Shell MCP Server

A Node.js implementation of the Model Context Protocol (MCP) that provides secure shell command execution capabilities. This server allows AI models to execute shell commands in a controlled environment with built-in security measures. Easily integrates with Claude Desktop for connecting Claude with your shell.

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Features

- MCP-compliant server implementation
- Secure command execution with blacklist protection
- Command existence validation
- Standard I/O based transport
- Error handling and graceful shutdown

Installation

Run npx mcp-shell.

To add it to Claude Desktop, run npx mcp-shell config. Or add npx -y mcp-shell to your config manually.

Start (or restart) Claude Desktop and you should see the MCP tool listed on the landing page.

Security Features

The server implements several security measures:

1. Command Blacklisting

- Prevents execution of dangerous system commands
- Blocks access to critical system modifications
- Protects against file system destruction
- Prevents privilege escalation

2. Command Validation
- Verifies command existence before execution
- Validates against the blacklist
- Returns clear error messages for invalid commands

Available Tools

The server provides one tool:

run_command

Executes a shell command and returns its output.

Input Schema:

{
  "type": "object",
  "properties": {
    "command": { "type": "string" }
  }
}

Response:

- Success: Command output as plain text
- Error: Error message as plain text

Blacklisted Commands

The following command categories are blocked for security:

- File System Destruction Commands (rm, rmdir, del)
- Disk/Filesystem Commands (format, mkfs, dd)
- Permission/Ownership Commands (chmod, chown)
- Privilege Escalation Commands (sudo, su)
- Code Execution Commands (exec, eval)
- System Communication Commands (write, wall)
- System Control Commands (shutdown, reboot, init)

Error Handling

The server includes comprehensive error handling:

- Command not found errors
- Blacklisted command errors
- Execution errors
- MCP protocol errors
- Graceful shutdown on SIGINT

Implementation Details

The server is built using:

- Model Context Protocol SDK
- StdioServerTransport for communication
- execa for command execution
- command-exists for command validation

Development

To modify the security settings, you can:

1. Edit the BLACKLISTED_COMMANDS set to adjust blocked commands
2. Modify the validateCommand function to add additional validation rules
3. Enhance the command parsing logic in the CallToolRequestSchema handler