MCPInstall

protocol-reverse-engineering

Master network protocol reverse engineering including packet analysis, protocol dissection, and custom protocol documentation. Use when analyzing network traffic, understanding proprietary protocols, or debugging network communication.

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12.8K
Last 24h
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#3908
Security
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Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/wshobson/agents --skill protocol-reverse-engineering
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads protocol-reverse-engineering automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

Security audits

Independent scans of the skill's instructions and bundled files.

Gen Agent Trust Hub PassSAFE ·This skill provides tools and techniques for network protocol reverse engineering. While the content is educational and uses industry-standard tools, the inherent capability to capture and inject network traffic presents an indirect prompt injection surface when processing untrusted data.
Socket Warn1 alert: gptSecurity
Snyk PassLOW ·Risk: LOW · No issues
Runlayer WarnMEDIUM ·1/1 file flagged
ZeroLeaks PassLOW ·1 finding · Score: 86/100

SKILL.md

The instructions your agent reads when the skill is triggered.

Protocol Reverse Engineering

Comprehensive techniques for capturing, analyzing, and documenting network protocols for security research, interoperability, and debugging.

Traffic Capture

Wireshark Capture

# Capture on specific interface
wireshark -i eth0 -k

# Capture with filter
wireshark -i eth0 -k -f "port 443"

# Capture to file
tshark -i eth0 -w capture.pcap

# Ring buffer capture (rotate files)
tshark -i eth0 -b filesize:100000 -b files:10 -w capture.pcap

tcpdump Capture

# Basic capture
tcpdump -i eth0 -w capture.pcap

# With filter
tcpdump -i eth0 port 8080 -w capture.pcap

# Capture specific bytes
tcpdump -i eth0 -s 0 -w capture.pcap  # Full packet

# Real-time display
tcpdump -i eth0 -X port 80

Man-in-the-Middle Capture

# mitmproxy for HTTP/HTTPS
mitmproxy --mode transparent -p 8080

# SSL/TLS interception
mitmproxy --mode transparent --ssl-insecure

# Dump to file
mitmdump -w traffic.mitm

# Burp Suite
# Configure browser proxy to 127.0.0.1:8080

Protocol Analysis

Wireshark Analysis

# Display filters
tcp.port == 8080
http.request.method == "POST"
ip.addr == 192.168.1.1
tcp.flags.syn == 1 && tcp.flags.ack == 0
frame contains "password"

# Following streams
Right-click > Follow > TCP Stream
Right-click > Follow > HTTP Stream

# Export objects
File > Export Objects > HTTP

# Decryption
Edit > Preferences > Protocols > TLS
  - (Pre)-Master-Secret log filename
  - RSA keys list

tshark Analysis

# Extract specific fields
tshark -r capture.pcap -T fields -e ip.src -e ip.dst -e tcp.port

# Statistics
tshark -r capture.pcap -q -z conv,tcp
tshark -r capture.pcap -q -z endpoints,ip

# Filter and extract
tshark -r capture.pcap -Y "http" -T json > http_traffic.json

# Protocol hierarchy
tshark -r capture.pcap -q -z io,phs

Scapy for Custom Analysis

from scapy.all import *

# Read pcap
packets = rdpcap("capture.pcap")

# Analyze packets
for pkt in packets:
    if pkt.haslayer(TCP):
        print(f"Src: {pkt[IP].src}:{pkt[TCP].sport}")
        print(f"Dst: {pkt[IP].dst}:{pkt[TCP].dport}")
        if pkt.haslayer(Raw):
            print(f"Data: {pkt[Raw].load[:50]}")

# Filter packets
http_packets = [p for p in packets if p.haslayer(TCP)
                and (p[TCP].sport == 80 or p[TCP].dport == 80)]

# Create custom packets
pkt = IP(dst="target")/TCP(dport=80)/Raw(load="GET / HTTP/1.1\r\n")
send(pkt)

Protocol Identification

Common Protocol Signatures

HTTP        - "HTTP/1." or "GET " or "POST " at start
TLS/SSL     - 0x16 0x03 (record layer)
DNS         - UDP port 53, specific header format
SMB         - 0xFF 0x53 0x4D 0x42 ("SMB" signature)
SSH         - "SSH-2.0" banner
FTP         - "220 " response, "USER " command
SMTP        - "220 " banner, "EHLO" command
MySQL       - 0x00 length prefix, protocol version
PostgreSQL  - 0x00 0x00 0x00 startup length
Redis       - "*" RESP array prefix
MongoDB     - BSON documents with specific header

Protocol Header Patterns

+--------+--------+--------+--------+
|  Magic number / Signature         |
+--------+--------+--------+--------+
|  Version       |  Flags          |
+--------+--------+--------+--------+
|  Length        |  Message Type   |
+--------+--------+--------+--------+
|  Sequence Number / Session ID     |
+--------+--------+--------+--------+
|  Payload...                       |
+--------+--------+--------+--------+

Before binary protocol or encryption analysis, read parsers, structure identification, and TLS techniques.

Before documenting a protocol or writing a dissector, read the specification template and Lua example.

Active Testing

Fuzzing with Boofuzz

from boofuzz import *

def main():
    session = Session(
        target=Target(
            connection=TCPSocketConnection("target", 8888)
        )
    )

    # Define protocol structure
    s_initialize("HELLO")
    s_static(b"\x50\x52\x4f\x54")  # Magic
    s_word(1, name="version")       # Version
    s_word(0x01, name="type")       # Type (HELLO)
    s_size("payload", length=4)     # Length field
    s_block_start("payload")
    s_dword(0x12345678, name="client_id")
    s_word(0, name="flags")
    s_block_end()

    session.connect(s_get("HELLO"))
    session.fuzz()

if __name__ == "__main__":
    main()

Replay and Modification

from scapy.all import *

# Replay captured traffic
packets = rdpcap("capture.pcap")
for pkt in packets:
    if pkt.haslayer(TCP) and pkt[TCP].dport == 8888:
        send(pkt)

# Modify and replay
for pkt in packets:
    if pkt.haslayer(Raw):
        # Modify payload
        original = pkt[Raw].load
        modified = original.replace(b"client", b"CLIENT")
        pkt[Raw].load = modified
        # Recalculate checksums
        del pkt[IP].chksum
        del pkt[TCP].chksum
        send(pkt)

Best Practices

Analysis Workflow

  1. Capture traffic: Multiple sessions, different scenarios
  2. Identify boundaries: Message start/end markers
  3. Map structure: Fixed header, variable payload
  4. Identify fields: Compare multiple samples
  5. Document format: Create specification
  6. Validate understanding: Implement parser/generator
  7. Test edge cases: Fuzzing, boundary conditions

Common Patterns to Look For

  • Magic numbers/signatures at message start
  • Version fields for compatibility
  • Length fields (often before variable data)
  • Type/opcode fields for message identification
  • Sequence numbers for ordering
  • Checksums/CRCs for integrity
  • Timestamps for timing
  • Session/connection identifiers

FAQ

What does the protocol-reverse-engineering skill do?

Master network protocol reverse engineering including packet analysis, protocol dissection, and custom protocol documentation. Use when analyzing network traffic, understanding proprietary protocols, or debugging network communication.

How do I install protocol-reverse-engineering?

Run npx skills add https://github.com/wshobson/agents --skill protocol-reverse-engineering in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/protocol-reverse-engineering/ (personal) or .claude/skills/protocol-reverse-engineering/ (project).

Which AI agents can use protocol-reverse-engineering?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is protocol-reverse-engineering safe to install?

Security partners have reviewed it: Gen Agent Trust Hub passed; Socket flagged items to review; Snyk passed; Runlayer flagged items to review; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.

Who maintains protocol-reverse-engineering?

It is published by wshobson in wshobson/agents. It has 12,844 recorded installs.

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