Skillget

mcp-client-and-proxy

mcp
SUMMARY

A universal MCP client with proxying feature to interact with MCP Servers which support STDIO transport.

README.md

Appsecco MCP Client and Proxy

Semi Professional Security Tool with Cool Vibes - Send MCP Server Traffic to your Burp Suite

Appsecco
License
Python

🌟 Key Features

  • 🔍 Advanced MCP Server Integration - Connect to any MCP server with professional-grade reliability
  • 🌐 Enterprise Proxy Support - Seamless integration with Burp Suite and other security tools
  • 🔗 Proxychains Integration - Professional traffic routing and analysis capabilities
  • 🛡️ SSL Bypass Support - Advanced testing scenarios with certificate handling
  • 📊 Interactive Security Testing - Professional interface for security assessments
  • 🔭 Full Traffic Visibility - Intercept both local relay traffic AND backend MCP server HTTPS traffic in Burp

🚀 What This Tool Does

The Appsecco MCP Client and Proxy is a professional security testing tool that provides:

  1. Local Relaying Proxy - Start a local proxy server to route traffic through Burp Suite or other security tools
  2. MCP Server Integration - Connect to MCP servers defined in mcp_config.json and interact with their tools
  3. Professional Traffic Analysis - Route all traffic through configurable proxies for security testing
  4. Full Backend Visibility - Intercept HTTPS traffic from mcp-remote to remote MCP endpoints in Burp
  5. Enterprise-Grade Reliability - Built for professional security teams and penetration testers

🛠️ Installation & Setup

Prerequisites

  • Python 3.7+
  • Node.js 18+ and npm (for running npx-based MCP servers)
  • Proxychains (for advanced proxy routing)
  • Burp Suite (recommended for traffic analysis)

Quick Start

# 1. Create virtual environment
python3 -m venv venv && source venv/bin/activate

# 2. Install Python requirements
pip3 install -r requirements.txt

# 3. Install Node.js dependencies for backend traffic interception
npm install -g global-agent
npm install undici

# 4. Run the professional security testing tool
python3 app.py --start-proxy

Proxychains Installation

The tool will automatically detect if proxychains is installed and provide installation instructions if needed:

  • Ubuntu/Debian: sudo apt-get install proxychains
  • CentOS/RHEL: sudo yum install proxychains
  • macOS: brew install proxychains-ng

📖 Usage

Basic Usage

# Start with HTTP proxy server for Burp inspection
python3 app.py --start-proxy

# Use custom configuration file
python3 app.py --config my_mcp_config.json --start-proxy

# Disable Burp proxy routing
python3 app.py --no-burp

# Disable proxychains
python3 app.py --no-proxychains

Advanced Options

usage: python3 app.py [-h] [--config CONFIG] [--proxy PROXY] [--start-proxy]
              [--proxy-port PROXY_PORT] [--no-burp] [--no-proxychains]
              [--no-ssl-bypass] [--debug]

Appsecco MCP Client and Proxy - Professional Security Testing Tool with proxychains support

options:
  -h, --help            show this help message and exit
  --config CONFIG, -c CONFIG
                        MCP configuration file (default: mcp_config.json)
  --proxy PROXY, -p PROXY
                        Burp proxy URL (default: http://127.0.0.1:8080)
  --start-proxy         Start HTTP proxy server for Burp inspection
  --proxy-port PROXY_PORT
                        HTTP proxy server port (default: 3000)
  --no-burp             Disable Burp proxy routing
  --no-proxychains      Disable proxychains usage
  --no-ssl-bypass       Disable SSL certificate bypass
  --debug               Enable debug output for troubleshooting

Example: python3 app.py --start-proxy

Brought to you by Appsecco - Product Security Experts

🔄 Data Flow with --start-proxy

When using the --start-proxy flag, the tool creates a professional security testing environment:

1. 🚀 Run the app: python3 app.py --start-proxy
2. 🔧 MCP Server Starts (with proxychains and HTTP_PROXY set)
3. 🌐 Local Proxy Server Starts on port 3000
4. 📡 App sends requests -> Local Proxy (port 3000) -> Burp (port 8080) -> MCP Server (stdio)
5. 🔗 MCP server (mcp-remote) sends HTTPS requests -> Burp (port 8080) -> Remote MCP endpoint
6. 📤 Remote MCP endpoint responds -> Burp -> MCP Server -> Local Proxy -> App

Burp Suite Configuration

  1. Launch Burp Suite and set it to listen on port 8080 (localhost)
  2. Configure Burp to intercept traffic as usual. This traffic will be travelling to localhost:3000 and backend APIs
  3. Use Burp's professional tools like Repeater, Intruder, and Scanner

🔭 Intercepting Backend MCP Server Traffic (mcp-remote)

By default, proxychains does not reliably intercept Node.js traffic because Node.js uses its own networking stack (libuv/undici) that bypasses LD_PRELOAD/DYLD_INSERT_LIBRARIES hooks. This means traffic from mcp-remote to remote endpoints like https://your-mcp-server.example.com/mcp would not appear in Burp.

This tool solves this using two mechanisms:

  • HTTP_PROXY/HTTPS_PROXY env vars — set automatically on the MCP subprocess when Burp proxy is enabled, so npm and legacy http traffic routes through Burp
  • proxy-bootstrap.js — a startup script that patches both Node.js's legacy http/https modules (via global-agent) and the native fetch/undici dispatcher (via undici's ProxyAgent), covering all outbound HTTP(S) connections from mcp-remote

Setup Steps

Step 1: Install the required Node.js packages

npm install -g global-agent
npm install undici        # run from the project directory

Step 2: Find your global-agent install path

npm root -g
# e.g. /usr/local/lib/node_modules  or  /Users/you/.nvm/versions/node/vX.Y.Z/lib/node_modules

Step 3: Export Burp's CA certificate as PEM

In Burp Suite: Proxy → Options → Import/export CA certificate → Export Certificate in DER format

Then convert to PEM:

openssl x509 -inform DER -in burp-ca.crt -out burp-ca.pem

Step 4: Update proxy-bootstrap.js with your global-agent path

Edit the require(...) path in proxy-bootstrap.js to match your system:

const { bootstrap } = require('/path/to/node_modules/global-agent');
bootstrap();

const { ProxyAgent, setGlobalDispatcher } = require('undici');
const proxyUrl = process.env.GLOBAL_AGENT_HTTPS_PROXY || 'http://127.0.0.1:8080';
setGlobalDispatcher(new ProxyAgent(proxyUrl));

Step 5: Configure mcp_config.json

Add an env block to each MCP server entry:

{
  "mcpServers": {
    "My MCP Server": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",
        "https://your-mcp-server.example.com/mcp"
      ],
      "env": {
        "NODE_EXTRA_CA_CERTS": "/path/to/burp-ca.pem",
        "NODE_OPTIONS": "--require /path/to/mcp-client-and-proxy/proxy-bootstrap.js",
        "GLOBAL_AGENT_HTTP_PROXY": "http://127.0.0.1:8080",
        "GLOBAL_AGENT_HTTPS_PROXY": "http://127.0.0.1:8080"
      }
    }
  }
}
Field Purpose
NODE_EXTRA_CA_CERTS Trusts Burp's CA cert so TLS validation passes through the proxy
NODE_OPTIONS Loads proxy-bootstrap.js before any other code runs
GLOBAL_AGENT_HTTP_PROXY / GLOBAL_AGENT_HTTPS_PROXY Proxy URL picked up by both global-agent and proxy-bootstrap.js

Once configured, all traffic — including HTTPS requests from mcp-remote to remote MCP endpoints — will appear in Burp.

📊 Analytics

This tool includes anonymous usage analytics for Appsecco to obtain usage metrics

What we track: startup arguments, tool start and end, count of MCP servers, error rates and basic system info (OS, Python version)
What we DON'T track: Personal data, URLs, testing targets, traffic, credentials
Opt-out: Use --no-analytics flag or set MCP_ANALYTICS_DISABLED=true

You can use export MCP_ANALYTICS_DEBUG=true to see what analytics data is shared.

Why did we build this universal MCP client

Watch the video

🛡️ About Appsecco - Let Us Hack Your Product Like Attackers Do 🛡️

Appsecco is a leading cybersecurity company specializing in product security testing, penetration testing, and security assessments. At Appsecco we hack your product and Cloud/K8s infra like hackers do. Real security testing for business-critical applications.

We wrote this MCP Client and Proxy tool when we had to testing the security of MCP server of a Fortune 500 FinTech company. It worked well for our Burp Suite workflow. We felt that there could be others who may need this as well.

🏢 Product Security Testing

Appsecco provides comprehensive cybersecurity services:

  • 🔍 Penetration Testing & Security Assessments for Business-critical Products
  • 🛡️ Application Security Testing
  • 🏗️ Infrastructure Security Audits
  • ☁️ Cloud Security Assessments

📞 Contact & Support

While this tool is offered under an open source MIT license, if you are interested in taking a look at our services. Here are the details.

📄 License

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

🙏 Acknowledgments

Built with ❤️ by Riyaz & Akash for the cybersecurity community.

Appsecco - Let Us Hack Your Product Like Attackers Do 🛡️

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