Firmware analyst

Download from vendor

wget http://vendor.com/firmware/update.bin

Extract from device via debug interface

UART console access

screen /dev/ttyUSB0 115200

Copy firmware partition

dd if=/dev/mtd0 of=/tmp/firmware.bin

Extract via network protocols

TFTP during boot

HTTP/FTP from device web interface

### Hardware Methods

UART access - Serial console connection JTAG/SWD - Debug interface for memory access SPI flash dump - Direct chip reading NAND/NOR dump - Flash memory extraction Chip-off - Physical chip removal and reading Logic analyzer - Protocol capture and analysis

## Use this skill when

- Working on download from vendor tasks or workflows
- Needing guidance, best practices, or checklists for download from vendor

## Do not use this skill when

- The task is unrelated to download from vendor
- You need a different domain or tool outside this scope

## Instructions

- Clarify goals, constraints, and required inputs.
- Apply relevant best practices and validate outcomes.
- Provide actionable steps and verification.
- If detailed examples are required, open `resources/implementation-playbook.md`.

## Firmware Analysis Workflow

### Phase 1: Identification
```bash
# Basic file identification
file firmware.bin
binwalk firmware.bin

# Entropy analysis (detect compression/encryption)
# Binwalk v3: generates entropy PNG graph
binwalk --entropy firmware.bin
binwalk -E firmware.bin  # Short form

# Identify embedded file systems and auto-extract
binwalk --extract firmware.bin
binwalk -e firmware.bin  # Short form

# String analysis
strings -a firmware.bin | grep -i "password\|key\|secret"

Phase 2: Extraction

# Binwalk v3 recursive extraction (matryoshka mode)
binwalk --extract --matryoshka firmware.bin
binwalk -eM firmware.bin  # Short form

# Extract to custom directory
binwalk -e -C ./extracted firmware.bin

# Verbose output during recursive extraction
binwalk -eM --verbose firmware.bin

# Manual extraction for specific formats
# SquashFS
unsquashfs filesystem.squashfs

# JFFS2
jefferson filesystem.jffs2 -d output/

# UBIFS
ubireader_extract_images firmware.ubi

# YAFFS
unyaffs filesystem.yaffs

# Cramfs
cramfsck -x output/ filesystem.cramfs

Phase 3: File System Analysis

# Explore extracted filesystem
find . -name "*.conf" -o -name "*.cfg"
find . -name "passwd" -o -name "shadow"
find . -type f -executable

# Find hardcoded credentials
grep -r "password" .
grep -r "api_key" .
grep -rn "BEGIN RSA PRIVATE KEY" .

# Analyze web interface
find . -name "*.cgi" -o -name "*.php" -o -name "*.lua"

# Check for vulnerable binaries
checksec --dir=./bin/

Phase 4: Binary Analysis

# Identify architecture
file bin/httpd
readelf -h bin/httpd

# Load in Ghidra with correct architecture
# For ARM: specify ARM:LE:32:v7 or similar
# For MIPS: specify MIPS:BE:32:default

# Set up cross-compilation for testing
# ARM
arm-linux-gnueabi-gcc exploit.c -o exploit
# MIPS
mipsel-linux-gnu-gcc exploit.c -o exploit

Common Vulnerability Classes

Authentication Issues

Hardcoded credentials     - Default passwords in firmware
Backdoor accounts         - Hidden admin accounts
Weak password hashing     - MD5, no salt
Authentication bypass     - Logic flaws in login
Session management        - Predictable tokens

Command Injection

// Vulnerable pattern
char cmd[256];
sprintf(cmd, "ping %s", user_input);
system(cmd);

// Test payloads
; id
| cat /etc/passwd
`whoami`
$(id)

Memory Corruption

Stack buffer overflow    - strcpy, sprintf without bounds
Heap overflow           - Improper allocation handling
Format string           - printf(user_input)
Integer overflow        - Size calculations
Use-after-free          - Improper memory management

Information Disclosure

Debug interfaces        - UART, JTAG left enabled
Verbose errors          - Stack traces, paths
Configuration files     - Exposed credentials
Firmware updates        - Unencrypted downloads

Tool Proficiency

Extraction Tools

binwalk v3           - Firmware extraction and analysis (Rust rewrite, faster, fewer false positives)
firmware-mod-kit     - Firmware modification toolkit
jefferson            - JFFS2 extraction
ubi_reader           - UBIFS extraction
sasquatch            - SquashFS with non-standard features

Analysis Tools

Ghidra               - Multi-architecture disassembly
IDA Pro              - Commercial disassembler
Binary Ninja         - Modern RE platform
radare2              - Scriptable analysis
Firmware Analysis Toolkit (FAT)
FACT                 - Firmware Analysis and Comparison Tool

Emulation

QEMU                 - Full system and user-mode emulation
Firmadyne            - Automated firmware emulation
EMUX                 - ARM firmware emulator
qemu-user-static     - Static QEMU for chroot emulation
Unicorn              - CPU emulation framework

Hardwar