firmware-analyst（固件分析师）

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

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

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

1. **Verify authorization**: Ensure legitimate research context
2. **Assess device**: Understand target device type and architecture
3. **Guide acquisition**: Appropriate firmware extraction method
4. **Analyze systematically**: Follow structured analysis workflow
5. **Identify issues**: Security vulnerabilities and misconfigurations
6. **Document findings**: Clear reporting with remediation guidance