mcp-shell

mcp-shell 🐚

A robust Model Context Protocol (MCP) server that provides secure shell command execution capabilities to AI assistants and other MCP clients. In other words: the brain thinks, this runs the commands.

🧠💥🖥️ Think of mcp-shell as the command-line actuator for your LLM. While language models reason about the world, mcp-shell is what lets them touch it.

What is this?

This tool creates a bridge between AI systems and your shell environment through the standardized MCP protocol. It exposes the system shell as a structured tool, enabling autonomous workflows, tool-assisted reasoning, and real-world problem solving.

Built on top of the official MCP SDK for Go: mark3labs/mcp-go.

It's written in Go, integrates directly with mcp-go, and provides a clean path from thought to execution. I'm aware similar projects exist — this one’s mine. It solves the problem the way I want it solved: minimal, composable, auditable.

Out of the box it runs isolated via Docker, but that's just a start. The roadmap includes support for optional jailing mechanisms like chroot, namespaces, and syscall-level confinement — without depending on Docker for everything.

Features

• 🔒 Security First: Configurable command allowlists, blocklists, and execution constraints
• 🐳 Docker Ready: Lightweight Alpine-based container for secure isolation
• 📊 Structured Responses: JSON-formatted output with stdout, stderr, exit codes, and execution metadata
• 🔄 Binary Data Support: Optional base64 encoding for handling binary command output
• ⚡ Performance Monitoring: Execution time tracking and resource limits
• 📋 Audit Logging: Complete command execution audit trail with structured logging
• 🎯 Context Aware: Supports command execution with proper context cancellation
• ⚙️ Environment Configuration: Full configuration via environment variables

Security Features

• Command Validation: Allowlist/blocklist with regex pattern matching
• Execution Limits: Configurable timeouts and output size limits
• User Isolation: Run commands as unprivileged users
• Working Directory: Restrict execution to specific directories
• Audit Trail: Complete logging of all command executions
• Resource Limits: Memory and CPU usage constraints

Quick Start

Prerequisites

• Go 1.23 or later
• Unix-like system (Linux, macOS, WSL)
• Docker (optional, for containerized deployment)

Installation

git clone https://github.com/sonirico/mcp-shell
cd mcp-shell
make install

Basic Usage

# Run with default configuration (if installed system-wide)
mcp-shell

# Or run locally
make run

# Run with security enabled (creates temporary config)
make run-secure

# Run with custom config file
MCP_SHELL_SEC_CONFIG_FILE=security.json mcp-shell

# Run with environment overrides
MCP_SHELL_LOG_LEVEL=debug mcp-shell

Docker Deployment (Recommended)

# Build Docker image
make docker-build

# Run in secure container
make docker-run-secure

# Run with shell access for debugging
make docker-shell

Configuration

Environment Variables

Basic server and logging configuration via environment variables:

Server Configuration

• MCP_SHELL_SERVER_NAME: Server name (default: "mcp-shell 🐚")
• MCP_SHELL_VERSION: Server version (set at compile time)

Logging Configuration

• MCP_SHELL_LOG_LEVEL: Log level (debug, info, warn, error, fatal)
• MCP_SHELL_LOG_FORMAT: Log format (json, console)
• MCP_SHELL_LOG_OUTPUT: Log output (stdout, stderr, file)

Configuration File

• MCP_SHELL_SEC_CONFIG_FILE: Path to YAML configuration file

Security Configuration (YAML Only)

Security settings are configured exclusively via YAML configuration file:

export MCP_SHELL_SEC_CONFIG_FILE=security.yaml

Example security configuration file:

security:
  enabled: true
  allowed_commands:
    - ls
    - cat
    - grep
    - find
    - echo
  blocked_commands:
    - rm -rf
    - sudo
    - chmod
  blocked_patterns:
    - 'rm\s+.*-rf.*'
    - 'sudo\s+.*'
  max_execution_time: 30s
  working_directory: /tmp/mcp-workspace
  max_output_size: 1048576
  audit_log: true

Tool Parameters

• command (string, required): Shell command to execute
• base64 (boolean, optional): Return stdout/stderr as base64-encoded strings

Response Format

{
  "status": "success|error",
  "exit_code": 0,
  "stdout": "command output",
  "stderr": "error output", 
  "command": "executed command",
  "execution_time": "100ms",
  "security_info": {
    "security_enabled": true,
    "working_dir": "/tmp/mcp-workspace",
    "timeout_applied": true
  }
}

Integration Examples

With Claude Desktop

{
  "mcpServers": {
    "shell": {
      "command": "docker",
      "args": ["run", "--rm", "-i", "mcp-shell:latest"],
      "env": {
        "MCP_SHELL_SECURITY_ENABLED": "true",
        "MCP_SHELL_LOG_LEVEL": "info"
      }
    }
  }
}

Production Deployment

# Build and install
make build
sudo make install-bin

# Set environment variables for basic config
export MCP_SHELL_LOG_LEVEL=info
export MCP_SHELL_LOG_FORMAT=json
export MCP_SHELL_SEC_CONFIG_FILE=/etc/mcp-shell/config.json

# Security is configured in the JSON file only
# Run service
mcp-shell

Development

# Install dependencies and dev tools
make install dev-tools

# Format code
make fmt

# Run tests
make test

# Run linter
make lint

# Build for release
make release

# Generate config example
make config-example

Security Considerations

⚠️ Important Security Notes

1. Default Mode: Runs with full system access when security is disabled (which is, of course, a terrible idea — unless you're into that).
2. Container Isolation: Use Docker deployment for additional security layers
3. User Privileges: Run as non-root user in production
4. Network Access: Commands can access network unless explicitly restricted
5. File System: Can read/write files based on user permissions

Recommended Production Setup

Create security.yaml:

security:
  enabled: true
  allowed_commands:
    - ls
    - cat
    - head
    - tail
    - grep
    - find
    - wc
    - sort
    - uniq
  blocked_patterns:
    - 'rm\s+.*-rf.*'
    - 'sudo\s+.*'
    - 'chmod\s+(777|666)'
    - '>/dev/'
    - 'curl.*\|.*sh'
  max_execution_time: 10s
  working_directory: /tmp/mcp-workspace
  max_output_size: 524288
  audit_log: true

Set environment:

export MCP_SHELL_SEC_CONFIG_FILE=security.yaml
export MCP_SHELL_LOG_LEVEL=info
export MCP_SHELL_LOG_FORMAT=json

Contributing

1. Fork the repository
2. Create feature branch (git checkout -b feature/amazing-feature)
3. Commit changes (git commit -m 'Add amazing feature')
4. Push to branch (git push origin feature/amazing-feature)
5. Open Pull Request

Ensure code is formatted (make fmt) and passes tests (make test).

License

MIT License - See LICENSE file for details.