protocol-reverse

protocol-reverse is a skill for Claude Code, Codex from zhaoxuya520/reverse-skill. It costs 30 tokens per session (1,140 once invoked), scanned A, original, MIT.

A guide to reconstructing how software communicates through a custom protocol, including binary messages, WebSocket frames, Protobuf or gRPC data, and captured network traffic. A protocol is the set of rules that tells two programs how to exchange messages.

In plain words
What is it for?
Use it to analyse PCAP files, identify message fields, lengths, checksums, compression, encryption, handshakes, heartbeats, and request states, then document the recovered protocol.
Why use it?
It helps when the message format and connection states are undocumented, so the data cannot be understood from ordinary API documentation alone.

Skill for Claude CodeCodex

About the project

Reverse Skill is a routing package for AI coding agents that selects appropriate reverse-engineering, penetration-testing, and security-research methods and tools for a given target. It is used for tasks involving APKs, binaries, frontend JavaScript, packet captures, CTF challenges, and authorized penetration testing. Its catalogue add-ons provide the skills and instructions that guide these workflows.

zhaoxuya520/reverse-skill · 34,580 stars · on GitHub

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/zhaoxuya520/reverse-skill/protocol-reverse
Any agent
npx skills add zhaoxuya520/reverse-skill --skill protocol-reverse
Clone the repo
git clone --depth 1 https://github.com/zhaoxuya520/reverse-skill

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for protocol-reverse

README.md
[![agentmods](https://agentmods.dev/badge/skills/zhaoxuya520/reverse-skill/protocol-reverse.svg)](https://agentmods.dev/skills/zhaoxuya520/reverse-skill/protocol-reverse)
Your own site
<a href="https://agentmods.dev/skills/zhaoxuya520/reverse-skill/protocol-reverse"><img src="https://agentmods.dev/badge/skills/zhaoxuya520/reverse-skill/protocol-reverse.svg" alt="Measured on agentmods" height="20"></a>
Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,140 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00030 $0.01140
Opus 5 $0.00015 $0.00570
Sonnet 5 $0.00006 $0.00228
Haiku 4.5 $0.00003 $0.00114

Measured yesterday against content hash f8408273d7ba, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

protocol-reverse scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

3 near-identical copies found in the catalogue:

skills/protocol-reverse/SKILL.md · 98 lines

How it starts

The opening of the file, as written. The whole thing — 98 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Protocol Reverse Engineering

ACTION REQUIRED(读完后立刻执行)

  1. NOW: 读取 ../field-journal/precedent-reverse.md — 确认授权与常规操作边界
  2. NOW: 确认任务是否为协议/流量/序列化格式逆向(非纯 Web 参数签名 → 转 js-reverse/
  3. NOW: 若有目标网络交互 → ../scripts/case-init.ps1 完成 scope;auth 未 granted 禁止对目标 ACT
  4. NEXT: 读取 ../tool-index.md;缺工具 bootstrap(tshark/wireshark 等可能需手动)
  5. ACT: 进入工作流 Phase 1,产出帧布局或消息字典草稿

适用场景

  • 自定义 TCP/UDP 二进制协议
  • Protobuf / gRPC / FlatBuffers / MessagePack
  • WebSocket / MQTT / 私有 RPC
  • PCAP / PCAPNG 还原字段与状态机
  • 客户端-服务端校验、序列号、加密帧头

不走本 skill

情况 去哪
仅 HTTP 参数签名 / JS 加密 js-reverse/
仅 TLS 证书问题 pentest-tools/ 或浏览器代理
固件内协议栈深挖 + 仿真 firmware-pentest/ 后再回本 skill

工作流

Phase 1 — 采集与分诊

□ 拿到样本:PCAP / 代理导出 / 客户端日志 / 二进制
□ 标记方向:C→S / S→C;是否有握手、心跳、重连
□ 固定头?魔数?长度字段?TLV?定长?
□ 是否压缩(zlib/gzip/lz4)或加密(AES/ChaCha 帧内)
□ tshark -r cap.pcap -T fields -e frame.number -e ip.src -e tcp.payload

Phase 2 — 帧布局还原

□ 对齐多个同类消息,找不变字节 / 自增序列号
□ 长度字段:大端/小端、含头/不含头
□ 校验:CRC16/32、checksum、HMAC 位置
□ 画出状态机:Connect → Auth → Ready → Request/Response → Close
□ 工具:Wireshark 自定义 dissector 草稿 / ImHex / 010 Editor 模板 / Kaitai Struct

Phase 3 — 序列化与加密

□ Protobuf:.proto 恢复(blackboxprotobuf / pbtk / protoc --decode_raw)
□ gRPC:HTTP/2 headers + protobuf body
□ 加密:找密钥派生(客户端 so/dll/JS)→ 联合 ida-reverse / js-reverse / apk-reverse
□ 重放:仅在授权 scope 内;先无害字段再敏感操作

Phase 4 — 产物

MUST 产出:
- 消息类型表(name / opcode / fields)
- 至少 1 条可复现的解码命令或脚本
- Evidence:原始 hex 摘录 + 解码结果(脱敏)

工具链

工具 必需 用途 自举
tshark / Wireshark 强烈建议 PCAP 解析 手动 / winget
Python3 解码脚本 系统
blackboxprotobuf 可选 未知 protobuf pip
ImHex / 010 可选 结构模板 手动
IDA / r2 / Ghidra 按需 客户端序列化函数 见对应 skill

参考

  • references/protocol-workflow.md — 帧布局与 Protobuf 速查
  • 相关:../ida-reverse/ ../js-reverse/ ../firmware-pentest/ ../pentest-tools/

路由上下文

上游: MASTER-ROUTING R21 · routing.md
下游: 需客户端算法 → ida-reverse/js-reverse;需利用重放 → pentest-tools/api-security
同级: malware-analysis(C2 协议)、digital-forensics(流量取证)

Read the full file on GitHub · 98 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 98 lines · 30 tokens per session scan A f8408273d7ba

Subscribe to this mod's changes

protocol-reverse is a skill published in the GitHub repository zhaoxuya520/reverse-skill (34,580 stars, last pushed yesterday), licensed MIT. It adds 30 tokens to every session and 1,140 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

Related

Other skills, from other repositories

systematic-debugging

Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.

obra/superpowers · 21 tokens

local-ai-agents

Build local-first AI agents that run entirely on a developer workstation with Microsoft Foundry Local and Qwen function-calling models. Covers Small Language Models (SLMs), the OpenAI-compatible local endpoint, sandboxed local tools, local RAG with Chroma, local MCP servers, hybrid cloud/local routing, and the…

microsoft/ai-agents-for-beginners · 200 tokens

chronicle

Analyze Copilot session history for standup reports, usage tips, session search, and session reindexing. Use when the user asks for a standup, daily summary, usage tips, workflow recommendations, wants to search or find past sessions by keyword/file/PR, wants to reindex their session store, or asks about deleting…

microsoft/vscode · 72 tokens

imagegen

Generate or edit raster images when the task benefits from AI-created bitmap visuals such as photos, illustrations, textures, sprites, mockups, or transparent-background cutouts. Use when Codex should create a brand-new image, transform an existing image, or derive visual variants from references, and the output…

openai/codex · 113 tokens

chat-pet-sprite-creation

Use when creating or changing VS Code chat pet sprite art, sprite sheets, state animations, eye treatments, Stable/Insiders variants, or pet transitions under src/vs/workbench/contrib/chat/browser/widget/media/chatPet.

microsoft/vscode · 53 tokens

cpu-profile-analysis

Analyze V8/Chrome CPU profiles (.cpuprofile) and DevTools trace files (Trace-.json). Use when: profiling performance, investigating slow functions, comparing code paths, finding bottlenecks, analyzing timeToRequest, understanding call trees from sampling profiler data, analyzing layout/paint/rendering, investigating…

microsoft/vscode · 71 tokens