competition-custom-protocol-replay

Compare original and translation side by side

🇺🇸

Original

English

🇨🇳

Chinese

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.

此技能仅可作为下游专用技能，在

$ctf-sandbox-orchestrator

已激活并完成沙箱假设、节点所有权和证据优先级确立后使用。若上述条件尚未满足，请先返回

$ctf-sandbox-orchestrator

。

当核心难点不只是识别协议名称，而是复现被系统接受所需的精确消息顺序和状态时，使用本技能。

除非用户明确要求英文回复，否则请使用简体中文回复。

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

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.

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.

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.

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

Canonical transcript, message types, field boundaries, checksums, counters, and session identifiers
Original capture slices and the replay harness inputs that produce acceptance
The exact mutation that flips the protocol from rejected to accepted, or vice versa