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Car Whisperer
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SUMMARY
The carwhisperer project intends to educates manufacturers of carkits and
other Bluetooth appliances to the possibility of a security threat caused
by the use of standard passkeys.
DETAILS
A Bluetooth passkey is used within the pairing process that takes place,
when two Bluetooth enabled devices connect for the first time. Besides
other public data, the passkey is a secret parameter used in the process
that generates and exchanges the so-called link key. In Bluetooth
communication scenarios the link key is used for authentication and
encryption of the information that is exchanged between the counterparts
of the communication.
The cw_scanner script repeatedly performs a device inquiry for visible
Bluetooth devices of which the class matches the one of Bluetooth Headsets
and Hands-Free Units. Once a visible Bluetooth device is found and it has
the appropriate device class is found, the cw_scanner script executes the
carwhisperer binary that connects to the found device (on RFCOMM channel
1) and opens a control connection and connects the SCO links.
The carwhiperer binary connects to the device found by the cw_scanner. The
passkey that is required for the initial connection to the device is
provided by the cw_pin.pl script that replaces the official Bluez PIN
helper (graphical application that usually prompts for the passkey). The
cw_pin.pl script provides the passkey depending on the Bluetooth address
that requests it. Depending on the first three bytes of the address, which
references the manufacturer, different passkeys are returned by the
cw_pin.sh script. In quite a few cases the preset standard passkey on
headsets and handsfree units is '0000' or '1234'.
Once the connection has been successfully established, the carwhisperer
binary starts sending audio to, and recording audio from the headset. This
allows attackers to inject audio data into the car. This could be fake
traffic announcements or nice words. Attackers are also able to eavesdrop
conversations among people sitting in the car.
Ideally, the carwhisperer is used with a toooned dongle and a directional
antenna that enhances the range of a Bluetooth radio quite a bit. (see
Long-Distance-Snarf experiment)
Recommendations:
In order to avoid getting attacked by carwhisperer, manufacturers should
not use standard passkeys in their Bluetooth appliances. Moreover, there
should be some kind of direct interaction with the device that allows a
device to connect. Another recommendation would be to switch the handsfree
unit to invisible mode, when no authorized device connects to it within a
certain time.
Not all Bluetooth carkits are subject to this threat. There is quite a few
Bluetooth carkits that use random passkeys that are generated for every
individual device during the production process. Carkits that are
integrated with a full infotainment system could use (and sometimes
already do use) the infotainment system's UI for acquiring a passkey from
the user.
Proof of Concept:
A proof of concept can be found at:
<http://trifinite.org/Downloads/carwhisperer-0.1.tar.gz>
http://trifinite.org/Downloads/carwhisperer-0.1.tar.gz
ADDITIONAL INFORMATION
The information has been provided by <mailto:juha-matti.laurio@netti.fi>
Juha-Matti Laurio .
The review was written by <mailto:martin@trifinite.org> Martin Herfurt.
The original article can be found at:
<http://trifinite.org/trifinite_stuff_carwhisperer.html>
http://trifinite.org/trifinite_stuff_carwhisperer.html
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