$npx -y skills add zhaoxuya520/reverse-skill --skill competition-pcap-protocolInternal downstream skill for ctf-sandbox-orchestrator. CTF-sandbox workflow for packet capture analysis, session reconstruction, application-protocol decoding, stream reassembly, beacon timing, and packet-to-process correlation. Use when the user asks to analyze a PCAP, rebuild
| 1 | # Competition PCAP Protocol |
| 2 | |
| 3 | Use this skill only as a downstream specialization after `$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. |
| 4 | |
| 5 | Use this skill when the decisive evidence sits inside packet order, protocol framing, or stream reconstruction rather than a single IOC or host log. |
| 6 | |
| 7 | Reply in Simplified Chinese unless the user explicitly requests English. |
| 8 | |
| 9 | ## Quick Start |
| 10 | |
| 11 | 1. Establish the capture boundaries first: hosts, time span, interfaces, missing packets, retransmits, and stream count. |
| 12 | 2. Group traffic into sessions before decoding payload semantics. |
| 13 | 3. Record protocol framing, sequence, timing, and transferred artifacts together instead of as isolated packets. |
| 14 | 4. Correlate packet evidence with host, malware, or app behavior only after the session is reconstructed. |
| 15 | 5. Reproduce the smallest decoded stream or transferred artifact that proves the challenge path. |
| 16 | |
| 17 | ## Workflow |
| 18 | |
| 19 | ### 1. Build The Session Map |
| 20 | |
| 21 | - Identify endpoints, protocols, ports, TLS handshakes, DNS lookups, websocket upgrades, and long-lived streams. |
| 22 | - Note missing capture coverage, asymmetric routing, packet loss, or reassembly issues before drawing conclusions. |
| 23 | - Separate control channels, bulk transfers, keepalives, and noise. |
| 24 | |
| 25 | ### 2. Decode The Protocol Boundary |
| 26 | |
| 27 | - Reassemble TCP streams or UDP conversations before interpreting fields. |
| 28 | - Recover framing, message order, custom headers, binary fields, compression, encryption boundaries, and object transfers. |
| 29 | - Keep payload direction, timing, and session state aligned with each decoded message. |
| 30 | |
| 31 | ### 3. Tie Packets To Behavior |
| 32 | |
| 33 | - Show which packet sequence maps to which host event, malware branch, login flow, upload, exfiltration step, or command channel. |
| 34 | - Distinguish protocol recognition from artifact recovery: naming HTTP, DNS, or a custom C2 is not enough without decoded content or proven downstream effect. |
| 35 | - If the task becomes mostly a host timeline problem after decode, switch to the tighter forensic timeline skill. |
| 36 | |
| 37 | ## Read This Reference |
| 38 | |
| 39 | - Load `references/pcap-protocol.md` for the session checklist, decode checklist, and evidence packaging. |
| 40 | - If the hard part is a WebSocket or SSE handshake, subscription flow, realtime frames, or frame-driven state, prefer `$competition-websocket-runtime`. |
| 41 | - If the hard part is a custom handshake, framing, checksum, sequence dependency, or deterministic replay harness, prefer `$competition-custom-protocol-replay`. |
| 42 | |
| 43 | ## What To Preserve |
| 44 | |
| 45 | - Stream IDs, endpoint pairs, packet ranges, timestamps, protocol framing, and object boundaries |
| 46 | - Decoded requests, responses, commands, transferred files, and the session that carried them |
| 47 | - The exact packet sequence or reconstructed stream that proves the challenge behavior |