Tech News
← Back to articles

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

read original related products more articles

πŸ“§ SMTP Tunnel Proxy

A high-speed covert tunnel that disguises TCP traffic as SMTP email communication to bypass Deep Packet Inspection (DPI) firewalls.

β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”‚ Application │─────▢│ Client │─────▢│ Server │─────▢│ Internet β”‚ β”‚ (Browser) β”‚ TCP β”‚ SOCKS5:1080 β”‚ SMTP β”‚ Port 587 β”‚ TCP β”‚ β”‚ β”‚ │◀─────│ │◀─────│ │◀─────│ β”‚ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜ β”‚ β”‚ β”‚ Looks like β”‚ β”‚ Email Traffic β”‚ β–Ό β–Ό β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β” β”‚ DPI Firewall β”‚ β”‚ βœ… Sees: Normal SMTP Session β”‚ β”‚ ❌ Cannot see: Tunnel Data β”‚ β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

🎯 Features

Feature Description πŸ”’ 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 πŸ‘₯ Multi-User Per-user secrets, IP whitelists, and logging settings πŸ”‘ Authentication Per-user pre-shared keys with HMAC-SHA256 🌐 SOCKS5 Proxy Standard proxy interface - works with any application πŸ“‘ Multiplexing Multiple connections over single tunnel πŸ›‘οΈ IP Whitelist Per-user access control by IP address/CIDR πŸ“¦ Easy Install One-liner server installation with systemd service 🎁 Client Packages Auto-generated ZIP files for each user πŸ”„ Auto-Reconnect Client automatically reconnects on connection loss

πŸ“š For in-depth technical details, protocol specifications, and security analysis, see TECHNICAL.md.

⚑ Quick Start

πŸ“‹ 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+

... continue reading