Show HN: SMTP Tunnel – A SOCKS5 proxy disguised as email traffic to bypass DPI

Summary

📧 SMTP Tunnel Proxy A high-speed covert tunnel that disguises TCP traffic as SMTP email communication to bypass Deep Packet Inspection (DPI) firewalls. ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ ┌──────────────┐ │ Application │─────▶│ Client │─────▶│ Server │─────▶│ Internet │ │ (Browser) │ TCP │ SOCKS5:1080 │ SMTP │ Port 587 │ TCP │ │ │ │◀─────│ │◀─────│ │◀─────│ │ └─────────────┘ └─────────────┘ └─────────────┘ └──────────────┘ │ │ │ Looks like │ │ Email Traffic │ ▼ ▼ ┌────────────────────────────────┐ │ DPI Firewall │ │ ✅ Sees: Normal SMTP Session │ │ ❌ Cannot see: Tunnel Data │ └────────────────────────────────┘ 🎯 Features Feature Description 🔒 TLS Encryption All traffic encrypted with TLS 1.2+ after STARTTLS 🎭 DPI Evasion Initial handshake mimics real SMTP servers (Postfix) ⚡ High Speed Binary streaming protocol after handshake - minimal overhead 👥 Multi-User Per-user secrets, IP whitelists, and logging settings 🔑 Authentication Per-user pre-shared keys with HMAC-SHA256 🌐 SOCKS5 Proxy Standard proxy interface - works with any application 📡 Multiplexing Multiple connections over single tunnel 🛡️ IP Whitelist Per-user access control by IP address/CIDR 📦 Easy Install One-liner server installation with systemd service 🎁 Client Packages Auto-generated ZIP files for each user 🔄 Auto-Reconnect Client automatically reconnects on connection loss 📚 For in-depth technical details, protocol specifications, and security analysis, see TECHNICAL.md. ⚡ Quick Start 📋 Prerequisites Server : Linux VPS with Python 3.8+, port 587 open : Linux VPS with Python 3.8+, port 587 open Client : Windows/macOS/Linux with Python 3.8+ : Windows/macOS/Linux with Python 3.8+ Domain name: Required for TLS certificate verification (free options: DuckDNS, No-IP, FreeDNS) 🚀 Server Setup (VPS) Step 1️⃣: Get a Domain Name Get a free domain pointing to your VPS: 🦆 DuckDNS - Recommended, simple and free - Recommended, simple and free 🌐 No-IP - Free tier available - Free tier available 🆓 FreeDNS - M...