competition-custom-protocol-replay

competition-custom-protocol-replay is a skill for Claude Code, Codex from 2233admin/reverse-skill-evolver. It costs 116 tokens per session (595 once invoked), scanned A, a copy of competition-custom-protocol-replay, MIT.

An internal workflow for capture-the-flag challenges involving unknown communication protocols. It focuses on reconstructing message formats, checksums, ordering, and the session steps needed for a server to accept a replay.

In plain words
What is it for?
Use it to analyze handshakes, authentication, commands, keepalives, framing, sequence numbers, and checksums, then reproduce the smallest accepted exchange.
Why use it?
It helps when simply decoding individual messages is not enough because acceptance depends on the exact conversation and changing state.

Skill for Claude CodeCodex

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/2233admin/reverse-skill-evolver/competition-custom-protocol-replay
Any agent
npx skills add 2233admin/reverse-skill-evolver --skill competition-custom-protocol-replay
Clone the repo
git clone --depth 1 https://github.com/2233admin/reverse-skill-evolver

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 competition-custom-protocol-replay

README.md
[![agentmods](https://agentmods.dev/badge/skills/2233admin/reverse-skill-evolver/competition-custom-protocol-replay.svg)](https://agentmods.dev/skills/2233admin/reverse-skill-evolver/competition-custom-protocol-replay)
Your own site
<a href="https://agentmods.dev/skills/2233admin/reverse-skill-evolver/competition-custom-protocol-replay"><img src="https://agentmods.dev/badge/skills/2233admin/reverse-skill-evolver/competition-custom-protocol-replay.svg" alt="Measured on agentmods" height="20"></a>
Per session 116 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 595 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00116 $0.00595
Opus 5 $0.00058 $0.00298
Sonnet 5 $0.00023 $0.00119
Haiku 4.5 $0.00012 $0.00060

Measured 4d ago against content hash b4ffc7e78122, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

competition-custom-protocol-replay 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 4d ago.

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

This is a copy

100% identical to competition-custom-protocol-replay — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

CTF-Sandbox-Orchestrator/competition-custom-protocol-replay/SKILL.md · 51 lines

How it starts

The opening of the file, as written. The whole thing — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Competition Custom Protocol Replay

Use this skill only as a downstream specialization after $ctf-sandbox-orchestrator is already active and has established sandbox assumptions, node ownership, and evidence priorities. If that has not happened yet, return to $ctf-sandbox-orchestrator first.

Use this skill when the hard part is not merely naming the protocol, but reproducing the exact message order and state needed for acceptance.

Reply in Simplified Chinese unless the user explicitly requests English.

Quick Start

  1. Identify client and server roles, session boundaries, and reset conditions before decoding field semantics.
  2. Recover framing, lengths, delimiters, sequence numbers, checksums, nonces, and state transitions before broad replay attempts.
  3. Keep one canonical transcript of a successful exchange.
  4. Change one field or one message at a time while replaying.
  5. Reproduce the smallest accepted conversation that proves the decisive branch.

Workflow

1. Map The Session State Machine

  • Identify handshake, negotiation, authentication, keepalive, command, and teardown phases.
  • Record which fields are static, which are derived, and which depend on prior messages.
  • Keep message order, direction, and timing tied to the same session identity.

2. Recover Framing And Integrity

  • Reconstruct lengths, delimiters, type bytes, checksums, MACs, counters, compression, or encryption boundaries.
  • Distinguish transport framing from application-level framing.
  • Note exactly where server acceptance changes when one field or step is mutated.

3. Build The Minimal Replay Harness

  • Reduce the path to the smallest transcript that reaches the accepted state, parser branch, command effect, or artifact.
  • Preserve both the original captured sequence and the replayed minimal sequence.
  • If the problem is mainly generic PCAP or stream decoding with no stateful replay requirement, switch back to the broader PCAP skill.

Read This Reference

  • Load references/custom-protocol-replay.md for the state-machine checklist, transcript checklist, and evidence packaging.

Read the full file on GitHub · 51 lines

Files

What ships with it

2 files 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. 4d ago First seen · 51 lines · 116 tokens per session scan A b4ffc7e78122

Subscribe to this mod's changes

competition-custom-protocol-replay is a skill published in the GitHub repository 2233admin/reverse-skill-evolver (13 stars, last pushed 23d ago), licensed MIT. It adds 116 tokens to every session and 595 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to competition-custom-protocol-replay, differing in 0 lines, and is treated as a copy.

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