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MCP Command Server

Secure JSON-RPC API for Remote Command Execution

MCP Command Server provides a secure, containerized interface for remote command execution with built-in pattern-based security validation, comprehensive API documentation, and enterprise-ready deployment configurations.

📋 Table of Contents

• 🔍 Overview
• ✨ Features
• 🏗️ Architecture
• 🚀 Installation
• 🧰 Usage
• 📚 API Documentation
• 🔒 Security
• 💻 Development
• 🧪 Testing
• 👥 Contributing
• 📄 License

🔍 Overview

MCP Command Server provides a JSON-RPC 2.0 compliant API for executing shell commands on the server. It’s designed with security in mind, featuring command pattern exclusion to prevent potentially harmful operations. The server is fully containerized with Docker and includes comprehensive API documentation accessible directly through the API.

✨ Features

• JSON-RPC 2.0 API: Standardized interface for command execution
• Command Security: Pattern-based command filtering to block potentially harmful operations
• Self-Documenting: Built-in /context endpoint serving markdown documentation
• Containerized: Ready-to-use Docker configuration
• Production-Ready: Security-focused design with non-root execution
• Developer-Friendly: Complete Postman collection for testing

🏗️ Architecture

flowchart TB
    Client[Client] -->|HTTP POST JSON-RPC| Server[MCP Command Server]
    Client -->|HTTP GET| Context["/context" Documentation]
    
    subgraph Server["MCP Command Server (Port 3030)"]
        API[JSON-RPC API] --> Validator[Command Validator]
        Validator -->|if safe| Executor[Command Executor]
        Validator -->|if unsafe| Reject[Reject Command]
        Context
    end
    
    Validator --> ExcludeYAML[exclude.yaml]
    Context --> ContextMD[.context]
    
    Executor -->|execute| Shell[Shell]
    Shell --> Results[Command Results]
    Results --> API
    
    classDef container fill:#326ce5,stroke:#fff,stroke-width:1px,color:#fff;
    classDef component fill:#fff,stroke:#000,stroke-width:1px,color:#000;
    classDef config fill:#f9f,stroke:#333,stroke-width:1px,color:#333;
    
    class Server,Shell container;
    class API,Validator,Executor,Context,Reject,Results component;
    class ExcludeYAML,ContextMD config;

Component Flow

sequenceDiagram
    participant Client
    participant Server as MCP Command Server
    participant Validator
    participant Executor
    participant Shell
    
    Client->>Server: POST / {JSON-RPC Request}
    Server->>Validator: Validate command
    
    alt Command matches exclusion pattern
        Validator->>Server: Reject (Security violation)
        Server->>Client: Error response
    else Command is safe
        Validator->>Executor: Execute command
        Executor->>Shell: Run shell command
        Shell->>Executor: Command output
        Executor->>Server: Process results
        Server->>Client: JSON-RPC Response
    end
    
    Client->>Server: GET /context
    Server->>Client: Markdown documentation

🚀 Installation

Prerequisites

• Docker and Docker Compose
• Git (for cloning the repository)

Using Docker (Recommended)

1. Clone the repository:

   git clone https://github.com/yourusername/mcp_command_server.git
   cd mcp_command_server
   

2. Start the server using Docker Compose:

   docker-compose up -d
   

3. The server will be available at http://localhost:3030

Building from Source

1. Ensure you have Rust installed (1.74+ recommended):

   curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
   

2. Clone and build the project:

   git clone https://github.com/yourusername/mcp_command_server.git
   cd mcp_command_server
   cargo build --release
   

3. Run the server:

   ./target/release/mcp_command_server
   

🧰 Usage

Basic Commands

Execute a simple command:

curl -X POST -H "Content-Type: application/json" -d '{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "command/get",
  "params": {
    "command": "echo \"Hello World\""
  }
}' http://localhost:3030/

Response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "stdout": "Hello World\n"
  }
}

Access API Documentation

Get the API documentation in markdown format:

curl http://localhost:3030/context

📚 API Documentation

The MCP Command Server provides comprehensive documentation via the /context endpoint. This documentation is served as markdown and includes:

• API overview
• Available methods
• Request/response formats
• Error codes
• Usage examples
• Security considerations

JSON-RPC Specification

The API follows the JSON-RPC 2.0 specification:

• Endpoint: http://localhost:3030/
• Method: POST
• Content-Type: application/json
• Body Format:

{
  "jsonrpc": "2.0",
  "id": "<unique_id>",
  "method": "command/get",
  "params": {
    "command": "<shell_command>"
  }
}

Available Methods

Response Format

Success Response:

{
  "jsonrpc": "2.0",
  "id": "<request_id>",
  "result": {
    "stdout": "<command_output>"
  }
}

Error Response:

{
  "jsonrpc": "2.0",
  "id": "<request_id>",
  "error": {
    "code": "<error_code>",
    "message": "<error_message>"
  }
}

Error Codes

🔒 Security

The MCP Command Server implements several security measures:

Command Exclusion System

The server uses a pattern-based exclusion system to prevent potentially harmful commands from being executed. This is configured through the exclude.yaml file, which contains:

• Plain text patterns (e.g., rm -rf, sudo, apt)
• Regular expression patterns (e.g., regex:.*\.\.\/.*)
• Options for case sensitivity and matching behavior

flowchart LR
    Command[Command Input] --> Validator[Command Validator]
    ExcludeYAML[exclude.yaml] --> Validator
    
    Validator --> Check{Safe?}
    Check -->|Yes| Execute[Execute Command]
    Check -->|No| Reject[Reject with Error]
    
    subgraph Patterns
        Plain[Plain Text Patterns]
        Regex[Regular Expression Patterns]
    end
    
    ExcludeYAML --> Patterns

Blocked Command Categories

The command exclusion system blocks several categories of potentially harmful commands:

• System modification (apt, yum, etc.)
• File deletion/modification (rm -rf, etc.)
• System control (shutdown, reboot, etc.)
• User/permission changes (chmod, sudo, etc.)
• Network operations (wget, curl, etc.)
• Command chaining to bypass filters (&&, |, etc.)
• Script execution (bash, python, etc.)
• Filesystem traversal (../, etc.)

Docker Security

The server runs as a non-root user within the Docker container to limit potential damage from security breaches.

💻 Development

Project Structure

mcp_command_server/
├── .context                 # API documentation markdown
├── Cargo.toml               # Rust dependencies
├── Dockerfile               # Multi-stage Docker build
├── exclude.yaml             # Command exclusion patterns
├── docker-compose.yml       # Docker Compose configuration
├── src/
│   ├── main.rs              # Main server code
│   ├── command.rs           # Command execution logic
│   ├── rpc.rs               # JSON-RPC handling
│   └── validator.rs         # Command validation logic
└── docs/
    ├── README.md            # Documentation for the Postman collection
    └── mcp_command_server.postman_collection.json  # Postman collection

Dependencies

• Rust: Primary programming language
• tokio: Async runtime for Rust
• warp: Web server framework
• serde & serde_json: Serialization/deserialization
• serde_yaml: YAML parsing for exclusion patterns
• regex: Regular expression support for command validation

🧪 Testing

Using the Postman Collection

A comprehensive Postman collection is included in the docs/ directory for testing the API:

1. Import docs/mcp_command_server.postman_collection.json into Postman
2. Run individual requests or the entire collection
3. The collection includes tests for:
   • Basic commands
   • Error handling
   • Command execution
   • File operations
   • Security validation

Manual Testing

Test basic functionality with curl:

# Test the context endpoint
curl http://localhost:3030/context

# Execute a simple command
curl -X POST -H "Content-Type: application/json" -d '{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "command/get",
  "params": {
    "command": "echo \"Hello World\""
  }
}' http://localhost:3030/

👥 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

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

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

Built with ❤️ using Rust and Docker.