that someone as experienced in RF as he would have a different definition of ‘simple’ than we would. But truly, he’s using multiplication and subtraction to do an awful lot.

DSSS transmits binary values as a set called a chip. The chip for digital 1 might be 11100010010 with the digital 0 being the inverse of that. You can see this in the slide at the top of this article. Normal DSSS decoding compares the signal to expected values, using a correlation algorithm that multiplies the two and gives a score. If the score is high enough, 11 in this example, then a bit has been detected.

To reverse engineer this it is necessary to center on the correct frequency and then detect the chip encoding. GNU radio is the tool of choice for processing a DSSS capture from a SPOT Connect module designed to push simple messages to a satellite communication network. The first math trick is to multiply the signal by itself and then look at spectrum analysis to see if there is a noticeable spike indicating the center of the frequency. This can then be adjusted with an offset and smaller spikes on either side will be observed.

When visualized in a constellation view you begin to observe a center and two opposite clusters. The next math trick is to square the signal (multiply it by itself) and it will join those opposite clusters onto one side. What this accomplishes is a strong periodic component (the cycle from the center to the cluster and back again) which reveals the chip rate.

Detecting symbols within the chip is another math trick. Subtract each successive value in the signal from the last and you will mostly end up with zero (high signal minus high signal is zero, etc). But every time the signal spikes you’re looking at a transition point and the visualization begins to look like logic traced out on an oscilloscope. This technique can deal with small amounts of noise but becomes more robust with a bit of filtering.

This sort of exploration of the signal is both fun and interesting. But if you want to actually get some work done you need a tool. [Michael] built his own in the form of a python script that cobbles up a .cfile and spits out the frequency offset, chip rate, chip sequence length, and decoded chip sequence.

Running his sample file through with increasing levels of noise added, the script was rock solid on detecting the parameters of the signal. Interestingly, it is even measuring the 3 parts per million difference between the transmitter and receiver clocks in the detected chip rate value. What isn’t rock solid is the actual bit information, which begins to degrade as the noise is increased. But just establishing the parameters of the protocol being used is the biggest part of the battle and this is a dependable solution for doing that quickly and automatically.

You can give the script a try. It is part of [Michael’s] Clock Recovery repo. This talk was recorded and you should add it to your reminder list for after the con when talks begin to be published. To hold you over until then, we suggest you take a look at his RF Design workshop from the 2015 Hackaday Superconference.

Injecting Code Into Mouse Firmware Should Be Your Next Hack

Here’s a DEF CON talk that uses tools you likely have and it should be your next hacking adventure. In their Saturday morning talk [Mark Williams] and [Rob Stanely] walked through the process of adding their own custom code to a gaming mouse. The process is a crash course in altering a stock firmware binary while still retaining the original functionality.

The jumping off point for their work is the esports industry. The scope of esporting events has blown up in recent years. The International 2016 tournament drew 17,000 attendees with 5 million watching online. The prize pool of $20 million ($19 million of that crowdfunded through in-game purchases) is a big incentive to gain a competitive edge to win. Contestants are allowed to bring their own peripherals which begs the questions: can you alter a stock gaming mouse to do interesting things?

The steelseries Sensei mouse was selected for the hack because it has an overpowered mircocontroller: the STM32F103CB. With 128 KB of flash the researchers guessed there would be enough extra room for them to add code. STM32 chips are programmed over ST-Link, which is available very inexpensively through the ST Discovery boards. They chose the STM32F4DISCOVERY which runs around  $20.

Perhaps the biggest leap in this project is that the firmware wasn’t read-protected. Once the data, clock, and ground pads on the underside of the board were connected to the Discovery board the firmware was easy to dump and the real fun began.

They first looked through the binary for a large block of zero values signifying unused space in flash. The injected firmware is designed to enumerate as a USB keyboard, open Notepad, then type out, save, and execute a PowerShell script before throwing back to the stock firmware (ensuring the mouse would still function as a mouse). Basically, this builds a USB Rubber Ducky into stock mouse firmware.

There are a few useful skills that make taking on this project a worthwhile learning experience. To compile your custom code correctly you need to choose the correct offset address for where it will end up once pasted into the firmware binary. The vector table of the original code must be rewritten to jump to the injected code first, and it will need to jump back to the mouse execution once it has run. The program flow on the left shows this. Both of these jumps require the program counter and registers to be saved and restored. The ARM stack is subtractive and the address will need to be updated to work with the added code.

The talk ended with a live demo that worked like a charm. You can check out the code in the MDHomeBrew repo. In this case the PowerShell script adds keyboard shortcuts for DOOM cheats. But like we said before, the experience of getting under the hood with the firmware binary is where the value will be for most people. With this success under your belt you can take on more difficult challenges like [Sprite_TM’s] gaming keyboard hack where the firmware couldn’t easily be dumped and an update binary was quite obsfucated.

Building a DEF CON Badge in Two Weeks

DEF CON is starting right now, and this is the year of #badgelife. For the last few years, independent hardware wizards have been creating and selling their own unofficial badges at DEF CON, but this year it’s off the charts. We’ve already taken a look at Bender Badges, BSD Puffer Fish, and the worst idea for a conference badge ever, and this is only scratching the surface.

This is also a banner year for the Hackaday / Tindie / Supplyframe family at DEF CON. We’re on the lookout for hardware. We’re sponsoring the IoT village, [Jasmine] — the high priestess of Tindie — and I will be spending some time in the Hardware Hacking Village, praising our overlords and saying the phrase, ‘like Etsy, but for electronics’ far too much. We’ll be showing people how to solder, fixing badges, and generally being helpful to the vast unwashed masses.

Obviously, this means we need our own unofficial DEF CON badge. We realized this on July 10th. That gave us barely more than two weeks to come up with an idea for a badge, design one, order all the parts, wait on a PCB order, and finally kit all the badges before lugging them out to DEF CON. Is this even possible? Surprisingly, yes. It’s almost easy, and there are zero excuses for anyone not to develop their own hardware badge for next year’s con.

Continue reading “Building a DEF CON Badge in Two Weeks”

Superconference Interview: Samy Kamkar

Samy Kamkar has an incredible arsenal of self-taught skills that have grown into a remarkable career as a security researcher. He dropped out of high school to found a company based on Open Source Software and became infamous for releasing the Samy worm on the MySpace platform. But in our minds Samy has far outpaced that notoriety with the hardware-based security exploits he’s uncovered over the last decade. And he’s got a great gift for explaining these hacks — from his credit card magstripe spoofing experiments to hacking keyless entry systems and garage door opener remotes — in great depth during his talk at the 2016 Hackaday Superconference.

We pulled Samy aside after his talk to discuss how the security scene has grown up over the years and asked him to share his advice for people just coming up now. We’re happy to publish it for the first time today, it can be seen below.

Now it’s your turn. The Call for Proposals is now open for the 2017 Hackaday Superconference. You don’t need to be Samy Kamkar to qualify for a talk. You just need an interesting story of hardware engineering, creativity in technical design, an adventure with product design, or a sordid tale of your prototyping experiences. We hope everyone with a story will submit their proposal, but for those who don’t tickets are now available. The Hackaday Superconference will take place in Pasadena, California on November 11th and 12th.

Sunday: Breakfast at DEF CON

Nurse your hangover by having Breakfast at DEF CON with Hackaday this Sunday. You’re invited to our yearly ritual by marking the beginning of the end with coffee and pastries at 10:30 am.

Choosing an exact location in advance is always tricky (anyone who’s been to DEF CON understands). We’ll pick a place once we hit town later this week. For now, head over to the Breakfast at DEF CON event page and hit the “join the team” button on the bottom left so we can let you know when we’ve found the perfect location for the breakfast meetup.

Extra internet points go to those who bring some hardware to show off… and especially for anyone who is making this the end of their Saturday rather than the beginning of Sunday. [Brian] and [Mike] will be there, joined by our friends [Jasmine] and [Shulie] who are on the scene for Tindie, a sponsor of the IoT Village this year. See you on Sunday!