gotun

gotun

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Lightweight HTTP-over-SSH proxy written in Go, designed to be cross-platform and easy to deploy.

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Overview

gotun is a command-line HTTP-over-SSH proxy. It establishes an SSH connection to a remote host and uses that host as the egress point for HTTP(S) traffic. Local HTTP requests are forwarded through the SSH tunnel and executed from the remote host.

Typical use cases:

• Accessing routers, servers, APIs and other resources in a private network
• Reaching networks that are only visible from a specific host (bastion/jump host, corporate network, isolated segments, etc.)
• Using the remote host as an outbound HTTP proxy

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How it works

Before: no direct access to internal resources

Your machine                 Firewall/NAT                    Internal network
┌─────────┐                ┌─────────┐                     ┌─────────────┐
│         │   ❌ direct     │         │                     │  Router     │
│   PC    │ ─────────────▶ │  FW/NAT │                     │  NAS        │
│         │   blocked       │         │                     │  Servers    │
└─────────┘                └─────────┘                     └─────────────┘

After: access via SSH bastion with gotun

Your machine            SSH (tcp/22)                   Bastion                 Internal network
┌─────────┐          ┌─────────────┐                ┌─────────┐              ┌─────────────┐
│         │  HTTP    │  gotun HTTP │    SSH tunnel  │         │   internal   │  Router     │
│   PC    │ ◀──────▶ │   proxy     │◀──────────────▶│ Bastion │◀────────────▶│  NAS        │
│         │          └─────────────┘                │         │              │  Servers    │
└─────────┘                                         └─────────┘              └─────────────┘
   ↑
   └─ HTTP proxy set to 127.0.0.1:8080

Why use gotun?

Traditional approach	With gotun
Manual port forwards per service	One SSH tunnel for all HTTP(S) traffic
Multiple ports exposed on the bastion	No extra open ports; uses existing SSH only
Hard to manage multiple mappings	Single proxy endpoint
Easy to accidentally expose internal hosts	All traffic stays inside an encrypted SSH tunnel

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Features

• No additional software required on the remote host (only SSH)
• All traffic is carried over an SSH tunnel
• Can reach any address that the remote host can reach (including internal addresses)
• Supports single and multi-hop SSH jump hosts
• Cross-platform: Windows, Linux, macOS
• Can be used as a system HTTP proxy (optional)
• TUN Mode: Supports standard TCP-based application proxying
• Rule-based traffic splitting via configuration file
• Shell completion support for Bash, Zsh, Fish, PowerShell
• Structured logging and verbose mode for debugging
• SOCKS5 proxy support

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Installation

Install script

curl -fsSL https://raw.githubusercontent.com/Sesame2/gotun/main/scripts/install.sh | sh

The script installs gotun into ~/.local/bin or /usr/local/bin.
Make sure that directory is included in your PATH.

Homebrew (macOS / Linux)

brew install gotun

Download prebuilt binaries

Download the appropriate binary for your platform from the
Releases page.

Build from source

git clone https://github.com/Sesame2/gotun.git
cd gotun
make build

The binary will be placed under build/.

go install

With Go 1.17+:

go install github.com/Sesame2/gotun/cmd/gotun@latest

Note: when installing via go install, the --version output may not include an exact version number, as it depends on build-time metadata. For reproducible version information, prefer the install script, Homebrew, or release binaries.

Ensure $GOBIN or $GOPATH/bin is on your PATH.

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Quick start

Basic usage

# Basic: connect to an SSH server and start an HTTP proxy
gotun [email protected]

# Use a non-default SSH port
gotun -p 2222 [email protected]

# Use a specific private key
gotun -i ~/.ssh/id_rsa [email protected]

# Change local proxy listen address/port
gotun --listen :8888 [email protected]

# Disable automatic system proxy configuration
gotun --sys-proxy=false [email protected]

# Enable SOCKS5 proxy (default listen on :1080)
gotun --socks5 :1080 [email protected]

Note: When using SOCKS5 with custom routing rules, it is recommended to enable "Proxy DNS when using SOCKS5" (Remote DNS) in your client. Otherwise, the client might resolve domains to IPs locally, causing domain-based routing rules to fail.

Browser configuration

By default, gotun listens on 127.0.0.1:8080 (unless changed by --listen).

In your browser’s proxy settings:

• HTTP proxy host: 127.0.0.1
• HTTP proxy port: 8080 (or the port you configured)

If system proxy support is enabled, some platforms can be configured automatically.

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Command-line options

Flag	Short	Description	Default
--http		Local HTTP proxy listen address (alias for --listen)	:8080
--listen	-l	[Deprecated] Same as --http	:8080
--socks5		SOCKS5 proxy listen address	:1080
--port	-p	SSH server port	22
--pass		SSH password (insecure, interactive preferred)
--identity_file	-i	Private key file path
--jump	-J	Comma-separated jump hosts (user@host:port)
--http-upstream		Force forward all HTTP requests to this upstream (host:port)
--target		[Deprecated] Same as --http-upstream
--timeout		Connection timeout	10s
--verbose	-v	Enable verbose logging	false
--log		Log file path	stdout
--sys-proxy		Auto-configure system proxy	true
--rules		Path to routing rules config file

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Typical scenarios

1. Accessing internal services through a bastion

Assume jumpserver.company.com can reach 192.168.1.100 inside a private network:

gotun [email protected]

Once running and proxy is configured, you can browse:

• http://192.168.1.100:8080
• Other HTTP(S) endpoints reachable from the jumpserver

2. Development and debugging

You need to reach a remote dev environment (APIs, DB, etc.) from your local machine:

# Verbose logging and custom listen port
gotun --listen :8888 -v [email protected]

If you do not want gotun to modify system proxy settings:

gotun --sys-proxy=false --listen :8888 -v [email protected]

Then configure your IDE or tooling to use 127.0.0.1:8888 as HTTP proxy.

3. Using a remote host as internet egress

gotun [email protected]

All (or selected) HTTP(S) traffic will exit from the remote server’s network.

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Jump hosts

When the final target is only reachable via one or more intermediate hosts, you can configure jump hosts.

Workflow diagram

Your machine           SSH Tunnel            Jump Host             SSH Tunnel            Target Host
┌─────────┐         ┌───────────┐         ┌──────────┐         ┌───────────┐         ┌──────────┐
│         │   🔐    │           │    🔐   │          │    🔐   │           │   🌐   │          │
│   PC    │◀───────▶│ gotun tun │◀───────▶│ Bastion  │◀───────▶│ gotun tun │◀───────▶│  Target  │
│         │  HTTP   │ (encrypt) │         │          │         │ (encrypt) │        │          │
└─────────┘         └───────────┘         └──────────┘         └───────────┘         └──────────┘

Single jump host

gotun -J [email protected] [email protected]

Traffic flow:

PC → SSH to jump.host.com → SSH to target.server.com → HTTP request

Multiple jump hosts

gotun -J [email protected],[email protected] [email protected]

gotun will establish nested SSH tunnels through each hop in order.

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Authentication

SSH key authentication (recommended)

# Explicit key
gotun -i ~/.ssh/id_rsa [email protected]

# Rely on default keys in ~/.ssh
gotun [email protected]

Password authentication

# Interactive (recommended over CLI flags)
gotun [email protected]
# gotun will prompt for the password

# Non-interactive (not recommended)
gotun --pass 'yourpassword' [email protected]

Avoid passing passwords directly on the command line when possible.

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System proxy integration

By default (--sys-proxy=true), gotun attempts to:

1. Capture the current system proxy settings
2. Set the system HTTP proxy to its local listening address (e.g. 127.0.0.1:8080)
3. Restore the original settings on exit

If you prefer to manage proxy settings yourself, run:

gotun --sys-proxy=false [email protected]

Platform notes:

• macOS: uses networksetup
• Windows: uses registry-based proxy configuration
• Linux: attempts to use desktop settings (e.g. GNOME) and/or environment variables where applicable

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Rule-based routing (Advanced)

gotun can read a Clash-style YAML rules file to decide which traffic is sent via the SSH proxy and which goes directly.

This is useful when you need:

• Direct access to local or corporate networks
• Proxy only for selected destinations (e.g. external services)

Example rules file

rules.yaml:

mode: rule

rules:
  # Direct access for internal domains and networks
  - DOMAIN-SUFFIX,internal.company.com,DIRECT
  - IP-CIDR,10.0.0.0/8,DIRECT
  - IP-CIDR,192.168.0.0/16,DIRECT
  - DOMAIN-SUFFIX,cn,DIRECT
  - DOMAIN-SUFFIX,qq.com,DIRECT

  # Specific domains via proxy
  - DOMAIN-SUFFIX,google.com,PROXY
  - DOMAIN-SUFFIX,github.com,PROXY

  # Everything else via proxy
  - MATCH,PROXY

Start gotun with the rules file:

gotun --rules ./rules.yaml user@your_ssh_server.com

Requests will be matched from top to bottom; the first matching rule applies.

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TUN Mode (Advanced)

gotun creates a local virtual network interface that intercepts specific (or all) TCP traffic and transparently tunnels it via SSH. This allows applications that don't support proxy settings to access remote resources through the SSH tunnel.

Why use TUN Mode?

• Full Application Proxy: Perfectly supports RDP (Remote Desktop), Database connections (MySQL/PostgreSQL), Redis, and other TCP-based application protocols.
• Zero Config: In Global Mode, all TCP traffic is routed automatically without per-app configuration.
• Network Mapping: Map a remote internal subnet to your local machine, solving IP conflict issues between local and remote networks.

⚠️ Note: Current TUN Mode only supports TCP protocol. UDP traffic and ICMP (ping) are not supported (use telnet or nc -vz to test connectivity).

Core Parameters

Flag	Short	Description
--tun		Explicitly enable TUN mode (auto-enabled by other TUN flags, optional)
--tun-global	-g	Global Mode: Routes ALL network traffic (auto-handles gateway to prevent SSH drop)
--tun-route		Split Tunneling: Route specific CIDRs to TUN (can be repeated)
--tun-nat		NAT Mapping: Map local subnet to remote subnet (LocalCIDR:RemoteCIDR)
--tun-ip		Internal IP for the TUN interface (default 10.0.0.1/24)

Usage Examples

1. Global Mode

Route all local traffic through the remote server.

⚠️ Warning: Global TUN mode might conflict with other software that modifies routing tables (e.g., Clash, ZeroTier). Use with caution or prefer Split Tunneling.

# -g automatically enables TUN mode
sudo gotun -g [email protected]

2. Split Tunneling

Route only specific subnets through the tunnel. For example, only traffic to 10.0.0.0/24 goes via SSH:

# Traffic to 10.0.0.x goes via SSH, everything else is direct
sudo gotun --tun-route 10.0.0.0/24 [email protected]

3. NAT Mapping

Solve subnet conflicts. For example, remote target is 192.168.0.0/24, but your local network also uses this range. Map it to a conflict-free local range (e.g., 10.0.0.0/24).

# Access Local 10.0.0.1 -> Auto-NAT -> Remote 192.168.0.1
sudo gotun --tun-nat 10.0.0.0/24:192.168.0.0/24 [email protected]

Note:

• Privileges: TUN mode requires sudo (macOS/Linux) or Admin (Windows).
• Windows: wintun.dll is auto-extracted on first run; no manual driver installation needed.

4. RDP Remote Desktop Example

Scenario: You need to RDP into a Windows machine at 192.168.2.1 (behind the SSH server), but you can't reach that IP directly. The SSH server (192.168.2.2) can reach it.

# Route traffic for 192.168.2.0/24 through the SSH tunnel
sudo gotun --tun-route 192.168.2.0/24 [email protected]

Once started, open your Remote Desktop Client and connect to 192.168.2.1 directly. It will feel like you are on the same LAN.

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Troubleshooting

Connection issues

# Enable verbose logs
gotun -v [email protected]

# Log to a file
gotun -v --log ./gotun.log [email protected]

Check:

• SSH connectivity (ssh [email protected])
• Firewall or security groups
• Correct key/port/jump configuration

Permission issues (system proxy)

On some systems, changing system proxy settings requires elevated privileges:

# macOS / Linux
sudo gotun [email protected]

# Windows: run cmd/PowerShell as Administrator
gotun.exe [email protected]

If this is not acceptable, disable system proxy management and configure proxy settings manually:

gotun --sys-proxy=false [email protected]

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Status and roadmap

Implemented:

• HTTP proxy
• HTTPS tunneling via CONNECT
• SSH key-based authentication
• Interactive password authentication
• Optional automatic system proxy configuration
• Cross-platform support (Windows/Linux/macOS)
• Verbose logging and log file output
• CLI flags and subcommands
• Single and multi-hop jump host support
• Rule-based routing
• Shell completion for common shells
• SOCKS5 proxy support
• TUN Mode: L3 VPN support (Global/Split/NAT)

Planned:

• Tray/GUI frontend
• Export/import of configuration profiles
• Connection pooling and performance tuning
• Traffic statistics and basic monitoring

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License

This project is licensed under the MIT License.