MCP Shell Server

A secure shell command execution server implementing the Model Context Protocol (MCP). This server allows remote execution of whitelisted shell commands with support for stdin input.

Features

• Secure Command Execution: Only whitelisted commands can be executed
• Standard Input Support: Pass input to commands via stdin
• Comprehensive Output: Returns stdout, stderr, exit status, and execution time
• Shell Operator Safety: Validates commands after shell operators (; , &&, ||, |)
• Timeout Control: Set maximum execution time for commands

MCP client setting in your Claude.app

Published version

code ~/Library/Application\ Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "shell": {
      "command": "uvx",
      "args": [
        "mcp-shell-server"
      ],
      "env": {
        "ALLOW_COMMANDS": "ls,cat,pwd,grep,wc,touch,find"
      }
    },
  }
}

Local version

Configuration

code ~/Library/Application\ Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "shell": {
      "command": "uv",
      "args": [
        "--directory",
        ".",
        "run",
        "mcp-shell-server"
      ],
      "env": {
        "ALLOW_COMMANDS": "ls,cat,pwd,grep,wc,touch,find"
      }
    },
  }
}

Installation

pip install mcp-shell-server

Usage

Starting the Server

ALLOW_COMMANDS="ls,cat,echo" uvx mcp-shell-server
# Or using the alias
ALLOWED_COMMANDS="ls,cat,echo" uvx mcp-shell-server

The ALLOW_COMMANDS (or its alias ALLOWED_COMMANDS ) environment variable specifies which commands are allowed to be executed. Commands can be separated by commas with optional spaces around them.

Valid formats for ALLOW_COMMANDS or ALLOWED_COMMANDS:

ALLOW_COMMANDS="ls,cat,echo"          # Basic format
ALLOWED_COMMANDS="ls ,echo, cat"      # With spaces (using alias)
ALLOW_COMMANDS="ls,  cat  , echo"     # Multiple spaces

Request Format

# Basic command execution
{
    "command": ["ls", "-l", "/tmp"]
}

# Command with stdin input
{
    "command": ["cat"],
    "stdin": "Hello, World!"
}

# Command with timeout
{
    "command": ["long-running-process"],
    "timeout": 30  # Maximum execution time in seconds
}

# Command with working directory and timeout
{
    "command": ["grep", "-r", "pattern"],
    "directory": "/path/to/search",
    "timeout": 60
}

Response Format

Successful response:

{
    "stdout": "command output",
    "stderr": "",
    "status": 0,
    "execution_time": 0.123
}

Error response:

{
    "error": "Command not allowed: rm",
    "status": 1,
    "stdout": "",
    "stderr": "Command not allowed: rm",
    "execution_time": 0
}

Security

The server implements several security measures:

1. Command Whitelisting: Only explicitly allowed commands can be executed
2. Shell Operator Validation: Commands after shell operators (;, &&, ||, |) are also validated against the whitelist
3. No Shell Injection: Commands are executed directly without shell interpretation

Development

Setting up Development Environment

1. Clone the repository

git clone https://github.com/yourusername/mcp-shell-server.git
cd mcp-shell-server

2. Install dependencies including test requirements

pip install -e ".[test]"

Running Tests

pytest

API Reference

Request Arguments

Field	Type	Required	Description
command	string[]	Yes	Command and its arguments as array elements
stdin	string	No	Input to be passed to the command
directory	string	No	Working directory for command execution
timeout	integer	No	Maximum execution time in seconds

Response Fields

Field	Type	Description
stdout	string	Standard output from the command
stderr	string	Standard error output from the command
status	integer	Exit status code
execution_time	float	Time taken to execute (in seconds)
error	string	Error message (only present if failed)

Requirements

• Python 3.11 or higher
• mcp>=1.1.0

License

MIT License - See LICENSE file for details