47 lines
1.8 KiB
Python
47 lines
1.8 KiB
Python
#!/usr/bin/env python3
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"""shellmcp: an MCP server with one tool, `run`, that runs a bash command. Stdlib only, stdio.
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--mode readonly (default) runs every command in a bubblewrap sandbox: the filesystem is
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read-only except a private /tmp, there is no network, no other process is visible, and the
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--hide paths (always ~/.ssh and ~/.gnupg) look empty. --mode all runs commands with the
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user's full permissions; let the MCP client ask before each call.
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"""
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import argparse
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import getpass
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import json
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import os
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import shutil
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import signal
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import socket
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import subprocess
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import sys
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ENV = {"PAGER": "cat", "GIT_PAGER": "cat", "NO_COLOR": "1", "TERM": "dumb"}
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def cut(text, limit):
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"""text, or its head and tail around a note when it is longer than limit."""
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if len(text) <= limit:
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return text
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half = limit // 2
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return f"{text[:half]}\n[... {len(text) - 2 * half} characters cut ...]\n{text[-half:]}"
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def run(command, cwd, timeout=60, limit=8000, prefix=()):
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"""The exit code and combined stdout and stderr of `bash -c command`, as one text."""
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proc = subprocess.Popen([*prefix, "bash", "-c", command], cwd=cwd, stdin=subprocess.DEVNULL,
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stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
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env={**os.environ, **ENV}, start_new_session=True)
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try:
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out, _ = proc.communicate(timeout=timeout)
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head = f"exit code {proc.returncode}"
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except subprocess.TimeoutExpired:
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os.killpg(proc.pid, signal.SIGKILL)
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try:
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out, _ = proc.communicate(timeout=5)
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except subprocess.TimeoutExpired: # a process left the group and holds the pipe
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out = b""
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head = f"timed out after {timeout} s, killed"
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return f"{head}\n{cut(out.decode(errors='replace'), limit)}"
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