Researchers from the École Polytechnique Federale de Lausanne vulnerability in the pairing methods of devices that comply with the Bluetooth Classic standard (Bluetooth BR/EDR). The vulnerability has been assigned a code name (). The problem allows an attacker to organize the connection of his fake device instead of a previously connected user device, and successfully complete the authentication procedure without knowing the link key generated during the initial pairing of devices and allowing one to avoid repeating the manual confirmation procedure at each connection.
The essence of the method is that when connecting to devices that support Secure Connections mode, the attacker announces the absence of this mode and falls back to using an outdated authentication method (“legacy” mode). In the “legacy” mode, the attacker initiates a master-slave role change, and, presenting his device as a “master,” takes upon himself to confirm the authentication procedure. The attacker then sends a notification that the authentication was successful, even without possessing the channel key, and the device becomes authenticated to the other party.
After this, the attacker can achieve the use of an encryption key that is too short, containing only 1 byte of entropy, and use an attack previously developed by the same researchers in order to organize an encrypted Bluetooth connection under the guise of a legitimate device (if the device is protected from KNOB attacks and the key size could not be reduced, then the attacker will not be able to establish an encrypted communication channel, but will continue to remain authenticated to the host).
To successfully exploit the vulnerability, it is necessary that the attacker's device be within reach of the vulnerable Bluetooth device and the attacker must determine the address of the remote device to which the connection was previously made. Researchers a prototype of the toolkit with the implementation of the proposed attack method and how to use a laptop with Linux and a Bluetooth card fake the connection of a previously paired Pixel 2 smartphone.
The problem is caused by a specification flaw and manifests itself in various Bluetooth stacks and Bluetooth chip firmwares, including Intel, Broadcom, Cypress Semiconductor, Qualcomm, Apple and Samsung used in smartphones, laptops, single board PCs and peripherals from various manufacturers. Researchers 30 devices (Apple iPhone/iPad/MacBook, Samsung Galaxy, LG, Motorola, Philips, Google Pixel/Nexus, Nokia, Lenovo ThinkPad, HP ProBook, Raspberry Pi 3B+, etc.) that use 28 different chips, and notified manufacturers about the vulnerability in December last year. Which of the manufacturers has already released firmware updates with the fix is not yet detailed.
The Bluetooth SIG, which is responsible for developing Bluetooth standards, about the development of an update to the Bluetooth Core specification. The new edition clearly defines cases in which it is permissible to change the master-slave roles, introduced a mandatory requirement for mutual authentication when rolling back to “legacy” mode, and recommended checking the type of encryption to prevent a decrease in the level of connection security.
Source: opennet.ru