Vulnerable File Reader MCP Server: Command Injection Exploit Demonstration

Overview: What is Vulnerable File Reader MCP Server?

The Vulnerable File Reader MCP Server is an implementation intended to read files through a secure interface, but unfortunately, it contains a critical vulnerability in its design. This server was developed for educational purposes to highlight the dangers of improper input handling and shell command usage within Python scripts. It serves as a demonstration of how seemingly harmless software can lead to severe security breaches if not designed with proper input validation and sanitization techniques.

🔧 Core Features & MCP Capabilities

The core feature of this server is its ease of integration into various AI-driven applications through the Model Context Protocol (MCP). MCP servers facilitate seamless communication between AI desktop clients like Claude Desktop, Continue, and Cursor. By leveraging the Vulnerable File Reader MCP Server, these tools can communicate with backend systems to perform file operations securely.

The key capabilities of this server include:

1. File Reading: The server provides a method to read files from a specified directory.
2. Command Injection Vulnerability: A major flaw in the implementation allows for arbitrary command execution if user input is not properly sanitized.
3. Educational Tool: Ideal for showing developers the severity and importance of secure coding practices.

⚙️ MCP Architecture & Protocol Implementation

The architecture of the Vulnerable File Reader MCP Server revolves around the MCP protocol, which uses a server-client model for bidirectional communication between AI desktop clients and backend systems. The protocol involves:

• Data Flow: Data flows from the client to the server via standardized messages.
• Command Execution: Commands are executed on the server side based on client requests.

Protocol Flow Diagram

graph TD
    A[AI Application] -->|MCP Client| B[MCP Protocol]
    B --> C[MCP Server]
    C --> D[Data Source/Tool]
    style A fill:#e1f5fe
    style C fill:#f3e5f5
    style D fill:#e8f5e8

Client Compatibility Matrix

MCP Client	Resources	Tools	Prompts	Status
Claude Desktop	✅	✅	✅	Full Support
Continue	✅	✅	✅	Full Support
Cursor	❌	✅	❌	Tools Only

🚀 Getting Started with Installation

To set up and use the Vulnerable File Reader MCP Server, follow these steps:

1. Prerequisites: Ensure you have Python 3.12 or higher installed.

2. Clone Repository: Clone the repository from GitHub.

   git clone https://github.com/Eliran79/Vulnerable-file-reader-server.git
   cd Vulnerable-file-reader-server
   

3. Install MCP Server:

   mcp install main.py
   

4. Configure MCP Client: Edit the ~/.config/claude-desktop/claude_desktop_config.json file to include your server configuration.

   {
     "mcpServers": {
       "file-reader": {
         "command": "/ABSOLUTE/PATH/TO/uv",
         "args": [
           "--directory",
           "/data/git/file_reader_server",
           "/usr/bin/uv",
           "run,--with,mcp,mcp,run,main.py"
         ]
       }
     }
   }
   

5. Start MCP Server:

   mcp dev main.py
   

💡 Key Use Cases in AI Workflows

This server is particularly useful for demonstrating and mitigating risks associated with improper input handling in MCP implementations. By exploring the vulnerabilities, developers can learn about secure coding practices.

Real-World Example 1: Data Retrieval

In an AI workflow, this server could be used to retrieve configuration files required by an AI model before deployment:

1. Client Request: The client initializes a request to read a specific configuration file.
2. Server Response: The server fetches the file from the designated directory and returns it to the client.
3. Tool Integration: The tool integrates the fetched file into its settings, ensuring the AI environment is properly configured.

Real-World Example 2: Command Execution

Using this server's command injection vulnerability as a teaching tool:

1. Client Request: The client sends an exploit payload with shell=True enabled.
2. Server Compromise: The server executes arbitrary commands, demonstrating how such vulnerabilities can be exploited.
3. Mitigation Techniques: This use case highlights the importance of input validation and secure coding practices.

🔌 Integration with MCP Clients

The Vulnerable File Reader MCP Server ensures compatibility with multiple client tools, making it versatile for various AI applications:

• Claude Desktop: Supports file reading from command line.
• Continue: Extends tooling capabilities through file operations.
• Cursor: Integrates advanced features like enhanced file handling.

By incorporating this server into the ecosystem, developers can test and enhance their understanding of secure MCP implementation best practices.

📊 Performance & Compatibility Matrix

While the performance metrics are not explicitly provided in the README, it’s important to note that:

• Response Time: The time taken for command execution or file reading.
• Resource Utilization: CPU and memory usage during interactions with the server.

The compatibility matrix is already illustrated above, detailing support for various MCP clients.

🛠️ Advanced Configuration & Security

To enhance security in the Vulnerable File Reader MCP Server:

1. Input Sanitization: Avoid using shell=True by utilizing safe methods like shell-escaping.
2. Path Validation: Ensure that user-provided paths do not lead to traversal attacks.

Here's an example of a secure implementation:

import os

safe_dir = "/data/git/file_reader_server"  # Define the safe directory
file_name = file_name.strip()             # Sanitize input

# Path validation
safe_path = os.path.abspath(safe_dir)
path_resolved = os.path.abspath(file_name)

if not path_resolved.startswith(safe_path):
    raise ValueError("Path traversal attempt detected")

result = subprocess.check_output(["cat", file_name], shell=False)  # Secure command execution

❓ Frequently Asked Questions (FAQ)

1. Can I use this for production environments?

   • No, this server is intended for educational purposes only and should never be deployed in a real-world scenario without thorough testing and improvement.

2. Is there any official documentation or support for the MCP protocol?

   • Check the official Model Context Protocol (MCP) documentation for comprehensive guides and support details.

3. How can I ensure secure communication between clients and servers using MCP?

   • Implement proper security measures such as input validation, secure protocols, and regular updates to your server code.

4. Which AI tools are compatible with the current version of this server?

   • Refer to the client compatibility matrix in the documentation for a detailed list.

5. Where can I find more resources on Model Context Protocol (MCP) integration and security best practices?

   • Visit the official MCP website or community forums for extensive resources and discussions.

👨‍💻 Development & Contribution Guidelines

Developers are encouraged to modify and enhance this project to create a secure and reliable MCP server. Contributions include:

1. Improving Security: Implement additional safeguards to prevent command injection attacks.
2. Enhancing Features: Add new functionalities or improve existing ones based on user feedback.

🌐 MCP Ecosystem & Resources

For more information about the broader MCP ecosystem, refer to these resources:

• Model Context Protocol (MCP) Website: Discover official documentation and community forums.
• GitHub Issues/Repository: Contribute and track bugs in the open-source project.

By participating actively, developers can drive progress within the MCP community.

In summary, the Vulnerable File Reader MCP Server serves as an essential tool for educating developers about the importance of secure coding practices. By understanding its vulnerabilities, you can ensure your own applications are more robust and secure against similar exploits.