Reverse Shell Async

OpenCROW I/O - Reverse Shell Async

Use this skill only for authorized CTF challenges, isolated labs, or systems you own. It manages the listener side of one inbound TCP session. It does not generate, suggest, or deploy reverse-shell payloads.

Runtime preflight

Prefer the opencrow-netcat-mcp server in a full installation. Start with toolbox_info, toolbox_verify, and toolbox_capabilities, then use session_listen. In a skills-only installation, probe rsx with command -v rsx; if it is unavailable, use the relative scripts/rsx resource. Report the exact missing command if neither path exists.

Safety defaults

• The listener binds to 127.0.0.1 unless --bind-host is supplied.
• A non-loopback bind is rejected unless --allow-remote is explicit.
• Use --expected-peer IP_OR_CIDR whenever the peer address is known. Mismatches are logged, closed, and do not consume the listener.
• A named listener accepts exactly one matching connection. It does not reconnect and does not serve multiple clients.
• Use a distinct session name for each authorized target flow, and stop live sessions when work is complete.

MCP-first workflow

1. Call session_listen with a name and port. Port 0 requests an available local port; read the actual port from the returned status.
2. Poll session_status until its state is connected.
3. Use session_send with exactly one of data, hex, or base64.
4. Use session_read for the escaped event log. Treat the rx.raw artifact as the exact received bytes.
5. Call session_stop if the listener or connection is still running.

CLI fallback

# Loopback listener on an automatically selected port
rsx listen --name lab --port 0

# Explicit authorized remote listener restricted to one source CIDR
rsx listen --name lab --bind-host 0.0.0.0 --port 4444 \
  --allow-remote --expected-peer 192.0.2.25/32

# Text and exact-byte input
rsx send --name lab --data 'id' --newline
rsx send --name lab --hex '03'
rsx send --name lab --base64 'AAEC/w=='

# Observe and stop
rsx status --name lab
rsx read --name lab --tail 40
rsx stop --name lab

--newline is valid only with text. Hex input may contain ASCII whitespace but must have valid, paired digits. Base64 input is strict. Decoded sends are limited to 1 MiB. The skill deliberately performs no automated PTY upgrade.

State and artifacts

State is stored at /tmp/opencrow-nc-async// unless OPENCROW_NC_ASYNC_DIR is set. Important states are starting, listening, connected, remote_closed, accept_timeout, stopped, and error.

• meta.json: mode, state, bind, peer, and timestamps
• io.log: safely escaped state, TX, and RX events
• rx.raw: exact bytes received from the peer
• daemon.log: listener diagnostics
• tx.fifo: internal asynchronous send channel

References

• Read references/operations.md for state transitions, error recovery, and raw-data rules.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: 02loveslollipop
• Source: 02loveslollipop/OpenCROW
• License: Apache-2.0

Install and usage instructions live in the source repository linked above.