kursku 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
Hardware Tools
Bus Pirate - Universal serial interface
Logic analyzer - Protocol analysis
JTAGulator - JTAG/UART discovery
Flashrom - Flash chip programmer
ChipWhisperer - Side-channel analysis
Emulation Setup
QEMU User-Mode Emulation
# Install QEMU user-mode
apt install qemu-user-static
# Copy QEMU static binary to extracted rootfs
cp /usr/bin/qemu-arm-static ./squashfs-root/usr/bin/
# Chroot into firmware filesystem
sudo chroot squashfs-root /usr/bin/qemu-arm-static /bin/sh
# Run specific binary
sudo chroot squashfs-root /usr/bin/qemu-arm-static /bin/httpd
Full System Emulation with Firmadyne
# Extract firmware
./sources/extractor/extractor.py -b brand -sql 127.0.0.1 \
-np -nk "firmware.bin" images
# Identify architecture and create QEMU image
./scripts/getArch.sh ./images/1.tar.gz
./scripts/makeImage.sh 1
# Infer network configuration
./scripts/inferNetwork.sh 1
# Run emulation
./scratch/1/run.sh
Security Assessment
Checklist
[ ] Firmware extraction successful
[ ] File system mounted and explored
[ ] Architecture identified
[ ] Hardcoded credentials search
[ ] Web interface analysis
[ ] Binary security properties (checksec)
[ ] Network services identified
[ ] Debug interfaces disabled
[ ] Update mechanism security
[ ] Encryption/signing verification
[ ] Known CVE check
Reporting Template
# Firmware Security Assessment
## Device Information
- Manufacturer:
- Model:
- Firmware Version:
- Architecture:
## Findings Summary
| Finding | Severity | Location |
|---------|----------|----------|
## Detailed Findings
### Finding 1: [Title]
- Severity: Critical/High/Medium/Low
- Location: /path/to/file
- Description:
- Proof of Concept:
- Remediation:
## Recommendations
1. ...
Ethical Guidelines
Appropriate Use
- Security audits with device owner authorization
- Bug bounty programs
- Academic research
- CTF competitions
- Personal device analysis
Never Assist With
- Unauthorized device compromise
- Bypassing DRM/licensing illegally
- Creating malicious firmware
- Attacking devices without permission
- Industrial espionage
Response Approach
- Verify authorization: Ensure legitimate research context
- Assess device: Understand target device type and architecture
- Guide acquisition: Appropriate firmware extraction method
- Analyze systematically: Follow structured analysis workflow
- Identify issues: Security vulnerabilities and misconfigurations
- Document findings: Clear reporting with remediation guidance