An anonymous reader quotes a report from Ars Technica:
When you use your phone to unlock a Tesla, the device and the car use Bluetooth signals to measure their proximity to each other. Move close to the car with the phone in hand, and the door automatically unlocks. Move away, and it locks. This proximity authentication works on the assumption that the key stored on the phone can only be transmitted when the locked device is within Bluetooth range. Now, a researcher has devised a hack that allows him to unlock millions of Teslas -- and countless other devices -- even when the authenticating phone or key fob is hundreds of yards or miles away. The hack, which exploits weaknesses in the Bluetooth Low Energy standard adhered to by thousands of device makers, can be used to unlock doors, open and operate vehicles, and gain unauthorized access to a host of laptops and other security-sensitive devices.
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[The] attack uses custom software and about $100 worth of equipment. [Sultan Qasim Khan, a principal security consultant and researcher at security firm NCC Group] has confirmed it works against the Tesla Model 3 and Model Y and Kevo smart locks marketed under the Kwikset and Weiser brand names. But he says virtually any BLE device that authenticates solely on proximity -- as opposed to also requiring user interaction, geolocation querying, or something else -- is vulnerable. "The problem is that BLE-based proximity authentication is used in places where it was never safe to do so," he explained. "BLE is a standard for devices to share data; it was never meant to be a standard for proximity authentication. However, various companies have adopted it to implement proximity authentication."
Because the threat isn't caused by a traditional bug or error in either the Bluetooth specification or an implementation of the standard, there's no CVE designation used to track vulnerabilities. Khan added: "In general, any product relying on BLE proximity authentication is vulnerable if it does not require user interaction on the phone or key fob to approve the unlock and does not implement secure ranging with time-of-flight measurement or comparison of the phone/key fob's GPS or cellular location relative to the location of the device being unlocked. GPS or cellular location comparison may also be insufficient to prevent short distance relay attacks (such as breaking into a home's front door or stealing a car from the driveway, when the owner's phone or key fob is inside the house)."
There's a few countermeasures one can take to mitigate this attack. "One mechanism is to check the location of the authenticating device to ensure that it is, in fact, physically close to the locked car or other device," reports Ars. "Another countermeasure is to require the user to provide some form of input to the authenticating device before it's trusted." The phone's accelerometer could also be used to measure its movements.
The advisories published by NCC Group can be found here, here, and here.
